EP2379787B1 - Method for determining a static and a dynamic imbalance, corresponding device and household appliance comprising said device - Google Patents

Description

The present invention relates to a method for determining an imbalance occurring in a drum of a domestic appliance for the care of laundry items, caused by a distribution of the laundry items in an interior of the drum, in which a static and a dynamic imbalance are determined. Moreover, the present invention relates to a corresponding device and household appliance with such a device accordingly established.

In washing machines, dewatering of washed items of laundry usually takes place mechanically in a so-called spin mode. During spin operation, the drum rotates at a relatively high speed, for example, at a speed of about 1,200 rpm, so that the laundry is tight against an inner wall of the drum. If the items of laundry are distributed unevenly, there is an imbalance and the drum and mechanically connected to the drum parts of the washing machine, such as a tub, begin to oscillate. These vibrations can become particularly strong in resonance areas of the washing machine, so that the drum can not be raised to a desired speed, resulting in unsatisfactory spin or wash results. In order to take this problem into account, methods are already known from the prior art in which the imbalance caused by the distribution of the items of laundry within the drum can be determined. Thus, the document discloses DE 196 16 985 A1 a method for balancing an imbalance occurring in a spinning operation in a drum of a washing machine. In this method, depending on a detected imbalance, a leveling liquid is introduced into drum-side in-plane cavities, wherein the mass of the imbalance and beyond an axial position of the imbalance within the drum is determined. Then, depending on the mass and the axial position of the imbalance, the imbalance compensation is carried out. Preferably, in the known method, a plurality of separate means are provided, by means of which the mass of the imbalance and beyond the axial position of the imbalance can be determined.

A method for determining a dynamic imbalance of a washing machine is out EP 1 167 609 A1 known. In the disclosed method, with a plurality of uniaxial acceleration sensor or a multiaxial acceleration sensor, imbalance-induced movement of the washing machine's tub is determined. The disadvantage of this method is that the cost-intensive provision of several such sensors.

The object of the present invention is to provide a method and a device or domestic appliance, in which a determination of the dynamic imbalance, in particular when using a single sensor, is ensured with little effort.

This object is achieved by a method with the features of claim 1, and by a device with the features according to claim 8 and by a household appliance with the features according to claim 10. Advantageous embodiments of the invention are specified in the subclaims which can be combined individually or in any combination with the patent claim 1, the patent claim 8 or the patent claim 10, if such a combination is technically possible and useful.

In an inventive method for determining an occurring in a drum of a household appliance for the care of laundry, caused by a distribution of the laundry items in an interior of the drum imbalance at least one dynamic imbalance is determined. A basic idea is that in each case a value of an amplitude of a movement behavior of a liquor container arranged in the domestic appliance is determined at at least two different rotational speeds of the drum, and that the dynamic unbalance is determined as a function of the at least two values of the amplitude. In a development of the invention, a static imbalance can advantageously also be determined at the same time as a function of a value of the ascertained amplitudes. Thus, both the static and dynamic imbalance can be determined with a simple sensor, in particular a uniaxial displacement sensor.

The term household appliance is understood here in particular a washing machine, a dryer or a washer-dryer.

In other words, an essential idea of the present invention is that for determining the dynamic and possibly the static unbalance a measured variable is considered which characterizes a movement behavior of a tub, wherein at least two different values of a speed of the drum each have a value of an amplitude of Measured variable is determined. Depending on the at least two values of the amplitude, the dynamic and possibly also the static unbalance are then determined. In particular, it may be provided that in the case of the at least two different rotational speeds, in particular at least two predetermined desired rotational speeds, a value of an average amplitude of the measured variable is determined over at least half a period of a course of the measured variable, and depending on the at least two values average amplitude, the static and the dynamic imbalance are determined. To determine the average amplitude, a distance between the envelopes of the course of the measured variable can preferably be used. Advantageously, it is achieved by the method according to the invention that, based on the determined static and / or dynamic imbalance, a vibration behavior of a vibration system of the domestic appliance having the drum and the tub can be determined. As a result, an improved control of the rotational speed of the drum is ensured. If it is detected from the determined dynamic and / or static imbalance that permissible limits are exceeded, then a transition into a centrifugal operation can be influenced. In particular, a cancellation of the spinning operation or a lowering of the speed can be made. By additionally determining the dynamic unbalance, the system movements and loads can be determined much more precisely.

Preferably, a displacement signal characterizing a deflection of the tub from a rest position and / or a speed and / or an acceleration of the tub are selected as the measured variable. In particular, it may be provided that a displacement sensor in the household appliance, preferably in a damper of the tub, is arranged, which is designed to generate the displacement signal characterizing the deflection of the tub from the rest position. Alternatively, it is also possible to use an acceleration sensor and to select a signal representing an acceleration of the movement of the tub as the measured variable. By integrating the acceleration signal, a speed of movement of the tub can be obtained. Therefore, instead of a displacement sensor and sensors for detecting the acceleration and / or the speed of the tub can be used.

An imbalance in the rotating drum of the tub forces a vibration of the tub. The amplitude of such a forced oscillation depends on device-specific parameters and the rotational speed of the drum (exciter frequency). For each degree of freedom of vibration own device-specific parameters apply. Since the oscillatory tub can now move freely in six degrees of freedom, determined by means of an amplitude of the signal, in particular the path signal of the tub, static unbalance for one degree of freedom only in the first approximation, because a certain proportion of the amplitude in this degree of freedom the vibration in a further degree of freedom or is dependent on a dynamic imbalance. Because each degree of freedom of movement of the tub has different resonance frequencies, the static imbalance is over- or underestimated depending on the speed. By the method, and in particular by comparing the imbalance or the amplitude of the signal, in particular the path signal, at least two different speeds, the dynamic imbalance can be determined and thus the static imbalance can be specified. From the comparison, a variable dependent on the dynamic imbalance or the dynamic imbalance can be determined directly. A mathematical formula in which the values of the amplitude of the signal or the unbalance at the at least two different rotational speeds are related to one another is also understood as such a comparison.

In one embodiment, a system of equations having at least two equations is formed, wherein the static and the dynamic unbalance are determined on the basis of the system of equations. It can be provided that a linear system of equations is selected as the equation system. In particular: unbalance (1st approximation) = (A * imbalance static + B * unbalance dynamic). Preferably, at least two constants of the system of equations, in particular A and B, speed-specific for the at least two selected values of the speed set.

In one embodiment it can be provided that an increase and / or decrease of the rotational speed is carried out as a function of the dynamic imbalance. In particular, an adaptation of an end speed, that is to say a speed during the spin operation, can be carried out so that loads determined from the static and the dynamic unbalance can not exceed a permissible limit value. If the at least two values of the rotational speed are selected such that the at least two values lie below a resonance rotational speed, then a transition to the centrifugal operation can be omitted if the determined dynamic imbalance shows that the tumbling movements of the drum become too great. Such a so-called disaster detection can also be due to the static unbalance.

A device according to the invention is designed for determining an unbalance occurring in a drum of a domestic appliance for the care of laundry items, caused by a distribution of the laundry items in an interior of the drum. The device comprises an unbalance determination device, which is designed to determine a dynamic imbalance. A basic idea is that the unbalance determination device is designed to determine in each case a value of an amplitude of a movement characterizing a movement of a liquor container arranged in the domestic appliance at at least two different rotational speeds of the drum, and depending on the at least two values of the amplitude, the dynamic unbalance to investigate. In addition, the unbalance determination device is advantageously designed to additionally determine a static imbalance in dependence on a value of the amplitudes.

Advantageous embodiments of the method according to the invention are to be regarded as advantageous embodiments of the device according to the invention.

Fig. 1

einen Verlauf einer Drehzahl einer Trommel eines Haushaltgeräts zur Pflege von Wäschestücken sowie einen Verlauf eines eine Auslenkung eines Laugenbehälters aus einer Ruhestellung charakterisierenden Wegsignals bei einer in einer axialen Mitte der Trommel ausgebildeten Unwucht;

Fig. 2

einen Verlauf der Drehzahl der Trommel sowie einen Verlauf des Wegsignals bei einer an einem hinteren axialen Rand der Trommel ausgebildeten Unwucht;

Fig. 3

einen typischen Verlauf einer Amplitude des Wegsignals in Abhängigkeit der Drehzahl der Trommel bezüglich eines Ortsvektors bzw. eines Freiheitsgrades der Schwingung des Laugenbehälters;

Fig. 4

eine schematischen Darstellung einer Waschmaschine.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawings. Showing:

Fig. 1

a course of a rotational speed of a drum of a household appliance for the care of laundry items and a course of a deflection of a tub from a rest position characterizing path signal formed in an axial center of the drum imbalance;

Fig. 2

a course of the rotational speed of the drum and a course of the path signal at a formed at a rear axial edge of the drum imbalance;

Fig. 3

a typical course of an amplitude of the path signal as a function of the rotational speed of the drum with respect to a location vector or a degree of freedom of the vibration of the tub;

Fig. 4

a schematic representation of a washing machine.

The embodiment explained in more detail below represents a preferred embodiment of the present invention.

Given is an in Fig. 4 shown domestic appliance for the care of laundry items 7, in this case a washing machine, which has in a housing 1 a spring 9 suspended from the tub 3 with a rotatably mounted drum 8 therein. At the tub 3, a balance weight 11 is attached. The drum is driven by a motor 5 via a belt 4. In a damper 6 of the tub 3 a not shown displacement sensor is arranged in the present example, which is able to detect a deflection of the tub 3 from a rest position, and to generate a signal characterizing this deflection. Hereinafter, this signal is referred to as a path signal. The invention also includes alternative arrangements of the sensor, if such a sensor can detect a movement of the tub 3 with respect to the housing 1.

Furthermore, the household appliance comprises a controller 10 which is electrically connected to electrical consumers, such as the motor 5, and measuring devices, such as the displacement sensor. The controller 10 is designed such that the control signals required for operating the household appliance are generated and that, with means included by the controller, the signals detected by the measuring appliances can be evaluated. Such a controller 10 may itself comprise or be connected to such an apparatus for determining an imbalance occurring in a drum of a domestic appliance for the care of laundry items caused by a distribution of the laundry items in an interior of the drum. Depending on the determined by the device for determining an imbalance dynamic and / or static imbalance, the controller 10 can generate control signals that affect the further program flow, in particular the spin operation with respect to the control and / or regulation of the rotational speed of the drum 8. Thus, for example Reduction of a drum speed when exceeding a predetermined unbalance limit for the determined dynamic and / or static imbalance possible to avoid excessive movements of the tub 3 and excessive mechanical stress.

In order to ensure a reliable control of a rotational speed n of the drum 8, in particular in a centrifugal operation, there is a particular interest in determining a static as well as a dynamic imbalance, which is caused by an uneven distribution of the laundry items in an interior of the drum.

In order to determine the static as well as the dynamic imbalance, in the present example a respective value of an amplitude of the path signal W of the deflection of the tub is determined in the present case at two different speeds n ₁ and n _{2 of} the drum. In this case, each value of the amplitude of the path signal W corresponds to a specific value of the imbalance, wherein this imbalance coincides only in a first approximation with the static imbalance. This is accomplished by allowing the tub 3 to generally move freely in six different degrees of freedom (x, y, z and rotation about x, y, z). That is, a detected path signal W is caused by the movement of the tub 3 in multiple degrees of freedom. In addition, the excitation of the tub 3 in a degree of freedom at the same time cause a movement of the tub 3 in a further degree of freedom. Since different oscillation parameters apply to the individual degrees of freedom of the oscillatable tub 3, typical amplitude curves are formed for the oscillation of the tub 3, depending on the type and magnitude of the excitation via the rotational speed n of the drum 8, ie the excitation frequency. Thus it is alone Observation of the course of the oscillation of any location vector of the tub 3 possible to determine the type or degree of freedom and the size of the excitation.

Accordingly, it is proposed according to the invention that the amplitude of a measured variable, in the present example of the path signal W, is determined at at least two different rotational speeds n ₁ and n ₂ . By comparing the two different values of the unbalance (1st approximation) at the two different rotational speeds n ₁ and n ₂ , the dynamic imbalance can be determined in the present case and thus the static imbalance can be specified.
Fig. 1 gives a curve f1 a speed n as a function of time t and a curve f2 of a path signal W as a function of time t again. At this point it should be mentioned that in the in Fig. 1 illustrated case, an unbalance-causing load in an axial center of the drum 8 is arranged. In contrast, in Fig. 2 a course f3 of the rotational speed n and a course f4 of the travel signal W as a function of the time t, it being mentioned that the unbalance-causing load is now arranged on an axial rear edge of the drum 8. As in the Fig. 1 and 2 can be seen in circles, a ratio V of a vibration amplitude of the path signal W at a rotational speed n ₁ of, for example 235 U / min to a vibration amplitude of the path signal W at a further speed n _2, for example, 300 U / min depending on the arrangement of the load or imbalance in the drum. The ratio V is thus significantly different in the case of the arrangement of the imbalance at the axial rear edge of the drum than in the case of the arrangement of the imbalance in the axial center of the drum. The ratio V can be defined in the simplest case as the quotient of the oscillation amplitude at the rotational speed n1 to the oscillation amplitude at the rotational speed n2 (V = W (n1) / W (n2).) Alternatively, the ratio V can also be determined by means of a difference quotient. Such a ratio V or a change in the oscillation amplitude can also be determined analogously for other ranges of the rotational speed n and / or taking into account a multiplicity of ranges of the rotational speed n For this purpose, the oscillation amplitudes W are determined at a number of different rotational speeds n of the drum 8, the number greater than or equal to the number of degrees of freedom of the imbalance to be determined. Fig. 3 gives an example course of an amplitude A of the path signal W as a function of the rotational speed n again. The amplitude A represents an average amplitude over at least half a period of the path signal W, wherein a distance between the envelope of the path signal W is considered for calculating the average amplitude. In the present case, the amplitude A represents a measure of the static unbalance (1st approximation).

To determine the static and the dynamic unbalance, a linear system of equations is formed in the present case. First, the amplitude A is determined for two different values of the rotational speed n, and then the static as well as the dynamic unbalance are determined as a function of the amplitude A and the rotational speed n. Where: $${\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="imgf0003.png"\; state="\{\{state\}\}">U</figure-callout>}}_{\mathrm{1.}\mathrm{N}\ddot{\mathrm{a}}\mathrm{approximation}}\mathrm{=}\mathrm{A}\mathrm{*}{\mathrm{U}}_{\mathrm{static}}\mathrm{+}\mathrm{B}\mathrm{*}{\mathrm{U}}_{\mathrm{dynamic}}\mathrm{,}$$

Here U ₁ denotes. Approximation of the unbalance obtained from the amplitude A, where U _static and U _{dynamic represents} the static or dynamic imbalance to be determined. A and B denote device-specific constants, which are set speed-specifically for the selected values of the rotational speed n. If the amplitude A or the unbalance (first approximation) is determined at two different rotational speeds n, then the dynamic and the static unbalance can be determined from a system of equations having two equations.

Claims (10)

1. Method for detecting an imbalance (U), which arises in a drum of a domestic appliance for the care of items of laundry and is produced by distribution of the items of laundry in an interior space of the drum, wherein at least one dynamic imbalance (U_dynamic) is determined, characterised in that in each instance a value of an amplitude (A) of a measurement variable (W), which characterises movement behaviour of a solution container arranged in the domestic appliance, is determined for at least two difference values of a rotational speed (n) of the drum and depending on the at least two values of the amplitude (A) the dynamic imbalance (U_dynamic) is ascertained by comparison of the values of the amplitude (A) for the at least two different rotational speeds.
2. Method according to claim 1, characterised in that a static imbalance (U_static) is ascertained in dependence on at least one value of the amplitude (A).
3. Method according to claim 1 or 2, characterised in that a travel signal (W), which characterises deflection of the solution container from a rest setting, and/or a speed and/or an acceleration of the solution container is or are selected as measurement variable.
4. Method according to any one of claims 1 to 3, characterised in that an equation system comprising at least two equations is formed and that the static and dynamic imbalances (U_static, U_dynatic) are ascertained on the basis of the equation system.
5. Method according to claim 4, characterised in that a linear equation system is selected as equation system.
6. Method according to claim 4 or 5, characterised in that at least two constants (A, B) of the equation system specific to rotational speed are fixed for the at least two selected values of the rotational speed (n).
7. Method according to any one of the preceding claims, characterised in that an increase and/or decrease in the rotational speed (n) is or are undertaken in dependence on the dynamic imbalance (U_dynamic).
8. Device for detecting an imbalance (U), which arises in a drum of a domestic appliance for the care of items of laundry and is produced by distribution of the items of laundry in an interior space of the drum, with imbalance determining equipment constructed for determining dynamic imbalance (U_static, U_dynamic) is determined, characterised in that the imbalance determining equipment is constructed for the purpose of determining in each instance a value of an amplitude (A) of a measurement variable (W), which characterises movement of a solution container arranged in the domestic appliance, for at least two different values of a rotational speed (n) of the drum and depending on the at least two values of the amplitude (A) ascertaining the dynamic imbalance (U_dynamic) by comparison of the values of the amplitude (A) for the at least two different rotational speeds.
9. Device according to claim 8, characterised in that the imbalance determining equipment is further constructed for the purpose of ascertaining a static imbalance (U_static) in dependence on at least one value of the amplitude (A).
10. Domestic appliance, particularly washing machine and/or washer/drier, for performing a method according to any one of claims 1 to 7, characterised in that a device according to one of claims 8 and 9 is included.

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