DK1736589T3

DK1736589T3 - Washing with imbalance detector

Info

Publication number: DK1736589T3
Application number: DK06011034.3T
Authority: DK
Inventors: Guido Schellenberg; Sven Hansen
Original assignee: V Zug Ag
Priority date: 2005-06-24
Filing date: 2006-05-30
Publication date: 2014-11-17
Also published as: EP1736589B1; PL1736589T3; SI1736589T1; EP1736589A2; EP1736589A3

Description

The invention relates to a washing machine according to the preamble of claim 1.

Such a washing machine is e.g. described in EP 1 391 549. It has a drum which rotates about an axis, a measurement device for detecting an imbalance in the drum during centrifugal operation, by means of which measurement values are generated as a function of the rotation angle of the drum, and a controller for determining the position and/or the magnitude of the imbalance on the basis of the measurement values. The imbalance can be compensated by taking into account the parameters determined in this way and/or the centrifugal program may be interrupted in case of a too large imbalance, e.g. in order to rearrange in the drum the laundry to be centrifuged.

It has been noticed that the determination of precise measurement values in such washing machines is not that easy. The objective of the present invention is therefore an improvement of the measurement precision.

This objective is reached by the washing machine according to claim 1. According to it, the washing machine has a memory for storing calibration values, wherein the controller of the washing machine is adapted to determine the position and/or magnitude of the imbalance by calculative recombination of the measured values and the calibration values.

Preferably, idle measurement values as a function of the rotation angle are stored in the memory, i.e. the measurement values determined during a calibration measurement with empty drum. The controller calculates adjusted values from the measurement values, e.g. by quotient formation, on the basis of which the position and/or magnitude of the imbalance can be determined e.g. by subtraction of the idle measurement values .

In this way it is possible to eliminate inherent asymmetries in the rotating parts and the measurement device. This is particularly advantageous in case an angular speed sensor is used, which detects marks on a rotating body. In this case the influence of inaccuracies of position and/or magnitude of the marks can be eliminated by calculative recombination with the idle measurement values.

In a further preferred embodiment the phase shift between the measurement values and the position of the imbalance is stored in the memory as a function of the rotational speed of the drum. Because this phase shift depends on the rotational speed, it is possible to determine the position of the imbalance by calculative recombination of the measurement values with the phase shift depending on the rotational speed of the drum.

Further preferred embodiments result from the dependent claims as well as from the now following description by means of the figures. It is shown in:

Fig. 1 a schematic section through a washing machine,

Fig. 2 a schematic view of the drum, the angular speed sensor and the controller,

Fig. 3 the measured time values in idle mode, measured by the angular speed sensor,

Fig. 4 the measured time values under load, measured by the angular speed sensor, and

Fig. 5 the phase shift between the measurement signal and the imbalance position depending on the rotational speed.

The washing machine shown in Fig. 1 has a drum 1 with a horizontal rotation axis 2. The drum 1 is arranged inside a vat 3. A motor 4 is attached to the vat 3, rotating the drum via a belt 5 and a belt pulley 6. The vat 3 is oscillatingly supported inside the washing machine by a suspension.

Acceleration sensors 7 are attached to the front end and, opposed, at the rear end of the vat 3 in the shown embodiment, making it possible to determine a pivoting movement and/or a tumbling movement of the drum. Additionally, an angular speed sensor 8 is provided on the pulley 6, by means of which the current angular speed can be measured as a function of the rotation angle of the drum, as described further down. Instead of or additionally to the acceleration sensors 7 and/or the angular speed sensor 8 it is possible to use e.g. distance sensors.

The sensors allow the detection of an imbalance in the drum during the centrifugal process or at the beginning of the centrifugal process respectively.

As described e.g. in DE 43 13 819, an imbalance in the drum is compensated by injecting a liquid, here water, in a targeted way into special tanks attached to the drum.

If the imbalance is too large, the centrifugal process may also be interrupted, as already mentioned.

In the shown embodiment three tanks 10 are provided for imbalance compensation, being arranged in the ribs 11 of the drum 1. Each tank 10 extends e.g. with its longitudinal axis along the entire axial length of the drum 1. Three filling rings 13a, b and c are arranged on the rear end face 12 of the drum 1. The filling rings are coaxial, wherein the filling ring 13a has the smallest diameter, the filling ring 13b has the next larger diameter and the filling ring 13c has the largest diameter .

Each filling ring is connected to one of the tanks 10 via a filling duct 14. A stationary injection device 16 is provided in order to inject water into the filling rings. It comprises a water inlet 17 supplying water to three valves 18. The water travels from the valves 18 to a corresponding duct 19a via a falling section 19, wherein the falling section 19 supresses a backflow of water into the water inlet 17. The ducts 19a end in nozzles 19b, from where the water is injected into the respective filling rings 13a, b, c. The nozzles 19b are attached to the vat 3 or to the swinging system of the washing machine respectively.

Fig. 2 shows schematically again the mechanical construction of the washing machine as well as its controller 20.

Particularly, Fig. 2 shows the drum 1 and its rotation axis 2. Furthermore a rotating body 21 is shown, which may e.g. be formed as a rotating disk arranged on the pulley 6, as seen in Fig. 1. The rotating body 21 rotates with the drum. It carries a plurality of marks formed as teeth 22 distributed evenly on the periphery of the rotating body. The angular speed sensor 8 arranged stationary on the rotation body 21 is capable of detecting the marks. In the present embodiment the angular speed sensor 8 is designed as light barrier, the light path of which is interrupted by the teeth 22.

Instead of a light barrier it is also possible to use another optical detector detecting the optically detectable marks on the rotating body 21. It is possible to also use non-optical, e.g. magnetic, measurement methods in connection with marks designed accordingly.

Time durations between the marks are determined from the signals of the angular speed sensor 8, e.g. as times between the signal transitions. Fig. 3 shows a corresponding series of measurement values tO during idle time of the drum, i.e. when the drum is empty. Because the teeth have all the same size and the same mutual distance, all measured time values are approximately the same. The deviations shown in Fig. 3 are present due to asymmetries in construction of the rotating parts as well as inaccuracies during the production of the teeth 22.

Each determined time value is inversely proportional to the current angular speed of the drum 1.

If the drum 1 is rotated under load and if the load is distributed in such a way that an imbalance is generated, the current angular speed of the drum 1 depends on the current rotation angle. A corresponding measurement series with durations t is shown in Fig. 4. As can be seen, the angular speed varies approximately in a sine form.

The magnitude of the imbalance is reflected in the amplitude of the sine-shaped variation in Fig. 4 and the position in the phase position of the signal.

In order to determine the angular position of the imbalance on the basis of a given phase position of the measurement signal, it has to be possible to attribute each one of the sectors i according to Fig. 3 or 4 respectively, to a rotation angle of the drum. For this, a zero point issuing device is provided as part of the angular speed sensor 8, issuing a signal when the drum is located in a certain zero position. In this case, the rotation position a of the drum 1 corresponding to a sector i can be calculated as follows:

a = 360° · i/N wherein N is the number of sectors.

For a precise measurement of amplitude and phase it is advantageous to consider the influence of said idle deviations according to Fig. 3. As mentioned, they result because of asymmetries of the rotating parts and of the angular speed sensor 8 and therefore also lead to errors in the measurement under load.

For this reason, in an advantageous embodiment of the invention the idle measurement values tO(i) are stored as a function of the rotation angle a or of the sector i respectively, in a memory 23 of the controller 20, according to Fig. 3, and the controller 20 is adapted to determine the position and/or magnitude of the imbalance by calculative recombination of the measured values t(i) according to Fig. 4 with the idle values tO (i) .

For a correction which is independent of the rotation speed it is possible to form the difference

(1) for the measurement value of each sector or rotation angle i respectively, wherein the sums are calculated for all sectors j. The difference d(i) calculated in this way is then used for determining the amplitude and phase of the imbalance.

It is also conceivable to calculate the quotient

(2)

These quotients q(i) are also independent of the idle deviations, like the differences d(i).

The calibration values tO(i) may be stored in the memory 23 by the manufacturer, e.g. during the final inspection of a device. However, they may also be determined later, at least partially, by the controller 20 and stored, e.g. by starting a certain calibration program, during which measurements are carried out with an empty drum. This is particularly appropriate when the angular speed sensor 8 or the rotating body 21 have to be replaced during maintenance or repair.

As already mentioned, the shown embodiment according to Fig. 1 also has two acceleration sensors 7 beside the angular speed sensor 8. Preferably, these different sensor types are used additionally. It has been found that in case of lower angular speeds the angular speed sensor 8 yields the most precise results, while the signals of the acceleration sensors 7 are relatively weak. In case of higher angular speeds the signals of the acceleration sensors 7 are stronger, while the ones of the angular speed sensors 8 lose their meaningfulness.

If the position of the imbalance shall be determined with the acceleration sensors 7, the signals of the acceleration sensors 7 measured at certain instants must first be correlated with the angular position of the drum 1. For this, e.g. the already mentioned zero point issuing device may be provided, which issues a signal when the drum is located in a certain zero position. Starting from the instant tn, in which this zero position was reached last time, and the current rotation speed D of the drum 1 (which may e.g. also be determined via the zero point issuing device), it is possible to attribute an angular position a to a measurement of the acceleration sensors at a given time tx by the equation

(3)

Furthermore it has however to be taken into account that the phase shift e.g. between the angle ao, at which angle the signal of one of the acceleration sensors 7 e.g. has its maximum, and the angular position 0% of the imbalance, is depending on the angular speed of the drum 1: - In case of low angular speeds of the drum, i.e. when the angular speed is such that the laundry doesn't fall anymore in the drum but is pressed against the drum wall, but the angular speed is clearly lower than the lowest resonance frequency of the elastic bearings of the drum and the vat, the phase shift between the maximum of the signal aO and the position of the imbalance aU is of about -90°. - In case of very high angular speeds clearly above the highest resonance frequency of the bearings of the drum 1, the phase shift shifts by 180°, i.e. in the present example to about +90°. A corresponding diagram of the phase shift is shown in Fig. 5. As can be seen in the figure, the course of the phase shift deviates in practice from a simple arctan-behaviour, because the bearings has multiple resonance frequencies and multiple degrees of freedom.

In order to determine the position of the imbalance from the phase of the sine-shaped variation of the signals of the acceleration sensors 7, the phase shift between the signals of the acceleration sensors 7 and the position of the imbalance is stored in a memory 25 of the controller 20 as function of the angular speed of the drum 1. This may e.g. be done as single values according to Fig. 5 or as parameters of a curve adapted to the values of the curve according to Fig. 5. The phase shift stored in the memory 25 and depending on the angular speed of the drum 1 forms calibration values by means of which the position measurements can be corrected.

In order to carry out the correction, the microprocessor 24 of the controller 20 determines the phase of the measured acceleration values, e.g. by means of Fourier-transform or Cosine-transform, wherein also the amplitude may be determined in the same calculation step. The microprocessor 24 adds the phase shift to the determined phase, according to the calibration values from the memory 25 attributed to this angular speed, from which the angular position of the imbalance results. Depending on this angular position, it is now e.g. possible to fill the tanks 10. For this, the controller 20 issues respective control signals to a valve controller 26.

Instead of acceleration sensors 7 which measure axial and/or radial accelerations of the drum 1 or the swinging system, also the position sensors may be used, which measure the axial or radial deviations of the drum 1, the vat 3 or other parts of the swinging system. In this case, the above mentioned phase correction has to be carried out in order to reach more precise measurements .

Preferably, the acceleration sensors 7 are used for processing the mean value of the signals. In this way a signal free of tilts of the drum is generated.

The calibration values, i.e. the course of the phase shift according to Fig. 5, may be stored in memory 25 by the manufacturer, by carrying out measurements on a drum with an imbalance attached in a known and defined position. The same calibration values may be used for all identical device of a same known type.

Claims

A washing machine with a drum (1) rotating about a pivot axis (2), a measuring device (7, 8) for detecting an imbalance in the drum (1), with which measurement values can be generated as a function of the drum's rotational position. on (a), and a control (20) for determining a position and / or magnitude of the imbalance from the measured values, characterized by a storage (23, 25) for storing calibration values, wherein the control (20) is designed to calculate the position and / or magnitude of the imbalance in calculating the measured values with calibration values.

Washing machine according to claim 1, characterized in that in the bearing (23, 25) idle measurement values (t0) are stored as a function of the turning position (a) and the control (20) is designed to calculate the position and / or the magnitude of the imbalance in calculating the measured values with the idle values.

Washing machine according to Claim 2, characterized in that the control (20) is designed to determine a quotient (q) of the measured values (t) and the idle measuring values (tO) concerned.

Washing machine according to one of the preceding claims, characterized in that a phase shift (phi) between the measured values and the position of the imbalance as a function of the drum speed (D) and the control (20) is stored in the bearing (23, 25). ) is designed to calculate the position of the imbalance by calculating the measured values with the phase shift (phi).

Washing machine according to one of the preceding claims, characterized in that the control (20) is designed to determine at least a portion of the calibration values of an empty drum (1) in a calibration measurement.

Washing machine according to one of the preceding claims, characterized in that the measuring device has at least one angular velocity sensor (8, 21, 22) which measures the instantaneous angular velocity as a function of the rotary position of the drum.

Washing machine according to claim 6, characterized in that the angular velocity sensor (8, 21, 22) has a rotating element (21) and a detector (8) wherein the rotating element (21) rotates with the drum (1) and carries a plurality of markings (22) and wherein the detector (8) is stationary at the pivot element (21) and detects the markings (22).

Washing machine according to claim 7, characterized in that the detector (8) is an optical detector and the markings (22) are optically readable markings, and in particular that the detector (8) is a photocell with a beam passable with the markings ( 22).

Washing machine according to one of the preceding claims, characterized in that the measuring device has at least one acceleration sensor (7) and / or a position sensor for measuring a radial and / or axial acceleration or position variation of the drum (1) or of a non-rotating vessel. (3) surrounding the drum and at least a portion of the measurement values are acceleration and / or position signals.

Washing machine according to claim 9, characterized in that at least two acceleration sensors (7) are provided at opposite ends of the vessel (3), where an average value of the signals of the acceleration sensors (7) is calculated.