CN107385769B

CN107385769B - Method for detecting bubbles in washing machine

Info

Publication number: CN107385769B
Application number: CN201710197503.6A
Authority: CN
Inventors: 马蒂诺·邦迪
Original assignee: Electrolux Appliances AB
Current assignee: Electrolux Appliances AB
Priority date: 2016-04-21
Filing date: 2017-03-29
Publication date: 2021-06-29
Anticipated expiration: 2037-03-29
Also published as: CN107385769A; EP3235939B1; EP3235939A1

Abstract

The invention relates to a method for operating a washing machine (1, 200) having a washing tub (3) containing a washing drum (4) and a heating device (20) for heating liquid in the washing tub (3). The method comprises the following steps: introducing a quantity of water and a quantity of detergent into the washing tub (3) to form a washing liquid; heating the washing solution; determining a temperature rise rate (TS); the determined temperature rise rate (TS) is compared to a Threshold Value (TV), and it is determined that foam is present if the determined temperature rise rate (TS) is greater than the Threshold Value (TV).

Description

Method for detecting bubbles in washing machine

Technical Field

The invention relates to the technical field of laundry.

In particular, the present invention relates to a method for detecting suds in a washing machine during a wash cycle.

Furthermore, the invention relates to a corresponding washing machine.

Background

Nowadays, washing machines, including both "simple" washing machines (i.e. washing machines that can only wash and rinse laundry) and washer-dryers (i.e. washing machines that can also dry laundry), are widely used.

In this specification, the term "washing machine" will refer to both simple washing machines and washer-dryers.

Washing machines typically comprise an outer casing or cabinet provided with a washing tub containing a rotatable perforated washing drum containing laundry. The loading/unloading door ensures access to the washing drum.

Washing machines generally comprise a water inlet circuit and a product supply unit for introducing water and washing/rinsing products (i.e. detergent, softener, etc.) into the washing tub.

The known laundry washing machines are also provided with a drainage system for draining the washing liquid from the washing tub. The drainage system generally comprises at least one drainage pump arranged at the bottom of the washing tub, which operates when required during the washing cycle.

Generally, the drainage system drains the washing liquid from the washing machine and/or it recirculates the washing liquid inside the tub, so that it is conveyed again onto the laundry.

According to the known art, a complete washing cycle generally comprises different phases or steps during which the laundry being washed is subjected to a suitable treatment.

The washing cycle generally comprises an initial wetting phase in which an appropriate amount of water and detergent is introduced into the washing tub, wherein said water and detergent produce washing liquid for wetting the laundry.

The washing cycle then generally comprises a main washing phase, during which the washing drum is rotated and the washing liquid contained in the washing drum is heated, generally by means of an electric resistor, to a predetermined temperature according to a washing program selected by the user.

The subsequent steps of the washing cycle may include a rinsing stage where clean water is introduced and a draining step, and a final dehydration process in which the washing drum is rotated at a high speed and liquid in the washing tub is drained from the washing machine.

When the washing liquid is moved/agitated by the rotating washing drum, some suds is usually generated. In particular, during the spinning and draining phases of the washing cycle, a large amount of foam can be very disadvantageous, since it can impair the correct functioning of the drain pump and it can hinder the liquid discharge from the machine. Thus, the drain pump is noisy in the presence of foam.

Foam is typically generated in the wash cycle by the user due to excessive use of detergent or by the detergent itself as a foaming agent that promotes foam formation.

In addition, excessive foam may cause spills, including liquid spills.

Some existing methods for operating washing machines are known, for example the method disclosed in WO2015036166, to be able to effectively detect foam and, if necessary, take action to reduce the amount of foam inside the washing tub and/or in the draining area. The detection and reduction of foam is performed in the equilibration phase and/or the dehydration phase, i.e. after the main wash phase.

However, during the wetting phase and/or the main wash phase, a certain amount of foam may have been generated. If too much suds is generated at this early stage of the washing cycle, some stages of the washing cycle cannot be performed without error.

In particular, for the same reasons as described above, a large amount of foam can be very disadvantageous during the dewatering and draining phases of the washing cycle, in particular in terms of the operation of the pump.

Furthermore, a large amount of foam during the main wash stage itself can be very disadvantageous, since the washing efficiency of the wash liquor is significantly reduced compared to normal conditions without foam.

Suds can also lead to detergent accumulation on the laundry. The presence of a certain amount of residual detergent may result in insufficient rinsing. Insufficient rinsing can result in leaving sufficient detergent in the laundry to cause allergies and allergic reactions in humans.

A known method for detecting suds in a washing machine is known from EP 1731656 a 2. In this document, a foam sensor integrated with a temperature sensor is realized. However, the device known from this document is complex.

This adversely affects the size and/or manufacturing cost of the washing machine and its reliability.

It is therefore an object of the present invention to overcome the disadvantages of the prior art.

A primary object of the present invention is to provide a washing machine capable of detecting the presence of bubbles at an early stage of a washing cycle as required.

Another primary object of the present invention is to provide a washing machine capable of reducing residue of detergent on laundry.

Another object of the present invention is to provide a laundry washing machine capable of detecting the presence of bubbles as required and having reduced complexity and/or reduced dimensions compared to known types of laundry washing machines.

A further object of the present invention is to provide a laundry washing machine capable of detecting the presence of bubbles as required and having a higher reliability compared to known types of laundry washing machines.

Disclosure of Invention

The applicant has found that by determining the rate of temperature rise of the liquid in the washing tub of the washing machine, the presence of foam in the washing tub can be determined.

The present invention therefore relates to a method for operating a washing machine during a washing cycle, the washing machine comprising a washing tub accommodating a washing drum and a heating device for heating liquid in the washing tub, wherein the method comprises the steps of:

-introducing a quantity of water and a quantity of detergent into the washing tub to form a washing liquid;

-heating the washing liquid;

-detecting the temperature of the washing liquid in the washing tub and/or in the discharge area of the washing tub;

-determining a rate of temperature rise;

-comparing the determined rate of temperature rise with a threshold value, and determining that foam is present if the determined rate of temperature rise is greater than the threshold value.

Preferably, the temperature of the washing liquid is detected during a predetermined monitoring period.

Preferably, the predetermined monitoring period is between 20s and 30min, more preferably 1 min.

According to a preferred embodiment of the invention, a predetermined monitoring period is set in the heating step.

In a preferred embodiment of the invention, the predetermined monitoring period is set at the beginning of the heating step.

Preferably, the rate of temperature rise is determined during a predetermined monitoring period.

More preferably, the temperature increase rate is an average temperature increase rate in a predetermined monitoring period.

In a preferred embodiment of the invention, the threshold value is comprised between 0.1 ℃/min and 10 ℃/min, preferably between 4 ℃/min and 8 ℃/min, more preferably equal to 7 ℃/min.

According to a preferred embodiment of the invention, the threshold value is related to the type of heating device.

Preferably, the threshold value is related to the power dissipation of the heating means.

In a preferred embodiment of the invention, the heating step is performed after the wetting step of the washing cycle.

The wetting step preferably comprises introducing a quantity of water and a quantity of detergent into the washing tub.

According to a preferred embodiment of the invention, the threshold value is a function of said amount of water.

Preferably, the threshold value is proportional to said amount of water.

According to another preferred embodiment of the invention, the threshold value is a function of the amount of water and the power dissipation of the heating means.

In a preferred embodiment of the invention, the washing drum is rotated during the heating step.

Preferably, the washing drum is rotated during the wetting step.

According to a preferred embodiment of the invention, at least one foam reducing action is taken if it has been determined that foam is present.

In a preferred embodiment of the invention, the foam reducing action comprises one of the following actions:

-reducing the time of the main wash step relative to the expected time of the main wash step of the wash cycle;

-reducing the activation time of the heating means with respect to the expected activation time of the heating means of the main washing step of the selected cycle;

-deactivating the heating means;

-deactivating the heating means for a predetermined time;

-varying the rhythm of the washing drum, preferably reducing the rotation time of the washing drum with respect to the expected rotation time of the main washing step of the selected cycle;

-introducing one or more additional rinsing steps with respect to the intended rinsing step of the selected cycle;

-introducing further water during the main washing step.

In another preferred embodiment of the present invention, the bubble reducing action includes a draining step of removing the washing liquid from the bottom of the washing tub and draining it to the outside. Preferably, clean water is introduced into the washing tub to restore a sufficient amount of washing liquid after the draining step.

According to a preferred embodiment of the invention, the foam reducing action comprises sending a warning alert, preferably a visual alert or an audible alert, to the user.

In a preferred embodiment of the invention, the laundry washing machine comprises a recirculation circuit with a recirculation pump for draining the liquid from the bottom of the washing tub to let said liquid enter another part of the washing tub, wherein the foam-reducing action comprises the following steps: the activation time of the recirculation pump is reduced relative to the expected activation time of the selected cycle.

In another aspect of the invention, the invention relates to a washing machine, wherein the washing machine is provided for the above method.

Drawings

Further features and advantages of the present invention will be emphasized in more detail in the detailed description of preferred embodiments of the invention provided below with reference to the accompanying drawings. In the drawings, corresponding features and/or components are denoted by the same reference numerals. In these drawings:

figure 1 shows a perspective view of a laundry washing machine according to a preferred embodiment of the present invention;

figure 2 shows a schematic front section view of a laundry washing machine according to a preferred embodiment of the present invention;

figure 3 shows a set of schematic graphs as a function of time during a period of time of a washing cycle in a first situation according to a preferred embodiment of the present invention;

figure 3A shows an enlarged view of a detail of figure 3;

figure 4 shows a set of schematic graphs as a function of time during a period of time in a washing cycle in a second situation according to a preferred embodiment of the present invention;

figure 4A shows an enlarged view of a detail of figure 4;

figure 5 shows a schematic flow diagram of a method for operating a laundry washing machine during a washing cycle, according to a preferred embodiment of the present invention;

fig. 6 shows another preferred embodiment of fig. 2.

Detailed Description

As described below, the present invention has proved to be particularly advantageous when applied to a washing machine. It should be stressed in any way that the invention is not limited to washing machines. On the contrary, the present invention can be conveniently applied to a washer-dryer (i.e., a washing machine that can also dry laundry).

Therefore, in the present specification, the term "laundry machine" will refer to both a simple laundry machine and a laundry washing and drying machine.

Referring to fig. 1 and 2, a washing machine 1 according to a preferred embodiment of the present invention is described.

The laundry washing machine 1 comprises an external casing or cabinet 2, in which external casing or cabinet 2 there is provided a washing tub 3 housing a perforated washing drum 4, in which washing drum 4 the laundry to be treated can be loaded.

The cabinet 2 is provided with a front loading/unloading door 8, the front loading/unloading door 8 allowing access to the washing tub 3 and the washing drum 4.

The washing tub 3 is preferably suspended in a floating manner inside the cabinet 2, advantageously by means of a plurality of helical springs and shock absorbers, not shown herein.

Advantageously, the washing drum 4 is rotated by an invisible electric motor, wherein preferably the electric motor transmits the rotational movement to the shaft of the washing drum 4, advantageously by means of a not shown belt-pulley system. In a different embodiment of the invention, the motor may be directly associated with the shaft of the washing drum 4.

A water inlet circuit 5 and a product supply unit 6 are arranged in the upper part of the laundry washing machine 1, the water inlet circuit 5 and the product supply unit 6 being adapted to supply water and washing/rinsing products (i.e. detergent, softener, etc.) into the washing tub 3. The water inlet circuit 5 controls the introduction of water from an external supply line E (hereinafter referred to as a tap water supply E).

The product supply unit 6 preferably comprises a drawer 6 provided with a removable compartment with various compartments adapted to be filled with washing and/or rinsing products.

In the embodiment described herein, water is supplied into the washing tub 3 by flowing it through the drawer 6 and through the supply pipe 9.

In a preferred embodiment, the water reaching the washing tub 3 can optionally contain one of the products contained in the compartment of the drawer 6, or it can be clean and, in this case, it can reach the washing tub 3 directly, bypassing the compartment of the drawer 6.

In an alternative embodiment of the present invention, another separate water supply pipe may be provided, which exclusively supplies clean water into the washing tub 3.

The water inlet circuit 5 also preferably comprises a water flow sensor, for example a flow meter, which enables the quantity of water supplied into the washing tub 3 to be calculated.

Advantageously, the laundry washing machine 1 comprises a drainage system 15.

Advantageously, the draining system 15 comprises a draining pump 16, a first pipe 17 connecting the washing tub 3 to the draining pump 16 and an outlet pipe 18 ending outside the cabinet 2. The draining system 15 is suitable for draining liquids, for example dirty water or water mixed with washing and/or rinsing products, from the washing tub 3 to the outside.

Preferably, the draining system 15 comprises a filtering device (not shown in the figures) located between the bottom of the washing tub 3 and the draining pump 16 and adapted to block all undesired objects (for example buttons that have detached from the laundry, coins that are mistaken into the washing machine, etc.) that have passed through the holes located on the surface of the washing drum 4 or that fall on the bottom of the washing tub 3 when transferred between the washing drum 4 and the washing tub 3, which could damage or block the draining pump 16.

Preferably, the filtering device can be removed through a door 14, advantageously located on the front or rear wall of the cabinet 2 of the laundry washing machine 1, and then cleaned, for example; in another embodiment, not shown, the filtering means can be accessed, for example, via the inside of the washing drum 4, for example through a suitable opening provided in the washing drum 4 selectively closed by a suitable lid, or through a removable lifter (lifter) of the washing drum 4.

Advantageously, laundry washing machine 1 comprises a device 19 suitable for sensing (or detecting) the water level inside washing tub 3.

The device 19 preferably comprises a pressure sensor sensing the pressure in the washing tub 3, the pressure value being correlated to the free water level contained in the washing tub 3. In another embodiment, not shown, laundry washing machine 1 comprises (in addition to or instead of the pressure sensor) a level sensor (for example mechanical, electromechanical, optical, etc.) adapted to sense (or detect) the water level inside washing tub 3.

Advantageously, laundry washing machine 1 comprises heating means 20 adapted to come into contact with the liquid in washing tub 3 and to heat the liquid in washing tub 3.

The heating device 20, preferably an electric resistor, is preferably arranged in a suitable seat, not shown, located at the bottom of the washing tub 3 or in the discharge area of the washing tub 3.

Preferably, the laundry washing machine 1 comprises a temperature sensor 21 for sensing the temperature of the liquid in the washing tub 3.

In the preferred embodiment shown here, the temperature sensors 21 are preferably integrated with the heating device 20, i.e. they are supported by a common housing.

In different embodiments, the temperature sensor may be located in other suitable positions adapted to detect the temperature of the liquid in the washing tub 3.

The laundry washing machine 1 advantageously comprises a control unit 22 connected to the various parts of the laundry washing machine 1 to ensure its operation. The control unit 22 is preferably connected to the water intake circuit 5, to the water discharge system 15, to the electric motor, and the control circuit 22 receives information from various sensors provided on the laundry washing machine 1, such as a flow meter of the water intake circuit 5, a pressure sensor 19 (or level sensor) located at the bottom of the washing tub 3, a temperature sensor 21, etc.

In particular, the temperature detected by the temperature sensor 21 is preferably continuously received by the control unit 22 and is advantageously used according to the invention, as better described hereinafter.

Alternatively, the temperature detected by the temperature sensor 21 is acquired by the control unit 22 at a predetermined time, when necessary.

The laundry washing machine 1 advantageously comprises an interface unit 50 accessible to the user, connected to the control unit 22, and through which the user can select and set washing parameters, in particular desired washing programs, from time to time. The washing program selected by the user will correspond to the respective washing cycle performed by the washing machine. In general, the user may optionally add other parameters, such as washing temperature, dehydration speed, load in terms of weight of laundry, etc. The interface unit 50 preferably includes a display to display the operating status of the machine or other information.

Based on the parameters acquired by said interface unit 50, the control unit 22 sets and controls the various parts of the laundry washing machine 1 in order to perform a desired washing cycle.

The temperature sensor 21 is arranged for detecting the temperature of the liquid in the washing tub 3 or in the discharge area of the washing tub 3.

According to an advantageous aspect of the present invention, the temperature sensor 21 is used to determine whether foam and/or the amount of foam is present in the washing tub 3 and/or the discharge area of the washing tub 3 during the heating phase of the washing cycle.

During heating of the liquid in the washing tub 3, preferably by activating the heating device 20, the temperature WT of the washing liquid in the washing tub 3 or in the discharge area of the washing tub 3 is detected with the temperature sensor 21. Then, a rising speed TS of the washing liquid temperature WT is determined, preferably by the control unit 22, according to the detected value.

Advantageously, if the temperature rise rate TS is greater than the threshold value TV, it is determined that there is foam and/or a large amount of foam in the washing tub 3 and/or in the discharge area of the washing tub 3.

If the temperature rise rate TS is lower than or equal to the threshold value TV, the presence of only water or a small amount of foam is detected.

Preferably, if the temperature rise rate TS is greater than the threshold value TV during the predetermined monitoring period Δ t, it is determined that there is foam and/or a large amount of foam in the washing tub 3 and/or in the discharge area of the washing tub 3.

If the temperature rise rate TS is lower than or equal to the threshold value TV within the monitoring period Δ t, only water or a small amount of foam is detected.

In particular, the determination may be made in the following cases: if the average temperature rise rate ATS is greater than the threshold value TV within the monitoring period Δ t, that is, if:

ATS＝ΔT/Δt>TV

or

Where ti is a start time of the monitoring period Δ t of the washing temperature WT and tf is an end time of the monitoring period Δ t of the washing temperature WT.

According to another advantageous aspect of the present invention, if the presence of foam in the washing tub 3 has been detected, one or more foam-reducing actions, which will be better described below, are preferably performed.

Fig. 3 shows a set of schematic diagrams as a function of time during a period of time in a washing cycle in a first situation according to a preferred embodiment of the present invention.

The first situation corresponds to a correct functioning condition of the washing cycle, i.e. no formation of foam in the washing tub 3.

Fig. 3 shows the time period between t 0s and t 4500s of the wash cycle. This time period corresponds to the initial phase of the wash cycle, in particular the wetting phase (t0-t1) and the main wash phase (t1-t 4).

During the wetting phase, i.e. at t0 ═ 0s to

In between, a quantity of water Qw and a quantity of detergent Qd are preferably introduced into the washing tub 3 through the water inlet circuit 5 and the product supply unit 6. During the wetting phase, water and detergent are introduced into the washing tub 3 to form a washing tub for washing the laundryThe washing liquid of (2).

During the wetting phase, the washing drum 4 is advantageously made to rotate in a preferred rhythm, for example in a clockwise and/or counterclockwise direction, at a low speed (for example at a speed of 10-300 rpm) and advantageously with a stop interval between successive rotations.

Accordingly, the liquid level 44 in the washing tub 3, preferably detected by the pressure sensor 19, rises from 0mm to about 100 mm.

In fig. 3, the liquid level 44 oscillates around 100mm due to the oscillation of the liquid level 44 inside the washing tub 3 caused by the rotation of the washing drum.

A liquid level 44 of about 100mm in the washing tub 3 is preferably sufficient to completely cover the heating device 20, so that the heating device 20 is advantageously completely immersed in the liquid.

The washing liquid temperature WT which is also indicated by reference numeral 45 in figure 3 remains substantially constant during the wetting phase,

corresponding to the temperature of the water coming from the mains water supply E.

As a first condition shown in fig. 3, the correct functioning of the washing cycle, the formation of foam is substantially prevented during the wetting phase.

At the time of

At this point, the main wash phase begins. The main washing stage includes a heating stage (t1-t2) and a holding stage (t2-t 4). During the heating phase, as is perceptible in fig. 3 from the drive signal 47 of the heating device 20, the heating device 20 is activated and the washing drum 4 rotates in a preferred rhythm. During the holding phase (t2-t4), the heating device 20 is deactivated and the washing drum 4 is rotated in a preferred rhythm.

During the heating phase (t1-t2), the washing liquid temperature WT rises essentially linearly. Heating stage in time

At the end of the process, at which time washing is carried outThe liquid temperature WT reaches a predetermined temperature T2. In the preferred embodiment shown here, the predetermined temperature T2 is set to 40 ℃, which corresponds to, for example, a cotton cycle (cotton cycle) of 40 ℃ selected by the user.

During the heating phase (t1-t2), the washing liquid temperature WT is likewise monitored.

In particular, during the heating phase (t1-t2), the temperature rise rate TS is calculated.

The temperature rise rate TS is compared with a threshold value TV, and if the temperature rise rate TS is greater than the threshold value TV, it is determined that there is foam and/or a large amount of foam in the washing tub 3. Otherwise, it is judged that only water or a small amount of foam is present.

Specifically, the temperature increase rate TS is calculated in a predetermined monitoring period Δ t.

In the normal case of fig. 3, the presence of only water or a small amount of foam is detected during the predetermined monitoring period Δ t-t 1-t 3. The temperature increase speed TS calculated in the monitoring period Δ t is eventually lower than or equal to the threshold value TV.

Preferably, the monitoring of the washing liquid temperature WT and the calculation of the temperature rise rate TS are performed continuously in successive monitoring cycles within the heating phase.

More preferably, the monitoring of the washing liquid temperature WT and the calculation of the rate of temperature increase TS are performed immediately at the beginning of the heating phase, i.e. at time t 1.

In different embodiments, the one or more monitoring periods may be distributed in different ways in the heating phase (t1-t2), for example one 2 minute monitoring period every 2 minutes.

Preferably, the temperature rise rate TS is calculated as an average temperature rise rate ATS in the monitoring period Δ t, that is: referring to fig. 3A, ATS is (T3-T1)/(T3-T1) ═ T3-T1)/Δ T, where T3 is the temperature detected at time T3 and T1 is the temperature detected at time T1.

In different embodiments, the temperature increase rate TS may be calculated in different ways, for example continuously (instantaneous rate).

The monitoring period Δ t is preferably set to a predetermined value, for example, 1 minute (min).

Preferably, the predetermined monitoring period is between 20s (seconds) and 30min (minutes).

In another embodiment, the monitoring period Δ t may be automatically reduced if, for example, the drive signal 47 of the heating device 20 is deactivated before the end of the monitoring period Δ t. The above-mentioned deactivation of the drive signal 47 of the heating device 20 before the end of the monitoring period Δ t may occur, for example, in the following cases: the washing liquid temperature WT reaches a predetermined target value, for example 40 ℃ in the cotton cycle at 40 ℃ or a maximum safety value.

The threshold value TV of the temperature rise rate TS is preferably set to a predetermined value, for example to a fixed value of 7 ℃/min.

Preferably, the threshold is between 0.1 ℃/min and 10 ℃/min, more preferably between 4 ℃/min and 8 ℃/min.

However, in different embodiments, the threshold TV may be set differently.

In practice, the warming-up speed TS is influenced by the quantity of water Qw introduced into the washing tub 3 during the wetting phase and/or by the type of heating device used in the laundry washing machine. Therefore, the threshold value TV may preferably be related to the amount of water Qw introduced into the washing tub 3 and/or the type of heating device.

Preferably, the threshold value TV can be estimated from the amount of water Qw introduced into the washing tub 3 during the wetting phase:

TV＝f(Qw)

preferably, the threshold value TV is proportional to the water quantity Qw.

In another preferred embodiment, the threshold value TV may be set according to the specific amount of water Qw introduced into the washing tub 3 during the wetting phase. The following table exemplarily shows the correlation between the threshold value TV and the water quantity Qw, wherein the power dissipation of the resistor 20 is a known value and is equal to 1000 watts:

water quantity Qw (liter)	Threshold value TV (DEG C/s)
		10	3
14	2
		20	2

TABLE 1

The threshold value TV may also preferably be related to the type of heating device used in the washing machine.

More preferably, the threshold value TV may be related to the power dissipation of the resistor 20. The following table exemplarily shows the correlation between the threshold value TV and the power dissipation of the resistor 20, wherein the amount of water Qw introduced into the washing tub 3 during the wetting phase is a known value and is equal to 10 liters:

TABLE 2

In another preferred embodiment, the threshold value TV is preferably related to both the quantity of water Qw introduced into the washing tub 3 and the type of heating device.

The following table exemplarily shows the correlation between the threshold value TV, the amount of water Qw introduced into the washing tub 3 during the wetting phase, and the power dissipation of the resistor 20:

TABLE 3

As mentioned above, the situation shown in fig. 3 corresponds to a correct functioning condition of the washing cycle, i.e. substantially no foam is formed in the washing tub 3. The washing cycle after the main washing stage (t1-t4) is typically continued for the remaining stages of the cycle, i.e., the rinsing stage, the balancing stage, the dehydrating stage, etc. (not shown in fig. 3). Therefore, the washing cycle does not perform the bubble reducing action.

Fig. 4 shows a second situation according to a preferred embodiment of the present invention.

The second situation corresponds to an undesired operating state of the washing cycle, i.e. the formation of foam in the washing tub 3 during the wetting phase.

Fig. 4 shows the time period between t 0s and t 4500s of the wash cycle. This time period corresponds to the initial phase of the wash cycle, in particular the wetting phase (t0-t1) and the main wash phase (t1-t 4).

During the wetting phase, i.e. at t ═ 0s to

In between, a quantity Qw of water and a quantity Qd of detergent are preferably introduced into the washing tub 3 through the water inlet circuit 5 and the product supply unit 6. During the wetting phase, water and detergent are introduced into the washing tub 3 to form washing liquid for washing the laundry.

In fig. 4, the liquid level 44 oscillates around 100mm due to the oscillation of the liquid level 44 inside the washing tub 3 caused by the rotation of the washing tub.

A liquid level 44 of about 100mm in the washing tub 3 is preferably sufficient to completely cover the heating device 20, so that the heating device 20 is advantageously always immersed in the liquid.

The temperature WT of the washing liquid is in the wet stateIs kept substantially constant during the phase in which,

The second situation shown in fig. 4 shows an undesired operating state of the washing cycle, because a certain amount of foam is generated during the wetting phase.

In particular, bubbles are formed in the washing tub 3 due to the rotation of the washing drum 4 during the wetting phase, wherein the washing drum 4 moves/agitates the washing liquid introduced into the washing tub 3.

At the time of

At this point, the main wash phase is started. The main wash stage includes an initial heating stage. During this heating phase, the heating means 20 are suitably activated/deactivated according to a specific control method, as is perceptible from the drive signal 47 of the heating means 20 in fig. 4. The washing drum 4 is likewise rotated in a preferred rhythm.

Since there is foam in the washing tub 3, the washing liquid temperature WT rises rapidly from the initial time t1 of the heating stage.

According to an advantageous aspect of the invention, a rapid rise of the washing liquid temperature WT in the heating phase indicates the presence of foam in the washing tub 3.

As mentioned above, the washing liquid temperature WT is advantageously monitored during the heating phase.

In particular, the temperature rise rate TS is calculated in the heating phase.

In the present case, as shown in fig. 4, since the calculated temperature increase rate TS is actually greater than the threshold value TV, the presence of foam and/or a large amount of foam in the washing tub 3 is detected.

Preferably, the calculation of the rate of temperature increase TS is performed immediately at the beginning of the heating phase, i.e. at time t1, whereby the presence of foam and/or a large amount of foam in the washing tub 3 is detected substantially immediately.

As shown in fig. 4A, the presence of foam is detected during a predetermined monitoring period Δ t-t 1-t 3. More specifically, the temperature increase rate TS is calculated as an average temperature increase rate ATS in the monitoring period Δ T, i.e., ATS ═ (T3-T1)/(T3-T1) ═ T3-T1)/Δ T.

Advantageously, the presence of foam in the washing tub 3 is detected according to the above-described method and one or more foam-reducing actions are performed.

In the following, possible foam reducing actions that may preferably be performed are described.

The foam reducing action that may be performed after detecting foam in the washing tub 3 preferably includes: the time of the main wash phase is reduced relative to the expected time of the main wash phase in the wash cycle.

The main wash phase may be defined as the following phases in the wash cycle: during this phase, the washing drum is rotated, and the washing liquid contained in the washing drum is heated to and/or maintained at a predetermined temperature according to the washing program selected by the user. The main wash phase precedes successive steps of the wash cycle, such as the rinse phase, the equilibrate phase, the spin-down phase, etc.

As the time of the main washing phase is reduced, the rotation time of the washing drum 4 is also reduced, thereby avoiding excessive movement/agitation of the liquid in the washing tub 3. Thus, the foam dissolves more quickly.

Another suds reducing action which may be performed after the detection of suds in the washing tub 3 preferably comprises reducing the activation time of the heating means with respect to the expected activation time of the heating means of the main washing phase of the selected cycle. In this case, the heating means may be completely deactivated for the remaining time of the main wash phase. Again, the foam dissolved more quickly.

Another suds reducing action which may be performed after detecting suds in the washing tub 3 preferably comprises varying the rhythm of the washing drum, preferably reducing the rotation time of the washing drum, with respect to the expected rotation time of the main washing phase of the selected cycle.

The reduction of the rotation time of the washing drum avoids excessive movement/agitation of the liquid in the washing tub, and therefore the foam dissolves more quickly.

Another suds reducing action which may be performed after the detection of suds in the washing tub 3 preferably comprises the introduction of one or more additional rinsing phases with respect to the intended rinsing phase of the selected cycle.

The additional rinsing stage enhances the dissolution of the foam and its discharge to the outside.

Another foam reducing action which may be performed after detecting foam in the washing tub 3 preferably comprises introducing an additional amount of water during the main washing phase.

The introduction of additional water reduces the concentration of detergent in the washing tub 3, thus advantageously reducing the possibility of foam generation.

Another foam reducing action which may be performed after detecting foam in the washing tub 3 preferably comprises a draining phase of the washing liquid being removed from the bottom of the washing tub and drained to the outside.

The discharge of the washing liquid reduces the concentration of the detergent in the washing tub 3, thus advantageously reducing the possibility of foam generation.

In a preferred embodiment, one or more water introduction stages and/or one or more water drainage stages are performed.

In a preferred embodiment, a certain amount of clean water is introduced into the washing tub 3 after the draining phase to restore a sufficient amount of washing liquid for the main wash. The introduction of clean water further reduces the concentration of the detergent in the washing tub 3.

Another action that may be performed after detecting the bubbles in the washing tub 3 preferably includes: a warning alert is sent to the user, such as a visual alert or an audible alert at the display of the interface unit 50. Since the formation of suds may be caused by an excess of detergent or a wrong use of detergent, a suds alert may be useful for the user, as it can inform the user how to prevent suds formation in future laundry washing cycles, e.g. selecting the correct detergent.

Fig. 5 shows a schematic flow diagram of a simplified method for operating a washing machine and for detecting suds during a wash cycle, according to a preferred embodiment of the present invention.

Laundry to be washed is first put into the washing drum 4 (step 100).

The user selects a desired washing course by operating the interface unit 50 (step 110).

In the next step (step 120), a washing cycle according to a washing program selected by the user is initiated. As a next step (step 130), the method provides a wetting phase in which a quantity Qw of water and a quantity Qd of detergent are introduced into the washing tub 3, preferably through the water inlet circuit 5 and the product supply unit 6, to form a washing liquid for washing the laundry. During this wetting phase, the washing drum 4 advantageously rotates in a preferred rhythm.

At a predetermined time t1, the heating phase is started (step 140), preferably by activating the heating device 20.

Starting from time t1 and with a duration Δ t of 1min, the washing liquid temperature WT in the washing tub 3 is preferably monitored by means of the temperature sensor 21.

At the end of the monitoring period Δ t, the temperature rise rate TS, or preferably the average temperature rise rate ATS, is calculated (step 150). If the ramp rate TS has a value lower than or equal to the threshold value TV ("NO" output at step 160), the method continues with the main wash phase (step 170), typically in steps according to the selected wash cycle.

For example, the heating device 20 is kept activated for more than 10 minutes (step 172) and the washing drum 4 is rotated in a preferred rhythm (step 174).

The main wash phase (step 170) lasts for a predetermined period of time, for example 60 minutes.

The washing cycle then advantageously performs one or more rinsing cycles (steps 180 and 190) during which clean rinsing water is added to the laundry and the washing drum is rotated to extract water and dirty particles/detergent from the laundry: the extracted dirty water is discharged from the washing tub 3 to the outside.

The wash cycle ends with the final dehydration stage (step 200).

Once the washing cycle has ended, in the case of a washer-dryer, it is also preferable to carry out a drying phase.

Returning to step 160, if the temperature increasing speed TS or the average temperature increasing speed ATS has a value greater than the threshold value TV ("yes" output of step 160), the main washing stage is modified by the preferred bubble reducing action.

For example, the heating device 20 is deactivated and the washing drum 4 is not rotated any more (step 176) for a predetermined time, for example 10 min.

Then, advantageously, the method continues with two successive rinsing cycles (steps 177 and 178), wherein clean rinsing water is added to the laundry and liquid is drained from the washing tub 3 to the outside during the rinsing cycles.

The wash cycle then advantageously continues with the one or more rinse cycles (steps 180 and 190) and the final spin phase (step 200).

Fig. 6 shows a constructional variant of a washing machine 200, in which the method according to the invention is advantageously carried out in the washing machine 200.

Features and/or components corresponding to those of the washing machine 1 of fig. 2 are denoted by the same reference numerals.

Washing machine 200 comprises a water outlet circuit 215 provided with a recirculation circuit 216, which recirculation circuit 216 is adapted to drain liquids from the bottom of washing tub 3 and to re-enter these liquids into another portion of washing tub 3, preferably into the upper region of washing tub 3. The recirculation loop 216 includes a recirculation pump 217 and a recirculation pipe 61. The recirculation pipe 61 terminates at a terminal nozzle 61a in an upper region of the washing tub 3.

The drain pump 16 and the recirculation pump 217 are preferably arranged downstream of the common filter 218.

The drain pump 16 and the recirculation pump 217 are suitably controlled by the control unit 22 so as to enable an outward discharge through the outlet duct 18 and/or a discharge through the recirculation pipe 61 towards the washing tub 3.

The operation of the laundry machine 200 and the detection of suds are advantageously performed as described above for the first embodiment.

The previously described suds reducing action can also be advantageously performed in the washing machine 200.

Another suds reducing action which may be performed after detecting suds in the washing tub 3 in the laundry washing machine 200 preferably comprises changing/reducing the activation time of the recirculation pump 217 with respect to the expected activation time of the selected cycle. This enhances a more rapid dissolution of the foam.

Advantageously, the method according to the invention enables the detection of foam at an early stage of the washing cycle, preferably just at the end of the wetting phase.

Accordingly, the bubble reducing action can be performed from the very beginning of the washing cycle. This helps to reduce the build-up of detergent on the laundry relative to known methods.

Furthermore, the detection of the foam is advantageously carried out by means of a temperature sensor, usually installed in the washing machine, without the need to install and control a dedicated foam sensor.

The method of the invention thus enables the detection of suds in a laundry washing machine having reduced complexity and/or dimensions compared to known types of laundry washing machines that detect suds.

Therefore, the washing machine performing the method of the present invention has a higher reliability than the known type of washing machine detecting bubbles.

Still advantageously, the method according to the invention ensures a more correct operation of the pump installed in the laundry washing machine for draining the liquid from the washing tub, since it substantially avoids the presence of foam at the inlet of the pump. This in turn reduces the noise caused by the pump working with the foam.

Advantageously, the method according to the invention reduces or avoids spillage and spillage of liquid from the washing tub.

It has thus been shown that the invention allows to achieve all the set objects. In particular, the invention enables providing a washing machine and a method having a suds detection system that is more efficient than known systems.

It is emphasized that the washing machine shown in the figures and described as a reference for some embodiments of the method according to the invention is of the front-loading type; it is however clear that the method according to the invention can also be applied to a top-loading washing machine substantially without any modifications.

Although in the illustrative embodiment of the present invention the method is applied with the heating phase following the wetting phase, which is approximately at the beginning of the wash cycle, it is to be understood that the present invention is not limited to those precise embodiments and that the method may be applied to any heating phase within the wash cycle.

Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included within the scope of the present invention as defined by the appended claims.

Claims

1. A method for operating a washing machine (1; 200) during a washing cycle, the washing machine comprising a washing tub (3) housing a washing drum (4) and a heating device (20) for heating liquid in the washing tub (3), wherein the method comprises the steps of:

-a wetting step comprising introducing a quantity (Qw) of water and a quantity (Qd) of detergent into the washing tub (3) to form a washing liquid;

-a heating step comprising heating the washing liquid;

-detecting a washing liquid temperature (WT) in the washing tub (3) and/or in a discharge area of the washing tub (3);

-determining a temperature rise rate (TS);

-comparing the determined temperature rise rate (TS) with a Threshold Value (TV) and determining that foam is present if the determined temperature rise rate (TS) is greater than the Threshold Value (TV),

wherein the heating step is performed after the wetting step of the washing cycle, the Threshold Value (TV) being a function (f (Qw)) of the amount of water (Qw).

2. Method according to claim 1, wherein the washing liquid temperature (WT) is detected at a predetermined monitoring period (Δ t).

3. Method according to claim 2, wherein the predetermined monitoring period (Δ t) is between 20s and 30 min.

4. Method according to claim 2, wherein the predetermined monitoring period (Δ t) is 1 min.

5. Method according to any one of claims 2 to 4, wherein said predetermined monitoring period (Δ t) is set within said heating step.

6. A method according to any one of claims 2 to 4, wherein the ramp rate (TS) is determined in the predetermined monitoring period (Δ t).

7. Method according to any one of claims 1 to 4, wherein said Threshold Value (TV) is comprised between 0.1 and 10 ℃/min.

8. Method according to any one of claims 1 to 4, wherein said Threshold Value (TV) is comprised between 4 and 8 ℃/min.

9. Method according to any one of claims 1 to 4, wherein said Threshold Value (TV) is equal to 7 ℃/min.

10. A method according to any one of claims 1 to 4, wherein the washing drum (4) is rotated during the heating step.

11. A method according to any one of claims 1 to 4, wherein the washing drum (4) is rotated during the wetting step.

12. The method of any of claims 1-4, wherein at least one foam reducing action is taken if foam has been determined to be present.

13. The method of claim 12, wherein the foam reducing action comprises one of:

-reducing the activation time of the heating device (20) with respect to the expected activation time of the heating device (20) of the main washing step of the selected cycle;

-deactivating the heating device (20);

-deactivating the heating means (20) for a predetermined time;

-varying the washing drum rhythm, reducing the rotation time of said washing drum with respect to the expected rotation time of the main washing step of the selected cycle;

-introducing further water during the main washing step.

14. Method according to claim 12, wherein the laundry washing machine (200) comprises a recirculation circuit (216) with a recirculation pump (217), said recirculation pump (217) being used to drain the liquid from the bottom of the washing tub (3) and to re-enter it into another part of the washing tub (3), wherein said suds reducing action comprises the steps of: reducing the activation time of the recirculation pump (217) relative to an expected activation time of the selected cycle.

15. A washing machine (1; 200), wherein the washing machine (1; 200) is adapted to employ a method according to any one of claims 1 to 14.