EP2418315B1 - Household device with measuring device and method for determining a status parameter in a household appliance - Google Patents

Description

The invention relates to a domestic appliance with at least one liquid meter and the further features of the preamble of the independent device claim. The domestic appliance can in particular be a water-bearing domestic appliance, in particular a laundry cleaning appliance. The invention further relates to a method for determining at least one state parameter in a domestic appliance with the further features of the preamble of the independent method claim. The state parameter can in particular be a liquid-related state parameter, in particular a fill level.

In water-bearing domestic appliances in particular, knowledge of a current water level is necessary for a process control. In washing machines in particular, the water level is a value that deviates from the amount of water taken in due to the suction behavior of a laundry and must therefore be recorded explicitly.

EP 1 610 102 A1 discloses a device for detecting the level in a container. A container, preferably for storing condensate in a household clothes dryer, is to be monitored for its filling status. The container has walls enclosing a cavity made of dielectric material, preferably plastic, and electrodes formed from electrically conductive material as elements of an electrical capacitor which is coupled to an evaluation circuit in the operating position of the container. In order to improve the sensitivity and accuracy of the measurement, the body of the container forming the cavity has a shape on the two opposing boundary walls, which correspond closely to the at least approximately parallel electrodes and whose distance from one another is suitable for using typically small measuring voltages between the electrodes to create an almost interference-free electrical field.

WO 2009/027242 A1 relates to a device and method for determining a fill level within a tub of a washing machine. The device for determining a level of liquid within a container of a water-carrying Household appliances, in particular a washing machine, are equipped with a level sensor, by means of which a pressure value generated by the liquid can be detected, the level sensor being arranged at least with a detection part in a lower region of the container covered with the liquid during the washing process. A determination device can be provided, by means of which the fill level of the liquid can be determined on the basis of the pressure value detected by the fill level sensor.

EP 1 557 651 A1 discloses a liquid-carrying domestic appliance with an optical fill level sensor, which comprises a light guide, a light source and a light sensor, and an evaluation unit for determining a state parameter of the liquid on the basis of the measurement data received with the light sensor, the state parameter to be determined being a fill level of the liquid in the domestic appliance is. In addition, a method for determining a state parameter of the liquid, namely a fill level, is also disclosed in the domestic appliance.

Also disclosed DE 10 2007 012166 A1 a method for determining a fill level of a liquid in a domestic appliance and the domestic appliance in the form of a washing machine, a dishwasher or a vending machine are known, which comprises an optical sensor for determining a fill level in the domestic appliance, the fill level using the transmission and reflection behavior of light coupled into an optical fiber of the sensor at an interface.

It is the object of the present invention to provide a possibility in a domestic appliance with which, with an optical sensor suitable for the level measurement, it is particularly cost-effective and versatile to determine at least one state parameter of a liquid in the domestic appliance that deviates from the level.

This object is achieved in accordance with the features of the independent claims. Preferred embodiments can be found in particular in the dependent claims and the description below.

An optical fill level sensor can in particular be understood to mean a sensor or measuring sensor whose (disembodied) measuring medium or measuring carrier is light. The Optical fill level sensor is therefore based on at least one optical measurement for determining, in particular, a fill level in the household appliance.

Although the optical level meter can be used for a level measurement, it can also measure other status parameters and does not even need to be used for level measurement. The optical level meter can therefore also be referred to as an optical liquid meter.

The object is accordingly achieved by a domestic appliance having at least one optical fluid meter, the at least one fluid meter and the domestic appliance comprising the further features of claim 1.

The use of light as the measurement carrier has the advantage that a very high measurement resolution is allowed. Measurement inertia when using light is also very low, so that dynamic state parameters can also be detected with an acceptable outlay. Furthermore, the optical fill level sensor requires only a few, and moreover no moving parts, so that a robust and cost-effective construction is made possible.

The at least one optical level sensor is an evaluation unit, e.g. a microprocessor. The evaluation unit is set up at least to determine at least one state parameter of the liquid in the domestic appliance on the basis of the measurement data received from the at least one light sensor. The evaluation unit can e.g. be a dedicated evaluation unit or a central control unit.

The at least one state parameter comprises a refractive index.

The at least one state parameter can also include, for example, a fill level, a turbidity, a concentration of additives, a dirt content, a movement (for example sloshing) and / or a viscosity of the liquid.

The evaluation unit can also be set up to determine at least one state parameter of the domestic appliance, e.g. for determining a degree of calcification, an unbalance of the loaded household appliance, etc.

Furthermore, the optical fill level sensor has at least one light guide that is at least partially wettable with a liquid, at least one light source by means of which light can be coupled into the light guide, and at least one light sensor for detecting light that is coupled out of the light guide.

In addition, the domestic appliance has at least one evaluation unit for determining at least one state parameter, in particular a fill level, of the liquid in the domestic appliance on the basis of the measurement data received from the at least one light sensor.

For example, to determine a fill level, a light guide that extends at least beyond the maximum fill level or level to be measured can be fed with light of a suitable wavelength by means of the at least one light source. At least a part of the injected or injected light can be totally reflected on the walls of the at least one light guide. The degree of total reflection differs between dry wall areas and wet wall areas or those wetted with the liquid, in particular water. The angle of the total reflection in the light guide can in particular be such that most of the light is reflected back into the inside of the light guide at the dry wall areas of the light guide and a defined larger proportion of the light exits into the surrounding liquid in wet wall areas. Detection of light locally coupled out of the light guide by means of the at least one light sensor (e.g. measurement of a light intensity, intensity, brightness, etc. of the light) consequently provides a change, in particular attenuation, of the light coupled out as a function of the fill level. For example, the higher the liquid is, the more light can escape from the wet wall areas or sides of the light guide, and the weaker the light that enters the at least one light sensor.

The at least one light source preferably comprises at least one light-emitting diode. If several light-emitting diodes are present, they can be of the same color or different Colors glow. A color can be monochrome (e.g. red, green, blue, etc.) or multichrome (e.g. white). The light emitted by the at least one light-emitting diode can also be an infrared light (IR LED) or an ultraviolet light (UV LED). The at least one light-emitting diode can be in the form of at least one individually packaged light-emitting diode or in the form of at least one LED chip. Several LED chips can be mounted on a common substrate ("submount"). The at least one light-emitting diode can be equipped with at least one of its own and common optics for beam guidance, for example at least one Fresnel lens, a collimator, and so on. Instead of or in addition to inorganic light-emitting diodes, for example based on InGaN or AlInGaP, organic light-emitting diodes are generally also (OLEDs, for example polymer OLEDs) can be used. The LEDs have the advantage of being very durable, robust, narrow-band, compact and easy to control. Alternatively, the at least one light source can have, for example, at least one diode laser. However, the at least one light source is not limited to a semiconductor light source and can, for example, also include other lasers, incandescent lamps, fluorescent tubes, etc.

The liquid can be, for example, water or a washing liquid (e.g. liquid washing liquor). The liquid can contain additives of various types, such as cleaning additives or impurities. Water with cleaning additives can also be referred to as a lye. The water can thus also generally be regarded as a water-based liquid.

It is a further development that the light guide is essentially made of a plastic that is transparent to the light emitted by the light source, for example PMMA. The light guide can have an inhomogeneous refractive index, in particular a refractive index that changes from the inside to the outside, in order to keep optical losses at reflection points small. For a simple and inexpensive design of the The light guide can have a homogeneous refractive index. The light guide can then be produced in particular as an injection molded part.

The light source and the light sensor can be provided as separate components or as an integrated unit (optical transceiver), preferably on a common carrier. If the light source and the light sensor are configured as a transceiver, the light can be detected by the light sensor in particular after a reflection at a free end of the light guide. The free end can then, in particular, be mirrored to increase the luminous efficiency.

To increase the luminous efficiency, at least one wall or surface, in particular a surface area provided as a light passage area, can have at least one optical function, e.g. be designed as a converging lens, a diverging lens, a prism, a mirror, etc.

The household appliance can in particular be a laundry care appliance, e.g. a washing machine or a washer-dryer, but also, for example, a tumble dryer, a dishwasher, etc. If the household appliance is a laundry cleaning device, such as a washing machine or a washer-dryer, the liquid can in particular be water (lye, rinse water, etc.).

In particular if the household appliance is a laundry cleaning device, the light guide can be inserted between two suds container halves when the suds container is being installed.

In particular if the domestic appliance is a laundry cleaning appliance, it is an embodiment that the light guide is arranged at least in sections on an inside of a tub. The light guide is then advantageously at least approximately similar to the shape of the inside of the tub, for example similar to a cylinder sector. Since the lye rises in the tub, a simple level measurement is obtained by wetting the light guide area accommodated in the tub. A possible non-linearity between the light intensity detected by the at least one light sensor and the fill level due to a curvature of the light guide can be taken into account by using corresponding characteristic curves.

It is also an embodiment that the light guide is a film. As a result, the light guide can be manufactured particularly inexpensively, can be made compact and can be used in confined spaces. In particular, several light guides can also be integrated into the film, e.g. for parallel measurements. If the domestic appliance is, for example, a laundry cleaning appliance, the light guide can be a film applied to the inside of the tub. As a result, an intermediate space between the tub and a laundry drum does not have to be redesigned, and the optical level sensor is particularly easy to integrate into the laundry cleaning device.

It is also an embodiment that the light guide is integrated in a container wall of a liquid container. In particular, the container wall can be designed as such as the light guide, e.g. by production from a plastic or glass that is translucent, in particular transparent, for the light. As a result, the light guide as a separate component can be dispensed with and a particularly reliable and inexpensive design is made possible. If the domestic appliance is, for example, a laundry cleaning appliance, it is an embodiment that the light guide is integrated in the tub. The tub can in particular be made at least partially from a plastic suitable as a light guide. The tub can e.g. be made at least partially of a plastic that is permeable to the light of the light source, specifically over the permitted fill level range.

It is also an embodiment that the domestic appliance has an integrated optical measuring unit with at least one optical level sensor and a measuring tube, at least one side wall of the measuring tube being part of an optical fiber of the at least one optical level sensor. The measuring tube is connected by means of at least one fluid channel to a liquid container of the domestic appliance, the level of which is to be measured by means of the optical measuring unit. On the basis of the principle of the communicating tubes, the fill level of the liquid container can be mapped and determined in the measuring tube. As a result, the optical fill level measurement can also be arranged at a distance from the liquid container, which allows a high degree of design flexibility. Because the light guide and the measuring tube are integrated with one another, they can be manufactured particularly reliably, inexpensively and in a space-saving manner, in particular in one piece, for example made of plastic by means of an injection molding process, or of glass. The measuring tube can be configured, for example, as a cuvette. The at least one light source and the at least one light sensor can have been preassembled on the light guide before the optical measuring unit is installed in the domestic appliance. The at least one light source and the at least one light sensor can in particular be configured as at least one optical transceiver.

It is also an embodiment that the at least one light source couples light of several wavelengths into the at least one light guide, the at least one light sensor detects light of these multiple wavelengths and the evaluation unit is set up on the basis of the measurement data received from the at least one light sensor for the several wavelengths to determine a state parameter of the liquid surrounding the light guide ('spectroscopic measurement'). The light of the several or different wavelengths can be coupled sequentially or simultaneously into the at least one light guide. The spectroscopic measurement can in particular provide additional information about the refractive index of the liquid surrounding the light guide. This takes advantage of the fact that, under otherwise identical circumstances (in particular with the same fill level), the portion extracted from the light guide is dependent on the refractive index of the medium to be measured. For a given refractive index, the absorption at a wavelength as a function of the fill level is given by a function (which can be described e.g. by a characteristic field, the parameter of which is the refractive index of the surrounding medium). Sufficiently large differences in the characteristic curve fields are assumed for different wavelengths, so that the respective curve of the characteristic curve field is clearly defined for the given situation in the case of measured absorption values for the different wavelengths with identical fill levels and an identical refractive index. Depending on the measurement precision set, additional information can be obtained from this, for example about a lye concentration or a dirt content in the liquid. It is comparatively easy to integrate any number of other light sources and light sensors.

However, it is also possible to determine the refractive index of the liquid surrounding the light guide by means of a measurement with only one wavelength if a defined fill level is known. The defined fill level can be achieved, for example, by targeted filling with the liquid. It takes advantage of the fact that given Level the amount of light transmitted in the light guide depends, among other things, on the refractive index of the surrounding medium. A calibration curve of the sensor then has an additional dimension, namely the refractive index of the surrounding medium or, in the case of a discrete application, a characteristic field. Assuming a constant dependency on the refractive index, the curves in the characteristic curve field are free of overlaps; it is initially not clear during a measurement which characteristic curve the measuring point is in in the characteristic curve field. However, the characteristic curve can already be identified by a single known point, this point can be determined by a known parameter, in this case a defined fill level. The defined fill level can be specified with a second sensor, here for example the flow sensor. To ensure that there is no interference with the measurement caused by the laundry in a drum filled with laundry, the measuring point is preferably below an immersion area of the drum.

It is a further embodiment that the optical fill level sensor has two spaced apart, optically couplable light guides, one of the light guides being optically coupled to the at least one light source and at least the other of the light guides, in particular both light guides, being optically coupled to at least one light sensor , Instead of or in addition to a measurement of the light attenuation, the light emerging during a reflection in a first of the light guides (which previously corresponds to the scattered light which is no longer used) will now run through the liquid and couple into a second of the light guides. The light intensity or the like measured on the second light guide. increases with increasing level or level of the liquid.

In order to keep the yield of light in the light sensor high, at least one phosphor (fluorescent dye, also called phosphorus, but not to be confused with the chemical element phosphorus) can be added to the second light guide his. Coupled light is reduced in frequency by the phosphor (so-called 'downconversion'), as a result of which the total reflection angle changes along with a reduced probability of exit or loss.

If optical measurement structures with different characteristics are used, the evaluation unit can be set up to differentiate between different media, in particular media of different consistency. This can be done, for example, by the optical fill level sensor being two spaced apart from one another has optically coupled light guides, one of the light guides being optically coupled to the at least one light source and both light guides being optically coupled to at least one respective light sensor. In this case, for example, water can ensure good light transmission from a first of the light guides to a second of the light guides , while foam, for example, also couples light out of the first light guide, but to a lesser degree than the water. Since the foam is not transparent (transparent) but translucent (opaque), light coupled out of the first light guide into the foam is only coupled to a small extent into the second light guide and is mainly scattered away to the side. The light component coupled into the second light guide due to the foam is therefore negligible compared to the light component coupled due to the water. By comparing the light intensity or the like on the light sensor of the first light guide and the light sensor of the second light guide, air, water and foam can be separated from one another by sensors. In particular, an amount of foam can be determined and the level of the liquid can be determined more precisely. Knowledge of the amount of foam can be used, for example, to determine a point in time at which cleaning agent is washed out of a laundry (low foam formation). With further dimensions of the optical measurement, further optical properties of the media (liquid, foam, etc.) in the household appliance can be recorded, such as the turbidity. The turbidity can be determined, for example, by an absorption of light through a predetermined absorption section filled with the liquid. The absorption path can correspond, for example, to a fill level measuring path in the optical fill level sensor. The turbidity sensor principle can thus be integrated into the optical level sensor.

It is also an embodiment that the at least one light guide has a stepped or discontinuous structure. The staged structure enables measurement even in the case of heavy soiling and under adverse environmental conditions by recognizing and counting corresponding stages in the measurement signal, for example with defined measuring points in each case at the stages and an interpolation in between.

The stepped structure can in particular comprise a stepped structure of an outside or surface of the light guide. The outside or surface of the light guide can be designed, for example, in the form of at least one periodic function, in particular along a longitudinal orientation of the light guide. The periodic function can, for example a sine function, a triangle function or a rectangular function. The periodic function is characterized by the different degrees of light decoupling from the course of the light signal. Contamination of the surface of the light guide can weaken the measurable light intensity or the like overall, but the width of the steps changes only insignificantly as a result of the contamination and is still easy to detect.

It is furthermore an embodiment that the domestic appliance has at least two optical fill level sensors of different types and at least one evaluation unit for jointly evaluating the measurement data received from the at least two optical fill level sensors. As a result, further information about a state of the liquid and / or the household appliance can be obtained.

It is also an embodiment that the evaluation unit is set up to determine an oscillation state of the liquid and / or the household appliance on the basis of the measurement data. This takes advantage of the fact that the optical measurement enables a very fast acquisition of measured values. There is practically no smoothing of the measurement signals due to the measurement principle. For example, at a given level, it is possible to determine a phase and amplitude of an oscillating state of vibrating parts of the household appliance that are mechanically coupled to the liquid (fluid) from an oscillation (in particular a periodic sloshing (a strong movement of the water surface due to a vibration system dynamics)) of the liquid derive. This information (s) can e.g. for intelligent laundry distribution (i.e., a reversing of the drum controlled by special algorithms for redistribution of the laundry). In particular, the use of optical fill level sensors in pairs at different locations in a tub allows the detection of diagonal imbalances that are not or only difficult to detect with conventional 3D sensors. In particular, two or more sensors can better detect a movement of a surface of the liquid, which in turn allows conclusions to be drawn about a diagonal imbalance.

Another embodiment is that the evaluation unit is set up to determine at least one fluid mechanical property of the liquid, in particular a viscosity, on the basis of the measurement data. The optical level sensor is special sufficiently fast to also detect vibrating or sloshing fill levels or water levels.

Averaging to determine the (average) fill level can be done, for example, by filtering the measurement signal; In addition to analog filters, digital filters, software filters or the like are also particularly suitable. Alternatively, e.g. a mechanical low-pass system can be used, for example due to the spatial separation of the liquid container and the optical fill level sensor described above and their hydraulic connection according to the principle of the communicating tubes, in which the fill level in the measuring tube practically does not understand vibration of the liquid in the liquid container. In particular with a logical filtering, e.g. Using electronics and / or software, information about (fluid) mechanical data can also be extracted from the vibrations or from the sloshing of the liquid, for example a viscosity of the liquid, e.g. Suds. The viscosity in turn can be used as an input variable for determining the purity of the liquid. It can be exploited that, according to Hagen-Poiseuille's law, a flow velocity in a pipe (under laminar conditions) is inversely proportional to the viscosity of the liquid. The viscosity can therefore be inferred from a measurement of a flow velocity or a decay of a vibration in a pipe system or similar data.

It is also an embodiment that the evaluation unit is set up to determine at least one contamination parameter of the water-carrying domestic appliance on the basis of the measurement data and to initiate at least one step provided for eliminating contamination of the water-carrying domestic appliance on the basis thereof.

In this way, reference or compensation signals from the optical level sensor can be used to detect contamination of the machine. For example, calcification of the light guide can be recognized by an increased coupling-out of light at the reflection points compared to a non-calcified light guide, in particular by means of a reference measurement in an unfilled state, for example before water is run in at the beginning of a washing cycle or a rinsing cycle. To For example, a single reference measurement can provide information about a degree of contamination with the light guide, but not about its distribution. A comparison with the light coupling known for the new, unpolluted light guide can be used to infer average contamination of the light guide. Additional information about a vertical distribution of the pollution can be obtained from the above-mentioned spectroscopic measurements or measurements at defined water levels.

The steps to remove the pollution can e.g. carrying out a self-cleaning program and / or issuing a note, e.g. a maintenance notice or the like to a user. Depending on the number of dimensions of the optical fill level sensor, information about the degree of contamination and information about its homogeneity and distribution (e.g. with calcification with a clear focus in a lower area) and about its development over time and for controlling the household appliance can be obtained use.

It is still a further embodiment that the at least one optical fill level sensor, in particular its at least one light guide, is arranged in an inflow region of fresh water of the domestic appliance. The inflowing fresh water can be used to flush the optical fill level sensor from impurities, for example to enable precise detection of foam. The fresh water supply can be interrupted (for a short time) for a particularly precise measurement. The flushable sensor can be used, in particular, as a reference (for example for detecting a machine status) together with a second optical fill level sensor at a point that cannot be flushed away.

In general, the level measurement is not limited to a water-based liquid, but can e.g. can also be used for liquid detergents etc. Accordingly, the invention is not limited to water-bearing domestic appliances.

• Einkoppeln von Licht in mindestens einen Lichtleiter, wobei der mindestens eine Lichtleiter zumindest teilweise von der Flüssigkeit benetzbar ist;
• Auskoppeln von Licht aus dem mindestens einen Lichtleiter in mindestens einen Lichtsensor und
• Bestimmen mindestens eines Zustandsparameters, insbesondere eines Wasserstands, der Flüssigkeit in dem Hausgerät auf der Grundlage von Messdaten des mindestens einen Lichtsensors.

The object is also achieved by a method for determining at least one state parameter, in particular a fill level, of a liquid in a domestic appliance with the further features of claim 14, wherein the method comprises at least the following steps:

• Coupling light into at least one light guide, the at least one light guide being at least partially wettable by the liquid;
• Coupling out light from the at least one light guide into at least one light sensor and
• Determining at least one status parameter, in particular a water level, of the liquid in the household appliance on the basis of measurement data from the at least one light sensor.

With the method, a refractive index of the liquid surrounding the light guide is determined as the state parameter.

The task can in particular be further developed analogously to the household appliance described above.

The invention has the advantages, among other things, that with a simultaneously high integration density, there is a cost advantage and a smaller number of components compared to conventional sensors. A parallel measurement using different optical principles (e.g. coupling vs. coupling, different wavelengths, etc.) enables the acquisition of several dimensions with additional information on the type, quantity and distribution of the media in multi-media systems (e.g. water-foam-air). A zero measurement can also provide information about the degree of contamination of the measuring device and thus e.g. in a washing machine over the tub. Including temporal aspects provides further information about the system (e.g. a viscosity of the liquid).

Fig.1

zeigt als Schnittdarstellung in Seiteneinsicht eine Prinzipskizze eines optischen Füllstandssensors gemäß einer ersten Ausführungsform;

Fig.2

zeigt als Schnittdarstellung in Seiteneinsicht eine Prinzipskizze eines optischen Füllstandssensors gemäß einer zweiten Ausführungsform;

Fig.3

zeigt als Schnittdarstellung in Seiteneinsicht eine Prinzipskizze eines optischen Füllstandssensors gemäß einer dritten Ausführungsform;

Fig.4

zeigt als Schnittdarstellung in Seiteneinsicht eine Prinzipskizze eines optischen Füllstandssensors gemäß einer vierten Ausführungsform;

Fig.5

zeigt eine Auftragung einer durch den optischen Füllstandssensor gemäß der vierten Ausführungsform detektierten Lichtstärke in Abhängigkeit von einem Füllstand;

Fig.6

zeigt in Seitenansicht einen Laugenbehälter einer Waschmaschine mit drei möglichen Lichtleitern.

The invention is described in more detail schematically in the following figures using exemplary embodiments. For clarity, the same or equivalent elements can be provided with the same reference numerals.

Fig.1

shows a sectional view in side view of a schematic diagram of an optical level sensor according to a first embodiment;

Fig.2

shows a sectional view in side view of a schematic diagram of an optical level sensor according to a second embodiment;

Figure 3

shows a sectional view in side view of a schematic diagram of an optical level sensor according to a third embodiment;

Figure 4

shows a sectional view in side view of a schematic diagram of an optical level sensor according to a fourth embodiment;

Figure 5

shows a plot of a light intensity detected by the optical fill level sensor according to the fourth embodiment as a function of a fill level;

Figure 6

shows a side view of a tub of a washing machine with three possible light guides.

Fig.1 shows a sectional view in side view of a schematic diagram of an optical level sensor 1 according to a first embodiment. The optical fill level sensor 1 has a rod-shaped light guide 2 made of PMMA of length L, which can be wetted at least partially with liquid F and which here stands vertically in a liquid container which can be filled with the liquid F, for example in a tub of a washing machine. A longitudinal section of the light guide 2 surrounded or wetted by the liquid F corresponds to a fill level h.

Light can be coupled into the light guide 2 via a first cover face or end face 3 of the light guide 2, as indicated here by the individual light beam S. The first end surface 3 cannot be wetted with the liquid. The light beam S that can be coupled into the light guide 2 is generated here by a light-emitting diode 4 and is essentially monochrome.

The light beam S passes through the light guide 2 and, since it runs obliquely to the longitudinal axis of the light guide 2, is totally reflected several times on the side wall or lateral surface 5 of the light guide 2 until it emerges or couples out at the other, second end face 6 and onto a light sensor 7 falls. The second end surface 6 is also not wettable by the liquid F. The total reflection is essentially loss-free or low-loss when the outer surface 5 is dry or not wetted with the liquid F at reflection points, and is substantially stronger when the outer surface 5 is wet or wetted with the liquid F at the location of the total reflection lossy. With the lossy Total reflection emits a certain proportion of the light S incident on the lateral surface 5 from the inside as scattered light T to the outside.

The light intensity detected by the light sensor 7 is thus clearly dependent on the fill level h or the relative fill level h / L. For example, an evaluation unit 8 functionally coupled to the light sensor 7, e.g. a control unit of a domestic appliance 9, from the measurement data of the light sensor 7 determine the fill level h. For this purpose, the evaluation unit 8 can e.g. Use one or more characteristic curves or look-up tables which relate the measurement data of the light sensor 7 to the fill level h.

The light-emitting diode 4 and / or the light sensor 7 can be attached essentially directly to the light guide 2 or at a distance therefrom.

The light-emitting diode 4 and the light sensor 7 can be arranged on the same end surface 3 or 6, in particular on the same carrier, the light sensor 7 then detecting light which has been reflected back on the other end surface 6 or 3 and thus the light guide 2 twice has gone through This arrangement is particularly compact and has an increased measuring accuracy. In order to reduce light losses at the end surface 3 or 6 reflecting the light back, this end surface 3 or 6 can be mirrored. The light emitting diode 4 and the light sensor 7 can in particular form a common optical transceiver unit, see also Fig.2 , The transceiver unit can also have electronics, for example for controlling the light-emitting diode 4 and / or for processing or processing the signals of the light sensor 7.

The domestic appliance 9 can in particular be a water-bearing domestic appliance such as a laundry cleaning appliance (washing machine, washer dryer, etc.). The liquid F can then in particular be a water-based liquid, in particular an alkali or rinse water.

Fig.2 shows a sectional view in side view of a schematic diagram of an optical level sensor 11 according to a second embodiment. The fill level sensor 11 is an integral part of an optical measuring unit 12, which additionally has a measuring tube 13 and a liquid channel 14. The measuring tube 13 is connected to a liquid container 15 by means of the liquid channel 14 on the principle of communicating tubes of a domestic appliance 16 hydraulically connected. As a result, a fill level or level in the measuring tube 13 corresponds to a fill level or level in the liquid container 15. The liquid container 15 here is an alkali container of a laundry cleaning device.

The light guide 17 of the optical fill level sensor 11 simultaneously represents a side wall 18 of the measuring tube 13, and both functional elements 17, 13 can be manufactured in one piece, in particular by means of a plastic injection molding process. The measuring tube 13 is designed here as a cuvette with plane-parallel side walls. The optical measuring unit 12 has a cutout 12a for receiving an optical transceiver 19. The optical transceiver 19 is directed directly adjacent to a light (on and off) coupling surface 20 of the light guide. The light coupling surface 20 can be designed as an optical element for shaping the light beam for a high luminous efficiency, e.g. lenticular. An opposite end surface 21 of the light guide 17 serves as a reflection surface and can be used for a high luminous efficiency e.g. be mirrored. The optical transceiver 19 can be preassembled in the recess 12a before the optical measuring unit is installed in the domestic appliance.

Figure 3 shows a sectional view in side view of a schematic diagram of an optical fill level sensor 21 according to a third embodiment for use in a domestic appliance 24. The optical fill level sensor 21 now has two light guides 22, 23 which are spaced apart and can be optically coupled to one another. The two light guides 22, 23 have the same shape and the same base material and are aligned parallel and adjacent to one another.

Similar to the optical fill level sensor 1, the first light guide 22 is optically coupled to the light-emitting diode 4 through the first end face 3a and is coupled to a first light sensor 7a through the opposite end face 6a.

The second light guide 23 has a light sensor 7b on its second end face 6b, but no light-emitting diode. The first end surface 6b, on the other hand, is mirrored so that light incident on it from the inside is reflected back and can run in the direction of the second end surface 6b. In order to keep the yield of light in the second light sensor 7b high, the second light guide 23 is mixed with at least one phosphor (fluorescent dye, 'phosphorus'). Coupled light is emitted by the phosphor in frequency reduced (so-called 'downconversion'), whereby the total reflection angle changes along with a reduced probability of exit or loss.

In addition to a measurement of the light attenuation, the light emerging during a reflection in the first light guide 22 (which previously corresponds to the scattered light that is no longer used) is continuously coupled laterally into the second light guide 23 by the liquid F. The light intensity or the like measured on the second light guide 23. consequently increases with increasing level or level h of the liquid F.

The optical fill level sensor 21 can be used here, for example, to quantitatively detect air A, liquid F and foam B.

In this case, the liquid F standing between the light guides 22, 23 results in good light transmission to the second light guide 23. The foam B, on the other hand, increases the output of light from the first light guide 22 (although not to the same extent as through the liquid) F), but then scattered through the foam B and only negligibly coupled into the second light guide 23. By comparing the light intensity of the two light sensors 7a and 7b, in particular in relation to the light intensity originally coupled in, a scattering loss due to the foam B can be estimated. The influence of the foam B can in turn be used to correct a level determination, which e.g. is carried out by means of the first light guide 22. Knowledge of the amount of foam or foam height can also be used as an input variable for controlling an operating cycle of the domestic appliance 24, for example for determining a point in time at which cleaning agent is washed out of a laundry.

Figure 4 shows a sectional view in side view of a schematic diagram of an optical level sensor 31 according to a fourth embodiment. The light guide 32 of the optical fill level sensor 31 is now provided, at least on one side region (here: the lateral surface 34), with a structure 33 which is stepped in a longitudinal extension, in particular rectangular. With a light guide 32, this structure can be achieved, for example, by regularly introducing circumferential grooves into the lateral surface 34 of the light guide 32.

The surface course, which is rectangular in the longitudinal orientation of the light guide 31, is impressed on the course of the light signal at the light sensor 7 by its different degree of light coupling. Figure 5 shows a suitable application of a light intensity I detected by the optical fill level sensor 31 as a function of a fill level h, each in any units. Contamination of the lateral surface 34 of the light guide 31, for example due to calcification or deposition of dirt particles, can indeed increase the measurable light intensity or the like. weaken overall, the width of the steps changes only slightly due to the contamination and is still easy to detect.

Figure 6 shows a side view of a tub 41 of a washing machine 42 with three possible light guides 43, 44, 45.

The light guide 43 has a part 43a which is curved to conform to an inside 46 of the tub 41 and which is guided downward through the sump 47 of the tub 41. An optical transceiver 19 is arranged at a lower free end of the light guide 43 outside of the tub 41. A fill level h, e.g. a lye. A nonlinear relationship between the fill level h and the light received at the transceiver 19 or the light attenuation due to the nonlinear design in the filling direction can be taken into account in the evaluation unit 8, e.g. by using appropriate corrections, e.g. Characteristics.

The light guide 43 can be designed as a film at least with regard to its curved part 43a. The use of the film enables a particularly economical, space-saving and easy-to-assemble design.

As an alternative or in addition, a light guide 44 can be used, which is constructed similarly to the light guide 43, but is attached to an outer side 48 of the tub 41 in a contacting manner. For this purpose, at least the area of the tub 41 in front of the light guide 44 is translucent for the wavelength (s) used in the optical measurement, in particular essentially transparent. Alternatively, one that is transparent for the wavelength (s) used in the optical measurement integral area of the tub 41 serve as a light guide of the optical level meter.

The light guides 43 and 44 have the advantage that they can be positioned between the outer surfaces of the tub and a washing drum rotatably mounted in the tub.

The light guide 45 is a rectilinear, upright light guide, which can also be positioned within the tub between the tub and the washing drum, can be integrated outside the tub or in the tub. The light guide 45 can also be used as a volume element, e.g. be designed as a rod-shaped element or as a film.

Of course, the present invention is not limited to the exemplary embodiments shown.

Any other suitable light source can also be used instead of the light-emitting diode, for example a laser diode or a broad-beam light source with a downstream filter. It is generally preferred that the incident light be narrow-band.

LIST OF REFERENCE NUMBERS

1

optical level sensor

2

optical fiber

3

first end face of the light guide

4

led

5

Shell surface of the light guide

6

second end face of the light guide

7

light sensor

8th

evaluation

9

household appliance

11

level sensor

12

optical measuring unit

12a

recess

13

measuring tube

14

liquid channel

15

liquid container

16

household appliance

17

optical fiber

18

Side wall of the measuring tube

19

optical transceiver

20a

Light coupling surface of the light guide

20b

End surface of the light guide

21

optical level sensor

22

first light guide

23

second light guide

24

household appliance

31

optical level sensor

32

optical fiber

33

tiered structure

34

Shell surface of the light guide

41

tub

42

Washing machine

43

optical fiber

43a

curved part of the light guide

44

optical fiber

44a

curved part of the light guide

45

optical fiber

46

Inside of the tub

47

swamp

48

Outside of the tub

H

level

L

Length of the light guide

S

beam of light

T

scattered light

Claims (15)

1. Household device (9; 16; 24; 42), in particular laundry cleaning appliance, having at least one optical liquid meter (1; 11; 21; 31), which has

   - at least one light guide (2; 17; 22, 23; 32; 43, 44, 45) which can be wetted at least partially with a liquid (F),

   - at least one light source (4), by means of which light (S) can be coupled into the light guide (2; 17; 22, 23; 32; 43, 44, 45), and

   - at least one light sensor (7; 7a, 7b) for detecting light coupled out of the light guide, and the household appliance (9; 16; 42) has at least one evaluation unit (8), which is embodied to determine at least one status parameter of the liquid (F) in the household appliance (9; 16; 42) on the basis of the measurement data received by the at least one light sensor (7; 7a, 7b),

   characterised in that
   the status parameter is a refraction index of the liquid surrounding the light guide (2; 17; 22, 23; 32; 43, 44, 45).
2. Household appliance (9; 16; 24; 42) according to claim 1, characterised in that

   - the at least one light source (4) couples light of various wavelengths into the at least one light guide (2; 17; 22, 23; 32; 43, 44, 45),

   - the at least one light sensor (7; 7a, 7b) detects light of these various wavelengths and

   - the evaluation unit (8) is designed to determine the refraction index of the liquid surrounding the light guide (2; 17; 22, 23; 32; 43, 44, 45) on the basis of the measurement data received by the at least one light sensor (7; 7a, 7b).
3. Household appliance (9; 16; 24; 42) according to claim 1 or 2, characterised in that the household appliance (9; 16; 42) is a laundry cleaning appliance and the light guide (2; 17; 22, 23; 32; 43, 44, 45) is arranged at least in sections on an interior of a tub (41).
4. Household appliance (42) according to claim 3, characterised in that the light guide (43, 43a) is a film attached to the interior (46) of the tub (41).
5. Household appliance according to claim 1 or 2, characterised in that the household appliance is a laundry cleaning appliance and the light guide is integrated into the tub.
6. Household appliance (24) according to one of the preceding claims, characterised in that

   - the optical liquid meter (21) has two light guides (22, 23) which are at a distance from one another and can be optically coupled with one another,

   - one of the light guides (22) is optically coupled to the at least one light source (4) and

   - at least the other of the light guides (23), in particular both light guides (22, 23), are optically coupled to at least one light sensor (7a, 7b).
7. Household appliance according to one of the preceding claims, characterised in that the at least one light guide (32) has a stepped design.
8. Household appliance according to one of the preceding claims, characterised in that the household appliance has at least two optical liquid meters (22, 23) of a different type and at least one evaluation unit (8) for jointly evaluating the measurement data received by the at least two optical liquid meters (22, 23).
9. Household appliance (9; 16; 24; 42) according to one of the preceding claims, characterised in that the evaluation unit is designed to determine a fill level (h) in the household appliance (9; 16; 24; 42) on the basis of the measurement data.
10. Household appliance (9; 16; 24; 42) according to one of the preceding claims, characterised in that the evaluation unit is designed to determine an oscillation state of the household appliance (9; 16; 24; 42) on the basis of the measurement data.
11. Household appliance (9; 16; 24; 42) according to one of the preceding claims,
    wherein the evaluation unit (8) is designed to determine at least one fluid-mechanical property of the liquid, in particular a viscosity, on the basis of the measurement data.
12. Household appliance (9; 16; 24; 42) according to one of the preceding claims,
    wherein the evaluation unit (8) is designed to determine at least one soiling parameter of the household appliance (9; 16; 24; 42) and on the basis of the measurement data and on its basis to initiate at least one step provided to eliminate a soiling of the household appliance (9; 16; 24; 42).
13. Household appliance (9; 16; 24; 42) according to one of the preceding claims,
    wherein the at least one optical liquid meter, in particular its at least one light guide, is arranged in an inflow region of fresh water of the water-conducting household appliance.
14. Method for determining at least one status parameter of a liquid (F) in a household appliance (9; 16; 24; 42), which has at least one evaluation unit (8) for determining the at least one status parameter of the liquid (F) in the household appliance (9; 16; 42) and at least one optical liquid meter (1; 11; 21; 31), wherein the optical liquid meter (1; 11; 21; 31) has

    - at least one light guide (2; 17; 22, 23; 32; 43, 44, 45) which can be wetted at least partially with a liquid (F),

    - at least one light source (4), by means of which light (S) can be coupled into the light guide (2; 17; 22, 23; 32; 43, 44, 45) and

    - at least one light sensor (7; 7a, 7b) for detecting light coupled out from the light guide,

    and wherein the method has at least the following steps:

    - coupling light (S) into the at least one light guide (2; 17; 22, 23; 32; 43, 44, 45),

    - outcoupling light from the at least one light guide (2; 17; 22, 23; 32; 43, 44, 45) into the at least one light sensor (7; 7a, 7b) and

    - determining at least one status parameter of the liquid (F) in the household appliance (9; 16; 24; 42) by means of the evaluation unit (8) on the basis of measurement data of the at least one light sensor (7; 7a, 7b),

    characterised in that
    a refraction index of the liquid surrounding the light guide (2; 17; 22, 23; 32; 43, 44, 45) is determined as the status parameter.
15. Method according to claim 14, characterised by the further steps,

    - coupling light of various wavelengths of the at least one light source (4) into the at least one light guide (2; 17; 22, 23; 32; 43, 44, 45),

    - detecting light of these various wavelengths with the at least one light sensor (7; 7a, 7b) and

    - establishing the refraction index of the liquid surrounding the light guide (2; 17; 22, 23; 32; 43, 44, 45) with the evaluation unit (8) on the basis of the measurement data for the various wavelengths received by the at least one light sensor (7; 7a, 7b).

Images