DE102009027933A1 - Method for recognizing foam in tub of drum-type washing machine during main washing phase, involves evaluating temperature curves by continuous determination of gradients of temperature curves over preset time period - Google Patents

Abstract

The method involves heating suds by a heating element under simultaneous movement of suds in a tub of a program-controlled laundry treatment machine using a laundry drum. A temperature signal (10) is measured using a temperature sensor and is recorded for maintaining temperature curves (12, 14). The temperature curves are evaluated by continuous determination of gradients of the temperature curves over a preset time period, which amounts between 1 second and 9 seconds. Foam is recognized from a noise signal incorporated in the temperature curves. An independent claim is also included for a program-controlled laundry treatment machine comprising a control device.

Description

The The invention relates to a method for detecting foam in a with a wash liquor filled tub a program-controlled laundry treatment machine, in particular a Drum washing machine, which in the tub a Heating element and a temperature sensor for determining a temperature the wash liquor, in which method a signal of the temperature sensor during operation of the laundry treating machine is recorded continuously. In addition, the concerns Invention a control device programmed to perform this method for a laundry treatment machine and one with laundry treating machine equipped with such a controller even.

excessive Development of foam occurs during a washing process less common in a modern laundry treatment machine as in a state of the art laundry treating machine Technology from about 20 to 25 years ago. By reducing the laundry mechanics in correspondingly endangered sections of the program and lowering the highest possible washing temperature of 95 ° C to 90 ° C in appropriately endangered programs is in the context of the further development of the laundry treatment machine which is also annoying for a user directly excessive Development of foam has been prevented in some washing processes. In addition, the manufacturers of detergents by adding of foam inhibitors, for their part, measures against excessive Development of foam during some washing processes.

Because but a washing process still uses surfactants in the washing used Wash liquor needed, wash liquor remains even in the presence a foam inhibitor always surface active and reserves thus a certain tendency to foaming. At the meeting of some factors, such as when there is an elevated level Concentration of the detergent in the wash liquor when blowing in from air into the wash liquor due to strong washing mechanics (eg with reduced loading of the laundry treatment machine) or when using a strong foaming detergent even lower quality can make it even stronger today Development of foam come to frothing can lead, with the foamed wash through the Einspülschale from the laundry treatment machine exit.

A Strong development of foam in a washing process is in several ways Regretfully. On the one hand, strong foam hinders the washing mechanics - the Lingerie floats in foam almost without own movement - which results in a deteriorated washing performance. on the other hand Strong foam leads to increased stress the heating elements and too strong local temperature differences in the washing liquor or washing liquid. The reason for this is that a conventional for regulating the temperature the wash liquor used temperature sensor too sluggish reacts as the heat transfer from the foam to the Temperature sensor is much lower than one Liquid to the temperature sensor.

Methods are known for washing laundry in a laundry treating machine in which the detection of foam during the pumping and Spülschleuderns. However, such methods are disadvantageous, since in them the resulting foam is detected only at a late program section. Thus, leakage of excessive foam through the dispenser bowl of the laundry treating machine can not be prevented during the actual washing phase preceding said phases. A method in which the foam is detected during the Abpumpphase by determining a pressure gradient, is from the DE 102 34 472 A1 known. The DE 198 46 248 A1 while describing a method in which the detection of foam during the Spülschleuderns.

There are also known methods in which the detection of foam during the washing phase takes place. Such methods are for example in the DE 41 041 51 A1 , of the DE 198 21 148 A1 and the DE 198 39 896 A1 described. There, the foam is determined in each case by means of optical sensors or a Leitwertmesseinrichtung.

A method for detecting foam is also from the EP 1 731 656 A2 known. In this method, at least two units, each referred to as a "foam sensor", which are arranged in the washing machine are used to detect foam. Each unit contains a two-terminal temperature-dependent resistor as a temperature sensor and an open electrode with another terminal. The presence of foam is determined when a sufficiently low electrical resistance forms between two of these electrodes, it being understood that this resistance is provided by the wash liquor and foam produced therefrom. Thus, when foam forms in the washing machine, it acts as an electrical connection between at least two such open electrodes, and the resistance between these electrodes rapidly decreases. However, the method has the disadvantage that the structure of the foam sensors and the wiring and evaluation of the measurement signals generated by the open electrodes are complicated.

It There is therefore a need for a method for detecting foam in a laundry treating machine, where an effective Recognition of foam is possible by simple means. There is also a need for a suitably programmed control device for a laundry treatment machine as well as at a appropriately equipped laundry treatment machine itself.

• (i) Beheizen der Waschlauge mittels des Heizelements unter gleichzeitigem Bewegen der Waschlauge in dem Laugenbehälter;
• (ii) Messen und Aufzeichnen des Signals der Temperatur, um eine Temperaturkurve zu erhalten und
• (iii) Auswerten der in Schritt (ii) erhaltenen Temperaturkurve, und Erkennen des Schaums aus einem in der Temperaturkurve enthaltenen Rauschsignal.

According to the invention, this object is achieved by a method for detecting foam in a liquor container of a program-controlled laundry treatment machine, in particular a drum washing machine, which has in the tub a heating element and a temperature sensor for determining a temperature of the wash liquor, in which method a signal of Temperature sensor continuously recorded during operation of the laundry treating machine, characterized in that the method comprises the following steps:

• (i) heating the wash liquor by means of the heating element while simultaneously moving the wash liquor in the tub;
• (ii) measuring and recording the signal of the temperature to obtain a temperature curve and
• (iii) evaluating the temperature curve obtained in step (ii) and detecting the foam from a noise signal contained in the temperature curve.

• (i) Beheizen der Waschlauge mittels des Heizelements unter gleichzeitigem Bewegen der Waschlauge in dem Laugenbehälter;
• (ii) Messen und Aufzeichnen des Signals der Temperatur, um eine Temperaturkurve zu erhalten und
• (iii) Auswerten der in Schritt (ii) erhaltenen Temperaturkurve, und Erkennen des Schaums aus einem in der Temperaturkurve enthaltenen Rauschsignal.

According to the invention this object is also achieved by a control device for a program-controlled laundry treatment machine, in particular a drum washing machine, which has a tub and in the tub a heating element and a temperature sensor for determining a temperature of the wash liquor, which controls programmed to carry out a method for detecting foam in the liquor container filled with a wash liquor, in which process a signal of the temperature sensor is continuously recorded during the operation of the laundry treating machine and which process comprises the following steps:

• (i) heating the wash liquor by means of the heating element while simultaneously moving the wash liquor in the tub;
• (ii) measuring and recording the signal of the temperature to obtain a temperature curve and
• (iii) evaluating the temperature curve obtained in step (ii) and detecting the foam from a noise signal contained in the temperature curve.

• (i) Beheizen der Waschlauge mittels des Heizelements unter gleichzeitigem Bewegen der Waschlauge in dem Laugenbehälter;
• (ii) Messen und Aufzeichnen des Signals der Temperatur, um eine Temperaturkurve zu erhalten und
• (iii) Auswerten der in Schritt (ii) erhaltenen Temperaturkurve, und Erkennen des Schaums aus einem in der Temperaturkurve enthaltenen Rauschsignal.

According to the invention this object is further achieved by a program-controlled laundry treatment machine, in particular drum washing machine, which has a tub and in the tub a heating element and a temperature sensor for determining a temperature of the wash liquor and a control device, which control device is programmed to carry out a method for detecting foam in the liquor container filled with a wash liquor, in which process a signal of the temperature sensor is continuously recorded during the operation of the laundry treating machine and which process comprises the following steps:

• (i) heating the wash liquor by means of the heating element while simultaneously moving the wash liquor in the tub;
• (ii) measuring and recording the signal of the temperature to obtain a temperature curve and
• (iii) evaluating the temperature curve obtained in step (ii) and detecting the foam from a noise signal contained in the temperature curve.

In Accordingly, heating takes place in a first step (i) of the method the wash liquor by means of the heating element with simultaneous movement.

In a second step (ii) is the temperature profile with a temperature sensor in the tub preferably throughout Washing phase of the laundry measured continuously and with a suitable device recorded. This z. For example, all 100 ms to 2 s, preferably every 1.5 s, a measuring point of the temperature recorded. Indicates the measured and recorded temperature curve a substantially linear temperature increase or increase, so you can conclude that in the tub no or very little foam is present. Indicates the measured and recorded temperature curve, however, a rather zigzag or jagged course, so is the presence of foam indicating noise signal before, and thus has a foaming in the Lye container have taken place.

The Evaluation of the temperature curve obtained in step (ii) takes place in a second step (iii). It is based on the course the temperature curve obtained in step (ii) determines whether foam has formed or not, depending on the result of a Foam treatment measure can be initiated.

After filling the laundry, the detergent and the water in the tub of the laundry treatment machine, the wash liquor is heated and moved at the same time, said moving is preferably carried out by means of a washing drum rotating in the tub, which laundry drum is permeable to the wash and receives the laundry. When rotating the Wä Drum the individual pieces of laundry are taken in a lower portion of the laundry drum and transported upwards, eventually falling from a certain height to the other pieces. In this way, the laundry items are moved and processed, which contributes to the cleaning effect in addition to the effect of the detergent.

At the Heating while moving shows the temperature in the wash liquor the cases without foaming an approximately with a linear, even temperature profile a measurable increase (gradient) at any given time, which contributes to the Heat capacity of the tub and its filling and the heating power is proportional. While the temperature curve in the absence of foam thus follows a roughly linear temperature profile, the temperature curve shows in the presence of foam on a more jagged course, accordingly a uniform without the foam expected Course superimposed noise. This noise has a Frequency spectrum in particular between 0.01 Hz and 1 Hz and is thus distinct from the expectable without foam uniform Course. The reason for this noise is that in the presence of a sufficient amount of foam in an environment of the temperature sensor again and again foam bubbles find that affect the dissipation of heat from heating element. The foam bubbles may be due to the embedded Air acts as a thermal insulation and thus increased locally Heating up the suds cause they can too by shielding the heating element, a local temperature decrease cause. Another role may be due to the stored Air reduced heat capacity of the foam play. Significant influences may additionally also different thermal conductivity of water or wash liquor and foam or air and different heat transfer from the foam or from the wash to the temperature sensor. Regardless of which effects altogether contribute exactly The invention is based on the finding that foam in the wash liquor to a divergence in the distribution of Temperature within the wash liquor, which leads to a measurement and evaluation for presence or absence the foam in the tub accessible and to Avoid excessive foam is.

The Invention thus offers the advantage that it compared to known Method by a simple determination of the noise signal from the measured and recorded temperature signal a particularly simple and accurate, early detection of foam in particular during the main wash phase and therefore early action to avoid or eliminate excessive Foam allows.

By excessive recognition of early recognition Foam can cause the escape of foam through the dispenser tray reliably prevented. In addition, according to the invention a improved washing performance can be achieved by sacrificing be reduced by the foam.

Preferably the evaluation of the temperature curve in step (iii) takes place Evaluate in particular by a correspondingly programmed control device the laundry treating machine is done in such a way that continuously a gradient of the temperature curve over each a predetermined time interval takes place. In the presence said Noise signal, the temperature gradient no longer follows the uniform Temperature curve that results when heated without foam, but changed clearly and with a comparatively high frequency. Thus, can a short-term increased or decreased temperature gradient be used as an indication of the present foam, where appropriate Measures to treat the overly existing foam can be initiated.

The predetermined time interval for the determination of the temperature gradient has a defined and unchangeable length, and it slides over the period in which the procedure is carried out over the temperature curve. The Steps (ii) and (iii) are thus over a predetermined Period, preferably during the washing phase, repeated continuously or both steps run simultaneously. Becomes thereby a certain Temperature rise (threshold) significantly exceeded or below, this is an indication that excessive Foaming has taken place. It can follow to find such a hint measures to Treatment of foam initiated to the excessive Reduce foam. Remains the temperature gradient within of a certain standard, no action is taken.

bestimmt, worin T_n die im Laugenbehälter gemessene Laugentemperatur (z. B. in °C) zum Zeitpunkt t_n (z. B. in s), T_n+1 die im Laugenbehälter gemessene Laugentemperatur (z. B. in °C) zum Zeitpunkt t_n+1 (z. B. in s), (T_n+1 – T_n) die Temperaturdifferenz (z. B. in °C) sowie (t_n+1 – t_n) das vorgegebene Zeitintervall (z. B. in s), über das der Temperaturgradient bestimmt wird, und n eine ganze Zahl ≥ 0 sind.Starting from the temperature curve obtained in step (ii), the temperature gradient is preferably according to the following formula

where T _{n is} the liquor temperature measured in the tub (eg in ° C) at time t _n (eg in s), T _{n + 1 is} the liquor temperature measured in the tub (eg in ° C) at time t _{n + 1} (eg in s), (T _{n + 1} - T _n ) the temperature difference (eg in ° C) as well as (t _{n + 1} - t _n ) the predetermined time interval (z B. in s), via which the temperature gradient is determined, and n are an integer ≥ 0.

The predetermined time interval (t _{n + 1} - t _n ), which slides over a certain period of time in which the method is carried out, is preferably in the range between 1 second and 9 seconds, particularly preferably about 3 seconds.

in the Framework of a preferred embodiment of the invention Procedure becomes a measure following step (iii) for treating the detected foam. is initiated. This is particularly preferred when the temperature gradient is more than a predetermined threshold. Thereby will ensure that a measure only then is initiated if excessive Foaming has taken place.

Of the Threshold is preferably between 0.1 ° C / s and 1.0 ° C / s, more preferably at about 0.3 ° C / s. If this threshold is exceeded, has an excessive foam development in the laundry treating machine, against which a measure must be taken. in principle here, the larger the temperature gradient, the greater the foam development and vice versa. If the temperature gradient is below this threshold, z. More colorful 0.3 ° C / s, so does not have excessive Foam development in the tub took place, and no action needs to be taken. In this way may cost the operation of the laundry treatment machine be lowered.

The Setting the threshold is appropriate independent from the sign of the measured gradient. It can also be both one positive as well as a negative threshold, for example, from the above preferred range, wherein a measure is then initiated when the threshold is exceeded or fallen below accordingly. It can therefore also a subsequent to a brief increase in temperature Temperature drop can be detected.

In a laundry treatment machine, as stated above a washing drum rotating in the tub has, in the context of a preferred embodiment of Invention, the measure as a change in a speed the laundry drum. It has also been shown that contrary to a common belief that the movement of Laundry drum basically the cause of the formation of foam, certain movements of the laundry drum, a special speed profile or the reversing of the laundry drum while applying a removal action of foam in terms of effective removal are advantageous. Advantageously, additionally or alternatively the measure in a reduction or shutdown of Heating energy for a certain period exist.

According to one Another preferred embodiment of the invention, the measure in the pumping out of a subset of the liquor with subsequent Feeding a certain amount of cold and / or warm Water exist. Such a measure is in itself already known, but has in connection with the above features the invention a special quality.

In a particularly preferred embodiment of the invention the process takes place during a washing phase, in particular the main washing phase of the laundry treating machine. Especially Preferably, the process is carried out during a heating phase, So while the wash in the tub is heated.

The The invention also relates to a control device for a program-controlled laundry treatment machine, in particular Drum washing machine that is programmed to carry it out the method according to the invention is suitable, and a laundry treatment machine with an inventive Control device. In one embodiment of this laundry treatment machine the heating element and the temperature sensor are relatively close to each other arranged. In this embodiment, the gap between Heating element and temperature sensor filled with foam, It may be due to the low heat capacity of the Foam to a particularly pronounced short-term increase in temperature.

Based the embodiments shown in the accompanying drawings The invention will now be explained in more detail. Show it:

1 a graph showing a recorded in step (i) temperature signal, which is obtained in the absence of foam in the tub, and

2 a graph showing a recorded in step (i) temperature signal, which is obtained in the presence of foam in the tub.

The chart of the 1 shows the temperature profile (temperature signal) 10 for a 60 ° C wash program measured and recorded in the tub of a washing machine throughout the washing process, including the main wash phase. The other curves contained in the graph 12 and fourteen Make the lye container supplied amount of water 12 dar as well as the rotation and the speed of the drum fourteen during the washing process. The treated linen is textiles made from terry cloth. At the beginning of the washing process (time T0) water is allowed to run for a period of 2 to 3 minutes in the tub of the washing machine. About 1 minute after the start of the water supply, the reversing of the laundry drum also starts at a speed of 30 to 40 rpm, with the laundry drum being reversed by alternating among the possible directions of rotation. After about 10 minutes of reversing the drum, the heating of the wash liquor starts with continued movement of the laundry drum. In the present case, the heating of the wash liquor over a period of about 25 minutes to a liquor temperature in the range of 50 to 60 ° C. As can be seen from the recorded temperature signal, this has a substantially linear temperature rise from an initial temperature of about 16 ° C to a temperature of 54 ° C. This substantially linear temperature profile is an indication that in the present wash no appreciable formation of foam has occurred and therefore no measure for removing foam was necessary.

The graph of 2 shows the temperature profile (temperature signal) 20 for a 60 ° C washing program that is in the tub of a washing machine during another washing process, which is largely the same as in 1 illustrated washing process, but in which an excessive formation of foam was deliberately caused. The others, in the diagram of the 2 contained curves 22 and 24 Make the amount of water added to the tub 22 as well as the rotation and the speed of the drum 24 during the washing process. The laundry is artificial fiber textiles. At the beginning of the washing process (time T0) water is allowed to run for a period of 2 to 3 minutes in the tub of the washing machine. About 1 minute after the beginning of the water supply, the reversing of the laundry drum also starts at a speed of 30 to 40 rpm, the reversing of the laundry drum taking place uniformly with alternating directions of rotation. After about 10 minutes of reversing the drum starts to heat the wash. In the present case, the heating of the wash liquor over a period of about 25 minutes to a liquor temperature in the range of 50 to 60 ° C. As can be seen from the recorded temperature signal, this has a substantially jagged temperature rise from an initial temperature of about 16 ° C to a temperature of 56 ° C. This substantially jagged temperature profile, which differs from the linear temperature curve in 1 differs, arises by superimposing a smoke signal over the uniform course according to 1 , This is clearly an indication that in the present wash a significant formation of foam has occurred. The cause of the noise signal is, in particular, that in the case of (strong) formation of foam around the heating element and / or the temperature sensor, foam bubbles repeatedly form, which have a lower thermal conductivity compared with the wash liquor. This leads to short-term temperature fluctuations in the area of the temperature sensor, which form the noise signal and were measured and recorded. They serve as an indication of the presence of foam and are evaluated by a correspondingly programmed control device of the laundry treatment machine, whereupon appropriate measures for removing the foam are initiated. In the present case, the measure consists in that the heating element is switched off until the wash solution cools to a temperature in the range from 40 to 45 ° C. and the foam thereby volatilises.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10234472 A1 [0005]
• - DE 19846248 A1 [0005]
• - DE 4104151 A1 [0006]
• DE 19821148 A1 [0006]
• - DE 19839896 A1 [0006]
• - EP 1731656 A2 [0007]

Claims (15)

A method for detecting foam in a liquor container of a program-controlled laundry treatment machine, in particular a drum washing machine, which has in the tub a heating element and a temperature sensor for determining a temperature of the wash liquor, in which process a signal of the temperature sensor during operation of the laundry treating machine continuously characterized in that the method comprises the steps of: (i) heating the wash liquor by means of the heating element while simultaneously moving the wash liquor in the tub; (ii) measuring and recording the temperature signal to obtain a temperature curve, and (iii) evaluating the temperature curve obtained in step (ii), and detecting the foam from a noise signal contained in the temperature curve. Method according to claim 1, characterized in that in that the washing liquor is moved by means of a in the tub rotating laundry drum takes place. Method according to one of the preceding claims, characterized characterized in that the evaluation of the temperature curve in step (ii) by continuously determining a gradient of the temperature curve over a predetermined time interval takes place from the temperature curve. A method according to claim 3, characterized in that the gradient according to the following formula

wherein T _{n is} the temperature measured in the tub at a time t _n , T _{n + 1 is} the liquor temperature measured in the tub at a time t _{n + 1} and (T _{n + 1} - T _n ) are a difference in the liquor temperatures, and where (t _{n + 1} -t _n ) is the predetermined time interval over which the temperature gradient is determined and n is an integer greater than or equal to zero. Method according to one of claims 3 and 4, characterized in that the predetermined time interval (t _{n + 1} - t _n ) is between 1 second and 9 seconds. A method according to claim 5, characterized in that the predetermined time interval (t _{n + 1} - t _n ) is about 3 seconds. Method according to one of the preceding claims, characterized characterized in that subsequent to step (iii) a measure for treating the detected foam is initiated. Method according to claim 7, characterized in that the action is initiated when the temperature gradient is more than a predetermined threshold. Method according to claim 8, characterized in that that the threshold is between 0.1 ° C / s and 1.0 ° C / s is. Method according to claim 9, characterized in that that the threshold is about 0.3 ° C / s. Method according to one of claims 7 to 10, characterized in that the moving of the wash liquor by means a washing drum rotating in the tub is done, and that the action is in a change a speed arranged in the tub, rotatable Laundry drum exists. Method according to one of claims 7 to 10, characterized in that the measure in pumping a Subset of the wash liquor with subsequent feed a certain amount of cold and / or warm water. Method according to one of the preceding claims, characterized in that it during a washing phase performed in the laundry treatment machine becomes. Control device for a program-controlled Laundry treating machine, in particular a drum washing machine, which a tub and in the tub a heating element and a temperature sensor for determining a temperature the wash liquor, which controls programmed to Carrying out a method for detecting foam in the liquor container filled with a wash liquor, in which method a signal of the temperature sensor during the operation of the laundry treatment machine continuously is recorded and what procedure the following steps includes: (i) heating the wash liquor by means of the heating element while simultaneously moving the wash liquor in the tub; (Ii) Measure and record the signal of temperature, around a temperature curve to get and (iii) evaluating the results obtained in step (ii) Temperature curve, and detecting the foam from one in the temperature curve contained noise signal. Program-controlled laundry treatment machine, in particular drum washing machine, which a tub and in the Laugenbe container has a heating element and a temperature sensor for determining a temperature of the wash liquor and a control device, which control device is programmed to carry out a method for detecting foam in the liquor container filled with a wash liquor, in which process a signal of the temperature sensor during operation of the laundry treatment machine continuously and which method comprises the following steps: (i) heating the wash liquor by means of the heating element while simultaneously moving the wash liquor in the tub; (ii) measuring and recording the temperature signal to obtain a temperature curve, and (iii) evaluating the temperature curve obtained in step (ii), and detecting the foam from a noise signal contained in the temperature curve.

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