Household appliance for the care of laundry items

Abstract

The invention relates to a household appliance (1) for the care of laundry items, consisting of a housing (2) and a tub (4) arranged therein. A rotatably mounted drum (3) for holding the laundry items is provided in the tub. The tub is mechanically coupled to an upper section (12) of the housing via at least one spring element (9) and to a lower section (11) of the housing via at least one damping element (10). A first force sensor (13) detects the force transmitted via the damping element (10). Additionally, a measuring spring element (21) is provided, which is connected to both the tub (4) and the lower housing section (11), as well as a second force sensor (14) that measures the force transmitted via the measuring spring element (21). This dual sensor system enables a precise determination of the load mass of the drum.

Description

[0001] The invention relates to a household appliance for the care of laundry items, comprising a housing and a tub arranged in the housing, wherein a drum designed to receive the laundry items is rotatably mounted in the tub, wherein the tub is mechanically coupled to a region, in particular an upper region, of the housing via at least one spring element, and wherein the tub is mechanically coupled to a further region, in particular a lower region, of the housing via at least one damping element, which has a first force sensor.The invention further relates to a method for operating a household appliance for the care of laundry items, comprising a housing and a tub arranged in the housing, wherein a drum designed to receive the laundry items is rotatably mounted in the tub, wherein the tub is mechanically coupled to a region, in particular an upper region, of the housing via at least one spring element, wherein the tub is mechanically coupled to a further region, in particular a lower region, of the housing via at least one damping element, wherein at least one force transmitted by the damping element is detected by a first force sensor.

[0002] Household appliances for the care of laundry and methods of this type are extensively known in the prior art, so that a separate printed reference is not fundamentally necessary. Household appliances of this type include, in particular, washing machines, washer-dryers, and the like. For example, EP 1 285 986 A1 discloses a household appliance of this type, a washing machine in which a tub is provided in which a drum for receiving laundry is rotatably mounted. Both the tub and the drum have a through-opening, which is substantially coaxial and can be closed by means of a machine door. Through the through-openings, a user has access to the interior of the drum when the door is open, so that laundry can be placed in or removed from it.During normal operation, the door is closed and the tub is at least temporarily filled with a liquid containing detergent to ensure the desired cleaning performance for the laundry. The drum rotates as needed during normal operation. The tub, which also supports the drum, is mechanically connected to the housing by one or more springs and one or more damping elements. This creates a vibration or oscillation system to at least partially suppress vibrations that may occur during normal operation when washing laundry. Counterweights and similar components may be incorporated into the housing for this purpose.Furthermore, household appliances and processes of this type are disclosed, for example, in EP 1 264 925 A2 and DE 298 12 393 U1.

[0003] The spring-loaded suspension of the drum tub allows the load of laundry to be determined, and in particular the mass of the load. This enables the appliance's control unit to appropriately adjust the operating parameters based on the determined load. Among other things, it takes into account that an increase in the drum's weight causes the tub to lower. This lowering is directly related to the weight or mass of the system. In a washing machine, the oscillation system, which specifically affects the tub, is typically suspended by two to four springs, resulting in the lowering due to an increase in weight or mass.Furthermore, two to four vibration dampers are typically provided, which, together with the springs, also absorb a significant portion of the weight force. Generally, only the lowering of the spring-mounted tub is measured. This has resulted in a comparatively large measurement error with regard to determining the mass.

[0004] The invention is based on the objective of further developing a generic household appliance and a generic method in such a way that the mass of the laundry items in the drum can be determined more accurately with limited effort.

[0005] The invention proposes a household appliance and a method according to the independent claims as a solution.

[0006] Advantageous further training opportunities arise from the characteristics of the dependent requirements.

[0007] With regard to a household appliance of the generic type, the invention particularly proposes that the household appliance has a measuring spring element and a second force sensor, wherein the second force sensor is mechanically coupled to the measuring spring element for detecting a force transmitted by the measuring spring element, and wherein the measuring spring element is mechanically coupled to the detergent container and the further area of ​​the housing.

[0008] With regard to the method according to the invention, it is particularly proposed that the lye container and the further area of ​​the housing are further mechanically coupled by means of a measuring spring element, wherein a second force sensor mechanically coupled to the measuring spring element detects a force transmitted by the measuring spring element.

[0009] The invention proposes, for the first time, a method of determining the drum load in the tub using force sensors. This eliminates the need for displacement sensors and the associated effort. The invention is based, among other things, on the idea that the measuring spring element and the second force sensor can detect the downward movement of the drum connected to the tub, which is dependent on the load of laundry. This allows the force transmitted by the at least one spring element to be determined, taking into account the corresponding spring constant. In this way, a kind of virtual displacement sensor can be created. Since the properties of the at least one spring element are known, the force acting on it can be determined. Furthermore, the first force sensor can be used to determine the force transmitted by the at least one damping element.If multiple spring elements are present, the force exerted by these spring elements can be determined accordingly. If multiple damping elements are present, each damping element can be equipped with its own primary force sensor. Alternatively, the force for the corresponding forces of further damping elements can be estimated or determined based on the force sensor assigned to at least one damping element, for example, using mathematical methods, estimation, and / or the like. In this way, it is possible to determine the weight force of the tub and drum, particularly if the drum is not driven by rotation. By changing this weight force, the load of laundry in the drum, and thus its mass, can be determined."Coupling" within the meaning of this disclosure means in particular that the corresponding connection can be realized directly or indirectly, that is, using one or more components.

[0010] Particularly preferably, the tub is mechanically coupled to an upper area of ​​the housing via at least one spring element and to a lower area of ​​the housing via at least one damping element which has the first force sensor.

[0011] Compared to the current state of the art, the mass of the load in the drum can thus be determined with significantly greater accuracy, allowing for more precise and effective control of the laundry care process performed by the appliance. This can also improve the intended operation of the appliance, which can, for example, be made more stable and, in particular, with less vibration. At the same time, it proves advantageous that only force sensors providing the corresponding sensor signals are required to determine the mass of the laundry in the drum. This makes it possible to significantly improve the functionality of the appliance with minimal additional effort. Therefore, separate displacement sensors or similar components with corresponding processing capacity are not necessary.According to the invention, only a single sensor type, namely a force sensor, is required. This also reduces the effort required for further evaluation, because a corresponding evaluation unit only needs to be designed for processing sensor signals from force sensors. For example, the force sensors can be evaluated successively using multiplexing, so that only a single channel on the evaluation unit side is required for signal processing. Here, too, a significant improvement can be achieved with minimal additional effort.

[0012] The invention enables reliable functionality, particularly with a wide variety of damping elements. Therefore, the function of the invention is not dependent on any force-displacement characteristics of the damping elements. This proves especially advantageous when damping elements are used that exhibit a significant static friction during normal operation.

[0013] The first and second force sensors can be fundamentally identical. Known designs can be used for both, such as those employing one or more strain gauges. The force sensors preferably provide an electrical sensor signal, which can be further processed by the evaluation unit to determine the force detected by the respective force sensor. For this purpose, the evaluation unit can include a suitable electronic circuit arrangement that can be coupled to the force sensors, at least temporarily.

[0014] Force sensors often incorporate an elastic element with a high spring constant, which deforms under the influence of the force being measured. Such an elastic element can also be referred to as a "flexing beam." The high spring constant typically results in only a small deformation within the intended measuring range. This deformation can be converted into an electrical signal, the sensor signal, using a suitable sensor element. Strain gauges, for example, can be used for this purpose. A strain gauge can detect a strain of the elastic element down to 10⁻⁶ or less. The elastic element, possibly including the strain gauge, can exhibit a deformation of, for example, -0.3 mm to +0.3 mm under a force in the range of approximately -100 N to +100 N. However, the functionality of force sensors is not limited to the use of strain gauges.Force measurement can also be performed using other suitable force sensors, such as those based on the piezoelectric effect or similar principles.

[0015] In contrast, distances are measured using suitable displacement sensors. A displacement sensor typically consists of two sensor components whose relative position varies depending on the distance traveled. This can be detected by a suitable sensor element. Such a sensor element can, for example, utilize the travel time of a suitable signal between the two sensor components, such as sound, light, or the like. Inductive or capacitive detection is also possible.

[0016] The invention makes it possible to achieve the desired functionality with only a single type of sensor, namely a force sensor. In particular, the complex measurement using displacement sensors can be avoided.

[0017] In one embodiment, the measuring spring element can further be provided with a comparatively small spring constant, particularly with respect to the at least one spring element. The force provided by a deflection of this measuring spring element can be detected by means of the second force sensor. For example, the force can be in a range in which the at least one damping element also transmits force. Preferably, however, the force can be smaller.

[0018] Preferably, the two force sensors are of the same design and have a substantially comparable configuration. For example, the force sensors can incorporate strain gauges. This allows for synergistic effects, particularly regarding the evaluation by the evaluation unit, as explained above. These synergistic effects can relate, for example, to the generation, transmission, and processing of the force sensor signals. Furthermore, synergistic effects can also be achieved with regard to shielding against interference or compensating for disturbances and / or drift effects, such as temperature, electromagnetic influences, and / or the like. Additionally, synergistic effects can be achieved with regard to mechanical functionalities, such as mechanical mountings or the elastic structures for the force sensors.Furthermore, a housing for the force sensors and, if necessary, any cabling and / or the like can largely be provided together in an integrated concept for both force sensors.

[0019] In the following, a bending beam is preferably understood to be a substantially planar component made of a sufficiently elastic material, clamped at one or more sides, which, when subjected to a force, bends out of the plane of the component, which may optionally be curved (e.g., as a curved component surface), in at least one force component. This deformation can be predominantly proportional to the applied force, particularly with small amplitudes of movement, so that the applied force can be determined by measuring the deformation. The bending beam can, for example, have a substantially cuboid structure, with the length of the bending beam preferably being greater than its width and height.Especially when the force sensors incorporate strain gauges, they can be designed such that the strains detected by the strain gauges are approximately the same. For this purpose, the bending beam to which the measuring spring element is connected can, for example, be significantly narrower and therefore preferably more flexible than the bending beam connected to the damping element. This allows the same strain gauge to be used for both force sensors.

[0020] The measuring spring element can, for example, be pre-tensioned, in particular such that when the oscillating system moves and the length of the damping element changes accordingly, the spring force of the measuring spring element does not cross zero. This further improves the evaluation because, for example, free stroke or hysteresis can be avoided, and fastenings to the measuring spring element cannot rattle or disengage. The measuring spring element is preferably designed essentially as a helical spring. However, it can also be designed, for example, as a disc spring, band spring, combinations thereof, and / or the like.

[0021] A friction damper, a free-stroke damper, or a similar device can be used as a damping element. The friction damper can, for example, primarily utilize Coulomb friction or alternatively or additionally viscous friction. A free-stroke damper preferably exhibits an approximately constant and small free-stroke force within a small operating range compared to the total stroke, for example, about 5 mm. Free-stroke dampers can also be provided that utilize a double spring in the free stroke and achieve a linearly increasing force in both directions within the operating range. It can be taken into account that, for example, outside of a free-stroke range, free-stroke dampers behave like a damper without free stroke, i.e., comparable to a friction damper with pure Coulomb friction, with a typical transition from free stroke to friction operation occurring, for example, at a force of approximately 15 N.The resulting free-stroke window can, for example, adapt to changing operating points, such as when the tub lowers as the drum is loaded with laundry. Depending on the design of the damping element, a change in length can counteract a force, which, depending on its characteristics and operating conditions, can result in a force within the damping element of, for example, between approximately 0.1 N and approximately 100 N. The evaluation can involve a weighted summation of the determined force values, yielding a value for the change in the total force and thus the change in the drum's load of laundry.

[0022] According to an advantageous embodiment, it is proposed that the damping element has a first connecting element at a first end, which is connected to a retaining element arranged on the washing tub, and that the measuring spring element has a second connecting element at a first end, which is connected to the retaining element. This makes it possible to reliably connect the damping element to the washing tub mechanically in a simple manner. The connection can be detachable or permanent. The connecting element can simultaneously connect both the damping element to the washing tub and the measuring spring element to the washing tub. Therefore, no separate fastening option needs to be provided for the measuring spring element.This ensures that a change in the position of the tub, in particular its load-dependent lowering, not only acts on the damping element via the holding element arranged on the tub, but can also be detected by means of the measuring spring element.

[0023] Preferably, the deflection is measured exclusively with the measuring spring element. The force in the damping element does not need to be directly dependent on the position of the vibration or oscillating system.

[0024] Preferably, the retaining element has a connecting pin and the first connecting element has an opening, with the connecting pin being arranged in the opening. This allows for a reliable connection between the damping element and the lye drum. This connection proves particularly advantageous under vibration loads, such as those that can occur in the lye drum when it is driven by a rotating drum. Alternatively or additionally, the connecting element can also be attached to a connecting screw or an additional adapter piece.

[0025] It is further proposed that the first end of the measuring spring element be connected to the connecting pin. This allows for a simple and reliable connection between the measuring spring element and the washing tub, thus ensuring reliable mechanical coupling. Alternatively, the first end of the measuring spring element could also be connected to the first end of the damping element. For example, the measuring spring element could also be connected to an adapter element, such as a sheet metal piece on the connecting pin, or to an upper part of the damping element, or even to a differently shaped section on the washing tub.

[0026] According to a further development, it is proposed that the household appliance has a connecting tab comprising a first connecting area and a second connecting area separate from the first. The damping element has a second end, which is opposite the first end in the longitudinal direction. The first connecting area is connected to the wider area, particularly the lower area, of the housing, and the second connecting area is connected to the second end of the damping element. In this way, a reliable connection between the wider housing area, especially the base, and the damping element can be established. This allows forces acting on the damping element from the washing machine tub to be reliably transferred to the housing. The first and second connecting areas can be directly adjacent to each other.A single-piece component can be provided to form the connecting tab, thus enabling a simple mechanical coupling between the damping element and the lower part of the housing. The connecting tab can essentially be a flat component with a fundamentally cuboid structure. Furthermore, the connecting tab can be essentially flat. However, the connecting tab can also be at least partially curved or bent. The first and second connection areas can be linked by a curve or bend in the connecting tab.

[0027] The connecting tab can be made of a metallic material, in particular spring steel. To connect the second section to the second end of the damping element, a further connecting part, for example a damper clamp or the like, can be provided. The first section of the connecting element can be connected to the further section, in particular the lower section, of the housing by means of a connection such as clinching, screwing, welding, riveting and / or the like.

[0028] It is further proposed that the connecting tab has a first measuring area formed between the first and second connecting areas, connecting them, with the first force sensor being arranged at the first measuring area. The first measuring area can preferably be at least partially elastic. The first measuring area can be part of the force sensor. The force sensor, for example a strain gauge or the like, can be arranged at the measuring area so that the force transmitted via the damping element or the force acting on the damping element can be detected by means of the force sensor. The first measuring area can be integral with the first and second connecting areas. However, the first measuring area can also be separated from the first and / or second connecting areas by means of a kink and / or a curvature.Preferably, the connecting tab is formed integrally with the first measuring range.

[0029] It is further proposed that the connecting tab has a third connecting area, separate from the first and second connecting areas. The measuring spring element has a second end, which is opposite the first end in the longitudinal direction and is connected to the third connecting area. This allows for a mechanical parallel connection of the measuring spring element and the damping element. The separately formed third connecting area makes it possible to mechanically couple the measuring spring element to the other area, particularly the lower area, of the housing via the same connection using the connecting tab. It is particularly advantageous if the first end of the measuring spring element is simultaneously connected to the retaining element of the washing container.

[0030] Furthermore, it is proposed that the connecting tab has a second measuring area formed between the first and third connecting areas, connecting them, with the second force sensor being arranged on the second measuring area. This allows the connecting tab to detect not only the force acting on the damping element using the first force sensor, but also the force acting on the measuring spring element using the second force sensor. It can be taken into account that the lowering of the vibration system is transmitted to the measuring spring element as a change in length, which acts as a force on the third connecting area. This provides a particularly simple design concept for realizing the invention.The connecting tab is preferably designed such that the second measuring area is separate from the first, allowing the two force sensors to detect the respective acting forces essentially without interference from each other. The second measuring area can also preferably be at least partially elastic. Preferably, the connecting tab is fully elastic. Furthermore, the first and second measuring areas can be essentially identical. However, it is also possible for the two measuring areas to be adapted to the respective acting forces, particularly to allow the use of essentially the same component design for both the first and second force sensors.

[0031] Furthermore, it is proposed that the second and third connection areas are only connected to each other via the first connection area. This allows the acting forces to act essentially independently on the rest of the housing or the housing base. This can reduce or eliminate disruptive interactions.

[0032] It is further proposed that the household appliance include a reference force sensor. The reference force sensor can be designed in the same way as the first and / or second force sensors. The reference force sensor can serve to detect interfering influences on the force sensors, which can then be taken into account during further signal processing. The reference force sensor can preferably be mounted at a location on the household appliance where either no force acts upon it, or, more preferably, opposite one of the other strain gauges, for example, on the underside of a sheet metal panel. This ensures that the strain during deformation due to force has opposite signs in the two strain gauges, while a disturbance, for example, due to temperature, has the same sign in both strain gauges, thus making the measurement and the disturbance separable.

[0033] Advantageously, the household appliance has an evaluation unit that is signal-linked to at least the first and second force sensors and is designed to evaluate at least the sensor signals from the first and second force sensors and to determine the mass of laundry items arranged in the tub. The evaluation unit can be at least partially an electronic unit, which, for example, can be at least partially integrated into the appliance's control system. Furthermore, the evaluation unit can also include a program-controlled processing unit that provides the desired evaluation functionality when a computer program is executed.

[0034] It is further proposed that the evaluation unit comprise at least one bridge circuit which is signal-coupled to at least the first or the second force sensor, preferably with the bridge circuit being connected to the reference force sensor. The bridge circuit enables the reliable processing of sensor signals, particularly electronic or electrical signals, and the reduction or suppression of interfering influences such as temperature or the like. It is particularly advantageous if the bridge circuit is also connected to the reference force sensor, which can serve to identify and reduce the influences that might interfere with or impair the force sensor readings during signal processing by the evaluation unit. The bridge circuit can, for example, be implemented as a hardware circuit.Furthermore, it is also possible to implement the bridge circuit, at least partially, using a program-controlled computer unit. For example, hardware-implemented bridge branches of the circuit can be coupled to one or more inputs of the computer unit. Thus, it is possible to couple the bridge branches to a single input of the computer unit using a multiplexer. For this purpose, the individual bridge branches can be activated separately by the computer unit. The computer unit can then supplement or complete the functionality of the bridge circuit, at least partially, by executing a suitable computer program. This also eliminates the need for a single reference force sensor.

[0035] It is further proposed that the evaluation unit includes a switching unit to which the first and second force sensors, as well as the reference force sensor, are connected. The evaluation unit is configured to control a switching state of the switching unit by means of a switching signal such that one of the three force sensors—namely, the first force sensor, the second force sensor, or the reference force sensor—is connected to an analog input of the evaluation unit. The analog input can, for example, be an input of the computer unit that provides analog-to-digital conversion. This makes it possible for the evaluation unit to provide only a single signal evaluation channel. The sensor signals of the three force sensors can then be evaluated and processed using time-division multiplexing. This reduces the effort required to implement the invention.The switching unit can be implemented either via a hardware circuit or at least partially via the computer unit. For example, it is possible to activate individual bridge branches as needed using a switching unit on the computer unit. This allows the switching unit to preferentially connect one of the three strain gauges to the input of the evaluation unit, so that its sensor signal arrives there and can be evaluated. The values ​​from the two measuring strain gauges and the reference strain gauge are available in the evaluation unit with a time offset. The difference can be calculated by the computer unit. With a hardware-implemented bridge circuit, the difference would be determined by hardware.

[0036] Terms such as "top", "bottom", "front", "back", "horizontal", "vertical", "front", "back", "depth", "latitudinal", "height" and the like indicate the positions and orientations that would be present when the household appliance is used and arranged as intended, and when viewed from the perspective of an observer standing in front of the appliance and looking towards it.

[0037] The advantages and effects stated for the household appliance according to the invention also apply equally to the method according to the invention, and vice versa. In particular, device features can therefore also be formulated as method features and vice versa.

[0038] Further features of the invention are evident from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the figures, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention. Embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features, in particular those set out above, are to be considered disclosed which go beyond or deviate from the combinations of features set out in the cross-references of the claims.

[0039] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the drawings. In the drawings, identical reference numerals denote identical functions and features. The drawings show: Fig. 1 a schematic perspective view of a washing machine, Fig. 2 a schematic interior view of the washing machine according to Fig. 1 , Fig. 3 a schematic representation of the operating principle of an oscillation system of the washing machine according to Fig. 1 , Fig. 4 a schematic front view of a damping element with a measuring spring element in area IV in Fig. 2 , wherein the damping element and the measuring spring element are connected together with a base of a washing machine housing by means of a connecting tab according to Fig. 2 are connected Fig. 5 a schematic side view of the damping element and the measuring spring element according to Fig. 4 , Fig. 6 in a schematic top view the connecting tab according to Fig. 5 , Fig. 7 a schematic circuit diagram of a bridge circuit with two strain gauges, and Fig. 8 a schematic circuit diagram of an evaluation unit of the washing machine according to Fig. 1 with a bridge circuit according to Fig. 7 .

[0040] Fig. 1 Figure 1 shows a schematic, perspective view of a washing machine 1, which serves as a household appliance for washing laundry. In alternative configurations, the appliance can also be a washer-dryer or the like. The washing machine 1 has a width direction x, a depth direction z, and a height direction y. The terms "top" and "bottom" refer to a vertical dimension.

[0041] Alignment of the washing machine during setup for intended use.

[0042] The washing machine 1 has a housing 2 in which a tub 4 is arranged, wherein a washing drum 3 is rotatably mounted in the tub 4. The laundry items to be washed can be placed in the washing drum 3. The washing drum 3 is rotatably mounted relative to the tub 4 via a pivot axis (not shown).

[0043] The washing drum 3 has a substantially hollow cylindrical shell and a rear end wall. The washing drum 3 is also open at the front, providing a loading opening through which a user can place or remove laundry items into an interior 5 of the washing drum 3. The tub 4 has a corresponding opening that is arranged coaxially with the loading opening. The loading opening can be closed by a door 6 of the washing machine 1, which is movably hinged to the housing 2. This also allows the opening of the tub 4 to be closed. The washing drum 3 can be driven to rotate by a drive motor 7. The drive motor 7 is controlled appropriately by a control unit 8 of the washing machine 1. As shown from Fig. 1 Furthermore, as can be seen, the control unit 8 includes an evaluation unit 23, which will be explained in more detail below.

[0044] Fig. 2 shows a schematic interior view of washing machine 1 according to Fig. 1 The washing container 4 is mechanically coupled to a housing cover 12 formed in an upper region of the housing 2 via three spring elements 9. Furthermore, the washing container 4 is mechanically coupled to a housing base 11 formed in a lower region of the housing 2 via three damping elements 10.

[0045] Fig. 4 shows a schematic front view of one of the damping elements 10 with the measuring spring element 21 in a region IV according to Fig. 2 The damping element 10 has a first connecting element 25 at a first end 26, in which an opening 31 is formed at the first end 26. Furthermore, a retaining element 27 is arranged on the tub 4, which in this case is designed as a connecting pin 30. The connecting element 25 is connected to the retaining element 27 by the fact that the connecting pin 30 is arranged in the opening 31. In this case, the connecting pin 30 is rotatably arranged in the opening 31.

[0046] Furthermore, it is from Fig. 4 It is evident that the measuring spring element 21 has a second connecting element 29 at a first end 28, which is also connected to the retaining element 27. In this case, the second connecting element 29 is formed by a detent projection that engages in a corresponding detent recess on the retaining element 27 or on the connecting pin 30. Other connection techniques are also conceivable.

[0047] Out of Fig. 4 It is further evident that the washing machine 1 has a connecting tab 22, which in this case is designed in the manner of a bending beam. The connecting tab 22 has a first connecting area 33 and a second connecting area 32 that is separate from the first connecting area 33 (see also Fig. 6 The damping element 10 has a second end 35, which is opposite the first end 26 in the longitudinal direction of the damping element 10. The first connection area 33 is connected to the housing base 11 of the housing 2, and the second connection area 32 is connected to the second end 35 of the damping element 10. As shown in Fig. 4 As can be seen, the connection is realized by means of a damper clamp 40. This damper clamp 40 enables the damping element 10 to be pivotally mounted about a pivot axis (not shown) relative to the second connection area 32.

[0048] The connecting tab 22 further comprises a first measuring area 37, which is formed between the first and the second connecting areas 32, 33 and connects the first to the second connecting area 32, 33. The first force sensor 13 is arranged on the first measuring area 37. This makes it possible to detect the force acting on the damping element 10 by means of the force sensor 13. In this example, the first measuring area 37 is delimited from the first and the second connecting areas 32, 33 by respective bends. In alternative embodiments, however, no bends need to be provided. Fig. 5 shows a schematic side view of the damping element 10 and the measuring spring element 21 according to Fig. 4 .

[0049] Fig. 6 A schematic top view shows the connecting tab 22 according to Fig. 5 As can be seen from the Fig. 4 and 6As can be seen, the connecting tab 22 has a third connecting area 34 that is separate from the first and second connecting areas 32, 33. The measuring spring element 21 has a second end 36, which is opposite the first end 28 in the longitudinal direction of the measuring spring element 21. The second end 36 of the measuring spring element 21 is connected to the third connecting area 34. The connection can be configured in the same way as the connection between the measuring spring element 21 and the connecting pin 30. However, other suitable connections are also conceivable.

[0050] The connecting tab 22 has a second measuring area 38, which is formed between the first and the third connecting areas 33, 34 and connects the first with the third connecting area 33, 34. The second force sensor 14 is arranged on the second measuring area 38. This allows a force acting on the measuring spring element 21 to be detected by means of the second force sensor. In this embodiment, the second measuring area 38 is separated from the first connecting area 33 by a bend. Other designs are also conceivable.

[0051] The measuring areas 37, 38 are formed in this case by respective elastically deformable areas of the connecting tab 22, as can be seen from the Fig. 5 and 6 as is evident.

[0052] Fig. 5 shows a schematic side view of the damping element 10 and the measuring spring element 21 according to Fig. 4 . Out of Fig. 6 It is further evident that the connecting tab 22 is essentially formed in one piece. The measuring areas 37, 38 and the connecting areas 32, 34 are each mechanically separated from one another by a recess 41. This design allows the force sensors 13, 14 to detect the respective forces essentially without interference from each other.

[0053] As from Fig. 6 As can be further seen, the force sensors 13, 14 are implemented in this case by arranging strain gauges 16, 18 in the respective measuring areas 37, 38. The strain gauges 16, 18 can detect a deformation of the respective measuring area due to the application of a force, thus providing an electrical sensor signal which can be evaluated by the evaluation unit 23.

[0054] Fig. 3 shows a schematic representation of the operating principle of an oscillation system of washing machine 1 according to Fig. 1 For the sake of clarity, only a spring element 9, a damping element 10, and the measuring spring element 21, which form the oscillation system, are shown in addition to the tub 4. The basic principle is essentially comprehensible from this illustration. It can be seen that the tub 4 is spring-loaded relative to the housing 2, in particular relative to the housing cover 12 and the housing base 11. This type of mounting makes it possible to detect the loading of the drum 3 with laundry items, at least outside of a rotating drive of the drum 3, in order to determine the mass of the laundry items or the resulting change in weight force. Fig. 3 It is evident that the damping element 10 is configured in series with the force sensor 13, whereas the measuring spring element 21 is configured in series with the force sensor 14. This allows the respective forces in the damping element 10 and in the measuring spring element 21 to be selectively detected by means of the force sensors 13 and 14, respectively. The force detection preferably takes place in a state in which the drum 3 is not being driven by rotation. Such a state can be achieved, for example, with the door 6 open or during a break in operation in which the drive motor 7 is not driving the drum 3. However, the invention is not limited to this.

[0055] Fig. 7 Figure 1 shows a schematic circuit diagram of a bridge circuit 24, which can be used to evaluate the sensor signals from the force sensors 13 and 14. As shown in Figure 2, the circuit diagram illustrates the following: Fig. 7 As can be seen, the washing machine 1 has a reference force sensor 17, which is essentially formed by a strain gauge, preferably having essentially the same construction as the strain gauges 16, 18. The reference force sensor 17 can be arranged at a suitable location on the housing 2, for example in a region of the connection area 33 of the connecting tab 22.

[0056] The basic principle of the bridge circuit is known to those skilled in the art, which is why further detailed explanations are omitted here. It should only be explained that the respective strain gauges 16, 18 form a series circuit with a resistor R1, at the center terminal of which a terminal U a is formed. This series circuit is connected to a power supply with an electrical reference potential 19 and an electrical supply potential 20. Essentially the same is provided for the reference force sensor 17, whose strain gauges form another series circuit with a further electrical resistor R 2, which has a center terminal with a terminal U b. This series circuit is also connected to the reference potential 19 and the supply potential 20, thus being connected in parallel to the aforementioned series circuit.A differential voltage U d can be detected between the connection contacts U a and U b.

[0057] The special features of the bridge circuit 24 are known to those skilled in the art, which is why further explanations are omitted here. The evaluation unit 23 is signal-connected to the first and second force sensors 13, 14 and is configured to evaluate at least their sensor signals in order to determine the mass of laundry items arranged in the tub 4, in particular in the washing drum 3. In the present embodiment, the evaluation unit 23 includes a computer unit 42, which provides a switching unit 39. This can be seen from the schematic circuit diagram according to Fig. 8 As can be seen, a bridge circuit 24 is connected to the computer unit 42, to which both the strain gauges 16, 18 and the strain gauge of the reference force sensor 17 are connected. This essentially provides three parallel-connected series circuits, as can be seen from the Fig. 7 As already explained, the center terminals of the series circuits are connected via decoupling amplifiers 43 to an input of the computer unit 42, which provides analog-to-digital conversion. The respective resistors R of the respective series circuits are coupled to respective output terminals of the computer unit 42, which can be switched to supply the respective series circuit with the supply potential 20. This makes it possible to selectively activate a respective series circuit using the switching unit 39 of the computer unit 42, so that the computer unit 42 can detect and process the respective sensor signal as a voltage signal. The weight force can then be determined by signal processing of all detected voltage signals provided by the computer unit 42.In comparison to a reference weight force of the empty washing drum 3, determined previously, for example, during the manufacture of washing machine 1, it is then possible to determine a differential weight force that essentially corresponds to the mass of the laundry items placed in the washing drum 3. The computer unit 42 can output this signal as a weight signal 44 to the control unit 8, which controls the washing machine 1 during its intended operation, at least depending on the weight signal 44.

[0058] According to the invention, it is therefore possible with minimal effort to determine the force acting on the spring elements 9 due to a positional displacement of the tub 4 using the measuring spring element 21, and, using the force detected by the first force sensor 13 on at least one of the damping elements 10, to determine the total weight of the tub 4 with the drum 3 and any laundry items stored therein. The inventive design thus enables a precise determination of the mass of the laundry items compared to the prior art, while at the same time, signal processing can be implemented with minimal effort due to the fact that only force sensors are required.

[0059] The exemplary embodiments serve solely to illustrate the invention and are not intended to limit it. Bezugszeichenliste

[0060] 1 Household appliance 2 Housing 3 Washing drum 4 Tub 5 Interior 6 Door 7 Drive motor 8 Control unit 9 Spring element 10 Damping element 11 Housing base 12 Housing cover 13 First force sensor 14 Second force sensor 15 Reference force sensor 16 Strain gauge 17 Strain gauge 18 Strain gauge 19 Reference potential 20 Supply potential 21 Measuring spring element 22 Connecting tab 23 Evaluation unit 24 Bridge circuit 25 First connecting element 26 First end 27 Holding element 28 First end 29 Second connecting element 30 Connecting pin 31 Opening 32 Connection area 33 Connection area 34 Connection area 35 Second end 36 Second end 37 Measuring area 38 Measuring area 39 Switching unit 40 Damper clamp 41 Recess 42 Computer unit 43 Decoupling amplifier 44 Weight force signal R, R1, R2 Electrical resistance Ua Connection contact Ub Connection contact Ud Differential voltage

Claims

1. Household appliance (1) for the care of laundry items, comprising a housing (2) and a tub (4) arranged in the housing (2), wherein a drum (3) designed to receive the laundry items is rotatably mounted in the tub (4), wherein the tub (4) is mechanically coupled to a region (12), in particular to an upper region (12), of the housing (2) via at least one spring element (9), wherein the tub (4) is mechanically coupled to a further region (11), in particular to a lower region (11), of the housing (2) via at least one damping element (10), and to a first force sensor (13) at least for detecting a force transmitted by the damping element (10), characterized bya measuring spring element (21) and a second force sensor (14), wherein the second force sensor (14) is mechanically coupled to the measuring spring element (21) for detecting a force transmitted by the measuring spring element (21), wherein the measuring spring element (21) is mechanically coupled to the lye container (4) and the further area (11) of the housing (2).

2. Household appliance according to claim 1, characterized by the fact that the damping element (10) has a first connecting element (25) at a first end (26) which is connected to a retaining element (27) arranged on the tub (4), and the measuring spring element (21) has a second connecting element (29) at a first end (28) which is connected to the retaining element (27).

3. Household appliance according to claim 2, characterized by the fact that the retaining element (27) has a connecting pin (30) and the first connecting element (25) has an opening (31), wherein the connecting pin (30) is arranged in the opening (31).

4. Household appliance according to claim 3, characterized by the fact that the first end (28) of the measuring spring element (21) is connected to the connecting pin (30).

5. Household appliance according to one of the preceding claims, characterized by a connecting tab (22) having a first connecting area (33) and a second connecting area (32) formed separately from the first connecting area (33), wherein the damping element (10) has a second end (35) which is opposite the first end (26) in the longitudinal direction, wherein the first connecting area (33) is connected to the further area (11) of the housing (2) and the second connecting area (32) is connected to the second end (35) of the damping element (10).

6. Household appliance according to claim 5, characterized by the fact thatthe connecting tab (22) has a first measuring area (37) which is formed between the first and the second connecting area (32, 33) and connects the first with the second connecting area (32, 33), wherein the first force sensor (13) is arranged at the first measuring area (37).

7. Household appliance according to claim 5 or 6, characterized by the fact that the connecting tab (22) has a third connecting area (34) formed separately from the first and second connecting areas (32, 33), wherein the measuring spring element (21) has a second end (36) which second end (36) is opposite the first end (28) in the longitudinal direction, wherein the second end (36) of the measuring spring element (21) is connected to the third connecting area (34).

8. Household appliance according to claim 7, characterized by the fact thatthe connecting tab (22) has a second measuring area (38) formed between the first and the third connecting area (33, 34) and connects the first with the third connecting area (33, 34), wherein the second force sensor (14) is arranged on the second measuring area (38).

9. Household appliance according to one of claims 7 or 8, characterized by the fact that the second and third connection areas (32, 34) are only connected to each other via the first connection area (33).

10. Household appliance according to one of the preceding claims, characterized by a reference force sensor (17).

11. Household appliance according to claim 10, characterized by the fact that the reference force sensor (17) is arranged on the connecting tab (22).

12. Household appliance according to one of the preceding claims, characterized byan evaluation unit (23) which is at least signal-technically coupled to the first and the second force sensor (13, 14) and which is configured to evaluate at least sensor signals of the first and the second force sensor (13, 14) in order to determine a mass of laundry items arranged in the tub (4).

13. Household appliance according to claim 12, characterized by the fact that the evaluation unit (23) has at least one bridge circuit (24) which is coupled to at least the first or the second force sensor (13, 14) via a signal connection, wherein preferably the bridge circuit (24) is connected to the reference force sensor (17).

14. Household appliance according to claim 13, characterized by the fact thatthe evaluation unit (23) has a switching unit (39) to which the first and second force sensors (13, 14) and the reference force sensor (17) are connected, wherein the evaluation unit (23) is configured to control a switching state of the switching unit (39) by means of a switching signal such that the bridge circuit (24) is coupled to either the first or the second force sensor (13, 14) via a signal.

15. Method for operating a household appliance (1) for the care of laundry items, comprising a housing (2) and a tub (4) arranged in the housing (2), wherein a drum (3) designed to receive the laundry items is rotatably mounted in the tub (4), wherein the tub (4) is mechanically coupled to a region (12), in particular to an upper region (11), of the housing (2) via at least one spring element (9), wherein the tub (4) is mechanically coupled to a further region (11), in particular to a lower region (11), of the housing (2) via at least one damping element (10), wherein a first force sensor (13) detects at least one force transmitted by the damping element (10), characterized by the fact thatthe lye container (4) and the further area (11) of the housing (2) are furthermore mechanically coupled by means of a measuring spring element (21), wherein a second force sensor (14) mechanically coupled to the measuring spring element (21) detects a force transmitted by the measuring spring element (21).

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