EP2221412B1 - Method for monitoring a load in a laundry drum and/or a drying level of laundry items and corresponding switching assembly - Google Patents

Abstract

The method involves controlling an electric motor i.e. permanent magnet excited synchronous motor, using a control device by applying electric voltage at a winding of a stator of the motor. Electric current flowing across the winding is measured by the control device. Energy (delta E) supplied to the electric motor is estimated based on the measured current. Drying level of laundry and/or loading of a drum is inferred based on distribution of energy over time. The drum is driven by the electric motor. An independent claim is also included for a circuit arrangement for monitoring loading of a drum and/or drying level of laundry in the drum.

Description

The invention relates to a method for monitoring a load of a laundry drum of a tumble dryer, see, for example DE19832292A1 and / or for monitoring a degree of drying of items of laundry introduced into the laundry drum, wherein the laundry drum is driven by means of an electric motor having a stator with at least one winding. The invention further relates to a corresponding circuit arrangement and a tumble dryer with such a circuit arrangement.

The term "tumble dryer" also includes a washer-dryer which is used for washing and drying items of laundry.

In a tumble dryer, it is of great importance to be able to predict the remaining drying time required for drying the laundry items. If the remaining drying time is determined, then a time at which the drying of laundry is stopped can be predicted. The drying time of the laundry is known to be related to the loading of the laundry drum. At the beginning of each drying process, this load is made up of the dry mass of the laundry items brought into the laundry drum and the mass of water, ie. H. the mass caused by the moisture of the laundry items.

It is an object of the invention to provide a method, a circuit arrangement and a corresponding dryer, in which, which and which an accurate monitoring of the loading of the laundry drum and / or the degree of drying of the laundry is possible.

This object is achieved by a method, a circuit arrangement and a tumble dryer with the features of the respective independent claim. Preferred embodiments of the invention are articles dependent claims and the following description, wherein preferred embodiments of the invention in one of the categories process, circuit arrangement and dryer always preferred embodiments of the invention in the respective other categories correspond, and this even if it is not explicitly indicated herein ..

In the method according to the invention, a loading of a laundry drum of a tumble dryer and / or a degree of drying of laundry items introduced into the laundry drum are monitored. The laundry drum is driven by means of an electric motor which has a stator with at least one electrical winding. In the method, the electric motor is controlled by means of a control device by applying electrical voltage to the at least one winding of the stator. An electric current flowing through the at least one winding when the electric motor is driven is measured by means of the control device, and conclusions are drawn as to the degree of drying of the laundry items and / or the loading of the drum depending on measured values of the current.

The invention is thus based on the finding that an electric current flowing in the winding of the stator when the electric motor is driven constitutes a measure of the loading of the laundry drum and thus a measure of the degree of drying of the laundry items. Depending on the measured values of the current flowing through the winding of the stator, the loading of the laundry drum and the degree of drying of the laundry items can be determined particularly accurately. It can thus be accurately determined or even regulated a remaining drying time, which is required for drying the laundry.

Depending on the measured values of the current, an energy delivered to the electric motor can be calculated. Then it is possible to deduce the degree of drying of the items of laundry and / or the loading of the drum as a function of a progression of the energy over time. A power delivered to the electric motor, ie the energy per unit time, depends directly on the load of the laundry drum or on the moment of inertia of the same. This means that in wet laundry more power must be delivered to the electric motor than dry laundry. Does the power delivered to the electric motor no longer change? so it is an indication that the laundry is already dry. In a time course of the energy delivered to the electric motor, it can be seen by a constant slope of the course.

With regard to the measurement of the current, it has proved to be advantageous if the laundry drum is driven by means of a permanent-magnet synchronous motor whose rotor carries at least one permanent magnet. The speed of such synchronous motors can be particularly simple, z. B. by means of an inverter, control or regulate. Thus, the speed behavior of the electric motor can be controlled depending on the respective current degree of drying of the laundry items and / or the current loading of the drum. At least two control scenarios are provided here: The speed behavior of the electric motor can be regulated with regard to the remaining drying time required for drying the laundry items. Alternatively or additionally, the speed behavior with respect to a power consumption of the electric motor can be controlled. These two control scenarios can be made available to an operator when operating the tumble dryer, for example. It may, for example, be such that the operator defines a point in time at which a drying process is to be ended. Then, the speed behavior of the electric motor is controlled by the control device so depending on the measured values of the current that on the one hand the drying process is terminated at this time and on the other hand, the power consumption of the electric motor is minimized.

• Beschleunigen der Wäschetrommel auf eine vorbestimmte erste Drehzahl;
• Rotieren der Wäschetrommel bei der ersten Drehzahl während eines vorbestimmten ersten Zeitintervalls, insbesondere für die gesamte Zeitdauer des ersten Zeitintervalls;
• Abbremsen der Wäschetrommel;
• Beschleunigen der Trommel auf eine vorbestimmte zweite Drehzahl;
• Rotieren der Wäschetrommel bei der zweiten Drehzahl während eines vorbestimmten zweiten Zeitintervalls, insbesondere für die gesamte Zeitdauer des zweiten Zeitintervalls.

In a preferred embodiment of the method according to the invention, the driving of the electric motor comprises the following steps:

• Accelerating the laundry drum to a predetermined first speed;
• Rotating the laundry drum at the first speed during a predetermined first time interval, in particular for the entire duration of the first time interval;
• Braking the laundry drum;
• Accelerating the drum to a predetermined second speed;
• Rotating the laundry drum at the second speed during a predetermined second time interval, in particular for the entire time period of the second time interval.

In this case, a difference between a measured value of the current detected during the first time interval and a measured value of the current detected during the second time interval is preferably calculated, and depending on this difference, conclusions are drawn as to the degree of drying of the laundry items and / or the loading of the drum. This is based on the recognition that the loading of the laundry drum changes during a drying process with time, as the laundry items lose moisture - the mass of the laundry items approaches the dry mass. Then during the drying process, less and less torque is required to drive the laundry drum or the moment of inertia of the laundry drum is getting smaller. Since the motor current is proportional to the torque, the measured values of the current flowing through the winding of the stator become ever smaller during the drying process. In this way, the change in the loading of the laundry drum and thus the change in the degree of drying can be monitored. If the measured values of the current change only slightly or even no longer, it is an indication that the items are already dry.

In particular, a difference between an average of the current intensity during the first time interval and an average value of the current during the second time interval is calculated, and depending on this difference, the degree of drying of the laundry items and / or the loading of the drum is deduced Accuracy of the monitoring of the loading and / or the degree of drying. Current peaks that may possibly occur in the course of the current are compensated for by the formation of the mean values.

It is also possible to measure an electrical current which, in a generator operation of the electric motor, ie when the laundry drum is being decelerated, flows over the winding of the stator. This current can be measured in the generator mode by means of the control device, and depending on the measured values of this current can be deduced the loading of the laundry drum. The loading of the laundry drum can thus be determined redundantly, depending on the current in motor operation and generator operation, and the two results can be compared.

Depending on the measured values of the motor current during engine operation, an initial load of the laundry drum can also be determined. For this purpose, the current flowing through the winding of the stator during a first driving of the electric motor during a drying process or drying program - d. H. during a time interval of a first acceleration and rotation of the drum - measured. Then, the initial load of the laundry drum can be determined depending on these measured values of the current. The drying time required for drying the laundry items can thereby be estimated. In addition, it is thus achieved that an overload of the laundry drum can be detected and the operator can be signaled. It is preferably provided that when the initial load exceeds a predetermined value, a warning signal, eg. B. an optical or an acoustic signal is output.

Furthermore, a phase delay between the phase of the voltage applied to the at least one winding of the stator and the phase of the measured current can be calculated, and depending on the phase delay, the degree of drying of the laundry items and / or the loading of the drum can be deduced.

The detected measured values of the current and / or the calculated energy and / or the phase delay can be compared with a characteristic stored in a memory. Values for the loading of the laundry drum and / or for the degree of drying of the laundry items can thus be read from a characteristic curve. Another possibility here is a mathematical model in which the values for the loading of the laundry drum and / or the degree of drying of the laundry items are calculated on the basis of a mathematical formula depending on the detected measured values of the current and / or the energy and / or the phase delay.

A circuit arrangement according to the invention is designed for monitoring the degree of dryness of laundry items introduced in a laundry drum of a tumble dryer and / or for monitoring a loading of the drum. The circuit arrangement comprises an electric motor whose stator has at least one winding which is coupled to a control device. The control device is for measuring a current flowing through the at least one winding and the current Detecting the degree of drying of the laundry items and / or the loading of the drum is formed depending on the detected measured values of the current.

The invention also includes a clothes dryer, which has a circuit arrangement according to the invention.

Further advantages of the invention will become apparent from the claims, the figures of the accompanying drawings and the following description of the figures. 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 in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

Fig. 1

ein Blockschaltbild einer Schaltungsanordnung;

Fig. 2

einen zeitlichen Verlauf eines über eine Wicklung eines Stators eines Elektromotors eines Wäschetrockners fließenden Stromes, wobei anhand des Verlaufs ein besonderes Verfahren näher erläutert wird; und

Fig. 3

einen zeitlichen Verlauf einer an den Elektromotor abgegebenen Energie während eines Trocknungsprozesses bzw. Trocknungsprogrammes, wobei anhand dieses Verlaufs ein besonderes Verfahren näher erläutert wird.

The invention will now be described with reference to a preferred embodiment and with reference to the accompanying drawings. Show:

Fig. 1

a block diagram of a circuit arrangement;

Fig. 2

a time course of a current flowing through a winding of a stator of an electric motor of a tumble stream, wherein a specific method is explained in more detail with reference to the course; and

Fig. 3

a time course of an energy delivered to the electric motor during a drying process or drying program, with reference to this course, a special method is explained in more detail.

In Fig. 1 a block diagram of a circuit 1 is shown. The circuit arrangement 1 comprises a power supply unit 2 which has, for example, a bridge rectifier. The power supply 2 is connectable to a power supply network. By means of the power supply 2, a rectified electrical voltage is provided. The circuit arrangement 1 furthermore has an inverter or inverter 3 with a plurality of insulated gate bipolar transistors. In particular, the inverter 3 comprises six such bipolar transistors. The inverter 3 is controlled by a control unit 4. The inverter 3 and the control unit 4 together form a control device.

The circuit arrangement 1 also includes a permanent-magnet synchronous motor 5, the rotor carries permanent magnets and the stator is designed to be three-phase. The stator thus has three windings 6 in the example. The windings 6 are coupled to the inverter 3. By means of the inverter 3 AC voltage for all windings 6 of the synchronous motor 5 can be provided.

The control unit 4 can detect a current I flowing through the windings 6. In this case, different embodiments are provided. Only the current I flowing through one of the windings 6 can be detected. Alternatively, currents I flowing across all the windings 6 of the stator can be measured separately. Finally, a summation current can be measured, i. H. All currents I can be tapped from the respective windings 6 and added up.

A method for monitoring a load of a laundry drum of a clothes dryer, which the circuit arrangement 1 according to Fig. 1 Now, as well as for monitoring a degree of dryness of laundry items loaded in the laundry drum, reference will now be made to FIGS Fig. 2 and 3 explained in more detail.

As already stated, the current I flowing through the winding 6 can be measured and evaluated by means of the control unit 4. An exemplary course of this current I is in Fig. 2 shown. The time t is plotted on the x-axis. During an entire drying process during a time interval 7, the laundry drum of the tumble dryer is repeatedly accelerated and decelerated by means of the synchronous motor 5. This can be seen on the basis of the pulse-shaped current profile: At a time t ₀ , the laundry drum is accelerated for the first time until it reaches a predetermined speed. The laundry drum is rotated during a time interval 8, in order then to be decelerated at a time t ₁ . During the time interval 8, current I flows through the windings 6. This current has an approximately sinusoidal profile. The laundry drum is repeatedly accelerated and decelerated during the time interval 7 of the entire drying program, being rotated during the respective time intervals 8 to 12. Characteristic of the course of the current I during the respective time intervals 8 to 12 is a current spike 13 which occurs at the beginning of each time interval 8 to 12.

Now, depending on the measured current I, the loading of the laundry drum and the degree of drying of the laundry items are monitored. At the beginning of a drying program, ie the first acceleration of the laundry drum at the time t ₀ and during the time interval 8, the current intensity of the current I is measured. For example, the current peak 13 of the current I is measured. This current is a measure of an initial load of the laundry drum, which is composed of the dry mass of the laundry items and from the moisture. This initial load is compared to a threshold and a warning signal is given when the initial load exceeds the predetermined threshold. From the initial load also required for the drying of the laundry items time, ie the time interval 7, calculated or estimated.

The current intensity of the current I is also monitored during the further time intervals 9 to 12. The current load of the laundry drum is determined depending on the current. Thus, the loading of the laundry drum at any time during the time interval 7 is known: It can either be calculated using a mathematical function depending on the current intensity of the current I or read from a characteristic or table by means of the control unit 4.

Now, the degree of drying of the laundry is to be monitored depending on the course of the current I. For this purpose, a change in the current intensity of the current I during the time interval 7 is monitored. For example, a difference between an average value of the current I detected during the time interval 8 and an average value of the current I detected during the next time interval 9 can be calculated. This difference is then a measure of the change in the degree of drying of the laundry items. It is also possible to calculate a difference between the current peaks 13. The change in the current intensity of the current I during the entire drying process, ie during the time interval 7, is in Fig. 2 illustrated by a line 14. If the course of the line 14 is constant, ie the current intensity of the current I no longer changes, the items of laundry no longer lose any water. This is an indication that the laundry is already dry. The drying process can thus be ended at a time t ₂ .

The current intensity of the current I is directly related to a torque of the synchronous motor 5. Both quantities, current I and torque, can be considered equal. If only one of the two quantities is mentioned, the statement can also be transferred to the second size.

Also, an output to the synchronous motor 5 energy represents a measure of the degree of drying of the laundry items and the loading of the laundry drum. Fig. 3 shows a time course of an output to the synchronous motor 5 energy E. This course is shown for a complete drying process, here for the duration of the time interval 7. How out Fig. 3 shows the change in energy .DELTA.E per unit time .DELTA.t a measure of the current load of the laundry drum. The change in energy .DELTA.E per unit time .DELTA.t, that is, the output to the synchronous motor 5 power is higher at the beginning of the drying process than at the end. This means that the loading of the laundry drum at the beginning of the drying process is higher than the end of the drying process, as the laundry items lose their moisture. Does not change the slope of the course of energy E, what in Fig. 3 can be seen from a time t ₃ , it can be determined that the laundry items are already dry. The degree of drying of the laundry items and the loading of the laundry drum can thus also be monitored depending on the course of energy.

LIST OF REFERENCE NUMBERS

1

circuitry

2

power adapter

3

inverter

4

control unit

5

permanent-magnet synchronous motor

6

windings

7 to 12

For time intervals

13

current peaks

14

line

E, ΔE

energy

.delta.t

time unit

I

electricity

t

Time

t ₀ , t ₁ , t ₂ , t ₃

timings

Claims (15)

1. Method of monitoring a load of a laundry drum of a laundry dryer and/or monitoring a degree of drying of articles of laundry introduced into the laundry drum, wherein the laundry drum is driven by means of an electric motor (5) comprising a stator with at least one winding (6), the method comprising the steps of:

   - activating the electric motor (5) by means of a control device (3, 4) by application of electrical voltage to the at least one winding (6);

   - measuring an electric current (I), which flows via the at least one winding (6), by means of the control device (3, 4); and

   - drawing a conclusion about the degree of drying of the articles of laundry and/or the load of the laundry drum in dependence on the measurement values of the current (I);

   characterised in that an energy (E), which is delivered to the electric motor (5), is calculated in dependence on the measured current (I) and a conclusion is drawn about the degree of drying of the articles of laundry and/or the load of the drum in dependence on a course of the energy (E) over time.
2. Method according to claim 1, wherein the laundry drum is driven by means of a permanently excited synchronous motor (5).
3. Method according to claim 1 or 2, wherein the activation of the electric motor (5) comprises:

   - accelerating the drum to a predetermined first rotational speed;

   - rotation of the drum at the first rotational speed during a predetermined first time period (8);

   - braking the drum;

   - accelerating the drum to a predetermined second rotational speed;

   - rotating the drum at the second rotational speed during a predetermined second time period (9); and

   wherein a difference (14) between a measured value, which is detected during the first time period, of the current (I) and a measured value, which is detected during the second time period, of the current (I) is calculated and a conclusion about the degree of drying of the articles of laundry and/or the load of the drum is made in dependence on the difference.
4. Method according to claim 3, wherein the difference between a mean value of the intensity of current during the first time period and a mean value of the intensity of current during the second time period is calculated.
5. Method according to claim 3 or 4, wherein during braking of the laundry drum a current flowing via the at least one winding (6) is measured by means of the control device (3, 4) and a conclusion about the load of the laundry drum is made on the basis of the measured values of the current (I).
6. Method according to any one of the preceding claims, wherein the current (I) is measured during a first activation (8) of the electric motor (5) during a drying program (7) and an initial load of the laundry drum is determined in dependence on the measured values of the current (I).
7. Method according to claim 6, wherein a warning signal is issued if the initial load exceeds a predetermined value.
8. Method according to any one of the preceding claims, wherein the detected measured values of the current (I) are compared with a stored characteristic curve.
9. Method according to any one of the preceding claims, wherein a phase delay between the phase of the voltage applied to the at least one winding (6) of the stator and the phase of the measured current (I) is calculated and a conclusion about the degree of drying of the articles of laundry and/or the load of the drum is made in dependence on the phase delay.
10. Method according to any one of the preceding claims, wherein the rotational speed behaviour of the electric motor (5) is regulated in dependence on the respective instantaneous degree of drying of the articles of laundry and/or on the respective instantaneous load of the drum.
11. Method according to claim 10, wherein the rotational speed behaviour is regulated with respect to a residual drying time.
12. Method according to claim 10 or 11, wherein the rotational speed behaviour is regulated with respect to a power consumption of the electric motor (5).
13. Circuit arrangement for monitoring the degree of drying of articles of laundry introduced into a laundry drum of a laundry dryer and/or for monitoring a load of the drum, comprising an electric motor (5), which comprises at least one stator with at least one winding (6) coupled with a control device (3, 4), wherein the control device (3, 4) is constructed for measuring a current (I), which flows via the at least one winding (6), and for recognising the degree of drying of the articles of laundry and/or the load of the drum in dependence on the detected measured values of the current (I), characterised in that the control device (3, 4) is designed for the purpose of calculating an energy (E), which is delivered to the electric motor (5), in dependence on the measured current (I) and making a conclusion about the degree of drying of the articles of laundry and/or the load of the drum in dependence on a course of the energy (E) over time.
14. Circuit arrangement according to claim 13, wherein the electric motor (5) is a permanently excited synchronous motor.
15. Laundry dryer with a circuit arrangement for monitoring the degree of drying of articles of laundry introduced into a laundry drum of the laundry dryer and/or for monitoring a load of the drum, comprising an electric motor (5), which comprises at least one stator with at least one winding (6) coupled with a control device (3, 4), wherein the control device (3, 4) is constructed for measuring a current (I), which flows via the at least one winding (6), and for recognising the degree of drying of the articles of laundry and/or the load of the drum in dependence on the detected measured values of the current (I), characterised in that the control device (3, 4) is designed for the purpose of calculating an energy (E), which is delivered to the electric motor (5), in dependence on the measured current (I) and making a conclusion about the degree of drying of the articles of laundry and/or the load of the drum in dependence on a course of the energy (E) over time.

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