EP2895649A1

EP2895649A1 - Method for washing laundry items in a program-controlled domestic appliance, and such a domestic appliance

Info

Publication number: EP2895649A1
Application number: EP13756513.1A
Authority: EP
Inventors: Christine Meissner; Kathrin Redlin
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2012-09-17
Filing date: 2013-09-05
Publication date: 2015-07-22
Anticipated expiration: 2033-09-05
Also published as: CN104704156A; RU2015108919A; RU2615061C2; DE102012023084A1; EP2895649B1; CN104704156B; PL2895649T3; WO2014040905A1

Abstract

The invention relates to a method in which a washing liquid in a suds container (3) is heated and a washing temperature of the washing liquid is set in order to wash laundry items (7) in a program-controlled domestic appliance (1) used for treating laundry items. In said method, laundry-specific and/or appliance-specific parameters, in particular the temperature of the washing liquid (6), are detected and the washing liquid is heated in dependence on the parameters in order to set a specific target temperature. The method is characterized in that, during a wetting phase (A2), in which washing liquid (6) is fed to the suds container (3) in order to wet the laundry items (7), a heating device (16) included in the domestic appliance is activated in order to heat the washing liquid (6), and the washing liquid (6) is heated by means of the heating device (16) to a wetting-phase temperature (Tn) that is lower than the target temperature (Tz) that is associated with a washing method selected by an operator. The method preferably also comprises a hot-water controller which causes the washing liquid to be heated to the target temperature during the wetting phase. The invention further relates to a corresponding domestic appliance.

Description

Method for washing items of laundry in a program-controlled domestic appliance, and such household appliance

The invention relates to a method for washing items of laundry in a program-controlled domestic appliance for the care of laundry items, in particular a washing machine in which a washing liquid present in a tub heated, a washing temperature is adjusted, laundry specific and / or device-specific parameters are detected and dependent on the parameters the heating of the washing liquid is performed to set a specific target temperature. The invention also relates to a program-controlled domestic appliance for washing items of laundry by means of a washing liquid, comprising a suds container for holding the washing liquid, a regulator unit, a temperature sensor for detecting the temperature of the washing liquid, with at least one solenoid valve for opening and closing a water inlet and a heater for heating the washing liquid to a specific target temperature, wherein regulator unit is adapted to carry out such a method.

DE 199 06 723 B4 discloses a method for washing laundry in a program-controlled washing machine and a corresponding program-controlled washing machine. Depending on a selected wash program, a wash temperature is set.

Moreover, DE 31 26 135 C1 discloses a method for adjusting the liquor temperature by means of a temperature measurement in a program-controlled drum washing machine.

Furthermore, DE 10 2007 002184 B4 discloses a method for washing items of laundry in a program-controlled domestic appliance for the care of laundry items, in which a washing liquid present in a suds container is heated and a washing temperature is set, wherein, inter alia, appliance-specific parameters are detected and dependent on the parameter values, the heating of the washing liquid to set a specific washing temperature is performed. A method for controlling the temperature of mixed water fed from separate cold and hot water feeds and an apparatus for implementing the method is known from EP 1 683 904 A1. This method and apparatus are particularly applicable to program-controlled domestic appliances such as washing machines and dishwashers.

The washing of laundry items of a laundry item in a domestic appliance for the care of laundry items, in particular a washing machine, is usually carried out in three phases. In a first phase, a water inlet and a wetting of the introduced in a drum of a washing machine for washing laundry done. In this first phase, also called net phase, the laundry, which is located in the inner drum, with the washing liquid or the liquor, which is located in the tub of the washing machine, wetted. In a second phase, also called washing phase, heating takes place to the respective target temperature of the selected washing program. In this case, a control of a heater is predominantly continuous. Only in certain programs or program modifications is an interruption of heating in this second phase. However, this leads in the majority of cases to a corresponding extension of the total washing time. In a third phase, which is referred to as the post-wash phase after reaching the target temperature, in some cases a temporary overheating takes place via a predefined hysteresis in the temperature control. In other cases, re-heating is ruled out once the target temperature has been reached. The heating of the laundry item in the second phase and the possible reheating in the third phase are each indirectly via the liquor. For this purpose, a heating device or a radiator is usually arranged in the lower part of the tub. The lye is heated by the radiator. When moving the drum, other items of laundry always come into contact with the heated liquor. Through the exchange between the free and the bound fleet, the heating of the laundry takes place.

Since the laundry is not heated directly in a batch of laundry, but indirectly via the wash liquor, depending on the type of textile and the textile amount, a temperature gradient results between the interior of the laundry lot and the free space surrounding it Fleet. This temperature gradient is the greater, the lower the exchange between the free and the bound liquor takes place. At the same time, an increased loading volume, decreasing fall mechanics due to a high filling ratio and a decreasing ratio of free to bound liquor significantly increase this temperature gradient.

This has the consequence that at high loading, the average temperature of the Wäschepostens, the "washing temperature", well below the temperature of the laundry surrounding the liquor, the "liquor temperature" is. With the household short wash times, this may mean that the average laundry temperature remains below certain minimum values, for example below 50 ° C. for sufficient bleach activation, and thus the wash performance is worsened lasting.

A conditional improvement can be achieved in this context by a corresponding extension of the washing time, optionally with a reheating. However, this in turn leads to a user not desired significant extension of the washing time.

Furthermore, an improvement in this regard can be achieved if the heater is already turned on in the mains phase. Such control of the washing temperature causes domestic appliances, which are connected to cold and hot water, the washing liquid is heated by the heater so fast that the target temperature is reached before the washing liquid required for wetting the laundry has been completely supplied to the tub , Thus, the still required amounts of water are supplied via the cold water inlet, which then has to be heated by the heater again. Thus, more heating energy must be expended than would be necessary in a pure hot water control.

It is therefore an object of the present invention to provide a method in which the washing time can be shortened and yet improved cleaning of the laundry items can be achieved, the method used energy-saving both in household appliances with exclusively cold water inlet as domestic appliances with cold and hot water supply can be. Also, a suitably upgraded home appliance should be specified. This object is achieved by a method having the features of claim 1, and a program-controlled domestic appliance, which has the features of claim 1 1, solved.

The inventive method for washing items of laundry in a program-controlled domestic appliance for the care of items of laundry is heated in a washing liquor present in a tub and set a washing temperature of the washing liquid. Here are laundry-specific and / or device-specific parameters, in particular the temperature of the washing liquid, detected and carried out depending on the parameters, the heating of the washing liquid for setting a specific target temperature. The method is characterized in that during a mesh phase in which the tub is supplied for washing the laundry laundry, a household heating device for heating the washing liquid is activated and is heated with the heater, the washing liquid to a net phase temperature which is smaller as the target temperature associated with a washing process selected by an operator.

It is particularly advantageous that the heating device can be activated already in the mains phase, at the same time maintaining a hot water control. This is achieved by using the hot water to regulate the washing liquid to the target temperature and with the heating device only to a lower temperature, the mains phase temperature. Thus, in the case of a refilling of washing liquid during the mains phase, the feed would preferably take place via the hot water feed. Thus, according to heating energy can be saved for the heater. Preferably, the mains phase temperature is set so that the mains phase temperature at the end of the mains phase is not quite reached when operating the household appliance with exclusive cold water supply. Thus, in such an operating case, the network phase is used optimally with regard to the introduction of heating energy in order to achieve even short program runtimes. Thus, advantageously only a single method can be provided which is suitable both for the domestic appliance with cold water inlet and for the domestic appliance with cold and hot water inlet. This procedure is then only in one

Embodied controller unit, whereby device variants can be saved. Thus, the home appliances are also cheaper to manufacture. The domestic appliance is preferably for operation with different target temperatures, which can be selected by the operator depending on the desired wash cycle. Thus, adapted for the process also for the possible target temperatures each adapted network phase temperatures.

Preference is given during the network phase from separate cold and hot water to the tub washing liquid supplied and are varied with a control unit, the cold and hot water supplies depending on the temperature of the washing liquid. In this case, the temperature of the washing liquid is set to the target temperature for which an upper limit and a lower limit are predetermined. Thus, the heating of the laundry items is prioritized by the supply of hot water to the heater of the household appliance. The upper and lower limits represent the limits of a hysteresis for the target temperature and are used to control the hot water and cold water supply. In this case, preferably at a temperature of the washing liquid which is less than or equal to the lower limit value, washing liquid is supplied via the hot water inlet, whereby the supply of washing liquid can be continued via the hot water supply until the temperature of the washing liquid reaches the upper limit value or has exceeded, that is, until a temperature of the washing liquid is greater than equal to the upper limit determined.

Accordingly, it can be advantageously provided that at a temperature of the washing liquid which is greater than or equal to the upper limit, washing liquid is supplied via the cold water inlet, wherein the supply of washing liquid can be continued through the cold water inlet until the temperature of the washing liquid to the lower Limit has reached or fallen below, that is, until a temperature of the washing liquid is determined to be less than or equal to the lower limit. In a washing phase subsequent to the net phase, in which no more heating energy is to be introduced, in the case of a draw, the supply of further washing liquid can take place via the cold water inlet, even if the lower limit value has not been reached. According to an alternative advantageous development, when the upper limit value is exceeded, a hot water feed to a cold water feed and a fall below the lower limit value are switched from a cold water feed to a hot water feed. In order to further simplify the control, such switching preferably does not take place during an active water feed, but only at the subsequent water feed. That is, when the temperature of the washing liquid exceeds the upper limit, a subsequent supply of washing liquid via the cold water inlet, or if the temperature of the washing liquid falls below the lower limit, there is a subsequent supply of washing liquid through the hot water inlet.

In particular, it is provided in the method that the mains phase temperature is less than the lower limit of the target temperature. Furthermore, in the method, the mains phase temperature is preferably dependent on the quantity and / or the type of the items of laundry introduced. This is particularly advantageous because the duration of the mesh phase is dependent on the load and the water absorption capacity of the laundry, since it is only completed when the required for the complete wetting of the laundry items amount of washing liquid and the additional desired free washing liquid supplied to the tub is. However, if the loading amount and / or before the start, for example, from a weighing, or shortly after the first water supply known, the expected total amount of washing liquid and required to reach the target temperature energy can be estimated. Therefore, then for each load quantity or type of loading and an optimum network phase temperature can be set, where possible no extension of the selected wash program takes place in the exclusive cold water mode and as little additional heating energy must be spent on the heater in the mixed cold and hot water operation of the domestic appliance.

The object is also achieved by the program-controlled domestic appliance for washing items of laundry by means of a washing liquid, with a suds container for receiving the washing liquid, a regulator unit, a temperature sensor for detecting the temperature of the washing liquid, with at least one magnetic valve for opening and closing a water inlet and a heating device Heating the scrubbing liquid to a specific target temperature, wherein the control unit is electrically connected to the at least one solenoid valve and the heater is connected, wherein the

Regulator unit is adapted for driving the heating device and is further adapted to activate during a net phase, which is designed for wetting the laundry items by the supply of washing liquid, the heater and to heat with the heater, the washing liquid to a mains phase temperature which is less than a target temperature associated with a washing process selected by an operator.

Such a household appliance can be developed advantageously by comprising at least one separate cold and one hot water inlet and the controller unit is further adapted to drive the solenoid valves of the cold and hot water feeds. In this case, the regulator unit is preferably set up to adjust the temperature of the washing fluid to the target temperature for which an upper limit value and a lower limit value are predetermined during the network phase. This is achieved in that the regulator unit allows opening and closing of the solenoid valves (17, 18) depending on the temperature (T) of the washing liquid (6) by the regulator unit (16).

For the control of a washing program selected by an operator, the domestic appliance preferably has a program control. The controller unit may be included in this program controller or incorporated as a separate unit in the domestic appliance.

Under hot water supply is in the context of the present invention, a supply of water from a home supply network, the water was already heated within the home supply.

The washing temperature, in particular by the regulator unit, thus specifically adapted to the current individual situation of the washing process, thereby enabling an improved washing process. The wash temperature to be controlled and the heating process are adapted to previously recorded condition variables or to the one-part variables of the washing process selected by an operator. As a result, the times for achieving the average washing temperature can be shortened in a targeted manner and thereby also realize shorter washing programs. In addition, better uniformity speed of the washing process can be achieved and an improved washing performance can be made possible even with very different items of laundry and relatively high loads.

Preferably, depending on the detected parameters, the energy input to be provided in particular by the heating of the household appliance for setting a mean washing temperature is determined. Preferably, the required energy input is generated in particular by appropriate control of the heater in at least two different phases, in particular depending on the progress of the selected wash program, with predefined temperature peaks.

As laundry-specific parameters, the loading quantity and / or the absorbency of the laundry items are preferably detected, in particular with suitable, basically known sensor systems assigned to the program control and / or the controller unit. In addition, it can be provided that the target temperature of the selected wash program and / or the average water level in the tub during a heating phase and thus in particular during a previously described second phase of the washing process, and / or the device temperature and / or the device ambient temperature as device-specific parameters and operating parameters be recorded.

Preferred embodiments of the inventive method may also represent preferred embodiments of the inventive domestic appliance and vice versa. The invention will be explained in more detail below using an exemplary embodiment with reference to the drawings. Show it:

1 schematically a washing machine in a sectional view,

2 is a diagram of a program sequence, wherein the rotational speed of the laundry drum and the amount of supplied washing liquid over time are shown schematically,

3 is a diagram of a net phase according to the invention with exclusive cold water feed, wherein schematically the temperature and the amount of supplied washing liquid are shown over time,

Fig. 4 is a diagram of a known network phase in cold and hot water supply, wherein schematically the temperature and the amount of supplied washing liquid over time are shown, and Fig. 5 is a diagram of a net phase according to the invention in cold and hot water supply, wherein schematically the temperature and the amount of supplied washing liquid are shown over time. In a preferred embodiment, a washing machine 1 (Fig. 1) in a housing 2 to a tub 3, in which a laundry drum 4 is rotatably supported by a shaft 5 and driven by a drive unit, not shown. The laundry drum 4 is charged with laundry items 7 via a filling opening (not shown). Hot water is supplied via a hot water inlet 8 and cold water is fed via a cold water inlet 9 to a flushing device I 0, in particular to a washing agent lancing device. This is the output side via a supply line 1 1 connected to the tub 3. The hot and cold water inlet is connected on the input side to a domestic water supply. The temperature of the hot and cold water depends on the ambient conditions of the domestic water supply. Preferably, the warm water has a temperature between 50 ° C and 60 ° C.

In the tub 3, according to one of a temperature sensor 12, which is preferably mounted in the vicinity of the bottom of the tub 3, measured temperature of the washing liquor via the supply line 1 1 warm or cold water via one of the two water inlets 8 or 9 initiated.

For this purpose, the temperature of the washing liquor is obtained as a signal quantity x in a transducer assigned to the temperature sensor 12. Furthermore, the washing machine 1 has a pressure sensor 13 with which a further signal is obtained via a further transducer, which signal is proportional to the height of the washing liquid fed to the tub 3. These signals are fed to a regulator unit 16. For this purpose, the sensors 12 and 13 and their transducers are electrically connected via lines with the

Regulator unit 16 connected. Alternatively, the signals can also be supplied to a program control 15 comprised by the washing machine 1. This is particularly advantageous if the regulator unit 16 and / or the transducers of the sensors 12 and 13 are integrated in the program control 15.

In the control unit 16, a reference variable is formed from the temperature signal x and the pressure signal. The reference variable is the size whose value, ie the setpoint, the Task size under fixed conditions. From the reference variable, the control unit 16 generates signal quantities, due to the solenoid valves 17, 18 are opened or closed to supply from the cold or hot water inlet 8, 9 washing liquid 6 of the desired temperature via the supply line 1 1 to the tub 3. Furthermore, the control unit 16 corresponding to the heater 19 on and off, which only takes place when with the supply of hot water through the hot water inlet 8 a set for the heater 19 temperature, in this case the mains phase temperature Tn is not reached. This is the case when the washing liquid 6 supplied via the hot water connection 8 does not yet have a sufficiently high temperature. This is brought to the required high temperature via the heating device 19 arranged in the bottom region of the tub 3. The heating device 19 is also connected to the program control unit 15 or to the control unit 16 via a signal line. That is, in the case of operation of the washing machine 1 with a cold and hot water supply, the heater 19 is an additional device, with the additional heat energy of the washing liquid 6 can be supplied.

In an alternative embodiment, not shown, the washing machine 1 may also be connected only via a cold water inlet 9 with a domestic water supply. In this case, the control unit 6 exclusively controls the heating device 19, which is why heat energy is then supplied to the washing liquid only by means of the heating device 19. That is, the controller unit 6 can be used both for a washing machine with exclusively cold water inlet as well as for a washing machine 1 with cold and hot water inlet 8, 9.

2 shows an example of a diagram of a program sequence is shown, wherein the speed of the laundry drum 4 (solid line z) and the amount of the tub 3 supplied washing liquid 6 (dashed line y) are shown over time t. A wash program sequence is divided into several phases. In the diagram (FIG. 2), the net phases A1, A2, which are defined by the fact that water is supplied to the tub for wetting the laundry items during these phases, and an adjoining washing phase B are shown. The network phases A1 and A2 differ in that the heater 19 is not activated in the network phase A1 and is activated in the network phase A2. Only if the heating device is activated can this be switched on and off. In the course y of the amount of washing liquid 6 rising and constant sections can be seen. During a rising portion, a water inlet 8 or 9 is opened and washing liquid 6 is supplied to the tub. In the washing phase B, the temperature T of the washing liquid 6 is always brought to the target temperature Tz by means of the heating device 19. The duration of the net phase A1 can be predetermined in time, or be dependent on the supplied washing liquid 6, in order to ensure that the heating device is also covered with washing liquid. In the present exemplary embodiment, the laundry drum 4 is operated in the network phases A1 and A2 with a speed optimized for the network, for example 25 1 / min. This speed is particularly with respect to the laundry drum 4 arranged, and not shown scooping, the washing liquid 6 transported from the bottom of the tub 6 in the upper tub area so that they can rain from there on the laundry items 7. During the washing phase B, in the present case, the laundry drum 4 is driven at a speed which is greater than in the mains phase, for example at 50 l / min. With the higher speed, a larger washing mechanism is introduced into the laundry items 7. FIG. 3 shows a profile of the temperature T (solid line x) and the amount of supplied washing liquid M (dashed line y) over the time t, which in the method according to the invention during a mains phase A1 and A2 during operation of the washing machine 1 with cold water inlet only. During the water inflow phases IV, cold water from the domestic supply network is supplied to the tub 3 via the cold water inlet 9. With the beginning of the mains phase A2, the heater 19 (section V) is turned on by the regulator unit 16, shown with the dotted line. In the inflow of cold water, the temperature T decreases only a little from, while the washing liquid 6 is reheated by the switched-heater 19 during the water inlet. In the present case, the network phase temperature Tn has been selected such that the heating device 19 remains switched on during the entire network phase A2. During a subsequent washing phase B, the temperature T of the washing liquid 6 is further heated to the target temperature Tz between the limits Tz-max and Tz-min. The operation of the washing machine 1, which comprises a cold and hot water connection 8, 9, will be explained below. FIG. 4 shows a profile of the temperature T of the washing liquid 6 (solid line x) and the amount M of supplied washing liquid 6 over the time t for a method known from the prior art during the network phases A1 and A2. In this method, the cold and hot water supplies and as well as the heater are controlled such that both by means of cold and hot water control as well as by means of temperature control, the washing liquid 6 during the network phases A1 and A2 already the target temperature Tz within the limits Tz-max and Tz-min can reach. This means that the heating device can remain switched on until reaching the upper limit Tz-max.

In this known method washing liquid 6 is supplied to the tub above the hot or cold water inlet in section I. The heater remains off since it is not activated in the mains phase A1. After the hot water supply, the temperature drops slightly again, since the washing liquid 6 are also cooled by the colder items of laundry 7 and the components of the washing machine. In the subsequent section II washing liquid 6 is again supplied to the tub over the hot water inlet, since the target temperature Tz has not yet been reached. However, within section II, the network phase A2 begins, in which the heater is activated. Thus, the heater is turned on immediately, since the target temperature Tz has not yet been achieved with the hot water supplies I and II. Before a renewed water supply takes place, the washing liquid 6 is heated to a temperature Tz-max by means of the heating device, for which reason the heating device is switched off. Since the upper limit Tz-max of the target temperature Tz has already been reached, the next water inlet in section IV is made via the cold water inlet, the heater being switched on again as soon as the lower limit Tz-min is reached. Accordingly, it may happen that all subsequent water supplies only via the cold water inlet, since the heater already sufficiently heated the washing liquid to a value above the limit Tz-max.

In contrast, in the embodiment of the inventive method for washing items of laundry 7 shown in FIG. 5 in a washing machine 1 with a cold and hot water supply 8, 9, the heater 19 is only switched on within the mains phase A2 when the washing liquid 6 is at the mains phase temperature Tn. the below the lower limit Tz-min is not yet reached. According to this embodiment, the washing liquid is supplied to the tub 3 via the hot water inlet 8 in sections I and II, wherein during the section II, the heater 19 is switched on only briefly within the section V until reaching the mains phase temperature. Depending on the specific boundary conditions of the respective washing program sequence, it can also happen that during the section II the heating device 19 does not have to be switched on at all. In FIG. 5, the representation forms of the lines and sections have been selected as in FIG. 4. In a section III, which begins after completion of the current water supply, the hot water valve 17 of the hot water inlet 8 is deactivated due to the exceeding of the upper limit Tz-max the target temperature Tz of the washing liquid 6 and accordingly the cold water valve 18 of the cold water inlet 9 has been activated. Thus, the subsequent water supply during section IV on the cold water inlet takes place. This inlet lowers the temperature of the washing liquid 6, but it does not fall below the net phase temperature Tn. Thus, the heater 19 remains switched off during the mains phase A2. With the falling below the lower limit Tz-min of the target temperature Tz, the cold water valve 18 is deactivated again for the next water supply and the hot water valve 17 is activated, which is why the water supply again takes place via the hot water inlet 8 during the last section I shown in Fig. 5.

The direct comparison of Figures 4 and 5 clearly shows that in the inventive method, the heater 19 is turned on only briefly. Thus, compared to the known method significantly additional heating energy can be saved, the same process can be used in washing machines with only one cold water inlet without impairment.

In addition to this exemplary embodiment, further modifications are included, in particular, that the mains phase temperature Tn can also be dependent on the loading amount and the type of the laundry items. In addition, the cold and hot water valves 17, 18 can be switched immediately upon reaching the upper or lower limit Tz-max, Tz-min, so even during a water supply. LIST OF REFERENCE NUMBERS

1 washing machine

2 housings

3 tubs

4 laundry drum

5 wave

6 washing liquid

7 pieces of laundry

8 hot water supply

9 cold water inlet

10 flushing device

1 1 supply line

12 tem peratu s sor

13 pressure sensor

15 program control

16 control unit

17 hot water solenoid valve

18 cold water solenoid valve

19 heating device

A1 mains phase without activated heating device

A2 mains phase with activated heating device

B washing phase

M amount of washing liquid supplied to the tub

T temperature of the washing liquid

n Speed of the laundry drum

t time, duration of a wash program

Tn mains phase temperature for the heater during a mains phase

Tz Target temperature for the washing liquid

Tz-Max upper limit of target temperature Tz

Tz-min lower limit of target temperature Tz I Water supply via hot water supply

II Water supply via hot water inlet and switched on heating device

III phase in which the cold water inlet is activated

IV Water supply via cold water inlet

V phase in which the heating device is switched on x signal and diagram of the measured temperature of the washing liquid

y Diagram of the wash solution supplied to the tub z Signal and diagram of the speed of the laundry drum

Claims

Patent claims

Method for washing items of laundry (7) in a program-controlled household appliance (1) for the care of items of laundry, in which a washing liquid (6) present in a tub (3) is heated, a washing temperature is set, laundry-specific and/or device-specific parameters are recorded and Depending on the parameters, the heating of the washing liquid (6) is carried out to set a specific target temperature (Tz), characterized in that during a wetting phase (A2), in which the tub (3) for wetting the laundry items (7) is supplied with washing liquid (6 ) is supplied, a heating device (19) for heating the washing liquid (6) is activated and with the heating device (16) the washing liquid (6) is heated to a network phase temperature (Tn), which is smaller than the target temperature (Tz), which is assigned to a washing process selected by an operator.

Method according to claim 1, characterized in that during the network phase (A1, A2) washing liquid (6) is supplied to the tub (3) from separate cold and hot water inlets (8, 9) and that the cold water is supplied with a control unit (16). and hot water inlets (8, 9) are varied depending on the temperature (T) of the washing liquid (6), the temperature (T) of the washing liquid (6) being at the target temperature (Tz), for which an upper limit value (Tz-max) and a lower limit value (Tz-min) are predetermined.

Method according to claim 2, characterized in that at a temperature (T) of the washing liquid (6) which is less than or equal to the lower limit value (Tz-min), washing liquid (6) is supplied via the hot water inlet (8).

Method according to claim 2 or 3, characterized in that a supply of washing liquid (6) via the hot water inlet (8) is continued until the temperature (T) of the washing liquid (6) has reached or exceeded the upper limit value (Tz-max). .

5. The method according to one of claims 2 to 4, characterized in that at a temperature (T) of the washing liquid (6) which is greater than or equal to the upper limit value (Tz-max), washing liquid (6) via the cold water inlet (9 ) is supplied.

6. The method according to one of claims 2 to 5, characterized in that a supply of washing liquid (6) via the cold water inlet (9) is continued until the temperature (T) of the washing liquid (6) reaches the lower limit value (Tz-min). or has fallen below.

7. The method according to claim 2 or 3, characterized in that if the temperature (T) of the washing liquid (6) exceeds the upper limit value (Tz-max), a subsequent supply of washing liquid (6) via the cold water inlet (9) he follows.

8. The method according to claim 5 or 6, characterized in that if the temperature (T) of the washing liquid (6) falls below the lower limit value (Tz-min), a subsequent supply of washing liquid (6) via the hot water inlet (8) he follows.

9. The method according to one of claims 2 to 8, characterized in that the network phase temperature is smaller than the lower limit of the target temperature.

10. The method according to one of the preceding claims, characterized in that the network phase temperature (Tn) depends on the amount and / or type of laundry items (7) introduced.

1 1. Program-controlled household appliance (1) for washing items of laundry (7) using a washing liquid (6), with a tub (3) for holding the washing liquid (6), a control unit (16), a temperature sensor (12) for measuring measuring the temperature (T) of the washing liquid (6), with at least one solenoid valve (17, 18) for opening and closing a water inlet (8, 9) and a heating device (19) for heating the washing liquid (6) to a specific target temperature ( Tz), the control unit (16) being electrically connected to the at least one solenoid valve (17, 18) and the heating device (19), characterized in that that the control unit (16) is set up to control the heating device (19) and is also set up to do so during a network phase (A1, A2), which is designed to wet the laundry items (7) by supplying washing liquid (6). Activate the heating device (19) and use the heating device (19) to heat the washing liquid to a network phase temperature (Tn), which is smaller than the target temperature (Tz), which is assigned to a washing method selected by an operator.

12. Domestic appliance according to claim 1 1, characterized in that the control unit (16) is set up to control the solenoid valves (17, 18) of separate cold and hot water inlets (8, 9) and is further set up in such a way that the temperature during the network phase (T) of the washing liquid (6) to the target temperature (Tz), for which an upper limit value (Tz-max) and a lower limit value (Tz-min) are predetermined, for which purpose the solenoid valves (17 , 18) is made possible by the control unit (16) depending on the temperature (T) of the washing liquid (6).