EP2333149B1 - Tumble drier with ambient temperature sensor - Google Patents

Description

Field of the invention

The invention relates to a tumble dryer with a drum for receiving laundry to be dried, with a process air circuit for drying the laundry in the drum and with a controller. Furthermore, the invention relates to a method for operating such a tumble dryer.

background

Out EP 2 006 437 a tumble dryer is known in which the laundry is dried in a drum. Process air is passed through the drum in a process air cycle, wherein a heat pump is provided for drying and heating the process air. Furthermore, the device has a cooling fan to cool a part of the heat pump with ambient air and thus to extract excess heat from the device. The device is designed to cool the cooling fan depending on the temperature of the medium of the heat pump.

EP 512 940 describes a device in which the degree of soiling of the lint filter is determined based on the frequency of temperature control cycles of the system.

DE 199 39 271 describes a method for determining the drying time in a tumble dryer, in which the ambient temperature is taken into account.

Presentation of the invention

It has as its object to provide a device or a method of this kind, which allow a more reliable determination of the degree of contamination of the lint filter. This object is achieved by the tumble dryer or by the method according to the independent claims.

Accordingly, the controller of the device is configured to determine the ambient temperature with a temperature sensor and to control the drying process and / or a display of the device depending on the ambient temperature.

There are various possibilities for this, of which some are mentioned below as well as in the detailed description below. These different options can be used alternatively or in combination.

If the device has a heat pump designed to dry and heat the process air in the process air circuit, then the ambient temperature can be used to differentially control the heat pump. In particular, coolant may be provided to cool at least a portion of the process air cycle and / or the heat pump with ambient air, as shown in FIG EP 2 006 437 or EP 1 156 149 is described. The coolant can now be controlled depending on the ambient temperature, in particular by being operated at higher ambient temperature stronger and / or longer than at cooler ambient temperature.

According to the claim, the knowledge of the ambient temperature is used to more reliably determine the degree of soiling of the lint filter of the device. For this purpose, known methods measure the duration of the drying process, for example the time it takes for the water content in the laundry or in the process air to drop below a certain level, whereby a long process time can indicate a high degree of soiling. However, a long process time may also be due to a high ambient temperature. Other methods determine the number of superheat cycles of the compressor of the heat pump of the appliance as this number increases as the lint filter loses its permeability. Even in this case, however, this can Number also increase because the ambient temperature is high, without the lint filter would be very dirty. Therefore, considering the ambient temperature in both cases allows a better detection of the filter contamination.

If the device has a display to indicate the anticipated process time of the drying process, the knowledge of the ambient temperature can be used to better estimate this process time as the process time usually increases with increasing ambient temperature.

Knowledge of the ambient temperature may also be useful for other applications, e.g. for the calculation of an estimated energy consumption, for the determination of an optimal process temperature or for the determination of the duration of individual process steps.

Short description of the drawing

Further embodiments, advantages and applications of the invention will become apparent from the dependent claims and from the following description with reference to FIG. This shows a block diagram of the most important components of a tumble dryer.

Ways to carry out the invention Structure of the device

The device after Fig. 1 has a drum 1 for receiving the laundry to be dried. It is provided a process air cycle (which in Fig. 1 is shown by solid lines), in which heated process air passed through the drum 1 and a lint filter 12, then cooled and then reheated and fed back into the drum 1. By cooling the process air it is dried in a known manner.

A blower 10 serves to pump over the process air.

Further, a heat pump cycle is provided (the path of the pumped by the heat pump cycle medium in Fig. 1 shown with dotted lines). The medium is conveyed by a compressor 2 to a condenser 3, from there to an additional heat exchanger 4, then via a throttle body 5, for example in the form of capillaries or an expansion valve, to an evaporator 6 and then via an optional heater 9 back to the compressor 2. The evaporator 6 serves to cool the process air and to extract water in this way, while the condenser 3 serves to reheat the process air so that they can absorb new water.

How out Fig. 1 Further, a cooling fan 7 is provided, which serves to cool at least a portion of the heat pump and / or the process circuit with ambient air. Im in Fig. 1 shown embodiment is performed with the cooling fan 7 ambient air over the additional heat exchanger 4 in order to cool this.

The cooling fan 7 and the additional heat exchanger 4 serve to extract heat from the heat pump cycle and thus the entire system and to deliver this to the ambient air. Preferably, the amount of heat extracted is controlled depending on the temperature in the heat pump cycle (and / or depending on the temperature in the process air cycle), eg, by operating the cooling fan 7 at a higher power as the temperature rises. The function and operation of the additional heat exchanger are described in detail in EP 1 884 586 and EP 2 006 437 described, but the control of the cooling fan 7 in the manner described below is additionally dependent on the ambient temperature.

• Ein erster Temperatursensor 20 misst die Umgebungstemperatur Tu des Geräts. Unter "Umgebungstemperatur" wird dabei die Temperatur des Raumes verstanden, in welchem der Wäschetrockner steht, oder ein zumindest an diese Temperatur angenäherter Wert. Funktion und Aufbau des Temperatursensors 20 werden weiter unten genauer beschrieben.
• Ein zweiter Temperatursensor 21 misst die Temperatur des Mediums der Wärmepumpe zwischen Expansionsventil 5 und Verdampfer 6.
• Ein dritter Temperatursensor 22 misst die Temperatur des Mediums der Wärmepumpe zwischen Verdampfer 6 und Kompressor 2.

Furthermore, the device has different temperature sensors, for example:

• A first temperature sensor 20 measures the ambient temperature Tu of the device. Under "ambient temperature" is understood to mean the temperature of the room in which the tumble dryer is, or a value at least approximated to this temperature. Function and structure of the temperature sensor 20 will be described in more detail below.
• A second temperature sensor 21 measures the temperature of the medium of the heat pump between expansion valve 5 and evaporator 6.
• A third temperature sensor 22 measures the temperature of the medium of the heat pump between the evaporator 6 and the compressor 2.

In the present context, only the first temperature sensor 20 is mandatory.

A controller 8 of the device evaluates the signals of the various temperature sensors and any other sensors and controls the device depending on the measured signals and the inputs of the user. For the latter, the device has a control panel 15. Further, the controller 8 may drive a display 16 which may be used by the user e.g. Indicates operating parameters and / or an expected process duration for the drying process.

Use of ambient temperature Tu

The device is preferably substantially with the example in EP 1 884 586 or EP 2 006 437 controlled method described. The knowledge of the ambient temperature Tu, however, allows some improvements, eg with regard to efficiency, reliability and user information. Some examples are described in more detail below.

a) Control of cooling

The cooling fan 7, as mentioned, extracts heat from the system by cooling with ambient air. Its efficiency depends on the ambient temperature Tu. Therefore, the controller 8 preferably controls the cooling fan 7 as a function of the ambient temperature Tu, and in particular operates it at a higher ambient temperature Tu stronger (ie at a higher speed) and / or longer than at a lower ambient temperature Tu. For this example, in paragraph 0031 of EP 1 884 586 shown table can be modified depending on the ambient temperature Tu by the values in the left column of the table are selected lower by 1 or 2 ° C at an ambient temperature above 30 ° C.

A corresponding control can also be used if the cooling fan 7 does not cool the heat pump, but (via an air-to-air heat exchanger) directly the air in the process air circuit.

In the above examples, the cooling means are formed by the cooling fan 7, which blows ambient air against a heat exchanger with which the heat pump medium and / or the process air can be cooled. In a further embodiment, the coolant may also include a controllable opening on the process air circuit, which may be partially or completely opened by the controller 8 to replace process air in the process air circuit by ambient air, as in EP 1 156 149 is described. Also in this way heat can be withdrawn from the system. The opening is preferably controlled depending on the ambient temperature Tu so that at high ambient temperature, a stronger exchange of air takes place than at low ambient temperature.

b) Detection of lint filter contamination

The knowledge ambient temperature Tu will be used according to the invention to more reliably detect contamination of the lint filter 12.

Basically, it is known that increasing contamination of the lint filter results in that, on the one hand, the temperature in the process cycle and in the Heat pump increases, and on the other hand, the process duration, ie the duration increases until reaching a predetermined drying quality. By now at least one of these quantities, ie a temperature parameter, of the. Temperature in the process cycle or in the heat pump depends, and / or the process duration is measured, the degree of contamination of the lint filter can be determined. However, both the mentioned temperature parameter and the process duration increase even when the ambient temperature Tu increases. By also taking into account the ambient temperature in the determination of contamination, more accurate values for the degree of soiling of the lint filter can thus be determined.

• Einer Prozessdauer des Trockenprozesses und/oder eines von der Temperatur im Prozesskreislauf und/oder in der Wärmepumpe des Wäschetrockners abhängigen Temperaturparameters, sowie
• der Umgebungstemperatur Tu.

In other words, the degree of contamination of the lint filter 12 is thus determined depending on the following parameters:

• A process duration of the drying process and / or a temperature parameter dependent on the temperature in the process cycle and / or in the heat pump of the tumble dryer, as well as
• the ambient temperature Tu.

The duration of the process is a suitable parameter in particular if this duration is determined by the moisture remaining in the laundry or the process air. For this, e.g. the drum 1 be equipped with suitable sensors for measuring the electrical conductivity of the laundry.

The above-mentioned temperature parameter is, for example, the temperature at a suitable point in the process air cycle or in the heat pump.

In a further embodiment of a heat pump tumble dryer, the temperature parameter may also be the number of overheating cycles of the heat pump of the appliance during a drying process. For this purpose, the heat pump is provided with a temperature sensor whose signal is compared with a permissible maximum value. If the maximum value is exceeded, the controller 8 switches off the heat pump compressor 2 until the temperature value drops to a permissible threshold value (= overheating cycle). Thereafter, the compressor 2 can be turned on again when needed. The number of such overheating cycles increases with increasing contamination of the filter 12, but also with increasing ambient temperature. Thus, for example, at an ambient temperature Tu of below 25 ° C., an inadmissible contamination of the lint filter 12 can be inferred if at least four overheating cycles are detected during a drying process. At an ambient temperature Tu between 25 ° C and 30 ° C, however, an impermissible contamination is only concluded if at least six overheating cycles take place; at Tu> 30 ° C, at least eight overheating cycles are required.

The result of the determination of lint filter contamination may be e.g. be displayed on the display 16, for example in the form of a request to clean the lint filter 12.

c) Estimation of the duration of the process

The knowledge ambient temperature Tu can also be used to more accurately determine the anticipated process duration, to then determine this, for example. to display on the display 16.

As already mentioned, it is generally known to display the anticipated process duration of a drying process in a tumble dryer. Corresponding methods are known to the person skilled in the art. However, as the process time increases with increasing ambient temperature Tu, more accurate predictions can be made if the ambient temperature Tu is taken into account in determining the process duration. Therefore, the controller 8 is preferably configured to calculate the anticipated process duration depending on the ambient temperature Tu. For this purpose, in the controller 8, for example a table with correction factors must be stored as a function of the ambient temperature Tu, with which the conventionally determined process duration is to be multiplied. The correction factors can be determined, for example, by calibration measurements of the device manufacturer.

d) Other applications

As already mentioned, the knowledge of the ambient temperature Tu can additionally or alternatively also be used for other purposes, e.g. for the calculation of an estimated energy consumption, for the determination of an optimal process temperature or for the determination of the duration of individual process steps.

For example, the ambient temperature Tu may also be used to decide if and how long the device should be heated at the beginning of the drying process, e.g. with the heater 9.

The knowledge of the ambient temperature can also be used to determine the final degree of dryness of the laundry. By "final degree of dryness" of the laundry is meant the degree of dryness (i.e., the limit moisture content) at which the drying process is terminated. Depending on the ambient temperature, the subjective humidity sensation changes, since more or less moisture condenses on the hands when touching the laundry and more or less moisture (for example in the form of sweat) is present. With the same residual moisture, the laundry is therefore perceived differently "dry" depending on the ambient temperature. Therefore, the controller 8 is preferably configured to adjust the final degree of dryness as a function of ambient temperature.

Furthermore, the knowledge of the ambient temperature can also be used to adjust the after-dry duration. Depending on the ambient temperature, the condensation performance of the dryer changes, so that the respective program associated drying time too short or too long. Therefore, the controller 8 is preferably designed such that it adapts the predetermined after-dry duration as a function of the ambient temperature. By "night-time drying" is meant a period of time during which the laundry, although the moisture sensor already detects dry laundry, is dried even further. This discrepancy arises, for example, because of thick laundry items or pillows, which are dry on the outside, but still have moisture inside. The after-dry duration is based on practical experience.

Measurement of ambient temperature

The ambient temperature can be measured with a temperature sensor 20 which is in good thermal contact with the environment of the device, e.g. by being arranged in thermal contact with an outer wall of the tumble dryer.

In another embodiment, the temperature sensor 20 may also be arranged in the intake region of the cooling fan 7, where fresh ambient air is sucked in.

The temperature sensor 20 may also be placed directly on the controller 8, i. on a printed circuit board of the controller 8.

In a further embodiment, the temperature sensor 20 can also be arranged on the process air circuit and / or on the heat pump and be formed, for example, by one of the temperature sensors 21 or 22. In this case, the controller is configured to measure the ambient temperature Tu with the temperature sensor in a rest period of the tumble dryer, ie in the time between two drying processes. Preferably, the time interval from the preceding drying process is so large (in particular several hours) that the tumble dryer is in thermal equilibrium with the environment. However, a measurement is basically also possible at an earlier point in time after a drying process, by estimating the ambient temperature from the current temperature at the temperature sensor and the cooling rate.

In this embodiment, therefore, the ambient temperature can be measured with only one temperature sensor (a) between the drying processes and (b) during a drying process a process temperature in the tumble dryer (for example a temperature in the heat pump or in the process air cycle).

While preferred embodiments of the invention are described in the present application, it is to be understood that the invention is not limited thereto and may be embodied otherwise within the scope of the following claims.

Claims (16)

1. Laundry dryer with a drum (1) for receiving laundry to be dried, with a process air circuit for drying the laundry in the drum (1) and with a controller (8), wherein a fluff filter (12) is arranged in the process air circuit, wherein the controller (8) is adapted to determine a contamination degree of the fluff filter (12), characterized in that the laundry dryer has a temperature sensor (20) for measuring the ambient temperature and the controller (8) is adapted to determine the ambient temperature with the temperature sensor (20) and to control a drying process and/or a display (16) depending on the ambient temperature, and wherein the controller (8) is adapted to determine the contamination degree of the fluff filter (12) depending on the following parameters:

   a process duration of the drying process and/or a temperature parameter depending on the temperature in the process circuit and/or in a heat pump (2, 3, 5, 6) of the laundry dryer, as well as the ambient temperature.
2. Laundry dryer according to claim 1, wherein the laundry dryer further has:

   a heat pump (2, 3, 5, 6), which is adapted to dry and to heat up process air in the process air circuit, and

   cooling means for cooling down at least a part of the process air circuit and/or the heat pump (2, 3, 5, 6) with ambient air,

   wherein the controller (8) is adapted to control the cooling means depending on the ambient temperature and particularly to operate stronger and/or longer in the presence of a higher ambient temperature than in the presence of a cooler ambient temperature.
3. Laundry dryer according to claim 2, wherein the cooling means comprise a cooling fan (7) in order to cool down at least a part of the process air circuit and/or the heat pump (2, 3, 5, 6) with ambient air.
4. Laundry dryer according to claim 3, wherein the temperature sensor (20) is arranged in the intake area of the cooling fan.
5. Laundry dryer according to one of the claims 1 to 3, wherein the temperature sensor (20) is arranged in thermal contact with an outer wall of the laundry dryer.
6. Laundry dryer according to one of the preceding claims, wherein the temperature sensor (20) is arranged in the process air circuit and/or on a heat pump (2, 3, 5, 6) of the laundry dryer and the controller (8) is adapted to measure the ambient temperature in an idle phase of the laundry dryer and a process temperature during the drying process.
7. Laundry dryer according to one of the preceding claims, wherein the temperature parameter is a temperature in the process air circuit and/or in a heat pump (2, 3, 5, 6) of the laundry dryer.
8. Laundry dryer according to one of the preceding claims, wherein the temperature parameter is a number of overheating cycles of a heat pump (2, 3, 5, 6) of the laundry dryer during a drying process.
9. Laundry dryer according to one of the preceding claims, wherein the laundry dryer has a display (16) for displaying an estimated process duration of the drying process and wherein the controller (8) is adapted to calculate the estimated process duration depending on the ambient temperature.
10. Laundry dryer according to one of the preceding claims, wherein the temperature sensor (20) is arranged on the controller (8).
11. Method for operating a laundry dryer according to one of the preceding claims, wherein the ambient temperature of the laundry dryer is measured with the temperature sensor (20).
12. Method according to claim 11, wherein the ambient temperature is measured by measuring the ambient temperature by means of the temperature sensor (20) in an idle time of the laundry dryer
    and wherein a process temperature in the laundry dryer is measured during the drying process by the temperature sensor (20).
13. Method according to claim 12, wherein a temperature of the process air and/or a temperature in a heat pump (2, 3, 5, 6) of the laundry dryer is measured during the drying process.
14. Method according to one of the claims 12 or 13, wherein the ambient temperature is measured with the temperature sensor (20) when the laundry dryer is in thermal balance with its ambient temperature.
15. Method according to one of the claims 11 to 14, wherein a fluff filter (12) is arranged in the process air circuit, wherein a contamination degree of the fluff filter (12) is determined depending on the following parameters:

    a process duration of the drying process and/or a a temperature parameter depending on the temperature in the process circuit and/or in a heat pump (2, 3, 5, 6) of the laundry dryer, as well as

    the ambient temperature.
16. Method according to one of the claims 11 to 15, wherein the controller (8) sets a final drying degree of the laundry and/or a posterior drying duration depending on the ambient temperature.

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