AU2011244860A1

AU2011244860A1 - Laundry drier with variable drying air flow and method for its operation

Info

Publication number: AU2011244860A1
Application number: AU2011244860A
Authority: AU
Inventors: Markus Kerschdorfer; Andre Widmer
Original assignee: V-Zug AG
Current assignee: V-Zug AG
Priority date: 2010-11-12
Filing date: 2011-10-28
Publication date: 2012-05-31
Also published as: CH701466A2; CH701466B1; EP2453055A1; CH701466A3; CN102535125A

Abstract

Abstract The air flow of the drying air in the laundry dryer can be varied. In particular, the air flow can be 5 reduced as the drying process proceeds, such that the air has enough time to take up a large amount of water from the laundry and it remains possible to extract water therefrom efficiently. Further, the user can be provided with different programs having different air flows and 10 process durations such that the duration, energy consump tion and noise generation can be chosen according to re quirements. Advantageously, the power of a heat pump (7) in the device can be adjusted depending on air flow. (Fig. 1) drum 12 1 < evaporator condenser ........... ............... cm.. o .............. ............................................. e.........=.... control unit - -0 Fig. 1

Description

Australian Patents Act 1990 - Regulation 3.2 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title Laundry drier with variable drying air flow and method for its operation The following statement is a full description of this invention, including the best method of performing it known to me/us: P/00/0 II CIAl la Technical Field 5 The invention relates to a laundry dryer with a drying air circuit, a drum arranged in the drying air circuit for receiving the laundry to be dried, a ventila tor for generating an air flow of drying air in the dry 10 ing air circuit, and a control unit for controlling the ventilator. Further, the invention relates to a method for operating such a laundry dryer. Background Art 15 In known laundry dryers the drying air in the air circuit is conveyed through the drum, which allows the laundry to be dried dried. A high air flow helps to increase the drying efficiency, but it increases energy 20 consumption and noise. Disclosure of the Invention The problem to be solved by the present in 25 vention is to provide a laundry drier and a method for its operation with improved air flow control. This aim is achieved by the independent claims. Accordingly, a control unit of the laundry drier is adapted to generate at least two different air 30 flows in the drying air circuit. Both air flows are lar ger than zero. According to the method of the present in vention the two air flows are maintained in different first and second time periods. This allows to provide a machine that is better adapted to requirements. 35 The term "at least two different air flows" is to be understood to designate two different air flows 17.10.2011 SU/web P106351AUOO.doc 2 that are unequal to zero, i.e. drying air at rest is not considered to be an air flow in the sense of the claim. Advantageously, the air flow is varied within a single drying process. 5 For example, the air flow can be set to be higher in an initial phase of the drying process and to be lower in an end phase of the same. This takes account of the fact that the laundry becomes dryer towards the end of the drying process and therefore, the humidity of 10 the drying air decreases, which makes an extraction of water from the drying air more difficult. By reducing the air flow towards the end of the process, the decrease of humidity can be compensated, such that the drying air can still be dried with high efficiency. 15 For the same reason, in another advantageous embodiment of the invention, the humidity of the laundry or of the drying air is measured by means of a humidity sensor, and the volume air flow is reduced when the hu midity decreases. 20 The laundry dryer can be equipped with a heat pump having an evaporator and a condenser in the drying air circuit, in order to extract water from and feed heat to the drying air. In this case the power of the heat pump is advantageously adjusted depending on the air 25 flow. In particular, the power of the heat pump can be reduced when the air flow is reduced. In this manner, noise can be reduced and energy consumption can be opti mized. Further, the laundry drier can comprise a 30 program selector of a known type, by means of which the user can select one of several drying programs with dif ferent operating parameters. In this case, at least two drying programs with different air flows can be provided. Upon selection of a first one of the drying programs, the 35 control unit generates a lower air flow than upon selec tion of a second one of the drying programs. The first drying program can, e.g., be used as a noise-reduced 17.10.2011 SU/web P106351AU00.doc 3 night program with lower energy consumption, while the second program provides higher speed drying. Other advantageous embodiments are listed in the dependent claims as well as in the description below. 5 The term "air flow" as used herein designates the "volume flow of the air", e.g. as expressed in m 3 per minute. Other advantageous embodiments are listed in the dependent claims as well as in the description below. 10 Brief Description of the Drawing The invention will be better understood and objects other than those set forth above will become ap 15 parent from the following detailed description thereof. Such description makes reference to the annexed drawing, which schematically shows some components of a laundry dryer. 20 Modes for Carrying Out the Invention The laundry dryer according to the enclosed figure comprises a drum 1 for receiving the laundry to be dried. The drum 1 is rotated by means of a drive 2, ad 25 vantageously in a reversing motion, i.e. the direction of the rotation is changed in a reversing rhythm in order to reduce the tendency of the laundry to become entangled. The drum 1 is arranged in a drying air cir cuit 3. In the present embodiment the air circuit is a 30 closed air circuit even though the invention can, in principle, also be used with an open air flow, in which part of the drying air is at least at intervals replaced by fresh air. In order to convey the air through the drying 35 air circuit 3, a ventilator 4 is provided. From ventila tor 4 the drying air arrives at drum 1 and from there it 17.10.2011 SU/wph P106351AUOO.doc 4 passes an evaporator 5 and a condenser 6 of a heat pump 7 and finally returns to ventilator 4. The heat pump 7 comprises a compressor 8, which pumps, in known manner, a heat pump fluid through 5 the condenser 6, an expansion valve 9, and the evaporator 5, such that condenser 6 acts as a heater and evaporator 5 as a freezer for the drying air in the drying air cir cuit 3. This allows to dry the air at the location of evaporator 5 and to heat it at the location of condenser 10 6. The operation of the device is controlled by a control unit 10. A program selector 11 is connected to control unit 10. By means of program selector 10 the user can select one of several drying programs with different 15 operating parameters. The control unit 10 controls a drying process by controlling the various components of the device, such as drive 2 of drum 1, compressor 8 and ventilator 4. As mentioned above, this allows to vary the 20 air flow in the drying air circuit 3. In the following, some examples are described. Reduction of the air flow with decreasing hu midity 25 In a particularly advantageous embodiment the air flow in the drying air circuit is reduced for in creasing dryness of the drying air and/or laundry. This is based on the understanding that efficiency of the wa ter extraction from the drying air decreases when its hu 30 midity decreases. For this reason, the air flow is advan tageously reduced when the air or laundry becomes drier, such that there is more time for the drying air to take up humidity in the drum. For this purpose, in the first embodiment, a 35 humidity sensor 12 can be provided, which measures the humidity of the laundry or of the drying air. The drying sensor 12 can, e.g., be a conductivity sensor that meas 17.10.2011 SU/web P106351AUOO.doc 5 ures the conductivity of the laundry in drum 1, or it can be a humidity gas sensor, which measures the humidity in the drying air. When control unit 10 detects a decrease of humidity the air flow is automatically reduced to a 5 lower value. In a second embodiment, however, a purely time-controlled control of the air flow is possible. In this case control unit 10 operates ventilator 4 in an initial phase of a drying process with a higher speed 10 than towards the end of the process. For example, venti lator 4 can be operated with a higher rotating speed dur ing the first 60 minutes of a drying process than during the subsequent end phase (or vice versa). The air flow, i.e. of the rotating speed of 15 ventilator 4, can be varied in stepwise manner, i.e. the air flow can take at least two different values separated by at least one step. Alternatively, the air flow can be varied continuously. 20 Special program with reduced air flow In another advantageous embodiment several drying programs can be provided, which differ in air flow. In particular, at least one program with a reduced air flow can be provided, upon selection of which venti 25 lator 4 is at least temporarily, advantageously during the whole process, operated with a lower speed than dur ing another (normal) program. In order to compensate for the reduced drying rate caused by the lower air flow, the program with the reduced air flow advantageously takes 30 longer than a regular program. A special program of this type can, e.g., be used at night because in that case the duration of the program is of minor importance. 35 Adaptation of drum speed to air flow In a further advantageous embodiment control unit 10 is designed to operate drive 2 of drum 1 depend 17.10.2011 CT /m-. P106351AUOO.doc 6 ing on the air flow. In particular, the rotating speed and/or the reversing rhythm of the drum can be adjusted depending on air flow. For example, the rotating speed can be reduced when the air flow is low, e.g. during the 5 special program with reduced air flow as described above, by means of which energy consumption and noise generation can be reduced further. Adapting the heat pump power to the air flow 10 It can be advantageous to adapt the power of the heat pump 7 depending on the air flow. During opera tion with lower air flow the power of heat pump 7 can be lower as well, as compared to the operation with higher air flow. This again allows to decrease energy consump 15 tion and noise. In other words, at least two different air flows can be maintained in the laundry drying, with a first air flow being maintained in a first time period and being larger than the second air flow maintained in a 20 second time period. In this case, during the first time period, the heat pump is operated with a larger power than during the second time period. For this reason, the drive of heat pump 7 is advantageously a "brushless DC" (BLDC) motor, whose ro 25 tating speed can be varied easily. It is, however, also possible to operate the motor in pulsed operation. Notes The above examples for programs and methods, 30 in which the air flow volume is varied, can be used indi vidually or in arbitrary combination. The amount of the variation of the air flow depends, inter alia, on the size of the device and its application. For a device with a drum volume of approxi 35 mately 110 litres the regular or normal air flow (e.g. during the above "initial phase" of a drying process or in the above "normal or regular program") can be approxi 17.10.2011 SU/web P106351AU00.doc 7 mately 250 m 3 /h. The reduced air flow (e.g. in the above "end phase" of a drying program or in the above "program with reduced air flow") can be approximately 150 m 3 /h. It is further possible to increase the air 5 flow temporarily or during certain programs, e.g. in or der to achieve a faster drying. In conclusion, the air flow of the laundry dryer can be varied. In particular, the air flow can be reduced during the course of a drying process, such that 10 the drying air can still take up a large amount of humid ity and it remains possible to efficiently extract water therefrom even towards the end of the process. Further, the user can be provided with different programs having different air flows and process durations, such that du 15 ration, heat consumption and energy consumption as well as noise generation can be chosen according to require ments. Advantageously, the power of the heat pump 7 is varied as a function of the air flow. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference numerals in the following claims do not in any way limit the scope of the respective claims. 17.10.2011 SU/web P106351AUOO.doc

Claims

1. A laundry dryer comprising a drying air circuit (3), 5 a drum (1) arranged in the drying air circuit (3) for receiving the laundry to be dried, a ventilator (4) generating an air flow of drying air in the drying air circuit (3), and a control unit (10) for controlling the ven 10 tilator (4), wherein the control unit (10). is adapted to generate at least two different non-zero air flows in the drying air circuit (3).

2. The laundry dryer of claim 1 wherein the 15 control unit (10) is adapted to vary the air flow during a drying process.

3. The laundry dryer of claim 2 wherein the control unit (10) is adapted to set the air flow to be higher in an initial phase of the drying process than in 20 an end phase of the drying process.

4. The laundry dryer of any of the preceding claims further comprising a humidity sensor (12) for measuring a humidity of the laundry or the drying air, wherein the control unit (10) is adapted to reduce the 25 air flow for decreasing humidity.

5. The laundry dryer of any of the preceding claims further comprising a program selector (11) by means of which a user can select one of several drying programs having different operating parameters, wherein 30 the control unit (10) generates a lower air flow upon se lection of a first one of the drying programs than upon selection of a second one of the drying programs.

6. The laundry dryer of claim 5 wherein the first drying program is running longer than the second 35 drying program.

7. The laundry dryer of any of the preceding claims further comprising a heat pump (7) and wherein the

17.10.2011 CT1 , / P10%k1 ATUJdner 9 heat pump (7) comprises an evaporator (5) arranged in the drying air circuit (3) and a condenser (6) arranged in the drying air circuit (3), and wherein the control unit (10) is adapted to adjust a power of the heat pump (7) as 5 a function of the air flow. 8. The laundry dryer of any of the preceding claims further comprising a rotational drive (2) for the drum, wherein the control unit (10) is adapted to adjust a rotation speed and/or a reversing rhythm of the drum 10 (19) as a function of the air flow. 9. A method for operating the laundry dryer of any of the preceding claims comprising the steps of maintaining a first air flow larger than zero in the drying air circuit (3) at a first time period, and 15 maintaining a second air flow larger than zero and different from the first air flow at a second time period, wherein the second time period is different from the first time period. 10. The method of claim 9, wherein the air 20 flow in an initial phase of a drying process is higher than in and end phase of the same drying process. 11. The method of any of the claims 9 or 10, comprising the step of measuring a humidity of the laun dry to be dried or of the drying air and reducing the air 25 flow for decreasing humidity. 12. The method of any of the claims 9 to 11 wherein the laundry dryer comprises a heat pump (7), wherein the heat pump (7) comprises an evaporator (5) ar ranged in the drying air circuit (3) and a condenser (6) 30 arranged in the drying air circuit (3), and wherein a power of the heat pump (7) is reduced for a decreasing air flow. 13. The method of any of the claims 9 to 12, wherein the laundry dryer comprises a heat pump (7), 35 wherein the heat pump (7) comprises an evaporator (5) ar ranged in the drying air circuit (3) and a condenser (6) arranged in the drying air circuit (3), wherein the air 17.10.2011 IT / wDh P1IA'Ac1l A rie- 10 flow in the first time period is higher than the air flow in the second time period, and wherein the heat pump (7) is operated with a larger power during the first time pe riod than during the second time period. 5 17.10.2011