Method for operating an automatic washing machine, and automatic washing machine

Abstract

A washing machine and method for operating a washing machine having a suds container and a non-ribbed drum. During rotation of the drum in a subcritical rotational speed range, the method includes determining an average value, a minimum, and a maximum of an oscillation of a physical variable relating to the drum or the motor, forming an overall average value from the determined average values, subtracting the overall average value formed from the corresponding minimum determined per oscillation and the corresponding maximum determined per oscillation to calculate a maximum value and a minimum value per oscillation, respectively. In each case an amount is formed from the respective calculated maximum value and an amount is formed from the respective calculated minimum value, a standard deviation from the amounts is determined, and a loading situation where laundry is rolling in the drum is determined based on the determined standard deviation.

Claims

1. A method for operating a washing machine having a suds container for holding washing liquid, a non-ribbed drum rotatably mounted in the suds container for holding laundry, a motor for driving the drum, and a control device, comprising the following steps while rotating the drum in a subcritical rotational speed range: determining an average value, a minimum, and a maximum of an oscillation of a physical variable relating to the drum or the motor per complete revolution of the drum over a predetermined period of time in which a plurality of revolutions of the drum take place; forming an overall average value from the determined average values; subtracting the overall average value from the corresponding maximum determined per oscillation and the corresponding minimum determined per oscillation to calculate a maximum value and a minimum value per oscillation, respectively; forming in each case an absolute value amount of the respective calculated maximum value and in each case an absolute value amount of the respective calculated minimum value; determining a standard deviation from the amounts formed over the predetermined period of time; and detecting, based on the determined standard deviation, whether a loading situation where laundry is rolling in the drum is present, wherein a loading situation where laundry is rolling in the drum is detected if the standard deviation determined is greater than a predetermined limit value.

2. The method according to claim 1, wherein the physical variable relating to the drum or the motor is preferably an actual rotational speed of the drum or a variable that correlates with the actual rotational speed.

3. The method according to claim 1, wherein the physical variable related to the drum or the motor is a torque of the motor or a variable correlated with the torque of the motor.

4. The method according to claim 1, wherein if a loading situation where laundry is rolling in the drum is detected, a predetermined action is also executed.

5. The method according to claim 4, wherein the predetermined action is stopping the rotation of the drum or continuing the rotation of the drum with a rocking process.

6. The method according to claim 1, wherein the predetermined period of time is in the range of from 1 to 15 seconds.

7. The method according to claim 1, wherein the subcritical rotational speed range is in the range of from 70 to 149 rpm.

8. A washing machine having a suds container for holding washing liquid, a non-ribbed drum which is rotatably mounted in the suds container for holding laundry, a motor for driving the drum, and a control device that is designed and set up to execute a method according to claim 1.

9. The method according to claim 1, wherein the predetermined period of time is in the range of from 2 to 10 seconds.

10. The method according to claim 1, wherein the predetermined period of time is in the range of from 3 to 5 seconds.

11. The method according to claim 1, wherein the control device adjusts a signal to the motor driving the drum when the loading situation where laundry is rolling is detected.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An embodiment of the disclosure is described in more detail below with reference to a purely schematic drawing and an example. In the drawings:

(2) FIG. 1 shows a partial curve of a torque in a time sequence.

DETAILED DESCRIPTION OF THE DRAWINGS

(3) FIG. 1 shows a partial curve of a torque in a time sequence. FIG. 1 shows the partial curve of the torque of a motor of a washing machine executing a washing program and in a loading situation where laundry is rolling and where laundry is not rolling in its drum. FIG. 1 shows the time signal curve of the torque at a target rotational speed of the drum of 120 rpm. The partial curve of the torque is shown for a predetermined period of time of 3 seconds during which the drum completes six revolutions at two revolutions per second.

(4) In the case of the solid line, the laundry lies completely in contact with the drum casing, so that the drum is free of rolling laundry, and a fixed imbalance has developed. This fixed imbalance causes the control of the motor per drum revolution to increase the torque relative to an average value, when increasing the fixed imbalance causes a braking of the actual rotational speed, and to decrease it relative to an average value, when decreasing the fixed imbalance causes an acceleration of the actual rotational speed. The solid line therefore shows the loading situation only with fixed imbalance where laundry is not rolling in the drum. The dashed line shows the loading situation with a fixed imbalance and where laundry is rolling in the drum. The torque waveform for the drum with fixed imbalance and where laundry is rolling in the drum, in which case the laundry does not completely contact the drum casing, as shown by the dashed line, differs from the torque waveform for the drum where laundry is not rolling in the drum.

Example

(5) A washing machine has a suds container for holding washing liquid, a non-ribbed drum rotatably mounted in the suds container for holding laundry, a motor for driving the drum, and a control device having a motor controller. The washing machine runs a washing program where laundry is located in the drum. In the course of the washing program, the drum is rotated at a target rotational speed of 120 rpm. At least partially during the execution of the washing program, the control device determines a time curve of a torque of the motor. FIG. 1 shows the determined curve of the torque.

(6) The following steps are now executed by the washing machine, in particular by the control device: determining an average value, a minimum, and a maximum of an oscillation of the torque occurring per complete revolution of the drum over the predetermined period of time, for example as shown in FIG. 1, in which a pluralityonly as an example sixcomplete evolutions of the drum take place; forming an overall average value from the determined average values; subtracting the total or overall average value formed from the corresponding minimum determined per oscillation and the corresponding maximum determined per oscillation to calculate a maximum value and a minimum value per oscillation, respectively; forming in each case an amount from the respective calculated maximum value and in each case an amount from the respective calculated minimum value; determining a standard deviation from the amounts formed over the predetermined period of time; and detecting whether a loading situation where laundry is rolling in the drum is present, depending on the determined standard deviation.

(7) Table 1 shows the corresponding minima and maxima of the signal curve of the engine torque for the case of the loading situation only with a fixed imbalance where laundry is not rolling in the drum, derived from FIG. 1, and the method steps described above, which result in the formation of the standard deviation.

(8) TABLE-US-00001 TABLE 1 Presentation of the minima and maxima per drum revolution, subtraction of the total average value, formation of the amount, and end result of the standard deviation for the case of the loading situation where laundry is not rolling. shows the corresponding minima and maxima of the signal curve of the engine torque for the case of the loading situation only with a fixed imbalance where laundry is not rolling in the drum, derived from FIG. 1, and the method steps described above, which result in the formation of the standard deviation. Without rolling Overall average laundry value: 182 Drum revolution 1 2 3 4 5 6 Maximum [Nm] 349 350 338 342 348 349 Minimum [Nm] 25 8 26 10 30 8 After subtracting the overall average value Drum revolution 1 2 3 4 5 6 Maximum [Nm] 167 168 156 160 166 167 Minimum [Nm] 157 174 156 172 152 174 After formation of the amount Drum revolution 1 2 3 4 5 6 Maximum [Nm] 167 168 150 160 166 167 Minimum [Nm] 157 174 156 172 152 174 Total standard deviation: 7.62

(9) The determined standard deviation is now compared with a predetermined limit value, which is stored in the washing machine and is 10, for example. The determined standard deviation is smaller than the predetermined limit value, so that the method detects that the drum has a loading situation where laundry is rolling in the drum. The drum continues to rotate at the target rotational speed of 120 rpm.

(10) Table 2 shows the corresponding minima and maxima of the signal curve of the engine torque for the case of the loading situation with a fixed imbalance and where laundry is rolling in the drum, derived from FIG. 1, and the method steps described above, which result in the formation of the standard deviation.

(11) TABLE-US-00002 TABLE 2 Presentation of the minima and maxima per drum revolution, subtraction of the total average value, formation of the amount, and end result of the standard deviation for the case of the loading situation where laundry is rolling in the drum. With Overall average rolling laundry value: 192 Drum revolution 1 2 3 4 5 6 Maximum [Nm] 359 382 349 341 358 356 Minimum [Nm] 52 25 20 12 48 13 After subtracting the overall average value Drum revolution 1 2 3 4 5 6 Maximum [Nm] 166 189 156 148 165 163 Minimum [Nm] 141 168 173 181 145 180 After formation of the amount Drum revolution 1 2 3 4 5 6 Maximum [Nm] 166 189 156 148 165 163 Minimum [Nm] 141 168 173 181 145 180 Total standard 15.01 deviation:

(12) The determined standard deviation is now compared with the predetermined limit value, which is stored in the washing machine and is 10, for example. The determined standard deviation is greater than the predetermined limit value, so that the method detects a loading situation where laundry is rolling in the drum. A predetermined action is also executed in the method since it was detected that the laundry is rolling in the drum. The predetermined action is stopping the rotation of the drum or continuing the rotation of the drum during a rocking process.