EP1736589A2 - Washing machine with unbalance detector - Google Patents

Abstract

The horizontal axis (2) wash drum (1) of a clothes washing machine has within the resiliently mounted tank (3) is rotationally driven by an electric motor (4) and pulley (6) having a segmented disc (21) and speed sensor (8) on the axis of the drum and accelerometers (7) by which the vertical motion of the drum is monitored and the speed controlled to prevent excessive amplitudes.

Description

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

Such a washing machine is eg in EP 1 391 549 described. It has a drum which rotates about an axis of rotation, a measuring device for detecting an imbalance in the drum in the spinning operation, with which as a function of the rotation angle of the drum measured values can be generated, and a controller for determining the position and / or size of the imbalance the measured values. Because of the unbalance parameters thus obtained, the unbalance can be compensated for and / or the spin program can be interrupted if there is too much imbalance, eg to redistribute the laundry to be spun in the drum.

It turns out that the determination of accurate readings in such washing machines is not easy. Object of the present invention is thus an improvement of the measurement accuracy.

This object is achieved by the washing machine according to claim 1. Accordingly, the washing machine includes a memory for storing calibration values. The control of the washing machine is designed to determine the position and / or size of the unbalance by calculating the measured values with the calibration values.

Preferably, idle measurements are stored in memory as a function of the angle of rotation, i. the measured values, as determined during a calibration measurement with an empty drum. The controller calculates from the measured values, e.g. quotient corrected quantities from which e.g. By subtraction with the idle measurement values from this, the position and / or size of the imbalance can be determined.

This eliminates inherent asymmetries in the rotating parts and the measuring device. This is particularly advantageous when an angular velocity sensor is used which detects markings on a rotating body. In this case, the influence of inaccuracies in the position and / or size of the markings can be eliminated by the calculation with the idling measured values.

In a further preferred embodiment, the phase shift between the measured values and the position of the imbalance as a function of the rotational speed of the drum is stored in the memory of the washing machine. Since this phase shift is speed-dependent, the position of the imbalance can be determined by calculating the measured values with the phase shift as a function of the rotational speed of the drum.

• Fig. 1 einen schematischen Schnitt durch eine Waschmaschine,
• Fig. 2 eine schematische Ansicht der Trommel, des Winkelgeschwindigkeits-Sensors und der Steuerung,
• Fig. 3 die vom Winkelgeschwindigkeits-Sensor gemessenen Zeitwerte im Leerlauf,
• Fig. 4 die vom Winkelgeschwindigkeits-Sensor gemessenen Zeitwerte unter Last und
• Fig. 5 die Phasenverschiebung zwischen Messsignal und Unwuchtposition in Abhängigkeit der Drehzahl.

Further preferred embodiments will become apparent from the dependent claims and from the following description with reference to FIGS. Showing:

• 1 is a schematic section through a washing machine,
• 2 is a schematic view of the drum, the angular velocity sensor and the controller,
• 3 shows the idle times measured by the angular velocity sensor,
• 4 shows the time values measured by the angular velocity sensor under load and
• Fig. 5 shows the phase shift between the measuring signal and unbalance position as a function of the speed.

The washing machine shown in FIG. 1 has a drum 1 with a horizontal axis of rotation 2. The drum 1 is arranged in a tub 3. On the tub 3, a motor 4 is fixed, which drives the drum via a belt 5 and a pulley 6 in a known manner for rotation. The tub 3 is mounted with a suspension swinging in the washing machine.

In the illustrated embodiment, acceleration sensors 7 are mounted at the front and, opposite, at the rear end of the tub 3, which allow to determine a pivoting and / or tumbling movement of the tub. In addition, in the pulley 6, an angular velocity sensor 8 is provided, with which in the manner described below, the instantaneous angular velocity can be measured as a function of the rotational angle of the drum. Instead of or in addition to the acceleration sensors 7 and the angular velocity sensor 8, for example, distance sensors can also be used.

The sensors make it possible to detect an imbalance in the drum when spinning or at the beginning of the spin program.

Like in DE 43 13 819 described, can be counteracted an imbalance in the drum by targeted in a specific, attached to the drum tanks, a liquid, in the present case water injected.

If the imbalance is too great, the spinning process can also be interrupted, as already mentioned.

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

Each of the filling rings is connected via a filling tube 14 with one of the tanks 10 in combination.

A stationary injector 16 is provided to inject water into the packing rings. It comprises a water inlet 17 which supplies water to three valves 18. From the valves 18, the water passes through a drop section 19 to a respective tube 19 a, wherein the drop section 19, a backflow of water into the water inlet 17 prevented. The hoses 19a terminate in nozzles 19b, of which the water is injected into the individual filling rings 13a, b, c. The nozzles 19b are mounted on the tub 3 and on the oscillating system of the washing machine.

Fig. 2 shows schematically again the mechanical structure of the washing machine and its controller 20th

In particular, Fig. 2 shows the drum 1 and its axis of rotation 2. Also shown is a rotary body 21 which, as shown in Fig. 1, e.g. may be configured as a disc which is arranged on the pulley 6. The rotary body 21 rotates with the drum. He carries a variety of markings, which are configured in the embodiment shown as regularly distributed over the periphery of the rotating body teeth 22. The stationary on the rotary body 21 arranged angular velocity sensor 8 is able to detect the markings. In the present embodiment, the angular velocity sensor 8 is designed as a light barrier whose light path is interrupted by the teeth 22.

Instead of a light barrier, it is also possible to use another optical detector which detects the optically detectable markings on the rotary body 21. It may also be non-optical, e.g. Magnetic measurement methods are used in conjunction with appropriately designed markings.

From the signals of the angular velocity sensor 8 time periods between the markers are determined, for example in the form of the times between the signal transitions. FIG. 3 shows a corresponding series of measured values of durations t0 when the drum is idling, ie when the drum is empty. Since in the present example, the teeth are all the same size and equally spaced, the measured times are all about the same size. The variations shown in Fig. 3 are due to asymmetries in the structure of the rotating parts and inaccuracies in the manufacture of the teeth 22.

Each of the time values thus determined is inversely proportional to the instantaneous angular velocity of the drum 1.

If the drum is rotated under load and the load is distributed so that it comes to an imbalance, the instantaneous angular velocity of the drum 1 is dependent on the current angle of rotation. A corresponding measurement series of time periods t is shown in FIG. 4. As can be seen, the angular velocity is varied approximately sinusoidally.

The magnitude of the imbalance is reflected in the amplitude of the sinusoidal variation in Fig. 4, the position in the phase angle of the signal.

errechnet werden, wobei N die Zahl der Sektoren ist.In order to conclude from a given phase position of the measurement signal on the angular position of the unbalance, the sectors i according to FIG. 3 or 4 each have a rotation angle of the drum can be assigned. For this example, as part of the angular velocity sensor 8, a zero point sensor is provided which emits a signal when the drum is in a specific zero position. The one sector i associated rotational position α of the drum 1 can in this case $$\mathrm{\alpha }=360°\cdot \mathrm{i}/\mathrm{N}$$

where N is the number of sectors.

For an accurate measurement of amplitude and phase, it is advantageous to take into account the influence of said idling fluctuations according to FIG. As mentioned, these are due to asymmetries of the rotating parts and the angular velocity sensor 8 and therefore also lead to errors in the measurements under load.

Therefore, in an advantageous embodiment of the invention, the idling measured values t0 (i) according to FIG. 3 are stored as a function of the rotation angle α or of the sector i in a memory 23 of the controller 20, and the controller 20 is designed to determine the position and / or size of the unbalance by calculating the measured values t (i) according to FIG. 4 with the idling measured values t0 (i).

für den Messwert jedes Sektors bzw. Drehwinkels i gebildet werden, wobei sich die Summen über alle Sektoren j erstrecken. Für die Bestimmung von Amplitude und Phase der Unwucht wird sodann die so erhaltene Differenz d(i) verwendet.For a speed-independent correction, for example, the difference $$\mathrm{d}\left(\mathrm{i}\right)=\left(\mathrm{t}\left(\mathrm{i}\right)/{\displaystyle \Sigma \mathrm{t}\left(\mathrm{j}\right)}\right)-\left(\mathrm{t}0\left(\mathrm{i}\right)/{\displaystyle \Sigma \mathrm{t}0\left(\mathrm{j}\right)}\right)$$

are formed for the measured value of each sector or angle of rotation i, the sums extending over all sectors j. For the determination of amplitude and phase of the unbalance, the difference d (i) thus obtained is then used.

It is also conceivable to calculate the quotients $$\mathrm{q}\left(\mathrm{i}\right)=\mathrm{t}\left(\mathrm{i}\right)/\mathrm{t}0\left(\mathrm{i}\right),$$

These quotients q (i), like the differences d (i), are also independent of the no-load fluctuations.

The calibration values t0 (i) can be stored by the manufacturer in the memory 23, e.g. as part of the final test of a device. However, they may also be detected, at least in part, at a later time by the controller 20 and stored, e.g. by starting a particular calibration program during which measurements are performed on an empty drum. This is particularly useful when the angular velocity sensor 8 or the rotating body 21 must be replaced during maintenance or repair work.

As already mentioned, the exemplary embodiment shown in FIG. 1, in addition to the angular velocity sensor 8, also has two acceleration sensors 7. These different types of sensors are preferably used in addition. It turns out that at lower angular velocities, the angular velocity sensor 8 provides the most accurate results while the signals from the acceleration sensors 7 are relatively weak. At higher angular speeds, the signals of the acceleration sensors 7 become stronger, while those of the angular velocity sensor 8 lose their meaningfulness.

zuzuordnen.If the position of the imbalance is to be determined with the acceleration sensors 7, first the signals of the acceleration sensors 7 measured at certain times must be associated with the angular position of the drum 1. For this purpose, for example, the already mentioned zero point transmitter can be provided which emits a signal when the drum is in a specific zero position. Starting from the time tn, at which this zero position was reached for the last time, and the current speed D of the drum 1 (which can be determined, for example, via the zero point encoder), it is possible to measure the acceleration sensors at a given time tx Angular position α according to the formula $$\mathrm{\alpha }=\left(\mathrm{t}\mathrm{x}-\mathrm{t}\mathrm{n}\right)\cdot \mathrm{D}\cdot 360°$$

assigned.

• Bei tiefen Winkelgeschwindigkeiten der Trommel, d.h. wenn die Winkelgeschwindigkeit so gross ist, dass die Wäsche in der Trommel nicht mehr fällt sondern an die Trommelwand angedrückt ist, aber die Drehzahl noch deutlich unter der tiefsten Resonanzfrequenz der elastischen Aufhängung von Trommel und Bottich ist, so beträgt die Phasenverschiebung zwischen dem Maximum des Signals α0 und der Lage der Unwucht αU beispielsweise ca. -90°.
• Bei sehr hohen Winkelgeschwindigkeiten deutlich über der.stärksten Resonanzfrequenz der Aufhängung der Trommel 1 dreht sich die Phasenverschiebung um 180°, d.h. im vorliegenden Beispiel auf ca. +90°.

However, it should also be taken into account that the phase shift, for example, between the angle α ₀ , at which the signal of one of the acceleration sensors 7 has its maximum, and the angular position α _{U of} the imbalance, is dependent on the angular velocity of the drum 1:

• At low angular velocities of the drum, ie when the angular velocity is so high that the laundry in the drum no longer falls but is pressed against the drum wall, but the speed is still well below the lowest resonance frequency of the elastic suspension of the drum and tub is so the phase shift between the maximum of Signal α0 and the position of the unbalance αU, for example, about -90 °.
• At very high angular velocities clearly above the highest resonance frequency of the suspension of the drum 1, the phase shift rotates by 180 °, ie in the present example to about + 90 °.

A corresponding course of the phase shift is shown in FIG. 5. As can be seen, the course of the phase shift differs in practice from a simple arctan behavior, since the suspension has several resonance frequencies and several degrees of freedom.

In order to be able to deduce the position of the imbalance from the phase position of the sinusoidal 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 as a function of the rotational speed is in a memory 25 of the controller 20 the drum 1 is stored. This can e.g. in the form of individual values according to FIG. 5 or in the form of the parameters of a curve adapted to the values according to FIG. 5. The phase shift stored in the memory 25 as a function of the rotational speed of the drum 1 forms calibration values with which the position measurements can be corrected.

To carry out the correction, the microprocessor 24 of the controller 20 determines the phase position of the measured acceleration values, for example by means of Fourier transformation or cosine transformation, wherein the amplitude can also be determined in the same calculation step. To the determined phase position, the microprocessor 24 adds the phase shift according to the calibration values from memory 25 to this speed, resulting in the angular position of the imbalance. Depending on this angular position, for example, the tanks 10 can now be filled. For this purpose, the controller 20 outputs control signals corresponding to a valve control 26.

Instead of acceleration sensors 7, which measure axial and / or radial accelerations of the drum 1 or of the oscillating system, it is also possible to use position sensors which measure the axial or radial deflections of the drum 1, the tub 3 or other parts of the oscillating system , Again, however, the above-mentioned phase correction is again to achieve accurate measurements.

Preferably, the mean value of the signals of the acceleration sensors 7 is used for processing. This produces a signal independent of tilting of the drum.

The calibration values, i. the course of the phase shift according to FIG. 5 can be stored by the manufacturer in the memory 25 by carrying out measurements on a drum with a known imbalance attached to a defined position. In this case, the same calibration values can be used per se for all devices of the same type of the same type.

Claims (10)

Washing machine with
a drum (1) rotating about an axis of rotation (2),
a measuring device (7, 8) for detecting an imbalance in the drum (1) with which measured values can be generated as a function of the rotational position (α) of the drum, and
a controller (20) for determining a position and / or size of the imbalance from the measured values,
characterized by a memory (23, 25) for storing calibration values, wherein the controller (20) is designed to determine the position and / or size of the unbalance by calculating the measured values with the calibration values. Washing machine according to claim 1, characterized in that in the memory (23, 25) idle measured values (t0) are stored as a function of the rotational position (α) and that the controller (20) is configured to the position and / or size of the imbalance by calculating the measured values measured with the idle measured values. Washing machine according to claim 2, characterized in that the controller (20) is adapted to determine a quotient (q) of the measured values measured (t) and of the respective no-load measured values (t0). Washing machine according to one of the preceding claims, characterized in that in the memory (23, 25) a phase shift (phi) between the measured values and the position of the imbalance as a function of the rotational speed (D) of the drum is stored and that the controller (20) thereto is designed to determine 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 controller (20) is designed to determine at least part of the calibration values when the drum (1) is empty 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 rotational position of the drum. Washing machine according to claim 6, characterized in that the angular velocity sensor (8, 21, 22) comprises a rotary body (21) and a detector (8), wherein the rotary body (21) rotates with the drum (1) and a plurality of markers (22), and wherein the detector (8) is stationarily arranged on the rotating body (21) and detects the marks (22). Washing machine according to claim 7, characterized in that the detector (8) is an optical detector and the markings (22) are optically readable marks, and in particular that the detector (8) is a light barrier with a light path interruptible by the markings (22) , Washing machine according to one of the preceding claims, characterized in that the measuring device 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 surrounding the drum, non-rotating tub (3) and at least a portion of the measured 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 tub (3), wherein an average value of the signals of the acceleration sensors (7) is determined.

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