EP3608469B1 - Laundry dryer and method for drying laundry with a laundry dryer - Google Patents

Description

Field of application and state of the art

The invention relates to a tumble dryer and a method for drying laundry to be dried using a tumble dryer.

Various designs for tumble dryers are known, with a tumble dryer quite commonly having a drum including a drive, air supply and air discharge. A fan is also provided to blow heated air into the tumble dryer via the air supply. Air discharged from the drum at the air outlet is then dehumidified in different ways. To dry laundry, the same amount of heat or equally warm air is often always introduced into the drum. A moisture measurement takes place either in the drum or in the air discharged from the drum. If a certain desired degree of drying is recognized, it is defined that the end of the drying process has been reached and the dryer stops.

Various dryers, also with inductive heating, are from the DE 10 2016 110 871 A1 , the EP 262 018 A2 , the EP 240 052 A1 , the DE 10 2016 110 883 A1 , the DE 10 2009 026 646 A1 and the DE 10 2016 110 859 A1 known.

From the EP 3 067 459 A1 a tumble dryer is known with a drum and a drum drive. A discrete dry sensor is provided for this purpose. This can be used to determine the moisture content of the laundry in the drum.

From the DE 42 43 594 A1 a tumble dryer and a method for controlling is known, wherein a humidity sensor unit has a discrete humidity sensor, which is arranged adjacent to a drying drum. This allows the degree of moisture in the laundry in the drum to be determined directly.

From the DE 10 2015 217 667 A1 a tumble dryer and a method for its operation are known in which a discrete moisture sensor is arranged next to a temperature sensor in an air duct away from the drum. The humidity in the exhaust air can be determined using the discrete humidity sensor.

From the WO 2016/170881 A1 a fan is known which can heat conveyed air. For this purpose, two induction heating coils are arranged on the valve housing, which are controlled accordingly can become. You can inductively heat a part of the rotor of the fan, which is made of a suitable material, for example iron. This can be provided for a base plate of the rotor, for example.

From the US 2013/0257331 A1 it is known for a general motor that a component of the electric motor changes depending on the air humidity so that a drive characteristic changes. However, this relates purely to engine-internal aspects.

task and solution

The invention is based on the object of creating a tumble dryer as mentioned at the outset and a method as mentioned at the outset with which problems of the prior art can be solved and in particular it is possible to dry laundry quickly, efficiently and also as gently as possible.

This object is achieved by a tumble dryer having the features of claim 1 and by a method having the features of claim 13. Advantageous and preferred configurations of the invention are the subject matter of the other claims and are explained in more detail below. Some of the features are only explained for the tumble dryer or only for the process. However, independently of this, they should be able to apply both to the tumble dryer and to the process independently and independently of one another. The wording of the claims is made part of the content of the description by express reference.

A laundry dryer according to the invention has a drum for receiving laundry to be dried and a drive motor for the drum. An air exhaust towards the drum as well as an air exhaust away from the drum are provided. These are advantageously channels with a large cross section, as is customary per se. An airflow fan is provided to move the airflow toward the drum through the air duct. The same fan sucks air out of the drum or away from the drum through the mentioned air discharge. The fan has its own fan drive, which in principle can be of a very general type.

Furthermore, heating means are provided for heating the air flow, which is essential for the drying function. Temperature sensing means are provided to sense the temperature of the air fed into the drum or, alternatively, the air exhausted from the drum. Provision can also be made for detecting the temperature of the air in both cases. Humidity detection means are also provided for correspondingly detecting a humidity of the air fed into the drum and/or the air discharged from the drum. According to the invention, the humidity of the air that is discharged from the drum is measured in any case, in order to obtain information about how much humidity is still present in the drum or how damp the laundry is. The temperature can be recorded in a similar way.

The tumble dryer has a control which, on the one hand, has a memory in which at least one default curve for the progression of temperature and/or humidity over time for a specific laundry drying program is stored. This drying program can be adapted to the type of laundry or its main fiber content and to a user's preference as to whether drying should take place gently or quickly. On the other hand, the controller also has arithmetic means that are designed to compare values for temperature and/or moisture currently recorded during a drying program, depending on the drying phase in the laundry, with an aforementioned default curve. In this way it can be determined at which operating point of the default curve the drying program is located. The currently recorded values for temperature and/or humidity are used for this purpose. Either only one default curve is provided, in which case the working point can be determined directly within this default curve. Alternatively, a number of different default curves can also be provided for this specific drying program, for example depending on the load quantity. Then the most suitable default curve can also be determined by comparison with the recorded values, and then the working point can be determined within this default curve.

The controller is designed to influence the further drying program or the further drying process on the basis of the operating point determined. In particular, it can be optimized, for which purpose the temperature of the air flow can be adjusted or changed by influencing the heating means. In addition or as an alternative, the strength of the air flow can be adjusted by influencing the fan, ie air can be supplied to the drum to a greater or lesser extent or blown into it.

The controller can also cause or control a drum movement or the drive motor for the drum separately and as desired. By adapting the drum movement, a named method for determining the temperature and/or humidity of the laundry can be optimally supported.

In particular, it is therefore possible with the invention to influence the further course of the drying program with regard to the temperature and/or strength of the air flow in order to advantageously reduce the temperature of the air flow to the drum during the last quarter of the drying program below the average of the previously used temperature of the to reduce airflow. For this it is important to know at which operating point of the default curve the drying program is located. The temperature can particularly advantageously be lowered at least 5°C below this average, possibly even lowered at least 15°C up to 20°C. Furthermore, the air flow rate to the drum should be increased above the average of the previously used air flow rates, advantageously increased by at least 20%, most advantageously increased by at least 50%. In this embodiment of the invention, the knowledge can thus be implemented that during the last quarter of the drying program the laundry is already largely or largely dry and is very warm in the outer area or in the outer layers. Further or continued heating brings only little or nothing here, so that energy can be saved by lowering the temperature of the supplied air and the laundry can also be protected. Rather, the increased blowing in of air at the end of drying then removes the moisture from the already strongly heated laundry better.

With air drying, the water or moisture from the laundry evaporates with the help of warm, dry air. This is supplied, gives off heat to the laundry to evaporate the moisture and absorbs the moisture from the laundry in the process. The moist air is then discharged.

Drying in a tumble dryer is mainly done by air drying. In the tumble dryer, temperature, air throughput and drum movement are coordinated in such a way that a consistently good drying result is achieved. In addition, contact drying could possibly be provided, preferably by heating the drum.

In a further advantageous embodiment of the invention, the strength of the air flow can be reduced at the beginning of the drying program, in particular during the first third or the first quarter of the estimated duration, and its temperature can be increased for this purpose. In this way, the laundry to be dried, which is still very damp or has almost the initial moisture content, can be heated as quickly as possible so that the moisture on the material surface can then evaporate better.

In order to achieve the best possible effect for the air supply, it can be provided that it is provided at most 10% of the diameter of the drum below its highest point. Advantageously, the air supply can even be provided at the highest point of the drum. This ensures that the air supply is not directly covered by laundry or unintentionally sealed. Furthermore, in the event that air is also sucked off at the air supply in order to record the temperature and/or the humidity of the air in the drum, this recording can be prevented as little as possible by laundry located close to it.

In the case of the invention, the fan direction or the direction of the air flow is reversed several times at intervals. Air can then be sucked out of the drum into the air supply, not at the air discharge but at the air supply. Information about the exhaust air or the air from the drum is obtained from this. According to the invention, this is information regarding the humidity of the exhaust air, which can be used for the aforementioned determination of the working point on a default curve or for determining the default curve itself. This is also information regarding the temperature of the exhaust air, if applicable. This is particularly advantageous when the temperature detection means and the humidity detection means are arranged in the air supply close to the drum. This is explained in more detail below.

The fan is preferably arranged close to the drum. A distance can be a maximum of 50 cm from the drum, preferably a maximum of 30 cm or even only 20 cm.

While in the prior art the fan is usually driven by the drum drive, and the fan drive is therefore always the same due to a predetermined constant speed of the drum, which prevents the strength of the air flow from varying, the fan drive in an advantageous embodiment of the present invention is its own drive that only for the fan is provided. In a particularly advantageous manner, the fan drive forms a structural unit together with the fan. Suitable power electronics are provided for controlling the fan drive, which can advantageously be steplessly adjusted. However, this is known in the prior art and is not a problem.

In an advantageous embodiment of the invention, the fan has an inductively heatable fan rotor, which thus forms a heating means for heating the air flow for the drum. For this purpose, the fan rotor can have a plurality of fan blades, wherein at least one fan blade consists at least partially of material that can be heated by means of a magnetic field generating means or has such a material. This material is preferably provided in a radially outer area of the fan rotor or the fan blades, as a result of which it can be arranged as close as possible to the magnetic field generation means mentioned. Provision can be made for a fan blade to be formed entirely from such a material. With inductive heating of this fan blade, the air conveyed by it can thus be heated as well as possible.

The magnetic field generating means are preferably arranged adjacent to the fan rotor and/or can at least partially surround it. They can also be arranged in or on a fan housing. An example of such an inductively heatable fan is known from DE 102017210527.5 the same applicant with the filing date of June 22, 2017. In an advantageous embodiment of the invention, the at least one magnetic field generating means has at least one induction coil or is such an induction coil. A single induction heating coil is advantageously provided for a fan. Depending on the design of the fan or fan rotor, it can be wound around the fan rotor radially outside of the fan rotor, so that its coil axis coincides with the axis of rotation of the fan rotor. Alternatively, a plurality of induction coils may be arranged around the fan rotor adjacent to one another such that their coil axes are perpendicular to and point towards the axis of the fan rotor.

In this case, it is advantageously possible for the temperature detection means to include the fan rotor and the magnetic field generation means in the form of the induction coil. The temperature of the inductively heatable fan blade or of the inductively heatable fan rotor can be detected from the activation of the induction coil and thus also the temperature of the air flow generated by the fan or the conveyed air. Such an inductive temperature measurement is generally known to those skilled in the art for induction heaters, for example in the field of induction hobs including induction heating coils. On the one hand, the temperature of the air blown into the drum can thus be detected in order to regulate the heating means to a desired temperature. On the other hand, when reversing the direction of rotation of the fan rotor and the air flow, the temperature of the air extracted directly from the drum can be measured. In this way, the temperature in the drum can be recorded almost directly, so to speak.

Thus, in this configuration, the heating means for heating the air flow can simultaneously form the temperature detection means. A separate temperature sensor can be saved by using the fan or the fan rotor for temperature measurement.

Alternatively, separate, discrete temperature sensors can be provided, which are advantageously arranged in the air supply near the drum, so that the temperature of the air can be measured as quickly and immediately as possible after being sucked out of the drum. However, these discrete temperature sensors can then also be provided on the air discharge from the drum close to the drum. Then, in principle, any heating means can be provided; even inductive heating of the fan rotor can be provided in the embodiment described above by means of at least one permanent magnet. This can be arranged alone or together with other permanent magnets near the fan rotor in a form similar to the induction coils described above for inductive heating of the fan rotor. A complex induction generator for the aforementioned induction coils can then be dispensed with, which significantly reduces the number of components.

In principle, a magnetic field generating means for an inductively heatable fan rotor can be arranged outside of a fan housing or outside of the air supply. In this way, an air flow is impaired as little as possible.

Such a magnetic field generating means can extend radially outside the fan rotor, preferably only at the axial level of the fan rotor and not above or below it.

In the case of the invention, the moisture detection means mentioned at the outset are implemented in or through the fan or comprise the fan and its drive. This is because the humidity of the conveyed air can be determined from the activation of the fan drive. This utilizes the fact that when there is high humidity in the air moved by the fan, a high torque has to be provided by the drive, while when there is low humidity in the air moved by the fan, a lower torque has to be provided. This is simply due to the fact that the specific density is higher in the first case than in the second case, so that in the first case more power or a higher torque has to be provided by the fan drive. During normal operation of the fan to draw air into the drum via the air duct, a such detection of humidity in the air is not necessary. In the case of a condensation dryer, for example, the humidity here will usually be relatively low. Rather, the moisture in the air sucked out of the drum is detected with this option when the fan direction or the direction of the air flow is reversed as mentioned above. Since a separate fan drive with its own control is provided anyway, this is also used as a moisture detection means. Then separate moisture detection means can be dispensed with. A phase shift between current and voltage in the fan drive is advantageously monitored to evaluate whether a high or a low torque is to be produced by the fan drive. In this way, the level of said torque can be determined, this relationship being known in principle to a person skilled in the art.

In an advantageous embodiment of the invention, the inside of the drum of the tumble dryer according to the invention is free of sensors. In this way, it can be designed in a simplified manner with increased operational reliability, since no sensors can break. The drum may also not have any sensors on its outside, as a result of which it can also be designed in a simple and reliable manner in this regard.

These and other features emerge from the claims, the description and the drawings, with the individual features being realized individually or in combination in the form of sub-combinations in one embodiment of the invention and in other areas and are advantageous and protectable in and of themselves Designs may represent for which protection is claimed here. The subdivision of the application into individual sections and subheadings do not limit the general validity of the statements made thereunder.

Brief description of the drawings

Fig. 1

eine schematische Darstellung eines erfindungsgemäßen Wäschetrockners mit induktiv beheiztem Lüfter samt separatem Lüfterantrieb,

Fig. 2

eine vergrößerte Darstellung einer alternativen Ausgestaltung einer Luftzuführung mit Abzweig zu einem separaten Auslass aus einem Gehäuse,

Fig. 3

eine Darstellung von Verläufen von Trocknungsparametern über der Zeit,

Fig. 4

eine Darstellung von Verläufen der Feuchtigkeit der Luft und der Wäsche über der Zeit mit vier Phasen und

Fig. 5

eine Darstellung von Verläufen der Temperatur der in eine Trommel des Wäschetrockners eingebrachten Luft und der Wäsche über der Zeit mit vier Phasen.

Exemplary embodiments of the invention are shown schematically in the drawings and are explained in more detail below. In the drawings show:

1

a schematic representation of a tumble dryer according to the invention with an inductively heated fan including a separate fan drive,

2

an enlarged view of an alternative embodiment of an air supply with a branch to a separate outlet from a housing,

3

a representation of the progression of drying parameters over time,

4

a representation of the progression of the humidity of the air and the laundry over time with four phases and

figure 5

a representation of the curves of the temperature of the air introduced into a drum of the tumble dryer and the laundry over time with four phases.

Detailed description of the exemplary embodiments

In the 1 is shown how a tumble dryer 11 can be basically constructed according to the invention. The tumble dryer 11 has a housing 12 with a drum 14 which is arranged in a drum receptacle 18 . The drum 14 can be driven by a drum drive 15 by means of a drive belt 16, as is basically known. The drum 14 usually rotates at a single possible rotational speed, which then also remains constant. However, this can also be varied. The drum 14 has no sensors or the like here. especially not for temperature or humidity.

A channel-like air supply 20 approaches the drum receptacle 18 at the top right, as is known per se from the prior art. This elevated position is important and beneficial, as previously explained. A fan 21 together with a fan rotor 22 and a fan drive 24 is arranged in the air supply 20, advantageously as a structural unit. As explained above, the fan rotor 22 is made of inductively heatable material, especially the individual rotor blades. It can thus be inductively heated by two induction coils 26a and 26b arranged outside the air supply 20 opposite the fan rotor 22 and surrounding it. This is also known from the prior art. The heating can be varied depending on the strength of the magnetic field generated by the induction coils 26a and 26b and also depending on the speed of the fan rotor 22. Such a fan 21, which can be heated inductively, is known.

The drum drive 15, the fan drive 24 and the induction coils 26a and 26b are connected to a controller 28 of the tumble dryer 11. This carries out the method explained at the outset as well as the other operations of the tumble dryer. The controller 28 advantageously has an appropriately designed processor.

In addition, an air discharge 40 is also arranged on the drum receptacle 18 at the top left, which leads to a condenser 42 in that water is separated from the moist air that is sucked out of the drum 14 in a known manner. It can be seen that the drum 14, air discharge 40 and air supply 20 form a kind of circuit, the air in it being moved or circulated counterclockwise, so to speak. This ventilation direction corresponds to normal, customary dry operation. Instead of the condenser 42 in the air discharge 40, the tumble dryer 11 can also use a heat pump or dehumidify the air sucked out of the drum 14 at the air discharge 40 in some other way.

The controller 28 is designed to determine the temperature of the fan rotor 22 or the inductively heatable parts present on it based on the activation of the induction coils 26a and 26b. The temperature of the air flowing past it can thus be recorded indirectly, which is also advantageous or even necessary in normal heating operation. Furthermore, the controller 28 controls the fan drive 24 of the fan 21 so that it knows or can determine the power to be applied. From this, as explained at the outset, conclusions can be drawn about the humidity in the transported air. Finally, the controller 28 can advantageously contain a converter or inverter for the fan drive 24 or can be designed as a structural unit therewith. It can also have an induction generator for driving the induction coils 26a and 26b or form a structural unit therewith. Thus, in one embodiment of the invention, a central control unit could be provided, which takes over the aforementioned control functions and a power supply.

The controller can also be a combination of an inverter and a controller or microcontroller and measuring means, for example a current measuring coil or a current shunt. A zero-crossing detection can also be provided. In the 2 an alternative tumble dryer 111 is shown as a variation in an enlarged view, which has an additional outlet 130 in its housing 112 . This outlet 130 opens into a branch 132 which branches off at the top from the air supply 120 or is connected to it. It is closed by a branch flap 134, which can be opened downwards and closed upwards by a flap actuator 136, ie it can be moved. The flap actuator 136 can be a rod drive, alternatively an electromagnet or the like.

A smaller second fan rotor 123 is attached to a fan 121 on the same shaft on which a larger first fan rotor 122 is also seated. The second fan rotor 123 is designed to convey air in the opposite direction of rotation to the first fan rotor 122 . If the fan drive 124 rotates in its normal direction, then the first fan rotor 122 conveys air through the air supply 120 according to the large arrow into the drum receptacle 118 and thus also into the drum 114 according to normal operation. It can be heated in the manner described above by induction coils 126a and 126b in order to heat the conveyed air for dryer operation. The second fan rotor 123 can also consist partially or entirely of inductively heatable material. If the fan drive 124 rotates in the opposite direction of rotation for which the second fan rotor 123 is designed, the air flow is generated according to the thinner arrow and air is sucked out of the drum 114 into the air supply 120 . When the branch flap 134 is open downwards and is shown in broken lines, this air flows upwards through the outlet 130, out of the housing 112 here by way of example. Alternatively, it could also be routed back into the duct of the air discharge 40 via a return, as a result of which the escape of fluff can be reduced or avoided. Of course, this air from the drum 114 does not have to be heated, here the heating function by means of the induction coils 126a and 126b serves to detect the temperature of this extracted air in this way. As explained at the outset, this takes place using the operating values of the induction coils 126a and 126b. The first fan rotor 122 can have no effect in this second opposite conveying direction; it may be able to contribute to the conveying of air in this direction, but this is not necessary. Finally, the second fan rotor 123 is provided for this purpose.

Is according to the 1 only a single fan rotor 22 provided on the fan 21, it should be designed for operation in both directions. A significantly better degree of efficiency can be provided for blowing air through the air supply 20 into the drum 14, but it should also be possible, at least in principle, in the other direction. The fan drive 24 or 124, which is independent of the drum drive 15, allows the fan 21 or 121 to be operated as desired and independently.

The extraction of air from the drum 114 to detect the temperature of this air does not have to be long, for example it can be as short as 2 seconds to 10 seconds.

Simultaneously with the detection of the temperature of the suctioned or discharged air from the drum 114, the instantaneous power of the fan drive 124 can also generally be detected by monitoring the fan drive 124 and its operating values. From this, as explained above, the humidity of the extracted air and thus inside the drum 114 can be determined. The more power the fan drive 124 has to apply for suction at a specific speed, the more humid this air is. The wetter the laundry in drum 114 is then.

Determining the humidity of the air discharged from the drum, possibly also the air fed into the drum 114, is advantageously carried out by determining a phase shift in the fan drive 124, since the required torque changes with the dependency of the viscosity of the air on its moisture content. Air with a high moisture content is simply more difficult to transport than dry air. A corresponding reference in the controller or a previous "calibration" in dry air allows this determination. Such a measurement can be taken at the in 2 shown double fan 121 can be performed well. The difference between sucking the air out of the drum 114 and blowing air into the drum is measured. Useful information about this process can be obtained from the difference.

The heating of the air via the inductively heated fan rotor 22 or 122 or 123 allows the energy absorbed by the induction coils 126a and 126b to be evaluated in parallel. The profile of the energy consumed can be seen on an induction generator (not shown) via corresponding control variables, which provides information about the temperature of the fan rotors, since a comparison with existing characteristic curves is possible. A dynamic electromagnetic excitation of the induction coils 126a and 126b can provide further information about the temperature of the air. If the energy input or the power output to the induction coils 126a and 126b is regulated with the aim of not heating the air but rather keeping the fan rotor at the temperature of the air being conveyed, then the change compared to known characteristic curves can also Indicate the humidity of the air or its change.

The combination of the two pieces of information from the recording of moisture and temperature allows the process to be carried out independently of direct temperature measurement, since known characteristic values can be recorded and compared with those actually present in the process. This enables process-oriented control of the humidity and ideal air temperature parameters. Known parameters such as outside temperature and pressure, which are measured here with sensors, can also support the control. In particular, the influences of the laundry, which are very random due to their different composition, can be recognized more quickly, since other parameters such as drum movement and thus laundry movement can be included in the evaluation of the measurement results.

In the 3 different curves of parameters over time t are shown. Curve 1 is the relative humidity or humidity of the laundry. Parameter 2 in the diagram below is the mass flow of removed moisture, given in kg/(m ² s). The parameter of curve 3 is the surface temperature T _WO of the laundry. The course 4 of the corresponding Parameters shows the core temperature T _WK of the laundry, and curve 5 is the temperature T _L of the air supplied. All temperatures are given in °C.

In section I, the laundry is heated and the moisture on the material surface is evaporated. The drying intensity is not great, because on the one hand the heat transferred is not only needed to evaporate the moisture, but above all to heat the entire laundry. On the other hand, the thermal moisture conductivity, which increases due to the temperature difference between the surface and the core, slows down the removal of moisture.

One definition of thermal moisture conductivity is that the moisture content of the laundry changes constantly during drying. This creates a concentration gradient between the textile surface, from which moisture is continuously removed, and the inner layers of the laundry items, which causes a moisture transport from places with higher to places with lower moisture concentration according to moisture diffusion, also known as moisture conductivity. The moisture is therefore transported to the surface of the laundry or to the location of the evaporation limit, where it is converted into steam, which mixes with the heated air, and is discharged into the environment. In the course of the drying process or drying program, the evaporation limit moves from the surface of the laundry into the interior of the laundry.

Since heat is supplied for the evaporation, the material to be dried is heated in addition to removing the moisture. The heat supply via the surface creates a temperature difference between the surface and the inner layers or the core.

Moisture has a tendency to migrate from higher to lower temperature locations due to effects related to the binding of liquids in capillaries. This phenomenon is called thermo-humidity. If the surface temperature is higher than the core temperature, the vectors of moisture conductivity and thermal moisture conductivity have different signs, i.e. the drying process slows down. The influence of thermal moisture conductivity decreases as the material to be dried increases in temperature as the temperature gradient decreases. With increasing heating of the laundry, the temperature difference across the cross-section of the laundry also decreases, which leads to an increase in the drying speed.

In section II the drying rate is constant. The temperature of the surface and inner layers or core differ only slightly and are only subject to minor changes. A steady state is established, the influence of the thermal moisture conductivity is eliminated, and the drying process is exclusively determined by the moisture conductivity.

In section III, the drying rate decreases again. With increasing heating, the evaporation limit moves from the surface into the inner layers or the core of the laundry. The heat supplied via the air is no longer used only or mainly for evaporating the moisture, but increasingly for heating the laundry. In section III, the partial pressure difference between the inner and outer layers of the laundry is crucial for the transport of moisture to the surface of the laundry. At the end of section III, the removal of moisture from the laundry is complete and the temperature of the laundry is approaching the temperature of the air. Overall, the drying speed depends on the conditions of heat transfer at the laundry surface and the distance of the water vapor from the evaporation line.

In the 4 is marked with triangles the time course of the moisture f _L in the air as it was measured during a drying process. During phase 1 for the first 9 minutes, this humidity in the air increases sharply to almost 100%. It remains at this high value for another 12 minutes during phase 2. During phase 1, the time profile of the moisture content f _W of the laundry, marked by rectangles, decreases only slightly. This moisture f _W of the laundry has been determined experimentally for the same time and cannot be directly correlated with the tumble dryer Fig. 1 or Fig. 2 are recorded. During phase 2, the moisture f _W of the laundry decreases sharply, which is not surprising since the air discharged during this phase is at most or almost fully saturated, see moisture f _L .

In the subsequent phase 3, which lasts about 20 minutes, the humidity f _W still decreases, but this decrease flattens out. Accordingly, the humidity f _L also decreases greatly. During the last phase 4, which lasts about 5 minutes, hardly any moisture can be removed into the air, but the laundry is dry or completely dry, since its moisture content f _W reaches zero or even slightly below.

In figure 5 is accordingly closed 4 divided into the four phases a curve for the temperature T _L of the discharged air shown with triangles during the same drying process. A curve for the temperature T _W of the laundry is also shown with rectangles. It roughly corresponds to the core temperature T _WK of the curve 4 in 3 . The temperature T _W of the laundry, like the moisture f _W of the laundry, has been determined experimentally.

It can be seen that in phase 1 the temperature T _L is increased rapidly to around 40°C. In phase 2, the temperature T _L is again increased to just over 50 °C. In phase 1, on the other hand, the temperature of the laundry T _W , which is shown as a rectangle, increases with a delay. Then, during phase 2, a temperature rise is greatly reduced.

Only at the beginning of phase 3 again, when the temperature T _L has also been increased somewhat, does the temperature T _W rise again slightly with two brief downward lapses, even if the temperature T _L also has corresponding dips.

In the relatively short phase 4, the temperature T _W rises even further, while the temperature T _L is lower and tends to remain the same or even drop somewhat.

Both the theoretical considerations and the considerations based on experiments indicate that the drying process can be optimized if the measurement of the parameters for temperature and humidity is optimized.

In detail, in phase 1, it is recommended to accelerate the process of increasing the temperature of the laundry so that evaporation begins as quickly as possible. In phase 2, the temperature T _W is equal to the temperature T _L , so that the energy supplied is used for evaporation. In phase 3, an increase in the temperature T _L makes little or no sense, since this only leads to an increase in the temperature T _W and not to an acceleration of evaporation due to the thermodynamic effects. Phase 4 is necessary because of the non-uniform moisture distribution, which is more difficult to remove because it is "bound moisture". The decisive factor here is the combination of heat output, air rate or convection and drum movement. Furthermore, the focus is on the heating capacity.

• Aufwärmen der Wäsche
• Konstantes Wärmen der Wäsche
• Konstante Trocknungsphase ohne Wärme oder mit wenig Wärme
• Durchblasen der Wäsche ohne Wärme oder mit wenig Wärme Werden die aktuellen Heizsysteme verwendet, dann kann über die Regelung und Steuerung eine Verbesserung erzielt werden.

For the four phases, the function is divided into:

• Warm up the laundry
• Constant heating of the laundry
• Constant drying phase with no or little heat
• Blowing through the laundry without heat or with little heat If the current heating systems are used, an improvement can be achieved through regulation and control.

At the same time, a combination of an air heating system with an integrated heater in the fan allows the measurement function to be optimized with fewer components and increased data acquisition. The aim is to use indirect information from the process for the process. Ultimately, parameters that are directly related to the convection and evaporation of water in the dryer should be recorded and used for process control. A mentioned method for detecting parameters for the process control can be optimally supported by the mentioned possibility of any control of the drum movement or the drive motor for the drum.

This means that existing sensors cannot necessarily be replaced, but supplemented. Above all, an attempt can be made to do without sensors in the drum itself, since these are expensive to attach and evaluate.

With the knowledge of these courses over time according to the Figures 3 to 5 By detecting the temperature and humidity of the air in the drum, which can be done according to the invention without sensors in the drum, it can be concluded at which point of such a course the drying process is. It can then be optimized, in particular to the effect that towards the end the temperature T _L no longer has to be so high. Energy can thus be saved and the laundry to be dried can also be protected. It is thus possible to improve the drying of laundry with a tumble dryer, in particular the tumble dryer according to the invention described above.

Claims (15)

1. A laundry dryer (11, 111) comprising:

   - a drum (14, 114) for receiving laundry to be dried,

   - a drive motor (15) for the drum,

   - an air supply (20, 120) to the drum,

   - an air exhaust (40) from the drum,

   - a fan (21, 121) for generating an air flow toward the drum (14, 114) through the air supply (20, 120) and away from the drum through the air exhaust (40)

   - a fan drive (24, 124) for the fan (21, 121),

   - heating means (26a, 26b, 126a, 126b) for heating the air flow,

   - temperature detection means for detecting the temperature of the air supplied to the drum (14, 114) or of the air discharged from the drum,

   - humidity sensing means for sensing the humidity of the air supplied into the drum (14, 114) or of the air discharged from the drum,

   - a controller (28) comprising:

   o a memory in which at least one preset curve for the course of temperature and/or humidity over time for a specific drying program of laundry is stored,

   o computing means which are designed to compare values for temperature and/or humidity currently detected during a drying program, depending on the drying phase of the laundry, with a preset curve and to determine at which operating point of the preset curve the drying program is located,

   - the controller (28) being designed to influence the further drying program on the basis of the operating point by means of an adaptation of the temperature of the air flow by influencing the heating means (26a, 26b, 126a, 126b) and/or by means of an adaptation of the strength of the air flow by influencing the fan (21, 121),

   characterized in that:

   - the humidity detection means surround the fan (21, 121) and a fan drive (24, 124), respectively,

   - the humidity can be determined from the control of the fan drive (24, 124) of the fan (21, 121) in such a way that, in the case of high humidity in the air moved by the fan, a high rotational torque is to be provided by the drive and, in the case of low humidity in the air conveyed by the fan, a low torque is to be provided by the fan drive,

   - the controller (28) is designed to determine the humidity in the air from the control of the fan drive (24, 124) of the fan (21, 121),

   - the direction of the fan or the direction of the air flow is reversed several times at time intervals in order to then suck air out of the drum (14, 114) into the air supply (20, 120) in order to obtain information about the exhaust air, the information comprising the humidity of the exhaust air.
2. Laundry dryer according to claim 1, characterized in that the air inlet (20, 120) is provided at most 10% below the highest point of the drum (14, 114), in particular above the highest point of the drum.
3. Laundry dryer according to claim 1 or 2, characterized in that the fan (21, 121) is arranged close to the drum (14, 114), preferably at a maximum distance of 50 cm from the drum, in particular at a maximum distance of 30 cm.
4. Laundry dryer according to one of the preceding claims, characterized in that the fan drive (24, 124) is a separate drive only for the fan (21, 121), preferably as an assembly unit together with the fan.
5. Laundry dryer according to one of the preceding claims, characterized in that the fan (21, 121) has an inductively heatable fan rotor (22, 122) as heating means, preferably the fan rotor (22, 122) having a plurality of fan blades, wherein at least one fan blade consists at least partly of material heatable by means of a magnetic field generating means (26a, 26b, 126a, 126b) or comprises such material, in particular in a radially outer region, wherein preferably at least one fan blade consists entirely of this material.
6. Laundry dryer according to claim 5, characterized in that the at least one magnetic field generating means (26a, 26b, 126a, 126b) is arranged adjacent to the fan rotor (22, 122) and/or at least partially surrounds the fan rotor and/or is arranged on a fan housing.
7. Laundry dryer according to claim 6, characterized in that the at least one magnetic field detection means comprises or is at least one induction coil (26a, 26b, 126a, 126b), preferably a single induction coil, wherein in particular the temperature detection means comprise the fan rotor (22, 122) and the magnetic field generating means as an induction coil (26a, 26b, 126a, 126b), wherein the temperature of the air discharged from or supplied to the drum (14, 114) can preferably be determined from the control of the induction coil.
8. Laundry dryer according to claim 6, characterized in that the at least one magnetic field generating means comprises at least one permanent magnet, preferably several permanent magnets.
9. Laundry dryer according to any one of claims 5 to 8, characterized in that the at least one magnetic field generating means (26a, 26b, 126a, 126b) is arranged outside a fan housing or outside the air supply (20, 120).
10. Laundry dryer according to any one of claims 5 to 9, characterized in that the at least one magnetic field generating means (26a, 26b, 126a, 126b) extends in radial extension outside the fan rotor (22, 122), preferably only at the axial level of the fan rotor and not above or below it, wherein in particular the at least one magnetic field generating means is arranged radially outside the fan rotor and circumferentially as an induction coil (26a, 26b, 126a, 126b) with a coil center axis which runs parallel to an axis of rotation of the fan rotor (22, 122) or coincides with the axis of rotation of the fan rotor.
11. Laundry dryer according to any one of the preceding claims, characterized in that the torque from the fan drive (24, 124) is determinable by monitoring a phase shift between current and voltage in the fan drive.
12. Laundry dryer according to any one of the preceding claims, characterized in that the drum (14, 114) is internally free of sensors, preferably also having no sensors on the outside.
13. Method for drying laundry to be dried with a laundry dryer (11, 111), wherein the laundry dryer comprises:

    - a drum (14, 114) for receiving laundry to be dried,

    - a drive motor (15) for the drum,

    - an air supply (20, 120) to the drum,

    - an air exhaust (40) from the drum (14, 114),

    - a fan (21, 121) for generating an air flow towards the drum (14, 114) through the air supply (20, 120) and away from the drum through the air exhaust (40),

    - a fan drive (24, 124) for the fan,

    - heating means (26a, 26b, 126a, 126b) for heating the air flow,

    - temperature detection means for detecting the temperature of the air supplied to the drum (14, 114) or of the air discharged from the drum,

    - humidity detecting means for detecting the humidity of the air supplied into the drum (14, 114) or the air discharged from the drum,

    - the humidity detection means comprising the fan (21, 121) or a fan drive (24, 124),

    - the humidity is determinable from the control of the fan drive (24, 124) of the fan (21, 121) in such a way that at high humidity in the air moved by the fan a high torque is to be provided by the drive and at low humidity in the air conveyed by the fan a low torque is to be provided by the fan drive,

    - a control system (28) with:

    o a memory in which at least one preset curve for the course of temperature and/or humidity over time for a specific drying program of laundry is stored,

    o computing means for comparing values for temperature and/or humidity currently detected during a drying program with a preset curve and for determining at which operating point of the preset curve the drying program is located,

    - the controller (28) is designed to determine the humidity in the air from the control of the fan drive (24, 124) of the fan (21, 121),

    with the steps:

    - current values for temperature and/or humidity during a drying program are detected,

    - the actual detected values for temperature and/or humidity are compared with a preset curve,

    - the comparison is used to determine at which operating point of the preset curve the drying program is located,

    - the further drying program is influenced on the basis of the operating point with regard to an adjustment of the temperature of the air flow by influencing the heating means (26a, 26b, 126a, 126b) and/or by means of an adjustment of the strength of the air flow by influencing the fan (21, 121),

    - the direction of the fan or the direction of the air flow is reversed several times at time intervals, in order to then suck air out of the drum (14, 114) into the air supply (20, 120) in order to obtain information about the exhaust air, the information comprising the humidity of the exhaust air.
14. Method according to claim 13, characterized in that the further drying program is influenced with regard to the temperature and/or strength of the air flow, preferably especially during the duration of the last quarter of the drying program, whereby then:

    - the temperature of the air flow to the drum (14, 114) is at least 5°C below the average of the temperature of the air flow used so far, preferably at least 15°C,

    - the strength of the air flow to the drum (14, 114) is at least 20% above the average of the previously used strength of the air flow, preferably at least 50%.
15. Method according to claim 13 or 14, characterized in that information regarding the temperature of the exhaust air is obtained by reversing the fan direction or the direction of the air flow.

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