EP3268531A1

EP3268531A1 - Method for determining a level of hygiene of a washing machine with an impedance sensor and washing machine suitable tehrefor

Info

Publication number: EP3268531A1
Application number: EP16709448.1A
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: 2016-03-11
Publication date: 2018-01-17
Anticipated expiration: 2036-03-11
Also published as: CN107407031A; CN107407031B; EP3268531B1; WO2016146521A1; DE102015204692A1

Abstract

The invention relates to a method for determining a level of hygiene H of a washing machine (1), comprising a lye container (2), a drum (3) for receiving the items of laundry (4), a drive motor (5) for the drum (3), and a control device (8) for controlling at least one washing process, wherein an impedance sensor (9, 10) which is arranged in the washing machine (1) and comes into contact with an aqueous fluid (7) in the course of a washing process, measures an impedance signal, said impedance signal being evaluated with regard to deposits on the impedance sensor (9, 10) as a measure for the level of hygiene H of the washing machine (1). The invention also relates to a washing machine (1) suitable for carrying out the method.

Description

Method for determining a degree of hygiene of a washing machine with an impedance sensor and suitable washing machine for this purpose

The invention relates to a method for determining a degree of hygiene of a washing machine with an impedance sensor (also referred to as electrochemical impedance sensor) and a washing machine suitable for this purpose. More particularly, the invention relates to a method for determining a degree of hygiene H of a washing machine with a tub, a drum for receiving laundry, a drive motor for the drum, and a control device, and a suitable for performing 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, in particular, surfactants as surface-active substances in order to form a wash liquor for the purpose of cleaning laundry items. In a washing machine, even when used correctly, residues from the water, from the laundry items treated or from detergents can accumulate. These residues can form a biofilm in the household appliance, which may be difficult to remove. The user of the washing machine usually gets something of it, if the biofilm secretes unpleasant-smelling substances. At this time, however, a distinct biofilm has already formed. In addition, the smell can be very unpleasant.

In any case, over time, the state of appearance of washing machines deteriorates due to the formation of deposits or deposits such as deposits. Biofilms. Biofilms contain immobilized bacterial cells embedded in a polymer matrix of microbial origin and, in addition to microorganism cells, may contain abiotic or inorganic components in greater amounts, all being held together by mucus formed by bacteria.

The risk of biofilm formation is compounded by a trend towards washing laundry at low temperature. The improvement of detergents and washing machines allows a good removal of soiling from textiles even at low temperatures. In addition, the washing is done at low temperatures increasingly dictated by the textile industry, since many laundry items should be washed according to their washing instructions only at 30 ° C or 40 ° C. In addition, low temperature washing saves energy and protects the environment. For many consumers, however, the question arises as to whether a sufficiently high degree of hygiene is achieved during a washing process at low temperatures. Microbial germs, in contrast to soils, are generally invisible and can threaten health. If a washing machine is operated mainly in the low temperature range and with mild detergents, contamination and formation of a biofilm in the washing machine can occur. In addition, during a washing process, cross-contamination may take place if heavily contaminated laundry items are washed together with slightly contaminated items of laundry in the same washing operation, after which the germ content of the previously slightly contaminated items of laundry has risen. Although many microbial germs found in household linen are not pathogenic to humans, special care should be taken in the home, in the care of the elderly, babies and toddlers, and generally heavily contaminated items such as kitchen towels. In such cases, a higher level of hygiene appears appropriate. In order to achieve the highest possible degree of hygiene, various modifications to laundry treatment appliances have hitherto been known. Particularly in the industrial sector, for example in the cleaning of special workwear (such as surgical gowns), highly specialized washing processes up to sterilization are used. In laundries and nursing homes, there are also special "hygiene washing machines." In the household sector, special washing machines with programs with additional rinses are offered to meet the increasing demand for high standards of hygiene, for example in the case of allergic persons or in households with small children The hygienic state of a washing machine sometimes activates a special hygiene program in which, for example, using steam and / or bioactive added liquids or gases, cleaning of the relevant parts of the washing machine is carried out, but the hygiene programs are not optimal for hygienic needs of the Washing machines tuned because time, duration and intensity of the measures carried out in a hygiene program are not tailored to the actual state of hygiene in the washing machine. It would therefore be desirable to obtain qualitative and in particular quantitative information about the degree of hygiene of the washing machine and to restore a desired degree of hygiene of the washing machine.

EP 2 465 993 A1 and EP 2 465 993 A1 describe a laundry treatment appliance with a cycle for the treatment of biofilms and corresponding processes. For example, if overgrowth is detected using a refractive index sensor, turbidity, surface tension or capacitance in a non-accessible area of the device, potential consequences such as biofilm formation are addressed by performing a biofilm treatment cycle. For this purpose, the relevant device part is heated, for example, directly or by means of hot air. In addition, the use of biocidal compounds is discussed.

DE 10 201 1 007 170 A1 describes a method for detecting and displaying a degree of hygiene of laundry in a laundry treatment appliance, which has a container for receiving laundry to be treated, a control device which is designed to carry out a plurality of selectable laundry treatment programs, and a display device wherein a hygienic grade H _{res of} the laundry resulting from a selected laundry treatment program is determined taking into account a predetermined or determined initial hygiene level H _ori g and the selected laundry treatment program and a difference ΔΗ = (H _re s-Htar) ^ 0 between the resulting hygiene level H _{res of} the laundry and a predetermined degree of hygiene H _{tar of} the laundry on the display device is displayed as a signal S1.

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 feed due to the characterization of the surfactant content in the washing and / or rinsing water of washing machines. 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.

The DE 43 1 1 064 A1 describes a method for measuring the Schmutzbefrachtung a wash liquor, wherein from the electrical impedance of an AC voltage applied capacitor between the plates is the wash liquor, measured values (M _R , Mi) determined separately according to real part and imaginary part and the measured values are compared with predetermined limit values.

EP 1 441 056 A1 discloses a washing machine comprising a tank for loading a washing liquid and things to be washed and control means adapted to perform a predetermined washing program. The washing machine comprises at least a first electrode which is electrically isolated from the washing liquid and sensor means which are to be connected to the control means and the first electrode and adapted to be a value of a sensor passing through the first electrode and through the washing liquid second electrode is formed to determine. The value should be supplied to the control means to control and / or adjust a wash program. The value determined by the sensor should indicate a capacitance and / or a complex impedance of the two electrodes. EP 2 71 1 697 A2 discloses a method for detecting properties of fluid media within a predetermined process using impedance spectroscopy, wherein various steps for recording and evaluating impedance characteristics as well as certain characteristic points are described in detail. Differences between the respective characteristic points of the current detections of the impedance characteristics are determined and evaluated.

JP 2010-213889 A discloses a sensor for a cleaning liquid according to the summary. This is to solve the problem of providing a sensor which can precisely determine a resistance value of a cleaning liquid. For this purpose, a change in a parallel resonance impedance is detected and evaluated with regard to the resistance value of the cleaning fluid.

Against this background, the object of the invention was to provide an improved method for determining a degree of hygiene of a washing machine. Preferably, this level of hygiene should be able to be determined and displayed in a way that is advantageous for a user, wherein the user should preferably also be given a possibility for suitable remedial measures. 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 determining a degree of hygiene H of a washing machine with a tub, a drum for receiving laundry, a drive motor for the drum, and a control device for controlling at least one washing program, wherein with an arranged in the washing machine impedance sensor, the comes in contact with an aqueous liquid in the course of a washing program, an impedance signal is measured and the Impedance signal is evaluated in terms of deposits on the impedance sensor as a measure of the degree of hygiene H of the washing machine.

Herein, an "aqueous liquid" may mean water, a wash liquor or a rinsing liquid, Furthermore, the "aqueous liquid" may also be incorporated in a biofilm adhering to the impedance sensor.

For the evaluation of the impedance signal with regard to deposits on the impedance sensor as a measure of the hygiene level H of the washing machine, a relationship between the impedance signal and the type and / or amount of deposits on the impedance sensor stored in the control device is generally used.

The impedance sensor is preferably arranged in an induction bowl, the tub and / or on the drum. Particularly preferably, at least one impedance sensor is arranged in the rear region of the tub and / or the drum. Thus, the degree of hygiene is determined in particular at the one or more places where it is particularly easy to form a biofilm and are sometimes relatively difficult to access.

The deposition on the impedance sensor may consist of various components such as dirt and detergent residues as well as the components of a resulting or existing biofilm. For the present invention it is particularly preferred that the deposition on the impedance sensor is a biofilm.

In general, the impedance sensor in the washing machine can be in contact with air, as well as with water with salts (chlorides, hardness). In addition, deposits may be present on the impedance sensor, which may be present in the form of biofilm (again consisting of 85-90% of water with salts) and / or particles (deposits of water hardness, zeolites, dirt residues, etc.). Different degrees and types of deposits lead to different impedance signals. Wherein the currently measured impedance signal in turn depends on the current state of moisture of the washing machine, in particular in the range of an impedance sensor. The impedance sensor is unwetted and without deposits in air, then there is the highest possible electrical resistance, since air in this context represents an insulator and thus a high impedance. This condition is present as long as the impedance sensor is measured in a new or a little-used or carefully cleaned machine without water.

If the impedance sensor comes into contact with water, then there is an immediate drop in the electrical resistance or the impedance (the gradient of the waste is large).

If dry deposits (particles) are present on the impedance sensor, then an impedance signal similar to that in air results. If these pads are wet or there is a biofilm, the measured impedance is lower than that of an airborne impedance sensor (if the pads connect the electrodes of the sensor), but higher than a clean sensor wetted with water. If a biofilm has formed on the sensor in particular, the impedance lies between that of water and solid deposits.

In addition, the temporal gradient of the impedance depends on the type of lining. Thus it can be concluded from the temporal course of the impedance signal, on the type of deposition. In particular, whether it is a particle deposition or a biofilm.

In this case, the temporal course can be considered both in the short term, ie in the transition from dry state to wetted state when performing a washing process, as well as in the long term, so in the same wetting state across several washing processes, evaluated to a knowledge of the type of coating reach.

The temporal change of the gradient over the service life of the washing machine is different when building up a particle deposition as in biofilm structure and can therefore provide knowledge about the nature of the deposition and the state of the washing machine. It is also known that during the operation of the washing machine there is an increased buildup of particulate matter, ie particle deposition. On the other hand, biofilm buildup tends to occur during downtime. Thus, on the one hand, conclusions about the type of deposits present can be drawn from the type of impedance signal on the one hand and from records of the time course of the activity of the device, and used to assess the device status. Or the information about the temporal course of the activity of the device can be used to check the evaluation of the impedance signal with regard to the deposition.

According to the invention, a method is preferred in which an impedance signal of the impedance sensor is measured in the washing machine in the presence of water before carrying out a first laundry treatment, in particular a washing of laundry items, and stored in the control device as a reference measurement corresponding to a maximum hygiene level H _max becomes. For measurement, the water used for washing programs can be used. However, it is also possible to use standard solutions with different predefined conductance values in order to be able to take into account the conductance of an aqueous liquid used as a measure of the water hardness in the later measurements. Likewise, reference measurements for different temperatures can be made and stored in the controller.

The implementation of the method according to the invention should as far as possible not be disturbed by the presence of detergent or dirt. Preferably, therefore, the impedance signal is measured and evaluated with regard to deposits on the impedance sensor as a measure of a hygiene state H of the washing machine by a rinsing liquid from the last rinsing step of a rinsing phase or water is used as the aqueous liquid. In a particularly preferred embodiment of the method according to the invention, the impedance signal is evaluated with regard to the degree of hygiene H of the washing machine and remedial measures are taken upon reaching or falling below a minimum degree of hygiene H _min . A preferred remedy is that upon reaching or falling below a minimum level of hygiene H _min, a cleaning program is automatically carried out with a cleaning liquid having a predetermined high minimum temperature T _min i and / or contains cleaning additives with a cleaning force F-ι. The high minimum temperature T _min1 may be 50 ° C or more, for example. The term "cleaning power" means, for example, a concentration or an oxidizing ability of a cleaning additive and thus generally also stands for a biocidal effect of a cleaning additive If the cleaning additive is the same in two cleaning fluids, then different cleaning powers represent different concentrations of the cleaning additive.

For carrying out such a cleaning program, a storage container for such a cleaning liquid or for the cleaning additives may be present in a washing machine used for carrying out the method.

Suitable additives may e.g. surfactant-containing detergents, oxidizing agents, acids and alkalis. Preferably biocidal substances are used as additives, i. Biocides. According to the invention, the biocide is not limited, as long as it can be used in the washing machine. For example, it may be hypochlorite, which is produced by electrolysis of a saline solution, which may be present in a suitable storage container of the washing machine present in embodiments of the washing machine, or an oxidizing gas. The oxidizing gas may be generated, for example, in a plasma generator. For example, ozone can be used as a biocidal agent.

For the heating of the cleaning liquid, as which in the case of the use of a heated cleaning liquid in particular also water can be used, preferably in a washing machine generally anyway existing heater is used for the wash liquor.

After carrying out the cleaning program, an impedance signal is again recorded in the presence of water with regard to remaining deposition residues on the impedance sensor and evaluated to determine whether the hygiene state is above H _min . If this is not the case, a cleaning program is preferably carried out again automatically.

Preferably, a cleaning program is performed only if there are no laundry items in the drum.

According to the invention, when a hygiene condition H <H _{min is determined} after a cleaning program has been carried out, a cleaning program is carried out with a cleaning liquid having a predetermined high minimum temperature T _min2 T _min1 and / or cleaning additives with a cleaning force F ₂ Contains F- _\ . Very particularly preferred is T _min2 > T _min1 and / or F ₂ > Fi.

If the washing machine used in the method according to the invention has an acoustic and / or optical display device, it is preferable to indicate that the minimum level of hygiene H _{min has been} reached or fallen short of on the display device.

Moreover, it is inventively preferred that the cleaning program is performed while a stored in the control device movement program of the drum is performed. Preferably, the execution of a cleaning program is displayed on a display device, if any.

"Movement program of the drum" generally means a sequence of rotation and stoppage phases of the drum, in which case the rotation speed of the drum can be different during rotation phases of the drum It is rotated in one direction and then, if necessary after a short break, turned back in the other direction, this process can be repeated several times.Such a movement program, the detachment and removal of a deposit on the impedance sensor can be supported in that a cleaning fluid reaches as many places as possible to be cleaned in the washing machine.

The desired minimum level of hygiene H _min may vary depending on the composition of the members of a household, as these possibly have different requirements or requirements with regard to the degree of hygiene. Thus, the minimum hygiene level H _{min of} a washing machine and thus also the hygiene state of laundry items washed therein may differ, depending on whether the laundry to be treated is intended for allergy sufferers, the sick, the elderly or babies. Accordingly, therefore, the washing machine is set up so that a user can specify the washing machine H _min and thus can enter via an operating device.

The method according to the invention can be carried out at different times in a washing program, but preferably before a washing phase is carried out and after a first rinsing step of a rinsing phase. However, the process according to the invention does not always have to be carried out in connection with a specific washing program. Rather, it can advantageously be provided that the method is performed only after a certain period of use of the washing machine.

In addition, the method according to the invention can be carried out independently of a washing program. If the method according to the invention is to be carried out only after a specific period of use of the washing machine, a suitable measure is preferably used for the period of use. For example, there may be a counter that counts the number n of washing programs carried out in the washing machine since a last measurement or after a last cleaning program. Upon reaching a predetermined maximum number n _max then the implementation of a method according to the invention can be provided. Another measure may be the weight M of the previously washed laundry, which is obtained by adding up the individual load levels during the period of use. Upon reaching a predetermined maximum weight M _max , the execution of a method according to the invention can then be provided. Finally, as a measure of the actually past since a last measurement or after a last cleaning program period can be used.

In a preferred embodiment of the method according to the invention, therefore, the impedance signal is measured and with regard to deposits on the Impedance sensor evaluated as a measure of the degree of hygiene H of the washing machine, if since a last measurement a predetermined period of use, ie a predetermined period of use, the washing machine has elapsed. In embodiments of the invention, a cleaning program can be initiated even if the deposits on the impedance sensor itself are not yet sufficient for an evaluation that H _{min is} undershot, but it is determined by the impedance sensor or another sensor that residual detergent or ( microbial) dirt due to introduced water has partially solved.

According to the invention, it is preferred that in the measurement of the impedance in a rinsing phase, preferably in one of the last or last rinsing step, any influence of detergent or dirt still present in the rinsing liquid be taken into account, wherein in the control device a relationship between impedance signal and Detergent concentration and dirt and different amounts of deposits deposited on the impedance sensor.

In the method according to the invention, impedance signals are generally recorded and evaluated by the impedance sensor being acted upon by alternating voltage with the electrical impedance of the impedance sensor and the impedance signals are evaluated with respect to the phase angle φ and the amount of impedance, in order to determine the occupancy of the impedance sensor with deposits and in particular to determine the presence of a biofilm or constituents thereof. Phase angle φ and amount of impedance may be evaluated in embodiments of the invention in view of the type, amount and concentration of deposits, for example components of a biofilm, or particle deposits, such as lime, detergent residues, zeolites, debris, etc.

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. Various representations are known to the person skilled in the art, for example the Nyquist representation, in which the real part or the imaginary part of the impedance is dependent on the applied AC frequency can be represented. For characterization of the impedance spectrum, generally only a few characteristic points are suitable (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, it is generally possible to derive important information for the occupancy of the impedance sensor with deposits. In this case, the conductivity of the aqueous liquid can be determined, for example, 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 coating and the aqueous liquid surrounding it, 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.

Thus, a degree of hygiene can be determined, for example, by using an impedance sensor, which can preferably specifically indicate the presence of deposits in the washing machine, in particular biofilms.

The inventive method can also be combined with another method for determining the degree of hygiene H, for example by using a predetermined amount of a biocide such as ozone and an evaluation of the consumption of the biocide. In addition to the inventively provided measurement with an impedance sensor, the degree of hygiene can be determined, for example, by changing a concentration or amount of a disinfecting agent, such as ozone. Possibly. can be made by such a measurement, a calibration of an impedance sensor. In this case, it makes sense to exclude or minimize a possible influence of inorganic or organic non-living impurities. This could be done, for example, by setting a degree of contamination already detectable by a user visually with such inorganic or organic contaminants by a user or by means of sensors possibly present in the washing machine. In a preferred embodiment of the invention, the impedance signals are evaluated in terms of electrical conductivity as a measure of a water hardness, in particular when recording a reference signal. This makes it possible to estimate the formation of deposits of detergent ingredients and ions contained in the water used. Depending on the observed tendency of the wash liquor used in a wash program to form such deposits, the service life of the washing machine, which is preferably to be fulfilled as a prerequisite for carrying out the method, may be adapted. For example, in the case of a great tendency to form such deposits, this time is relatively short.

The invention also relates to a washing machine with a tub, a drum for receiving laundry, a drive motor for the drum, a control device for controlling at least one washing process, and with an arranged in the washing machine impedance sensor, in the course of a washing process in contact with an aqueous liquid is provided, wherein the control device is adapted to carry out a method in which an impedance signal is measured and evaluated with regard to deposits on the impedance sensor as a measure of the degree of hygiene H of the washing machine.

In a preferred embodiment, the impedance sensor is arranged in the tub, the dispenser tray and / or on the drum. Most preferably, the impedance sensor is arranged in a rear half of the tub, a lower half of a heating bag arranged in the tub and / or on the back of the drum.

In a preferred washing machine according to the invention, a temperature sensor is arranged in the tub, and in the control device a relationship between impedance signals and the type and amount of deposits on the impedance sensor is stored for various temperature values measured with the temperature sensor.

In the washing machine also other sensors for monitoring and controlling the operation can be used, for example, 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. The display device may for example consist of one or more LEDs, which may indicate a degree of hygiene H of the washing machine by lighting or non-lighting or by displaying different colors. Alternatively or in addition to this, for example, a liquid crystal display may be present.

In embodiments of the invention, the knowledge of the amount of water flowing into the tub or water 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 control device is in particular also designed to carry out a plurality of selectable laundry treatment programs.

The cleaning program can be carried out in different ways, wherein a washing machine according to the invention may contain different further components depending on a cleaning program to be carried out. Thus, for example, a reservoir already mentioned above for a cleaning fluid or of cleaning, in particular biocidal additives may be present. In embodiments, the washing machine may include, for example, an apparatus for providing ozone, in particular an ozone generator or an opening or a buffer for an ozone-containing liquid. The control device of the washing machine is then usually designed to control the generation and / or supply of ozone or an ozone-containing liquid. An ozone removal device and / or various controllable closure devices are then usually also present.

The invention has numerous advantages. Thus, impurities and deposits, in particular the formation of a biofilm, can be detected at an early stage. This allows their early and thus comparatively simple elimination before a user of the washing machine perceives the negative effects, such as a bad smell. It can be ensured that a washing machine constantly meets the hygienic requirements. The invention also allows in embodiments particularly suitable cleaning programs as remedial measures. The washing machine is not only not damaged by a cleaning program, it can also be extended a life of the washing machine. Although the invention allows the use of aggressive cleaning fluids, they can be dispensed with. Thus, the invention allows an early cleaning program in which, for example, the use of hot water, possibly with little aggressive biocidal additives, is sufficient.

The invention has the advantage that it is possible in a simple and efficient way to determine the hygiene level of laundry treatment equipment and display. Finally, the method according to the invention makes it possible to provide improved laundry treatment programs and hygiene programs, in particular for improving the degree of hygiene. This achieves a general improvement in the hygiene of the laundry, which can also be specifically improved for special user groups such as allergic persons. The result is a Carefree washing possible, while also excessive temperatures can be avoided. As a result, the laundry can be spared and energy consumption reduced.

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 of the figure has a tub 2, in which a drum

3 rotatably supported 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 conjunction with specially shaped Wäschemitnehmern 14 and scooping means 17 for the wash liquor 7 on the inner surface of the drum shell also also an intensification of the flooding of the laundry items

4 with wash liquor 7 reached. In the dispensing tray 12, an impedance sensor 10 is arranged, which is generally an electrode system of a plurality of electrodes, for example, two capacitor plates. With the aid of impedance sensor 10, deposits present in the dispensing tray 12 as well as any biofilm that may be present can be detected and analyzed, so that a cleaning program can be carried out early and in an optimized manner.

The washing machine 1 also has a liquor inlet system comprising 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 also be guided over 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 Readings from Parameters such as liquor level, liquor temperature, speed of the drum, etc. may be bound within the washing machine 1.

6 indicates a pressure sensor, i. a sensor for measuring the hydrostatic pressure, in the tub 2. The hydrostatic pressure p results from the level of the free liquor 7 forming in the tub 2, i. In addition, the washing machine 1 comprises 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 off the wash liquor 7.

In the figure, 9 denotes an impedance sensor in the tub 2, wherein the structure of electrodes is not shown here in detail. The impedance sensor 9 is arranged in a rear half of the tub 2. For carrying out the method according to the invention, of embodiments thereof and of washing programs, the signals of the impedance sensors 9 and 10 and the rotational speed of the drum 3, their loading with laundry items, the hydrostatic pressure, etc., and the measured values are fed to the control device 8. 1 1 means a display device with which a detected degree of hygiene of the washing machine can be displayed. For this purpose, for example, the determination of an insufficient degree of hygiene, ie if the degree of hygiene is less than a prescribed minimum value H _min , be displayed, for example, in the representation of the hygiene state by lighting a red diode. If, on the other hand, the degree of hygiene is sufficient, this circumstance can be indicated by the lighting up of a corresponding green LED.

Finally, with the display device 1 1, the execution of a cleaning program can be displayed, in addition, cleaning parameters such as the temperature of an aqueous liquid used and any additives can be displayed. To measure the temperature of the aqueous liquid, a temperature sensor 22 is present in the tub. 23 means a storage container for a cleaning liquid, in which preferably cleaning, in particular biocidal additives are present.

In addition, with the display device 1 1 also process parameters of a washing program carried out in the washing machine 1 can be displayed, such as a temperature of the wash liquor, a residual duration of the program, a loading amount.

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 impedance sensor in the tub; 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

23 reservoir for a cleaning fluid

Claims

Method for determining a degree of hygiene H of a washing machine (1) with a tub (2), a drum (3) for receiving items of laundry (4), a drive motor (5) for the drum (3), and a control device (8) for Controlling at least one washing program, characterized in that with an impedance sensor (9, 10) arranged in the washing machine (1), which comes into contact with an aqueous liquid (7) in the course of a washing program, an impedance signal is measured and the impedance signal with respect to Deposits on the impedance sensor (9,10) as a measure of the degree of hygiene H of the washing machine (1) is evaluated.

A method according to claim 1, characterized in that the impedance sensor (9,10) in a dispensing tray (12), the tub (2) and / or on the drum (3) is arranged.

A method according to claim 1 or 2, characterized in that the deposition on the impedance sensor (9, 10) is a biofilm.

Method according to one of claims 1 to 3, characterized in that before carrying out a first laundry treatment in the washing machine (1) in the presence of water (7) an impedance signal of the impedance sensor (9, 10) is measured and in the control device (8) as Reference measurement, which corresponds to a maximum degree of hygiene H _max deposited.

Method according to one of claims 1 to 4, characterized in that the impedance signal is measured and evaluated with regard to deposits on the impedance sensor (9, 10) as a measure of a hygiene state H of the washing machine (1) by using as an aqueous liquid (7). a rinsing liquid from the last rinsing step of a rinsing phase or water is used.

6. The method according to any one of claims 1 to 5, characterized in that the impedance signal with respect to the degree of hygiene H of the washing machine (1) is evaluated and taken when reaching or falling below a minimum level of hygiene H _min remedial measures.

7. The method according to claim 6, characterized in that as a remedial action, a cleaning program is automatically performed with a cleaning liquid, which has a predetermined high minimum temperature T _min1 and / or contains cleaning additives with a cleaning force F-ι, wherein the cleaning liquid preferably in a in the washing machine (1) arranged storage container (23) is stored.

8. The method according to claim 7, characterized in that after performing the cleaning program in the presence of water in terms of remaining deposition residues on the impedance sensor (9, 10) again picked up an impedance signal and evaluated to determine whether the sanitary condition is above H _min .

9. The method according to claim 8, characterized in that upon detection of a hygiene condition H <H _min a cleaning program is performed with a cleaning liquid having a predetermined high minimum temperature T _min2 ^ T _min1 and / or cleaning additives with a cleaning force F ₂ ^ Fi contains.

10. The method according to any one of claims 6 to 9, characterized in that reaching or falling below the minimum level of hygiene H _min on a display device (1 1) is displayed.

1 1. Method according to one of Claims 6 to 10, characterized in that the cleaning program is carried out while a movement program of the drum (3) deposited in the control device (8) is carried out.

12. The method according to any one of claims 6 to 1 1, characterized in that the execution of a cleaning program on the display device (1 1) is displayed.

13. The method according to any one of claims 1 to 12, characterized in that the impedance signal is measured and evaluated in terms of deposits on the impedance sensor (9,10) as a measure of the degree of hygiene H of the washing machine (1), if since a last measurement a predetermined service life of the washing machine has elapsed.

14. washing machine (1) with a tub (2), a drum (3) for receiving laundry items (4), a drive motor (5) for the drum (3), a control device (8) for controlling at least one washing process, and with an impedance sensor (9, 10) arranged in the washing machine (1), which comes into contact with an aqueous liquid (7) in the course of a washing process, characterized in that the control device (8) is arranged to carry out a method an impedance signal is measured and evaluated with regard to deposits on the impedance sensor (9, 10) as a measure of the degree of hygiene H of the washing machine (1).

15. Washing machine (1) according to claim 14, characterized in that the impedance sensor (9,10) in a rear half of the tub (2), a lower half of the tub in the tub (2) arranged heating pocket and / or on the back of the drum (3) is arranged.