DE102015203744A1 - Water-conducting household appliance with level detection - Google Patents

Abstract

A water-conducting domestic appliance, in particular coffee machine or washing machine or dishwasher, comprising a container for storing a consumable with walls of the container, the walls comprise electrically conductive plates with electrical connections, and an electronics for signal detection, in particular for detecting a level, is further developed, the walls (3) comprise conductive plastic as plates (4).

Description

The invention relates to a water-conducting household appliance, for example a coffee machine, a washing machine or a dishwasher, comprising a container for storing a consumable consumed during operation of the household appliance, with walls of the container, wherein the walls electrically conductive plates with electrical connections to Contacting an electronics include, which serves a signal detection, in particular for detecting a level.

The known structure uses the principle of a capacitive sensor, wherein the container acts as a capacitor. An electrical capacitor basically consists of two closely spaced electrically conductive but electrically isolated plates or electrodes, typically of metal. Between the plates is a dielectric as insulator. The size of the capacitance is basically determined by the size of the plates, the material of the dielectric and the reciprocal of the distance of the electrodes from each other. The capacitance C of the capacitor is greater the larger the area of the opposing plates and the closer the plates are to each other. In addition, the dielectric property of the insulator located between the plates affects the capacitance. When using plastic as an insulator with a relative dielectric constant of 2, the capacity with respect to air doubles as a dielectric insulator. Pure water has a relative dielectric constant of 81, which increases the capacity by a factor of 81.

In the reservoir, a conductive plate acts on the outside of the container wall as a first capacitor plate. The container wall is non-conductive and forms a capacitive dielectric. Typically, there is a conductive liquid inside the container. It wets the container wall from the inside. The wetted surface virtually forms the second capacitor plate. Depending on the level of the container, the wetted surface and thus the second capacitor plate increases or decreases. The size of the wetted container wall is therefore crucial to the resulting capacity. The capacitance of the capacitor is thus a measure of the level in the container.

In the DE 10 2006 043 973 A1 a water-conducting household appliance is described, in particular a household dishwasher, which has a detergent dosing system having a detergent dispenser with a receiving space for receiving at least one cartridge, wherein the cartridge for storing at least one cleaning agent is formed. The storable amount of detergent is greater than the amount required for a rinse cycle. The detergent dosing system has a device for detecting a filling level in the detergent dispenser or a filling level in a cartridge.

The object of the present invention is to provide a water-conducting household appliance, which detects the level of a container as cost-effectively as possible.

This object is achieved by a household appliance having the features of patent claim 1.

In the case of the household appliance mentioned at the beginning, the walls, which essentially consist of an insulating plastic, additionally comprise according to the invention a conductive plastic which forms the plates of a capacitive sensor. The core of the invention is therefore to use as a level sensor, a capacitive sensor, wherein at least one capacitor plate is formed by the conductive plastic material. The dielectric can essentially be formed by the non-conductive material, that is, by the insulating plastic, but possibly also by a non-conductive ingredient of the container. Accordingly, the walls of the container are as good as exclusively made of plastic, namely of conventional electrically insulating plastic on the one hand and of electrically conductive plastic on the other hand. Both plastics can be processed largely the same, so that the container of the invention is cheaper to produce due to the similar material as a comparable container with metallic plates. For a permanent physical connection of the material for the container on the one hand and the material for the plates on the other hand is easier to achieve in the case of the two plastics according to the invention than with two different materials according to the prior art, namely plastic on the one hand and metal on the other. For the same reason, the container according to the invention can be more easily manufactured in one piece or in one piece, for example in film technology or with an injection molding process. This makes it possible to achieve a very cost-effective production method for a two-shell construction of the container.

The container thus basically consists of two different types of plastic, one conductive and one non-conductive. The two types of plastic can be constructed to form the container walls in principle at least two layers. In any case, the nonconductive or insulating plastic assumes the function of the insulator or of the dielectric. Are the plates in the walls formed only part of the area, need the Walls of the container also to be performed in sections only in two layers.

Typical state-of-the-art capacitive sensors typically use metal plates disposed on both sides of a plastic container. In the case that the metal plates are stationary mounted on the device side and the container which forms the insulator, can be removed, there is usually an air gap between the metal plates and the insulator. It may vary as a result of deformation of the container depending on its degree of filling. Due to the irregular air gap between the metal plate and the container wall, however, the electrical capacitance of the sensor is affected. Temperature differences, the filling state and deformations of the container as a result or vibrations of the device can affect the air gap and disturb the measurement signal. The advantage of the invention, however, is that the air gap and thus at least the aforementioned interference can be completely eliminated. The inventively constructed sensor is therefore very precise. The high accuracy even makes it possible to replace a separate flow rate measurement with the evaluation of the signals of the sensor according to the invention.

The integration of the plates in the walls of the container has the further advantage that the sensor for the customer is no longer recognizable. He is therefore protected by conscious or unconscious manipulations. With the material combination according to the invention in the context of a two-component component, the container also offers greater designerische freedom, since the production and processing options of plastics are very diverse and not otherwise limited by otherwise or required by the prior art metal plates. Even irregular container shapes are very easy to implement.

According to an advantageous embodiment of the invention, the container may be at least partially translucent or transparent. Transparent insulating plastic as a material of a reservoir itself is known. The use of translucent conductive plastic on the other hand offers the freedom of design to make the reservoir translucent or transparent at any and useful for the user section to make him a level recognizable. Conductive plastic, which is not transparent per se, for example, can be emaciated to the film thickness, whereby it may also already appear translucent or largely transparent. Transparent non-conductive plastic can be designed significantly thicker according to the design requirements. Again, inexpensive manufacturing processes such as casting, injection molding or deep drawing of a container or inner container, lamination with conductive plastic or molding are possible. Conversely, the conductive plastic can serve as a supporting material and the insulating plastic are emaciated to the film thickness. This can increase the electrically effective sensor capacity.

According to a further advantageous embodiment of the invention, the walls of the container may comprise a total or in some areas more than two layers, namely be constructed in three or more layers. For example, the walls of the container may consist of two layers of insulating plastic, which include a layer of the conductive plastic as plates of the capacitor. The outer layer of insulating plastic can insulate the container to the outside to shield it from electrical interference, such as contact with the user, which would affect the capacitance of the sensor. For the most part, the soil can for example be single-layered and, for example, consist exclusively of insulating plastic.

A fourth, namely conductive layer can be present according to a further advantageous embodiment of the invention as the outermost layer and connected to a device-side ground. For this purpose, the wall of the container may be coated for example by metallic vapor deposition or by an additional outer layer of conductive plastic. Provided with a contact to the "earth" of the device, it can serve as electrical shielding and further improve the measurement quality.

In principle, the reservoir can be a removable fluid container. With coffee machines, the preparation water can be conveniently poured into the faucet and transported to the appliance if the coffee machine does not have a permanent water connection.

According to an alternative embodiment of the invention, the reservoir according to the invention may be a communicating with a removable liquid container riser. Not the removable liquid container thus comprises the sensor device according to the invention, but the riser. The sensor device can thus be arranged stationary. The removable liquid container can therefore be designed very simply and inexpensively, as is conventional, and in particular requires no contacting with the domestic appliance. In combination with a transparent or translucent water tank, which shows the user the water level, the riser pipe needs not be visible and therefore can be designed arbitrarily. Alternatively, for example, the riser may use a thin translucent or transparent conductive plastic to indicate a level of fluid. Then, the reservoir can be arranged concealed so far, because the riser as communicating with the liquid container tube provides the level information.

Regular use of containers of the type described above as a liquid container. The most frequently occurring substances are therefore to be stored and measured, such as, for example, liquid detergents, descaling agents, rinse aid or preparation water. However, according to an alternative embodiment of the invention, the container may also be a powder container. If the enclosed filling medium is not conductive, densely packed and its dielectric constant is different from air, the capacitive measuring method will work as well. Because with the change in the filling volume, the electrical capacity changes even with powder. Thus, levels of solid but powdery substances such as detergents or descaling agents can be measured according to the invention.

Regularly has the reservoir, which also acts as a capacitive sensor, no direct electrical contact with the liquid, so it is formed electrically non-contact. This is also possible with the invention. The liquid as a container contents is completely surrounded by the insulating plastic within the container. This simple construction is inexpensive, hygienic and reliable. The container comprises two capacitors, for example a right-side and a left-side capacitor, which, as is known, each consist of a conductive plate, the insulating layer and the conductive liquid wetting the insulating layer. The two capacitors are electrically connected by the conductive liquid. The sensor capacitance results from the series connection of two individual capacitances, namely those formed between the first plate and the liquid (or possibly a suitable powder) on the one hand and the one formed between the second plate and the liquid on the other hand. With the variable level within the container also changes that surface of the capacitor plates, which are in contact via the liquid.

This arrangement also works with non-conductive liquids or powdery solids. Then, the consumable is yet another capacitor connected in series or in series, the capacitance of which is formed by the area of the respective contacted wall surfaces. The distance between the wall surfaces and the dielectric property of the filler determine the additional capacity.

According to an alternative embodiment of the container according to the invention for a conductive liquid, the container may be formed electrically contacted with respect to the liquid, so it may have a direct electrical contact to the liquid. It may be formed by a preferably relatively small contact made of conductive plastic or another conductive material. According to the invention it then suffices that the container advantageously comprises only one plate isolated from the interior, which preferably extends over the entire region of the walls. The second "plate" necessary for a condenser now forms the entire surface of the wall wetted by the conductive liquid. In comparison with the first mentioned embodiment, this alternative is not a series connection of two capacitors but a single capacitor whose plate area is approximately twice as large. Nominally quadruples the electrical measuring capacity compared to the upper variant.

According to a further advantageous embodiment of all the above variants of the container can have more, even several electrically isolated from each other plates which are contacted separately. Several plates arranged parallel next to one another in relation to the filling height direction can produce capacitive sensors operating in parallel in the container, which serve to detect the same filling level. They allow a higher reliability of detection by redundant measurements, such as in steam-generating devices, eg. As a steam iron, is advantageous. You can define different measuring ranges, if necessary with different sensitivities. They can thus represent separate sensor elements. As a result, higher reliability can be achieved or more complex evaluation methods can be made possible. With different plate shapes of parallel plates also a differential measurement is possible, so that when filled with substances of different properties of the level can still be measured identically.

According to an alternative advantageous embodiment, the plates can be arranged one above the other in the filling height direction and contacted separately. This results in a clearer delineation of different Füllhöhenbereiche. For example, a 2-, 3- or 4-stage, ie generally a multi-stage sensor for stepped measurements can be created and used as a replacement for multi-stage reed switches.

According to a further advantageous embodiment of the invention, the household appliance with be equipped with electronics for signal detection, wherein the electronics detects one or more signal (s) that can be removed via the contacting of the plates of the container or the direct contact with the contents. The signals can be supplied to a digital signal processing and processed according to the requirements of the household appliance. For geometrically more complex shapes of the container, the signals can be adjusted for example by software so that the output signal of the electronics is proportional to the level of fill. An output signal can also be output in proportion to the change in the fill level and thus provide information on the flow rate. Output signals of the electronics can be of a digital type which signal predetermined fill levels when they are exceeded or undershot and thus replace the previous signals with reed switches or other float switch systems.

The principle of the invention will be explained in more detail below with reference to a drawing by way of example. In the drawing show:

1 : a section through a container with capacitive level sensor without direct electrical contact to the liquid,

2 : A section through a container with capacitive level sensor with direct electrical contact to the liquid.

1 shows a section through a cubic container 1 for holding a supply of water 2 for a coffee machine, not shown. The container 1 consists of four vertical walls 3 , which are multi-layered, and a horizontal floor 12 , which is also multi-layered. Two opposite walls 3 as well as the ground 12 are shown in section. In the ground 12 There are two connections 9 coming from a bottom of the container 1 from via electrical lines 17 with an evaluation electronics 10 of the coffee machine are connected.

The multilayered walls 3 have an inner layer 6 and an outer layer 8th , which consist of conventional per se plastic, which is electrically non-conductive or insulating. In between there is a middle layer 7 from an electrically conductive plastic, which assumes the function of a capacitor plate according to the invention and hereinafter referred to as a plate 4 referred to as. The plate 4 is thus electrically both through the outer layer 8th from the environment as well as the contents of the container 1 , the water 2 , through the inner layer 6 isolated.

In fact, the container is 1 - Viewed electrically - in the direction of view in a left half 13a and a right half 13b divided. Because it includes two separated plates 4 passing through an insulator strip 14 are electrically isolated from each other. On the ground 12 runs the insulator strip 14 in the direction of view, ie perpendicular to the plane of the drawing. In the parallel to the drawing plane extending and therefore not shown other walls of the container 1 it runs between the plates mutatis mutandis 4 the left half 13a and the right half 13b of the container 1 ,

From the soil 12 of the container 1 Join the connections 9 right and left of the insulator strip 14 downwards. They represent the respective electrical connection of the plates 4 the left half 13a and the right half 13b via two touch contacts to the electrical lines 17 forth to the transmitter 10 to lead. The two connections 9 are located largely in the middle of the ground 12 and are separated only by the electrically insulating plastic 7 of the insulator strip 14 separated. From the water 2 they are through the inner layer 6 of the soil 12 electrically isolated.

The container 1 poses with the two plates 4 and the associated connections 9 a total of a two-pole electric capacitor, which consists of series-connected, electrically effective areas and its capacity by the filling level of the water 2 is changed. Two essential areas are those of the water 2 wetted insulating surfaces of the left half 13a and the right half 13b of the container 1 , These two capacitive areas can be considered as separate effective capacitors. You are in conductive accepted water 2 directly connected in series. The first electrical capacity is determined by the extent of the water 2 wetted surface of the inner layer 6 determines, under which the electrically conductive middle layer 7 ie the plate 4 the left half 13a located. The thickness of the inner layer 6 and the dielectric property of their insulating plastic determine the fundamental capacity of the first left-hand capacitor.

The water 2 wetted area of the right half 13b with the local extent, the thickness and the corresponding dielectric property of the layer 6 determines the capacitance of the second right-hand capacitor of the right half 13b , Overall, the series circuit of the capacitors represents the left half 13a and the right half 13b the total capacity of the level sensor

As the wetted surfaces of the walls 3 with the level in the container 1 change is also the total capacity of the series connection a direct measure of the level in the container 1 , If the capacity change is detected, a measure of the inflow or outflow from the container is obtained 1 ,

The container 1 is a plastic part of two components, which can be easily produced by injection molding. Because of the material similarity of the conventional and the conductive plastic, they can be combined well with each other.

For non-conductive assumed water 2 put that with the water 2 filled space between the right half 13a and the left half 13b another in series capacitor (see above). The dielectric property of the water 2 with its very high dielectric constant is particularly advantageous. The capacitance of this capacitor is also determined by the distance between the right and left walls 3 and the size of the wetted right and left surface of the wall 3 certainly. In this embodiment, the container 1 Also suitable for level measurement of non-conductive powders.

Is the container for level measurement of water 2 For example, it is advantageous to use the thickness of the inner layer 6 less than 0.5 mm, preferably even less than 0.1 mm. This significantly increases the available measuring capacity and significantly improves the measurement quality. The thickness of the plates 4 From the electrically conductive plastic is preferably also 0.1 to 0.5 mm. The outer layer 8th is preferably 0.5 to 2.5 mm thick and is essentially for the mechanical stability of the container 1 responsible. The two connections 9 are also made of electrically conductive plastic and form with the respective plate 4 a composite. If the container 1 should not be designed to be removable, the lines 17 to the transmitter 10 in the connections 9 be pressed or poured.

2 shows a second embodiment of the container 1 that of conductive water 2 as a consumer good in the container 1 emanates. The walls 3 are identically constructed as in 1 , The difference lies in the area of the soil 12 between the connections 9 , Here is the water 2 between the connections 9 about an additional plug 16 Made of conductive plastic and a connection 11 directly with the evaluation electronics 10 electrically connected. The stopper 16 is from the connections 9 through the insulator strip 14 electrically isolated on all sides. The connections 9 the plates 4 the left half 13a and the right half 13b however, are also different from 1 outside the container 1 electrically at the connection point 15 contacted each other and then together with the transmitter 10 connected. Advantageously, the two plates 4 in the walls 3 also directly contiguous from the electrically conductive plastic. The insulating strip 14 must in this case the plates 4 no longer isolate each other, it is only for the isolation of the plug 16 on the ground 12 necessary.

Compared to the embodiment 1 sets the capacity between the connected terminals 9 and the connection 11 now a parallel connection of the capacitors of the left half 13a and the right half 13b dar: The plates 4 are over the connection 9 connected in parallel with the second "capacitor plate", the water 2 that over the layer 6 as a dielectric from the plates 4 is disconnected.

If the capacitors the right half 13b and the left half 13a are equal to halves in series according to 1 usually the total capacity (Cges = ½C), in parallel according to 2 However, the individual capacities add up (Cges = 2C). The parallel connection of 2 is thus compared with the series circuit of 1 approximately four times larger.

Since the foregoing containers, described in detail, are embodiments, they may be modified in the usual way by those skilled in the art to a great extent without departing from the scope of the invention. In particular, the concrete embodiments of the container can also take place in a different form than that described here, for example in a cylindrical one. Likewise, the container can be configured in another form, if this is necessary for reasons of space or designerischen reasons. The use of the indefinite article "a" or "an" does not preclude the fact that the characteristics in question can also be present several times or more than once.

LIST OF REFERENCE NUMBERS

1

 container

2

 water

3

 wall

4

 plate

5

 ground

6

 inner layer

7

 middle layer

8th

 outer layer

9

 connection

10

 evaluation

11

 direct connection

12

 ground

13a

 left half

13b

 right half

14

 insulator strip

15

 junction

16

 Graft

17

 electric lines

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102006043973 A1 [0004]

Claims (10)

Water-conducting household appliance, in particular coffee machine or washing machine or dishwasher, comprising a container for storing a consumable with walls of the container, the walls comprise electrically conductive plates with electrical connections, and electronics for signal detection, in particular for detecting a level, characterized in that the Walls ( 3 ) conductive plastic as plates ( 4 ). Domestic appliance according to claim 1, characterized in that the container ( 1 ) is at least partially opaque, partly transparent which is completely transparent. Domestic appliance according to claim 1 or 2, characterized in that the walls ( 3 ) of the container ( 1 ) are made up of more than two layers. Domestic appliance according to one of the above claims, characterized in that the walls ( 3 ) of the container ( 1 ) comprise an additional shielding layer of conductive material. Domestic appliance according to one of the above claims, characterized in that the container ( 1 ) is a riser communicating with a removable liquid container. Domestic appliance according to one of claims 1 to 4, characterized in that the container ( 1 ) is a powder container. Domestic appliance according to one of claims 1 to 5, characterized in that the container ( 1 ) no direct electrical contact to the liquid ( 2 ). Domestic appliance according to one of claims 1 to 5, characterized in that the container ( 1 ) a direct electrical contact to the liquid ( 2 ). Domestic appliance according to one of the above claims, characterized in that the container ( 1 ) several plates ( 4 ), which in the filling height direction of the container ( 1 ) are arranged one above the other. Domestic appliance according to one of claims 1 to 8, characterized in that the container ( 1 ) several plates ( 4 ), which with respect to the filling height direction of the container ( 1 ) are arranged parallel to each other.

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