EP2733257B1

EP2733257B1 - Method for operating a laundry treatment apparatus and laundry treatment apparatus

Info

Publication number: EP2733257B1
Application number: EP12192964.0A
Authority: EP
Inventors: Andrea Giovannetti; Flavio Noviello; Roberto Ragogna
Original assignee: Electrolux Home Products Corp NV
Current assignee: Electrolux Home Products Corp NV
Priority date: 2012-11-16
Filing date: 2012-11-16
Publication date: 2021-10-13
Anticipated expiration: 2032-11-16
Also published as: PL2733257T3; EP2733257A1

Description

The invention relates to a method for operating a laundry treatment apparatus and a laundry treatment apparatus having a heat pump system.
DE 10 2005 041 145 A1 discloses a laundry dryer comprising a heat pump system and a variable-speed compressor, According to an embodiment a method for operating the variable-speed compressor during a drying cycle comprises operating the compressor at the beginning of a drying cycle at high power and subsequently reducing the compressor power. The compressor power may be varied in dependency of refrigerant temperature, ambient temperature and additionally or alternatively process air temperature. For example the compressor power may be varied in dependency of a currently measured temperature, of a temperature progress over time, of specific ratios of certain temperatures and additionally or alternatively of a specific ratio of two or more temperature progresses over time.
US 2010/077787 discloses a heat pump drying machine having a normal dry mode for operating a compressor at a predetermined dry operation frequency and an energy saving dry mode for operating the compressor at an energy saving operation frequency that is lower than the dry operation frequency. A control device is provided to control an operation frequency of the compressor so that the two dry operation modes are switched to each other. Such switch is operated based on detection of a temperature signal.
EP 2 182 104 discloses a clothes dryer including a heat pump system having a motor drive unit for driving a compressor motor. The motor drive unit rotates a compressor motor in a drying processing when a result of detection by an outside temperature sensor has been determined to be larger than a first threshold. The motor drive unit rotates the compressor motor in the drying processing based on a result of setting by a second speed setting unit when the result of detection by the outside temperature sensor has been determined not to be larger than the first threshold.
EP 2 333 141 discloses a clothes dryer provided with a heat pump and drying laundry by operation of an air circulator and the heat pump, The rotational speed of a compressor is changed by controlling frequency, and the clothes dryer can be operated by selection of either a quick-drying mode for drying the laundry in a relatively short time by changing a drive frequency of the compressor or a saving mode for drying the laundry in a time longer than the time of the quick-drying mode. In the saving mode, the compressor is driven in a frequency band providing a high coefficient of performance. Compressor drive frequency is changed based on a detected temperature signal.
EP 2 455 526 discloses a clothes dryer including a heat pump system operated by an operating unit which includes a power sensor for measuring a power input to operate said compressor, and a temperature sensor for measuring a temperature of refrigerant in a continuous part of a heat pump system refrigerant guide. Compressor is operated with a power input adapted to keep said temperature at a predetermined threshold.
EP 2 284 310 discloses a clothes dryer including a heat pump system and a control unit for controlling the rotation speed of the heat pump compressor according to time development of a physical parameter of drying air stream, refrigerant and/or laundry,
It is an object of the invention to provide a method for operating a laundry treatment apparatus having a heat pump system and a laundry treatment apparatus which provide an improved drying performance,
The invention is defined in claim 1. Particular embodiments are set out in the dependent claims.
Moreover, the invention provides a laundry treatment apparatus according to claim 14.
According to claim 1, a method for operating a laundry treatment apparatus is provided, wherein the treatment apparatus may be a heat pump tumble dryer or a washing machine having a drying function. The apparatus comprises a heat pump system and a laundry treatment chamber (e.g. laundry drum) for treating laundry using process air. The heat pump system comprises a first heat exchanger (evaporator) for heating a refrigerant fluid, a second heat exchanger (condenser) for cooling the refrigerant fluid, an expansion device and a refrigerant loop, in which the refrigerant fluid is circulated through the first and second heat exchangers and the expansion device. A compressor is provided which is adapted to operate at variable speed and additionally or alternatively at variable power for circulating the refrigerant fluid through the refrigerant loop. Here and in the following, if reference to the 'speed' of the compressor is made, this means the 'rotation speed' of the compressor.
The method for operating the laundry treatment apparatus comprises detecting at least one temperature signal with the first temperature signal being indicative of the ambient or environment temperature of the laundry treatment apparatus, and the method further comprising a second temperature signal. For example at least one temperature signal may be a refrigerant temperature detected at the exit of the second heat exchanger, a temperature of electronic boards (e.g. power board, compressor control board) or a temperature detected in an inner volume within apparatus cabinet. As a further example the at least one temperature signal may be detected by means of a temperature sensor arranged internal or external the apparatus cabinet and/or a temperature sensor may be arranged in a cooling air flow path (e.g. cooling air flow for cooling the compressor). In an embodiment the temperature signal is a signal derived from two, three or more temperature sensors arranged at different locations within the dryer cabinet. The locations of the temperatures sensors or the type of temperature to be detected thereby (e.g. refrigerant or ambient temperature) are given in the present description for different examples which all are comprised here by 'temperature signal' or 'sensor'. A mathematical function may be applied to two or more detected temperature signals to calculate or determine the 'detected' temperature signal.
The method further comprises selecting a predetermined speed and/or power profile (i.e. control profile) for operating the compressor in dependency of the at least one detected temperature signal. Subsequent to selecting the control profile, the compressor is started to be operated during a laundry drying cycle by applying or executing the selected predetermined speed and/or power profile to the compressor during the drying cycle in dependency of the at least one detected temperature signal. Preferably the apparatus comprises a control unit for starting and controlling the compressor according to the speed and/or power profile as described above and below, i.e. the predetermined control profile is implemented or executed by the control unit.
Summarizing, by the above described method the operation of the compressor is adapted to the starting condition or starting state of the treatment apparatus and/or its environment by applying predetermined control profiles to the compressor. Thereby it is not necessary to continuously adapt the compressor control profile during its operation or a drying cycle, whereby a drying process with operation conditions optimized according to the starting conditions is implemented. For example a smooth running of the compressor and a fast drying process are provided that may result in an improved drying performance.
Preferably a predetermined control profile does not provide target speed and target power at the same time, i.e. either a predetermined speed profile or a predetermined power profile is executed. According to an embodiment the predetermined control profile provides a predetermined target speed for a time period and a predetermined target power for another time period different to the first time period.
In particular a predetermined control profile may provide a changing or variable target speed or target power or a change from a target speed to a target power (or vice versa), such that during the operation under the predetermined control profile there are pairs of

i) different first target speed/second target speed,
ii) first target power/second target power,
iii) first target speed/first target power,

For example there may be at least two or three cycle-types with two or three associated predetermined speed and/or power profiles, e.g. a cold cycle, a normal cycle and a hot cycle. E.g. a hot cycle is executed when the at least one detected temperature signal exceeds or reaches a predetermined threshold value, wherein the hot cycle may comprise a reduced target speed and/or power control, wherein 'reduced' means lower levels of speed and/or power as compared to a normal cycle. Thus it is taken into account that in case of initial high temperature levels of the apparatus or an environment, a reduced compressor power and/or a reduced speed is required to reach a desired operating condition. This for example takes into account that a warm-up period at the beginning of a drying cycle is shorter for a hot cycle as compared to a normal or cold cycle. The warm-up period is the period before the energy-efficient steady state or targeted operation state of the heat pump system is reached and during which the refrigerant heats up and refrigerant pressure builds up.
A cold cycle may comprise a speed 'boost' operation profile having a higher speed and/or power levels as compared to normal cycle. I.e. a predetermined control profile for a cold cycle provides that by higher compressor power and/or speed levels the warm-up period at the beginning of a drying cycle is significantly reduced as compared to applying a 'normal' cycle control profile.
Preferably the at least one temperature signal is detected only once for determining compressor control profile. In particular the at least one temperature signal is detected before starting to operate the compressor.
Preferred only the first and the second predetermined speed and/or power profiles are provided for a specific temperature or temperature range of the detected initial temperature, wherein for other temperatures or temperature ranges speed and/or power profile(s) are free. For example 'free' control profiles may be varied during a drying cycle. For example a predetermined control profile is applied only, if the detected temperature is low, such that by shortening the warm-up period the drying cycle duration may be significantly reduced.
According to the invention the at least one detected temperature signal is indicative of an ambient or environment temperature of the laundry treatment apparatus. At least one detected temperature signal may be provided by a temperature sensor capable of detecting the environment or ambient temperature at least under a predefined operation condition. E.g. it may be determined whether the apparatus is located in a high temperature environment or an environment where removal of heat from a drying cycle is hindered (e.g. due to the apparatus being located in a wall recess or the like) whereby a corresponding control profile (i.e. with reduced speed/power) may be selected to prevent e.g. emergency switch offs of the compressor due to overheating.
For example the temperature sensor may be a real ambient temperature sensor, i.e. a sensor arranged outside the apparatus housing or a sensor arranged in a cooling air passage for cooling air sucked in from the outside of the apparatus housing. Or the temperature sensor is arranged within the apparatus cabinet and is best adapted to detect a temperature corresponding to the ambient temperature (see below).
A predefined operation condition may be that the laundry apparatus was non-operative for a while. For example such that a component where the temperature sensor(s) is(are) placed is cooled down for a while by blowing ambient air to the component and/or sensor, e.g. a sensor detecting the temperature of a refrigerant or of an electronic board or of compressor motor. Then the temperature sensor detects ambient temperature only if at the location of the sensor the apparatus component or operating fluid has cooled down (equilibrated) to ambient temperature. For example when the sensor is in contact with the heat pump system or heat pump fluid that is cooled down to ambient temperature.
According to an embodiment, temperature signals of several temperature sensors arranged at different locations within and/or outside the apparatus may be received by the control unit, wherein the control unit makes a plausibility check or evaluation of the temperature signals to conclude on an ambient temperature having high likelihood. For example in case of several temperature sensors the sensor signal indicating the correct or close ambient temperature is selected. I.e. the temperature sensor with lowest temperature signal may indicate the ambient temperature which is true for sensors except under some conditions when a sensor is placed in contact with the second heat exchanger (evaporator) or expansion device.
The predetermined speed and/or power profile or all selectable predetermined speed and/or power profiles may be defined over a respective predetermined time period. For example the minimum time period for which the speed and/or power profile is predetermined is 15 min, 20 min, 30 min, 40 min, 60 min, 90 min or 120 min. Here, preferably, apart from emergency or safety interruptions there is no possibility to stop the control of compressor speed under the predetermined speed and/or power profile.
In particular the predetermined time period may be the time of a complete laundry treatment process or of one or more treatment cycles within one laundry treatment process. A treatment cycle is for example a first drying cycle for drying the laundry, wherein the speed control is not applied during an anti-crease cycle of a dryer when the laundry drying to a predefined humidity is finished.
In an embodiment, while the selected predetermined speed and/or power profile is applied to the compressor, the speed and/or power profile is not changed or modified, in particular not modified in response to a temperature change or change of another process parameter, with exception of emergency switch-off, e.g. due to overheating, and/or when a desired/selected laundry humidity is reached. I.e. after selecting a speed and/or power profile, the at least one temperature signal has no influence on the selected speed and/or power profile during its execution. Thus one temperature measurement (before compressor is activated) determines compressor operation during a predetermined length/phase of the drying cycle.
Preferably the laundry treatment apparatus comprises a control unit having an associated memory, wherein at least two or more than two predetermined speed and/or power profiles are stored in the memory for being selectively retrieved and executed by the control unit upon selection as described above and below.
The selection of the speed and/or power profile to be started is made among

(i) a first predetermined speed and/or power profile to be selected for a first temperature or temperature range of the detected temperature signal, and
(ii) at least a second predetermined speed and/or power profile to be selected for a second temperature or temperature range of the detected temperature signal, wherein the first and second speed and/or power profile are different of each other, and wherein the first and second temperature and/or the first and second temperature ranges are different of each other.

Preferably each compressor control profile is adapted to the specific requirements of the heat pump system represented by the detected temperature or temperature ranges.
Alternatively to the above embodiment, two or more speed and/or power profiles (but not all speed and/or power profiles) are predetermined. I.e. at least one speed and/or power profile is a 'free' speed and/or power profile in which controlling and/or starting conditions are predetermined, but the time behavior of the free speed and/or power profile may change in dependency of permanent or repeated detection of operation conditions (for example by constantly monitoring the temperature signal). For example when the ambient temperature (i.e. the corresponding temperature signal) is in a normal range (for example 15-30°C) a normal cycle is executed with a first predetermined speed and/or power profile. When the ambient temperature is in a low range (for example below or 15°C) a cold cycle is executed with a second predetermined speed and/or power profile. When the ambient temperature is in a hot range (for example above or 30°C) a hot cycle is executed with a third predetermined speed and/or power profile.
Preferred detecting comprises detecting the at least one temperature signal before starting the drying cycle and/or before starting to operate the compressor. For example the temperature signal is detected shortly after a 'button' for activating the drying cycle is pushed. Alternatively or additionally the temperature signal is detected after about 1 min. after starting a drying cycle or program but while the compressor is still switched-off. For example after starting a drying cycle a process air fan (which may be connected to the drum motor) and/or an optional cooling air blower (e.g. for cooling the compressor) already operates, whereby the detected temperature may be stabilized or equalized before detecting the temperature signal.
Preferably all predetermined speed and/or power profiles comprise at least two different predetermined compressor speeds at two different times during the time period of the predetermined speed and/or power profile. A predetermined speed and/or power profile comprises

(i) operating the compressor at a first speed and/or power level in a first phase, and
(ii) operating the compressor at a second speed and/or power level higher than the first speed in a second phase of the selected drying cycle subsequent to the first phase.

The compressor speed/power may increase in one step from a first constant or substantially constant speed and or power level to a second speed or power level. For example in a first operating phase the compressor is operated 5 min at 2050 rpm - to avoid too much noise from compressor until lubricant reaches operating temperature - and in a subsequent second operating phase the compressor is operated at 4000 rpm, e.g. until the heat pump system reaches a desired operating temperature.
The predetermined speed and/or power profile control may comprise operating the compressor in a third phase following the second phase at a third speed and/or power level lower than the second speed and/or power level. For example the compressor is operated after the second phase at 2500 rpm for the rest of the drying cycle, for example when the heat pump system is hot enough to operate with acceptable drying efficiency at a reduced (energy-saving) speed.
According to an embodiment the level of at least one of the first speed and/or power level, the second speed and/or power level and the third speed and/or power level is depending on the level of the detected temperature signal. E.g. when a high temperature signal is detected, i.e. when the temperature signal is above a predetermined threshold value, the apparatus or its environment has a higher initial temperature, such that the compressor may be operated at reduced power and/or speed to prevent e.g. emergency switch-offs of the compressor due to overheating.
Preferably the selection of the predetermined speed and/or power profile is additionally made in dependency of a compressor torque or power level, which is indicative for the viscosity of the compressor lubricant. E.g. when it is determined that the compressor lubricant has a high viscosity, i.e. the lubricant is cool, then the compressor may be operated at lower speed and/or power until the lubricant has operating viscosity (lower viscosity) to prevent noises and any damage of the compressor.
During execution of the selected predetermined speed and/or power profile a change from a first level of the speed and/or power defined by the selected predetermined speed and/or power profile to a second level of the speed and/or power defined by the selected predetermined speed and/or power profile is initiated or triggered by

A) laundry humidity being detected as being lower than a predetermined threshold, or
B) a second temperature signal exceeding a predefined temperature level.

For example a change from first speed or power level to second speed or power level is made when the refrigerant temperature and/or the process air temperature exceed a predefined temperature level or threshold, As a further example a change from first speed or power level to second speed or power level is made when laundry humidity is detected to be lower than a predetermined threshold. Speed/power levels are defined by the selected predetermined speed and/or power profile, wherein the first level is lower than the second level.
To determine whether a high (initial) temperature signal (i.e. a temperature detected in the hot range, for example a temperature detected above 30°C) results from a previous drying cycle or from a hot environment, the method preferably comprises: repeatedly detecting the at least one first temperature signal before starting to operate the compressor to determine a first temperature gradient of the at least one first temperature signal, wherein a first speed and/or power profile is applied to the compressor when the first temperature gradient exceeds a predetermined gradient, and wherein a second speed and/or power profile is applied to the compressor when the first temperature gradient is below the predetermined gradient. The first and the second speed and/or power profiles may be different one another.
For example, the temperature signal may be detected at least two times, for example before and after starting a drying cycle (wherein a process air fan already starts operating) but before the compressor is operated, such that the ventilation of the blower (e.g. process air blower and/or cooling air blower) balances temperature of the location where temperature is detected. When the first signal is higher than the second signal, i.e. the temperature gradient is negative, the temperature signals indicate that the treatment apparatus is located in an environment that is colder than the detected temperature, such that the above described cold cycle, hot cycle or normal cycle is executed. Preferably the cycle to be executed is chosen by the control unit, among a plurality of predetermined cycles, upon estimation of actual environment (ambient) temperature based on temperature signals and/or temperature signals difference and time elapsed between two subsequent temperature measurements by an appropriate algorithm. If a small temperature difference between the temperature signals is detected, i.e. the corresponding gradient is almost zero,
a hot or high temperature environment is indicated. Consequently a hot cycle is executed, in that a corresponding predetermined speed/power profile is applied to the compressor.
In an alternative or additional method for determining whether high (initial) temperature signal (i.e. a temperature detected in the hot range, for example a temperature detected above 30 °C) results from a previous drying cycle or from a hot environment is provided by detecting at least two temperatures of at least two spaced apart positions in the cabinet of the apparatus to determine a second temperature gradient between the at least two positions, wherein a first speed and/or power profile, selected among a plurality of predetermined cycles, is applied to the compressor when the second temperature gradient exceeds a predetermined gradient, and wherein a second speed and/or power profile, further selected among a plurality of predetermined cycles, is applied to the compressor when the second temperature gradient is below the predetermined gradient. E.g. if the detected temperatures are almost the same, i.e. the temperature gradient is almost zero, an initial high temperature signal results from a hot environment, such that a hot cycle is executed. In turn when at least one of the detected temperature signals is higher than the other temperature signals, a cold environment may be indicated. For example the initial high temperature of e.g. a sensor arranged at the heat pump system results from a previous drying cycle but but not from a high temperature environment.
Preferably the value or level of at least one of the first temperature gradient and the second temperature gradient is depending on one or more of the following: an operation state of the laundry treatment apparatus, an operation state of the heat pump system, a program cycle, a selected program for laundry treatment, and a user input or selection input by a user of the laundry treatment apparatus.
At least one of the at least two detected temperature signals may correspond to a temperature detected at one of the following positions in the heat pump system or within the cabinet of the laundry treatment apparatus: a refrigerant fluid outlet position at the first or second heat exchanger, an electronic board or inverter position of an electronic board or inverter controlling a component of the heat pump system, an electronic board or inverter position of an electronic board or inverter controlling a motor for driving the laundry treatment chamber being a drum, a refrigerant fluid outlet position at the compressor, the compressor, the expansion device, a position in a cooling air flow path (where e.g. the cooling air blown by a cooling air blower flows), or a position in the air flow of the process air. Additionally at least one temperature sensor may be arranged outside the treatment apparatus cabinet to detect an ambient or environment temperature instantly.
A laundry treatment apparatus, in particular heat pump tumble dryer or washing machine having a drying function is provided, wherein the apparatus comprises a heat pump system, a control unit adapted to control the operation of the heat pump system and a laundry treatment chamber for treating laundry using process air. The heat pump system comprises a first heat exchanger for cooling a refrigerant fluid, a second heat exchanger for heating the refrigerant fluid, an expansion device, a refrigerant loop, in which the refrigerant fluid is circulated through the first and second heat exchangers and the expansion device, a compressor for circulating the refrigerant fluid through the refrigerant loop, wherein the compressor is adapted to be operated at different compressor speeds and/or different compressor powers under the control of the control unit. The laundry treatment apparatus comprises a process air channel guiding the process air outside the laundry treatment chamber, wherein the process air channel includes different sections, including a section forming a battery channel in which the first and second heat exchangers are arranged, and further comprises at least one temperature sensor for detecting a temperature signal indicative of an ambient or environment temperature of the laundry treatment apparatus, wherein the control unit is adapted to implement a method according to any of the above described embodiments.
According to an example which is not part of the invention as defined by the claims, a method for operating a laundry treatment apparatus is provided, in particular a heat pump dryer or washing machine having dryer function, wherein the apparatus comprises a heat pump system and a laundry treatment chamber for treating laundry using process air, and wherein the heat pump system comprises: a first heat exchanger for heating a refrigerant fluid, a second heat exchanger for cooling the refrigerant fluid, an expansion device, a refrigerant loop, in which the refrigerant fluid is circulated through the first and second heat exchangers and the expansion device, and a variable speed and/or variable power compressor for circulating the refrigerant fluid through the refrigerant loop, wherein at least one compressor speed value generates at least one vibration or sound resonance in the treatment apparatus.
The method provides operating the compressor at a first speed value, which is below the resonance speed value or below one of the resonance speed values, the method further provides operating the compressor at a second speed value, which is above the resonance speed value or above the one of the resonance values, and the method further provides increasing the compressor speed in one step from the first speed value to the second speed value or decreasing the compressor speed in one step from the second speed value to the first speed value. By increasing or decreasing the compressor speed in one step an instantaneous or almost instantaneous change of speed is generated, which provides or has the result that the compressor is operated at the resonance frequency for a minimum time period. Thereby no or almost no vibration or sound resonance is generated while increasing/decreasing compressor speed.
Resonance frequencies of the apparatus may comprises resonances of (individual) components of the apparatus, i.e. the compressor, elements thereof and/or components connected/attached to the compressor. An initial speed or first speed may be zero or may be a predetermined minimum operating speed at which the compressor operates effectively, or may be a lower operating speed. The second speed may be a target speed, i.e. a speed level at which the compressor is continuously operated during the (whole or for a given time period of the) drying cycle.
According to an alternative example which is not part of the invention as defined by the claims, a method for operating a variable speed compressor in an apparatus is provided, wherein during operation the compressor causes resonance vibrations or resonance sound at one or more speed values of the compressor, which are resonance speed values, wherein the method comprises increasing the compressor speed from a first speed value to a second speed value or decreasing the compressor speed from the second to the first speed value, wherein, if the speed interval between the first and second speed value covers one or more of the resonance speed values, the speed increase or decrease is made in one step between a lower limit speed value and an upper limit speed value, wherein for each one of the resonance speed values the lower limit speed value is a speed value less than the respective resonance speed value and the upper limit speed value is a speed value higher than the respective resonance speed value. Thus, as described above, it is provided that the compressor is operated at the resonance speed only a minimum time period, such that resonances, i.e. noises and vibrations, during compressor operation are avoided or at least minimized.
Preferably the gradient of the compressor speed change between the lower limit speed value and the upper limit speed value is higher than the gradient used for changing the speed from the first to the second or from the second to the first speed value outside the region or regions between the respective lower and upper speed limit values. I.e. even if a 'step' speed change is applied, physically there is a short time for accelerating and decelerating the compressor over the resonance frequency. The ratio between the gradients may be at least 2, 3, 4, or 5. By increasing the gradient of speed increase/decrease (preferably increasing the gradient to the physically achievable gradient of increase/decrease achieved by a speed jump around the one or more resonance frequency speeds) the 'swinging in' around the resonance is too short for developing the resonance phenomena (vibration and/or noise).
Preferably the height of a step or the difference between the first speed value and the second speed value determines the time of operating the compressor at the first speed value. E.g. when the step is high, i.e. the speed difference is high or large, the compressor is operated prior to the high step a longer time at the first speed value, in comparison to a small speed step. I.e. the higher the step between a preceding speed value and a successive speed value the longer the time for operating the compressor at the preceding speed value.
Preferably the method comprises decreasing compressor speed in one step from the second speed value to the first speed value or to an end speed value, wherein the end speed value is below the at least one resonance speed value. E.g. an end speed value may be a minimum speed value at which the compressor operates efficiently or may be zero, i.e. the compressor is switched-off.
Preferably at least two resonance speed values of the compressor exist or are arranged between the first and second speed value or end speed value. I.e. more than one resonance frequency may be skipped in one step, whereby time is saved while increasing compressor speed to a desired target speed.
Alternatively or additionally to the speed jumps or increased gradients as described in the paragraphs above, in case of operating the compressor at a target speed and/or target power which results in operating it at a resonance speed, the control unit of the apparatus or the controller of the compressor provides operating the compressor at an adjusted target speed or adjusted speed under target power which is somewhat higher or lower than the resonance speed (the originally intended target speed or speed at target power). Thereby resonance operation of the compressor is avoided.
Any of the above described features and elements of the methods of operating a treatment apparatus may be combined in any arbitrary combination and may be implemented in a heat pump laundry dryer or heat pump washing machine having drying function as described above. For example the predetermined speed and/or power profiles at the same time involve the resonance-avoiding speed-change or speed adjustment operation method.
Reference is made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying figures, which show:

Fig. 1: a schematic view of a laundry treatment apparatus having a heat pump system,
Fig. 2: a schematic block diagram of components of the apparatus of Fig. 1,
Fig. 3: an exemplary flow chart showing how compressor control profiles are selected,
Fig. 4: a diagram schematically illustrating two exemplary compressor control profiles,
Fig. 5: a diagram illustrating a specific example of a compressor control profile according to the invention in comparison to a prior art control profile,
Fig. 6: a diagram illustrating a specific example of a compressor power profile,
Fig. 7a-b: flow charts illustrating how to evaluate whether a high detected temperature signal is due to ambient conditions or to what the heat pump system has performed before the temperature detection, and
Fig. 8: a diagram showing a compressor control profile according to a further embodiment.

Fig. 1 depicts in a schematic representation of a laundry treatment apparatus 2 which in this embodiment is a heat pump tumble dryer. The tumble dryer having a cabinet 3 or housing comprises a heat pump system 4, including in a closed refrigerant loop 6 in this order of refrigerant flow B: a first heat exchanger 10 acting as evaporator for evaporating the refrigerant R and cooling process air, a variable speed/variable power compressor 14, a second heat exchanger 12 acting as condenser for cooling the refrigerant R and heating the process air, and an expansion device 16 from where the refrigerant R is returned to the first heat exchanger 10. Together with the refrigerant pipes connecting the components of the heat pump system 4 in series, the heat pump system 4 forms a refrigerant loop 6 through which the refrigerant R is circulated by the compressor 14 as indicated by arrow B. If the refrigerant R in the heat pump system 4 is operated in the transcritical or totally supercritical state, the first and second heat exchanger 10, 12 can act as gas heater and gas cooler, respectively.
The expansion device 16 is a controllable valve that operates under the control of a control unit 30 (Fig. 2) to adapt the flow resistance for the refrigerant R in dependency of operating states of the heat pump system 4. In an embodiment the expansion device 16 may be a fixed, non-controllable device like a capillary tube.
The process air flow within the treatment apparatus 2 is guided through a compartment 18 of the treatment apparatus 2, i.e. through a compartment 18 for receiving articles to be treated, e.g. a drum 18. The articles to be treated are textiles, laundry 19, clothes, shoes or the like. In the embodiments here these are preferably textiles, laundry or clothes. The process air flow is indicated by arrows A in Fig. 1 and is driven by a process air blower 8 or fan. The process air channel 20 guides the process air flow A outside the drum 18 and includes different sections, including the section forming the battery channel 20a in which the first and second heat exchangers 10, 12 are arranged. The process air exiting the second heat exchanger 12 flows into a rear channel 20b in which the process 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 (which is the loading opening of the drum) is filtered by a fluff filter 22 arranged close to the drum outlet in or at the channel 20.
When the heat pump system 4 is operating, the first heat exchanger 10 transfers heat from process air A to the refrigerant R. By cooling the process air to lower temperatures, humidity from the process air condenses at the first heat exchanger 10, is collected there and drained to a condensate collector 26. The process air which is cooled and dehumidified after passing the first heat exchanger 10 passes subsequently through the second heat exchanger 12 where heat is transferred from the refrigerant R to the process air. The process air is sucked from exchanger 12 by the blower 8 and is driven into the drum 18 where it heats up the laundry 19 and receives the humidity therefrom. The process air exits the drum 18 and is guided in front channel 20d back to the first heat exchanger 10. The main components of the heat pump system 4 are arranged in a base section 5 or basement of the dryer 2.
The dryer 2 comprises a temperature sensor 28 for monitoring or detecting a temperature of the refrigerant R (or of a temperature dependent on the refrigerant temperature) at the compressor output to provide a temperature signal for the control unit 30. In this embodiment the dryer 2 comprises an additional temperature sensor 27 preferably arranged inside the cabinet 3 designed to detect the ambient temperature. The 'ambient' temperature is a measure for the temperature of the environment where the dryer 2 is placed. For example when the dyer is placed indoor, the ambient temperature is indoor temperature or when the dryer is placed outdoor (e.g. in a garage or a veranda) the temperature is or is close to outside temperature. Sensor 27 may be placed external to the cabinet 3, but is preferably internal to it and arranged at a position such that at least at specific conditions the ambient temperature can be detected. As indicated in Fig. 1, sensor 27 may be placed in an upper region of dryer, for example at or close to the input panel 38. This position is distant to the heat sources or heated components (where the process air flows) and measures a temperature close to the external temperature. Alternatively, sensor 27 is placed in the bottom of the cabinet 3, for example in the air path of the cooling air C sucked in by the blower 24 such that (at least after operating the blower 24 for a short time) the detected ambient temperature is directly related to the 'external' temperature.
As shown in Fig. 2 a further temperature sensor 29 is provided to monitor or detect the temperature of an electronic board of the control unit 30, which provides a further temperature signal for the control unit 30. Alternatively only one temperature sensor is provided, e.g. sensor 28.
Examples for locations for temperature sensors are: a refrigerant fluid outlet of the first or second heat exchanger 10, 12, an electronic board or inverter position of an electronic board or inverter controlling a component of the heat pump system 4, an electronic board or inverter position of an electronic board or inverter controlling the drum motor 32, a refrigerant fluid outlet position at the compressor 14, the compressor 14, the expansion device 16 or a position in the air flow A of the process air. I.e. one or more temperature sensors are positioned such that an operating state of the heat pump system 4 may be derived or deduced from the detected temperature or from a combination of temperature signals of two or more temperature sensors. In the following temperature detection is described in more detail as an example.
An optional cooling air blower 24 or fan unit is arranged close to the compressor 14 to remove heat from the compressor 14, i.e. from the heat pump system 4, during a drying operation. The cooling air flow C is taking heat from (the surface of) the compressor 14. The air blower 24 comprises a blower or fan 36 which is driven by a fan motor 34 controlled by the control unit 30 of the dryer 2. As indicated in Fig. 1, the cooling air C is sucked in at the bottom of the cabinet 3 and conveyed towards the compressor 14 for compressor cooling. The cooling air (at least partially passed over the compressor) exits the cabinet 3 through openings at the cabinet bottom and/or rear wall. By transferring heat from the compressor 14, during operation of the heat pump system 4, the refrigerant is shifted to optimized thermodynamic conditions for the heat exchanges processes between the closed loops of the process air loop and the refrigerant loop 6. Alternatively no fan unit is provided.
Fig. 2 shows a schematic block diagram of components of the dryer of Fig. 1 illustrating the control of the dryer components. The control unit 30 is adapted to control the operation of the components of the dryer 2, i.e. the drum motor 32, the compressor 14, the valve 16 (optionally) and the fan motor 34, according to the selected program. Via an input panel 38 a user may select a drying program or cycle, e.g. FAST, ECONOMY, IRON-AID. Optionally further inputs may be made, e.g. residue humidity, laundry amount or laundry type. Further, the control unit 30 is adapted to control the air blower 24 and the compressor 14 (speed and/or power) such that during the heat pump 4 warm-up period and the following normal operation period the operation conditions of the heat pump system 4 can be optimized in view of energy consumption / drying duration / drying result / component's lifetime.
Fig. 3 shows a flow chart illustrating an exemplary method for operating a treatment apparatus 2 as described above. Before starting to operate the compressor 14, a temperature signal Tx is detected, e.g. from temperature sensor 28 at the compressor exit. When the temperature signal is below a first threshold temperature, e.g. 15°C, the dryer 2 or the heat pump system 4 is considered to be in a 'cold' state or condition, wherein depending on the level of the detected temperature signal Tx a corresponding predetermined compressor control profile ('cold cycle') is selected and applied to the compressor 14 via control unit 30. The selected predetermined control profile may be a predetermined compressor power profile or a compressor speed profile or a combination of predetermined power and speed profile, e.g. as described below with respect to Figs. 4, 5 and 7.
If the detected temperature signal Tx is above a second threshold temperature, e.g. 30°C, the dryer or heat pump system 4 is regarded to be in a 'hot' state or condition. Depending on the level of the detected temperature signal Tx a corresponding predetermined compressor control profile ('hot cycle') is selected and applied to the compressor via control unit 30. The respective control profiles may be stored in a memory of the control unit 30 which may be adapted to select the control profiles as described above and below.
If the detected temperature signal Tx is between the two threshold temperatures the dryer or heat pump system is regarded to be in a normal state or condition, i.e. a corresponding power/speed control profile is applied to the compressor 14. In the control unit memory there may be provided one, two, three (as depicted in Fig. 3) or more predefined compressor control profiles for the cold cycle and/or for the hot cycle, which for example are defined for specific temperature ranges. In an embodiment temperature ranges and associated predetermined speed and/or power profiles may also be provided for the 'normal operation' .
Returning to Fig. 3, as an example the detection of 'cold cycle' provides for the temperature ranges (all below 15°C) T1-T2 cold profile 1), T2-T3 cold profile 2), and below T3 cold profile 3). As an example the detection of 'hot cycle' provides for the temperature ranges (all above 30°C) T4-T5 hot profile 1), T5-T6 hot profile 2), and above T6 hot profile 3).
As described above, a predetermined speed/power profile for operating the compressor 1 is selected in dependency of a temperature signal before the compressor 14 starts to operate, e.g. even before a drying cycle is started. For example after the selection of the predetermined control profile, the compressor 14 is operated for the (predetermined) length of the control profile without being further adapted to a temperature change of the temperature signal Tx.
Fig. 4 shows exemplary schematic compressor speed control profiles i), ii) for the above described 'cold' state (i) and 'hot' state (ii) of the heat pump system 4.
Tests in climate chamber at 12°C and 5°C evidenced very long cycle duration for ECONOMY cycle, where the variable speed compressor 14 is driven at 2050 rpm for all cycle. For example a load of 4.5 kg of cotton with an initial humidity of 50% is dried in 110 min at 23°C but it needs one hour more (170 min) when the ambient temperature is 5°C, i.e. in a 'cold' condition or environment. To overcome this disadvantage of long drying duration, a speed profile is applied to the compressor which is a little more expensive from energy point of view, but obtains an improvement on cycle duration.
Returning to Fig. 4, when the heat pump system 4 or the dryer 2 is cold, i.e. has a temperature below a predetermined threshold value as described above, the selected compressor speed profile comprises a first phase tla-tlb where the compressor 14 is operated at a first speed level sp1a to avoid too much noise from the compressor 14 until the compressor lubricant reaches operating temperature. The length of the first phase or time may be predetermined or may depend on other parameters which indicate the viscosity of the lubricant, e.g. the heat pump refrigerant temperature, compressor motor torque or compressor power. The length of the first phase or time may depend on a parameter indicating the status of a drying process, such as the residual humidity in the laundry.
After the first phase, the compressor speed is accelerated to a second speed level sp1b, which is in this embodiment maintained throughout the remaining drying cycle.
By increasing compressor speed from speed level sp1a to splb the heat pump system 4 soon reaches acceptable operating temperature, which is very useful especially with low loads. I.e. despite a cold environment or cold state of the heat pump system 4 the heat pump system 4 reaches in minimum time operating temperature required to efficiently dry laundry 19.
Alternatively the predetermined speed profile ends prior to the drying cycle end (compare 'hot' speed profile), wherein after the end of the speed profile the compressor 14 is controlled by the control unit 30 e.g. in dependency of process air temperature. For example the compressor 14 is operated such that a predetermined process air temperature for drying laundry 19 is maintained in the drum 18 until a (predetermined or selected) final laundry humidity is reached.
The schematically depicted 'hot' speed profile of Fig. 4 shows how the compressor 14 is controlled when a 'hot' state or condition of the apparatus 2 or its environment is determined. In contrast to 'cold' speed profile the compressor 14 is operated or switched-on at a later point in time t2a of the drying cycle, thereby it is prevented that the compressor 14 might have to be (repeatedly) switched off due to overheating. In the phase when the compressor is switched off, the process air blower 8 continues to operate and preferably the drum 18 is rotated such that by the process air A the evaporator 10 heats up and the condenser 12 cools down. By the heat losses of the system (no ideal insulation) heat is taken away from the heat pump system 4 such that the compressor 14 can be restarted. In an embodiment heat loss is assisted by operating the optional blower 24 for removing heat by cooling the compressor.
In the improved control sequence according to the predetermined profile shown in Fig. 4, further the compressor is operated in the first phase at a lower speed level sp2a and for a shorter time in comparison to 'cold' speed profile. I.e. as the heat pump system is already 'pre-heated' due to the detected hot state, less energy is required to provide e.g. that the compressor lubricant reaches operating temperature.
After the first phase compressor speed is increased to a second speed level sp2b, which is lower than the second speed level splb of the above 'cold' profile. Thereby it is also prevented that the compressor 14 may be (emergency) switched off due to overheating of the heat pump system 4. In contrast to above 'cold' speed profile the 'hot' speed profile ends prior to the end of the drying cycle, i.e. the compressor 14 may be switched off. Alternatively the compressor 14 may be operated after t2c at a minimum speed specific to the particular compressor type.
Fig. 5 shows a diagram illustrating a further example of a compressor speed control profile I according to the invention in comparison to a constant speed profile II. In a first phase of speed control profile I the compressor 14 is operated 5 minutes at 2050 rpm to avoid too much noise from the compressor until the lubricant reaches operating temperature. In a second phase the compressor 14 is still operated at a first speed level of 4000 rpm until condenser exit temperature reaches a predetermined temperature, e.g. 40°C. The second step allows the heat pump system 4 to reach soon an acceptable operating temperature. This is very useful especially with low loads. In a subsequent third phase compressor speed is reduced to 2500 rpm for the rest of the drying cycle.
When the heat pump system 4 is hot enough to work with an acceptable drying efficiency compressor speed is reduced to an intermediate level (not the 2050 of standard ECONOMY cycle) needed to carry on the cycle within a certain time even with low ambient temperature. In particular at the beginning of cycle (i.e. when the compressor 14 is switched off) the condenser exit temperature is evaluated. If it is lower than a 'cold cycle' threshold (e.g. 15°C) as described above the new profile I is applied to the compressor 14, otherwise it may be driven with the normal ECONOMY profile.
As depicted in Fig. 5 a drying cycle performed with constant speed profile II reaches barely 30°C, while the compressor speed profile I according to the invention stays over 40°C for a while in the same time. This allows the duration of a cycle to be reduce of an amount ranging from 39 minutes to 48 minutes.
Summarizing, with the speed target profile I for the compressor 14 an acceptable operating temperature of the heat pump system may be reached in minimum time, whereby the compressor, i.e. the heat pump system 4, works better and cycle duration is reduced.
According to an embodiment, when a 'cold cycle' is determined via an ambient temperature measurement, in addition to the compressor speed profile, also temperature thresholds may be determined for adjusting compressor speed while the speed profile is running. I.e. the speed level of the first, second and (optionally) third phase may be adapted to the present requirement or state of the dryer 2 or heat pump system 4, for example as described with respect to Fig. 4. Thus the drying cycle may be adapted to receive an optimum drying result and a minimum drying duration.
A similar speed and/or power profile concept of adjusting compressor speed/power target is applied in case of starting a drying cycle in a hot or high temperature condition. A high temperature measured at the cycle start may indicate that the machine is installed on a hot environment, or that it has just finished a drying cycle or that a cycle was just interrupted and another one (or the same) has been restarted.
When the machine is installed in a hot environment, or if it performs consecutive cycles on an environment that does not allow enough heat exchange from the machine, it is very probable that the compressor operation should be suspended by the software to avoid overpressures on the heat pump circuit (which is detected in an indirect way through the temperature of condenser exit). Every time this temperature exceeds a configured threshold (e.g. 70°C) the compressor 14 may be switched off for 5 minutes to allow internal pressures to decrease at a reasonable level. As mentioned above, the process air blower 8 and drum rotation are further applied and optionally the cooling air blower 24 is activated or is operated continuously (further operated) while compressor is switched off.
This phenomenon is very evident on a drying cycle with the 'FAST' option selected by the user, where the compressor is driven at a very high fixed power (e.g. 750 W). According to an embodiment when a fast cycle is performed in 'hot conditions' the compressor power target is decreased to avoid too much compressor switches off. I.e. comparable to above example shown in Fig. 4, where compressor speed level is reduced due to 'hot' conditions, compressor power may also be reduced due to a high temperature state of the apparatus or of its environment.
A specific example for reducing compressor power as described above is shown in Fig. 6, which illustrates the difference between a compressor speed profile for a 'normal' FAST drying cycle at 750 W, i.e. in a normal (ambient) temperature e.g. -15-30°C, and a 'hot' FAST drying cycle at 600 W, where a hot or high temperature state of the apparatus 2 or its environment has been detected as described above (the sensor provides detected signal Tx). Further the compressor speeds corresponding to the respective FAST drying cycles are depicted, showing that due to the reduced target power in the 'hot' drying cycle the compressor speed is also significantly reduced, whereby compressor switch offs due to overheating are prevented.
Fig. 7a-b show flow charts of two different embodiments for evaluating whether a high detected temperature Tx (i.e. a temperature detected in the hot range, for example a temperature detected above 30°C) is due to ambient conditions or is due to operating conditions of the heat pump system which were applied before the current temperature detection and resulted in the detection of the high temperature (e.g. starting a drying program immediately or shortly after a previous drying process).
As shown in Fig. 7a an initial (high) temperature of Tx is T1 (at time t0) which is measured or detected just when the machine is switched on or a drying program is selected (at that time none of the treatment apparatus components like compressor 14 or blower 8 is activated). The temperature signal Tx may be measured through an NTC or temperature sensor installed in or at the heat pump system 4 (for example sensor 28 at the compressor outlet), wherein any temperature sensor placed at other places of the apparatus 2 could be used for the same purpose. Another example would be one or more temperature sensors mounted on electronic boards, e.g. a power board and a compressor control board. Subsequently the drying cycle is started which in this cycle means that the drum motor 32 rotates the drum 18 and the connected process air fan 8 for circulating air A. After a predetermined time from the start of the drying cycle (e.g. 1 min) the compressor 14 is still switched off and the temperature measurement is repeated to obtain a second temperature signal Tx = T2 (at time point t1 > t0).
Then the two temperatures T1, T2 are compared. When the first (high) temperature signal T1 is higher than the second temperature signal T2 then the treatment apparatus 2 is located in an environment that is colder than the detected temperature T1, T2. The ventilation effect of the fan 8 leveled the high temperature signal T1 to the lower temperature level T2 of the apparatus environment. For example the high temperature signal T1 results from a previous drying operation of the apparatus 2, but not from a generally high temperature (ambient) environment of the dryer 2. The actual (ambient) environment may be estimated from detected temperatures T1, T2 and/or temperature difference T1-T2 and time elapsed between two subsequent temperature measurements by an appropriate algorithm. The control unit selects the compressor control profile to be carried out based on the (ambient) environment temperature estimated by such algorithm. The control profile selection is performed among a plurality of predetermined control profiles.
When the first temperature signal T1 is the same or less than the second temperature signal T2, then the dryer 2 is located at a high temperature environment or in an environment which does not allow sufficient removal of heat from the dryer, e.g. the dryer 2 is located in a small compartment or room. In other words it is determined that the ventilation effect due to the fan 8 gave no results in term of temperature decrease after a sufficiently long period of fan operation. The control unit selects compressor control profile based on detected temperature T1 or T2.
As shown in Fig. 7b three temperature sensors are available to detect three temperature signals Ta, Tb, Tc (at the same time) at three different positions. For example temperature sensor 28 at the refrigerant circuit, temperature sensor 27 at the upper or lower region of the cabinet 3 (see above), and a temperature sensor on the compressor control board. Sensor 28 may be in the machine basement 5, and the compressor control board is in a region over the basement 5.
The detected temperature signals Ta, Tb, Tc are compared to determine whether they are essentially the same, i.e. whether the temperature values vary within a predetermined range ΔT ≤ ΔT1 threshold. If the detected (high) temperature signals are essentially the same, the high temperature is due to the high temperature ambient condition. If one or more of the temperature sensors (in particular sensor 28) detects a completely different temperature, i.e. ΔT > ΔT1 threshold then the initial high temperature probably results from a previous drying cycle. In this case the ambient temperature may be normal (e.g. in the range of 15 to 30°C) or cold (e.g. below 15°C). In particular it is checked whether the temperature difference ΔT is below a further predetermined threshold ΔT2_threshold > ΔT1 threshold such that it is concluded that there is a normal environment (normal range of ambient temperature). Otherwise (ΔT > ΔT2_threshold) it is a cold ambient temperature. The control unit 30 selects the appropriate predetermined speed and/or power profile. The difference temperature ΔT may be a complex or simple function of the temperature signals Ta, Tb, Tc (ΔT = f(Ta, Tb, Tc) or only a function of two of the temperature signals.
It has been observed that the compressor 14 has particular resonance speeds that may cause mechanical noise during operation which may induce a user to think that something is wrong/broken with the treatment apparatus 2 or an annoying noise is generated. Amongst others such noises may be due to resonances of compressor components, heat pump components or components mechanically coupled to the compressor, due to possible refrigerant phase changes (from gas to liquid) and/or due to a change of refrigerant pressure when the compressor target speed changes.
In the following a control procedure for changing the rotation speed of the compressor or for adjusting to a new rotation speed of the compressor under avoiding or reducing resonance vibration and/or noise is disclosed. This procedure is preferably used in combination with the selection of the above predetermined speed and/or power profile of the compressor to avoid resonances. However, this procedure is also applicable independent of the above speed and/or power control. In case of power target control, i.e. if the compressor is to be operated with a predefined target power, the control unit can monitor the rotation speed of the compressor and in response thereto, the control unit can (for example temporarily) adjust the target power to a slightly higher or lower target power to avoid resonance. It is to be noted (compare Fig. 6) that the compressor speed depends on the target power as well as on the current operation state (e.g. refrigerant temperature) of the heat pump system 4 so that either in the current constant operation or in the current transient operation (warm-up phase) the rotation speed may correspond to the or one of the resonance speeds.
Fig. 8 shows a schematic diagram exemplary illustrating a compressor control profile according to a further embodiment. As shown in the example of Fig. 8 the compressor 14 may comprise three resonance speeds rsp1, rsp2 and rsp3. To avoid operating the compressor 14 at these speeds, according to curve X the target speed is increased from zero (or any initial speed value) in a step-like manner so as to pass quickly through the resonance speeds.
In a first phase the compressor 14 is operated at a first (or initial) speed level sp3a below the first resonance speed rsp1. Then compressor speed is increased step-like from the first speed level sp3a to a second speed level sp3b, whereby the resonance speed rsp1 is passed in the shortest possible time. I.e. even if a 'step' speed change is applied, physically there is a short time for accelerating/decelerating the compressor 14 over the resonance frequency, i.e. by the step-like increase of speed the compressor 14 is operated at the resonance speed rsp1 only for a minimum time, such that resonances and the corresponding noises or vibrations have no chance to build up.
The compressor 14 is operated at the second speed level sp3b e.g. until the compressor lubricant reaches operating temperature as described above. Then compressor speed is again increased in a step-like manner from the second speed level sp3b to a third speed level sp3c, whereby two other resonance speeds rsp2, rsp3 are passed. I.e. one or more resonance speeds may be passed in one step, respectively, such that in the latter case the number of steps may be reduced for reaching a final speed level sp3c.
The dashed curve Y in Fig. 8 shows an example where the compressor speed is intentionally increased as in speed ramp over time to the target speed sp4c within the given time t4c, where however the resonance frequencies rsp1, rsp2 and rsp3 are overcome in jumps of increased speed ramps under the control of the control unit 30. Instead of implementing such speed control for avoiding resonances using the control unit 30 of the dryer 2, a control board or inverter (not shown) which controls the compressor may have a controller that is programmed to provide such speed jumps or to apply a slightly higher or lower compressor speed, if the intended target speed (which is for example set by the control unit 30) corresponds to one of the resonance speeds.
According to the operation as indicated by curve Y, if during a speed increase or speed reduction the speed interval between a first and a second speed value covers one or more of the resonance speed values (rsp1, rsp2 and rsp3), the speed increase or decrease is made in one step between a lower limit speed value and an upper limit speed value (not shown in Fig. 8). For each resonance speed value the lower limit speed value is a speed value less than the respective resonance speed value and the upper limit speed value is a speed value higher than the respective resonance speed value. By increasing or decreasing the speed in this way, it is provided that the compressor is operated at the resonance speed only a minimum time period, such that resonances, i.e. noises and vibrations, during compressor operation are avoided or at least minimized.
Preferably the gradient of the compressor speed change between the lower limit speed value and the upper limit speed value is higher than the gradient used for changing the speed from the first to the second or from the second to the first speed value outside the region or regions between the respective lower and upper speed limit values. I.e. even if a 'step' speed change is applied, physically there is a short time for accelerating and decelerating the compressor over the resonance frequency. The ratio between the gradients may be at least 2, 3, 4, or 5. Maximum gradients can be achieved by up- or down-speed steps analog to the steps shown for curve X.
It is further to be noted that, due to the step-like speed control, the refrigerant can stabilize its pressure in a more efficient way without changing phase (from gas into liquid) and therefore the compressor 14 does not produce noise and it cannot be damaged by pumping liquid.
A specific example for compressor resonance speeds and corresponding operating times is shown in following Table 1:

TIME DURATION (Minutes) COMPRESSOR SPEED (rpm)

1 2050

1 2700

1 3200

5 3700

To be keep until refrigerant temperature is over a threshold 5000
A first resonance speed is located around 2300 rpm and further three resonance speeds between 4000 and 5000 rpm. The noise problem is particularly felt when the dryer runs (in normal ambient temperature conditions) a 'FAST' cycle, i.e. a cycle designed to rapidly dry laundry as described above. In that drying cycle, compressor speed may reach up to 5000 rpm to greatly short the cycle duration. Therefore all the four resonance speeds may be encountered both when the compressor speed is increased and when the speed is decreased. Thus a similar step-like speed decrement may be arranged.
This method for increasing and decreasing compressor speed may also be used with the compressor speed profiles for a 'cold' or 'hot' drying cycle as described above. For example the diagram of Fig. 5 in relation to a 'cold' cycle, a speed step may be arranged between 2050 rpm and 4000 rpm to consider the resonance present at about 2300 rpm.
Generally, when applying a predetermined speed and/or power profile, the predetermined speed control profile may be continued for example according to any of the following ways:

i) as described e.g. above for the profile (curve X) in Fig. 8 the third speed level sp3c may be maintained until the end of the drying cycle,
ii) the compressor 14 may be switched off prior to the end of the drying cycle as shown in Fig. 4,
iii) after the predetermined speed profile is completed or finished prior to drying cycle end, compressor speed may be adapted to requirements of the drying cycle (e.g. process air temperature),
iv) compressor speed may be reduced to a minimum operating speed specific for the respective compressor 14 until the drying cycle ends.

Reference Numeral List

2: heat pump tumble dryer
3: cabinet/housing
4: heat pump system
5: base section
6: refrigerant loop
8: blower
10: first heat exchanger (evaporator)
12: second heat exchanger (condenser)
14: compressor
16: expansion device
18: drum (laundry compartment)
19: laundry
20: process air channel
20a: battery channel
20b: rear channel
20c: rising channel
20d: front channel
22: fluff filter
24: cooling air blower
26: condensate collector
27: external temperature sensor
28: temperature sensor (compressor exit)
29: temperature sensor (electronic board)
30: control unit
32: drum motor
34: fan motor
36: fan
38: input panel

A: process air flow
B: refrigerant flow
C: cooling air (flow)
R: refrigerant
Tx: detected temperature signal

Claims

Method for operating a laundry treatment apparatus, in particular a heat pump dryer or washing machine having dryer function, wherein the apparatus (2) comprises a heat pump system (4) and a laundry treatment chamber (18) for treating laundry using process air (A), and wherein the heat pump system comprises:
a first heat exchanger (10) for heating a refrigerant fluid (R),

a second heat exchanger (12) for cooling the refrigerant fluid (R),

an expansion device (16),

a refrigerant loop (6), in which the refrigerant fluid is circulated through the first and second heat exchangers and the expansion device,

a variable speed and/or variable power compressor (14) for circulating the refrigerant fluid (R) through the refrigerant loop (6), and

a process air channel (20) guiding the process air (A) outside the laundry treatment chamber (18), the process air channel including different sections including the section forming a battery channel (20a) in which the first and second heat exchangers (10, 12) are arranged,
the method comprising:
detecting at least one first temperature signal indicative of an ambient or environment temperature of the laundry treatment apparatus,

selecting a predetermined speed and/or power profile for operating the compressor (14) in dependency of the at least one detected first temperature signal,

starting to operate the compressor (14) in a laundry drying cycle by applying or executing the selected predetermined speed and/or power profile to the compressor (14) during the drying cycle in dependency of the at least one detected first temperature signal,

characterized in that

the selection of the speed and/or power profile to be started is made among

a first predetermined speed and/or power profile to be selected for a first temperature or temperature range of the detected temperature signal,

at least a second predetermined speed and/or power profile to be selected for a second temperature or temperature range of the detected temperature signal,

wherein the first and second speed and/or power profile are different of each other, and

wherein the first and second temperature and/or the first and second temperature ranges are different of each other;

the predetermined speed and/or power profile comprises:
operating the compressor (14) at a first speed and/or power level (sp1a, sp2a, sp3a) in a first phase, and

operating the compressor (14) at a second speed and/or power level (sp1b, sp2b, sp3) higher than the first speed in a second phase of the selected drying cycle subsequent to the first phase, and

during execution of the selected predetermined speed and/or power profile a change from the first level of the speed and/or power defined by the selected predetermined speed and/or power profile to the second level of the speed and/or power defined by the selected predetermined speed and/or power profile is initiated or triggered by
A) laundry humidity being detected as being lower than a predetermined threshold, or

B) a second temperature signal exceeding a predefined temperature level.
Method according to claim 1, wherein the detected temperature signal is provided by a temperature sensor (27, 28) capable of detecting the environment or ambient temperature at least under a predefined operation condition.
Method according to claim 1 or 2, wherein the predetermined speed and/or power profile or all selectable predetermined speed and/or power profiles are defined over a respective predetermined time period.
Method according to any of the previous claims, wherein the laundry treatment apparatus (2) comprises a control unit (30) having an associated memory, wherein at least two or more than two predetermined speed and/or power profiles are stored in the memory for being selectively retrieved and executed by the control unit upon selection.
Method according to any of the previous claims, wherein detecting comprises detecting the at least one temperature signal before starting the drying cycle, or before starting to operate the compressor (14).
Method according to any of the previous claims, wherein all predetermined speed and/or power profiles comprise at least two different predetermined compressor speeds at two different times during the time period of the predetermined speed and/or power profile.
Method according to any of the previous claims, wherein the predetermined speed and/or power profile control comprises
operating the compressor (14) in a third phase following the second phase at a third speed and/or power level lower than the second speed and/or power level.
Method according to any of the previous claims, wherein the level of at least one of the first speed and/or power level, the second speed and/or power level and the third speed and/or power level is depending on the level of the detected temperature signal.
Method according to any of the previous claims, wherein the selection of the predetermined speed and/or power profile is additionally made in dependency of a compressor torque or power level.
Method according to any of the previous claims, wherein the method comprises:
repeatedly detecting the at least one first temperature signal before starting to operate the compressor (14) to determine a first temperature gradient of the at least one first temperature signal,

applying a first speed and/or power profile to the compressor (14) when the first temperature gradient exceeds a predetermined gradient, and

applying a second speed and/or power profile to the compressor (14) when the first temperature gradient is below the predetermined gradient.
Method according to any of the previous claims, wherein the method comprises:
detecting at least two temperatures of at least two spaced apart positions in the cabinet of the apparatus to determine a second temperature gradient between the at least two positions,

applying a first speed and/or power profile to the compressor when the second temperature gradient exceeds a predetermined gradient, and

applying a second speed and/or power profile to the compressor when the second temperature gradient is below the predetermined gradient.
Method according to any of the claims 10 or 11, wherein the value or level of at least one of first temperature gradient and the second temperature gradient is depending on one or more of the following:
- an operation state of the laundry treatment apparatus,

- an operation state of the heat pump system (4),

- a program cycle,

- a selected program for laundry treatment, and

- a user input or selection input by a user of the laundry treatment apparatus.
Method according to any of the previous claims 10 to 12, wherein at least one of the at least two detected temperature signals correspond to a temperature detected at one of the following positions in the heat pump system (4) or within the cabinet of the laundry treatment apparatus (2):
a refrigerant fluid outlet position at the first or second heat exchanger (10, 12),

an electronic board or inverter position of an electronic board or inverter controlling a component of the heat pump system (4),

an electronic board or inverter position of an electronic board or inverter controlling a motor for driving the laundry treatment chamber being a drum,

a refrigerant fluid outlet position at the compressor (14),

the compressor (14),

the expansion device (16), or

a position in the air flow (A) of the process air.
Laundry treatment apparatus, in particular heat pump tumble dryer or washing machine having a drying function, wherein the apparatus comprises a heat pump system (4), a control unit (30) adapted to control the operation of the heat pump system and a laundry treatment chamber (18) for treating laundry using process air, and wherein the heat pump system (4) comprises:
a first heat exchanger (10) for cooling a refrigerant fluid (R),

a second heat exchanger (12) for heating the refrigerant fluid (R),

an expansion device (16),

a refrigerant loop (6), in which the refrigerant fluid is circulated through the first and second heat exchangers and the expansion device,

a compressor (14) for circulating the refrigerant fluid through the refrigerant loop (6), wherein the compressor (14) is adapted to be operated at different compressor speeds and/or different compressor powers under the control of the control unit (30);

a process air channel (20) guiding the process air (A) outside the laundry treatment chamber (18), the process air channel including different sections including a section forming a battery channel in which the first and second heat exchangers (10, 20) are arranged:

at least one temperature sensor for detecting a temperature signal indicative of an ambient or environment temperature of the laundry treatment apparatus;

wherein the control unit (30) is adapted to implement a method according to any of the previous claims.