EP2467525B1 - Method for determining an imbalance of a washing drum in a washing machine in the spin dryer mode, drive apparatus and washing machine having a drive apparatus - Google Patents

Description

The invention relates to a method for determining an imbalance in a laundry drum of a washing machine after initiating a spin operation, in which the laundry drum is to accelerate to a predetermined spin speed. The laundry drum is driven by means of a drive motor, and to phase strands of a stator of the drive motor, an alternating electrical voltage is applied in each case, which is provided by an electrical DC link voltage using an inverter. The invention also relates to a drive device for driving a laundry drum of a washing machine and to a washing machine with such a drive device.

It is state of the art to determine the imbalance in a laundry drum in a washing machine after initiating a spin operation. Before the laundry drum is accelerated to the highest speed in the spin mode, the given imbalance should be checked again due to uneven distribution of the laundry items on the inner wall of the laundry drum. A method for determining the imbalance in the spin operation of a washing machine is for example from the document DE 102 34 053 C1 known. There is a fluctuation in the power consumption of the laundry drum driving and three-phase running drive motor evaluated, and the imbalance is determined depending on this fluctuation. The power consumption of the drive motor is calculated from measured values for a DC link voltage as well as from measured values for a DC link current.

So in the article according to the publication DE 102 34 053 C1 the calculation of the power absorbed by the drive motor depending on the DC link voltage and the DC link current, which are measured directly in the DC link, ie before feeding into the inverter or the inverter. The calculation of the power thus includes the losses occurring in the inverter, as well as the electrical power loss of a usually existing driver stage for the inverter. For that reason, as well as due the influence of the fluctuations of the AC supply voltage provided by the network on the amplitude of the DC link voltage, the power delivered to the motor and thus the imbalance can be determined only inaccurate in the prior art.

Another method for determining the imbalance in a laundry drum in a washing machine and a device of the washing machine for performing the method is out US 5677606 A known. Such a washing machine has a three-phase drive motor, to the phase strands of an AC voltage is applied, which is provided from an inverter. In order to determine the unbalance, in the known method the phase currents are measured, a difference between the measured phase currents and the mean value is formed and the number of times the difference is counted with respect to a predetermined limit value. An imbalance is detected by the method when the counted number exceeds a predetermined number.

It is an object of the invention to provide a solution, as the imbalance in a laundry drum of a washing machine after the initiation of a spin operation can be determined very accurately.

This object is achieved by a method with the features according to claim 1, by a drive device with the features of claim 14, as well as by a washing machine with the features according to claim 15. Preferred embodiments of the invention are subject matters of the dependent claims and the following description, and accordingly disclosed preferred embodiments of the invention according to one of the categories of method, drive device and washing machine in the context of technically possible always preferred embodiments of the invention according to the respective other categories correspond, and this even if this is not explicitly indicated in individual cases.

In a method according to the invention for determining an imbalance in a laundry drum of a washing machine after initiating a spinning operation in which the laundry drum is accelerated to a predetermined sliding speed is, the laundry drum is driven by a drive motor. At phase strands of a stator of the drive motor in each case an electrical alternating voltage is applied, which is provided by an electrical DC link voltage using an inverter. In at least one phase string of the stator, an electrical string current is measured, and the unbalance is determined as a function of measured values for the string current.

Accordingly, the phase current is measured in at least one phase phase of the drive motor; From the measured values for this string current, the imbalance in the washing drum is then determined. Furthermore, the current is measured directly on the drive motor. Thus, only the electric current actually absorbed by the drive motor is used to determine the imbalance. If the current in the DC link is measured, the losses occurring in the inverter can not be taken into account when determining the imbalance. Also, due to the influence of any, on the side of the electrical supply network - that is before a rectifier - occurring fluctuations in the AC supply voltage to the current of the current in the DC link exact determination of the imbalance based on this current can not be achieved. In contrast, the current flowing through a phase strand of the stator strand current provides an accurate statement about the actual power consumption and thus on the load or the torque of the drive motor, as well as the unbalance in the laundry drum. Any electrical losses occurring in the inverter, as well as the deviations and fluctuations in the AC supply voltage are not included in the determination of the imbalance; because the unbalance is determined advantageously due to the flowing only in the drive motor strand current.

In addition, during the determination of the imbalance of the drive motor in the centrifugal operation, an initial charge of the laundry drum determined prior to the initiation of the centrifugal operation, in particular since the beginning of the centrifugal operation, and / or one integrated since the beginning of the washing process, will also be present the drive motor delivered Energy taken into account. Namely, it is inferred in determining the imbalance in particular on the load or the torque of the drive motor. By taking into account the initial load when determining the imbalance, it is thus possible between a torque due to the initial load and the Distinguish torque due to the imbalance. In this case, the starting point is a washing program comprising a plurality of process sections, which has at least one washing process and one spinning operation, the washing process serving to clean and / or rinse laundry and smaller by operation at a low speed of the laundry drum, in particular one speed as the usual spin speed, characterized.

Furthermore, it is of particular advantage that such a method can be used during spin operation not only at low speeds of the laundry drum but also at higher speeds. In this case, a speed is less than or equal to the so-called resonance speed of the laundry drum at a low speed, wherein the resonance speed corresponds to the main resonant frequency of a vibrating mounted in the housing of the washing system, which comprises at least the laundry drum. Accordingly, a high speed is a speed that is significantly greater than the resonance speed, preferably in a range of twice to 5 times the resonance speed.

Preferably, the drive motor is a brushless DC motor (BLDC) or a permanent magnet synchronous motor. The drive motor may comprise three phase strings; then the inverter provides three AC voltages, namely one AC voltage for each phase phase of the drive motor. Such synchronous motors are characterized by high efficiencies compared to, for example, asynchronous motors. By a high efficiency of the electric motor can be made compact, so that advantages in terms of cost due to the material savings can be achieved. A major advantage of a brushless DC motor is the ability to measure the string current accurately and without much effort. The current measurement can be done, for example, by a control device that simultaneously controls the inverter. The control device can measure the phase current, and a microprocessor of the control device can evaluate the measured values for the current and determine the imbalance. With a brushless DC motor or permanent magnet-excited synchronous motor, the imbalance can thus be easily determined from the measured values for the phase current.

Preferably, phase currents in at least two phase phases, in particular in all phase phases, of the stator are measured and evaluated with regard to the imbalance of the laundry drum. In the case of a three-phase stator, measured values for preferably a total of three phase currents are then available for determining the imbalance. For example, the imbalance can be determined redundantly depending on the respective measured values of the phase currents, and the results of this determination can then be compared with one another. Additionally or alternatively, the imbalance depending on summarized measured values of at least two phase currents, in particular of all phase currents, are determined. For example, an energy and / or a power can be calculated from the measured values for the phase currents for determining the imbalance, as will be explained in more detail below.

A very robust and exact determination of the imbalance can be achieved if, at least at a predetermined time after the initiation of the centrifugal operation, an electrical energy output to the drive motor since a predetermined earlier time, in particular since the start of the centrifugal operation, from the measured values for the phase current is calculated. Then the imbalance can be determined depending on the value of the energy. For the calculation of the energy, the amplitude of the AC voltage applied to the phase string is preferably also used. This embodiment takes advantage of the fact that the electrical energy absorbed by the drive motor depends on the imbalance or the distribution of the laundry items within the laundry drum. The relationship is that the greater the imbalance or the more irregular the distribution of the laundry items on the inner wall of the laundry drum, the greater the load or the torque of the drive motor and thus the energy absorbed by the drive motor. If an initial loading of the laundry drum is known - it can be determined, for example, at the beginning of each washing process - then it can be deduced from the calculated energy on the load of the drive motor due to the uneven distribution of the laundry items in the laundry drum. For calculating the energy, the measured values of the strand flow determined since the start of the spinning operation can be stored, and the energy delivered to the drive motor since the start of the spinning operation can then be calculated from the stored measured values for the strand current. The evaluation of the energy delivered to the drive motor since the start of the spinning operation has the advantage over the evaluation of the measured values of the phase current that any fluctuations occurring in the course of the phase current are taken into account or included in the calculation of the energy. The energy can namely be calculated by integrating the current profile or a power curve. By integrating the occurring in the course of the string current, for example, due to an uneven distribution of the laundry items in the laundry drum fluctuations are taken into account, and the imbalance or the load of the drive motor can be accurately determined.

It has been found to be particularly advantageous if a time course of the energy delivered to the drive motor since a predetermined time after the initiation of the spinning operation, in particular since the start of the spinning operation, is determined; then the imbalance can be determined as a function of a gradient or of a gradient of this course. This means that the energy delivered to the drive motor is always integrated since the predetermined time, in particular since the initiation of the centrifugal operation, so that during the centrifuging operation a continuous course of the energy arises. This course is an increasing course, as the energy is added up and the total energy given to the drive motor gets bigger and bigger. This embodiment is based on the recognition that the slope of the course of the energy represents an exact measure of the imbalance; the greater the imbalance or the load of the drive motor due to unevenly distributed laundry items, the greater the gradient or the gradient of the course of the energy. The evaluation of the slope can be done, for example, that the slope is determined at a certain time after the start of the spinning operation and is compared with stored in a memory reference values for the slope. Depending on this comparison, a degree of imbalance can then be determined. For example, the stored reference values can be subdivided into at least two, in particular at least three, reference value ranges, and it can be checked in which of the reference value ranges the determined slope falls. If each of the reference value ranges is assigned to a specific degree of imbalance - for example "small imbalance", "average imbalance" and "large imbalance" - the degree of imbalance can thus be determined directly without much effort, and the further spinning operation can be carried out accordingly to be controlled.

Additionally or alternatively, an instantaneous power output to the drive motor can be calculated from the measured values for the phase current and preferably also from the amplitude of the alternating voltage applied to the phase strand. Then the imbalance can be determined depending on the calculated power. The fact that the greater the imbalance of the laundry drum is, the better more power is absorbed by the drive motor. At a predetermined point in time after the start of the spinning operation, therefore, the power can be calculated and compared with reference values stored in a memory. For example, the stored reference values can be subdivided into at least two, in particular at least three, reference value ranges, and it can be checked in which of the reference value ranges the calculated power value falls. If each of the reference value ranges is assigned to a specific degree of imbalance - for example, "small imbalance", "average imbalance" and "large imbalance" - the degree of imbalance can thus be determined directly without much effort, and the further spinning operation can be carried out accordingly to be controlled.

A progression of the electrical power delivered to the drive motor in the spin mode can be determined over time, and the unbalance can be determined as a function of a gradient or a gradient of this profile. The greater the imbalance or the load of the drive motor due to the imbalance, the greater the slope of the course of the power. By evaluating the slope can thus be determined whether the drive motor is loaded and thus an imbalance in the laundry drum is present or not. The slope of the course of the power can also be compared with reference values stored in a memory, and the unbalance can be determined depending on the result of this comparison.

The course of the power can also be evaluated for the duration of one revolution of the laundry drum, and depending on this course, the position of the imbalance in the laundry drum can be determined or an uneven distribution of the laundry within the laundry drum can be detected. It takes advantage of the fact that the imbalance of the laundry drum can be detected by means of a fluctuation in the course of the power for the duration of one drum revolution. The variation of this course then represents a direct measure of the distribution of imbalance in the laundry drum.

Additionally or alternatively, the profile of the phase current can be evaluated over time, and the unbalance can be determined depending on the course of the string current. For example, in this embodiment, a shape of an envelope of the Phase current can be evaluated. If there are high fluctuations in the course of the phase current or in the course of the envelope, this is a sign that there is an uneven distribution of the laundry items within the laundry drum. The course of the string current can also be evaluated for the duration of one revolution of the laundry drum, and depending on this course, the position of the imbalance in the laundry drum can be determined or an uneven distribution of the laundry items within the laundry drum can be detected. The imbalance of the laundry drum can therefore be detected by means of a fluctuation in the course of the strand current for the duration of a drum revolution. The variation of this course then represents a direct measure of the distribution of imbalance in the laundry drum.

As already stated, reference values can be stored in a memory and the imbalance can be determined as a function of a comparison of the determined and / or calculated variable with the stored reference values. For example, the measured values for the phase current and / or the energy values and / or the slope of the curve of the energy and / or the power values and / or the slope of the curve of the power can be compared with respectively assigned reference values stored in a memory. Depending on this comparison, a degree of imbalance can then be determined. For example, the stored reference values can be subdivided into at least two, in particular at least three, reference value ranges, and it can be checked in which of the reference value ranges the measured and / or calculated quantity falls. If each of the reference value ranges is assigned to a specific degree of imbalance - for example, "small imbalance", "average imbalance" and "large imbalance" - the degree of imbalance can thus be determined directly without much effort, and the further spinning operation can be carried out accordingly to be controlled.

Thus, the further spin operation can be controlled depending on a degree of the detected unbalance. If the imbalance in the laundry drum is large, the laundry drum can not be accelerated to the predetermined spin speed, as this could lead to an uncontrolled vibration of the washing machine. This is especially true for high spin speeds of the laundry drum greater than 800 U / min. For this reason, in particular safety measures are taken by which uncontrolled vibrations of the washing machine can be avoided. It can for Example, the predetermined spin speed to which the laundry drum is to accelerate, then reduced when the determined imbalance reaches a predetermined first degree - for example, "medium imbalance". If the determined imbalance is not yet critical - but large enough to put the washing machine into undesired vibration at the given spin speed of the laundry drum - so the laundry drum can be accelerated to a lower speed. The desired goal of being able to carry out the centrifugal operation can therefore be achieved with a reduced speed in this embodiment.

This can be implemented, for example, in such a washing process: A microprocessor of the washing machine initiates a spin operation of a washing process. In this spin mode, the laundry drum should be accelerated to a spin speed of 1200 rpm. The microprocessor controls an inverter, which in each case provides an electrical AC voltage to each phase strand of a permanent magnet synchronous motor, namely from a DC link voltage. The washing drum is driven by the permanent magnet synchronous motor. Immediately after initiating the spin operation, the microprocessor begins to calculate the electrical energy delivered to the permanent magnet synchronous motor. For example, the microprocessor calculates the energy at regular intervals, for example at intervals of about 10 ms. In each calculation, the microprocessor takes into account the energy delivered to the motor since the start of the spinning operation, that is, the energy is integrated in each case. This results in a time course of the energy delivered to the engine in each case since the initiation of the spinning operation. After a predetermined period of time has elapsed after initiation of the spinning operation, the microprocessor determines an increase in the time profile of the energy and / or the absolute value of the energy delivered since the start of the spinning operation at this time. This slope and / or the absolute value of the energy is compared by the microcontroller with reference values for the slope or energy stored in a memory. The microcontroller checks in which reference value range the determined slope and / or the absolute value of the energy falls / falls. The microcontroller also takes into account a start load, which was determined at the beginning of the washing process. Thus, the microcontroller can judge what imbalance in the laundry drum or which load of the drive motor is given. Recognize the Microprocessor "average imbalance", the spin speed of 1200 rev / min is reduced to, for example, 800 rpm.

If the determined imbalance reaches a predetermined second degree - for example, "large imbalance" - then the laundry drum can be completely decelerated. Then the spin operation is interrupted for a short time, and the laundry drum is braked to 0 rev / min and accelerated again. The laundry items are thus redistributed in the laundry drum, and the imbalance is determined after re-accelerating the laundry drum again. This embodiment has the advantage that the washing machine is not put into an uncontrolled oscillatory movement, dangerous conditions of the washing machine are avoided.

A drive device according to the invention for driving a laundry drum of a washing machine comprises a drive motor for driving the laundry drum. The drive device also includes an inverter coupled to phase strings of a stator of the drive motor, to the input of which a DC link voltage can be applied and which is designed to provide in each case an electrical AC voltage for the phase phases of the stator. A controller controls the inverter. The control device is designed to measure an electrical string current in at least one phase strand of the stator, even before the initiation of the centrifugal operation, an initial loading of the laundry drum and / or an integrated, in particular since the beginning, of the previous spin mode preceded washing process, to the drive motor To determine energy and to determine an imbalance in the laundry drum depending on measured values for the strand flow and depending on the initial load and / or the integrated during the washing process energy.

The preferred embodiments presented with reference to the method according to the invention and their advantages apply correspondingly to the drive device according to the invention.

A washing machine according to the invention comprises a drive device according to the invention or a preferred embodiment thereof.

Further features of the invention will become apparent from the claims, the figures of the accompanying drawings and the following description of the figures. All the features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respectively indicated combination but also in other combinations or also alone.

Fig. 1

in schematischer und höchstabstrakter Darstellung eine Waschmaschine gemäß einer Ausführungsform veranschaulicht, wobei die Waschmaschine eine Antriebsvorrichtung gemäß einer Ausführungsform aufweist;

Fig. 2

jeweils einem anderen Grad einer Unwucht zugeordnete zeitliche Verläufe einer an einen Antriebsmotor der Antriebsvorrichtung abgegebenen elektrischen Energie veranschaulicht; und

Fig. 3

einen zeitlichen Ausschnitt der Verläufe gemäß Fig. 2 veranschaulicht, wobei anhand der Verläufe ein Verfahren gemäß einer Ausführungsform näher erläutert wird.

The invention will now be described with reference to individual preferred embodiments and with reference to the drawings, wherein

Fig. 1

in schematic and highly abstract representation of a washing machine according to an embodiment illustrated, wherein the washing machine comprises a driving device according to an embodiment;

Fig. 2

each time associated with a different degree of imbalance shows a course of an output to a drive motor of the drive device electrical energy; and

Fig. 3

a temporal excerpt of the courses according to Fig. 2 illustrated, with reference to the courses, a method according to an embodiment is explained in more detail.

An in Fig. 1 1 shows a drive device 2 which serves for mechanically driving a laundry drum 3 arranged in the washing machine 1. The laundry drum 3 is designed to receive laundry items 4. The drive device 2 comprises a drive motor 5 and a circuit arrangement 6 for operating the drive motor 5. The drive motor 5 is in the embodiment a permanent magnet synchronous motor or a brushless DC motor and comprises three phase strands 7, 8, 9. The phase strand 7 is connected to a first terminal 10 of Drive motor 5 electrically connected; the phase strand 8 is connected to a second terminal 11 of the drive motor 5, and the phase strand 9 is connected to a third electrical terminal 12 of the drive motor 5.

The circuit arrangement 6 comprises a circuit input 13 with a first and a second input connection 14, 15, between which an electrical supply alternating voltage U _v is applied. The AC supply voltage U _v is provided by an electrical supply network.

The circuit arrangement 6 also has three output terminals 16, 17, 18. The first output terminal 16 is connected to the first terminal 10 of the drive motor 5, the second output terminal 17 is connected to the second terminal 11 of the drive motor 5, and the third output terminal 18 is connected to the third terminal 12 of the drive motor 5.

With the input terminals 14, 15 is a in Fig. 1 only schematically illustrated power supply 19 coupled, the - as out Fig. 1 shows - may have a bridge rectifier. The power supply 19 may also comprise other components, such as in particular a line filter and the like.

The power supply 19 provides between its output terminals 20, 21 an electrical DC link voltage U _z . In this case, a reference potential B is provided at the output terminal 21. Between the output terminals 20, 21 of the power supply 19, that is parallel to the power supply 19, an intermediate circuit capacitor 22 is connected. Thus, the DC link voltage U _z provided by the power supply unit 19 is applied to the DC link capacitor 22.

Parallel to the DC link capacitor 22, a voltage divider 23 is connected, which has two ohmic resistors 24 in the embodiment. Between the ohmic resistors 24 a Abgriffpol 25 is arranged, at which a voltage U _s can be tapped. The amplitude of the voltage U _s provided by the voltage divider 23 represents a measure of the amplitude of the DC link voltage U _z .

Parallel to the power supply 19, the intermediate circuit capacitor 22 and the voltage divider 23, an inverter or an inverter 26 is connected. The inverter 26 includes a first circuit branch 27, a second circuit branch 28, and a third circuit branch 29. The first, second, and third circuit branches 27, 28, 29 are coupled on the one hand to the output terminal 20 of the power supply 19 and on the other hand to the reference potential B or the output terminal 21 of the power supply 19. The first circuit branch 27 comprises two electrical switches 30, 31; a pole 32 arranged between the electrical switches 30, 31 is coupled to the first output terminal 16 of the circuit arrangement 6. The second circuit branch 28 has correspondingly two electrical switches 33, 34; a pole 35 arranged between the electrical switches 33, 34 is coupled to the second output terminal 17 of the circuit arrangement 6. Accordingly, the third circuit branch 29 has two electrical switches 36, 37; a pole 38 provided between the electrical switches 36, 37 is coupled to the third output terminal 18 of the circuit arrangement 6 and thus to the third terminal 12 of the drive motor 5. The electrical switches 30, 31, 33, 34, 36, 37 in the exemplary embodiment bipolar transistors with insulated gate electrodes (IGBT).

The circuit arrangement 6 furthermore comprises a control device 39, which in the exemplary embodiment is a microprocessor. The control device 39 serves to drive the inverter 26, and more precisely the electrical switch 30, 31, 33, 34, 36, 37.

By appropriate control of the inverter 26, the control device 39, the speed of the drive motor 5 and thus control the speed of the laundry drum 3 and / or regulate. The control device 39 can also measure the intermediate circuit DC voltage U _z , namely, depending on the electrical voltage U _s provided by the voltage divider 23. The control device is coupled to the tapping pole 25 of the voltage divider 23. Thus, the control device 39 detects the voltage U _s and can thus infer the DC link voltage U _z .

In order to drive the drive motor 5, in each case an electrical alternating voltage U ₁₂ , U ₂₃ , U ₁₃ between the terminals 10 and 11 or 11 and 12 or 10 and 12, that is applied to the phase strands 7, 8, 9 of the drive motor 5. The amplitude of these voltages U ₁₂ , U ₂₃ , U ₁₃ is known to the control device 39; namely, the control device 39 detects the intermediate circuit DC voltage U _z and controls the inverter 26.

The control device 39 also detects phase currents I ₁ , I ₂ , I ₃ , which flow via the phase strands 7, 8, 9 of the drive motor 5. For this purpose, the control device 39 is coupled to a tapping pole 41 of the first circuit branch 27 arranged between the electrical switch 31 and an ohmic resistor 40 connected in series therewith. The control device 39 is also coupled to a tapping pole 42, which is arranged between the electrical switch 34 and a series-connected ohmic resistor 43 in the second circuit branch 28. Furthermore, the control device 39 is coupled to a tapping pole 44, which is arranged between the electrical switch 37 and a series-connected ohmic resistor 45 in the third circuit branch 29. Thus, the control device 39 can detect the respective current intensity of the phase currents I ₁ , I ₂ , I ₃ , which flow via the phase strands 7, 8, 9 of the drive motor 5.

A method according to an embodiment will now be described with reference to FIGS FIGS. 2 and 3 explained in more detail. The method is used to determine an imbalance in the laundry drum 3, which may occur due to uneven distribution of the laundry items 4 on an inner wall of the laundry drum 3 in a centrifugal operation. In the spin mode, the drum 3 is to be accelerated to a predetermined spin speed - for example to a speed of 1200 rpm - to dewater the laundry items 4. After starting the washing process, that is before the initiation of the spinning operation, the initial loading of the laundry drum 3, that is to say the initial mass of the laundry items 4, is determined by the control device 39. After the initiation of the spinning operation, the load or the torque of the drive motor 5 and thus the imbalance in the laundry drum 3 are then determined as a function of the measured values for the phase currents I ₁ , I ₂ , I ₃ and depending on the determined initial load of the laundry drum 3.

The control device 39 collects all measured values for the phase currents I ₁ , I ₂ , I ₃ after the initiation of the centrifugal operation. From these measured values for the phase currents I ₁ , I ₂ , I ₃ , as well as from the amplitude of the voltages U ₁₂ , U ₂₃ , U ₁₃ , the control device 39 calculates an electrical energy E delivered to the drive motor 5. This energy E can be used by the control device 39 also in the washing mode, so before the initiation of the spin operation calculate. For the determination of the imbalance in the laundry drum 3, however, the control device 39 preferably takes into account only the after measured values for the phase currents I ₁ , I ₂ , I ₃ recorded in the initiation of the spinning operation.

Regarding Fig. 2 The spinning operation starts at a time t ₀ . At this time t ₀ , the energy E delivered to the drive motor 5 in the spinning mode is still 0 Wh; the drive motor 5 has not taken up any energy E in the spin mode. During the spinning operation, the control device 39 continuously calculates, for example, at intervals of 10 ms, the energy E delivered to the drive motor 5 since the start of the spinning operation, that is to say since the time t _0. The course of the energy E increases over time t during the spin operation. In other words, the energy E is integrated in the spinning mode, so that at the end of the spinning operation the total energy E recorded in the spinning operation by the drive motor 5 is calculated.

The control device 39 thus determines a time course of the energy E during the spin operation. Depending on the course of the energy E, the control device 39 then determines the imbalance in the laundry drum 3; At the same time, the control device 39 evaluates a gradient ΔE / Δt of the course of the energy E. In Fig. 2 For example, different slopes .DELTA.E / .DELTA.t the curves of the energy E are shown. A slope ΔE / Δt of a first course V ₁ corresponds to a large degree of imbalance; the energy E increases relatively quickly or the drive motor 5 has absorbed a relatively large amount of energy E since the start of the spinning operation. The slope .DELTA.E / .DELTA.t of a relatively flat waveform V _{2 of} the energy E corresponds to a small degree of imbalance; the drive motor 5 has absorbed comparatively little energy E since the time t ₀ or the energy increases relatively slowly.

The determination of the unbalance can be made such that the laundry drum 3 is first accelerated to a lower speed of, for example, 100 rpm to 300 rpm before it is accelerated to the spin speed. At this lower rotational speed, the control device 39 can then evaluate the energy E, namely in particular the slope ΔE / Δt of the course of the energy E.

The control device 39 compares the determined slope .DELTA.E / .DELTA.t with stored in a memory reference values for the slope .DELTA.E / .DELTA.t. For example, different reference value ranges can be stored in the memory, the control device 39 then checks in which of the reference value ranges the determined slope ΔE / Δt falls. Each reference value range can be assigned one degree of imbalance, namely, for example, "low imbalance", "average imbalance" and "large imbalance".

Redundant or alternatively, the control device 39 can also evaluate the absolute values of the energy E (measured in watt-hours) and determine the unbalance depending on this. In Fig. 3 is a section of the curves of the energy E over the time t shown. In the memory reference ranges R1, R2, R3 may be stored, which are each assigned to a different degree of imbalance. The reference value range R1 can be assigned to a "small imbalance", the reference value range R2 to a "middle imbalance", and the reference value range R3 to a "large imbalance". At a certain time after the initiation of the spin operation, the control device 39 evaluates the absolute value of the energy E. The control device 39 checks in which of the value ranges R1, R2, R3 the calculated value of the energy E falls. Thus, the control device 39 can directly infer the degree of imbalance.

Different embodiments may be provided for determining the unbalance: The control device 39 may first accelerate the laundry drum 3 to a first rotational speed of, for example, 100 rpm. At this speed, the control device 39 can calculate the energy E delivered to the drive motor 5 since the start of the spinning operation. The control device 39 can then check in which of the reference value ranges R1, R2, R3 the calculated value of the energy E falls. However, the determination of the unbalance can also be such that the control device 39 initially accelerates the drum 3 to a predetermined speed of, for example, 100 rpm and from this speed begins to calculate the energy E. From this speed, the control device 39 can then accelerate the laundry drum 3 to a predetermined higher speed of, for example, 200 rpm and calculate the energy E delivered to the drive motor 5 during this acceleration. Thus, the energy E can be calculated and used to determine the unbalance, which is delivered to the drive motor 5 during a time interval during which the laundry drum 3 is accelerated from a first predetermined speed to a second predetermined speed. Then the control device 39 can check in which reference value range R1, R2, R3 the calculated value of the energy E falls.

Redundant or alternatively, the control device 39 can also evaluate the measured values for the phase currents I ₁ , I ₂ , I ₃ and determine the imbalance in the laundry drum 3 as a function of this evaluation. For example, temporal courses of the phase currents I ₁ , I ₂ , I ₃ can be analyzed, in particular an envelope of these courses can be evaluated. The imbalance can then be determined as a function of fluctuations in these courses. It can also be provided here that the course of at least one of the phase currents I ₁ , I ₂ , I ₃ analyzed for the duration of a drum revolution and the imbalance is determined depending on this course within a drum revolution.

Redundant or alternatively, the control device 39 can calculate and evaluate an electric power delivered to the drive motor 5 in the spin mode, namely from the measured values for the phase currents I ₁ , I ₂ , I ₃ . For example, a slope of a time history of the power may be calculated and compared with reference values stored in the memory. Depending on this comparison, in particular depending on in which reference value range the determined slope falls, then the imbalance can be determined. The course of the electrical power can also be analyzed for the duration of a drum revolution, and the unbalance can then be determined as a function of fluctuations in this course within one drum revolution.

Overall, therefore, a method is provided with which the imbalance in a laundry drum 3 a washing machine 1 or the mechanical load of the laundry drum 3 driving drive motor 5 can be determined in the spin mode. Phase currents I ₁ , I ₂ , I _{3 of} the drive motor 5 are measured, and the imbalance is determined as a function of the measured values for the phase currents I ₁ , I ₂ , I ₃ . For example, an electric energy E outputted to the drive motor 5 since a predetermined time after initiating the spin operation, particularly since the start of the spin operation, may be calculated, and the unbalance may be determined depending on the calculated value of the energy E. A slope ΔE / Δt of a time profile of the energy E can be used as a measure of the imbalance or for a torque of the drive motor 5. In this way, it is possible to accurately determine the imbalance in the washing drum 3, and appropriate safety measures in the spin mode can be taken. For example, the originally determined spin speed to which the laundry drum 3 is to be accelerated in the spin mode can be reduced or it can be interrupted the spin operation and the laundry items 4 can be redistributed in the laundry drum 3.

The imbalance can also be determined sequentially or continuously during the further course of the shearing operation in one of the above-mentioned manner. Here by can be determined even at higher speeds, whether the previously determined unbalance has changed and, if necessary, adapt to the determined at higher speed unbalance before reaching the spin speed. For example, a previously determined depending on the determined imbalance spin speed can be reduced when the imbalance has become greater, or the fixed spin speed are increased when the imbalance has decreased. <B> LIST OF REFERENCES </ b> 1 Washing machine 2 driving device 3 washing drum 4 laundry 5 drive motor 6 circuitry 7 phase conductor 8th phase conductor 9 phase conductor 10 connection 11 connection 12 connection 13 circuit input 14 input port 15 input port 16 output port 17 output port 18 output port 19 power adapter 20 output port 21 output port 22 Link capacitor 23 voltage divider 24 Ohmic resistances 25 Abgriffpol 26 inverter 27 circuit branch 28 circuit branch 29 circuit branch 30 switch 31 switch 32 pole 33 switch 34 switch 35 pole 36 switch 37 switch 38 pole 39 control device 40 Ohmic resistance 41 Abgriffpol 42 Abgriffpol 43 Ohmic resistance 44 Abgriffpol 45 Ohmic resistance U _v AC supply voltage U _z Intermediate circuit voltage U _s tension U ₁₂ , U ₂₃ , U ₁₃ AC voltages I ₁ , I ₂ , I ₃ phase currents to time e energy AE / .DELTA.t pitch V ₁ , V ₂ course R1, R2, R3 Reference ranges

Claims (15)

1. Method of determining an imbalance in a laundry drum (3) of a washing machine (1) after initiation of spinning operation, in which the laundry drum (3) is to be accelerated to a predetermined spinning rotational speed, wherein the laundry drum (3) is driven by means of a drive motor (5), a respective electrical alternating voltage (U₁₂, U₂₃, U₁₃) provided from an electrical intermediate circuit direct voltage (U_z) with the assistance of an inverter (26) is applied to each phase (7, 8, 9) of a stator of the drive motor (5), an electrical phase current (I₁, I₂, I₃) is measured in at least one phase (7, 8, 9) of the stator and the imbalance is determined in dependence on measurement values for the phase current (I₁, I₂, I₃), characterised in that even before initiation of the spinning operation an initial loading of the laundry drum and/or an energy delivered to the drive motor and integrated during, particularly since the start of, a washing process preceding the spinning operation is or are determined and in addition the imbalance is determined in dependence on the initial loading and/or the energy integrated during the washing process.
2. Method according to claim 1, characterised in that the drive motor (5) is a brushless direct-current motor, particularly with three phases (7, 8, 9).
3. Method according to claim 1 or 2, characterised in that a respective electrical phase current (I₁, I₂, I₃), is measured in at least two phases (7, 8, 9), particularly in all phases (7, 8, 9), of the stator and the imbalance is determined in dependence on the measurement values for the phase currents (I₁, I₂, I₃).
4. Method according to any one of the preceding claims, characterised in that at at least one predetermined instant after initiation of the spinning operation an electrical energy (E) delivered to the drive motor (5) since a predetermined earlier instant (to) after initiation of the spinning operation, particularly since initiation of the spinning operation, is calculated from the measurement values for the phase current (I₁, I₂, I₃) and the imbalance is determined in dependence on the electrical energy (E).
5. Method according to any one of the preceding claims, characterised in that a plot (V₁, V₂) of an electrical energy (E) delivered to the drive motor (5) since a predetermined instant (to) after initiation of the spinning operation, particularly since initiation of the spinning operation, over time (t) is determined from the measurement values for the phase current (I₁, I₂, I₃) and the imbalance is determined in dependence on a gradient (ΔE/Δt) of the plot.
6. Method according to any one of the preceding claims, characterised in that an instantaneous electrical power delivered to the drive motor (5) is calculated from the measurement values for the phase current (I₁, I₂, I₃) and the imbalance is determined in dependence on the electrical power.
7. Method according to claim 6, characterised in that a plot of the electrical power, which is delivered to the drive motor (5) in spinning operation, over time (t) is determined and the imbalance is determined in dependence on a gradient of the plot.
8. Method according to any one of the preceding claims, characterised in that a plot of the phase current (I₁, I₂, I₃) over time (t) is evaluated and the imbalance is determined in dependence on the plot, particularly in dependence on an envelope curve of this plot.
9. Method according to any one of the preceding claims, characterised in that the measurement values for the phase current (I₁, I₂, I₃) and/or the values of a magnitude obtained therefrom are compared with reference values filed in a memory and the imbalance is determined in dependence on the result of this comparison.
10. Method according to claim 9, characterised in that the filed reference values are subdivided into at least two, particularly into at least three, reference value ranges respectively associated with a degree of imbalance and in the determination of the imbalance it is checked in which of the value ranges a measurement value of the phase current (I₁, I₂, I₃) and/or a value of the magnitude obtained therefrom lies or lie.
11. Method according to any one of the preceding claims, characterised in that the spinning operation is controlled in dependence on a degree of the determined imbalance.
12. Method according to claim 11, characterised in that the predetermined spinning rotational speed to which the laundry drum is accelerated is reduced when the imbalance reaches a predetermined first degree.
13. Method according to claim 11 or 12, characterised in that the laundry drum (3) is fully braked when the imbalance reaches a predetermined second degree.
14. Drive device (2) for driving a laundry drum (3) of a washing machine (1), comprising:

    - a drive motor (5) for driving the laundry drum (3),

    - an inverter (26), which is coupled with phases (7, 8, 9) of a stator of the drive motor (5) and to the input of which an intermediate circuit direct voltage (U_z) can be applied, the inverter being constructed for providing a respective electrical alternating voltage (U₁₂, U₂₃, U₁₃) for each of the phases (7, 8, 9) from the intermediate circuit direct voltage (U_Z), and

    - a control device (39) for controlling the inverter (26), the control device being constructed to measure an electrical phase current (I₁, I₂, I₃) in at least one phase (7, 8, 9) of the stator and to determine an imbalance in the laundry drum (3) in dependence on measurement values for the phase current (I₁, I₂, I₃),

    characterised in that the control device (39) is further constructed for the purpose of determining even before initiation of the spinning operation an initial loading of the laundry drum and/or an energy delivered to the drive motor and integrated during, particularly since the start of, a washing process preceding the spinning operation and for additionally determining the imbalance in dependence on the initial loading and/or the energy integrated during the washing process.
15. Washing machine (1) with a drive device (2) according to claim 14.

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