Laundry treatment machine with capacitive humidity sensor module

Abstract

The invention provides a laundry treatment machine (2), in particular a washing machine, a dryer or a washer-dryer, comprising: a cabinet (5), a laundry treatment drum (4) arranged within the cabinet (5), a door (8) for closing an opening (9) for loading laundry (6) to be treated into the drum (4), and a humidity sensor module (24, 24a) for estimating the humidity of the laundry contained within the drum (4), the humidity sensor module (24, 24a) comprising: a main electrode (14) arranged at the door (8), a secondary electrode (16, 17) arranged at the door (8), and a control unit (18). The control unit (18) is connected to the main and secondary electrodes (14, 16) and is configured for transmitting signals to and / or receiving signals from the main and secondary electrodes (14, 16), and wherein the secondary electrode (16, 17) at least partially surrounds the periphery of the main electrode (14).

Description

[0001] Laundry treatment machine with capacitive humidity sensor module

[0002] The present invention relates to a laundry treatment machine, in particular a washing machine, a dryer or a washer-dryer.

[0003] Systems for measuring the humidity of laundry in laundry treating machines like tumble dryers or washer-dryers based on the measurement of the dielectric properties of items in the drum, the so-called “capacitive sensing” are generally known. The working principle of such sensing system is based on the fact that the laundry in the drum has dielectric properties, and it behaves like a dielectric material placed between plates of a capacitor, thus inducing some change in the detected capacitance. The capacitance change can be detected and correlated to dielectric properties of items in the drum, making it possible to estimate the water content in the laundry.

[0004] To be able to sense the dielectric properties of the laundry, a system for capacitive sensing requires an electric field in the drum, whose field lines cross the laundry. The electric field is generated by applying a voltage to electrodes that can be arranged outside the drum, wherein the drum and / or the cabinet form a counter-electrode due to the fact that they are electrically conductive. Humidity content of the laundry is estimated based on the capacity measured between electrodes and drum or cabinet.

[0005] EP 1 413 664 Al discloses a method and a system for measuring the humidity of the laundry contained in washing-machines, which is based on the measurement of the variations of the electric permittivity or dielectric constant of the laundry during the drying program and on the conversion of this permittivity, by means of a suitable control device, into a quantity, for example a voltage or a frequency, which depends on the humidity of the laundry.

[0006] DE 102018 113 485 Al discloses a dryer having a drum and a residual humidity capacitive measuring system for measuring the humidity of the laundry contained within the drum, wherein the residual humidity measuring system comprises a first electrode arranged at the door and a second electrode formed by the drum.

[0007] It is an object of the invention to provide a laundry treatment machine, in particular a washing machine, a dryer or a washer-dryer, with an improved drying efficiency. In particular, it is an object of the invention to provide a laundry treatment machine with an improved humidity detection by means of an improved humidity capacitive sensor.

[0008] The invention is defined in the independent claim. Particular embodiments are set out in the dependent claims.

[0009] According to claim 1, a laundry treatment machine, in particular a washing machine, a dryer or a washer-dryer, is provided. The laundry treatment machine comprises a cabinet, a laundry treatment drum arranged within the cabinet, a door for closing an opening (e.g. a loading opening) for loading laundry (e.g. clothes) to be treated into the drum, and a humidity sensor module for estimating the humidity of the laundry contained within the drum. The humidity sensor module comprises: a main electrode arranged at the door, a secondary electrode arranged at the door, and a control unit connected to the main and secondary electrodes and being configured for transmitting signals to and / or receiving signals from the main and secondary electrodes. The main electrode and the secondary electrode are electrically insulated from each other. The secondary electrode at least partially surrounds the periphery (i.e. an outer rim / edge) of the main electrode (i.e. the secondary electrode is at least partially arranged along the outer edge / rim of the main electrode).

[0010] The main and secondary electrode can be understood as the basis element of the humidity capacitive sensor of the invention.

[0011] The control unit is preferably configured for applying a voltage to the main and the secondary electrode, for receiving signals from the main and secondary electrodes and for determining, based on the received signals, a capacitance between the main electrode and a reference element of the laundry machine acting as a counter-electrode, for example the drum or the cabinet, and / or the capacitance between the secondary electrode and the reference element.

[0012] Preferably, the control unit is configured for applying the same voltage to the main electrode and the secondary electrode, whereas the reference element has a different reference voltage. For example, the reference voltage of the reference element such as the drum and / or the cabinet acting as a counter-electrode can be zero if the drum and / or the cabinet are connected to ground or common voltage (which is different to the reference voltage).

[0013] Alternatively, the control unit may be configured for applying a first voltage to the main electrode and a second voltage to the secondary electrode, wherein the first voltage is different from the second voltage (and preferably both are different to the reference voltage). The conductive drum is preferably electrically connected to the control unit. Preferably, the electrical connection between the drum and the control unit is implemented by the use of a brush or a plurality of brushes. The brush is preferably placed along the smallest possible drum diameter, i.e. near a rear flange area of the drum. Alternatively, other conductive components suitable to be connected to the drum, like for example a metallic ball bearing, can be used.

[0014] In particular, the control unit may be configured for determining from the signal from the main and secondary electrodes the dielectric constants between each of the main and secondary electrodes and the reference element acting as the counter-electrode.

[0015] Based on the determined dielectric constants the control unit is configured to estimate a humidity of laundry within the laundry treatment machine.

[0016] The control unit may be connected to a main controller of the laundry treatment machine for supplying a supply voltage to the control unit and / or to transmit and receive control signals between the main controller of the laundry treatment machine and the control unit. In particular, the control unit transmits a control signal indicating the humidity of the laundry contained in the drum to the main controller and the main controller may adjust the drying cycle based on the signal transmitted by the control unit.

[0017] By arranging the secondary electrode around the main electrode so that it at least partially surrounds the periphery (i.e. an outer rim / edge) of the main electrode, wherein the secondary electrode and the main electrode are electrically isolated from each other, the field lines of the electric field originating from a front surface (i.e. surface facing towards the drum) of the excited main electrode are 'focused' into the central region of the drum, while the field lines of the electric field originating from the front surface (i.e. surface facing towards the drum) of the excited secondary electrode are deflected to the lateral front area of the drum. In particular, the secondary electrode is placed at a shorter distance to the metallic surface of the drum in comparison to the distance of the main electrode from the metallic surface of the drum (when seen in projection to the plane of the main electrode and when starting from the center of the main electrode towards the peripheral drum walls in projection). Thus, the electric field lines of the secondary electrode have a relatively short pathway to the surface of the drum. Electric field lines originating from the main electrode are forced to reach the inner metallic surface of the drum along some longer pathway compared to field lines starting from secondary electrode. In particular, the field lines starting from the main electrode are deviated in their trajectory towards the center and back region of the drum by the existence of the field lines generated by the secondary electrode. As the majority of the laundry tumbling in the rotating drum is in the center region as compared to the laundry amount at the front lateral side of the drum, the electric field lines originating from the main electrode go through some greater volume of wet laundry (e.g. clothes), thus sampling a wider amount of clothes load.

[0018] Preferably, the voltages applied to the main and secondary electrodes are such that the electric field lines generated by the main electrode all or essentially all pass through the central region of the drum towards the rear lateral surface and back surface of the drum, and such that the electric field lines of the secondary electrode all or essentially all pass through the front and lateral (or peripheral) region of the drum towards the front lateral surface of the drum (or tub).

[0019] Therefore, by arranging the secondary electrode around the main electrode so that it at least partially surrounds the periphery (i.e. an outer rim / edge) of the main electrode, the main electrode is able to detect a first capacity towards the center and back volume of the drum, whereas secondary electrode is able to detect a second capacity towards the lateral front area of the drum.

[0020] Due to the arrangement of the main and secondary electrodes, the electric field lines starting from the main electrode goes or pass through some greater volume of wet laundry (i.e. the pathway / length of the field lines from the main electrode crossing the wet laundry is increased). Thus, a wider amount of laundry load is sampled.

[0021] Preferably, the signal from the main electrode is used as the main reference for the humidity estimation of the clothes within the drum. More preferably, the signal from the main and the secondary electrode are used as the main reference for the humidity estimation of the clothes within the drum. Thus, the estimation of humidity of the laundry based on the capacity detected by the main electrode or the capacities detected by the main and the secondary electrode is more accurate and the drying efficiency is thus improved.

[0022] For example, above mentioned DE 10 2018 113 485 Al suggests the use of a plurality of electrodes arranged adjacent to each other at the circumference of the door. Thus, the field lines produced by each electrode are directed towards the lateral side of the drum. Due to the positioning of the electrodes, the field lines produced by the electrodes at the door do not achieve the above effect of directing the filed lines of an electrode towards the center of the drum as in the above laundry treatment machine.

[0023] Based on the more accurate humidity estimation, the drying time estimation since the beginning of the drying cycle is improved. Further, the time-to-end update of a drying cycle is improved through the drying cycle. The detection of wet-spots within the laundry, e.g. in mixed loads, is improved as the electric field lines are focused into the central region of the drum where most of the wet laundry is located. Further, the automatic drying cycle is more accurate, thus possible better rating by customer magazine.

[0024] Preferably, the door comprises a door chamber formed by a door main body made of non- conductive material, for example electrically insulating glass. The door main body may comprise or is the glass wall of the door. Further the door main body may comprise a wall facing towards an interior of the drum (e.g. the glass wall) and a front side screen. Preferably, the main and secondary electrodes are arranged within the door chamber. In particular, the main and secondary electrodes are arranged at a position of the door, in particular within the door chamber, such that exclusively or mainly only the non-conductive material (i.e. the wall facing towards the interior of the drum such as the glass wall) is arranged between the main and secondary electrodes and the inner space of the drum.

[0025] The front side screen of the door may be made of a plastic material. The front side screen may form an outer surface of the door. The front side screen may be arranged on a surface of the glass wall facing away from the interior of the drum.

[0026] 'Main electrode arranged at the door' may mean that at least the main electrode is attached to a glass wall of the door. This is preferably used when the laundry treatment machine comprises a door with a flat glass wall. 'Main electrode arranged at the door' may also mean that at least the main electrode is very close but not directly attached to the glass wall of the door (i.e. a gap between the main electrode and the glass wall of the door is provided).

[0027] Preferably, the secondary electrode covers at least partially the rear surface of the main electrode. More preferably, the secondary electrode fully encloses the main electrode at the lateral side (periphery) and the rear surface of the main electrode. Alternatively, the entire secondary electrode extends in the same plane as the main electrode and preferably the secondary electrode surrounds the main electrode all around the outer edge.

[0028] A 'rear' surface of the main electrode and / or the secondary electrode may be the surface opposite of the electrode's surface ('front' surface), wherein the front surface is facing towards the wall of the door main body facing towards the interior of the drum (in particular towards the glass wall of the door) and / or which is facing towards the cabinet's interior, specifically towards the inner of the drum. The 'rear' surface of the main electrode and / or the secondary electrode is preferably the surface facing away from the drum. Covering the rear surface of the main electrode may include that a support element, like a support substrate (see below) is arranged between the rear surface of the main electrode and the front surface of the secondary electrode (i.e. covering does not mean that the secondary electrode is directly attached to the rear surface of the main electrode, but an insulator and / or an air gap are provided between). The front surface of the main electrode and / or the secondary surface may be the sensing surface of the humidity sensor and / or the rear surface of the main electrode and / or the secondary electrode may be the non-sensing surface of the humidity sensor. Preferably and specifically the front surface of the main electrode serves as a sensing surface and optionally the secondary electrode serves for reference and / or calibration sensing with respect to the signal from the main electrode.

[0029] The 'periphery' of the main electrode is preferably the area around the circumference or lateral / outer edge or rim of the main electrode. The lateral / outer edge may be the edge or surface between the front and rear surface or the edge or surface connecting the front and rear surface of the main electrode.

[0030] Preferably, the main electrode forms an inner electrode and the secondary electrode forms an outer electrode with respect to the mutual spatial location of the main and secondary electrodes. Inner location of the main electrode and outer location of the secondary electrode may relate, respectively, to a mutual location with respect to a plane of the main electrode and / or may relate to a mutual location with respect to the laundry treatment machine cabinet where the second (outer) electrode is positioned towards the outside of the laundry treatment machine cabinet, and the main (inner) electrode is positioned towards the interior of the laundry treatment machine cabinet.

[0031] Preferably the secondary electrode surrounds (encompasses) the main electrode all around the (lateral) periphery or along 50% to 90% or 60% to 100% of the periphery (circumference) of the main electrode. Preferably the secondary electrode covers all or 50% to 90% or 60% to 100% of the outer (rear) surface (in particular backside, i.e. 'rear surface' of the main electrode facing away from the drum) of the main electrode.

[0032] Preferably, the main electrode is dimensioned so that its surface is as big as possible depending on the shape and on the available space of the glass wall of the loading door.

[0033] Preferably the secondary electrode is dimensioned so that its surface is comprised in a range of 10% -200%, 20-40%, 30-50%, 100-120%, 110-150% of the surface of the main electrode.

[0034] Preferably, the main and the secondary electrodes are coplanar or partially coplanar. Preferably, the main and the secondary electrodes are coplanar and are arranged parallel to the surface of the glass. Preferably the secondary electrode in the region surrounding the periphery of the main electrode is coplanar to the main electrode. Alternatively, the main and the secondary electrodes may be not coplanar and do not lie on the same plane. The main electrode may be arranged in a first plane and the secondary electrode in a second plane, wherein the first and second planes are distanced from each other and more preferably are parallel to each other. In particular, the front surfaces of the main and secondary electrodes may be arranged in different planes being distanced to each other. For example, the main electrode may be arranged closer to the glass wall of the door than the secondary electrode, or vice versa. Preferably the secondary electrode in the region surrounding the periphery of the main electrode is coplanar to the main electrode and the secondary electrode in the region covering the rear surface of the main electrode is spaced from the plane of the main electrode, preferably parallel spaced to the main electrode.

[0035] The main electrode may be arranged at the door and the secondary electrode may be arranged at (or at least partially behind) the main electrode (in particular on a side of the main electrode facing away from the drum) such that the field lines of the main electrode towards the drum are mainly or all passing through the central region of the drum and the field lines of the secondary electrode towards the drum are mainly passing through the front and lateral area of the drum. Thus, the electric field lines starting from the main electrode goes through some greater volume of wet clothes, thus sampling a wider amount of clothes load. In a case in which a portion of the secondary electrode at least partially covers the rear surface of the main electrode, the portion of the secondary electrode may act as a shielding element configured to deflect electric field lines originating from the main and secondary electrodes towards the interior of the drum. Thus, the effect of directing the field lines of the main electrode towards the drum is further improved.

[0036] To further improve the effect of directing the field lines of the main and of the secondary electrode, the laundry treatment machine further comprises a shield electrode arranged at the door, in particular within the door chamber, which is configured to deflect / redirect the electric field lines originating from the back side of the main and secondary electrodes towards, respectively, the center and the lateral front area of the drum.

[0037] The shield electrode may be connected to the control unit which is preferably configured for applying to the shield electrode the same voltage applied to the main and the secondary electrode. The control unit may be configured for receiving signals from the shield electrode and for determining, based on the received signals, a capacitance between the shield electrode and the reference element of the laundry machine acting as the counter-electrode, for example the drum or the cabinet. Alternatively, the shield electrode is connected to the control unit which is configured for applying to the shield electrode a voltage which is different than the voltage applied to the main and the secondary electrode.

[0038] Preferably, the capacitance between the shield electrode and the reference element of the laundry machine acting as the counter-electrode, for example the drum or the cabinet is not used by the control unit for estimating the humidity of the laundry.

[0039] Alternatively, the capacitance between the shield electrode and the reference element (e.g. the drum or the cabinet) is also used in addition to the capacitance of the main and the secondary electrode for estimating the humidity of the laundry within the drum.

[0040] Alternatively, the shield electrode may be used only for deflecting / redirecting the electric field lines originating from the back side of the main and secondary electrodes towards the interior of the drum, whereas the control unit does not determine the capacitance between the shield electrode and the reference element.

[0041] The shield electrode may prevent the main and secondary electrodes from being influenced from events happening in the external environment (i.e. in front of the door of the laundry treatment machine) such as for example when a user is passing in front of the laundry treatment machine.

[0042] Preferably, the shield electrode is arranged behind the main and the secondary electrode (i.e. at a side facing the rear surfaces of the main and secondary electrodes).

[0043] Preferably, the shield electrode is arranged between the secondary electrode and the front side screen of the door or between the main and the secondary electrode and the front side screen of the door. Preferably, the shield electrode is arranged within the door chamber between the front side screen and the main and secondary electrodes.

[0044] Preferably, the shield electrode is arranged at the door at a side of the secondary electrode which faces away from the glass wall of the door main body (i.e. away from the interior of the drum). The shield electrode may have the same outer shape as the secondary electrode. The shield electrode is preferably congruent with the main and secondary electrodes.

[0045] Preferably the shield electrode and / or the control unit is arranged parallel to the front side screen and / or parallel to the main and / or secondary electrodes. Preferably, the shield electrode and / or the control unit is arranged parallel to the front side screen and the main and / or secondary electrodes are arranged inclined with respect to the front side screen. The shield electrode may be arranged in a different plane than the plane in which the main and secondary electrodes extend (i.e. the shield electrode may be arranged distanced from the electrodes).

[0046] In a further embodiment, the function of the shield electrode may be carried out by the secondary electrode. In this case, only the capacitance between the main electrode and the reference element may be used for estimating the humidity of the laundry, whereas the secondary electrode preferably at least partially covers the back surface of the main electrode.

[0047] Preferably the control unit is an active or passive electronic unit. In case of the passive electronic unit, only passive components are used like resistors, capacitors, voltage dividers and / or inductors. In case of active electronic unit, active components may be used like transistor(s), amplifiers and / or microcontrollers.

[0048] Preferably, the main electrode and / or the secondary electrode is arranged at a first distance from the glass wall of the door. Preferably the distance is in the range of 1,0 - 4 mm, 1,2 - 3,5 mm, 1,5

[0049] - 3 mm, 1,8 - 2,5 mm, preferably at a distance of 2,2 mm. A portion of the secondary electrode which surrounds the periphery of the main electrode (the portion of the secondary electrode which is arranged on a first surface of the support element as explained below) may be arranged at the first distance from the door (i.e. exterior surface of the glass wall of the door). The first distance is preferably to compensate for manufacturing tolerances and in particular in case of a curved door to compensate for the bending of curved external glass surface. It was found that the closer the electrodes are to the external surface of the glass wall of the door, the stronger the signal of the electrodes is affected.

[0050] Alternatively, the first distance may be zero if the main electrode and / or the secondary electrode are directly attached to the glass wall.

[0051] The first distance may be the distance between the front surface of the main electrode and / or the front surface of the secondary electrode and the glass wall, in particular external surface of the glass facing away from the drum interior.

[0052] Preferably, at least a portion of the secondary electrode and / or the portion of the secondary electrode which is covering the rear surface of the main electrode, is arranged at a second distance from the rear surface of the main electrode in the range of 2,0 - 12 mm, 4,0 - 10 mm, 5,0

[0053] - 9 mm, preferably at a distance of 6 mm. A portion of the secondary electrode which covers at least partially the rear surface of the main electrode (and in particular the portion of the secondary electrode which is arranged on a second surface of a support element as explained below) is arranged at the second distance from the main electrode.

[0054] The second distance may be the distance between the rear surface of the main electrode and the secondary electrode, i.e. the portion of the secondary electrode arranged at the rear surface of the main electrode.

[0055] The above distances ensure that the signal from the electrodes is not much affected which results in an accurate and reliable capacity detection and thus humidity estimation of the laundry.

[0056] Preferably, the gap (which results from the distances) between the main electrode and / or secondary electrode and the glass wall of the door and / or the gap between the main electrode and the secondary electrode and / or a gap between the main electrode / secondary electrode and the shield electrode (see below) can be either filled with air or a hollowed and / or plastic element.

[0057] Preferably the first and second electrodes are arranged on a support element (see below) which is configured to support and / or distance or space the main and secondary electrodes from each other (with the distances above). For example, the first electrode and at least a portion of the secondary electrode are arranged on a first surface of the support element (i.e. surface facing the interior of the drum) and at least a portion of the secondary electrode is arranged at a second surface of the support element (i.e. surface facing away from the interior of the drum towards the front side screen) which is opposite to the first surface of the support element. I.e. the support element is provided between the main and secondary electrodes, wherein the support element spaces the electrodes at the first surface of the support element from the portion of the secondary electrode at the second surface of the support element. In this case, the distance between the electrodes which is formed by the support element may be e.g. 12 mm.

[0058] For example the support element forms a hollowed plastic element, and at least a portion of the secondary electrode is arranged on a surface which is opposite to the surface on which the main electrode is arranged.

[0059] Alternatively, the entire main and secondary electrodes are arranged on the first surface of the support element.

[0060] Preferably, an electric insulating element is supported by the support element for electrically separating the main and secondary electrodes from each other. The insulating element is preferably arranged on the first surface of the support element facing towards the interior of the drum. The support element may be further configured to distance or space the main electrode from the door (i.e. the glass wall of the door) and / or to distance or space the shield electrode from the main and / or secondary electrodes.

[0061] The first distance may result from adhesive material or from any kind of spacer like, for example, a deformable rubber element, used to fix the main and / or secondary electrodes to the door (in particular the glass wall of the door) or the support element may comprise distance elements configured to provide the gap between the main electrode and the door (in particular the glass wall of the door).

[0062] The main and secondary electrodes are preferably electrically isolated from each other such as by the electric insulating element as mentioned above. In particular, a gap between the secondary electrode or portion of the secondary electrode surrounding the periphery or outer edge of the main electrode and the outer edge of the main electrode is provided. In particular, a gap is provided at the first surface of the support element between the main electrode and the secondary electrode arranged on the first surface of the support element. Preferably, the gap is in the range between 0.3 mm and 50% of the maximum length of the main electrode. More preferably, the gap is in the range between 0.3 and 40 mm, 0.3 and 20 mm, 0.3 and 10 mm or 0.3 and 5 mm.

[0063] The main electrode and / or secondary electrode may have a thickness in the range of 0,05 - 1,2 mm, 0,4 - 0,9 mm or 0,5- 0,7 mm. However, the thickness of the main and the secondary electrodes is not relevant for measuring the humidity of the laundry.

[0064] Preferably, the front side screen may be at least partially made of a conductive material such as conductive plastic, for example based on metallic meshed or on black carbon loaded plastic. In this case the front side screen may act as a shield electrode so that the conductive material may shield the main and secondary electrodes to the outside of the laundry treatment machine (i.e. configured to deflect field lines originating from the main and secondary electrodes towards the interior of the drum). In this case the conductive material of the front side screen may be electrically connected to the control unit and the control unit is adapted to apply the shield voltage to the conductive material.

[0065] Preferably, the main electrode and the secondary electrode have the same or different outer contours. Preferably, the main electrode and / or the secondary electrode, in particular the outer contour of the secondary electrode has the form of a rectangular, a circle, or the basic form of a semicircle or of a segment of a circle. The main electrode may be arranged at the lower region of the loading door, in particular at the lower region of a user's viewing field of the door. For example, the portion of the secondary electrode which surrounds the periphery of the main electrode may have the form of a semicircle or of a segment of a circle, or a rectangular completely surrounding the entire main electrode. Preferably, the main and secondary electrodes are formed to be adapted to the geometrical shape, i.e. curvature and / inclination of the glass wall of the door.

[0066] Preferably the main electrode does not protrude beyond the secondary electrode. Preferably, the cross section of the secondary electrode has the shape of a "C".

[0067] Preferably separate electrical connections are provided between each of the main and secondary electrodes and the electrically conductive drum or cabinet and the control unit. Preferably, the electrical connection between the control unit and the electrically conductive drum or cabinet and / or an electrical connection between the control unit and a main controller (see below) of the laundry treatment machine is guided through a hinge of the door.

[0068] Preferably, the control unit comprises a signal generating unit configured to generate a temporally varying voltage signal which is supplied via the electrical connection to the main electrode and the secondary electrode as the main voltage.

[0069] Alternatively, the control unit comprises a signal generating unit configured to generate a temporally varying voltage signal which is supplied via the electrical connection to the main electrode as the main voltage and via the electrical connection to the secondary electrode as the secondary voltage. Preferably, the secondary voltage is different from the main voltage such as the frequency or periodicity and / or the amplitude of the secondary voltage differs from the frequency or periodicity and / or the amplitude of the main voltage.

[0070] More preferably, the control unit is configured to apply a main voltage Vm to the main electrode, the secondary electrode and optionally to the shield electrode.

[0071] Alternatively, the control unit is configured to apply a secondary voltage to the secondary electrode and / or the shield electrode.

[0072] Preferably, the main voltage is a pulsed square signal or a sinusoidal signal. Alternatively, voltages with a different waveform can be used.

[0073] The frequency or periodicity of the voltage supplied to the main and / or secondary electrode is in the range of 0,3 - 300 kHz, preferably 100 kHz.

[0074] Preferably, the main voltage has an amplitude in the range of 0 to 10 V, preferably, 0 to 8 V, 0 to 6 V or more preferably 0 to 3 V. Preferably, the main voltage has an amplitude of 1,25 V. Preferably, the control unit comprises a signal detection unit configured to detect a main signal dependent on the capacity between the main electrode and the drum or the cabinet (i.e. the reference element) and / or a secondary signal dependent on the capacity between the secondary electrode and the drum or the cabinet (i.e. the reference element). Based on the detected main and / or secondary signals, a humidity of the clothes within the laundry treatment machine may be estimated. The estimated humidity may be transmitted to a main controller of the laundry treatment machine.

[0075] Preferably, the main electrode and / or the secondary electrode is arranged at a distance from the shield electrode in the range of 0,5 - 40 mm, 1,0 - 10 mm, 6,0. The distance is the distance between the shield electrode and a surface of the main and / or secondary electrode facing the shield electrode. The distance is preferably to insulate the shield electrode from the main and / or secondary electrode to prevent short circuit.

[0076] Preferably, the humidity sensor module (sensor module) is realized as an integrated and / or ready- to-mount module and / or pre-assembled modular component. Thus, the pre-assembled sensor module can be mounted at the door, in particular within the door chamber, and the overall assembly of the sensor module is therefore simplified. Due to the modularity the sensor module may be functionally pre-tested before mounting. Pretesting and pre-calibration of the module is thus simplified. E.g. no mounting of sensor elements like electrodes on the door main body is required thereby minimizing manufacturing tolerances.

[0077] Further, the sensor module arranged within the door chamber is protected from contamination which ensures that the humidity sensor can provide a reliable measurement. The user cannot come into contact with the components of the sensor module, thus avoiding damage to the components of the sensor module through contact by the user. The sensor module can be accessed easily at the door so that the maintenance of the sensor module and its components is simplified.

[0078] Preferably, the sensor module comprises the main electrode, the secondary electrode and the support element for supporting the main and the secondary electrode, like a support substrate, wherein the main electrode is arranged on a first surface of the support element and the secondary electrode is at least partially arranged on the first surface of the support element so that it surrounds the periphery of the main electrode.

[0079] Alternatively, the main electrode is arranged on the first surface of the support element and a first portion of the secondary electrode is arranged on a second surface of the support element, which is opposite to the first surface, and / or a second portion of the secondary electrode is arranged on the first surface of the support element so that it surrounds the periphery of the main electrode.

[0080] Preferably the first and second surfaces of the support element are connected to each other by a lateral or circumferential surface, wherein a (e.g. third) portion of the secondary electrode connecting the (first and second) portions of the secondary electrode arranged at the first and second surface is arranged at the circumferential surface of the support element. Preferably the secondary electrode extends along at least three sides or surfaces of the support element.

[0081] Preferably, the main electrode and the secondary electrodes are arranged on the first surface of the support element (i.e. the entire secondary electrode surrounds the periphery of the main electrode and / or extends in the same plane as the main electrode) so that the main and the secondary electrodes are coplanar with respect to the first surface of the support element. Due to the arrangement of the electrodes on the support element, the effectiveness of the 'focusing' of the field lines from the main electrode to the drum's interior is improved.

[0082] Preferably, the support element is formed of an electrically insulating material such as plastic. The support element may be a plate or board, in particular a plastic board or a printed circuit board. In an implementation, the support element may be a flexible layer.

[0083] Preferably, the main electrode and / or the secondary electrode are formed on the support element, in particular on the first and / or second surface of the support element, by metallization of or metal depositing on the respective surface of the support element. I.e. the support element with the main and secondary electrodes forms a metallized plastic component. This makes it possible to realize any shape for the electrodes. Further, material costs are reduced compared to using sheet metal for the electrodes.

[0084] The use of metallized plastic simplifies the process of forming electrodes having different and / or complex shapes.

[0085] More preferably, the main electrode and the secondary electrode are formed of an electrically conducting material or are formed of an electrically insulating material having an electrically conductive layer.

[0086] The main and secondary electrodes are electrically isolated from each other.

[0087] In particular, to electrically insulate the main electrode from the secondary electrode to prevent short circuits between the electrodes, a gap between the secondary electrode or portion of the secondary electrode surrounding the periphery or outer edge of the main electrode and the outer edge of the main electrode is provided by forming / arranging the first and the secondary electrode spaced from each other on the support element made of an electrically insulating material.

[0088] In particular, the gap is provided at the first surface of the support element between the main electrode and the secondary electrode arranged on the first surface of the support element. Preferably, the gap is in the range between 0.3 mm and 50% of the maximum length of the main electrode. More preferably, the gap is in the range between 0.3 and 40 mm, 0.3 and 20 mm, 0.3 and 10 mm or 0.3 and 5 mm.

[0089] More preferably, to improve the insulation between the main electrode and the secondary electrode to prevent short circuits, an insulating element, like for example a (rubber) gasket is provided in the gap between the main electrode and the secondary electrode. The insulating element may have a thickness of at least 0,3 mm, 0,4 mm or 0,5 mm. Preferably, the insulating element is supported by the support element for electrically separating the main and secondary electrodes from each other. The insulating element is preferably arranged on the first surface of the support element facing towards the interior of the drum.

[0090] Preferably, the portion of the secondary electrode arranged on the first surface of the support element and the main electrode arranged on the first surface of the support element extend within a common plane, i.e. the main electrode does not protrude beyond the secondary electrode on the first surface of the support element.

[0091] Preferably, the humidity sensor module comprises a sensor module housing, wherein the main and secondary electrodes are at least partially encapsulated in or arranged at the sensor module housing. The sensor module housing is preferably arranged at the door, in particular within the door chamber.

[0092] Preferably, the sensor module housing comprises a front wall facing towards the interior of the drum and a rear wall facing towards the front side screen, wherein the main and secondary electrodes are arranged at the front wall of the sensor module housing, preferably at an outer surface of the front wall of the sensor module housing. Alternatively, the main and secondary electrodes may be arranged at an inner surface of the front wall within the sensor module housing.

[0093] Preferably, the sensor module housing comprises a front portion including the front wall and a rear portion including the rear wall, wherein the front portion is removably coupled with the rear portion. The removable coupling of the front and rear portions of the sensor module housing simplifies the maintenance and / or exchange of components arranged within or at an outer surface of the sensor module housing.

[0094] The shield electrode may form the front wall of the sensor module housing. In this case the main and secondary electrodes are preferably arranged on the support element and the support element is attached to the shield electrode, wherein the electrodes face in the direction of the interior of the drum.

[0095] Alternatively, the shield electrode is arranged within the sensor module housing and the main and secondary electrodes are mounted directly on the front wall of the sensor module housing (i.e. in this case the support element for supporting the main and secondary electrodes is formed by the front wall of the sensor module housing).

[0096] The sensor module housing may comprise mounting elements for mounting the components such as the main and secondary electrodes, the shield electrode and / or the control unit at or within the sensor module housing.

[0097] In case the humidity sensor, in particular the main and secondary electrodes, are not mounted on the first wall of the sensor module housing, the support element with the main and secondary electrodes may be arranged within the sensor module housing. The support element may be arranged at the inner surface of the front wall of the sensor module housing with the main and secondary electrodes facing the front wall of the sensor module housing.

[0098] The sensor module, in particular the sensor module housing, and / or the door comprises one or more mounting elements for mounting the sensor module on the door, in particular within the door chamber, and / or the sensor module, in particular the sensor module housing, is coupled or aligned by one or more adjusting elements configured to spatially align the sensor module with the door, in particular with the door chamber. Alignment with the door means in consequence an alignment with the inner space of the drum. By alignment, e.g. after having mounted the sensor module on the door, the signal quality can be optimized individually for each laundry treatment machine during assembling or for service purposes.

[0099] Preferably, the sensor module housing at least partially encapsulates the support element with the main and secondary electrodes.

[0100] Preferably the sensor module comprises the main electrode, the secondary electrode, the support element supporting the main and the secondary electrode and the shield electrode and the main electrode, the secondary electrode, the support element supporting the main and the secondary electrode and the shield electrode are mounted within or at the sensor module housing. The shield electrode may be applied or attached to the sensor module housing or the support element. The shield electrode may be a separate element which is mounted to the sensor module housing or the support element. Alternatively, the shield electrode is formed by metallization of or metal depositing on the respective surface of the sensor module housing or the support element. In the latter case, the sensor module with the main and secondary electrodes and the shield electrode can be manufactured as one component which simplifies the assembly of the laundry treatment machine.

[0101] Preferably, the sensor module housing at least partially encapsulates the shield electrode, the support element with the main and secondary electrodes.

[0102] Preferably, the control unit is arranged at or in the housing, in particular at a surface of the shield electrode facing away from the glass wall of the door.

[0103] Preferably, the control unit and / or the shield electrode are removably mounted at or within the sensor module housing.

[0104] Preferably, the control unit is arranged at the door and / or is arranged at and / or integrated in the sensor module, and in particular at or in the support element. Arranging the control unit at the door (i.e. close to the sensor module in contrast to arranging it within the laundry treatment machine cabinet) and / or in or on the sensor module or the sensor module housing provides the shortest possible distance resulting in a reduced length of the wiring between the electrodes, such as the main and secondary electrodes and preferably the shield electrode, and the control unit. Preferably shielded cables / lines are provided between the control unit and the electrodes. Thus, environmental interferences (e.g. electrostatic loads, electromagnetic radiation from different sources, magnetic fields from motors ...) or interferences from within the laundry treatment machine have a reduced effect on the sensor measurements. Preferably, the wiring between the electrodes and the control unit is preferably electrically insulated.

[0105] Preferably the control unit is arranged and / or integrated on the support element (e.g. board) supporting the main and secondary electrodes. Preferably the control unit is arranged at or mounted on a surface of the shield electrode facing away from the glass wall of the door (i.e. away from the interior of the drum). Alternatively, the control unit is arranged at a surface of the shield electrode facing the drum interior, in particular between the shield electrode and the main and secondary electrodes.

[0106] Preferably, the shield electrode is arranged at or integrated in the sensor module, and in particular at or in the support element or the sensor module housing. The shield electrode may be arranged at or integrated in the support element with the secondary electrode facing the shield electrode. More preferably, the shield electrode is arranged at a surface of the support element which is opposite to a surface facing the glass wall of the door (i.e. the interior of the drum). The shield electrode and / or the control unit may be arranged between the main and secondary electrodes and the front side screen.

[0107] Preferably, the sensor module housing has a mounting protrusion, wherein the mounting protrusion is at least partially clamped between the wall of the door main body facing towards the inner of the drum and the front side screen or the mounting protrusion is at least partially clamped between a first door frame element and a second door frame element of the door and / or the mounting protrusion is attached or mounted to the door frame.

[0108] Preferably, the sensor module housing is configured such that the sensor module housing is clamped within the door chamber between the wall of the door main body facing towards the inner of the drum and the front side screen and is positionally aligned by compression forces.

[0109] Preferably it is not necessary to fix the housing in the door chamber with additional fasteners such as screws or similar. This means that no fastenings need to be installed on the door. This simplifies and accelerates the assembly of the humidity sensor module.

[0110] The sensor module, and in particular the sensor module housing, may be arranged at a lower region of the door, in particular at the lower region of a user's viewing field of the door. Thus, even after the humidity sensor module is installed within the door chamber, it is still possible for the user to look through the door into the interior of the laundry treatment machine. Thus, the humidity sensor module does not affect user-friendliness.

[0111] Preferably, the control unit is electrically connected to the main and secondary electrode, and / or is electrically connected to the electrically conductive drum or the cabinet, and / or is electrically connected to the main controller of the laundry treatment machine, in particular for supplying a or the supply voltage to the control unit and / or to transmit and receive control signals between the main controller of the laundry treatment machine and the sensor module.

[0112] Preferably, the sensor module housing at least partially encapsulates the shield electrode, the support element, the main and secondary electrodes and the control unit.

[0113] Further, a sensor module for humidity capacitive measurements in a laundry treatment machine, in particular in a washing machine, a dryer or a washer-dryer, is provided. The sensor module comprises a support element formed of an electrically insulating material, a main electrode, a secondary electrode, wherein the main and secondary electrodes are arranged on the support element, and a control unit, wherein the main electrode and the secondary electrode each is electrically connected to the control unit. The control unit comprises a reference voltage contact adapted to provide or receive a or the reference voltage which is applied to a or the reference element of the home appliance (such as the drum or the cabinet), and a supply voltage contact adapted to receive a supply voltage from the home appliance for operating the sensor module. In operation the reference voltage Vr is applied to the reference element and the reference voltage contact of the control unit. Preferably the reference voltage is the ground voltage, in particular the common ground voltage of the laundry treatment machine (e.g. washing machine, dryer or washer-dryer). Preferably the reference voltage Vr is supplied via a main controller of the apparatus to the control unit.

[0114] Preferably, the sensor module comprises a shield support formed of an electrically conducting material or formed of an electrically insulating material having an electrically conductive layer arranged on at least a portion of the shield support, wherein the support element is mounted in or at the shield support with the secondary electrode facing the shield support, and the support element forms a shield electrode of the sensor module, wherein the shield electrode each is electrically connected to the control unit.

[0115] Further, another sensor module for capacitive measurements in a home appliance, in particular in a laundry treatment machine, is provided. The sensor module comprises a support element formed of an electrically insulating material, a main electrode and a secondary electrode, wherein the main and secondary electrodes are arranged at the support element, a (sensor module) housing at least partially encapsulating the support element with the main and secondary electrodes, and a control unit arranged at or in the housing, wherein the main electrode and the secondary electrode each is electrically connected to the control unit. The control unit comprises a reference voltage contact adapted to provide or receive a reference voltage which is applied to a reference element of the home appliance, a signal generating unit configured to generate a temporally varying voltage signals which are supplied via the electrical connection to the main electrode and the secondary electrode as main voltage, and a signal detection unit configured to detect a main signal dependent on the capacity between the main electrode and the reference element and / or a secondary signal dependent on the capacity between the secondary electrode and the reference element.

[0116] The control unit may further comprise a supply voltage contact adapted to receive a supply voltage from the home appliance, in particular from a main controller of the appliance, for operating the sensor module. The main and secondary electrodes of the sensor modules may be designed or configured as described above with respect to the laundry treatment machine. Further, the features of the sensor module described with respect to the laundry treatment machine are also applicable to the above sensor modules. The sensor module of the laundry treatment machine may be designed or configured as the above sensor modules.

[0117] Each individual feature of the laundry treatment machine can be combined with the sensor modules, or any sub-group of features (e.g. any of the dependent claims) of the laundry treatment machine can be individually combined with the sensor modules. Vice versa any individual feature or sub-group of features (e.g. any of the dependent claims) of the sensor modules can be combined with the laundry treatment machine.

[0118] Any feature disclosed herein (for the above embodiments and / or configurations and from the below described detailed embodiments and modifications) can be combined with the claimed subject individually or in any sub-combination. If herein the conjunction "and / or" is used all logical elements and combinations are individually disclosed. E.g. a, b and / or c discloses the elements / combinations a, b, c, ab, ac, be as well as abc.

[0119] Reference is made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying figures, which show:

[0120] Fig. 1 a schematic side view of a washer-dryer,

[0121] Fig. 2 an enlarged view of the door of the washer-dryer in Fig. 1,

[0122] Fig. 3 a schematic side view of another washer-dryer,

[0123] Fig. 4 an enlarged view of the door of the dryer in Fig. 3, and

[0124] Figs. 5a-e different shapes of the main electrode, secondary electrode and the shield electrode.

[0125] The following figures are related to a washer-dryer. However, it is emphasized that the invention is also applicable to a dryer or a washing machine. In case of a washer-dryer either an electrically conductive tub (not shown) of the washer-dryer (instead of a conductive drum of the dryer) or an electrically conductive drum of the washer-dryer form a counter-electrode for the main and secondary electrodes. Fig. 1 is a schematic side view of a washer dryer 2 comprising a cabinet 5 (depicted simplified), a laundry treatment drum 4 arranged within the cabinet 5, and a door 8 for closing a loading opening 9 for loading laundry 6 to be treated into the drum 4. The drum 4 of the washer-dryer 2 is arranged within a tub (not shown). As shown in Fig. 2, the door 8 may comprise a door chamber 31 formed by a glass wall 10 facing the interior of the drum 4 and a front side screen or cover 12 arranged at a side of the glass wall 10 facing away from the interior of the drum 4. The front side screen 12 preferably forms an outer surface of the door 8. The door chamber 31 is preferably a closed space. The glass wall 10 may be inclined with respect to the front side screen 12.

[0126] The washer-dryer 2 comprises a sensor module 24 arranged inside the door chamber 31 and comprising at least a main electrode 14 arranged at or near to the glass wall 10, a secondary electrode 16 arranged at or near the glass wall 10, and preferably a shield electrode 22 arranged behind the electrodes 14, 16, i.e. between the front side cover 12 and the electrodes 14, 16.

[0127] The drum 4 is an electrically conductive drum forming a counter-electrode for the main and secondary electrodes 14, 16.

[0128] The sensor module 24 may further comprise a control unit 18 connected to the main, to the secondary and to the shield electrodes 14, 16 and 22, and being configured for transmitting signals to and / or receiving signals from the main, the secondary and the shield electrodes 14, 16 and 22. Preferably, the control unit 18 is arranged inside the door chamber 31, as shown in Fig. 1.

[0129] As shown in Fig. 2, the control unit 18 and / or the shield electrode 22 may be arranged parallel to the front side screen 12. Alternatively, and as shown in Fig. 1, the shield electrode 22 and / or the control unit 18 may be arranged parallel to the main and secondary electrodes 14, 16 and / or parallel to the glass wall 10.

[0130] The control unit 18 may be electrically connected to the drum 8, and to a main controller 20 of the washer-dryer 2, in particular for supplying a supply voltage Vb to the control unit 18 and / or to transmit and receive control signals between the main controller 20 of the washer-dryer 2 and the control unit 18.

[0131] The control unit 18 may be configured to apply a main voltage Vm to the main electrode 14 and a secondary voltage Vs to the secondary electrode 16. Preferably, the main voltage Vm and the secondary voltage Vs are identical. The main voltage Vm is preferably a pulsed square signal or a sinusoidal signal with a frequency or periodicity of the voltage in the range of 0,3 - 300 kHz, preferably 100 kHz and / or an amplitude in a range of 0 to 10 V, preferably 1,25 V.

[0132] The control unit 18 may be configured to apply a reference voltage Vr to the drum 4 forming the counter-electrode for the main and secondary electrodes 14, 16. The reference voltage Vr may be zero if the drum and / or the cabinet are connected to the ground.

[0133] The main electrode 14 may be arranged at the glass wall 10 and the secondary electrode 16 may be arranged at the main electrode 14 such that the field lines 35a of the main electrode 14 directed towards the drum 4 mainly or all passing through the central region of the drum 4, towards the rear lateral surface and back surface of the drum 4, whereas the field lines 35b of the secondary electrode 16 directed towards the drum 4 are mainly passing through the front and lateral area of the drum 4 - see Fig. 1.

[0134] Due to the arrangement of the main and secondary electrodes 14, 16, the field lines of the electric field originating from the front surface of the excited main electrode 14 are 'focused' into the central region of the drum 4 towards the rear lateral surface and back surface of the drum 4, and the field lines of the electric field originating from the front surface of the excited secondary electrode 16 are deflected to the lateral front area of the drum 4. In particular, the secondary electrode 16 is placed at a shorter distance to the metallic surface of the drum 4 compared to the main electrode 14. Thus, the electric field lines of the secondary electrode 16 have a relatively short pathway to the surface of the drum 4. Electric field lines starting from the main electrode 14 are forced to reach the inner metallic surface of the drum 4 along some longer pathway compared to field lines starting from secondary electrode 16. In particular, the field lines starting from the main electrode 14 are deviated in their trajectory by the existence of the field lines generated by the secondary electrode 16. Thus, the electric field lines 35a starting from the main electrode 14 go through some greater volume of wet clothes 6, thus sampling a wider amount of clothes load. Thus, the estimation of humidity within the laundry 6 is more accurate and the drying efficiency is thus improved.

[0135] The shield electrode 22 is configured to shield the main and secondary electrodes 14, 16 to the outside. The control unit 18 may be configured to apply a shield voltage Vg to the shield electrode. Preferably, the shield voltage Vg is identical to the main Voltage Vm supplied to the main and secondary electrodes 14, 16.

[0136] As shown in Fig. 2, the main electrode 14 and the secondary electrode 16 may be arranged at a first distance dl from an external surface (i.e. surface facing away from the drum interior) of the glass wall 10. The distance may be in the range of 1,8 - 2,5 mm, or may be 2,2 mm or substantially 2,2 mm. The first distance dl may result from adhesive material used to fix the main and / or secondary electrodes 14, 16 (in particular the sensor module 24 below) to the door, and in particular to the external surface of the glass wall 10 of the door. Alternatively, the first distance dl may be zero if the main and secondary electrodes 14, 16 are directly attached to the glass wall 10.

[0137] The main electrode 14 and / or the secondary electrode 16 may be arranged at a second distance d2 from the shield electrode 22. The second distance may be in the range of 0,5 - 15 mm or 1 - 10 mm. The second distance d2 is preferably to insulate the shield electrode 22 from the main and / or secondary electrodes 14, 16 to prevent short circuits.

[0138] As shown in Fig. 2, the secondary electrode 16 at least partially surrounds the periphery 15 of the main electrode 14 - see also periphery / outer edge 15 of main electrode in Figs. 5a-e. The secondary electrode 16 preferably surrounds the main electrode 14 all around the periphery 15, i.e. the main electrode 14 forms an inner electrode and the secondary electrode 16 forms an outer electrode. In particular, and as shown in Fig. 2, the secondary electrode 16 and the main electrode 14 may extend in the same plane, i.e. are coplanar. The main electrode 14 and / or the secondary electrode 16 may have the same or different outer shape. For example, the main electrode 14 and / or the secondary electrode 16 may have the form of a semicircle or of a segment of a circle. Different exemplary shapes of the main electrode 14, the secondary electrode 16 and the shield electrode 22 are shown in Figs. 5a to 5e. Preferably, a gap g is provided between the periphery 15 of the main electrode 14 and the secondary electrode 16 surrounding the periphery 15 of the main electrode 14. The gap g may be in the range of 0.3 - 10 mm or 0.3 - 5 mm. An insulating element (not shown) such as a (rubber) gasket may be provided in the gap g between the main electrode 14 and the secondary electrode 16 to prevent short circuits. Preferably, the insulating element extends around the entire circumference of the main electrode 14 as shown in Fig. 4.

[0139] As shown in Figs. 2 the sensor module 24 further comprises a support element 26, e.g. a support substrate for supporting the main electrode 14 and the secondary electrode 16, which are arranged on the support element 26. In particular, the main and secondary electrodes 14, 16 may be arranged, preferably entirely, on a first surface of the support element 26 facing to the glass wall 10 and / or to the interior of the drum 4. The main and secondary electrodes 14, 16 may be separate elements which are mounted on the support element 26. Alternatively, the main and secondary electrodes 14, 16 may be formed on the support element 26 by coating for example by metal deposition. The support element 26 may be made of plastic and / or may be formed as a hollowed element. The support element 26 may comprise a receptacle configured for receiving the insulating element (not shown). As shown in Fig. 2, the sensor module 24 comprising the control unit 18, the shield electrode 22, the support element 26 and the main and secondary electrodes 14, 16 is preferably arranged inside the door chamber 31 and are assembled so as to form an integrated and / or ready-to -mount module.

[0140] The control unit 18 may be arranged at or integrated in the support element 26. The shield electrode 22 may be arranged at or integrated in the support element 26. Preferably, the shield electrode 22 is arranged at the support element 26 on a second surface 30 which is opposite to the first surface 28. The control unit 18 may be arranged on a side of the shield electrode 22 (or may be mounted on a surface of the shield electrode 22) facing away from the support element 26. Thus, the distances between the different components of the sensor module 24 are reduced which improves the overall performance of the sensor module 24. Preferably, the control unit 18 and / or the shield electrode 22 are arranged parallel to the front side screen 12.

[0141] Alternatively or additionally, the sensor module 24 may comprise a sensor module housing / casing 25 (shown simplified in Fig. 2), wherein the control unit 18, the shield electrode 22, the support element 26 and the main and secondary electrodes 14, 16 may be arranged at or inside the sensor module housing 25. The sensor module housing 25 may be arranged inside the door chamber 31.

[0142] Preferably, the main and secondary electrodes 14, 16 are mounted to or are integrated in (not shown) a front wall of the sensor module housing 25 facing towards the interior of the drum. In this case, the support element 26 supporting the electrodes 14, 16 may be formed by the front wall of the sensor module housing 25. The electrodes 14, 16 are preferably arranged on an outer surface of the front wall of the sensor module housing 25. The control unit 18 and / or the shield electrode 22 are preferably arranged within the sensor module housing 25. Mounting elements may be provided within the sensor module housing 25 for supporting the shield electrode 22 and / or the control unit 18.

[0143] The sensor module housing 25 and in particular the front wall of the sensor module housing 25 is preferably adapted to the shape of the door chamber 31 and in particular to the wall 10 of the door main body facing towards the interior of the drum 5. The sensor module housing 25 may comprise a front portion and a rear portion which are removably coupled. Thus, it is easy to access the components within the housing 25 such as the shield electrode 22 and / or the control unit 18, for maintenance. The sensor module 24, in particular the support element 26 or the sensor module housing 25, and / or the door 8 may comprise one or more mounting elements (not shown) for mounting the sensor module 24 in the door chamber 31. For example, the sensor module 24, in particular the support element 26 or the sensor module housing 25, may be attached to the door 8 and in particular to the external surface of the glass wall 10 by using an adhesive material. Alternatively or additionally, the sensor module 24 or the housing 25 is mounted to the door by screwing. Due to the screwing, the sensor module 24 is preferably pressed against the glass wall 10 which provides stability to the sensor module 24. The sensor module 24, in particular the support element 26, may be coupled by one or more adjusting elements (not shown) configured to spatially align the sensor module 24 with the door 8. Alternatively or additionally, the sensor module housing 25 is dimensioned so that it can be mounted into the door chamber 31 and is positionally aligned by compression forces between the glass wall 10 and the front side cover 12 (i.e. without fastening the sensor module housing 25 within the door chamber by e.g. gluing or screwing).

[0144] Fig. 3 is a schematic side view of another washer-dryer 2a, and Fig. 4 is an enlarged view of the door of the washer-dryer in Fig. 3. In the following only the differences between the washer-dryer 2a of Figs. 3 and 4 and the washer-dryer 2 of Figs. 1 and 2 are described. All other features described with respect to Figs. 1 and 2 are also applicable to the washer-dryer of Figs. 3 and 4.

[0145] The secondary electrode 17 at least partially surrounds the periphery 15 of the main electrode 14 and covers at least partially a rear surface 14a of the main electrode 14. A front surface 14b of the main electrode 14 which is opposite to the rear surface 14a faces the glass wall 10. The main electrode 14 and the secondary electrode 17 may be provided as a sensor module 24a, wherein the main electrode 14 is arranged on the first surface 28 of the support element 26 and the secondary electrode 17 is arranged at least partially on the second surface 30 of the support element 26, which is opposite to the first surface 28. In particular, the first surface 28 of the support element 26 facing towards the drum interior and the second surface 30 of the support element 26 faces away from the drum interior.

[0146] As shown in Figs. 3 and 4, the secondary electrode 17 may comprise a first portion 17a which is arranged on the second surface 30 of the support element 26, and / or a second portion 17b which is arranged on the first surface 28 of the support element 26, and / or a third portion 17c connecting the first and second portions 17a, 17b, wherein the third portion 17c is arranged on a lateral or circumferential surface of the support element 26 (i.e. on a surface which connects the first and second surfaces 28, 30 of the support element 26). The second portion 17b of the secondary electrode 17 may surround the periphery 15 of the main electrode 14 at least partially, preferably surrounds the main electrode 14 all around the periphery 15, i.e. the main electrode 14 forms an inner electrode and the secondary electrode 17 forms an outer electrode. Due to the arrangement of the electrodes 14, 17 on the support element 26, the effectiveness of the 'focusing' of the field lines from the main electrode 14 to the drum's interior is improved.

[0147] As shown in Fig. 4, the support element 26 supporting the main and secondary electrodes 14, 17 and / or the shield electrode 22 and / or the control unit 18 may be attached to or integrated in or at the sensor module housing 25. For example, the shield electrode 22 can be attached to the second surface 30 of the support element 26. The support element 26 may be formed as a hollow and / or plastic component. The main and secondary electrodes 14, 17 may be formed on the support element 26 by coating such as metal deposition. Alternatively, the support element 26 supporting the main and secondary electrodes 14, 17 may be formed by a front wall of the sensor module housing 25 facing towards the interior of the drum. The sensor module housing 25 may comprise one or more mounting elements for mounting the shield electrode 22 and / or the control unit 18 within or at the sensor module housing 25.

[0148] Preferably, the secondary electrode 17, in particular the first portion 17a of the secondary electrode 17, is arranged at a third distance d3 from the main electrode 14 and / or the second portion 17b of the secondary electrode 17. The third distance d3 may be in the range of 2,0 - 12 mm, 4,0 - 10 mm, 5,0 - 9 mm, and in particular is 6 mm. The third distance d3 is preferably to insulate the secondary electrode 17 from the shield electrode 22 to prevent short circuits.

[0149] Figs. 5a-e show different shapes of the main electrode 14, secondary electrode 16 and the shield electrode 22 perpendicular to the front surface 14b of the main electrode 14. The main electrode 14, the secondary electrode 16, 17 and / or the shield electrode 22 may have the same or different outer contours. In the shown examples, the secondary electrode 16 covers the entire periphery of the main electrode 14. The shield electrode 22 is arranged between the electrodes 14, 16 and the front screen cover 12. Preferably, the main and secondary electrodes 14, 16 are arranged in a lower region of a user's viewing field of the door 8.

[0150] Figs. 5a-c show examples in which the main electrode 14, the secondary electrode 16, 17 and the shield electrode 22 have the same outer basic shape (basic form). For example, the main electrode 14, the secondary electrode 16, 17 and the shield electrode 22 may have a circular outer shape (see Fig. 5a), a basic form of a semicircle or of a segment of a circle (Fig. 5b) or a rectangular outer shape (see Fig. 5c). In particular, in Fig. 5a, the main electrode 14 has the shape of a circle and the secondary electrode 16 has the shape of a ring enclosing the main electrode 14. Fig. 5d and Fig. 5e show examples in which the main electrode 14, the secondary electrode 16, 17 and the shield electrode 22 have different basic shapes. As shown in Figs. 5d and 5e, the main and secondary electrodes 14, 16 may have the same basic shape, whereas the shield electrode 22 has a different basic shapes. In Fig. 5d, the main and secondary electrodes 14, 16 have the basic form of a semicircle or of a segment of a circle (as shown in Fig. 5b) and the shield electrode 22 has a rectangular shape (as shown in Fig. 5c). In Fig. 5e, the main and secondary electrodes 14, 16 have a rectangular basic shape (as shown in to Fig. 5c) and the shield electrode 22 has the basic form of a semicircle or of a segment of a circle (as shown in to Fig. 5b). Figs. 5a to 5e show the secondary electrode 16 of the sensor module 24 in Figs. 1 and 2. However, it is clear that the shapes shown in Figs. 5a and 5e are also applicable to the sensor module 24a and the main and secondary electrodes 14 and 17 and the shield electrodes shown in Figs. 3 and 4.

[0151] Reference Numeral List

[0152] 2, 2a washer-dryer

[0153] 4 drum

[0154] 5 cabinet

[0155] 6 laundry

[0156] 8 door

[0157] 9 loading opening

[0158] 10 glass wall of door

[0159] 12 front side screen (e.g. plastic window) of door

[0160] 14 main electrode

[0161] 14a rear surface of main electrode

[0162] 14b front surface of main electrode

[0163] 15 periphery / outer edge of main electrode

[0164] 16, 17 secondary electrode

[0165] 17a-c first / second / third portion of secondary electrode

[0166] 18 control unit

[0167] 20 main controller

[0168] 22 shield electrode

[0169] 24, 24a sensor module

[0170] 25 sensor module housing

[0171] 26 support element (e.g. support substrate)

[0172] 28 first surface of support element

[0173] 30 second surface of support element

[0174] 31 door chamber

[0175] 35a, 35b field line of electric field of main / secondary electrode dl, d2, d3 first / second / third distance g gap between main and secondary electrode at periphery of main electrode

[0176] Vm main voltage

[0177] Vs secondary voltage

[0178] Vr reference voltage

[0179] Vb supply voltage

[0180] Vg shield voltage

Claims

Claims:

1. Laundry treatment machine (2, 2a), in particular washing machine, dryer or washer-dryer (2, 2a), comprising: a cabinet (5), a laundry treatment drum (4) arranged within the cabinet (5), a door (8) for closing an opening (9) for loading laundry (6) to be treated into the drum (4), and a humidity sensor module (24, 24a) for estimating the humidity of the laundry contained within the drum (4), the humidity sensor module (24, 24a) comprising: a main electrode (14) arranged at the door (8), a secondary electrode (16, 17) arranged at the door (8), and a control unit (18) connected to the main and secondary electrodes (14, 16) and being configured for transmitting signals to and / or receiving signals from the main and secondary electrodes (14, 16), wherein the main electrode (14) and the secondary electrode (16, 17) are electrically insulated from each other and wherein the secondary electrode (16, 17) is arranged around the main electrode so that it at least partially surrounds the outer edge of the main electrode (14).

2. Laundry treatment machine according to claim 1, wherein the secondary electrode (16, 17) extends in the same plane as the main electrode (14) and surrounds the entire outer edge of the main electrode (14) or surrounds 50 % to 90 % of the periphery of the main electrode (14), or wherein the secondary electrode (17) extends in the same plane as the main electrode (14), covers at least partially the rear surface (14a) of the main electrode and surrounds the entire outer edge of the main electrode (14) or surrounds 50% to 90% of the periphery of the main electrode (14).

3. Laundry treatment machine according to claim 1 or 2, wherein the main electrode (14) and / or the secondary electrode (16, 17) is / are arranged at a first distance (dl) from the door (8), in particular from an external surface of a glass wall (10) of the door, wherein in particular the first distance (dl) is in the range of 1,0 - 4 mm, 1,2 - 3,5 mm, 1,5 - 3 mm, 1,8 - 2,5 mm, preferably a distance of 2,2 mm, or wherein the main electrode (14) and / or the secondary electrode (16, 17) is / are attached to an external surface of a glass wall (10) of the door (8).

294. Laundry treatment machine according to any of claims 1 to 3, wherein at least a portion (17a) of the secondary electrode (17) and / or the portion of the secondary electrode, which is at the outer side of the main electrode, is arranged at a second distance (d3) from the main electrode (14), wherein in particular the second distance (d3) is in the range of 2,0 - 12 mm, 4,0 - 10 mm, 5,0 - 9 mm, preferably is a distance of 6 mm.

5. Laundry treatment machine according to any of the preceding claims, wherein the main electrode (14) and the secondary electrode (16, 17) have the same shape or different shapes, wherein preferably the surface of the second electrode (16,17) is comprised in a range of 10% - 200%, 20-40%, 30-50%, 100-120%, 110-150% of the surface of the main electrode (14).

6. Laundry treatment machine according to any of the preceding claims, wherein the main electrode (14) and the secondary electrode (16, 17) are formed of an electrically conducting material or are formed of an electrically insulating material having an electrically conductive layer.

7. Laundry treatment machine according to any of the preceding claims, wherein the humidity sensor module (24, 24a) further comprises a support structure (26) formed of an electrically insulating material which supports and / or distances or spaces the main and secondary electrodes (14, 16, 17) from each other.

8. Laundry treatment machine according to claim 7, wherein the main electrode (14) and the secondary electrode (16) are arranged entirely on a first surface (28) of the support element (26), or wherein the main electrode (14) is arranged on the first surface (28) of the support element (26) and a first portion (17a) of the secondary electrode (17) is arranged on a second surface (30) of the support element (26), which is opposite to the first surface (28), and a second portion (17b) of the secondary electrode (17) is arranged on the first surface (28) of the support element (26).

9. Laundry treatment machine according to claims 7 or 8, wherein the main electrode (14) and the secondary electrode (16) are formed / arranged spaced from each other on the support element (26) to form to a gap which electrically insulates the main electrode (14) from the secondary electrode (16, 17).3010. Laundry treatment machine according to any of the preceding claims, further comprising a shield electrode (22) arranged at the door (8) behind the main (14) and the secondary electrode (16, 17) so that it deflects field lines originating from the main and secondary electrodes (14, 16, 17) towards the interior of the drum.

11. Laundry treatment machine according to claim 10, wherein the main electrode (14) and / or the secondary electrode (16, 17) is / are arranged at a distance (d2) from the shield electrode (22) in a range of 0,5 - 40 mm.

12. Laundry treatment machine according to claims 10 or 11, wherein the control unit (18) is connected to the shield electrode (22) and is configured for transmitting signals to and / or receiving signals from the shield electrode (22), wherein the control unit (18) is configured to apply a main voltage Vm to the main electrode (14) and to the secondary electrode (16, 17), and to apply a shield voltage Vg to the shield electrode (22), wherein the shield voltage Vg corresponds to the main voltage Vm or is different than the main voltage Vm.

13. Laundry treatment machine according to claim 12, wherein the main voltage Vm is a pulsed square signal or a sinusoidal signal, and / or wherein the frequency or periodicity of the main voltage is in the range of 0,3 - 300 kHz, preferably 100 kHz, and / or wherein an amplitude of the main voltage is in the range of 0 to 12 V, preferably 1.25 V.

14. Laundry treatment machine according to any of the preceding claims, wherein the control unit (18) is configured to apply a reference voltage Vr to an electrically conductive reference element of the laundry treatment machine forming a counter-electrode for the main and secondary electrodes (14, 16, 17) and / or the shield electrode (22), wherein the reference voltage Vr differs from the main voltage Vm, or to receive from the reference element a reference voltage Vr equal to zero if the electrically conductive reference element is connected to ground.

15. Laundry treatment machine according to claim 14 wherein the electrically conductive reference element of the laundry treatment machine is the drum (4) and / or to the cabinet (5).

16. Laundry treatment machine according to any of the preceding claims, wherein the main electrode (14) is configured to detect a first capacity between the main electrode (14) and the electrically conductive reference element based on the main voltage Vm and the reference voltage Vr,wherein the secondary electrode (16,17) is configured to detect a second capacity between the secondary electrode (16,17) and the electrically conductive reference element based on the main voltage Vm and the reference voltage Vr, and wherein the control unit (18) is configured to estimate the humidity of the laundry based on the first and the second capacity.

17. Laundry treatment machine according to any of the preceding claims, wherein the main electrode (14) is configured to detect a first capacity between the main electrode (14) and the electrically conductive reference element based on the main voltage Vm and the reference voltage Vr, wherein the secondary electrode (14) is configured to detect a second capacity between the secondary electrode (16,17) and the electrically conductive reference element based on the main voltage Vm and the reference voltage Vr, wherein the shield electrode (22) is configured to detect a third capacity between the shield electrode (22) and the electrically conductive reference element based on the shield voltage Vg and the reference voltage Vr, and wherein the control unit (18) is configured to estimate the humidity of the laundry based on the first, the second and / or the third capacity.

18. Laundry treatment machine according to any of the any of the preceding claims, wherein the door (8) comprises a door chamber (31) formed by a door main body (11) made of non- conductive material, preferably glass, comprising a wall (10) facing towards an interior of the drum, and by a front side screen (12)19. Laundry treatment machine according to any of the any of the preceding claims, wherein the main, the secondary, the shield electrodes (14, 16, 17, 22) and the control unit (18) are arranged within the door chamber (31), or wherein the main, the shield electrode (14, 22), and the control unit (18) are arranged within the door chamber (31).

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