EP0719885A1 - Method for controlling the drying in the domestic laundry driers - Google Patents

Abstract

A domestic tumbler drier with a fan which blows air through a heater has temp. and moisture sensors as well as a programmable electronic controller which can store measured values and process variables. At the start (t0) of the drying process the air temp. ( delta 4s) at the drum exit is measured and during a time interval (t0-t2) part or all of the heater is periodically switched ON and OFF. At the end of the start-up period (t0-t2), which covers one to three switching cycles, temp. measurements at the heater inlet ( delta 2), at the drum inlet ( delta 3) and at the drum exit ( delta 4) are used to calculate temp. differences which are stored together with the time elapsed. Temps. and laundry moisture contents are measured continuously or with a frequency of several times per second. When limiting values (A1, A2) according to previously input laundry parameters have been reached, one of several stored process sequences are fed to the controller. Pref. the controller uses a fuzzy logic processor to estimate the drying time from the temp. differentials in the start-up period and the time taken to reach a critical outlet temp. or intermediate laundry moisture content. The controller has a number of algorithms for various input conditions, e.g. different degrees of required dryness, laundry type, etc..

Description

The invention is based on a method for controlling drying processes in household tumble dryers with a laundry drum which can be rotated about an at least horizontal axis and which has an inlet air inlet and an outlet air outlet, with a blower in the air duct and a heating device in front of the inlet air inlet and with temperature and moisture sensors as well as with a memory for measured values and process sequence variants and an electronic program control device.

Such a method is known from German Offenlegungsschrift 37 03 671. The known method begins with a heating phase up to the target temperature (eg 60 ° C), during which the positive temperature gradient Δϑ / Δt is determined. The negative temperature gradient is determined in a subsequent intermediate cooling phase. Since a sufficiently precise assessment of the drying time at the beginning of the drying process is not possible, a fictitious time is initially given for the expected end of the drying process. This time specification results from previous experiences. The negative temperature gradient then allows a calculation of the expected drying time, which is still subject to uncertainties, but which can already reduce the tolerance range in which the fictitious time indication replaces the remaining time. The the Drying process also influencing parameters "type of laundry" must be communicated to the controller before the beginning of the drying process via an input by the operator. Nothing is said about the influence of the amount of the laundry item introduced into the drying process in the said publication. The further drying process is then known to be controlled under the influence of the constantly measured residual moisture. The determination of the remaining time in each case is to be continued by calculating the negative residual moisture gradient, taking into account the target residual moisture and the specified type of laundry. However, drying processes going beyond the residual moisture measurement value of, for example, 8% corresponding to "slightly moist" must then be timed, for which the remaining duration is extrapolated from the previously calculated residual moisture gradient.

Above all, the known method has a disadvantage that can be seen in the waiting for the heating phase, which lasts about 10 to 15 minutes, before a reasonably reliable value can be calculated for the remaining time of the drying process. Furthermore, the unsafe residual moisture measurement outside of a relatively safe measured value range between the limit values of approx. 30% to approx. 8% interferes. The overall reliability of the control of the drying process from the measured residual moisture values is too low. On the one hand, this is because the amount of laundry is a reliably measurable correction parameter. In addition, it is also not possible to react to several environment parameters; because the known static control method during the early phase of a drying process cannot take into account different ambient temperatures or different initial residual moisture contents and any existing one Preheat the machine using previous drying processes. For a period of about 10 to 15 minutes, both the process control and the remaining time display depend on pure estimates or uncertain experience. The measurements of the positive and negative temperature gradients carried out during this phase are also influenced by such imponderables and are subject to errors which falsify the course of the process.

The invention has for its object to use the technical possibilities of modern electronic means to determine the required drying time of a laundry filling a tumble dryer by a technically simple and inexpensive method without external influences, such as. Varying ambient temperatures or different initial residual moisture contents, the accuracy of the process sequence, the drying time determination and the remaining time display can be questioned.

This task is already solved by the method described in our older German patent application P 44 42 250.4. However, the amount of computing power required for this control process is considerable and can be replaced by stored, experience-based, recurring, standardized process flows, which can be varied depending on the physical condition of the process to be controlled, with a few parameter measurements.

The invention achieves the above-mentioned object in a new way in that the exhaust air temperature is measured at the exhaust air outlet at the start of the drying process, that during at least one period at the beginning of the drying process Part or all of the heating device is periodically switched on and off so that after a start phase, the duration of which is measured over a period of one to three heating periods, air temperature measurements are carried out at the entrance of the heating device, in front of the supply air inlet and immediately behind the exhaust air outlet and from the measured values on the one hand in the exhaust air and at the entrance of the heating device and on the other hand in the supply air and at the entrance of the heating device differences are formed and stored that process variables - such as the time actually elapsed since the program started, temperature values and humidity values of the laundry to be dried - are constantly being or at least periodically with frequencies of several times per second and when predetermined threshold values are reached as a function of the program parameters entered, the type, quantity and / or moisture of the right to start each time a call to several stored processes sequences to the memory unit for output, and processing was made in the program control unit.

The immediate measurement of the exhaust air temperature at the start time registers the existing machine system temperature, which also contains the ambient temperature of the machine due to the aspirated ambient air in the case of an exhaust air dryer. Uncertainties about such environmental parameters are therefore eliminated. In the initial period of periodic switching on and off of the heating device or a part of the air temperatures measured by it at the three locations mentioned provide information about the so-called thermal transfer function which can be formed as a quotient of an input and an output variable. The thermal input variable is the difference between the temperatures at the entrance to the heating device and at the supply air inlet Drum formed. This size is very pronounced both in a so-called exhaust air dryer, which sucks in the air from the environment and releases the exhaust air into the environment, as well as in a condensation dryer, which has a closed process air channel, but between the outlet of the drum and the entrance of the heating device has a condensation cooler. The thermal output variable represents the behavior of the heat consumer - namely the laundry item - and is formed from the differences in temperature measured at the outlet of the drum and at the inlet of the heating device and / or at the outlet of the drum and at the inlet of the drum. This thermal transfer function, which is formed from the thermal input and output variables, automatically takes into account all ambient conditions, such as fluctuations in the mains voltage, type and quantity of laundry as well as initial residual moisture, the individual measured values of which influence the thermal input variable and the thermal output variable. For example, the thermal output variable increases faster, the greater the heating output - depending on the mains voltage - and the smaller the amount of laundry and the initial residual moisture. This thermal transfer function permits a first assessment of the expected program duration, which can replace an empirical value for the drying duration displayed during the first period of the drying process.

In the course of the drying process, measured values of the temperatures or their differences, measured moisture values and the time actually elapsed repeatedly intervene in the drying process in that they call up stored process sequences on the one hand and on the other hand these process sequences using the parameter measurement values normally available from experience differing actual measured values vary. These variations are also printed out in changed and time to be corrected displays.

In a particularly advantageous manner, the method according to the invention can be further developed in that, as a process variable, the actually elapsed time from the start of the program until an average measured value of the exhaust air temperature is reached during the quasi-stationary phase, in which the heat input by the heating device coincides with that Heat removal by evaporation of the moisture from the laundry is roughly balanced. The said point in time is best suited to make a decision as to which of the stored process sequences is suitable for the further treatment of the laundry item. At this point in time, the relevant decision data is available, i.e. the parameters about the amount of laundry and initial residual moisture, about the system and ambient temperature, about the heating power actually introduced and the remaining time calculated differently due to initial measurement inaccuracies compared to the actually elapsed time. At this point in time there is a first possibility of correction by observing the rise in the exhaust air temperature up to the quasi-stationary phase.

Advantageously, the actually elapsed time from the start of the program until an average measured value for a predetermined residual moisture content of the laundry is reached can be registered and stored as a process variable, which can be classified as measurable for the first time in the course of the drying process for physical reasons. All residual moisture values averaged over this Measured value of approx. 30% can only be determined with uncertainty and therefore cannot be used for an unequivocal control of the drying process. However, since the temperatures at the above-mentioned locations are periodically monitored again and again until the actual elapsed time until this residual moisture is reached for the first time, the drying process can continue to run smoothly and unchanged, provided there are no disturbances causing a temperature deviation. After a phase of exclusive subtraction of time steps since reaching the quasi-stationary phase, reaching the averaged measured value of approx. 30% for the residual moisture of the laundry item now also allows the remaining time values displayed up to this point to be checked again. The time of measurement when the residual moisture of 30% has been reached since the program started gives further information about the composition of the laundry item with regard to the types of fabric. For example, moisture is more difficult to evaporate from a thick cotton fabric made from thick threads than from a thinner and lighter cotton fabric. To a lesser extent, the quasi-stationary phase with a large proportion of large items of laundry in the item of laundry is lengthened in comparison with smaller items of laundry, which fall apart more easily and more frequently when the moving laundry drum falls around and are exposed to the hot air flow than large items of laundry. Depending on this, the measured value of approx. 30% for the residual moisture in the item of laundry is reached sooner or later. A new process sequence following the previous process sequence is therefore only started earlier or later.

The new process section runs until an average measured value (of, for example, 20%) is reached for a predetermined residual moisture in the laundry, which defines the term "lack of moisture" corresponds. Then the time that has actually elapsed since reaching the measured value for the residual moisture that can be measured for the first time (RF = 30%) is registered and stored. At this newly determined point in time, a new process section can be initiated.

Advantageously, the drying process according to the invention is logically controlled by a further process variable, which characterizes the time actually elapsed from reaching the measured value for the residual moisture that can be measured for the first time until an average value (of 13%, for example) has been reached for a predetermined residual moisture of the laundry, which one Definition of the term "iron damp" corresponds. This size is also registered and saved. As a result, the drying process can be corrected in a further process section if a misjudgment of the previous process sections has resulted.

It makes sense to also be able to influence the last process section, which can be determined by definable facts, by means of a process variable, from the time actually elapsed since the measured value was reached for the residual moisture that can be measured for the first time until an average measured value (e.g. 8%) is reached for a predetermined residual moisture the laundry is determined, which corresponds to a definition of the term "slightly dry". This measured value can also be registered and saved. It is also suitable for correcting the assigned process section in the same way as in the previous process sections.

As an essential development of the invention, it has been found that mean values for the temperature and humidity measured values are formed and stored from a limited number of individual measured values that have been recurring periodically since a start signal. Experience has shown that the temperature and humidity measurements change within a short period of time, so that a single measurement may could give a wrong picture of the current physical state. For example, temperature values could be recorded 60 times per second. For example, four measurements, which can be stochastically distributed over a short time span of a maximum of 4 seconds, provide a good basis for an averaging of the measured values which at least approximates the current physical state. The specified period of time for the measuring section should not be longer than four seconds, as otherwise process-related errors can result. The minimum time span at 60 measurements per second can therefore be around 67 milliseconds in the case of immediately successive measurements. The above-mentioned differences are advantageously formed from the temperature measurement mean values and stored.

To increase the measuring accuracy, it is advantageous if, in the case of a storage device which can only store whole numbers of the measured values, the measured values of the temperatures of the exhaust air and at the entrance of the heating device are doubled before the difference is formed. With the doubling, fractions of the measured values can double to the next higher odd integer, so that inaccuracies when omitting decimal fractions are reduced.

To call up stored process sequences, it is particularly advantageous if, according to a further development of the invention, when control values differ when a measured value is reached, a fuzzy processor is given, the fuzzy processor calls up a predetermined process sequence depending on the content of the respective control signal and outputs a value for the duration of the drying process. Different, standardized process sequences can be stored for the individual process sections, which can be varied if necessary by continuously measured parameters. When calling up such a process sequence, a value for the duration of the drying process or for the remaining time (duration of the drying process minus the time that has actually elapsed since the program was started) can be output at the same time.

The accuracy of the drying process can be further increased if, according to an advantageous further development of the invention, the threshold values of measurable process parameters, here the temperature differences, are changed in a targeted manner as a function of an automatically determined or entered value for the loading quantity. Load values to be entered depend on the ability of the operator to make an accurate estimate. It has already been explained above that the temperature profiles observed in the start-up phase of the drying process allow a conclusion to be drawn about the load quantity, which can be more precise than the operator's estimate. It is therefore advantageous if a value for the load quantity determined in this way influences the threshold value of the temperature difference to be observed in each case.

It is also advantageous if the fuzzy processor calculates a remaining time depending on the process run called and the value for the duration of the drying process, as well as input parameters for the type and / or amount of laundry and the drying target, and outputs it to an output unit.

In addition, the fuzzy processor can advantageously change the threshold values of the residual moisture at which the time is registered, depending on an automatically determined or entered value for the loading quantity. Since the drying behavior of laundry items of different sizes runs differently, the starting condition for the respective process sequence, namely the reaching of the threshold value of the residual moisture, can be set up to be variable while maintaining the stored process sequences for the individual process sections. When the remaining time is displayed, it is particularly advantageous if the remaining time that has been output is decrementally corrected by subtracting the time progress until it is recalculated on the basis of new control signals and measured values. Because of the relatively high level of inaccuracy and the length of the drying process to be processed, it is reasonable to set the decrements to an absolute remaining time of approximately 30 minutes to 5 minutes, while towards the end (from around 30 minutes remaining time) the calculation accuracy and the brevity of the remaining ones Justify remaining time decrements of one minute. Alternatively, depending on the correction requirement, the individual decrements can be shorter or longer than the intended decrements. In the case of a calculated correction that required a larger remaining time display than the actual display, it is advantageous to avoid irritation to the operator, the previous remaining time display to be left until the correction value is at least lower than the remaining time currently displayed by the intended decrement.

It is particularly advantageous for the handling of the household clothes dryer if the fuzzy processor saves empirical values for the composition of the respective drying process and for its total duration from the drying processes that have previously taken place, depending on the program parameters entered. Then, at the start of the program, an empirical value depending on the type and / or amount of laundry entered and the drying goal entered can be output for the entire duration of the program. Since the experiences over a longer period, i.e. Over several similar drying processes, which can result in an ever greater accuracy for the duration of the respective drying process, the chance of displaying an appropriate program execution time at the beginning of the drying process is greater with increasing experience of the fuzzy processor.

It is therefore particularly advantageous if the empirical value is compared with programs that subsequently run with similar program parameters based on the calculations of the fuzzy processor, the program expiration time period is corrected, and the corrected empirical value is exchanged for the previous empirical value in the memory. For this purpose, it is expedient if, in order to correct the empirical value, this and a certain number of subsequently determined program sequence time periods are averaged.

Fig. 1

einen schematischen Seitendurchblick durch einen erfindungsgemäß ausgestatteten Wäschetrockner,

Fig. 2

ein Diagramm der Leistungsstufen der Heizeinrichtung über die Zeit,

Fig. 3

ein Diagramm der Temperaturen an den drei in Fig. 1 angegebenen Meßpunkten über die Zeit und

Fig. 4

ein Diagramm des Restfeuchte-Verhaltens eines zu trocknenden Wäschepostens über der Zeit.

The method according to the invention is explained below using an exemplary embodiment shown in the drawing. Show it

Fig. 1

a schematic side view through a clothes dryer equipped according to the invention,

Fig. 2

a diagram of the power levels of the heating device over time,

Fig. 3

a diagram of the temperatures at the three measuring points indicated in Fig. 1 over time and

Fig. 4

a diagram of the residual moisture behavior of a laundry item to be dried over time.

The residual moisture values given for the exemplary embodiment shown relate to a basis of 0% relative humidity, in which an absolute water content is contained in any fabric at a temperature of 20 ° C. and 65% relative humidity of the ambient air.

The clothes dryer in FIG. 1 has a program control device 1 in the upper part, which can be adjusted by an operating handle 6 and - not shown - contains a fuzzy processor control. At the lower rear of the tumble dryer there is an inlet air opening 7 which is connected to the inlet 11 of the laundry drum 10 via a blower 8, the inlet air duct 9 and the heating device 5. The outlet 12 of the laundry drum 10 is connected via the pot 13 of the loading door 14 and the exhaust air duct 15 to the exhaust air outlet 16 on the front of the tumble dryer.

To close the dry air circuit via a condenser 17, which is only shown in broken lines here, the fan 8 and the manifold 18 of the exhaust air duct 15 have to be turned over and connected to the respective connections 19 and 20 of the condenser 17.

In the flow direction in front of the heating device 5, which is designed to be switchable in two heating stages, a fresh air temperature sensor 2 is installed in the supply air duct 9, which, in the case of the configuration as an exhaust air dryer, measures the temperature of the ambient air drawn in. If the tumble dryer is equipped as a condensation dryer, this temperature sensor measures the outlet air of the condenser 17, which may have residual heat. A supply air temperature sensor is arranged in the supply air duct between the heating device 5 and the inlet 11 of the laundry drum 10. It measures the temperature of the supply air heated by the heating device 5. In the flow direction behind the outlet 12 of the laundry drum 10, the temperature sensor 4 is arranged in the exhaust air duct 15 and measures the temperature of the exhaust air.

The diagram shown in FIG. 2 shows that the heating device 5 is periodically switched back and forth to the full and half the heating output at the beginning of the drying process. This is preferably done twice during the first four minutes. This creates a in the diagram of Fig. 3 clearly visible up and down swinging measured at the temperature sensor 3 the temperature θ ₃ on the inlet air of the washing drum 10. From time t ₂ = 4 minutes is then heated at full heating power permanently to the temperature sensor 3 a impermissibly high temperature, then what is not shown here is to switch back and forth between full and half heating capacity depending on whether the maximum or minimum temperature is reached or fallen below.

At the start time t _{0 of} the drying process, the exhaust air temperature ϑ _{4S is} measured at temperature sensor 4 in the exhaust air outlet. This temperature represents the initial state of the tumble dryer and also takes into account the temperature of the ambient air sucked into the supply air opening 7. Since the heating device 5 is still cold at this point in time, the measured temperature relates only to the state of the surroundings and any preheating of the tumble dryer, if any, from a drying process that had previously taken place. At the start time t ₀ , the heating device 5 is also switched to full heating power and the drives, not shown, for the blower 8 and the laundry drum 10.

When starting from the cold state of the tumble dryer, the amount of heat introduced by the heating device 5 must first heat up the parts of the tumble dryer which come into contact with the warm air flow together with the items of laundry. In the example of FIG. 3, the temperature ϑ ₃ on the transmitter 3 in the supply air inlet 11 reaches about 75 ° after one minute, while the temperature ϑ ₄ on the transmitter 4 in the exhaust air outlet 12 only reaches about 30 °. In the next minute interval, the heating device 5 is switched back to half the heating output, as a result of which the temperatures ϑ3 and ϑ ₄ drop again, ϑ ₃ to about 55 ° and ^ϑ 4 to about 25 °. With the second full switch-on period of the heating device 5 in the third minute interval, the temperature ϑ ₃₁ reaches about 80 ° at the time t ₁ , while ϑ _{41 reaches} about 35 °. The temperature ϑ ₂₁ at the sensor 2 before the input of the heating device 5 is still assumed to be 20 ° C at this time, that is the temperature the sucked in ambient air. In the course of the drying process, of course, the temperature of the ambient air also rises, because the tumble dryer also releases at least part of its heat quantity into the installation room. This even applies to exhaust air dryers in which the ϑ ₄ warm exhaust air is led outside through an exhaust air hose. Leakage losses and feedback effects mean that even in this way the ambient air is heated. However, the heating of the ambient air is considerably higher in a so-called condensation dryer, the condenser 17 of which is cooled by cooling air, which takes the amount of heat from the condenser and transfers it to the installation room.

Darin bedeuten

t_Rest

die anzuzeigende Restzeit bis zum gewählten Trocknungsziel,

t_Fuzzyges

die vom Fuzzy-Prozessor aufgrund der im Zeitpunkt des Aufrufes vorliegenden Variablen berechnete Gesamttrocknungszeit,

f₁

ein trocknungszielabhängiger Korrekturfaktor als Prozentsatz für die unterschiedlichen Trocknungsziele "mangelfeucht", "bügelfeucht" für Baumwolle, "bügelfeucht" für pflegeleichte Textilien, "leicht trocken" für Baumwolle und "leicht trocken" für pflegeleichte Textilien.

t_Plz

Die aktuelle abgelaufene Prozeßlaufzeit und

t₁

eine Konstante für die Trocknungsziele "sehr trocken" und "extra trocken".

At time t1, at which temperatures ϑ ₂₁ , ϑ ₄₁ and ϑ _{31 are} measured and averaged, the differences ϑ _4-2 = ϑ ₄₁ - ϑ ₂₁ , ϑ _3-4 = ϑ ₃₁ - ϑ ₄₁ and ϑ _{3 -2} = ϑ ₃₁ - ϑ ₂₁ formed. The fuzzy processor calculates a total drying time from the now available variables, the start temperature ϑ _4s , the temperature differences ϑ _4-2 , bis _3-4 and ϑ _3-2 as well as the elapsed time for t ₁ = 3 minutes, which together with an algorithm 1, which is now called up by call A1, is used for the preceding process section to correct the previously estimated residual display. The remaining time to be displayed is calculated using the following equation. $${\text{t}}_{\text{rest}}{\text{= t}}_{\text{Fuzzyges}}{\text{xf}}_{\text{1}}{\text{-t}}_{\text{Postcode}}{\text{+ <figure-callout id="1" label="t" filenames="imgf0002.png" state="{{state}}">t</figure-callout>}}_{\text{1}}$$

Mean in it

t _rest

the remaining time to be displayed until the selected drying target,

t _fuzzyges

the total drying time calculated by the fuzzy processor based on the variables available at the time of the call,

f ₁

a correction factor depending on the drying target as a percentage for the different drying targets "poorly damp", "iron-damp" for cotton, "iron-moist" for easy-care textiles, "slightly dry" for cotton and "slightly dry" for easy-care textiles.

t _zip

The current elapsed process time and

t ₁

a constant for the "very dry" and "extra dry" drying goals.

This type of calculation is used together with the algorithms for calls A1, A2 and A3.

For the call A2, a threshold value of, for example, 60 ° C. is activated from the time t2 = 4 minutes elapsed process time), which must be reached by the temperature ϑ ₄ so that the fuzzy algorithm 2 is called. To correct the remaining time to be displayed, the time t _{60 that} has actually elapsed since the start of the program for the first time reaching the average measured value of the exhaust air temperature ϑ ₄₂ = 60 ° is registered, stored and used for correction. At this exhaust air temperature ϑ ₄₂ = 60 ° the so-called quasi-stationary phase of the drying process begins. During this phase, the heat input through the heating device remains approximately the same as the heat removal through evaporation of the moisture from the laundry. At the end of the quasi-stationary Phase, the temperature ϑ _{4 of} the exhaust air rises above 60 °. To protect the laundry, certain threshold values of the exhaust air temperature must not be exceeded here, for which the heating device 5 may be switched back to half the heating output or switched off entirely.

In the course of the quasi-stationary phase of the drying process, a device (not shown) for direct measurement of the residual moisture present in the laundry, which works according to the conductivity measurement method, is activated. As soon as this conductance measuring device, which is queried several times per second like the temperature sensors and its measured value is averaged accordingly, has determined the residual moisture value RF = 30%, the time that has actually elapsed until this mean value is reached for the first time is recorded and saved and when calling 3 Algorithm 3 in the fuzzy processor is used to correct the remaining time display (equation 1).

Darin bedeuten

t_Rest

die Restzeit bis zum gewählten Trocknungsziel,

t_Fuzzyrest

die unter Anwendung der vorliegenden Variablen durch den Fuzzy-Prozessor berechnete Restzeit bis zum Erreichen einer Restfeuchte von 8 %,

f₂

ein trocknungszielabhängiger Korrekturfaktor,

t₁

eine Kontante für die Trocknungsziele "sehr trocken" und "extra trocken".

The following equation 2 applies to the calculation of the remaining times from calls A4 to A6: $${\text{t}}_{\text{rest}}{\text{= t}}_{\text{Fuzzy residue}}{\text{x (1-f}}_{\text{2nd}}{\text{) + <figure-callout id="1" label="t" filenames="imgf0002.png" state="{{state}}">t</figure-callout>}}_{\text{1}}\text{+8 min}$$

Mean in it

t _rest

the remaining time until the selected drying target,

t _Fuzzyrest

the remaining time calculated by the fuzzy processor using the available variables until a residual moisture of 8% is reached,

f ₂

a correction factor dependent on the drying target,

t ₁

a constant for the drying goals "very dry" and "extra dry".

Since the time course of the decrease in residual moisture in the range between 30% and 8% can be assumed to be a straight line with sufficient accuracy, the same equation 2 applies to the drying sections from call A4.

In a memory area assigned to the fuzzy processor, a possibility is expediently provided for storing further correction factors which are based on the input variables ϑ _4s , ϑ ₂₁ , ϑ ₃₁ , ϑ ₄₁ , ϑ ₄₂ , t ₆₀ , t _RF30 , t _RF20 , t _RF13 and t _RF8 or the output variables t fuzzyges and t _rest as well as t _{fuzzy residue} can act.

When correcting the display, proceed as follows: After the respective algorithm calls to the fuzzy processor, the remaining time is calculated as described and the results are displayed. From this point in time until the next call, the remaining displays above 30 minutes are decremented in 5-minute increments, with the display being an integer with five divisible values. When a remaining time display of 30 minutes is reached, the display is decremented in one-minute steps. If only two digits are provided for displaying the remaining time, the number 99 is displayed for remaining times greater than 95 minutes and documented with a flashing decimal point that the time is estimated and is over 99 minutes.

If there is a deviation from the currently displayed remaining time when reassessing the respective remaining time or when changing to the time-controlled section after reaching the residual moisture RF = 0%, the display jumps to a new, smaller display value if the display is larger than that remaining time or the displayed value remains until the display and forecast match, if the display is smaller than the calculated remaining time. Then, however, the right decimal point flashes as an indication of the current inaccuracy.

To achieve the drying goals "very dry" and "extra dry", a time control is connected due to the assumed straightness of the remaining drying process. The display is decremented to 0 during these time-controlled program sections. At the end of the cooling phase, which is still included in the remaining time calculation, the remaining time display is switched off. This makes it easy to see that the drying program has ended. This is followed by the so-called anti-crease phase, which is no longer part of the actual drying process.

Claims (16)

Method for controlling drying processes in household tumble dryers with a laundry drum rotatable about an at least horizontal axis, which has an inlet air inlet and an outlet air outlet, with a blower in the air duct and a heating device in front of the inlet air inlet and with temperature and humidity sensors and with a memory for measured values and process sequence variants and an electronic program control device, characterized in that at the start time (t ₀ ) of the drying process the exhaust air temperature (ϑ _4S ) at the exhaust air outlet (12) (transmitter 4) is measured such that during at least one period (t0 to t2 ) at the beginning of the drying process, part or all of the heating device (5) is periodically switched on and off, that after a start phase (t0 to t2), the duration of which is measured over the period of one to three heating periods, air temperature measurements at the entrance (Encoder 2) of the heating device (5), in front of the supply air inlet (11) (G eber 3) and immediately behind the exhaust air outlet (12) (encoder 4) and from the measured values (ϑ ₄ , ϑ ₃ , ϑ ₂ ) in the exhaust air, at the entrance of the heating device and (ϑ ₃ ; ϑ ₂ ) Differences (ϑ _4-2 , ϑ _3-4 , ϑ _3-2 ) are formed and saved in the supply air, in addition that process variables - such as the actually elapsed time (t) since the program started, temperature values (ϑ) and humidity values ( RF) of the laundry to be dried - measured continuously or at least periodically with frequencies of several times per second and when reaching predetermined threshold values depending on the program parameters entered, the type and amount of laundry and / or initial residual moisture relating to a call (A1 to A6) of several stored process flows to the storage unit for output to and processing in the program control unit (1). Method according to Claim 1, characterized in that the actually elapsed time (t60) from the start of the program until an average measured value (ϑ ₄₂ ) of the exhaust air temperature (eg 60 ° C) is reached and stored during the quasi-stationary phase is recorded as a process variable which the heat input by the heating device roughly balances with the heat removal by evaporation of the moisture from the laundry. A method according to claim 1, characterized in that as a process variable the actually elapsed time (t _RF30 ) from the start of the program until an average measured value (30%) is reached for a predetermined residual moisture (RF) of the laundry, which is considered to be the first time in the course of the drying process is classified as measurable for physical reasons, registered and stored. A method according to claim 1, characterized in that as a process variable the actually elapsed time (tRF20) since reaching the measured value (30%) for the residual moisture (RF) which can be measured for the first time until an average measured value (20%) is reached for a predetermined time Residual moisture (RF) of the laundry, which corresponds to a definition of the term "insufficiently moist", is registered and stored. A method according to claim 1, characterized in that as a process variable the actually elapsed time (t _RF13 ) since reaching the measured value (30%) for the residual moisture (RF) which can be measured for the first time until an average measured value (13%) is reached for a first time predetermined residual moisture (RF) of the laundry, which corresponds to a definition of the term “iron-damp”, is registered and stored. A method according to claim 1, characterized in that as a process variable the actually elapsed time (t _RF8 ) from reaching the measured value (30%) for the residual moisture (RF) which can be measured for the first time until an average measured value (8%) is reached for a first time predetermined residual moisture (RF) of the laundry, which corresponds to a definition of the term "slightly dry", is registered and stored. Method according to one or more of Claims 1 to 6, characterized in that mean values for the temperature and humidity measured values are formed and stored from a limited number of individual measured values which have been recurring periodically since a start signal. Method according to Claim 7, characterized in that the difference is formed from the mean temperature measurement values and stored. Method according to Claim 8, characterized in that the measured values of the temperatures (ϑ ₄ , ϑ ₂ ) in the exhaust air and at the entrance to the heating device (5) are doubled before the difference is formed. Method according to one of Claims 7 to 9, characterized in that, when measured values are reached in each case, different control signals are sent to a fuzzy processor, the fuzzy processor calls up a predetermined process sequence depending on the content of the respective control signal and a value for the duration (t _fuzzyges , t _rest or t _{fuzzy rest} ) of the drying process. Method according to Claim 10, characterized in that the fuzzy processor specifically changes the threshold values of the temperature difference as a function of an automatically determined or entered value for the load quantity. A method according to claim 10 or 11, characterized in that the fuzzy processor, depending on an automatically determined or entered value for the loading quantity, the threshold values (30%, 20%, 13%, 8%) of the residual moisture (RF) at which the time registrations are made, specifically changed. Method according to one of claims 10 to 12, characterized in that the time remaining (t _rest ) until it is recalculated is corrected decrementally on the basis of new control signals and measured values by subtracting the time progress. Method according to one of claims 10 to 13, characterized in that at the start (S) of the program _{sequence, an empirical value} which is dependent on the type and / or quantity of laundry entered and the drying _{target entered is} output for the entire program _sequence duration (t _fuzzyges ) . Method according to Claim 14, characterized in that the empirical value is compared with programs which subsequently run with similar program parameters on the basis of the calculations of the fuzzy processor and the program expiry time periods are corrected, and the corrected empirical value is exchanged for the previous empirical value in the memory. A method according to claim 15, characterized in that to correct the empirical value, this and a certain number of subsequently determined program execution time periods are averaged.

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