EP0302319B1 - Method for reducing the laundry unbalance in washing machines - Google Patents

Description

The invention relates to a method for reducing the laundry imbalance in washing machines according to the preamble of claim 1.

After the washing and rinsing phase has ended, the items to be washed are loosened before the actual spin cycle and then redistributed in accordance with a laundry imbalance correction method, i.e. the wet items of laundry must lie as evenly as possible on the inner circumference of the laundry drum.

From DE-OS 34 16 639 a "method for controlling the spin program of a washing machine" using a microcomputer control, an imbalance detection device and a speed control device for the drive motor of the laundry drum is known. With the help of the microcomputer control, the centrifugal process is carried out depending on any imbalance. Different loads as well different supply voltages are recorded and taken into account in the speed control of the drive motor. The washing drum of the washing machine is brought from a low wash speed to a higher contact speed range. During this contact phase, the laundry is distributed evenly and the speed or current consumption behavior of the drive motor is evaluated via an imbalance detection device and fed to a microcomputer. The result of the evaluation is compared with stored reference values and then determines the further speed curve of the spinning process.

Measurements have shown that with large loads of laundry and absorbent laundry, even if they are evenly distributed in the laundry drum, errors occur in the unbalance measurement. This means that the greater the so-called symmetrical base load (evenly distributed weight), the greater the incorrect measurement of the unbalance size of the laundry. In the known method, larger laundry imbalances are spun which the microcomputer does not recognize. In the case of medium unbalance values, which the microcomputer recognizes correctly, spinning is only carried out at a reduced speed and the washing water is not thrown out of the laundry sufficiently. The final spin speed is only increased when the imbalance is low.

The invention is based on the object of detecting the laundry imbalance even with large laundry loads and absorbent laundry by reducing the symmetrical base load more precisely. The unbalance detection should continue to be optimized by measuring the actual engine speed fluctuations.

This object, according to the invention, is achieved by the characterizing features of claim 1.

The advantages that can be achieved with the invention are, in particular, that even large laundry loads and heavy, absorbent laundry are fully thrown out without major imbalance values. Another advantage is a reduction in ground forces during centrifugal operation and, as a result, material and cost savings by reducing the vibrating mass.

• Fig.1 Die Prinzip-Skizze einer Waschmaschine mit digitaler Drehzahlregelung für den Antriebsmotor sowie mit Feuchtigkeitssensor im Abflußschlauch,
• Fig.2 das Blockschaltbild des digitalen Drehzahlreglers für den Antriebsmotor,
• Fig.3 ein Antriebsmotordrehzahl-Zeitdiagramm,
• Fig.4 ein Kurvendiagramm mit der Unwucht (G) in Abhänigkeit von der Antriebsmotordrehzahl-Istwertschwankung (Δ n) und der symmetrischen Grundlast als Parameter.

An embodiment of the invention is shown in the drawings and will be described in more detail below.
Show it:

• Fig. 1 The basic sketch of a washing machine with digital speed control for the drive motor and with a moisture sensor in the drain hose,
• 2 shows the block diagram of the digital speed controller for the drive motor,
• 3 shows an engine speed diagram,
• 4 shows a curve diagram with the unbalance (G) as a function of the actual engine speed fluctuation (Δ n) and the symmetrical base load as parameters.

The washing machine shown schematically in Fig. 1 has a tub (1), a laundry drum (2) and a digital speed controller (3) for a drive motor (4). The wash liquor is discharged using a drain pump (5) through a drain hose (6). The drain hose (6) contains a moisture sensor (7) in the form of a water flow meter, not shown, near its elbow.

2, a tachometer generator (8) is driven by the drive motor (4). The tachometer generator (8) measures the actual speed fluctuations (9) of the drive motor (4), which represent a measure of the imbalance (G) and transmits them to a microcomputer (µP).

In the present method, after the washing and rinsing phase has ended, the spin speed setpoint value (10) is only thrown up if a prescribed minimum unbalance limit (11) entered into the microcomputer (μP) is not exceeded during a laundry distribution phase or a known laundry imbalance correction system .
If, on the other hand, a maximum unbalance limit is exceeded (as can be the case with large laundry loads and absorbent laundry), the laundry is redistributed in accordance with the known laundry imbalance correction system (the laundry distribution phase). If the laundry is now distributed in such a way that the maximum unbalance limit is undershot, it is spun for a certain spin time at a certain spin speed, which is, however, less than the desired spin speed value (10). This removes moisture from the laundry and thus reduces its weight or the symmetrical base load and thus the unbalance (G). The laundry is then loosened up by a certain number of washing reversing cycles and then redistributed again in a laundry distribution phase, the laundry unbalance correction system, until the minimum unbalance limit (11) is undershot. Only then will the final spin speed (10), which is applied to the microcomputer (µP), be flung up.

3 and 4 illustrate the previously described work processes:

Measuring the unbalance (G)

Result: G1 -maximum unbalance limit exceeded, then the laundry distribution phase and measuring the unbalance (G)
Result: G2 - the maximum unbalance limit is now undershot, but the minimum unbalance limit is still exceeded, then:

First phase of dehumidification and reduction of the symmetrical base load

Result: G3 minimum unbalance limit still exceeded (the value G3 is now determined very precisely because it was determined with a reduced symmetrical base load. As already mentioned at the beginning, unbalance determinations with high symmetrical base loads are subject to errors), then:
Loosen the laundry by a certain number of washing reversing cycles and a new washing distribution phase and measuring the unbalance (G)
Result: G4 (exact value) - minimum unbalance limit (11) undershot, then

Throwing up to target spin speed value (10)

The dewatering effect of the laundry to reduce the residual moisture for the first time (first moisture removal phase with spinning below the target spin speed value (10)) is measured by the moisture sensor (7) in the drain hose (6) with the help of a water quantity counter and transmitted to the microcomputer (µP), which thereby transmits the Spin time and / or the Spin speed affected. This spin speed can also reach the desired spin speed value (10). The microcomputer (µP) also determines the number of washing reverse cycles during loosening of the laundry, based on the actual speed fluctuations (9) measured by the tachometer generator (8). The actual speed fluctuations (9) in this phase are not a measure of the imbalance (G) but a measure of the degree of loosening of the laundry.

Claims (1)

1. Method of reducing the laundry imbalance in washing machines with a tacho-generator coupled rigidly to the drive motor, with a microcomputer-controlled, digital speed control, by means of which, before acceleration to the specified spinning speed reference value during a laundry distribution phase, at a spinning speed which is below the spinning speed reference value, a laundry imbalance can be measured by means of the speed actual value fluctuations of the drive motor detected by the tacho-generator and with which, at laundry imbalance values above a maximum imbalance limit, the laundry can be loosened by reversing cycles, in which case the value of the laundry imbalance (G1) detected at the beginning and with a high symmetrical base load can be reduced to the value (G2) by a further laundry distribution phase, characterised in that the drum is only accelerated to the spinning speed reference value when the high symmetrical base load and the value (G2) have been reduced, by means of a moisture extracting phase directly and continuously following the laundry distribution phase with a spinning speed which is above the spinning speed of the preceding laundry distribution phase, to a lower symmetrical base load and the laundry imbalance has been reduced to the value (G3), in which case the quantity of water per unit time occurring during the moisture extraction phase is detected by means of a moisture sensor (7) mounted in the drainage hose (6) and, as a measure of the speed level and spinning duration, the value (µP) is supplied to the microcomputer, and then with this reduced symmetrical base load with the laundry imbalance value (G3), a number of reversing movements were carried out during a laundry loosening phase, this number being determined on the basis of the level of drive motor speed actual value fluctuations (Δn₂_,₃) until this reduced symmetrical base load was reduced in a new laundry distribution phase from the imbalance value (G3) to the imbalance value (G4), which is below a minimum imbalance limit.

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