DE102014216853A1 - Method for loading-dependent operation of a dryer and dryer suitable therefor - Google Patents

Abstract

The invention relates to a method for operating a dryer 1 with a program control 8, a drum 3 for laundry to be dried and a process air duct 2, in which a process air blower 6 for the transport of the process air and a heater 4 for heating the process air are Method comprises a heating phase, a first drying section, a second drying section and a cooling phase and wherein before the start of the second drying section, the load L determined and assigned to one of at least two predetermined loading conditions Lgering or Lhoch and during the second drying section for the loading state Lgering or Lhoch specific circuit pattern M2gering or M2hoch of the heater 4 for heating power reduction takes place, wherein the circuit patterns M2gering and M2hoch at least with respect to the extent AHVS or the duration tHVS a single Heizleistungsverringerungsschaltung HVS erscheiden. The invention also relates to a dryer 1 suitable for carrying out this process.

Description

The invention relates to a method for the load-dependent operation of a dryer and a suitable for carrying out this method dryer. The invention relates in particular to a method for operating a dryer with a program control, a drum for items to be dried and a process air duct in which a process air blower for the transport of the process air and a heater for heating the process air, wherein the method is a heating phase, a first drying section, a second drying section and a cooling phase and before the start of the second drying section determines the load L and one of at least two predetermined loading conditions L _low or L _high , and a particularly suitable for carrying out this method dryer.

In a dryer, air (so-called process air) is passed through a process air blower via a heater in a drum containing the laundry items to be dried as a drying chamber. The hot air absorbs moisture from the laundry to be dried. In an exhaust air dryer, the moist, warm process air is directed to the outside, for example in a storage room. In a condensation dryer, on the other hand, the moist, warm process air is passed, after passing through the drum, into a heat exchanger, which is usually preceded by a lint filter. In this heat exchanger (for example, air-to-air heat exchanger), the moist, warm process air is cooled, so that the water contained in it condenses. The condensed water (condensate) is then usually collected in a suitable container and the cooled and dried air again fed to the heater and then the drum.

The drying process in a tumble dryer is generally divided into three phases. In this case, a heating phase first takes place during which the temperature of the process air rises until a certain temperature value is reached. This is followed by a main drying phase, during which the main drying of the laundry takes place. The main drying phase may be subdivided into a first and a second drying section, the first drying section being quasi-stationary, i. that the temperature of the process air is substantially constant. Likewise, in the first drying section, the drying rate is substantially constant, because on the surface of the laundry, the water evaporates continuously. In the subsequent second drying section then slows down the drying rate, since the remaining moisture must be transported to the surface of the laundry only by the capillaries located in the substance, causing delays and thus no continuous evaporation of the laundry surface more. The drying process is then completed with a cooling phase in which the heating is generally switched off. The process air blower generally remains switched on during the cooling phase in order to exploit the residual thermal energy still present in the drum and process air circuit.

Such drying processes are known to be very energy consuming. Thus, it is of great interest to reduce the energy consumption of dryers in order to save costs and to protect the environment. In addition, it is also desirable to treat the laundry gently and to avoid overheating. Against this background, it is known to control the heating power of the tumble dryer as a function of the temperature and / or the humidity.

The DE 44 09 531 C1 discloses a clothes dryer with a sensor for monitoring the contamination of the lint filter, in which two parallel heating elements form the heater, wherein the first of these heating elements can be switched off by means of a first thermostat when the supply air of the process air circuit reaches a predetermined temperature. Thus, the temperature of the supply air is limited regardless of the prevailing conditions in the dryer, ie regardless of load, overvoltage, too high heat output or too low air flow. The first thermostat performs a cycle operation between high and reduced heating power. In addition, a humidity sensor can be arranged, which always switches to reduced heating power when sinking below a predetermined humidity value.

The DE 32 02 586 C2 describes a method for operating a tumble dryer, wherein during a first drying phase of the tumble dryer works at least partially as a condensation dryer and the process air flow is heated by a heater. When a certain critical temperature is reached, an air damper is opened and the heating is switched off or the heating power is reduced, so that in a subsequent second drying phase the tumble dryer operates as an exhaust air dryer. When the heat stored in the heat exchanger is used up, the air damper is closed again and the heater is switched back to full heating power so that a first drying phase is carried out again. The drying process thus proceeds by further cyclically subsequent first and second drying phases. The dryer control can be done by temperature sensors or by time control.

The EP 1 441 062 B1 discloses a clothes dryer and a method for controlling the heating power, wherein the control of the heating power takes place in dependence on moisture degrees or humidity gradients. For this purpose, there is a humidity sensor in the tumble dryer, for example, a conductivity sensor or a temperature sensor in the exhaust duct. It is, for example, a time difference between two times at which predetermined degrees of humidity are reached, determined and, if this time difference exceeds a certain setpoint or below, the heating power is increased or decreased accordingly. In order to achieve the best possible line of the drying process, such a check of the drying progress during the entire drying process is performed as many times as possible and the heating power thus adjusted several times.

The US 6 199 300 B1 discloses a method of controlling the heat output in a tumble dryer while monitoring the temperature and humidity level in the dryer. If a certain temperature value, in particular a temperature plateau, is reached in the dryer, the heating power is reduced. If, however, the humidity falls below a predetermined value, the heating power is increased again to remove the residual moisture yet. The control unit of such a tumble dryer comprises at least one temperature sensor to measure the exhaust air temperature, and at least one humidity sensor.

Thus, in the known laundry drying process, the control of the heating power takes place either as a function of the temperature or of the humidity. However, temperature and humidity are generally not uniformly distributed over the process air located in the laundry chamber, since especially with increasing drying, especially in the interior of the laundry water is stored, whereas on the surface of the laundry, a higher temperature and less moisture occur. These differences can lead to delays in the current adjustment of the circuit of the heating power in conventional clothes dryers. In addition, the predictive power of temperature and / or humidity values for the further course of the drying process is rather low, so that, for example, reliable conclusions as to how much the heating power must be reduced are difficult or impossible.

The EP 0 067 896 A1 describes a method for drying laundry, in which the amount of laundry to be dried is determined and the heating power required for drying is adapted thereto. Preferably, the adjustment of the heating power takes place gradually. The adjustment of the size of the heating power can be done with a time delay with respect to the beginning of the drying process. The main advantage of this method is that it first dries with full heating power, which shortens the drying process.

The DE 11 2007 000 552 T5 describes a dryer comprising: a drum for receiving a dry object; a heater for supplying hot air to the dry object; a scanning unit for generating a measured value which is varied with an amount of the dry object in the drum; and a control unit for determining the amount of the drying object from the measured value generated by the scanning unit and controlling an operating power of the heating device according to the result of the determination. In particular, controlling a power of a heater when it is operated at full power when starting to dry has the steps of: keeping the operating power of the heater at full power when it is determined that the amount of the dry object is large, and reducing the Operating power of the heater to a power that is less than the full power, if it is determined that the amount of the dry object is small.

The DE 39 20 737 A describes a control device for a program-controlled domestic tumble dryer with a laundry drum and at least two heating elements of different heating power for the dry air, and a load state of the laundry drum or the weight of the laundry to be dried detecting sensor device with or after the beginning of the drying program with detected under load of Laundry drum for the control device provides a pulse for switching to a matched to the respective load state of the laundry drum or the laundry weight reduced heating power. In the case of a lower loading of the laundry drum, the heating device is in particular clocked as a function of the detected or detected laundry drum load.

Against this background, it was an object of the present invention to provide a method for operating a dryer with Heizleistungsverringerungsschaltung, which overcomes the disadvantages of the known laundry drying method. The object of the invention was also to provide a suitable dryer for this purpose.

The solution of this object is achieved according to this invention by a method and by a dryer with the features of the corresponding independent claims. Preferred embodiments of the method according to the invention are described in the corresponding dependent claims, the following description and attached drawing. Preferred embodiments of the method according to the invention correspond to preferred embodiments of the dryer according to the invention and vice versa, although this is not explicitly stated in the individual case herein.

The invention thus relates to a method for operating a dryer with a program control, a drum for items to be dried and a process air duct in which a process air blower for the transport of the process air and a heater for heating the process air are, wherein the method comprises a heating phase, comprising a first drying section, a second drying section and a cooling phase and wherein prior to the beginning of the second drying section the load L is determined and assigned to one of at least two predetermined loading conditions L _low or L _high and during the second drying section one _low or L _high for the loading condition L. specific circuit _pattern M _2gering or M _{2 high of} the heater for heating power _reduction takes place, wherein the circuit _patterns M ₂ and M _{2 low} at least in terms of the extent A _HVS and / or the duration t _HVS a single Heizleistungsverringersschal HVS.

"Dryer" herein means in particular a dryer for items of laundry, wherein the type of clothes dryer is not restricted according to the invention and may also include washer-dryer, so household appliances for washing and drying laundry. In particular, exhaust air dryers and condensation dryers are meant, wherein condensation dryers are preferred according to the invention.

The type of determination of the loading L of the drum is not limited according to the invention. For example, the load can be set by user input. In general, however, the loading of the drum is determined by the dryer, for example by weighing the drum and / or by evaluating a motor current and / or electrical power of the electric drive motor. The loading is preferably determined by evaluating a motor current and / or an electrical power of the electric drive motor. If, for example, the power delivered to the electric drive motor is kept constant, the dependence of the motor current on a load of the electric drive motor can be used to determine the loading state of the drum. In this case, in particular, a course of the current within a predetermined period of time, for example, during a run-up of the drum, are tracked. It can be concluded by the dependence of the torque of the electric drive motor of the loading state of the drum and due to the dependence of the torque of the motor current on the load.

At least two different loading states, for example L _low and L _high , are stored in the program control and the determined loading L is assigned to one of the predetermined loading states. In general, the respective load states are each assigned specific weight ranges. Particularly preferably, a determined loading of up to and including 4 kg is assigned to a "low loading state" L _low and a determined loading of more than 4 kg is assigned to a "high loading state" L _high . It is assumed that a maximum load of 7 kg. Furthermore, more than two different loading states L ₁ , L ₂ ,..., L _n , for example three, four or five different loading states, can also be predetermined in the program control.

The loading L of the drum is determined before the start of the second drying section. The transition between a first drying section and a second drying section is generally characterized in that the drying rate in the second drying section is not constant as in the first drying section, but decreases, since the remaining moisture only to the surface of the laundry through the capillaries located in the material must be transported. Thus, for example, the transition between the first drying section and the second drying section may be time-lagged for typical process flows in the program control or currently determined by suitable means, for example by means of temperature and / or humidity sensors. Preferably, the transition between a first drying section and a second drying section is determined by exceeding a threshold value of the process air temperature. It is advantageous if the corresponding temperature sensor, for example an NTC temperature sensor, if possible measures a temperature which correlates with the laundry temperature. Accordingly, the temperature sensor is preferably arranged at the outlet of the process air channel from the drum ("drum outlet").

During the second drying section, a switching pattern of the heating for reducing the heating power, which is specific for the respective load state, expires, for example in the case of the loading conditions L _low or L _high, a switching pattern M _2gering or M _2high . In the case of several loading states L ₁ , L ₂ ,..., L _n , these can be assigned correspondingly to a plurality of switching patterns M _A , M _B ,..., M _Z. The assignment of the loading state L to a shift pattern M is usually in the program control. In this case, a "switching pattern of the heating for reducing the heating power" is generally understood as meaning such a switching pattern of the heating, which leads to a reduction of the heating power compared with the maximum possible total heating power H _tot .

In the simplest case, there is a reduction in heating power when switching off the heating completely. Preferably, however, there is no complete switching off of the heating, which is why the heating here advantageously has at least two heating stages, more preferably three heating stages. The maximum total heating power H _tot results, according to circuit, for example the sum of the heat outputs of all the heating steps, for example in three heating stages with the respective heating powers H _1, H ₂ and H _3: H _ges = H ₁ + H ₂ + H ₃ .

Accordingly, a reduction of the heating power can be achieved by switching off only one heating stage at a time or by simultaneously switching off a plurality of heating stages, for example two heating stages, without the heating being completely switched off. In this way, the amount A _{HVS of} a heating power reduction circuit HVS can be set as needed.

In general, a switching pattern includes a plurality of individual heater power reduction circuits HVS ₁ , HVS ₂ , etc. Here, under a single heater power reduction circuit HVS, switching off one or more heater stages simultaneously or turning off the entire heater for a certain period of time, namely the duration of the heater power reduction circuit t _HVS , Understood. In this case, it is generally assumed that there is a switch-off with respect to the maximum possible total heat _output H _ges . A heating power reduction circuit HVS is thus determined by its extent A _HVS and its duration t _HVS . Preferably, a switching pattern M during the second drying section only includes heating power reduction circuits of the same extent A _HVS . Moreover, a switching pattern M including multiple heat-power reduction circuits is determined by the number of heat-power reduction circuits N _HVS and the frequency of the heat-power reduction circuits f _HVS .

According to the invention, the load-specific circuit patterns during the second drying section differ at least in terms of the extent A _HVS and / or the duration t _{HVS of} a single heating power reduction circuit HVS. Accordingly, since a certain switching pattern M in the second drying section preferably has only heat sink circuits HV of the same extent A _HVS , the different switch patterns preferably differ in the extent A _{HVS of} all the heater power reduction circuits HVS.

Such a load-specific switching pattern for reducing the heat output in the second drying section has the advantage that a further increase in the process air temperature is avoided. In contrast, it would come at a constant supply of the total heating H _ges in the second drying section to a further increase in the process air temperature, which is disadvantageous because it no longer increased drying of the laundry takes place and it leads to an undesirable overheating of the laundry and even to danger a fire can come. In addition, an optimum drying process of the laundry can still be ensured by a load-specific switching pattern for reducing the heating power in the second drying section. Namely, such a switching pattern makes it possible to reduce the heating power only and, above all, only to the extent that a drying course optimized in accordance with the load is achieved.

Preferably, in a load state L _low , which corresponds to a lower load, during the second drying section in the circuit _pattern M _{2 gering} at a single _{Heizleistungsverringersschaltung} HVS, the heating power is reduced more than a single _{Heizleistungsverringersschaltung} HVS in the circuit _pattern M _2hoch that a load state L _high for a higher Loading is assigned. More preferably, the circuit patterns include only heat reduction circuits of the same extent A _HVS . Thus, in all the _heater power reduction circuits HVS of the low load L _low circuit _pattern M _{2, the heater} power is reduced more than the _heater power reduction circuits HVS in the high load L circuit _pattern M _{2 high} . For example, in a _{Heizleistungsverringerungsschaltung} in the switching pattern M _2gering at low load L _low the heating power is reduced by 20 to 30% compared to the maximum possible Gesamtheizleistung H _ges , whereas in a _{Heizleistungsverringerungsschaltung} in switching pattern M _2hoch at high load L _high, the heating power only by 5 to 10 % compared to the total _heat output H _{ges is} reduced.

In this embodiment, the duration of each heating power reduction circuits is t _HVS in the circuit pattern M _2gering at low load _low L preferably 10 to 30 seconds and particularly preferably 10 to 20s.

In this way, the influence of the load is particularly effectively implemented in the circuit pattern. It should be noted in particular that in the second drying section at low load L _slightly less water is still capillary bound in the laundry present as high load L _high . Thus, with lower loading, a higher level of heat output reduction is better tolerated not only with respect to the drying process than with high loading, but also with low load overheating is avoided.

In a preferred embodiment, the determination of the loading L and the assignment to one of at least two predetermined loading conditions L _low or L _high before the first drying section or directly at the beginning of the first drying section. In this case, the transition from the heating phase into the first drying section, which proceeds quasi-stationary, is characterized by the attainment of a specific temperature value of the process air temperature. This can be, for example, the temperature at which a temporal change in the temperature of the process air reaches a minimum. Advantageously, the corresponding temperature sensor is arranged in the dryer such that the measured temperature correlates with the laundry temperature.

As used herein, "directly at the beginning of the first drying section" means that the load detection and allocation occurs as soon as a temperature threshold is exceeded which correlates with the transition from the heating phase to the first drying section. The loading is advantageously determined by the dryer.

In this way, the assignment of a switching pattern for Heizleistungsverringerung for the second drying section can be done early. In addition, it is possible to optionally determine a load-specific switching pattern for the first drying section.

It is particularly preferred that the determination of the load L and the assignment to one of at least two predetermined loading conditions L _low or L _high at the end of the heating phase or directly at the beginning of the first drying section. At the end of the heating phase herein means that the determination of loading takes place in the temporally second half of the heating phase, preferably in the last third of the heating phase, and more preferably in the last 5 minutes of the heating phase. The loading is advantageously determined by the dryer. Thus, the load can be determined as accurately as possible in order to assign an adequate switching pattern for reducing heat output.

Furthermore, it is preferred that already during the first drying section a for the associated load state L _low or L _highly specific circuit _pattern M _1gering or M _1hoch the heater for heating power _reduction takes place, wherein the circuit _patterns M _1gering and M _1hoch at least with respect to the extent A _HVS and or the duration t _{HVS of} a single Heizleistungsverringersschaltung HVS and / or the number N _HVS and / or the frequency f _{HVS of} the Heizleistungsverringerungsschaltungen different.

The first drying section is substantially quasi-stationary, i. the temperature profile essentially forms a plateau. During the first drying section, water continuously evaporates on the surface of the laundry, so that the drying speed during the first drying section is constant. The beginning of the first drying section is thus characterized by reaching a certain temperature, namely the plateau temperature.

During the first drying section, the circuit _patterns M _1gering and M _{1h differ} at least in the extent A _HVS and / or the duration t _{HVS of} a single _{heater power reduction} circuit HVS and / or the number N _HVS and / or the frequency f _{HVS of} the _{heater power reduction} circuits. Advantageously, the circuit patterns are designed so that the temperature of the laundry is kept substantially constant. This can be implemented in various ways by adjusting the parameters magnitude _HVS and / or duration t _{HVS of} a single heating power reduction circuit HVS and / or number N _HVS and / or the frequency f _{HVS of} the heating power reduction circuits suitably according to the load. It must be taken into account in particular that at full load, the energy distribution is much more uniform over the mass to be dried than at low load.

Thus, for example, in the first drying section, it is possible to apply a higher amount A _{HVS of} the individual heating power reduction circuits at a higher load than at a lower load. Accordingly, it is preferable that, in a load state L _low corresponding to a lower load, during the first drying section in the circuit _pattern M _{1 lower, the heater} power is less reduced for a single _heater power reduction circuit HVS than for a single _heater power reduction circuit HVS in the circuit _pattern M _{1 high corresponding} to a load state L is assigned _high for a higher load. With such an increased heating power reduction in the first drying section at high loading, it is advantageous to simultaneously increase the frequency f _HVS Heater power reduction circuits compared to a lower load switching pattern to reduce.

Further, the magnitude A _{HVS of} the individual heater power reduction circuits may be identical for low and high load switching patterns during the first drying section, but for example the number N _HVS and / or the frequency f _{HVS of} the heater power reduction circuits may be varied. It should be noted that the first drying section at low load is usually shorter, so has a lower total time than at high load. For example, it is preferable that the frequency f _{HVS of} the _{heater power reduction circuits} in the first drying _section remains constant at a lower load _{map pattern} M ₁ , whereas it increases at a higher load _{map pattern} M ₁ , thus decreasing the time intervals between the individual _{heater power reduction circuits} at high load ,

By these measures, it is possible that the washing temperature can be kept constant during the first drying section. Thus, an optimal drying process can be achieved.

It is particularly preferred that the duration t _{HVS of} a single _{Heizleistungsverringerungsschaltung} HVS in the circuit _pattern M _1gering for a lower load state L _low during the first drying section is a maximum of 20s. In this way, the temperature of the laundry at low load can be kept very good constant. Advantageously, in such a circuit _pattern M _1, the magnitude A _{HVS of} a single _{heater power reduction} circuit is 10% ± 2% of the maximum possible _heater total H _ges , with the circuit _pattern M ₁ preferably consisting of a plurality of such identical _{heater power reduction} circuits.

In a further preferred embodiment of the method according to the invention, the dryer has a variable-speed drive motor, which drives the drum, wherein in the cooling phase at least temporarily a throttling of the rotational speed n of the drive motor takes place. Variable speed drive motor herein means that the speed of the drive motor during the process of the invention, i. of the drying process, can be varied. Cooling phase is understood to mean the phase of the drying process which follows the second drying section and during which the heating is usually switched off. A throttling of the rotational speed of the variable-speed drive motor causes a reduction in the rotational speed of the drum in the method according to the invention.

The throttling takes place during the cooling phase at least temporarily, preferably the throttling takes place from below a certain threshold temperature during the cooling phase, very particularly preferably the throttling sets in at 70 ° C, wherein the sensor temperature correlates as possible with the laundry temperature. The corresponding temperature sensor is preferably arranged on the drum outlet. For example, the temperature sensor may be an NTC temperature sensor, but according to the invention there are no limits to the type of temperature sensor.

The engine speed n can be throttled in various ways in the context of the invention. In the simplest case, the speed n is lowered to a constant value n _cooling , which is below the average speed n _medium during the main _{drying phase} . However, it is also advantageous that the rotational speed n _{cooling of} the drive motor during the cooling phase is increasingly reduced. This means that the speed is increasingly reduced according to a so-called "ramp" over time. This reduction in speed can be gradual or continuous. Since the residual heat still present in the process air duct usually decreases more and more after the heating has been switched off, a correspondingly adapted, increasingly reduced speed could lead to the energetically best utilization of the residual heat still present at the respective time. Alternatively, changing intervals of lower and higher reduced speeds are conceivable.

In the method according to the invention, a rotational speed n of the variable-speed drive motor is preferably in a rotational speed range of> 2500 to 3500 rpm and particularly preferably in a rotational speed range of 2700 to 3200 rpm. During throttling in the cooling phase, however, the rotational speed n _{cooling of} the variable-speed drive motor is preferably in a rotational speed range from 1800 to 2500 rpm and particularly preferably in a rotational speed range from 1900 to 2200 rpm.

In this way, additional energy can be saved. Heat, which is no longer removed from the laundry at the end of the drying process, accumulates and can linger longer in the drum due to the slower drum movement. Thus, with a slower drum movement, the remaining residual heat can be used more efficiently to evaporate the remaining Endrestfeuchte.

In particular, due to the reduced drum speed of the laundry case and thus the drying result is not adversely affected because the laundry case in the drum during the cooling phase is almost not changed by a reduction of the drum speed. The fact that in the cooling phase, the laundry items are already almost dry and thus have a corresponding volume, the drum is largely filled during the cooling phase, resulting in a movement of the laundry items with the drum without laundry. Thus, a uniform loading of the laundry with the process air is guaranteed even at reduced drum speed. In general, the speed of the drum is much lower than the speed of the motor, which can be achieved by a strong reduction. This can be done, for example, 1:55, so that the drum at a speed of the engine of 2750 rev / min has a speed of 50 rev / min. When using a heavily understated operated drum, the effects of the reduced speed of the drive motor on the laundry case in the drum are comparatively low.

It is particularly preferred if the throttling of the drive motor is set as a function of the load L. Advantageously, the charge state associated with the load can be assigned a throttle pattern of the drive motor during the cooling phase. For example, at lower load, the engine can be throttled more, since at lower load a greater residual heat is present. This leads to a particularly high energy saving at low load, whereas at high loading the process is not unnecessarily delayed.

In a further preferred embodiment of the method _{according to the invention} , in each case different specific circuit _{patterns of} the heating M _1gering , M _1high , M _2gering and / or M _2high take place for different types of laundry. Different types of laundry include, for example, laundry load, which consist mainly of cotton, from various synthetic types, such as sports underwear, or from animal fibers such as wool or silk or mixed laundry load, where no type of laundry predominates. The determination of the type of laundry may be made by the user, immanent in a drying program, or determined in a suitable manner by the dryer. This has the advantage that the heating circuit pattern can be adapted even more precisely, since the size and distribution of capillaries and pores in the laundry are dependent on the type of laundry.

In addition, it is preferred that the specific circuit _{patterns of} the heating M _1gering , M _1high , M _2gering and / or M _{2high be determined} as a function of the maximum possible total _{heat output} H _{ges of} the drier. This means that, depending on the total heat output H _{ges of} the dryer, different heating circuit patterns are used even under otherwise identical conditions. For example, at a higher total heating power H _ges, the heating power during the switching pattern for reducing the heating power can be reduced more than at a lower total heating power H _tot . This is due to the fact that a high total heat _output H _ges on the one hand accelerates the drying process, which is desirable, but on the other hand there is also a greater risk of overheating. Thus, in this way, depending on the maximum possible total heating H _{ges of} the dryer, the energy savings can be optimized without negatively affecting the drying process.

The invention also relates to a dryer with a program control, a drum for items to be dried and a process air duct in which a process air blower for the transport of the process air and a heater for heating the process air, wherein the program control is set up to carry out a method, which comprises a heating phase, a first drying section, a second drying section and a cooling phase, wherein prior to the beginning of the second drying section, the load L is determined and assigned to one of at least two predetermined loading conditions L _low or L _high and during the second drying section a for the loading state L _low or L _high specific circuit _pattern M _2gering or M _2hoch the heater for heating power _reduction takes place, wherein the circuit _pattern M _2gering and M _2hoch at least in terms of the extent A _HVS or the duration t _HVS a single n Heizleistungsverringerungsschaltung HVS differ.

The dryer according to the invention can be designed as a pure dryer, but also as a washer-dryer. A washer-dryer is here understood to mean a combination appliance which has a washing function for washing laundry and a drying function for drying wet laundry. It is preferably a condensation dryer.

The dryer according to the invention preferably has a heat exchanger, which is particularly preferably an air-to-air heat exchanger. For example, the dryer on an air-to-air heat exchanger with a cooling air duct, in which a cooling air blower is arranged.

The heater of the dryer according to the invention is preferably an electric heater, which is preferably realized via an electrical resistance.

In a preferred embodiment of the dryer according to the invention, the heater has at least three heating stages. A heating level corresponds to an individually switchable heating capacity. The total heat output H _tot results, according to circuit, for example the sum of the heat outputs of all the heating steps, for example in three heating stages with the respective heating powers H _1, H ₂ and H _3: H _ges = H ₁ + H ₂ + H ₃ .

The at least three heating stages are preferably heating stages which are different from one another, since this makes possible a larger combination of switchable heating powers.

Preferably, the heating and are thus the heating stages via electrical resistors, in particular realized via heating resistors, convert the electrical energy into thermal energy. For controlling the power of the at least three heating stages, for example, a plurality of resistors or partial resistors are connected in parallel or in series.

In this way, the reduction of the heating power can be very well adapted to the respective conditions, according to the invention in particular to the loading state, and an optimized drying process is made possible.

In a further preferred embodiment of the dryer according to the invention, a temperature sensor is arranged at the outlet of the process air channel from the drum. This is preferably an NTC temperature sensor. By means of this temperature sensor, the process air temperature in the vicinity of the laundry can be determined and, if appropriate, the transition of the various phases or sections of the drying process can thus be determined.

In a further preferred embodiment, the dryer according to the invention has a variable-speed drive motor which drives the drum and the process air blower. Due to the variable speed drive motor can be reduced during the cooling phase, the speed of the drum to save more energy. In addition, in this embodiment, the same variable speed drive motor also simultaneously drives the process air blower. So even more energy savings can be achieved, since only one drive motor is used to drive the drum and the process air blower. The reduced speed of the variable speed drive motor or the process air blower during the cooling phase causes a lower process air volume flow. Thus, the laundry items are cooled more slowly, which even in the cooling phase still a significant removal of moisture from the laundry can take place and the heater can possibly be switched off earlier in the drying process. Thus, despite a slower cooling of the laundry, it is possible that the duration of the drying process is not extended altogether.

The type of variable speed drive motor used in the dryer according to the invention is not limited, as long as a variation of its speed can be achieved. However, it has proved to be particularly advantageous if the variable-speed drive motor is a brushless DC motor. In a brushless DC motor (BLDC motor), the usual mechanical commutator with brushes for power application is replaced by an electronic drive circuit. BLDC motors have a relatively high efficiency and are therefore very energy efficient. In addition, the speed of the drum or the process air blower can be set as desired without much effort by such a motor. The inertia of the rotor of BLDC motors is comparatively low, so that a good dynamic characteristic is achieved. In addition, brushless drive motors are relatively low maintenance, since there are no brushes as wearing parts. This extends the life of the drive motor and thus of the dryer. In addition, such motors can be installed in hard to reach places. In addition, in BLDC motors, the ratio of output power to size is particularly high, which allows a comparatively small footprint.

In particular, the use of a BLDC motor as a motor allows a change in the speed in a simple manner and in particular a high speed. Thus, by using a BLDC motor also a better implementation of the method according to the invention is possible. In particular, a speed n _{cooling of} the motor in the cooling phase can be set in a simple manner, which is smaller than a speed n in the main _drying phase. Preferably, the speed in the cooling phase is about 20 to 50% lower than in the main drying phase. In addition, it has been found that when using a BLDC motor under otherwise identical conditions, especially at the same speed, a higher energy efficiency compared to other electric motors is given.

Furthermore, it is preferred that the dryer according to the invention has a maximum possible total heating power H _tot of at least 2500 W. As a result, on the one hand, a rapid flow of the drying process is ensured and, on the other hand, according to the invention, a high energy saving can be achieved.

In a further embodiment, the dryer also has a display device for different states of the dryer. For this purpose, an optical display device is preferably used. The display device can provide information about the operation of the dryer, for example by issuing a text or by lighting different colored light emitting diodes, for example via the course of a method according to the invention with an optimized for the loading state heating reduction circuit of the dryer.

The invention has numerous advantages. Thus, the load-dependent circuit for reducing the heat output can achieve a significantly higher energy saving than in the case of known dryers, which resort to temperature and / or humidity values, in particular in the case of heating power reduction circuits. In particular, it has surprisingly been found that the influence of the load inherent in a greater predictive power in relation to the heating power required for the drying process. This allows more accurate statements about how long and to what extent the heat output should be reduced, and the drying process can be optimized. Thus, despite the energy savings by the method according to the invention, the drying process is not adversely affected, since a high degree of adaptation to the current conditions can be ensured. Last but not least, the reduced heating power also results in a gentler treatment of the laundry and a potential risk of fire in the dryer can be avoided.

Further details of the invention will become apparent from the following description of a non-limiting embodiment of a dryer according to the invention, in which a method according to the invention can be carried out for its operation. It is related to the 1 to 3 taken.

The 1 shows a vertical section through a dryer, which is designed as a condensation dryer, wherein the arrows indicate the flow direction of the process air. Other embodiments are conceivable.

The 2 shows a schematic temperature profile and Heizleistungsverlauf during a conventional drying process, which has no Heizleistungsverringerungsschaltungen.

The 3 shows a schematic temperature profile and Heizleistungsverlauf during a drying process according to the invention on the example of a high load L _high , according to the switching patterns M _1hoch and M _2hoch .

The in 1 illustrated dryer 1 has a drum rotatable about a horizontal axis 3 for the absorption of laundry items, not shown here, on, within which carriers 5 are attached to the movement of laundry during a drum rotation. The process air is in the process air duct 2 by means of a process air blower 6 via an air-to-air heat exchanger 14 and an electric heater 4 through the drum 3 guided. It is by the electric heater 4 heated air through the drum entrance 19 from behind, ie from a door 12 opposite side of the drum 3 through whose perforated bottom into the drum 3 directed.

After leaving the drum 3 the process air laden with moisture flows through the filling opening of the drum 3 through a lint filter 11 within a door closing the filling opening 12 , Subsequently, the process air flow in the door 12 down through the drum exit 18 in the process air duct 2 deflected and the air-to-air heat exchanger 14 passed through the cooling air in a cooling air duct 15 by means of a cooling air blower 16 can be transported. In the air-to-air heat exchanger 14 As a result of cooling, a more or less large part of the moisture taken up by the process air from the items of laundry condenses in a condensate tray 17 collected.

The control of the dryer 1 takes place via a program control 8th by the user via a control unit 7 can be regulated. Two temperature sensors 9 . 10 , a temperature sensor 9 at the drum exit 18 and a temperature sensor 10 at the drum entrance 19 , are with the program control 8th connected.

In the embodiment shown in the figure, the process air blower 6 and the drum 3 through the drive motor 13 driven. The drive motor 13 in this embodiment is a brushless DC motor (BLDC). The drum is heavily stocked, for example, in the ratio 1:55, whereas the process air blower is not stocky, but is driven by the drive motor with a speed ratio of 1: 1. The electric heater 4 is realized by heating resistors so that it has three different heating levels. For example, results from the circuit of the resistors a maximum possible total heating H _{ges of} the dryer in the amount of 3000W.

When carrying out a method according to the invention, for example, during the drying process, first the end of the heating phase is determined by the by a temperature sensor 9 and or 10 measured temperature exceeds a certain threshold. As soon as this by means of program control 8th is determined by a common method, such as a determination of the weight gain of the drum 3 , a load L of the drum 3 intended with laundry. Subsequently, the load is assigned to a stored in the program control load state, for example, at a load of up to 4 kg a "low load" L _low or at a load of about 4 kg a "high load state" L _high . Then be in the program control 8th the selected loading state L _low or L _high corresponding stored circuit _patterns for the first and second drying section selected, for example M _1gering and M _2gering at a loading state L _low of up to 4 kg or M _1hoch and M _2hoch in a loading state L _high up to 4 kg.

In accordance with these selected circuit patterns, the heater is then switched during the first and second drying sections. For example, at a low load state L _low in the first drying section corresponding to a circuit _pattern M _1, only a few heat-power _reduction circuits take place in which the total heat output H _{ges is} reduced by, for example, 10%. This is due to the corresponding heating levels of the heater 4 allows. In the second drying section, according to a circuit _pattern M _{2, fewer} heating power _reduction circuits than in the first drying section take place in which the total heating power H _{tot is} reduced by, for example, 30% each.

On the other hand, at a high load state L _high in the first drying section corresponding to a circuit _pattern M _1, more _heater power _reduction circuits take place than at a low load in the first drying section. In this case, the total _heat output H _ges, for example, each by 10%, reduced. However, the frequency f _{HVS of} these Heizleistungsverringerungsschaltungen increases during the first drying section, their time intervals are thus shortened, whereas at low load, the frequency remains the same. In the second drying _section , more heating power _{reduction circuits} also take place in accordance with a circuit _pattern M _2high , but in which the total heating power H _tot is reduced by only 10%, for example. In contrast to a corresponding circuit _pattern with low loading M ₂ , the frequency f _{HVS of} these heat-power _reduction circuits _likewise increases here, their time intervals are shortened even more than during the first drying section.

During the cooling phase, ie present when the heater 4 is switched off at the end of the drying process, also the speed of the drive motor 13 , the drum here 3 and the process air blower 6 drives, for example, from 2750 rev / min to 2000 rev / min lowered. To control these processes is the program control 8th used.

In the 2 and 3 FIG. 2 shows a schematic temperature profile and a schematic heating performance curve during a during a conventional drying process, which does not have any heating power reduction circuits (FIG. 2 ) and during a drying process according to the _{invention using} the example of a high load L _high , corresponding to the switching patterns M _1high and M _2high , ( 3 ) compared.

During a conventional drying process ( 2 ) is worked from the beginning of the drying process until the beginning of the cooling phase with a maximum possible total heating H _ges . In the cooling phase, the heating is switched off. In the drying process according to the invention ( 3 ), the Heizleistungsverlauf thereof differs at least in the second drying section, in the 3 Example shown in the first drying section. In this case, in the example of a high load L _high , in the first drying section corresponding to a circuit _pattern M _{1high, a} plurality of heat _sink circuits of equal magnitude are performed, the frequency of which increases, ie, the distances between the circuits become shorter. In the second drying _section, in turn, according to a circuit _pattern M _2high , a plurality of heat _sink circuits of the same degree are performed, the frequency of which further increases, in which in 3 As shown, the duration of the heating power reduction circuits in the second drying section also decreases.

As the corresponding schematic temperature curves in the 2 and 3 can be seen causes a drying process according to the invention ( 3 ) that the temperature during the second drying section compared to a conventional drying method ( 2 ) does not rise so much. The temperature curves relate to the temperature at the drum outlet, which usually correlates with the temperature of the laundry. The in 2 shown strong temperature increase during the second drying section can not be used optimally for drying the laundry and can thus lead to overheating. This is advantageously avoided in the method according to the invention, so that energy is saved and at the same time the laundry is spared.

LIST OF REFERENCE NUMBERS

1

 dryer

2

 Process air duct

3

 drum

4

 (Electric heating

5

 takeaway

6

 Process air fan

7

 operating unit

8th

 program control

9

 Temperature sensor at the drum exit

10

 Temperature sensor at the drum entrance

11

 lint

12

 door

13

 Variable speed drive motor; in particular BLDC motor

14

 Heat exchanger; in particular air-air heat exchanger

15

 Cooling air duct

16

 Cooling fan

17

 Drain pan

18

 drum exit

19

 drum input

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4409531 C1 [0005]
• DE 3202586 C2 [0006]
• EP 1441062 B1 [0007]
• US 6199300 B1 [0008]
• EP 0067896 A1 [0010]
• DE 112007000552 T5 [0011]
• DE 3920737 A [0012]

Claims (15)

Method for operating a dryer ( 1 ) with a program control ( 8th ), a drum ( 3 ) for laundry items to be dried and a process air duct ( 2 ), in which a process air blower ( 6 ) for the transport of process air and heating ( 4 ) for heating the process air, wherein the method comprises a heating phase, a first drying section, a second drying section and a cooling phase and before the start of the second drying section determines the load L and one of at least two predetermined loading conditions L _low or L _high , thereby characterized in that during the second drying section a for the load state L _low or L _highly specific circuit _pattern M _2gering or M _2hoch the heater for heating power _reduction takes place, wherein the circuit _pattern M _2gering and M _2hoch at least in terms of the extent A _HVS and / or the duration t _{HVS of} a single Heizleistungsverringerungsschaltung HVS differ. A method according to claim 1, characterized in that in a loading state L _low , which corresponds to a lower load, during the second drying section in the circuit _pattern M _2gering at a single _{Heizleistungsverringersschaltung} HVS, the heating power is reduced more than a single _{Heizleistungsverringersschaltung} HVS in the circuit _pattern M _{2 high} , which is associated with a loading state L _high for a higher load. A method according to claim 1 or 2, characterized in that the determination of the load L and the assignment to one of at least two predetermined loading conditions L _low or L _high before the first drying section or directly at the beginning of the first drying section. A method according to claim 3, characterized in that the determination of the load L and the assignment to one of at least two predetermined loading conditions L _low or L _high at the end of the heating phase or directly at the beginning of the first drying section. A method according to claim 3 or 4, characterized in that runs during the first drying section for the associated load state L _low or L _highly specific circuit _pattern M _1gering or M _1hoch the heater for heating power _reduction , wherein the circuit _pattern M _1gering and M _1hoch at least in terms of Extent A _HVS and / or the duration t _HVS a single Heizleistungsverringersschaltung HVS and / or the number N _HVS and / or the frequency f _HVS the Heizleistungsverringerungsschaltungen different. A method according to claim 5, characterized in that the duration t _HVS a single _{Heizleistungsverringersschaltung} HVS in the circuit _pattern M _1gering for a lower load state L _low during the first drying section is a maximum of 20s. Method according to one of claims 1 to 6, characterized in that the dryer 1 a variable speed drive motor ( 13 ), the drum ( 3 ), wherein in the cooling phase at least at times a throttling of the rotational speed n of the drive motor ( 13 ) takes place. Method according to one of claims 1 to 7, characterized in that for different types of laundry in each case different specific circuit _{patterns of} the heating M _1gering , M _1hoch , M _2gering and / or M _2hoch done. Method according to one of claims 1 to 8, characterized in that the specific circuit _{pattern of} the heating M _1gering , M _1hoch , M _2gering and / or M _2hoch depending on the maximum possible total heating H _{ges of} the dryer 1 be determined. Dryer ( 1 ) with a program control ( 8th ), a drum ( 3 ) for laundry items to be dried and a process air duct ( 2 ), in which a process air blower ( 6 ) for the transport of process air and heating ( 4 ) for heating the process air, characterized in that the program control ( 8th ) is arranged to carry out a method comprising a heating phase, a first drying section, a second drying section and a cooling phase, wherein prior to the beginning of the second drying section the load L is determined and assigned to one of at least two predetermined loading conditions L _low or L _high and during the second drying section is a _low, or L _highly specific for the loading condition L circuitry pattern M _2gering or M _2hoch the heater runs for heating reduction, wherein the circuit pattern M _2gering and M _2hoch at least in terms of the extent a _HVS or the duration t _HVS a single heating power reduction circuit HVS differ , Dryer ( 1 ) according to claim 10, characterized in that the heating ( 4 ) has at least three heat levels. Dryer ( 1 ) according to claim 10 or 11, characterized in that at the exit ( 18 ) of Process air channels ( 2 ) from the drum ( 3 ) a temperature sensor ( 9 ) is arranged. Dryer ( 1 ) according to one of claims 10 to 12, characterized in that the dryer is a variable-speed drive motor ( 13 ), the drum ( 3 ) and the process air blower ( 6 ) drives. Dryer ( 1 ) according to claim 13, characterized in that the variable-speed drive motor ( 13 ) is a brushless DC motor. Dryer ( 1 ) according to one of claims 10 to 12, characterized in that the dryer ( 1 ) has a maximum possible total heat _output H _ges of at least 2500 W.

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