EP3879023B1 - Method for detecting a load of a rotating drum in a laundry treatment machine, and corresponding laundry treatment machine - Google Patents

Description

The invention relates to a method for detecting a loading of a rotating drum in a laundry treatment machine with damp laundry items within a detection period from the start-up of the laundry treatment machine and by means of a sensor device comprising a pair of electrodes for contacting the laundry items in the drum, an evaluation device, lines which connect the evaluation device to the electrodes, and a counter provided in the evaluation device.

The invention also relates to a laundry treatment machine comprising a rotatable drum for receiving damp laundry items and a sensor device comprising a pair of electrodes for contacting laundry items in the drum, an evaluation device, lines which connect the evaluation device to the electrodes, and a counter provided in the evaluation device.

From the EP 2 013 403 A1 A method for operating a tumble dryer is disclosed, in which a sensor circuit is provided which generates a pulsed signal from contact with damp items of laundry. A voltage dependent on the electrical resistance of contacting items of laundry is measured via electrodes and fed to a comparator which, depending on whether the measured voltage is above or below a predetermined threshold value, generates the pulsed signal of a predetermined high voltage or zero. This is then fed to a counter which is used to determine an average frequency of the pulsed signal. This average frequency is used as an indication of the drying of the items of laundry. The absence of the pulsed signal during operation of the tumble dryer is used as an indication of a malfunction.

From the US 4,385,452 A A laundry treatment machine, in particular a tumble dryer, of the type defined at the beginning is produced. During a drying process of laundry items in the tumble dryer, a series of Voltage measurements on the laundry items that bridge the electrodes.

When a given number of consecutive voltage measurements provide results that relate to the moisture content of the laundry, the counter, which is incremented by pulses of constant frequency, is reset to zero. When the counter exceeds a predetermined limit, the drying process is terminated.

A method having the features of the preamble of claim 1 is known from US 2011/088278 A1 known.

The EP 1 657 352 A1 discloses a method for continuously determining the moisture content of the laundry during the drying process. In this method, the number of events is counted, i.e. how often the moisture content determined by measuring the resistance of electrodes in the laundry exceeds a predetermined value. The drying process is terminated when the number of events per unit of time exceeds a value that is intended to characterize a certain residual moisture content of the laundry.

In addition to detecting possible malfunctions of a laundry treatment machine, it is also useful to check a laundry treatment machine that has been put into operation and is functioning without any problems to see whether it has actually been loaded with laundry to be treated. In the case of a laundry treatment machine that functions as a tumble dryer, this means in particular checking whether the laundry treatment machine is loaded with a reasonably large amount of laundry with a reasonably high initial moisture content. If the laundry treatment machine has a drum that rotates during operation and moves the laundry items against each other, the mechanical power required to rotate the drum can be measured and compared with a threshold value, whereby if the value falls below the threshold value, it can be concluded that there is no load. Existing electrodes can also be used to measure the moisture content of the laundry during the drying process. However, the accuracy of the measurement can be severely impaired by the varying contact between the electrodes and the laundry items on the one hand and external interference signals that must be eliminated from the measured values by suitable filtering measures on the other. In particular, the filter measures can affect the accuracy of the measurement if there is a relatively small batch of laundry items with only a small amount of moisture in the laundry treatment machine.

The aim is therefore to provide an effective method for detecting the loading of a rotating drum in a laundry treatment machine with wet laundry items, as well as a laundry treatment machine that is suitably equipped.

To solve this problem, a method is provided for detecting the loading of a rotating drum in a laundry treatment machine with wet

Items of laundry within a detection period from the start-up of the laundry treatment machine and by means of a sensor device comprising a pair of electrodes for contacting the items of laundry in the drum, an evaluation device, lines which connect the evaluation device to the electrodes, and a counter provided in the evaluation device. In this method, the evaluation device sets the counter to zero when the machine is started up, whereupon the evaluation device records a series of resistance measurements from the electrodes during the detection period, the evaluation device compares each resistance measurement with a threshold value and increments the counter by 1 if the resistance measurement is less than the threshold value, and does not change the counter if the resistance measurement is greater than or equal to the threshold value. The evaluation device further compares a value of the counter with a first limit value and determines the detection of the load as positive if the value is greater than the first limit value and the detection as negative if the value is less than or equal to the first limit value.

This method determines the degree to which the resistance measurement data falls below a threshold value and is therefore relatively tolerant of noise in the resistance measurement values, with a large part of this noise resulting from the fact that the items of laundry moving in the rotating drum bridge the electrodes to a varying extent. Complex filtering measures for the signals taken from the electrodes are therefore unnecessary. Filtering measures that are used as part of the normal application of the electrodes to determine the remaining moisture in a drying batch of laundry can therefore be omitted as part of the proof, prior to the actual drying process, that there is actually a batch of laundry to be dried in the drum.

This process can also be completed within a particularly short detection period and thus help to avoid the use of energy for a laundry treatment machine that is running unnecessarily and the operation of sensitive components of the laundry treatment machine, for example a heat pump.

This method can also achieve a relatively high level of measurement accuracy and reliability, as even a very small and slightly damp batch of laundry items can be detected. With a suitable design, a batch of 0.1 kg of dry mass of laundry items with a moisture content of 10% (corresponding to a small towel that a person has used to dry wet hands) can be detected in a laundry treatment machine that is designed to dry a batch of laundry items weighing 5 kg to 10 kg of dry mass and a moisture content of 50%, i.e. a water content with a mass of 50% of the dry mass of the laundry items (corresponding to a small towel that a person has used to dry their wet hands). This also makes it possible to define automatic drying processes for such small batches of laundry items and to make them available in appropriately upgraded laundry treatment machines.

An existing laundry machine can be retrofitted to use the process with little effort, especially since the process can be implemented completely or at least largely by changing the control software accordingly. Any changes to the hardware primarily concern the switching on and off of filters for the signals to be taken from the electrodes, which are implemented in hardware.

In a preferred development of the method according to the invention, the evaluation device records first raw measurement values from the electrodes at a measurement frequency, and a plurality n ₁ of directly consecutive first raw measurement values are combined to form a corresponding second raw measurement value. The series of second raw measurement values thus obtained can thus be used in the method with or without further processing as a series of resistance measurement values.

Preferably, this measurement frequency is approximately 800 Hz.

Even more preferably, when combining every second raw measurement value, an average value of the corresponding first raw measurement values is formed, wherein a largest first raw measurement value and a smallest first raw measurement value from the corresponding raw measurement values are also disregarded.

Preferably, the plurality n ₁ of the first raw measurement values to be combined to form a second raw measurement value is equal to 8.

A preferred development of the invention provides that every second raw measurement value is a resistance measurement value, i.e. is used directly and without further processing in the further method according to the invention. This is not very complicated and is error-proof. However, with a measurement frequency of around 800 Hz, second raw measurement values with a frequency of 100 Hz arise, which, with a detection time of the order of one minute, leads to 6000 or a multiple of this number of individual data to be processed and requires a correspondingly large counter.

An alternative development of the invention to the previous development provides that the evaluation device forms each resistance measurement value as the minimum of a plurality n ₂ of second raw measurement values that follow one another in time. This further reduces the frequency with which the resistance measurements are obtained and reduces the number of data to be processed. Preferably, the second plurality n ₂ is equal to 100, corresponding to a reduction in the data to be processed by a factor of 100. With the preferred measurement frequency of 800 Hz and the also preferred plurality n ₁ of 8, this leads to one resistance measurement value being obtained per second of the detection time, and with a detection time of one minute, the counter would only have to be able to count up to 60, corresponding to the need for six bits of counter size per minute of detection time.

According to a further preferred development of the invention, the evaluation device determines the threshold value for each resistance measurement value from an average value with each resistance measurement value recorded since commissioning and subtraction of a distance value from the average value, whereby the distance value is greater than zero or equal to zero. A variable, sliding threshold value is therefore defined and applied, which is determined from the resistance measurements themselves and can therefore be adapted to the respective individual case. This makes the determination and definition of corresponding and sufficiently generally valid threshold values superfluous in the context of the development of the laundry care machine to be equipped according to the invention and also increases the accuracy of the detection in individual cases.

A preferred additional development of the development of the invention described in the previous section provides that the evaluation device compares the last average value formed at the end of the detection period with a second limit value and determines the detection of the load as positive if the last average value formed is less than a second limit value, and determines the detection as negative if the last average value formed is greater than or equal to the second limit value. This introduces an additional criterion for the desired detection and further increases the accuracy of the method.

It is particularly preferred that the detection period for applying the invention is set at approximately one minute after start-up. This advantageously utilizes the high accuracy of the method and promotes the achievement of the goal of avoiding unnecessary operation of the laundry treatment device. The invention therefore requires only approximately a quarter of the time required by a conventional method for detecting a load in a laundry care machine.

To achieve this object, a laundry treatment machine is also specified, comprising a rotatable drum for receiving damp laundry items and a sensor device comprising a pair of electrodes for contacting laundry items in the drum, an evaluation device, lines which connect the evaluation device to the electrodes, and a counter provided in the evaluation device, in which laundry treatment machine the evaluation device is set up to carry out the method according to the invention as explained herein.

Preferably, the laundry treatment machine according to the invention is a tumble dryer.

Preferably, the laundry treatment machine according to the invention is intended for treating a batch of laundry items with a dry weight of between 5 kg and 10 kg, as is usual for a laundry treatment machine for use in a private household. With further preference, this laundry treatment machine is intended for drying the laundry items that are placed in the drum with a residual moisture of about 50% for a period of about 2 hours. In this laundry treatment machine, the detection period for detecting a Loading according to the invention takes less than 1% of the time required for a total drying process.

Fig. 1

eine schematische Darstellung einer erfindungsgemäßen Wäschepflegemaschine;

Fig. 2

ein Flussdiagramm eines ersten Ausführungsbeispiels des Verfahrens;

Fig. 3

ein Flussdiagramm eines zweiten Ausführungsbeispiels des Verfahrens;

Fig. 4

ein Flussdiagramm eines dritten Ausführungsbeispiels des Verfahrens;

Embodiments of the invention are explained below with reference to the figures in the accompanying drawing. They show:

Fig.1

a schematic representation of a laundry care machine according to the invention;

Fig.2

a flow chart of a first embodiment of the method;

Fig.3

a flow chart of a second embodiment of the method;

Fig.4

a flow chart of a third embodiment of the method;

Figure 1 shows a laundry treatment machine 1 comprising a drum 2 which can be rotated about an axis 3 and is intended for receiving damp laundry items 4. The laundry treatment machine 1 also comprises a sensor device 5, 6, 7, 8 comprising a pair of electrodes 5 for contacting laundry items 4 in the drum 2, an evaluation device 6, lines 7 which connect the evaluation device 6 to the electrodes 5, and a counter 8 provided in the evaluation device 6. The lines 7 are mainly shown as only one line, but in reality they naturally have to be two-pole.

This laundry treatment machine 1 is a tumble dryer for use in a private household and is intended for treating a batch of laundry items 4 with a dry weight of between 5 kg and 10 kg. In particular, it is provided that the laundry items 4 are introduced into the drum 2 with a residual moisture content of approximately 50% and are dried to a residual moisture content of essentially zero over a period of approximately two hours.

According to conventional practice, the sensor device 5, 6, 7, 8 serves to control a drying process for wet laundry items 4 in the drum 2, whereby resistance measurements are made with the aid of the electrodes 5, from which the The residual moisture contained in the laundry items 4 is closed: the lower the electrical resistance that the laundry items 4 form between the electrodes 5, the greater the residual moisture. However, such measured resistances are subject to strong fluctuations, which arise because the contact between the electrodes 5 and the laundry items 4 is subject to strong fluctuations due to their movement in the rotating drum 2. Interference signals also play a role, which penetrate into the evaluation device 6 with their lines 7 due to an antenna effect of the electrodes 5 and are superimposed on the measured resistance values. It is therefore necessary for filters to be connected upstream of a moisture measuring device 11 in the evaluation device 6, symbolized here by a first filter 9 and a second filter 10. Of these, the second filter 10 is only assigned to the moisture measuring device 11. Associated with the moisture measuring device 11 is a second display device 13, shown schematically as a lamp.

Furthermore, the evaluation device 6 has a counter 8, to which measured values from the electrodes 5 are only fed after filtering by the first filter 9, this filtering being carried out as follows: The evaluation device 6 first records first raw measured values r1 _j from the electrodes 5 at a predetermined measuring frequency, which is preferably about 800 Hz, and combines a first plurality n ₁ of directly successive first raw measured values r1 _j to form a corresponding second raw measured value r2 _j . When combining each second raw measured value r2 _{j ,} an average of the corresponding first raw measured values r1 _j is formed, with a largest first raw measured value and a smallest first raw measured value from the corresponding raw measured values r1 _j being disregarded. Said first plurality n ₁ is preferably equal to 8. The first display device 12, again shown schematically as a lamp, is assigned to the counter 8.

Each second raw measurement value r2 _j obtained in this way can be easily regarded and used as a resistance measurement value r _i . However, with a measurement frequency of about 800 Hz, the frequency at which the second raw measurement values r2 _j thus obtained are obtained is still very high at 100 Hz. If the detection period to is set to one minute, a total of about 6000 second raw measurement values r2 _j are obtained, which require a counter 8 with the corresponding capacity (or a counter 8 which is limited in its capacity with a sufficient maximum size and works in such a way that it stops when it has reached its maximum count value and is not reset to zero by a conventional overflow. It is therefore interesting to further reduce the number of resistance measurement values r _i . To do this, the evaluation device 6 can form each resistance measurement value r _i as the minimum of a second plurality n ₂ of temporally successive second raw measurement values r2 _j , where the second plurality n ₂ is equal to 100. In the example discussed here, the number of resistance measurement values to be evaluated per detection period is thus reduced from 6000 to 60.

This in Fig.2 The method shown as a flow chart for detecting the loading of a rotating drum 2 in the laundry treatment machine 1 with damp laundry items 4 within a detection period t _D from the start-up of the laundry treatment machine 1 and by means of a sensor device 5, 6, 7, 8 comprising a pair of electrodes 5 for contacting the laundry items 4 in the drum 2, an evaluation device 6, lines 7 which connect the evaluation device 6 to the electrodes 5, and a counter 8 provided in the evaluation device 6, runs in particular as follows: The evaluation device 6 sets the counter 8 to zero when the machine is started up. During the detection period t _D the evaluation device 6 records a series of resistance measurements r _i from the electrodes (5). The evaluation device 6 compares each resistance measurement value r _i with a threshold value s; it increments the counter 8 by one if the resistance measurement value r _i is less than the threshold value s, and does not change the counter 8 if the resistance measurement value r _i is greater than or equal to the threshold value s. Finally, the evaluation device 6 compares a value z of the counter 8 with a first limit value g ₁ and determines the proof of loading as positive if the value z is greater than the first limit value g ₁ , and determines the proof as negative if the value z is less than or equal to the first limit value g _1. For this purpose, a counting parameter i is initially set to zero, as are a time parameter t and the value z of the counter 8. Each time a resistance measurement value r _i is recorded, the counting parameter i is incremented by one. This resistance measurement value r _i is then compared with the threshold value s, and if necessary, the counter 8 is incremented by one. This is repeated in a loop until the time parameter t exceeds the length of the detection period t _D . Then the value of the counter 8 is compared with the first limit value g ₁ and the detection is determined as positive or negative accordingly, as in Fig.2 indicated with plus and minus signs.

The Figures 3 to 4 show flow charts of preferred embodiments of the method. Not shown are steps in which first raw measured values r1 _j are processed into second raw measured values r2 _j . Such steps correspond to the filtering of the Fig.1 shown first filter 9, as described in detail above.

However, Figure 3 an embodiment of the method in which the evaluation device 6 forms each resistance measurement value r _i as a minimum of a second plurality n ₂ of temporally successive second raw measurement values r2 _j , where the second plurality may be equal to 100. This may reduce the number of resistance measurements to be evaluated per detection period t _D from 6000 to 60. For this purpose, according to Fig.3 a second counting parameter j and a flag f, both of which are initially set to zero. Partial intervals between times t _j-1 and t _j of the detection period to, which is divided into n ₂ sub-intervals of equal length, are identified using the second counting parameter j, and over each of these time intervals it is determined whether there is a resistance measurement value r _i that is smaller than the threshold value s. If this is the case, the flag is set to one. After each sub-interval has elapsed, it is only determined whether the flag is equal to 1. If so, the counter 8 is incremented by one. The detection takes place at the end of the detection period as per Fig.2 .

In the proceedings under Figure 4 the evaluation device 6 determines a sliding threshold value s _i for each resistance measurement value r _i from an average value m _i with each resistance measurement value r _i recorded since commissioning and subtraction of a distance value a from the average value m _i , where the distance value a is greater than zero or equal to zero. The threshold value to be set in each case is thus determined from data obtained in the process itself (apart from the distance value a that may be set), and is thus adapted to the individual case. Figure 4 does not describe the determination of the moving average m _i directly, but only indicates this through the expression m _i+1 (m _i ), which shows the dependency between successive moving averages. In addition to the verification criterion that at the end of the detection period t _D the value z of the counter 8 exceeds the first limit value, an additional verification criterion is used. This is done in such a way that the evaluation device 6 calculates the last value formed at the end of the detection period t _D. compares the mean value m _i with a second limit value g ₂ and determines the proof of loading as positive if the last calculated mean value m _i is less than the second limit value g ₂ and determines the proof as negative if the last calculated mean value is greater than or equal to the second limit value g ₂ .

A significant benefit of the invention is that the detection period t _D can be set to approximately one minute after start-up, which is associated with a reduction of the detection period required for conventional methods by 75%. The invention thus achieves significantly more precise detection of a load in a laundry care machine in less time than conventional practice.

LIST OF REFERENCE SYMBOLS

1

Laundry treatment machine

2

drum

3

axis

4

Laundry item

5

electrode

6

Evaluation device

7

Line

8th

counter

9

First filter

10

Second filter

11

Humidity measuring device

12

First display device

13 14

Second display device

a

Distance value

e

Flag

g1

First limit

g2

Second limit

mi

moving average

n1

First variety

n2

Second multitude

r1j

first raw measurement value

r2j

second raw measurement value

s

Threshold

si

sliding threshold

t

Time

tD

Detection period

e

Value of counter 8

Claims (15)

1. Method for detecting a load of a rotating drum (2) in a laundry treatment machine (1) with damp items of laundry (4) within a detection time interval (t_D) from commissioning the laundry treatment machine (1) and by means of a sensor facility (5, 6, 7, 8) comprising a pair of electrodes (5) for making contact with the items of laundry (4) in the drum (2), an evaluation facility (6), lines (7), which connect the evaluation facility (6) with the electrodes (5) and a counter (8) provided in the evaluation facility (6), in which method:

   a) the evaluation facility (6) sets the counter (8) to zero with the commissioning;

   b) the evaluation facility (6) records a series of resistance measured values (r_i) of the electrodes (5) during the detection time interval (t_D);
   characterised in that

   c) the evaluation facility (6) compares each resistance measured value (r_i) with a threshold value (s) and increments the counter (8) by 1 if the resistance measured value (r_i) is smaller than the threshold value (s) and does not change the counter (8) if the resistance measured value (r_i) is greater than the threshold value (s) or is equal to the same;

   d) the evaluation facility (6) compares the value (z) of the counter (7) with a first limit value (gi) and determines the detection of the loading as positive if the value (z) is greater than the first limit value (g₁) and determines the detection as negative if the value (z) is lower than the first limit value (g₁) or is equal thereto.
2. Method according to claim 1, in which the evaluation facility (5) records first raw measured values (r1_j) with a measuring frequency of the electrodes, and in each case combines a first plurality (n1) of directly consecutive first raw measured values (r1_j) to form a corresponding second raw measured value (r2_j).
3. Method according to claim 2, in which the measuring frequency amounts to approximately 800 Hz.
4. Method according to one of claims 2 and 3, in which, with the combination of each second raw measured value (r2_j), an average value of the corresponding first raw measured value (r1_j) is formed, wherein a largest first raw measured value and a smallest first raw measured value from the corresponding raw measured values (r1_j) remain disregarded.
5. Method according to one of claims 2 to 4, in which the first plurality (n₁) is equal to 8.
6. Method according to one of claims 2 to 5, in which each second raw measured value (r2_j) is a resistance measured value (r_i).
7. Method according to one of claims 2 to 5, in which the evaluation facility (5) forms each resistance measured value (r_i) as a minimum of a second plurality (n₂) of temporally consecutive second raw measured values (r2_j).
8. Method according to claim 7, in which the second plurality (n₂) is equal to 100.
9. Method according to one of claims 6 to 8, in which the evaluation facility (5), for each resistance measured value (r_i), determines a floating threshold value (s_i) from an average value (m_i) with each resistance measured value (r_i) recorded since the commissioning and subtraction of a distance value (a) from the average value (m_i), wherein the distance value (a) is greater than zero or equal to zero.
10. Method according to claim 9, in which the evaluation facility (5) compares the average value (m_i) last formed upon expiry of the detection time interval (t_D) with a second limit value (g₂) and determines the detection of the load as positive if the last formed average value (m_i) is smaller than the second limit value (g₂), and determines the detection as negative if the last formed average value is greater than the second limit value (g₂) or is equal thereto.
11. Method according to one of the preceding claims, in which the detection time interval (t_D) is scheduled for approximately one minute after the commissioning.
12. Laundry treatment machine (1) comprising a rotatable drum (2) for receiving damp items of laundry (4) and a sensor facility (5, 6, 7, 8) comprising a pair of electrodes (5) for making contact with items of laundry (4) in the drum (2), an evaluation facility (6), lines (7), which connect the evaluation facility (6) with the electrodes (5) and a counter (8) provided in the evaluation facility (6), characterised in that the evaluation facility (6) is designed to carry out the method according to one of the preceding claims .
13. Laundry treatment machine (1) according to claim 12, which is a tumble dryer.
14. Laundry treatment machine (1) according to one of claims 12 and 13, which is determined to treat a batch of items of laundry (3) with a dry weight of between 5 kg and 10 kg.
15. Laundry treatment machine (1) according to claim 14, which, in order to dry the items of laundry (3) which are introduced into the drum (2) with a residual moisture of approximately 50%, is determined during a time interval of approximately 2 hours.

Images