EP2185763B1 - Method for eliminating foam in a drum washing machine and drum washing machine suitable therefor - Google Patents

Description

The invention relates to a method for removing foam in a drum washing machine and a drum washing machine suitable for this purpose. In particular, the invention relates to a method for removing existing foam in a tub of a drum washing machine with a program control for controlling a program sequence comprising a sequence of steps comprising adding water and rotating the drum and a drum washing machine suitable therefor.

In conventional drum washing machines, high speed is thrown after the main wash and the rinse cycles. If a lot of foam is present or is produced during spinning, the lye pump does not promote the foam-lye mixture. The spin is therefore not performed in foam detection in the pumping or stopped in the event of foam detection during spin. In addition, the foam can escape from the openings of the tub as the tub ventilation and the filling hose. Early foam detection and efficient measures to remove the foam are therefore important.

According to the DE 41 04 151 A1 the foam is destroyed by switching on a heater. In order to destroy the foam in the wider vicinity of the heater, the drum is rotated slowly so that more foam passes to the heater and is destroyed there by supplying heat.

In the DE 43 34 969 A1 a device for the destruction of detergent foam is described which has a device for generating hot air, which is introduced through a feed line in the tub wall between the tub and the drum.

In addition, methods for removing foam in a tub of a drum type washing machine are known from DE 102 34 472 A1 as well as the DE 198 36 248 A1 known.

The DE 102 34 472 A1 describes a method for removing foam in a tub of an electronically controlled drum washing machine as a result of a program step, which is provided for dehydrating the tub, with a arranged at the bottom of the tub lye drain system with a drain pump and with a sensor for determining the height of the liquid in the tub. The course of the sensor signal (P) is recorded during the operation of the drain pump, contains a gradient Ap _n / .DELTA.t _n compared to Ap _n-1 / .DELTA.t _n-1, indicating the presence of foam, whereupon one of the Gradient-matched foam treatment measure is initiated, for example, supplying a certain amount of water or changing the speed of the laundry drum.

In the EP 0 278 239 A1 Excessive foaming in the main wash, observed during the heating of wash liquor in the tub, is eliminated by adding a limited amount of cold water and / or by temporarily turning off the liquor heater.

The EP 1 063 341 A2 describes a washing machine with a tub and a rotatable washing zone, which has a detection device for determining the state of the wash liquor and the output of a signal and a control device for receiving this signal and for issuing predetermined commands for the washing of textiles. One such condition is a so-called "suds lock", a foam barrier. This results in a pronounced foaming a large tensile force on the drum, which leads to a significant decrease in the rotational speed of the drum. The operation of the washing machine should then be adjusted.

The EP 0 268 155 A2 describes a program-controlled washing machine with a drum in a tub, from which the washing and rinsing is discharged by means disposed in a drain line drain pump, wherein the drain line a pipe is connected to a sensor whose output signals an indication of the foaming during the spin process are and constitute control variables for the drive motor of the laundry drum and thus for the control of the spin speed. For example, the spin speed is reduced until the foam limit falls below again.

The EP 0 724 036 A1 describes a washing and drying machine for clothes equipped with a foam reducing arrangement. The machine comprises a tub and a rotatably mounted drum therein a pressure sensor and processing and control means which receive the signal of the pressure sensor as a measure of the pressure in an air chamber and periodically reproduce its mean value. Upon exceeding a predetermined difference between successive mean pressures corresponding to a high foaming condition, a predetermined foaming control washing program is modified. The modification may consist in a reduction in the rotational speed of the drum or an addition of a larger amount of water in at least one rinsing phase.

Moreover, in customary processes, the foam is usually removed by means of adapted rinsing baths with the greatest possible avoidance of the introduction of mechanical energy (for example due to long downtimes of the drum).

A disadvantage of the known methods is that they sometimes lead to a considerable lengthening of the overall washing program, greatly increased water consumption and a poor spinning result.

The object of the invention was therefore the. To provide a method by which the foam produced in a washing machine can be combated more effectively than with conventional methods. In addition, it was an object of the invention to provide a drum washing machine suitable for carrying out this method.

According to the invention, these objects are achieved by a method having the features of claim 1 and by a drum washing machine having the features of claim 12. Advantageous embodiments of the invention are listed in the subclaims.

The present invention is therefore a method for removing detected foam in a drum washing machine with a program control for controlling a program flow, a rotatably mounted in a tub drum, a water inlet system, arranged at the bottom of the tub lye drain system with a drain pump, a drive motor for the Drum and a sensor for determining a foam level h _s and / or a negative temporal gradient of the foam level (ie _s / dt) of a liquid-air mixture in the tub, wherein detected by the sensor foam during a Centrifugal start-up of the drum, ie a continuous or discontinuous increase in the speed of the drum, continuously or discontinuously switched on a small amount of water is added at continuously or discontinuously switched liquor pump, wherein in a spin the foam level h _s monitored by the sensor and depending on the foam level h _s a Controlled speed of the drum, so that with an increase in the foam level h _s, the speed is reduced, while maintaining the foam level h _s, the speed is maintained and / or with a reduction in the foam level h _s, the speed is increased, and a maximum amount of water during the spin-up is adapted to the amount of laundry in the drum.

The water supply system is generally directed to the laundry located in the drum or into a space between the drum and the tub.

In the process according to the invention, a small amount of water is generally added after a successful pumping out of washing liquor, continuously or discontinuously.

For this purpose, for example, depending on the amount of laundry loaded in a drum, a quantity of water can be preset. Alternatively, a known load detection can be carried out in the drum washing machine. For example, load detection can be performed on the amount of water that has accumulated and, in particular, on a comparison between measured hydrostatic pressures and the amount of water that has been admitted.

When a maximum foam level h _smax is _exceeded , the speed is generally reduced until the drum stops. The maximum foam level h _smax is preferably adapted to the amount of laundry in the drum.

The sensor may be a single sensor or a system of multiple sensors. Likewise, the term sensor includes besides the actual sensor preferably also a corresponding system for registration and transmission of the data to a program control.

In preferred embodiments of the invention, the sensor is an optical measuring system, a conductometric measuring system, a capacitive measuring system or a pressure measuring system.

In the event that a pressure measuring system is used, this is preferably also used for the regulation of a water level during a wash and / or rinse cycle.

When using a pressure measuring system, as a measure of the foam level h _s and / or a negative time gradient of the foam level (ie _s / dt) of a liquid-air mixture in the tub, preferably a hydrostatic pressure p and a negative time gradient of the hydrostatic pressure ( dp / dt) of a liquid-air mixture in the tub.

In a preferred embodiment of the invention, the continuous amount of water is 0.5 to 1.5 l / min. In a preferred alternative embodiment, the discontinuously tapered amount of water is 0.2 to 2 l in each case.

• A) Bei Stillstand oder langsamem Drehen der Trommel, vorzugsweise bei Stillstand der Trommel, Abpumpen der Flüssigkeit-Luft-Mischung und nach einer vorgegebenen Zeit Δt₁ Messen des hydrostatischen Drucks p und/oder des negativen zeitlichen Gradienten des hydrostatischen Drucks (-dp/dt);
• B) Vergleich des in Schritt A) gemessenen hydrostatischen Drucks p mit einem vorgegebenen Schwellenwert p₁ für den hydrostatischen Druck p und/oder Vergleich des in Schritt A) gemessenen negativen zeitlichen Gradienten des hydrostatischen Drucks (-dp/dt) mit einem vorgegebenen Schwellenwert (-dp/dt)₁ für den negativen zeitlichen Gradienten des hydrostatischen Drucks (-dp/dt), und
• C) bei Vorliegen der Bedingungen (-dp/dt) < (-dp/dt)₁ und p > p₁ Durchführen der folgenden Schritte C1) bis C3),
• C1) Zugabe einer vorgegebenen kleinen Wassermenge ΔV_i,
• C2) Drehen der Trommel mit einer vorgegebenen niedrigen Drehzahl U₁, vorzugsweise in abwechselnden Richtungen, ggf. unterbrochen von einem Stillstehen der Trommel,
• C3) Abpumpen der Flüssigkeit-Luft-Mischung, Messen des hydrostatischen Drucks p und Wiederholen von Schritt B),
• D) bei Vorliegen der Bedingung (-dp/dt) > (-dp/dt)₁ oder p < p₁ Durchführen der folgenden Schritte D1) bis D4)
• D1) bei einem Druck p, der größer als ein vorgegebener Druck p₂ ist, wobei p₂ < p < p₁ gilt, Zugabe einer vorgegebenen kleinen Wassermenge ΔV_j und Drehen der Trommel bei eingeschalteter Pumpe mit einer Drehzahl U₂ > U₁, wobei nach einem vorgegebenen Zeitintervall Δt₂ der hydrostatische Druck p gemessen wird und in Abhängigkeit von einer Änderung des hydrostatischen Drucks p nach Ablauf des Zeitintervalls Δt₂ einer der folgenden Schritte D2) bis D4) durchgeführt wird;
• D2) bei einem Ansteigen des hydrostatischen Drucks p Zugabe einer vorgegebenen kleinen Wassermenge AV_j, Herabsetzen der Drehzahl U₁ um einen Betrag ΔU_i und Drehen der Trommel mit der Drehzahl U₁-AU_i;
• D3) bei einem Gleichbleiben des hydrostatischen Drucks p Zugabe einer vorgegebenen kleinen Wassermenge ΔV_j und Drehen der Trommel mit unveränderter Drehzahl U₁;
• D4) bei einer Abnahme des hydrostatischen Drucks p Zugabe einer vorgegebenen kleinen Wassermenge ΔV_j, Erhöhen der Drehzahl U₁ um einen Betrag ΔU_j und Drehen der Trommel mit der Drehzahl U₁-ΔU_j;
• D5) Messen des hydrostatischen Drucks p nach Ablauf eines Zeitintervalls Δt₂, und für den Fall, dass p > p₁ ist und eine Summe Σ ΔV_i,j der zugegebenen Wassermengen ΔV_i,j kleiner als eine vorgegebene maximal zulässige Wassermenge W_z ist, Durchführung eines der Schritte D2) bis D4) in Abhängigkeit von der nach dem Zeitintervall Δt₂ eingetretenen Änderung des Drucks;
• E) für den Fall ΣΔV_i,j > W_z Wiederholen der Schritte A) bis D5);
• F) bei einem Druck p < p₂ Erhöhung der Drehzahl U der Trommel bis zum Erreichen einer vorgegebenen maximalen Drehzahl U_max.

In a very particularly preferred embodiment, the invention is a method for removing detected foam in a drum washing machine with a program control for controlling a program flow, a rotatably mounted in a tub drum, a water inlet system, arranged at the bottom of the tub lye drain system with a drain pump, a Drive motor for the drum, a heater and a sensor for determining a hydrostatic pressure p and / or a negative time gradient of the hydrostatic pressure (dp / dt) of a liquid-air mixture in the tub, wherein the following steps A) to F) be performed:

• A) At standstill or slow rotation of the drum, preferably at standstill of the drum, pumping the liquid-air mixture and after a given time .DELTA.t ₁ measuring the hydrostatic pressure p and / or the negative temporal gradient of the hydrostatic pressure (-dp / dt );
• B) Comparison of the hydrostatic pressure p measured in step A) with a predetermined threshold value p ₁ for the hydrostatic pressure p and / or comparison of the negative temporal gradient of the hydrostatic pressure (-dp / dt) measured in step A) with a predefined threshold value ( -dp / dt) ₁ for the negative time gradient of the hydrostatic pressure (-dp / dt), and
• C) in the presence of the conditions (-dp / dt) <(-dp / dt) ₁ and p> p ₁ performing the following steps C1) to C3),
• C1) adding a predetermined small amount of water ΔV _i ,
• C2) rotating the drum at a predetermined low speed U ₁ , preferably in alternating directions, possibly interrupted by a standstill of the drum,
• C3) pumping out the liquid-air mixture, measuring the hydrostatic pressure p and repeating step B),
• D) in the presence of the condition (-dp / dt)> (-dp / dt) ₁ or p <p ₁ performing the following steps D1) to D4)
• D1) at a pressure p which is greater than a predetermined pressure p ₂ , where p ₂ <p <p ₁ , adding a predetermined small amount of water ΔV _j and rotating the drum with the pump switched on at a speed U ₂ > U ₁ , wherein after a predetermined time interval .DELTA.t _2, the hydrostatic pressure p is measured and in response to a change in the hydrostatic pressure p after the expiration of the time interval .DELTA.t ₂ one of the following steps D2) to D4) is performed;
• D2) with an increase in the hydrostatic pressure p adding a predetermined small amount of water AV _j , reducing the speed U ₁ by an amount ΔU _i and rotating the drum at the speed U ₁ -AU _i ;
• D3) at a constant hydrostatic pressure p addition of a predetermined small amount of water .DELTA.V _j and rotating the drum with unchanged speed U ₁ ;
• D4) with a decrease in the hydrostatic pressure p adding a predetermined small amount of water ΔV _j , increasing the speed U ₁ by an amount ΔU _j and rotating the drum at the speed U ₁ -ΔU _j ;
• D5) measuring the hydrostatic pressure p after a time interval Δt ₂ , and in the event that p> p is ₁ and a sum Σ ΔV _{i, j of} the added amounts of water .DELTA.V _{i, j is} less than a predetermined maximum allowable amount of water W _z Performing one of the steps D2) to D4) as a function of the change in pressure which has occurred after the time interval Δt ₂ ;
• E) for the case ΣΔV _{i, j} > W _z repeating steps A) to D5);
• F) at a pressure p <p ₂ increase the speed U of the drum until reaching a predetermined maximum speed U _max .

In the aforementioned step A), the slow rotation of the drum is preferably carried out at a speed in the range of 10 to 40 revolutions per minute, for example, at 35 revolutions per minute. In addition, the negative temporal gradient of the hydrostatic pressure (-dp / dt) is advantageously measured in step A). The presence of a liquid-air mixture (foam) generally manifests itself in a plot of hydrostatic pressure p versus time t during pump down by a more or less pronounced kink which indicates a decrease in the negative time gradient of hydrostatic pressure (-dp / dt).

In a preferred embodiment of the inventive method, the predetermined amount of water .DELTA.V _i and / or .DELTA.V _{j is} adapted to a loading of the drum with laundry.

In general, the predetermined amount of water ΔV _i and / or ΔV _{j is} 0.5 to 2 liters. The amounts of water ΔV _i and ΔV _j may be the same or different. Preferably, the amounts of water ΔV _i and ΔV _j are set so that both are equal.

According to the invention, the low speed U _{1 is} preferably in the range of 15 to 45 revolutions per minute. Preferably, the speed U _{2 is} at least 100 revolutions per minute.

In the aforementioned preferred method, steps C2) and C3) are preferably carried out simultaneously.

In step F), at a pressure p <p _2, the rotational speed U of the drum is increased until reaching a predetermined maximum rotational speed U _max , which is preferably in the range from 900 to 1100 revolutions per minute. The increase in speed can be gradual or in one or more stages.

The time intervals Δt ₁ and Δt ₂ may be the same or different. Preferably, they are the same.

Before carrying out the process according to the invention, a foam detection can be carried out.

Usually, the presence of foam (liquid-air mixture) is detected by a build-up of pressure during washing or spinning or by a greatly reduced pressure decrease during pumping.

Foam detection can also be carried out by means of a conductivity measurement with two electrodes in the lower region of the tub. In addition, a foam detection during spinning by means of an evaluation of the target / actual speed difference is possible. In the foam detection by evaluation of the target / lst speed difference, the fact is exploited that the foam can brake a rotating drum, whereby there is a difference between the target and the actual speed. In this case, the association between a specific foam concentration and the target / difference is generally stored in a data memory of the drum washing machine.

Upon detection of foam during spinning, spinning is stopped and the process of the invention is carried out.

The invention also relates to a drum washing machine with a program control for controlling a program sequence, a drum rotatably mounted in a tub, a water supply system, a liquor drain system arranged at the bottom of the tub with a drain pump, a drive motor for the drum, a sensor for determining a foam level h _s and / or a negative temporal Gradients (ie, _s / dt) of a liquid-air mixture in the tub, and switching means for rotating, accelerating, decelerating and / or stopping the drum, wherein the switching means can perform the method of the invention described above. The drum washing machine according to the invention preferably also has a heating device.

The method and drum washing machine of the present invention enable rapid and efficient foam removal. Generally, any foam that has been ejected is not applied to the laundry again. When using reduced amounts of water, the invention makes it possible to avoid residual foam on the laundry and the cuff. In this case, the invention makes possible an automatic adaptation of the foam removal measure to the actual formation of foam.

The invention will be described below with reference to the FIG. 1 which is a schematic representation of the relevant parts of a drum washing machine according to the invention, in which a method according to the invention for the removal of foam can be carried out. Other embodiments are conceivable.

The drum washing machine of in FIG. 1 embodiment shown has a tub 1, in which a drum 2 is rotatably mounted and driven by the drive motor 14. For improved ergonomics, the rotational axis 3 of the drum 2 is directed from the horizontal by a small angle (eg 13 °) forwardly upwards, so that the user of the drum washing machine has easier access and insight into the interior of the drum 2. By this arrangement, in conjunction with specially shaped Wäschemitnehmern 4 and 5 Schöpfeinrichtungen for the wash liquor 6 on the inner surface of the drum shell also also an intensification of the washing of the laundry 7 with wash liquor and a reduction of the free liquor reaches which amount of wash liquor in the tub referred to, which can not be absorbed by the saturated laundry (substantially below the lowest point of the drum 2).

The drum washing machine also has a liquor inlet system comprising a water connection fitting for the domestic water network 8, an electrically controllable valve 9 and a supply line 10 to the tub 1, which may optionally also be guided via a Waschmitteleinspüleinrichtung ("Einspülschale") 11, from the Inlet water can transport detergent portions into the tub. In addition, in the tub 1, a heater 13. The valve 9 as well as the heater 13 can be controlled by a control device ("program control") 12 in response to a program flowchart of a time program and / or the achievement of certain measurements of Parameters such as liquor level, liquor temperature, speed of the drum, etc. may be bound within the drum washing machine. 15 means a sensor for measuring the hydrostatic pressure or its negative time gradient in the tub 1.16 means a drain pump for pumping out the wash liquor.

Claims (12)

1. Method of eliminating foam in a drum washing machine with a program control (12) for control of a program sequence, a drum (2) rotatably mounted in a solution container (1), a water feed system (8, 9, 10), a solution drain system, which is arranged at the base of the solution container (1), with a solution pump (16), a drive motor (14) for the drum (2) and a sensor (15) for determining the level h_s of foam and/or a negative time gradient (dh_s/dt) of the foam level of a liquid/air mixture in the solution container (1), characterised in that when foam is recognised by the sensor (15) during spinning run-up of the drum (2), i.e. a continuous or discontinuous increase in the rotational speed of the drum (2), with the solution pump (16) switched on continuously or discontinuously a small quantity of water is added continuously or discontinuously, wherein the level h_s of foam is monitored by means of the sensor (15) during spinning and a rotational speed of the drum (2) is controlled in dependence on the level h_s of foam so that in a case of increase in the level h_s of foam the rotational speed is reduced, in a case of maintenance of the level h_s of foam the rotational speed is maintained and/or in a case of a reduction in the level h_s of foam the rotational speed is increased, and a maximum feed quantity of water is adapted during the spinning run-up to the amount of laundry present in the drum (2).
2. Method according to claim 1, characterised in that in the case of exceeding a maximum level h_smax of foam the rotational speed is reduced to standstill of the drum (2).
3. Method according to claim 2, characterised in that the maximum level h_smax of foam is adapted to the amount of laundry present in the drum (2).
4. Method according to any one of claims 1 to 3, characterised in that the sensor (15) is an optical measuring system.
5. Method according to any one of claims 1 to 3, characterised in that the sensor (15) is a conductometric measuring system.
6. Method according to any one of claims 1 to 3, characterised in that the sensor (15) is a capacitive measuring system.
7. Method according to any one of claims 1 to 3, characterised in that the sensor (15) is a pressure measuring system.
8. Method according to claim 7, characterised in that the pressure measuring system is additionally used for regulating a water state during a washing and/or rinsing process.
9. Method according to any one of claims 1 to 8, characterised in that the continuously fed water quantity is 0.5 to 1.5 l/min.
10. Method according to any one of claims 1 to 8, characterised in that the discontinuously fed water quantity is in each instance 0.2 to 2 l.
11. Method according to any one of claims 1 to 10, characterised in that the following steps A) to F) are carried out:

    A) in the case of standstill or slow rotation of the drum, pumping away of the liquid/air mixture and after a predetermined time Δt₁ measuring the hydrostatic pressure p and/or the negative time gradient (-dp/dt) of the hydrostatic pressure;

    B) comparing the hydrostatic pressure p measured in step A) with a predetermined threshold value p₁ for the hydrostatic pressure p and/or comparing the negative time gradient (-dp/dt), which is measured in step A), of the hydrostatic pressure with a predetermined threshold value (-dp/dt)₁ for the negative time gradient (-dp/dt) of the hydrostatic pressure and

    C) performing the following steps C1) to C3) if the conditions (-dp/dt) < (-dp/dt)₁ and p > p₁ are present:

    C1) adding a predetermined small water quantity ΔV_i;

    C2) rotating the drum at a predetermined low rotational speed U₁;

    C3) pumping away the liquid/air mixture, measuring the hydrostatic pressure p and repeating step B);

    D) performing the following steps D1) to D4) if the condition (-dp/dt) > (-dp/dt)₁ or p < p₁ is present:

    D1) in the case of pressure p greater than a predetermined pressure p₂, wherein p₂ < p < p₁, adding a predetermined small water quantity ΔV_j and rotating the drum at a rotational speed U₂ > U₁ with the pump switched on, wherein after a predetermined time interval Δt₂ the hydrostatic pressure p is measured and depending on a change in the hydrostatic pressure p after expiry of the time interval Δt₂ one of the following steps D2) to D4) is performed:

    D2) in the case of a rise in the hydrostatic pressure p adding a predetermined small water quantity ΔV_j, reducing the rotational speed U₁ by an amount ΔU_i and rotating the drum at the rotational speed U₁ - AU_i;

    D3) in the case of the hydrostatic pressure p remaining the same adding a predetermined small water quantity ΔV_j and rotating the drum at unchanged rotational speed U₁;

    D4) in the case of reduction in the hydrostatic pressure p adding a predetermined small water quantity ΔV_j, increasing the rotational speed U₁ by an amount ΔU_j and

    rotating the drum at the rotational speed U₁ - ΔU_j;

    D5) measuring the hydrostatic pressure p after expiry of a time interval Δt₂ and if p > p₁ and a sum ∑ΔV_i,j of the added water quantities ΔV_i,j is smaller than a predetermined maximum permissible water quantity W_z carrying out one of the steps D2) to D4) in dependence on the change in pressure occurring after the time internal Δt₂;

    E) repeating the steps A) to D5) if ∑ΔV_i,j > W_z; and

    F) in the case of a pressure p < p₂ increasing the rotational speed U of the drum until reaching a predetermined maximum rotational speed U_max.
12. Drum washing machine with a program control (12) for control of a program sequence, a drum (2) rotatably mounted in solution container (1), a water feed system (8, 9, 10), a solution drain system, which is arranged at the base of the solution container (1), with a solution pump (16), a drive motor (14) for the drum (2) and a sensor (15) for determining the level h_s of foam and/or a negative time gradient (dh_s/dt) [of the foam level] of a liquid/air mixture in the solution container (1), as well as switching means (9, 12, 14) for rotating, accelerating, braking and/or stopping the drum, characterised in that the switching means (9, 12, 14) are arranged for eliminating foam in the drum washing machine in that when foam is recognised by the sensor (15) during spinning run-up of the drum (2) with the solution pump (16) switched on continuously or discontinuously a small quantity of water is added continuously or discontinuously, wherein the level h_s of foam is monitored by means of the sensor (15) during spinning and a rotational speed of the drum (2) is controlled in dependence on the level h_s of foam so that in a case of increase in the level h_s of foam the rotational speed is reduced, in a case of maintenance of the level h_s of foam the rotational speed is maintained and/or in a case of a reduction in the level h_s of foam the rotational speed is increased, and a maximum feed quantity of water is adapted during the spinning run-up to the amount of laundry present in the drum (2).

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