EP2185763A1

EP2185763A1 - Method for eliminating foam in a drum washing machine and drum washing machine suitable therefor

Info

Publication number: EP2185763A1
Application number: EP08774906A
Authority: EP
Inventors: Ingo Schulze; Torsten Hasse
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2007-08-01
Filing date: 2008-07-09
Publication date: 2010-05-19
Anticipated expiration: 2028-07-09
Also published as: WO2009016009A1; US20100199440A1; PL2185763T3; EA201070210A1; CN101772600A; US8510887B2; EP2185763B1; DE102007036041A1; EA017259B1; CN101772600B

Abstract

The invention relates to a method for eliminating foam in a drum washing machine having a program controller (12) for controlling a program sequence, a drum (2) rotatably supported in a detergent solution tub (1), a water supply system (8, 9, 10), a detergent solution discharge system disposed at the bottom of the detergent solution tub having a detergent solution pump (16), a drive motor (14) for the drum (2), and a sensor (15) for determining a foam level hs and/or a negative time gradient of the foam level (dhs/dt) of a fluid/air mixture present in the detergent solution tub (1), wherein a small amount of water is added continuously or discontinuously, with the detergent solution pump (16) switched on continuously or discontinuously, when foam is detected by the sensor (15) during a spinning run-up of the drum (2), that is, a continuous or continuous increase in the rotational speed of the drum (2). The invention further relates to a drum washing machine suitable for performing said method.

Description

Method for removing foam in a drum washing machine and drum washing machine suitable for this purpose

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 DE 41 04 151 A1, the foam is destroyed by switching on a heating device. 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 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 supply line in the tub wall between the tub and the drum.

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

DE 102 34 472 A1 describes a method for removing foam in one

Lye container of an electronically controlled drum washing machine as a result of a program step, which is provided for dewatering of 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) recorded during the operation of the leach pump contains a gradient Δp _n / Δt _n compared to Δp _n -i / Δt _n -i, which indicates the presence of foam, then one on the Gradient-matched foam treatment measure is initiated.

In EP 0 278 239 A1, excessive foam formation in the main wash, which can be observed during the heating of wash liquor in the tub, is eliminated by adding a limited amount of cold water and / or by temporarily switching off the liquor heating.

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 to provide a method by means of 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 14. 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 time gradient of the foam level (dhg / 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 continuous increase in the speed of the drum, with continuously or discontinuously switched on the drain pump, a small amount of water is added continuously or discontinuously.

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.

In a preferred embodiment of the method according to the invention, the foam level h _{s is} monitored by means of the sensor during a spin, and a rotational speed of the drum is controlled as a function of the foam level h _s .

In this case, it is particularly preferred that, when the foam level h _{s is increased,} the rotational speed is reduced, the rotational speed is maintained when the foam level h _{s is} maintained and / or the rotational speed is increased when the foam level h _{s is} reduced.

Preferably, a maximum inflowing amount of water during the spin start-up is adapted to the amount of laundry in the drum. 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. A load detection can be performed, for example, on the accumulated amount of water and in particular by comparing between measured hydrostatic pressure and amount of water.

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

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 out the liquid-air mixture and after a predetermined time At ₁ Measuring the hydrostatic pressure p and / or the negative time 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 predetermined threshold value ( -dp / dt) -ι for the negative temporal gradient of the hydrostatic pressure (-dp / dt), and

C) in the presence of the conditions (-dp / dt) <(-OpZcIt) ₁ and p> pi performing the following steps C1) to C3),

C1) Addition of a given small amount of water ΔV _h

C2) rotating the drum at a predetermined low speed Ui, 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 ^ or p <pi 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 <Pi, adding a predetermined small amount of water .DELTA.V _j and rotating the drum with the pump on at a speed U ₂ > Ui, 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 ΔV _j , reducing the speed Ui by an amount ΔU, and rotating the drum at the speed Ui-ΔU ,;

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 Ui by an amount ΔU _j and rotating the drum at the speed Ui-AU ,;

D5) measuring the hydrostatic pressure p after a time interval Δt ₂ , and in the event that p> pi and a sum Σ ΔV, _{j of} the added amounts of water ΔV, _{j is} less than a predetermined maximum allowable amount of water W _z , performing a 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,,> W _z repeating steps A) through 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 method according to the invention, the predetermined amount of water .DELTA.V, and / or .DELTA.V _j adapted to a loading of the drum with laundry.

In general, the predetermined amount of water ΔV, and / or ΔV _{j is} 0.5 to 2 liters. The amounts of water ΔV, and ΔV _j may be the same or different. Preferably, the amounts of water ΔV, 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), the speed U of the drum is increased at a pressure p <p ₂ until reaching a predetermined maximum speed U _ma χ, which is preferably in the range of 900 to 1100 revolutions per minute. The increase in speed can be gradual or in one or more stages.

The time intervals At ₁ and At 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 drop during pumping.

The foam detection can also be carried out via a conductivity measurement with two electrodes in the lower region of the tub. In addition, a foam detection during spin by means of an evaluation of the target / actual speed difference is possible. In the foam detection by evaluation of the target / actual 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 / actual 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 of a drum rotatably mounted in a tub, a water supply system, a bottom of the tub arranged Laugenablaufsystem 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 is illustrated below with reference to FIG. 1, which is a schematic representation of the parts of a drum washing machine which are relevant to the invention, in which a method according to the invention for removing foam can be carried out. Other embodiments are conceivable.

The drum washing machine of the embodiment shown in Figure 1 comprises 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 (e.g., 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 feed system, which has a

Water connection fitting for the domestic water network 8, an electrically controllable valve 9 and a supply line 10 to the tub 1 includes, which may also have a

Waschmitteleinspüleinrichtung ("Einspülschale") 1 1 may be performed, from which 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, drum speed, etc. can 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

claims

1. A method for removing foam in a drum washing machine with a program control (12) for controlling a program sequence, a in a tub (1) rotatably mounted drum (2), a water supply system (8, 9,

10), a liquor drainage system arranged at the bottom of the tub (1) with a drain pump (16), a drive motor (14) for the drum (2) and a sensor (15) for determining a foam level h _s and / or a negative time gradient the foam level (ie _s / dt) of a liquid-air mixture in the tub (1), characterized in that at

Sensor (15) detected foam during a spin start of the drum (2), i. a continuous or continuous increase in the rotational speed of the drum (2), with continuously or discontinuously turned on drain pump (16) continuously or discontinuously a small amount of water is added.

2. The method according to claim 1, characterized in that in a spin the foam level h _s by means of the sensor (15) is monitored and depending on the foam level h _s a speed of the drum (2) is controlled.

3. The method according to claim 2, characterized in 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 of the foam level h _s, the speed is increased.

4. The method according to any one of claims 1 to 3, characterized in that a maximum inflowing amount of water during the spin start-up is adapted to the amount of laundry in the drum (2).

5. The method according to any one of claims 1 to 4, characterized in that when exceeding a maximum foam level h _smax the speed is reduced to a standstill of the drum (2).

6. The method according to claim 5, characterized in that the maximum foam level h _{smax is adapted} to the amount of laundry in the drum (2).

7. The method according to any one of claims 1 to 6, characterized in that the sensor (15) is an optical measuring system.

8. The method according to any one of claims 1 to 6, characterized in that the 5 sensor (15) is a conductometric measuring system.

9. The method according to any one of claims 1 to 6, characterized in that the sensor (15) is a capacitive measuring system.

10. The method according to any one of claims 1 to 6, characterized in that the sensor (15) is a pressure measuring system.

11. The method according to claim 10, characterized in that the pressure measuring system additionally for the regulation of a water level during a wash and / or

15 rinse is used.

12. The method according to any one of claims 1 to 11, characterized in that the continuously tapered amount of water is 0.5 to 1, 5 I / min.

20 13. The method according to any one of claims 1 to 11, characterized in that the discontinuously tapered amount of water is in each case 0.2 to 2 l.

14. drum washing machine with a program control (12) for controlling a program sequence of a tub (1) rotatably mounted in a tub (2),

25 a water supply system (8, 9, 10), at the bottom of the tub (1) arranged Laugenablaufsystem with a drain pump (16) a drive motor (14) for the drum (2), a sensor (15) for determining a foam level h _s and / or a negative temporal gradient (ie, _s / dt) of a liquid-air mixture in the tub (1), and switching means (9, 12, 14) for rotating,

Acceleration, deceleration and / or stopping of the drum, characterized in that the switching means (9, 12, 14) are arranged to remove foam in the drum washing machine by detecting foam from the sensor (15) during a spin start of the drum (2 ) in continuously or discontinuously switched on drain pump (16) continuously or discontinuously a small

35 amount of water is added