Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F34/00—Details of control systems for washing machines, washer-dryers or laundry dryers
  • D06F34/14—Arrangements for detecting or measuring specific parameters
  • D06F34/18—Condition of the laundry, e.g. nature or weight
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/02—Characteristics of laundry or load
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/02—Characteristics of laundry or load
  • D06F2103/04—Quantity, e.g. weight or variation of weight
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/02—Characteristics of laundry or load
  • D06F2103/06—Type or material
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/02—Characteristics of laundry or load
  • D06F2103/08—Humidity
  • D06F2103/10—Humidity expressed as capacitance or resistance
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/28—Air properties
  • D06F2103/34—Humidity
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/28—Air properties
  • D06F2103/36—Flow or velocity
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/38—Time, e.g. duration
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/44—Current or voltage
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2103/00—Parameters monitored or detected for the control of domestic laundry washing machines, washer-dryers or laundry dryers
  • D06F2103/44—Current or voltage
  • D06F2103/46—Current or voltage of the motor driving the drum
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/12—Humidity or dryness of laundry
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/16—Air properties
  • D06F2105/24—Flow or velocity
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/26—Heat pumps
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/28—Electric heating
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/30—Blowers
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/38—Conditioning or finishing, e.g. control of perfume injection
  • D06F2105/40—Conditioning or finishing, e.g. control of perfume injection using water or steam
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/46—Drum speed; Actuation of motors, e.g. starting or interrupting
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/46—Drum speed; Actuation of motors, e.g. starting or interrupting
  • D06F2105/48—Drum speed
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F2105/00—Systems or parameters controlled or affected by the control systems of washing machines, washer-dryers or laundry dryers
  • D06F2105/56—Remaining operation time; Remaining operational cycles
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F39/00—Details of washing machines not specific to a single type of machines covered by groups D06F9/00 - D06F27/00 
  • D06F39/40—Steam generating arrangements
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F58/00—Domestic laundry dryers
  • D06F58/20—General details of domestic laundry dryers 
  • D06F58/203—Laundry conditioning arrangements
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F58/00—Domestic laundry dryers
  • D06F58/32—Control of operations performed in domestic laundry dryers 
  • D06F58/34—Control of operations performed in domestic laundry dryers  characterised by the purpose or target of the control
  • D06F58/36—Control of operational steps, e.g. for optimisation or improvement of operational steps depending on the condition of the laundry
  • D06F58/38—Control of operational steps, e.g. for optimisation or improvement of operational steps depending on the condition of the laundry of drying, e.g. to achieve the target humidity

Definitions

• the invention relates to a laundry treatment apparatus, in particular a laundry dryer, having a laundry storing compartment and a laundry water content sensor for detecting the amount of water contained in the laundry stored in the laundry storing compartment.
• GB 1 232 839 B discloses control circuits for a fabric drying machine using the reflection 5 pattern of HF electromagnetic waves, in particular microwave radiation, to prevent
• the sensor is arranged for observing the interior of the laundry drum and for detecting signals corresponding to e.g. vibrations of the drum or the machine, rotation speed of the drum, the amount of laundry loaded, or the water level in the drum.
• the sensor may also provide indirect information about the motor, pumps, mountings, shock absorbers and/or 5 laundry or machine temperature. Furthermore, the sensor is proposed for sensing the grade of impurity of the water in the drum.
• DE 101 63 199 A 1 teaches a laundry treatment apparatus with a sensor for detecting the humidity of laundry in the laundry drum, wherein the sensor comprises a microwave o resonator and a probe head for feeding an electromagnetic stray field into the drum.
• measurement circuitry is arranged for determining characteristic parameters of the resonator which are dependent on the dielectric properties of surrounding material, i.e. laundry in the drum. From the measured parameters the humidity of the laundry can be determined.
• WO 2013/088830 Al discloses a laundry dryer for drying laundry stored in a rotating drum, wherein the dryer is equipped with an electromagnetic wave generation unit, an electromagnetic wave detection unit, and a computation unit.
• the electromagnetic wave generation unit emits electromagnetic waves at frequencies in the range of 100 GHz - 120 THz into the interior of the drum.
• the electromagnetic wave detection unit detects electromagnetic waves emitted by the generation unit that have passed through the drum. 5
• the computation unit determines the laundry drying state based on a signal output from the detection unit.
• It is an object of the invention to provide a laundry treatment apparatus comprising a laundry water content sensor adapted to detect the amount of water contained in the o laundry to be treated, in which the laundry treatment is further improved.
• a laundry treatment apparatus comprises a casing, a laundry storing compartment within said casing for receiving the laundry to be treated, a contactless water content sensor, and a control unit.
• the laundry treatment apparatus may be a laundry dryer, a washing machine, a washer dryer, or the like.
• the contactless water content sensor is adapted to detect the amount of water contained in the o laundry stored in the storing compartment.
• the contactless water content sensor may
• the control unit is adapted to receive a signal from the laundry water content sensor and serves for controlling the 5 operation of the laundry treatment apparatus.
• the control unit is furthermore adapted to select or adjust one or more of the following parameters in dependency of the laundry water content sensor signal: estimated time to cycle end, drying air flow rate, cooling air flow, drum rotation speed during tumbling, parameters of heat pump compressor operation, heating power, and/or parameters of a self-cleaning operation for removing fluff from a o drying air fluff filter of the apparatus by flushing the filter with a liquid, preferably water and highly preferably water condensed during the laundry drying process.
• the laundry storing compartment preferably is or comprises a laundry drum, preferably a front loading drum 5
• cycle in the context of laundry treatment operation is used to denote a laundry treatment program or program sub-routine of the laundry treatment apparatus, such as tumbling, spinning, drying, steaming and/or self-cleaning.
• the control unit uses the signal received from the laundry water content sensor in order to select and/or adjust the estimated time to cycle end, i.e. the time until the current or a subsequent laundry treatment operation cycle will be finished.
• the obtained estimated time to cycle end can be used for controlling the machine operation, e.g. the 5 rotation speed and/or acceleration and/or deceleration of a laundry drum, a steam
• the estimated time to cycle end may be used to provide information to the user, e.g. display the remaining time required for laundry treatment on a display unit.
• the signal received from the laundry water content sensor is additionally or alternatively used by the control unit for selecting and/or adjusting the flow rate of drying air that is guided through the laundry storing compartment, in particular during laundry drying operations.
• a fan or drying air blower may be provided for moving said drying air and for controlling its flow rate.
• the drying air is cooled and/or dehumidified in a heat exchanger by means of a cooling air stream (e.g. in a (cross-flow or counter-flow) air/air heat exchanger).
• a cooling air stream e.g. in a (cross-flow or counter-flow) air/air heat exchanger
• the control unit may be arranged for selecting and/or adjusting the cooling air flow in dependency of the o laundry water content.
• the 'cooling air stream' is a flow of cooling air drawn into the cabinet of the laundry treatment apparatus from outside and the cooling air having undergone heat exchange is exhausted to the outside of the apparatus cabinet.
• the heat exchanger is a drying air / ambient air heat exchanger, for example of the cross flow type.
• Such cooling air is used for example in case 5 the laundry treatment apparatus is a condenser-type dryer or washer-dryer with a closed process loop and a condensate collector that collects the condensate condensed out of the drying air at the heat exchanger.
• the 'cooling air stream' is a flow of ambient (from outside cabinet) air flowing over the compressor and/or auxiliary heat exchanger used in the heat-pump system of a heat-pump dryer or washer- o dryer.
• the laundry water content sensor signal may serve for adjusting and/or selecting the rotation speed of a laundry drum, in particular during tumbling.
• said laundry drum is rotatable and may be part of 5 the laundry storing compartment, e.g. with the laundry storing compartment comprising a circumferential wall defined by said rotatable drum, a back wall, and/or a front wall opposite to the back wall with a front loading opening for loading laundry into the laundry storing compartment.
• the laundry water content sensor signal may serve in addition or alternatively for adjusting and/or selecting operation parameters of a heat pump
• Such heat pump compressor is part of a heat pump system that may be
• the heat pump compressor operation parameters to be selected and/or adjusted may include one or more of: the compressor speed; the temporal profile of the o compressor speed and/or the input power provided to the compressor. By selecting and/or adjusting such parameters it is possible to control, e.g., the air humidity or dehumidifying degree of the drying air, the temperature of the drying air, the amount of water extracted from the drying air, the total power and/or energy consumption of the laundry treatment apparatus.
• the signal received from the laundry water content sensor is additionally or alternatively used by the control unit for selecting and/or adjusting the heating power used for drying laundry.
• the control unit for selecting and/or adjusting the heating power used for drying laundry.
• the laundry water content sensor signal may serve for selecting and/or adjusting parameters of self-cleaning operations carried out by the 5 laundry treatment apparatus.
• the self-cleaning operations are for removing fluff from a drying air fluff filter of the apparatus by flushing the filter with a liquid, preferably water and highly preferably water condensed during the laundry drying process.
• the laundry water content sensor signal may be used to estimate of the laundry water content at the beginning of, e.g., a laundry drying cycle. This can provide a o value of the whole amount of water removed and/or to be removed from the laundry.
• the so-obtained knowledge about the total amount of water removed and/or to be removed can implicitly provide knowledge about the amount of water available for self-cleaning cycles, in particular when the condensation efficiency of the laundry treatment apparatus machine is known a priori, e.g. by design.
• the control unit can use this information to control self- 5 cleaning cycles carried out by the laundry treatment apparatus as will be explained below in more detail.
• the laundry treatment apparatus further comprises a load detector adapted to detect the weight of laundry stored in the laundry storing compartment.
• the control unit is adapted to receive a signal from the load detector. It can determine a secondary parameter depending on the received load detector signal and water content 5 sensor signal. Said secondary parameter may be used by the control unit for controlling the operation and/or operation parameters of the laundry treatment apparatus, for example related to a drying and/or spinning operation or the like.
• said load detector may be or may comprise for example one or more of o the following: a weight sensor (e.g. connected to or integrated in the mounting of the drum); a sensor detecting oscillations/vibrations of the drum and/or machine; a sensor detecting the speed of drum rotation or its variations (in particular as a direct signal or in relation to an electrical and/or magnetic parameter of the motor driving the drum, like the supplied current, voltage and/or power and/or the magnetic flux detected by a magnet field 5 sensor); a logical component or piece of software integrated in or attached to the control unit for determining load indirectly (e.g.
• a weight sensor e.g. connected to or integrated in the mounting of the drum
• a sensor detecting oscillations/vibrations of the drum and/or machine
• a sensor detecting the speed of drum rotation or its variations (in particular as a direct signal or in relation to an electrical and/or magnetic parameter of the motor driving the drum, like the supplied current, voltage and/or power and/or the magnetic flux detected by
• the signal of a conductivity sensor may also be evaluated by the control unit to derive therefrom a measure for the laundry load in the laundry storing compartment (which is a drum in the preferred embodiment).
• control unit is adapted to receive the water content signal from the water content sensor and the load signal from the laundry load detector or sensor and to process or evaluate the signals for determining the humidity value of the laundry (moisture content or degree of the laundry) stored in the laundry storing compartment. So both signals are used to calculate or estimate a more reliable value for the relative moisture content of the o laundry.
• the 'relative' moisture or humidity content can be considered covering a range from 100% (where the laundry is wet close to dripping) and 0% where it has lost all humidity.
• control unit is further adapted to determine the humidity value of the laundry in dependency of the laundry type, and/or by retrieving the humidity value from a look-up table providing humidity values in dependency of the water 5 content and load signals.
• control unit is furthermore adapted to select or adjust one or more of the following parameters in dependency of the laundry water content sensor signal: estimated time to cycle end, drying air flow rate, drum rotation speed during tumbling and/, parameters of heat pump compressor operation, heating power, and/or parameters of self-cleaning operation.
• the laundry storing compartment preferably is or comprises a laundry drum, preferably a front loading drum
• the signal(s) from the laundry water content sensor and/or the load detector can further be used in addition or alternatively for selecting and/or adjusting other parameters of the laundry treatment apparatus, such as a steam generation rate, steaming time intervals, duration of warm-up, water flow rate to the steamer, creating user signals e.g. related to the water level in water reservoir.
• the signal(s) from the laundry water content sensor and/or the load detector may comprise analog and/or digital signal components and may be transmitted by a single signal line or a plurality of signal lines, in particular a signal bus, more in particular embodied according to a standardized interface such as I2C, SPI or CAN.
• said secondary parameter determined by the control unit may comprise one or more of the following: the humidity of the laundry; the absolute total water amount within the laundry storing compartment; the dry weight of the laundry; the distribution of the laundry in the laundry storing compartment; the distribution of water within the laundry storing compartment; and/or the type of laundry.
• said secondary parameter determined by the control unit comprises, is related to, or indicates the humidity of the laundry to be treated.
• the secondary parameter may indicate the humidity of the laundry in the laundry storing compartment, e.g., quantified as weight or mass of water per weight or mass of laundry.
• determining the secondary parameter by the control unit may comprise deriving the weight or mass of laundry water content from the laundry water content sensor signal, deriving the weight or mass of laundry from the load sensor signal, and/or dividing the derived weight or mass of laundry water content by the derived weight or mass of laundry (or vice versa). Deriving the weight or mass of laundry water content and/or deriving the weight or mass of laundry may also comprise derivation of intermediate signals from the respective sensor signals or from combinations of different sensor signals.
• the secondary parameter determined by the control unit comprises, is related to, or indicates the absolute total water amount within the laundry storing compartment.
• the water content sensor may, e.g., be limited to measuring the laundry water content within a certain constricted volume of the laundry storing compartment or contained in a constricted portion of the laundry. This may be due to "blind zones" of the sensor (see below) or because of a limited depth of penetration achievable by the applied measurement method.
• the control unit may then derive the absolute total water amount within the laundry storing compartment by means of correcting the laundry water content sensor signal using the load detector signal.
• the secondary parameter determined by the control unit may further or alternatively comprise the dry weight of the laundry, e.g.
• the secondary parameter determined by the control unit may further or alternatively comprise the type of laundry in the laundry storing compartment, which is beneficial, e.g., as it allows to adapt parameters of the laundry treatment such as a maximum water, steam and/or drying air temperature to the needs of the laundry being treated.
• the type of laundry may be defined, e.g. by its specific water absorbance, specific weight, or similar parameters. Determining the type of laundry may preferably include determining the dry laundry weight, comparing the dry laundry weight to the wet laundry weight, determining the rate of water removal from the laundry, determining a specific water absorbance of the laundry, and/or the like.
• the secondary parameter determined by the control unit may further or alternatively comprise the distribution of the laundry and or the distribution of water within the laundry storing compartment. Having signals indicating one or both of these distribution is especially beneficial for adjusting the drum speed and/or acceleration and/or deceleration so as to avoid excessive vibrations of the machine and/or in order to create a more uniform distribution while spinning up the drum.
• the drum may be turned faster during a laundry drying cycle when the water content distribution is detected to be non-uniform while the drum rotation may be reduced or even stopped, when the water content is detected to be uniform, which can be an advantage for achieving a low power consumption of the laundry treatment apparatus.
• deriving the secondary parameter by the control unit may also 5 comprise obtaining a user input, in particular a user input indicating the type of laundry loaded into the laundry storing compartment.
• control unit is adapted to determine a laundry load value using the signal from the load detector and to adjust the so-obtained laundry load value by means of o the signal obtained from the laundry water content signal.
• the load detector may be embodied in the form of a conductivity
• such a system can be used5 to estimate the amount of laundry in a rotating laundry drum by evaluating, for example, the variations and/or noise in the measured conductance between two detector electrodes. As the measured conductance values depend on the amount of laundry in the drum as well as on the humidity of the laundry, a more accurate value of the laundry weight can be derived by correcting the load detector signal using the laundry water content sensor o signal.
• control unit is adapted to determine a laundry water content value using the laundry water content sensor signal and to adjust the so-obtained laundry water content value using the load detector signal. This is especially beneficial, if the 5 signal from the water content detector alone does not or not under all circumstances
• the accuracy of the water content sensor may, e.g., be limited due to "blind zones" or because of a limited measurement penetration depth as mentioned above.
• the control unit may then obtain a more accurate value of the laundry water content by correcting the laundry water o content sensor signal using load detector signal.
• the laundry storing compartment is a rotatable drum driven by a drum motor and the load detector is a drum motor current, voltage, power and/or torque detector.
• the load detector is a drum motor current, voltage, power and/or torque detector.
• a load detector can be implemented in the form of a motor torque detector or comprising a motor torque detector.
• a motor torque detector can be implemented in the inverter control electronics which is providing power to the motor, because the power to be provided to the motor is related to the torque created by the motor.
• a motor current, motor voltage or motor power detector may be provided.
• generating the load detector signal by the load detector and/or generating the laundry water content signal by the laundry water content sensor therefore comprises detecting temporal variations of the motor torque.
• the control unit receives a separate signal containing information on variations of the motor torque and uses this signal for deriving or adjusting the load detector signal and/or the laundry water content signal.
• the laundry water content sensor may not only generate a laundry water 5 content signal but may additionally provide useful data on the weight of the laundry in the laundry storing compartment.
• a laundry water content sensor may be designed to emit high frequency electromagnetic waves into the laundry storing compartment and detect the signals arising from portions of the waves that are transmitted through and/or reflected by the laundry. In 0 a similar way as the movement of the laundry in a slowly rotating drum creates temporal variations of the motor torque (see above), it will create characteristic temporal variations in the detected high frequency electromagnetic wave signals depending on the weight, type, and/or distribution of the laundry in the drum. Such signals can thus be useful for determining the weight of the laundry in the laundry drum.
• the load detector may not only generate a signal indicating the weight of the laundry in the laundry storing compartment but may additionally contain information on the laundry water content, as mentioned above in the examples of the conductivity measurement load detector and the motor voltage, current or power detector.
• an embodiment of the load detector detects the weight of laundry stored in the laundry storing compartment by evaluating at least one signal from the laundry water content sensor.
• the water content sensor may detect the laundry water content by evaluating at least one signal from the load detector.
• the same sensor or plurality can be used for generating both a load sensor signal and a water content sensor signal.
• the contactless laundry water content sensor comprises at least one high frequency (HF) electromagnetic wave emitter and/or at least one high frequency (HF) electromagnetic wave receiver.
• the high frequency electromagnetic wave emitter emits high frequency electromagnetic waves into the laundry storing compartment. A portion of the emitted waves is absorbed by the humid laundry or leaves the laundry treatment apparatus and does not reach the receiver. Another portion of the emitted waves is transmitted through the laundry and forms a transmitted electromagnetic signal that reaches the receiver. Yet another portion of the emitted waves is reflected by the humid laundry and/or parts of the laundry treatment apparatus and forms a reflected signal also reaching the receiver.
• the term "reflection" is meant to comprise not only reflection in its narrow sense but also refraction as well as absorption with subsequent re-emission with unchanged and/or changed frequencies.
• the or a high frequency electromagnetic wave emitter and the or a high frequency electromagnetic wave receiver forming the contactless laundry water content sensor are separate components mounted at opposite to each other with respect to the laundry storing compartment, so that electromagnetic waves emitted by the emitter can pass through the laundry storing compartment towards the receiver.
• the 'emitter' can also be denoted or understood as being a 'transmitter' and/or the 'receiver' can be understood as sensor detecting a or the respective signal.
• one or more electromagnetic wave emitters are provided only (without providing an electromagnetic wave receiver) and the signal loss is detected by detecting a damping value (signal damping or attenuation or transmission loss) of the signal emitted from the one or more emitters.
• a damping value signal damping or attenuation or transmission loss
• the absorption of the signal depends on the amount of water in the laundry storing compartment.
• the emitter-only or transmitter-only arrangement where the HF signal is emitted and received by the same element is denoted as 'HF electromagnetic wave emitter and HF electromagnetic wave receiver'.
• the high frequency emitter and the high frequency receiver are integrated into a common housing, mounted on a common substrate, and/or use a single 5 antenna for signal emission and reception.
• both transmitter and receiver are preferably located on the same side of the laundry storing compartment and the receiver is preferably be adapted to receive electromagnetic signals that are reflected by the laundry.
• the frequency or frequencies of the electromagnetic radiation emitted by the emitter and/or the frequency or frequencies which the receiver is tuned to are adjusted so that the radiation interacts preferably with the water inside the laundry instead of other material such as, e.g., textiles fibers.
• the different portions of absorbed, transmitted and/or reflected electromagnetic waves significantly depend on the laundry5 water content, so that the strength and other characteristics (e.g. temporal variations, frequency spectrum, phase shifts and/or time delays) of the electromagnetic signals reaching the high frequency electromagnetic wave receiver strongly depend on the laundry water content.
• the laundry water content can be estimated from the signal(s) generated in the HF electromagnetic wave receiver and/or by comparing those o signals with the characteristics of the electromagnetic waves emitted by the HF
• the high frequency or the high frequencies used by the laundry water content sensor is/are in the range of 900 to 930 MHz and/or in the range of 2.4 - 2.5 GHz, and/or in 5 the range of 5.7 - 5.9 GHz. More preferably, the high frequency or the high frequencies used by the laundry water content sensor 200 is/are in the range of 902 to 928 MHz and/or in the range of 2.400 - 2.483 GHz, and/or in the range of 5.725 - 5.875 GHz.
• the laundry water content sensor is adapted to detect the signal absorption by the laundry, the signal reflection by the laundry, or the signal absorption and signal reflection by the laundry.
• the laundry water content sensor is adapted to detect signal absorption and/or reflection by measuring the transmitted and/or absorbed and/or reflected signal intensities. More preferably, the laundry water content sensor is adapted to 5 detect further signal interactions with and/or signal modifications by the laundry, in
• At least one high frequency electromagnetic wave emitter and/or at least one high frequency electromagnetic wave receiver comprises a planar antenna, in particular a patch antenna.
• a patch antenna (which may be a microstrip antenna) is a thin antenna, preferably comprising a rectangular layer (patch) of metal mounted above a larger
• the components are
• a patch antenna can be built, for example, on a dielectric o substrate, using the same or similar materials and techniques as are well known from the production of printed circuit boards.
• Planar antennas are very common in sensing applications. Advantages of patch antennas include their compact size, low cost, reliability, robustness, large-scale availability,5 reproducibility, and simple integration into larger systems. They can be tuned to a wide range of frequencies and, in particular, they are easy to integrate into array structures combining microstrip antennas with other electronic functions. Therefore patch antennas are particularly well suited as sensor components for use in a laundry treatment apparatus. 0 In an embodiment, the control unit of the laundry treatment apparatus is adapted to execute a calibration cycle for calibrating the laundry water content sensor and/or the load detector when the amount of water inside the laundry storing compartment is known.
• said calibration cycle may comprise recording and/or processing of the signal(s) from the laundry water content sensor and/or the load detector at one or several o instances in time.
• said calibration cycle is executed when no laundry is stored in the laundry storing compartment. In order to make sure that the laundry storing compartment is empty when executing the calibration cycle, one or more of the following conditions may be checked in the embodiments:
• a laundry detector preferably mounted at a lower part of the drum, indicates that no 5 load is in the laundry storing compartment;
• the load detector signal is (apart from very small deviations) consistent with the signal expected for an empty laundry storing compartment;
• the water content sensor signal is (apart from very small deviations) consistent with the signal expected for an empty laundry storing compartment;
• the laundry water content sensor and/or the load detector (in the o following commonly denoted as “sensors") or at least one of the sensor components is/are arranged in a lower region of the laundry storing compartment.
• sensors the load detector
• the sensor components is/are arranged in a lower region of the laundry storing compartment.
• Such an arrangement is particularly beneficial if the accuracy of the sensor measurements depends on the distance between the laundry and the respective sensor or one of its components because gravity will push the laundry towards the lower region of the laundry storing compartment and 5 thus close to any sensor mounted near to that region.
• such an arrangement provides for an increased probability that a significant amount of the laundry is within the active area or active volume of the respective sensor.
• active area and active volume are used to denote the area or volume of the laundry storing compartment within which laundry water content or laundry weight can be most effectively sensed by o the respective sensor.
• the laundry storing compartment is rotatable drum and the laundry water content sensor and/or the load detector or at least one of the sensor components is/are arranged at a position in the lower region of the drum and shifted along the main rotation 5 direction of the drum mantle.
• This arrangement increases the probability that a significant amount of the laundry is within the active area or active volume of the respective sensor, because as described above, when the drum is slowly rotating, then the pieces of laundry will be raised along the drum mantle following the drum rotation direction before falling back towards the bottom of the drum.
• the drum is spinning at a higher 0 speed, then the laundry will be compressed towards the laundry mantle, so that it can be beneficial to place the sensors or sensor components at positions sufficiently close to the mantle.
• the laundry water content sensor and/or the load detector are positioned 5 at or close to the drum mantle.
• the laundry storing compartment wall or wall sections are made of material that is transparent for passing the high frequency electromagnetic waves used by the laundry water content sensor.
• the laundry drum, a lateral wall of the laundry drum, and or a lateral wall of the laundry storing compartment could be made of plastics or plastic-polymeric material such as PTFE (e.g. Teflon), PE, PP, and/or polyamides.
• PTFE e.g. Teflon
• PE e.g. Teflon
• PE polyethylene
• polyamides polyamides
• the drum mantle or portions of the drum mantle and/or the drum rear wall and/or a back wall of the laundry dryer are made of appropriate material that allows the HF electromagnetic waves to pass through, i.e.
• the water content sensor and/or the load sensor are placed outside the laundry storing compartment.
• the sensor components can be well protected against humidity, pollution by fluff, or mechanical stress created by the laundry.
• the sensor may reach an increased life time and/or can be designed to be more cost efficient.
• At least one component of the laundry water content sensor is placed outside of the laundry storing compartment. More preferably all components of the laundry water content sensor are placed outside of the laundry storing compartment. o Preferably at least one component of the load detector is placed outside of the laundry storing compartment. More preferably all components of the load detector are placed outside of the laundry storing compartment.
• mounting the laundry water content sensor and/or the load detector outside the laundry storing compartment may avoid or reduce "blind zones" of the detectors, as will be explained 5 below in more detail.
• selecting or adjusting the drying air flow rate by the control unit in dependency of the laundry water content sensor signal comprises selecting one of at least two different predetermined target levels of the drying air flow rate depending on the o laundry water content.
• the control unit may adjust the target drying air flow rate smoothly within a predefined range of target flow rates in dependency of the determined laundry water content.
• a drying air blower is arranged such that the created drying air flow rate and/or the created average drying air flow rate is at or close to the target flow rate selected and/or adjusted by the control unit.
• control unit may adjust and/or select a target rotation speed of the drying air blower and/or adjust and/or select the electrical power provided to the drying air blower in dependency of the determined laundry water content.
• the drying air is cooled and/or dehumidified in a heat exchanger by exchanging heat with a cooling air stream (e.g. in a condensate-type dryer or washer- dryer).
• a cooling air stream is used to cool a component of a heat-pump system by exchanging heat with the cooling air stream.
• a component of the heat pump system cooled in this way is not in direct heat-exchanging contact with the process air and is e.g.
• the cooling air flow may be selected and/or adjusted in dependency of the laundry water content, e.g. as follows: At the beginning of a drying cycle, when the laundry water content is still high, only a relatively low cooling air flow rate is created, because the laundry needs to be heated up to the drying temperature first, so that any heat energy taken away by the cooling air flow during that phase is wasted and leads to an increase of the time needed for laundry drying. However, when the designated operating temperature is reached and the laundry water content decreases significantly, the cooling air flow can be increased in order to increase the rate of water removed from the drying air A and thus achieve efficient drying. In this way, the described process of selecting and/or adjusting the cooling air flow helps to reduce both the time needed for a drying cycle and the overall energy consumption of the laundry treatment apparatus.
• selecting or adjusting the cooling air flow rate by the control unit in dependency of the laundry water content sensor signal comprises selecting one of at least two different predetermined target levels of the cooling air flow rate depending on the laundry water content.
• the control unit may adjust the target cooling air flow rate smoothly within a predefined range of target flow rates in dependency of the determined laundry water content.
• a cooling air blower is arranged such that the created cooling air flow rate and/or the created average cooling air flow rate is at or close to the target flow rate selected and/or adjusted by the control unit.
• the control unit may adjust and/or select a target rotation speed of the cooling air blower and/or adjust and/or select the electrical power provided to the cooling air blower in dependency of the determined laundry water content.
• a drying air flow is created by blowing external air (i.e. air from the outside of the apparatus cabinet) through the laundry treatment chamber.
• external air i.e. air from the outside of the apparatus cabinet
• laundry drying is made in the apparatus being a vented air dryer.
• External air venting may be performed permanently or temporally, e.g. in a mixed vented/closed loop-type dryer.
• the drying air flow rate is adjusted in dependency of the laundry water content, whereby selecting or adjusting the drying air flow can be achieved in the same way as described above for the cooling air flow.
• the laundry storing compartment is or comprises a rotatable laundry 5 drum
• the drum rotation speed is selected and/or adjusted in dependency of the laundry water content.
• selecting or adjusting the drum speed by the control unit in dependency of the laundry water content sensor signal comprises selecting one of at least two different predetermined target levels of the drum speed depending on the laundry water content.
• the control unit may adjust the target drum o speed smoothly within a predefined range of target flow rates in dependency of the
• the drum motor is arranged such that the resulting drum speed and/or average drum speed is at or close to the target speed selected and/or adjusted by the control unit.
• the control unit may adjust and/or select the electrical power provided to the drum motor in dependency of the 5 determined laundry water content.
• the laundry treatment apparatus further comprises a steam generation unit for generating steam for laundry steam treatment which is controlled by the control unit, and the control unit is adapted to select or adjust one or more of the following o parameters in dependency of the laundry water content sensor signal and/or or the load detector signal: the flow rate of the steam provided for laundry treatment; the temperature of the steam provided for laundry treatment; and/or one or more time intervals during which steam is provided for laundry treatment.
• the control unit is adapted to implement the control by one or more of the
• control unit is adapted to implement the control by: c) decreasing the heating power when the detected laundry water content sensor signal falls below a fifth 5 predetermined value (W5) or is in a fourth predetermined value range, and optionally d) further decreasing the heating power when the detected laundry water content sensor signal falls below a sixth predetermined value (W6, W7) or is in a fifth predetermined value range.
• control unit of the laundry treatment apparatus is adapted to implement the control by one or more of the following: d) increasing the drying air flow 5 rate and/or the drying air blower speed when the detected laundry water content sensor signal falls below a first predetermined value or is in a first predetermined value range (compare embodiments shown in Fig. 13 (Wl)); e) decreasing the drying air flow rate and/or the drying air blower speed when the detected laundry water content sensor signal falls below a second predetermined value or is in a second predetermined value range0 (compare embodiments shown in Fig. 14 (W2); Fig. 15 (W4)).
• control unit (51) is adapted to implement the control by one or more of the following: f) increasing the cooling air flow rate speed when the detected laundry water content sensor signal falls below a third predetermined value or is in a third predetermined5 value range (compare embodiments shown in Fig. 14 (W2); Fig. 15 (W4), g)
• control unit is adapted to implement the control by one or more of the following: i) decreasing the compressor speed of a heat-pump system of the apparatus 5 or the compressing power of the compressor when the detected laundry water content sensor signal falls below a seventh predetermined value or is in a seventh predetermined value range or exceeds a first temporal gradient (dWl/dt) of the water content sensor signal, j) increasing the compressor speed of a heat-pump system of the apparatus or the compressing power of the compressor when the detected laundry water content sensor o signal falls below an eighth predetermined value or is in an eighth predetermined value range or exceeds a second temporal gradient (dW4/dt) of the water content sensor signal, and k) further increasing/decreasing the compressor speed of a heat-pump system of the apparatus or the compressing power of the compressor when the detected laundry water content sensor signal falls below/rises above a ninth predetermined value or is in a ninth 5 predetermined value range or falls below/rises above a third temporal gradient (dW
• first to sixth predetermined values can be different or partially the same values.
• first predetermined value is higher than the second predetermined value (or first range above second range).
• fourth predetermined value is higher than the fifth predetermined value (or fourth range above fifth range).
• Fig. 1 a schematic view of a laundry treatment apparatus
• Fig. 2 a perspective view of a laundry treatment apparatus
• Fig. 3 a schematic sectional side view of a laundry treatment machine with a
• Fig. 4 a detailed sectional view of the conductivity-measurement system comprising two electrodes as shown in Fig. 3,
• Fig. 5 a schematic sectional side view of a laundry treatment machine with a
• Fig. 6 a schematic view of the laundry storing compartment of an embodiment of a laundry treatment apparatus with a contactless laundry water content sensor
• Fig. 7 a schematic view of the laundry storing compartment of another embodiment of a laundry treatment apparatus with a contactless laundry water content sensor
• Fig. 8 a schematic view of an embodiment of a contactless laundry water content sensor
• Fig. 9 a schematic view of another embodiment of a contactless laundry water content sensor
• Fig. 10 a schematic view of a further embodiment of a contactless laundry water
• FIG. 11a a schematic view of the laundry storing compartment of a further embodiment of a laundry treatment apparatus with a contactless laundry water content sensor
• Fig. 1 lb a schematic view of the laundry storing compartment of yet another
• Fig. 12 a graph illustrating the functional or experimentally determined relation
• Fig. 13 a graph illustrating the adjustment of drying air flow rate in dependency of the laundry water content
• Fig. 14 a graph illustrating the adjustment of drum speed in dependency of the laundry water content
• Fig. 15 a graph illustrating the joint adjustment of drying air flow rate and drum speed in dependency of the laundry water content
• Fig. 16 a graph illustrating the adjustment of heat pump compressor speed in
• Fig. 17 a graph illustrating joint adjustment of drying air heating power in dependency of the laundry water content.
• Fig. 1 shows a schematically depicted laundry treatment apparatus 2 having a cabinet or casing 3 and indicated/housed therein some of the apparatus components.
• the laundry treatment apparatus 2 comprises a heat pump system 4, including a closed refrigerant loop 6 which comprises in the following order of refrigerant flow B: a first heat exchanger 10 acting as evaporator for evaporating the refrigerant and cooling drying air, a compressor 14, a second heat exchanger 12 acting as condenser for cooling the refrigerant and heating the drying air, and an expansion device 16 from where the refrigerant is returned to the first heat exchanger 10.
• the heat pump system 4 forms the refrigerant loop 6 through which the refrigerant is circulated by the compressor 14 as indicated by arrow B.
• the drying air flow A within the laundry treatment apparatus 2 is guided through a laundry 5 storing compartment 17 of the laundry treatment apparatus 2, i.e. through a compartment for receiving articles to be treated, e.g. a rotatable drum 18.
• the articles to be treated are textiles, laundry 19, clothes, shoes or the like.
• the drying air flow is indicated by arrows A in Fig. 1 and is driven by a drying air blower 8.
• the drying air channel 20 guides the drying air flow A outside the drum 18 and includes different sections, including the section0 forming the battery channel 20a in which the first and second heat exchangers 10, 12 are arranged.
• the drying air exiting the second heat exchanger 12 flows into a rear channel 20b in which the drying air blower 8 is arranged.
• the air conveyed by blower 8 is guided upward in a rising channel 20c to the backside of the drum 18.
• the air exiting the drum 18 through the drum outlet (e.g. the loading opening of the drum 18) is filtered by a fluff filter5 22 arranged close to the drum outlet in or at the channel 20.
• the optional fluff filter 22 is arranged in a front channel 20d forming another section of channel 20 which is arranged behind and adjacent the front cover of the laundry treatment apparatus 2.
• the condensate formed at the first heat exchanger 10 is collected and guided to the condensate collector 30.
• the condensate collector 30 is connected via a drain conduit 46, a drain pump 36 and a drawer pipe 50 to an extractable condensate drawer 40. I.e. the collected condensate can be pumped from the collector 30 to the drawer 40 which is arranged at an upper portion of the laundry treatment apparatus 2 from where it can be comfortably withdrawn and emptied by a user.
• the laundry treatment apparatus 2 comprises a control unit 51 for controlling and monitoring the overall operation of the laundry treatment apparatus 2.
• the control unit 51 receives a temperature signal from a temperature sensor 41 which is arranged at the outlet of the second heat exchanger 12 (condenser) or at o the outlet of the compressor and which is indicative of the refrigerant temperature at this position.
• the control unit 51 also controls the drain pump 36.
• the control unit 51 is able to control other parts of the laundry treatment apparatus 2.
• the laundry treatment apparatus also comprises a nozzle unit 88, a steam generation unit 90 (in short 'steamer'), and a steamer tank 140 for storing liquid to be supplied to the steam generation unit 90.
• a pump unit e.g. the drain pump 36
• a pump unit is arranged for pumping the liquid collected in the condensate collector 30 to the drain tank 40 and/or to the steamer tank 140 via the branching element 142.
• steam for laundry treatment can be generated in the steam generation unit 90 and guided to the nozzle unit 88 by means of a steam conduit 106.
• the nozzle unit 5 serves for injecting the generated steam into the laundry storing compartment 17.
• the nozzle unit 88 is mounted at a rear wall of the laundry treatment apparatus 2.
• the steam generation unit is an inline steam generator. More preferably, the flow rate of steam generated by the steam generation unit and injected into the laundry storing compartment as well as other parameters of steam generation (e.g. steam o temperature, steaming intervals and/or heating energy) are controlled by the control unit
• the rotatable drum 18 is driven by a motor 150 via a belt 156.
• the motor 150 also drives blower 8 and/or is a variable speed motor which can be driven 5 with a speed that is set by the control unit 51.
• Motor 150 is powered by an electronic board 152 (e.g. by an inverter) which in turn is controlled by control unit 51 via signal line 154.
• the electronic board 152 preferably sends a signal to the control unit 51 via line 154 indicating the motor torque and/or the temperature of electronic board and/or other parameters of the board and the motor (see further details below).
• Fig. 2 shows a front perspective view of a laundry treatment apparatus that uses a heat pump system 4.
• the outer appearance of the depicted dryer 2 is defined by the casing 3 comprising a top cover 56, a left cover or wall 58, a front cover 60 having a front door 55 and a front top panel 62.
• the front top panel 62 frames a drawer cover 64 of the
• the right portion of the front top panel 62 forms an input section 66 wherein here the elements (like indicators, a display, switches and so on) of the input section 66 are not shown in detail.
• Fig. 3 illustrates a schematic sectional side view of a laundry treatment apparatus 2 with o two electrodes 82 and 84 forming an embodiment of a conductivity system that can be used for estimating the laundry humidity and/or the laundry load inside the laundry drum 18 (see below).
• the apparatus 2 comprises the laundry storing compartment 17 inside the laundry drum 18, the front door 55, the loading opening 54 of the drum 18, heat exchangers 10, 12, and a front frame 70.
• the electrodes 82 and 84 are attached at the rear 5 side of the front frame 70 and are arranged at a lower portion of a laundry loading front opening 54 of the laundry drum 18 and below the front door 55.
• the first electrode 82 is arranged above the second electrode 84. In this embodiment, the distance between the electrodes 82 and 84 is relatively small as compared to the dimensions of the laundry storing compartment 17.
• Fig. 4 depicts a detailed sectional side view of the electrodes 82 and 84.
• the electrodes 82 and 84 are parts of a conductivity measurement system. Said conductivity system is provided for determining the humidity of the laundry 19 inside the drum 18 and/or for estimating the amount of load in the laundry drum 18.
• the electrical conductance and/or resistance between the electrodes in particular its level of electrical noise and/or fluctuation during the operation of the laundry treatment apparatus can be measured for this purpose.
• the measurement is done during those stages of a laundry treatment program, when the laundry is not or not yet completely dry, such as at the beginning of a drying program.
• the wet load can connect electrically the first electrode 82 to the second electrode 84, when a part of the wet load touches simultaneously the first electrode 82 and the second electrode 84.
• a peak e.g. of low conductance and/or high resistance
• a signal related to the detected electric resistance and/or conductivity particularly the maximum conductivity value measured at peaks, and also the average value of a signal related to the detected electric resistance and/or conductivity are related to the humidity of the laundry inside the laundry drum 18.
• evaluating the noise and/or fluctuation of the detected electric resistance and/or conductivity comprises one or more of the following:
• Fig. 5 is a schematic sectional side view of a laundry treatment apparatus 2 similar to that shown in Fig. 3 but with a laundry water content sensor 200 and a load sensor 220.
• the laundry water content sensor 200 is a contactless sensor, i.e. a sensor that can determine the water content of the laundry 19 inside the laundry storing compartment 17 without the need of getting into direct contact with the laundry 19.
• the laundry water content sensor 200 generates and outputs a laundry o water content sensor signal 218 that is received by the control unit 51 , where the signal can be used for controlling the operation of the laundry treatment apparatus 2 and/or for controlling at least subroutines of one or more laundry treatment programs.
• the control unit 51 may adjust the following parameters depending on the received laundry water content sensor signal 218:
• drum rotation speed e.g. in laundry treatment programs for tumbling or spinning
• the signal 218 from the laundry water content sensor is related to the total amount of water contained in the laundry 19 inside the laundry storing compartment 17, so 5 that during a laundry treatment program for tumbling and/or drying, the control unit 51 can estimate the total amount of water that is stored by the laundry or articles in the compartment 17 and remains to be removed from the laundry or articles. By comparing the estimated the total amount of water contained in the laundry at two or more points in time, the control unit may further estimate the profile of the past, current, and/or future rate of water removal achieved by a given laundry treatment program. It may 5 also be provided to estimate the total amount of water that has been removed during a treatment cycle and/or a certain period of time of laundry treatment.
• the specific design and program parameters of a machine such as available heating power, drum rotation speed and/or compressor power are taken into account when l o estimating the water removal rate or the amount of water that has been removed. More preferably, the water removal rate achieved by a specific program of a specific machine may be known or assumed a priori from the machine design.
• the estimated time until the end of the laundry treatment cycle (here: tumbling or drying) can be derived.
• the so estimated time to cycle end may be used, e.g., for controlling operation parameters of the laundry treatment apparatus and/or for providing information to the user about the remaining time required for a laundry treatment.
• the flow rate of drying air (A) may be increased with decreasing laundry water content and/or increasing amount of removed water so as to ease and/or speed up the removal of remaining water in almost dry laundry.
• the drying air flow is adjusted over time depending on the water content sensor signal 218 and other operation
• the speed of the drying air fan 8 is increased with decreasing laundry water content and/or increasing amount of removed water and/or when the water removal rate is high in order to compensate for the increased pressure drop that may occur in the drying air circuit e.g. due to clogging of air filters by moisture.
• the rotation speed of a laundry drum 18 is adjusted depending on the signal 218 of the water content sensor 200. More preferably, the drum rotation speed is reduced with decreasing amount of water detected in the laundry, because a lower rotation speed may be 35 appropriate for moving the laundry that becomes lighter with decreasing water content along the treatment cycle. Furthermore, the speed and/or power of the heat pump compressor 14 may be adjusted according to the water content sensor signal 218. In particular, the compressor speed and/or power may be reduced with decreasing amount of remaining water in the drum (laundry/articles), since a smaller refrigerant flow rate is well matched with the lower 5 humidity level exiting the drum and entering the evaporator.
• the power for heating the drying air A and/or the drying air temperature are also adjusted depending on the estimated amount of remaining water in the laundry and/or the estimated amount of removed water and/or the estimated water removal rate.
• An estimation of the laundry water content at the beginning of, e.g., a laundry drying cycle by means of the laundry water content sensor 200 can provide an accurate value of the whole amount of water removed and/or to be removed from the laundry.
• the obtained knowledge about the total amount of water removed and/or to be removed can implicitly provide knowledge about the amount of water available for self-cleaning cycles, in 5 particular when also the condensation efficiency of the laundry treatment apparatus
• control unit 51 may use this information to control self-cleaning cycles carried out by the laundry treatment apparatus 2.
• Self-cleaning cycles are for removing fluff from a drying air fluff filter of the apparatus by flushing the filter with a liquid, preferably water and highly preferably water o condensed during the laundry drying process
• the apparatus 2 is arranged to normally do one self-cleaning cycle after each laundry drying cycle.
• a condensate water amount V0 is the optimal amount of water required for a self-cleaning cycle (e.g. washing of filters 22)
• water amount VI is the amount of water estimated as being available for self-cleaning after a drying cycle (for example calculated from the total amount of water removed from the laundry multiplied by condensation efficiency).
• V0 ⁇ VI If V0 ⁇ VI, then the available amount of water is appropriate for one washing cycle, so that the apparatus can perform the self-cleaning cycle after the drying cycle as usual. 0 - If V0 » VI, then additional self-cleaning cycle(s) could be added when appropriate.
• the control unit may delay self-cleaning until enough water for an effective self-cleaning is available.
• the user may be given an alarm signal indicating that filters need to be cleaned manually since self- cleaning was not possible.
• an alarm is given when self-cleaning was skipped several times. More preferably the user is warned that the laundry treatment apparatus 5 2 may need inspection when the frequency of skipped self-cleaning cycles is rises above a certain threshold which indicates a possible defect.
• the load sensor 220 shown in the embodiment of Fig. 5 may be a conductivity measurement system as shown in Fig. 4 and described above. Having the0 height level in the laundry storing compartment 17 determined for example by the load sensor being a conductivity sensor, the water content, and, optionally, the type of laundry, it is possible to estimate e.g. the weight and/or volume and/or mass of the laundry load.
• an acoustic system such as an ultrasonic sensor may be used for measuring the height level of laundry 19 loaded into the laundry storing compartment 17.5
• the load sensor 220 may also be embodied as a weight sensor associated to the laundry storing compartment 17, in particular the drum 18.
• the load sensor (not necessarily load sensor 220 shown in Fig. 1) o may comprise a circuitry for measuring electrical parameters of the drum motor such as the electric current and/or the induced voltage.
• the electrical current through the electric drum motor is at least approximately proportional to the torque of the electric drum motor.
• the electric current measured gives a measure of the torque of the electric drum motor and from the torque the amount of load may be determined.
• 5 the torque of the electric drum motor may be detected and/or calculated differently, for example by means of a torque sensor associated to the drum motor.
• the detection of the load amount or load mass is for example provided by a load sensor formed of the electronic board or inverter 152 which sends a signal corresponding to the torque of drum drive motor 150 to the control unit via line 154.
• Control unit 51 processes the torque signal 154 for determining the load or mass of the laundry and/or articles in the drum 18.
• the load sensor 220 comprises one or a plurality of temperature sensors.
• the amount of load in the laundry storing compartment may be determined from 5 the temperature difference of the drying air A between an inlet and outlet of the laundry storing compartment 17.
• the temperature difference is related to the amount of water extracted from the laundry and decreases with decreasing laundry load because of a reduced heat exchange between the air flow and the reduced amount of laundry.
• the temperature of the air flow at the outlet of the laundry storing compartment 17 can be used alone for estimating the amount of load in the laundry storing compartment 17.
• the amount of load laundry storing compartment 17 may be detected by the temperature difference of the air flow between an inlet and outlet of the first heat exchanger 10.
• the load sensor 220 may be embodied as a single sensor or may o comprise a plurality of sensors measuring one or more quantities that are appropriate for determining the load of laundry in the laundry storing compartment 17 as, e.g., explained above.
• the load sensor 220 may further comprise processing circuitry generating one or more load sensor signals by combining signals from the different individual sensors it comprises.
• the load sensor signal 228 may5 be a signal from a single sensor and/or may comprise a plurality of signals from said
• plurality of sensors and/or may comprise one or more combined and/or preprocessed signals in said processing circuitry.
• the load sensor 220 may consist of or comprise at least one sensor that is o used also for other purposes in the laundry treatment apparatus 2.
• existing temperature sensors 41 in the heat pump system or in the drying air flow A may be reused to form the load sensor 220.
• the laundry water content sensor 200 may be adapted for determining not only 5 a laundry water content but also the laundry load inside the laundry storing compartment.
• different characteristics (such as average value and amplitude and/or frequency of variations) of the one or more signals generated by the laundry water content sensor are evaluated, e.g. in the control unit 51, to determine both a laundry water content and a laundry load value.
• the load sensor 220 serves for determining the amount of laundry 19, i.e. the "load", inside the laundry storing compartment 17.
• the load sensor 220 provides a load sensor signal 228 to the control unit 51.
• the control unit may use the signal 228 to derive a quantity that is directly related to the amount of laundry, such as, e.g., the weight, the 5 volume, and/or the mass of the laundry inside the laundry storing compartment. Knowing the amount of laundry that is loaded in the laundry storing compartment is beneficial for controlling operation parameters of the laundry treatment apparatus 2, such as the speed and/or acceleration and/or deceleration of drum rotation during, e.g., tumbling or spinning.
• Determining the amount of load in the laundry storing compartment 17 may include receiving information about the amount of load through a user selection of data.
• the 5 preferred way to determine the amount of load by the user may include the provision of a button on the input section 66 which permits the user to select the amount of load.
• the button may comprise, for example, two positions corresponding to the choice of a "full- load condition” or a "half-load condition” which may depend on the quantity of laundry loaded into the laundry storing compartment 17 by the user.
• the user o input may be combined with signals obtained from the load sensor 220.
• a signal and/or quantity corresponding to the humidity of the laundry 19 inside the laundry storing compartment 17 is derived by the control unit 51 from the laundry water content sensor signal 218 and the load sensor signal 228.
• the 5 control unit 51 may determine the total amount of water and the load of laundry inside the laundry storing compartment 17. In particular, it may obtain the mass of water and the mass of the laundry load, both, e.g., in units of kg (or lbs.). Dividing the total amount of water by the load of laundry yields a value quantifying specific humidity of the laundry, such as kg of water per kg of laundry, for example. Preferably, the resulting specific o humidity value may be used for controlling the operation of the laundry treatment machine.
• Such controlling may comprise, for example, one or more of the following:
• Fig. 6 shows a sectional view of the laundry storing compartment 17 inside a laundry drum 18 with a contactless laundry water content sensor 200 using electromagnetic radiation for 5 measuring the laundry water content.
• the sensor 200 consists of a high frequency (HF) wave emitter 202 and a separate high frequency wave receiver 208.
• the emitter 202 generates and emits electromagnetic waves 216.
• a portion of the emitted waves 216 is absorbed by the humid laundry 19 or leaves the laundry treatment apparatus and does not reach the receiver 208.
• Another portion of the emitted waves 216 is transmitted through the laundry 19 and forms a transmitted electromagnetic signal T that reaches the receiver 208.
• emitted waves 216 is reflected by the humid laundry and/or parts of the laundry treatment apparatus 2 (e.g. by the drum 18) and forms a reflected signal R also reaching the receiver 208.
• the term "reflection” is meant to comprise not only reflection in its narrow sense but also refraction as well as absorption with subsequent re-emission with unchanged and/or changed frequencies.
• the frequency or frequencies of the electromagnetic radiation emitted by the emitter 202 and/or the frequency or frequencies which the receiver 208 is tuned or are adjusted so that the radiation interacts preferably with the water inside the laundry instead of other material such as, e.g., textiles fibers.
• the high frequency or the high frequencies used by the laundry water content sensor 200 is/are in the range of 900 to 930 MHz and/or in the range of 2.4 - 2.5 GHz, and/or in the range of 5.7 - 5.9 GHz.
• the high frequency or the high frequencies used by the laundry water content sensor 200 is/are in the range of 902 to 928 MHz and/or in the range of 2.400 - 2.483 GHz, and/or in the range of 5.725 - 5.875 GHz.
• the laundry water content sensor 200 is a contactless water content sensor as, e.g., in the embodiment shown in Fig. 6.
• the components 202, 208 of a contactless laundry water content sensor 200 do not need to get into direct contact with the laundry 19 for measuring the laundry water content.
• the components 202 and 208 of the water content sensor 200 are placed outside the laundry storing compartment 17.
• the sensor components can be well protected against humidity, pollution by fluff and mechanical stress created by the laundry.
• the sensor may reach an increased life time and/or can be designed to be more cost efficient.
• FIG. 11a shows a situation where a contactless laundry water content sensor based on emission and reception of HF electromagnetic waves 216 is mounted inside the laundry storing compartment 17.
• regions D the "blind zones"
• FIG. 1 lb shows the same design except that the laundry water content sensor 200 is located outside the laundry storing compartment 17. As depicted by the figure, the size of the "blind zones" D is significantly reduced by this arrangement.
• the laundry storing compartment 17 in such a way that HF electromagnetic waves 216 can pass through the respective portions of the walls 17a of the laundry storing compartment 17.
• the laundry drum 18, a lateral wall of the laundry drum 18, and or a lateral wall 17a of the laundry storing compartment 17 could be made of plastics or plastic-polymeric material such as PTFE (e.g.
• Teflon Teflon
• PE polystyrene
• PP polystyrene
• polyamides polystyrene
• a HF electromagnetic wave emitter 202 and a HF electromagnetic wave receiver 208 are located close to each other on the same side of the laundry storing compartment 17.
• emitter 202 and receiver 208 are attached to each other or integrated to form a single sensor unit. More preferably, they are mounted to a common PCB or substrate and/or are integrated in a common housing. In this way the handling of the sensor, such as its mounting into the laundry treatment apparatus, its calibration, and/or its connection to the control unit 51, can be simplified. Furthermore, costs may be reduced e.g. by saving cost for a second housing. Since in the embodiment according to Fig. 7, there is no direct path of HF electromagnetic wave transmission from the emitter 202 through the laundry storing compartment to the receiver 208, the laundry water content sensor 200 according to this embodiment is preferably adapted to detect a reflected electromagnetic wave signal R.
• Figs. 6 and 7 also depict the laundry water content sensor 200 arranged in a lower region of the laundry storing compartment 17, that is shifted towards the region towards which the laundry inside the laundry storing compartment 17 would be pushed by gravity.
• at least one component 202, 208 of the laundry water content sensor 200 or the laundry water content sensor 200 as a whole is arranged in a lower region of the laundry storing compartment 17. This is beneficial if the accuracy of the measurements of the sensor 200 or at least one its components 202, 208 depend on the distance to the laundry.
• such an arrangement can help to increase the probability that a significant amount of the laundry is within the active area/volume of the laundry water content sensor 200, i.e. the area/volume within which laundry water content can be detected effectively by the laundry water content sensor 200.
• Figs. 8, 9, and 10 illustrate further embodiments of a contactless laundry water content sensor 200 using emission and reception of HF electromagnetic waves.
• Fig. 8 is a more detailed view of a setup with an HF electromagnetic wave emitter 202 and an HF electromagnetic wave receiver 208 as shown in Fig. 7.
• the emitter 202 comprises an HF emitter circuitry 204 and an HF emitter antenna 206
• the receiver 208 comprises an HF receiver circuitry 210 and an HF receiver antenna 212.
• the emitter circuitry 204 and the emitter antenna 206 are integrated on a common PCB and/or HF emitter substrate 203.
• the receiver circuitry 210 and the receiver antenna 212 are integrated on a common PCB and/or HF receiver substrate 209. Both substrates 203 and 209 are assembled onto a common PCB and/or into a common contactless water sensor housing 201.
• Fig. 10 depicts an embodiment of a contactless water sensor 200 realizing a further level of integration by combining the emitter circuitry 204 and the receiver circuitry 210 on a common PCB or common substrate 215 and adding a common HF emitter and receiver antenna 214 to the same PCB or substrate 215.
• further levels of integration can be achieved in other embodiments, e.g.
• HF electromagnetic wave emitter 202 by sharing additional parts of circuitry between the HF electromagnetic wave emitter 202 and the HF electromagnetic wave receiver 208, such as, e.g., for power supply and/or signal conversion.
• IC integrated circuit
• IC integrated circuit
• a higher level of integration can yield cost reductions and/or simplifications regarding the handling of the sensor 200 (e.g. mounting, calibration, connectivity with other components).
• the graph of Fig. 12 shows in relative units the relation between water content determined by the water content sensor 200, the load weight or mass determined by the load detector (e.g. the current and/or voltage sensor implemented in electronic board 152) and the humidity of the laundry in the drum.
• the relation can also be established by experimental results (and interpolation therebetween) which are stored in a look-up table 52 (see Fig. 1) to which the control unit 51 has access.
• the analytical function is derived by an interpolation function using experimental results.
• the humidity of the laundry is more accurately determined by detection and evaluation and/or processing of the load signal (from 220) and water content signal (from 200).
• the humidity is the relevant value for the user in view of the laundry states 'dry', 'cabinet dry', 'ironing dry' or a laundry refreshment program in which a minimum humidity has to be reached
• the operation of the laundry treatment apparatus can be optimized.
• the optimized intended drying or humidity (wetting) state can be determined and reached by the apparatus more exactly what - at least in average of several operation runs - reduces treatment time and energy required.
• the laundry load is the sum of the laundry dry load and the water content (mass of water) bound in the laundry.
• the humidity then could be assumed to be the ratio of current water content of the laundry / maximum storable water content of the laundry.
• the humidity in particular the residual humidity (cabinet dry, ironing dry 7), depends on the laundry type.
• the method for determining the humidity and determining the laundry state at which a specific condition is met can further process the water content and the laundry load in dependency of the laundry type.
• the laundry type is for example input by the user via the control panel 66 or it is determined from the temporal progress of the drying process. Then different functions LH or look-up tables are available in dependency of the laundry type to further improve the accuracy in determining the humidity as a value used to terminate the drying process or to change from one sub-routine (e.g. drying) to another sub-routing (e.g. anticrease tumbling).
• Fig. 13 is a diagram showing how in an embodiment of the laundry treatment apparatus 2 having a heat pump system (10, 12, 14, 16) for drying air drying the drying air flow rate can be controlled by the control unit 51 in dependency of the laundry water content.
• the solid line of the diagram indicates the variation over time of the laundry water content in the laundry storing compartment 17 as determined from the laundry water content signal 218 and/or the load detector signal 228 according to the arrangements explained above.
• the dotted line depicts the temporal air flow rate profile as adjusted by the control unit 51 in response to the laundry water content.
• the drying air flow rate is low when the laundry water content is high, e.g. 5 at the beginning of a laundry drying cycle. Since the heat that can be absorbed from the drying air stream by the heat exchanger 10 is limited, the rate of water that can be removed from the drying air is also limited. On the other hand, the amount of water absorbed by a given volume of drying air A passing through the laundry storing compartment 17 is relatively high when the laundry water content is high. Thus, for the high laundry water o content at the beginning of the drying cycle, a relatively low flow rate of drying air A is sufficient to reach a laundry drying rate at or close to the maximal possible value, depending on the design of the laundry treatment apparatus 2.
• the drying air flow rate is increased by the control unit 51 when the water content drops below a certain threshold (e.g. the first predetermined water content value Wl). This increase of the o drying air flow rate corresponds the upwards step of the dotted line in the diagram.
• drying air flow is kept at a low rate as long as possible and only increased when and as much as necessary in order to keep a designated laundry drying rate, the energy consumed by the drying air fan and thus the total energy consumption of the laundry treatment apparatus can be reduced as compared to prior art not having this kind of drying air flow 5 rate adjustment.
• the drum rotation speed is 5 beneficially selected and/or adjusted in dependency of the laundry water content
• Fig. 14 is a diagram depicting an example of the temporal variations of the determined laundry water content and the adjusted drum rotation speed, both in relative units.
• the temporal profile of the laundry water content (solid line) is the same as in Fig. 13.
• the drum rotation speed is adjusted to a relatively high value, when the laundry water content is relatively high. This is because due to gravity the wet laundry tends be compressed at the bottom of the drum and needs to be moved and mixed quickly in order to enable efficient penetration of and water removal by the drying air.
• the control unit can evaluate the signal to determine the degree of dehydration during a spinning phase. Such the spinning can be stopped when the laundry is sufficiently dehydrated after water extraction and energy for driving the drum at spinning speed can be saved and respective time of spinning can be reduced.
• drying air cooling/drying for drying air cooling/drying as well as for embodiments wherein the drying air is cooled and/or dehumidified in a heat exchanger by means of a cooling air stream.
• the drum 18 and the drying air blower 8 are driven by the same motor 150 (see above).
• drum rotation speed and blower speed - and thus also drying air flow rate - are directly related to one another.
• the drying air flow rate is preferably adjusted to a relatively low value while the laundry water content is relatively high, in particular at the beginning of a laundry treatment cycle, and increased when the laundry water content decreases.
• the drum rotation speed is preferably reduced when the laundry water content becomes low, 5 i.e. towards the end of a laundry drying cycle.
• the blower 8 is driven by a motor that can be controlled by the control unit independent of the motor for driving the drum 18. In this way the speed, on/off periods and/or rotation o direction of the blower and the drum can be controlled independent of each other.
• control unit 51 adjusts the speed of the motor 150 in dependency of the laundry water content, thereby adjusting both the drying air flow rate and the drum speed at the same time.
• 5 Fig. 15 depicts an example of the resulting temporal profiles of laundry water content
• a low motor speed is applied while the laundry water content is high, e.g. above an upper threshold (e.g. a third predetermined water content value W3), so that both drum speed and drying air flow rate o are low at the beginning of a laundry drying cycle.
• an upper threshold e.g. a third predetermined water content value W3
• the water content value coincides for drying air flow rate and drum speed, but in other embodiments where the drum and drying air fan are driven independently, the two W3 values may be different ones. This way of control avoids waste of motor energy and/or heating energy during the initial drying phase as explained above.
• the speed of the motor 150 is increased, whereby drum speed and drying air flow rate are increased simultaneously. This is indicated by the simultaneous upwards steps of the dotted and dashed lines in the diagram.
• the motor speed is decreased again, resulting in a simultaneous decrease of the drum speed and the drying air flow rate, as shown by the simultaneous downwards steps of the dotted and dashed lines in the chart. In that way, waste of energy and excessive fluff creation due to drum rotation can be avoided (see above).
• a lower o threshold e.g. a fourth predetermined value W4
• the laundry drying rate can be estimated as the amount of removed water content per unit time.
• the estimated laundry drying rate can be used by the control unit 51 for adjusting the speed of the heat pump compressor 14 as illustrated in Fig. 16.
• the dashed 5 line in the diagram depicts an example of the temporal profile of the estimated laundry drying rate (measured in kg/min) obtained during a drying cycle of the laundry treatment apparatus.
• the drying rate is for example the temporal gradient dW/dt of the negative water content value W (i.e.
• dW/dt is positive when the water content value W decreases).
• the drying rate is relatively low and then starts to rise at the beginning of o the drying cycle. This is because the heat pump system, the drying air A, and the laundry storing compartment 17 are in the heat-up phase and have not yet reached their designated operating temperature. After a certain period of time, when the target operating temperature is reached, the drying rate arrives at a maximum and then begins to decline again, because the water content of the laundry 19 decreases and the remaining water is 5 absorbed less efficiently by the drying air A.
• the solid line shows an example of the adjusted heat pump compressor speed (in relative units).
• the heat pump compressor speed is adjusted to a relatively high value (first and highest speed) so as to speed-up the warm-up phase thereby reducing the overall time needed for the laundry drying cycle.
• the heat pump 5 compressor speed is reduced to an intermediate level (second speed lower than first speed) that is, however, still sufficient for drying the drying air A.
• the speed of the heat pump compressor 14 is o further reduced to a third speed (lower than the second speed) (second step of the solid line), because less humidity needs to be removed from the drying air and/or in order to reduce the drying air temperature towards the end of the drying cycle.
• Fig. 16 shows another embodiment of controlling the compressor speed as shown by the 5 dotted line.
• the compressor speed is high (e.g. at maximum) in the heat-up period for heating up the heat pump system.
• the compressor speed is lowered to a first reduced speed.
• the temporal gradient of the water content value rises and reaches a fourth water content value dW4/dt, which is higher than the third water content value dW3/dt.
• the condensation capacity of the evaporator is increased by increasing the compressor speed again to the higher speed (e.g. maximum speed).
• the speed of the compressor is lowered again to a second reduced compressor speed (which in this example is the same as the first reduced compressor speed).
• the laundry drying process further continues and when the temporal gradient of the water content value falls below a sixth water content value dW6/dt, the compressor speed is reduced to a third reduced compressor speed which is lower than the first and/or second reduced compressor speed.
• the lowered drying rate water content gradient
• the drying air humidity removal capacity is adapted to the lower yield of air humidity
• the control unit reduces the compressor speed to zero as the now residual water content of the laundry can be removed with the available cooling (water condensing) capacity of the evaporator and the residual drying air heating capacity of the condenser.
• the numbering first, second, third ... is a relative numbering to indicate the temporal sequence within the specific embodiment described.
• adjusting the heat pump compressor speed in dependency of the laundry water content (or more particularly, the estimated laundry drying rate, as in the above example) can reduce the overall drying cycle time as well as the total energy consumption of the laundry treatment apparatus 2.
• the laundry treatment apparatus 2 exhibits a heating element for heating the drying air A to be guided to the laundry storing compartment 17.
• the heating power of the heating element is adjusted in dependency of the laundry water content derived from the laundry water content signal 218 and/or the load detector signal 228 as explained above.
• Fig. 17 is an example showing two different ways how this can be realized.
• the dashed line shows the temporal profile of laundry water content, for the sake of clarity again identical to the one displayed in Figs. 13, 14, and 15.
• the heating power of the heating element starts at its maximal level and is then reduced step by step while the laundry water content decreases and less heat is required for removing the remaining moisture.
• the heating power is reduced to a second power value lower than the maximum heating power
• the power is o reduced to a third heating power lower than the second heating power
• the heater is switched off.
• the residual heat in the system e.g. laundry and laundry storing cabinet and/or condenser
• the residual cooling capacity of the heat exchanger evaporator
• a first approach for reducing the heating power is indicated by the dotted line:
• the heating element or at least one branch of the heating element is periodically switched on and off, resulting in a reduced average heating power applied to the drying air flow.
• the heating element or at least one branch of o the heating element is continuously provided with an electrical power corresponding to the heating power that needs to be applied to the drying air flow.
• the latter approach is particularly beneficial because it eliminates the power peaks created by the periodic switching applied in the first approach, which may be problem for the user when operating the laundry treatment apparatus 2 together with other domestic appliances.
• control unit 215 contactless water content sensor

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