EP0750065B1 - Device and method for determining the unbalance in a drum washing machine - Google Patents

Description

The invention relates to a device for determining the unbalance of a loaded drum in a washing machine with a swinging suds container in which the Drum rotatably supported and driven by a motor. In addition, the Invention a method for determining the unbalance in such a washing machine. The invention also relates to a method for controlling the spinning process such a washing machine.

With drum washing machines, unbalanced laundry distribution creates imbalances. These cause strong movements of the, especially during the spinning process swinging suspended suds container. In extreme cases, this can lead to striking the Suds container on the housing, excessive bearing stress and thus damage of the machine. To prevent unbalanced damage to the Washing machine is known to sense the size of the imbalance and the skidding Abort a predetermined unbalance threshold to redistribute to do the laundry.

For sensing the unbalance size, it has already been proposed (EP 0 091 336 A1) that Evaluate error signal of the control deviation for unbalance determination. With this procedure is just a sensation of unbalance in the speed range below the resonance speed possible. At high speeds (> 300 rpm) the unbalance size can no longer be determined, since the control deviations are hardly measurable here. For this reason a final decision on the further course of the spin program already in subcritical speed range. This often leads to security reasons an unnecessary termination of the spinning process. In the supercritical area above the resonance speed, the unbalanced laundry is usually dewatered and thus reduces the unbalance.

Furthermore, it is known in the above-mentioned washing machines to cancel spin starts through additional safety measures (increased damping, better bearings) restrict. However, this leads to an increase in the cost of production.

From DE 30 02 786 A1 a washing machine with a level sensor is known which consists of a riser arranged in the drain area of the tub and connected to it Pressure measuring device exists.

The invention presents the problem of an apparatus and a method for determination to disclose the imbalance of the type mentioned at the outset, which is simple and can be used in a wide range of speeds. It turns out in particular the invention the problem, a method for controlling the spinning process Washing machine using a device for determining the unbalance of the input mentioned type, taking into account the drainage of unbalance becomes.

• Die gewünschte Schleuderenddrehzahl wird häufiger erreicht;
• die Lebensdauer der Waschmaschine wird durch die geringere Belastung verlängert;
• die Sicherheitsvorkehrungen an den Verschleißteilen der Waschmaschine können bei gleichbleibender Lebensdauer verringert werden.

According to the invention, these problems are solved by a device or by methods having the features of the respective independent claims. The following advantages are achieved with the device designed according to the invention for determining the unbalance and with the use of the method according to the invention:

• The desired final spin speed is reached more often;
• the service life of the washing machine is extended by the lower load;
• The safety precautions on the wearing parts of the washing machine can be reduced while maintaining the same service life.

An expedient further development of the device results from the arrangement of a membrane transverse to the flow direction in the riser. This is a simple, easy to manufacture Arrangement for generating an unbalance-dependent pressure signal component. Is next to it it is advantageous to weight the membrane to accommodate the dynamic signal component to reinforce in a simple way. The arrangement of openings in the membrane Avoid falsification of the quasi-static signal for level measurement.

In a further advantageous embodiment, there are several devices in the riser for generating pressure signals dependent on the vibrations of the tub arranged, their natural frequencies at different speed ranges of the drum speed are coordinated. This ensures that in these speed ranges a sufficiently amplified dynamic signal component is generated in each case.

In an advantageous embodiment of the method according to the invention for determining the The pressure sensor of the washing machine's level sensor is used. Hereby the cost of an additional sensor is saved.

Figur 1

eine schematische Darstellung einer Waschmaschine mit einer erfindungsgemäß ausgebildeten Vorrichtung zur Bestimmung der Unwucht;

Figur 2

die Steigleitung bei einem anderen Ausführungsbeispiel der Erfindung als vergrößerte Einzelheit;

Figur 3

den Ablauf eines Schleuderprogramms in Abhängigkeit von der sensierten Unwucht anhand eines Drehzahl-/Zeit-Diagramms

An embodiment of the invention is shown purely schematically in the drawings and is explained in more detail below. Show it:

Figure 1

a schematic representation of a washing machine with an inventive device for determining the unbalance;

Figure 2

the riser in another embodiment of the invention as an enlarged detail;

Figure 3

the sequence of a spin program depending on the sensed imbalance using a speed / time diagram

The drum (1) is rotatably mounted in the tub (2) in a known manner. It is through a motor (3) driven. A tachometer generator (4) coupled to the motor (3) engages Engine speed signal for regulation.

To measure the water level there is a riser at the drainage area (5) of the tub (2) (6) arranged at the other end of which there is an analog pressure sensor (7). Of the Water supply is shown in simplified form in the drawing, so that only the inflow over the Detergent drawer (8) is symbolized. The signal outputs (9) of the tachometer generator (4) and the analog pressure sensor (7) are with the program control (10) of the washing machine connected.

By arranging a membrane (13) loaded with a weight (14) in the riser (6) in front of the pressure sensor (7) a system is created which, in addition to the quasi-static Pressure changes caused by level differences in the washing liquid in the tub (2) are also caused by accelerations of the tub solution system (2) - Riser (6) reacts. Because these accelerations are primarily due to unbalance Deflections of the drum (1) are caused, represents the dynamic signal component the pressure sensor (7) the size of the unbalance of the laundry in the drum (1). By making openings (11) in the membrane (13) a falsification of the quasi-static signal component prevented.

Figure 2 shows an enlarged view of a riser (6) in which two weighted Membranes (13a, b) are arranged. These have the choice of certain weights (14) and / or spring constants of the membrane (13) natural frequencies that are different Speed ranges are matched.

A high-resolution pressure sensor (7), preferably an analog one, must be used as the pressure sensor (7) Pressure sensor (7) can be used to detect the dynamic signal components. This means both the water level and the deflection of the tub due to unbalance (2) can be sensed, the program control (10) must separate the quasi-static and the dynamic signal component. For this reason a microprocessor control (10) is preferably used as the control device.

FIG. 3 shows a speed-time diagram to explain a method for controlling the spinning process. The drum (1) is first accelerated from the washing speed n _W (approx. 50 rpm) to a first measuring speed n ₁ (<100 rpm) below the resonance speed n _R (300-500 rpm). The laundry must lie against the drum jacket at this speed (n ₁ ), so that any imbalances have already formed. When this first measuring speed (n ₁ ) is reached at time t ₁ , the unbalance is determined by the microprocessor control (10). This can advantageously be done by the method described above. If the unbalance determined is below a predetermined unbalance limit value, the drum (1) is further accelerated to a second measuring speed n ₂ (800 rpm) above the resonance speed n _R (-). Since the unbalance is checked again here, the unbalance limit can be set significantly higher than in the known single-stage unbalance determination method.

If the unbalance limit value is exceeded during the measurement at the first point in time t ₁ , the microprocessor control (10) brakes the drum (1) to such an extent that the contact speed n _{A is} undershot and the laundry can be redistributed. Then a new spin starts (• - • - •).

When the second measuring speed (n ₂ ) is reached at time t ₂ , the unbalance is determined again by the microprocessor control (10). The drum (1) is then accelerated to a final speed n _E , which depends on the size of the imbalance now prevailing.

• der Schleuderprozeß abgebrochen;
• die Drehzahl reduziert,
• die Drehzahl beibehalten,
  oder
• die Drehzahl erhöht werden.

The device shown in FIG. 2 is particularly suitable for determining the two unbalance values in different speed ranges. However, it is also possible to use the method according to the invention for determining the unbalance only in the supercritical speed range and to evaluate the control deviation of the motor (3) in the subcritical speed range as described at the beginning. In addition, it is possible to take ₂ further unbalance measurements after the second measuring speed n. In this way, the speed curve can be graded. Here, a speed n _i is first controlled, then the unbalance value U _{i is} determined and then a speed n _i (U _i ) is controlled. If the computer of the microprocessor control (10) is sufficiently fast, this gradation can be resolved to such an extent that the unbalance is monitored almost continuously and a speed curve dependent on the respective unbalance value is selected. Depending on the degree to which a specified unbalance limit is exceeded,

• the spinning process was interrupted;
• reduces the speed,
• maintain the speed,
  or
• the speed can be increased.

The above-described method can reduce the unbalance at any time be taken into account by drainage during spin-up.

Claims (6)

1. Device for the determination of imbalance of a loaded drum (1) in a washing machine with a vibratingly suspended caustic container (2) in which the drum (1) is rotatably mounted and is driven with the help of a motor (3), characterised in that in a level sensor, already known in itself, comprising a riser (6) arranged in the discharge region of the caustic container (2), to which a pressure sensor (7) is connected, there is arranged in the riser (6) at least one device for the generation of a pressure signal which is dependent upon the vibrations of the caustic container (2).
2. Device according to claim 1, characterised in that in the riser (6) at least one membrane (13) is arranged transversely to the direction of through-flow.
3. Device according to claim 2, characterised in that the membrane(s) (13) is/are provided with a weight (14).
4. Device according to claim 2 or 3, characterised in that the membrane(s) (13) is/are provided with at least one opening (11).
5. Device according to one of the claims 1 to 4, characterised in that in the riser (6) there are arranged several devices for the generation of pressure signals which are dependent upon the vibrations of the caustic container (2), the natural frequencies of said pressure signals being coordinated to different rotational speed ranges of the drum rotational speed.
6. Method for the determination of imbalance of a loaded drum (1) of a washing machine with a vibratingly suspended caustic container (2) in which the drum (1) is rotatably mounted and is driven with the help of a motor (3) characterised in that the dynamic portion of the signal of a pressure sensor (7), which is connected to the caustic container (2), is evaluated, the pressure fluctuations generated from the vibrations of the caustic container (2) being referred to as a measure of the imbalance.

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