DE102014210618A1 - Pressure sensor for a household appliance - Google Patents

Abstract

Pressure sensor (1) for a household appliance (W), comprising a fluid receiving space (R) which is at least partially bounded by a movable wall element (7), which wall element (7) depending on a pressure of a in the fluid receiving space (R) located Fluid (F) bulges outwardly, an elastically deformable return element (11), which presses the wall element (7) in the direction of the fluid receiving space (R), and an outside of the wall element (7) arranged resonant circuit (11, 13) with an inductance, wherein an inductance value depends on a degree of curvature of the wall element (7), wherein the elastic return element (11) represents the inductance, and the inductance value of the elastic return element (11) correlates with its degree of deformation.

Description

The invention relates to a pressure sensor for a domestic appliance, comprising a fluid receiving space, which is at least partially bounded by a movable wall element, which wall element bulges outward in response to a pressure of a fluid in the fluid receiving space, an elastically deformable return element, which the wall element in Direction of the fluid receiving space presses, and a resonant circuit with an inductance, wherein an inductance value of a degree of curvature of the wall element depends. The invention is particularly advantageously applicable to pressure sensors for domestic water-conducting appliances such as laundry care appliances, e.g. Washing machines and / or tumble dryers, dishwashers or small household appliances.

For level measurement of water in a wash tank in washing equipment analog pressure sensors are commonly used today. About a so-called air trap, a hydrostatic pressure is built up according to the level in the wash tank. The pressure sensor is pneumatically connected to this air trap. The applied pressure causes a rubber membrane to deflect in the pressure sensor. At this bendable membrane, a ferrite is attached. This ferrite causes, caused by the bending of the membrane under pressure, a translational movement. The translational movement of the ferrite leads in a coil surrounding it to change an inductance. The inductance is part of an electrical resonant circuit. The electrical resonant circuit is detuned with changing inductance, and consequently a frequency signal proportional to the applied pressure is generated. This signal is used to control the washing process.

DE 20 2005 012 207 U1 discloses a device for pressure display, in particular for washing machines, comprising a support housing, an elastic membrane whose edge is fixed to the housing so as to form with it a chamber of variable volume, in which a fluid pressure is fed in operation, at least one electrical Switch mounted in the housing on the opposite side of the chamber of the chamber and containing a bistable metal blade fixed to the housing and bearing at least one movable contact disposed in at least one of the two positions of the metal sheet with at least one fixed electrical Contact can cooperate, which is attached to the housing; the membrane being connected to the bistable metal sheet of the at least single switch by an intermediary transfer member having at least one pressure arm cooperating with said metal sheet in such a manner that the membrane is capable of triggering the switching of said at least single switch when the pressure in the chamber exceeds a corresponding predetermined value; wherein in the housing on the opposite side with respect to the membrane of the chamber, an analog position transducer is arranged, which includes a fixed part and a corresponding movable means; the transfer member having a further pressure arm coupled to the movable means of the transducer; the arrangement being selected so that, during operation, the transducer is capable of providing a continuous signal indicative of the value of the fluid pressure in the chamber.

DE 11 2009 003 606 T5 discloses a modified inductive pressure sensor for detecting operating parameters of a household electrical appliance, such. As a washing machine or a dryer, which is provided with a relatively movable component with respect to the main body (container or drum) of the type having a rigid housing which receives a deformable membrane, which is sensitive to hydraulic pressure, a core which is made of ferromagnetic material and operatively associated with the diaphragm, and a winding fixed to the housing and operably coupled to the core to form a variable inductance inductor; wherein a mass is received in the housing and in close proximity to the diaphragm which is free to move with respect to the housing in at least one direction corresponding to the axis of the winding.

However, the known pressure sensors are relatively expensive to produce.

It is the object of the present invention to at least partially overcome the disadvantages of the prior art and in particular to provide a simple and inexpensive producible pressure sensor, in particular for household appliances.

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

The object is achieved by a pressure sensor for a domestic appliance, comprising a fluid receiving space which is at least partially bounded by a movable wall element, which wall element bulges outwards in response to a pressure of a fluid located in the fluid receiving space, an elastically deformable return element, which Press wall element in the direction of the fluid receiving space, and a resonant circuit having an inductance, wherein an inductance value depends on a degree of curvature of the wall element, wherein the elastic restoring element represents the inductance, and wherein the inductance value of the elastic restoring element correlates with its degree of deformation.

This inductive pressure sensor results in a significant simplification of the structure. Due to the dual function of the elastic return element, a separate inductance, e.g. be dispensed with a coil with coil carrier, and on the ferrites.

The fluid receiving space serves to receive the fluid whose pressure is to be determined. The fluid may be liquid, gas or a combination thereof, e.g. Steam. The liquid may be water, e.g. Fresh water, condensate water, liquor or wastewater. The fluid may also be gas, in particular air, an air trap, which is at a pressure level corresponding to a pressure of a liquid whose level is to be determined.

The fluid receiving space may, for example, have a fluid connection for connection to an air trap or to a liquid reservoir of the domestic appliance (for example a connecting tube or a connecting piece) whose filling level is to be determined by means of a pressure measurement. The fluid receiving space may in particular have rigid walls except for the movable wall element. It may in particular be a rigid housing with an opening which is covered by the movable wall element.

That the movable wall member buckles or deflects outward depending on the pressure in the fluid receiving space means that it is sensitive to pressure. The higher the (internal) pressure in the fluid containment space, the greater the camber or deflection. A value of camber or deflection may be proportional to the magnitude of the (internal) pressure, at least for typical pressure levels of household appliances. The value of the curvature or deflection may be influenced by at least one mechanical property of the elastic return element, for example by a modulus of elasticity, a restoring force or a spring constant in the direction of movement of the movable wall element. The value of the curvature or deflection may in particular be significantly influenced by a mechanical property of the elastic return element, so that the mechanical, in particular elastic, property of the movable wall element on the value of the curvature or deflection is negligible.

It is a particularly simple, robust and inexpensive implementable development that the movable wall element is a deformable wall element, which is particularly noted at the edge. It may then be particularly elastically deformable under the internal pressure, e.g. through a vault.

It is an embodiment that the movable wall element is an elastically deformable membrane. The membrane may be made of plastic, in particular rubber. The membrane is impermeable to the fluid whose pressure is to be determined. The membrane may in particular be a technical vibration membrane.

The movable wall element may itself be mounted rigidly but displaceably in an alternative development. It may then be deflected by displacement under the internal pressure.

Specifically, correlating the inductance value of the elastic return element with its amount of deformation may mean that a value of deformation or deformation of the elastic return element (e.g., its longitudinal compression and / or torsion) is uniquely attributable to the inductance value. The elastic return element in particular provides at least one defined current path for generating a magnetic field. The elastic return element may in particular consist of electrically conductive material.

The inductance may in particular be a coil.

It is an embodiment that the elastic return element is a spring made of electrically conductive material. Such is due to their winding shape particularly easy to use as a coil and also lightweight, inexpensive and robust. In addition, by means of a spring, a restoring force, an electrical resistance, an induction value range, etc. can be easily set within a wide range. It is a further development that the spring is a metal spring, e.g. made of steel or copper. As an alternative to the metal spring, e.g. a spring made of electrically conductive plastic can be used.

It is still an embodiment that the spring is a deformable by the curvature of the wall element in its longitudinal direction coil spring. The coil spring has a particularly high shape similarity to a conventional coil and is highly linearly deformable and robust. The coil spring may be a helical compression spring or a helical tension spring. However, that is Spring is not limited thereto and may alternatively be, for example, a conical spring or a spiral spring.

It is a further embodiment that the coil spring is seated on a first side of a stiff spring plate and at least partially surrounds a projection or stem of the spring plate. Thus, in a compact manner, a secure fit of the spring is achieved with a well-defined orientation, and thus also a precisely reproducible induction value as a function of a degree of curvature of the movable wall element.

It is yet another embodiment that a second side of the spring plate rests on the movable wall element. The spring plate can then except serve as a support member for the coil spring as a lifting transformer for transmitting in particular a running through the movable wall element translational movement on one end of the coil spring. Thus, the coil spring can be precisely and compactly elongated, in particular compressed, become.

Since the change of the inductance value of the elastic restoring element, in particular of the spring, in particular helical spring, depends only on the degree of deformation, the material of the spring plate can be chosen particularly versatile. It is an embodiment that the spring plate is a non-ferritic spring plate, which allows the provision of a particularly inexpensive and lightweight spring plate. So may the spring plate made of sheet steel or plastic. However, in principle, a ferritic spring plate may be used to cause a particularly strong induction change can. The amount of deformation may be e.g. a longitudinal deformation and / or a torsion of the elastic return element, in particular the spring, comprise. With a change in the deformation measure, the inductance value of the elastic return element also changes.

It is also an embodiment that the spring, in particular metal spring, electrically conductively connected to a circuit board, e.g. is soldered, which circuit board has a parallel to the metal spring in parallel capacitance. This makes it easy to provide a resonant circuit. By means of the resonant circuit, the deformation of the elastic return element and thus the curvature or deflection of the movable wall can be determined particularly easily and accurately. Thus, a resonant frequency of the voice circuit that depends on the inductance value may be determined.

The resonant circuit may be connected to an evaluation circuit, which consists of a characteristic of the resonant circuit, e.g. a frequency signal of the resonant circuit, in particular its resonance frequency or its detuning, the pressure in the fluid receiving space and / or a level of a connected to the fluid receiving chamber vessel of the household appliance determined. By changing the inductance so a resonant circuit can be detuned and a proportional signal to the internal pressure and thus to a level can be generated. It is an embodiment that the circuit board has an evaluation circuit for determining a pressure in the fluid receiving space from a frequency signal of the resonant circuit. The resonant circuit is disposed outside of the fluid-excluding space. The evaluation circuit may be e.g. a microcontroller or similar exhibit.

It is a development that the capacitor of the resonant circuit already be integrated into the evaluation circuit. To evaluate the coil signals then only the coil needs to be connected to the evaluation circuit.

It is still a development that the evaluation circuit (for example, its microcontroller or the like) is adjustable, for example, via an adaptation of software parameters is variable, e.g. for pressure evaluation and / or correlation of the pressure with a level.

For a compact and simple construction, at least one capacitance, in particular a capacitor, and the evaluation circuit may be arranged on a common printed circuit board. The elastic return element is preferably electrically connected to the circuit board, e.g. Soldered over two flexible cables or wires.

The object is also achieved by a household appliance having at least one pressure sensor as described above. The household appliance can be designed analogously to the pressure sensor and has the same advantages

It is an embodiment that the household appliance is a laundry care appliance. The pressure sensor is particularly useful here, since an effective operation of a laundry care device typically depends on a fill level determination that can be carried out by means of the pressure sensor.

It is an embodiment that the laundry care device is a washing device, for example a washing machine or a washer-dryer. In a washing machine, an effective, in particular water-saving operation, depends considerably on a precise knowledge of a level of water, in particular with additives as lye (also referred to as "free liquor"), in a drum container. For a washer-dryer, for example, a note may be appreciated a level of condensate water in a floor box for device control be useful.

In a washing device, the pressure sensor may in particular be hydraulically coupled to a free-float receiving area, e.g. with a bottom portion of a drum container. This may be done directly by e.g. Liquid whose level is to be determined, the fluid receiving space fills. The coupling may also be indirect, e.g. via an air trap, by means of which the fluid receiving space with gas, e.g. Air is filled, which is at least about the same pressure level as the liquid. The gas and the liquid may be e.g. be separated by an elastic membrane.

The pressure sensor may be coupled to a control device of the household appliance for data transmission, which control device then determines the data determined by the pressure sensor for controlling a process sequence, e.g. a washing process, can use.

An evaluation device, e.g. for calculating a pressure or a level on the basis of the measurement signals present at the pressure sensor, may be integrated in the pressure sensor or be present elsewhere in the household appliance, for example by functional integration in a central control circuit. This evaluation may be e.g. based on at least one characteristic (for example, a measurement signal / pressure characteristic, a pressure / level characteristic and / or a measurement signal / level characteristic) or by means of an analytical calculation (for example, using a formula or a formula system).

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment which will be described in detail in conjunction with the drawings.

The figure shows an exploded view in an oblique view of a pressure sensor 1 a washing machine W.

The pressure sensor 1 has a first housing shell 2 and a second housing shell 3 on, both of which are rigid or rigid and, for example, made of plastic or metal (for example, aluminum). The first housing shell 2 has a connection piece at the front 4 for connection to an air trap (see Fig.) arranged hydraulically coupled to a liquid container (not shown, eg on a bottom region of a drum container), via which air L in the air trap into the first housing shell 2 can get. A pressure of air L is supposed to be through the pressure sensor 1 be determined, from which it can be concluded on a level of the liquid. The first housing shell 2 has inside one on its side wall 5 circumferential step 6 on, as a support for an edge of a membrane 7 (eg made of rubber) is used.

The membrane 7 has a circular disk-like basic shape with a reinforced edge. If the edge of the membrane 7 on the stage 6 rests, is together with the first housing shell 2 one to one opening to the spigot 4 dense receiving space R for the air L formed. The receiving space R is thus through the first housing shell 2 and the membrane 7 limited. When filling the receiving space R with the pressurized air L, the movable inner portion of the membrane bulges 7 elastic to the outside. The membrane 7 thus sensitive to pressure, with a deflection of the membrane 7 is constantly changing with a change of the internal pressure in the fluid accommodating space R. The higher the internal pressure, the more the membrane bulges 7 outward. As the internal pressure decreases, the membrane moves 7 back accordingly.

At the fluid receiving chamber R remote from (outer) side of the membrane 7 lies a stiff spring plate 8th on. This has a disc-shaped foot 9 and one from a front of the foot 9 projecting cylindrical guide portion 10 or stalk up. The back of the foot 9 lies on the movable inner area of the membrane 7 on. The material of the spring plate 8th is basically free and may eg have plastic, aluminum and / or steel sheet. He is chosen non-ferritic here.

On the leadership area 10 of the spring plate 8th is as a resiliently deformable return element a screw (pressure) spring 11 pinned, with one end on the front of the foot 9 seated. The coil spring 11 is longer than the management area 10 , Preferably in all practical value ranges of the internal pressure in the fluid receiving space R. At its other end sits the coil spring 11 in the area of the second housing shell 3 on.

At least when the fluid receiving space R is filled with pressurized air L and the membrane 7 bulges outwards, the coil spring 11 by the position corresponding to the curvature of the spring plate 8th compressed and then exerts a restoring force on the spring plate 8th and the membrane 7 in the direction of the fluid receiving space R from.

In the fluid receiving space R is another screw (pressure) spring 12 , which is much smaller and softer than the coil spring 11 , It serves to invaginate the membrane 7 in the direction of the fluid receiving space R and / or wobbling of the membrane 7 to prevent. It acts on the coil spring 11 opposite.

The coil spring 11 also serves as a coil for a resonant circuit 11 . 13 , Which 11 eg to a capacitor 13 may be electrically connected in parallel. The coil spring 11 like to at their ends over flexible cables 14 with a circuit board 15 be electrically connected, on which also the capacitor 13 is arranged. The coil spring 11 consists of metal, eg copper, and has a known quiescent inductance value in the relaxed state. With changing length and possibly torsion of the coil spring 11 caused by a changing curvature of the membrane 7 , the inductance value also changes. This in turn will make the resonant circuit 11 . 13 detunes and changes its resonant frequency.

The changed resonance frequency can be determined by means of an evaluation circuit 16 determine that also on the circuit board 15 is arranged. From the resonance frequency can be inferred to the pressure of the air L and thus to a level of the liquid. The circuit board 15 , in particular the evaluation circuit 16 may be connected to a control device S (indicated by the arrow) of the washing machine W, so that the washing machine W can control its operation as a function of a level determined in this way. The evaluation circuit 16 may eg be a microcontroller, an ASIC, an FPGA, an IC, etc. For example, it may be customizable or adjustable via software modification.

At a back of the second housing shell 3 There is a screw-threaded opening 17 , in which a (here example headless) screw 18 is rotatable. By adjusting a depth of insertion of the screw 18 can be a position of the resting thereon end of the coil spring 11 adjust, and thus, for example, a quiescent inductance value. In an outer face of the headless screw 18 Leaves a finishing cap 19 deploy.

The inductive pressure sensor 1 results in a significant simplification of the structure. Due to the double function of the coil spring 11 can be dispensed with a separate inductance, for example on a coil with coil carrier, and on a ferrites.

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

So the screw needs 18 not to be "headless". For example, alternatively, a simple headed adjustment screw may be used to calibrate the zero position of the system. Then, for example, the end cap 19 omitted.

Also, the capacitor of the resonant circuit already in the evaluation circuit 16 be integrated. To evaluate the coil signals then only the coil needs to be connected to the evaluation circuit.

Generally, "on", "an", etc. may be taken to mean a singular or a plurality, in particular in the sense of "at least one" or "one or more" etc., unless this is explicitly excluded, e.g. by the expression "exactly one", etc.

Also, a number may include exactly the specified number as well as a usual tolerance range, as long as this is not explicitly excluded.

LIST OF REFERENCE NUMBERS

1

 pressure sensor

2

 first housing shell

3

 second housing shell

4

 spigot

5

 Side wall

6

 step

7

 membrane

8th

 stiff spring plate

9

 disc-shaped foot

10

 guide region

11

 Helical compression spring

12

 Helical compression spring

13

 capacitor

14

 electric wire

15

 circuit board

16

 evaluation

17

 opening

18

 headless screw

19

 end cap

L

 air

R

 Fluid holding chamber

S

 control device

W

 Washing machine

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 202005012207 U1 [0003]
• DE 112009003606 T5 [0004]

Claims (11)

Pressure sensor ( 1 ) for a household appliance (W), comprising - a fluid receiving space (R), which at least partially by a movable wall element ( 7 ), which wall element ( 7 ) bulges outwards as a function of a pressure of a fluid (F) located in the fluid receiving space (R), - an elastically deformable return element ( 11 ), which the wall element ( 7 ) pushes in the direction of the fluid receiving space (R), and - a resonant circuit ( 11 . 13 ) with an inductance, wherein an inductance value of a degree of a curvature of the wall element ( 7 ), characterized in that - the elastic return element ( 11 ) represents the inductance, and - the inductance value of the elastic return element ( 11 ) correlates with its deformation measure. Pressure sensor ( 1 ) according to claim 1, characterized in that the elastic return element is a spring made of electrically conductive material, in particular metal spring ( 11 ) is. Pressure sensor ( 1 ) according to claim 2, characterized in that the spring is a by the curvature of the wall element ( 7 ) at least in its longitudinal direction deformable coil spring ( 11 ). Pressure sensor ( 1 ) according to claim 3, characterized in that the helical spring on a first side of a stiff spring plate ( 8th ) and at least partially a stem ( 10 ) of the spring plate ( 8th ), wherein the second side of the spring plate ( 8th ) on the wall element ( 7 ) rests. Pressure sensor ( 1 ) according to claim 4, characterized in that the spring plate is a non-ferritic spring plate. Pressure sensor ( 1 ) according to one of claims 2 to 5, characterized in that the metal spring ( 11 ) with a printed circuit board ( 15 ) is electrically conductively connected, which circuit board ( 15 ) one to the metal spring ( 11 ) electrically connected capacitance ( 13 ) having. Pressure sensor ( 1 ) according to claim 6, characterized in that the printed circuit board ( 15 ) an evaluation circuit ( 16 ) for determining a pressure in the fluid receiving space (R) from a frequency signal of the resonant circuit ( 11 . 13 ) having. Pressure sensor ( 1 ) according to one of the preceding claims, in which the movable wall element ( 7 ) is a membrane. Domestic appliance (W) with at least one pressure sensor, characterized in that the pressure sensor is a pressure sensor ( 1 ) according to any one of the preceding claims. Domestic appliance (W) according to claim 9, characterized in that the household appliance (W) is a laundry care device. Domestic appliance (W) according to claim 10, characterized in that the laundry care device is a washing device, the pressure sensor ( 1 ) is hydraulically coupled to a receiving area for free liquor and the pressure sensor ( 1 ) is coupled for data transmission with a control device (S).

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