Method for controlling a laundry drying machine

Abstract

A method for controlling a laundry drying machine having a laundry treating chamber and a control unit which receives a signal indicative of laundry moisture from a moisture sensor. The method includes receiving a user input of a laundry treating program, and, in the machine initialization phase, comparing the laundry moisture indicated by the signal to a first threshold, which is stored in the control unit and is indicative of dried laundry or empty threating chamber. If the signal is determined to be equal or less than the first threshold, one or more of the following actions is performed: carrying out only a portion of the selected laundry treating program; skipping the program main phase; starting the program final phase; stopping the laundry treating program; providing a notification of dried laundry and/or empty treating chamber.

Claims

1. A method for controlling a laundry drying machine comprising a treating chamber adapted to contain laundry to be treated and a control unit configured to receive a signal (S.sub.m) indicative of laundry moisture from a moisture sensor, the method comprising: receiving, at the laundry drying machine, a user selection of a laundry treating program comprising a machine initialization phase for detecting physical parameters of the laundry and/or of the laundry drying machine, a program main phase for tumbling the laundry while a heater is ON, and a program final phase for tumbling the laundry while the heater is OFF; performing a machine initialization phase including comparing the laundry moisture indicated by the signal (S.sub.m) to a first threshold (THR.sub.1), which is stored in the control unit and is indicative of dried laundry or an empty treating chamber; and upon determining that the signal (S.sub.m) is equal to or less than the first threshold (THR.sub.1), maintaining the heater OFF while performing one or more of the following: skipping the program main phase by not performing the program main phase and by starting the program final phase, and stopping the laundry treating program by not performing the program main phase and not performing the program final phase.

2. The method according to claim 1, further comprising: comparing the laundry moisture indicated by the signal (S.sub.m) to a second threshold (THR.sub.2), which is stored in the control unit and is indicative of an empty treating chamber; and upon determining that the signal (S.sub.m) is equal to or less than the second threshold (THR.sub.2), determining that the treating chamber is empty.

3. The method according to claim 2, further comprising, upon determining that the treating chamber is empty, performing only one or more of: stopping the laundry treating program; and providing a notification of empty treating chamber.

4. The method according to claim 2, wherein the machine initialization phase further comprises estimating the quantity/weight and/or type of the laundry in the treating chamber.

5. The method according to claim 4, wherein estimating the quantity/weight and/or type of the laundry in the treating chamber is carried out in function of one or more of: laundry moisture; temperature of a fluid circulating within the laundry drying machine; an electrical characteristic of a motor power supply; a signal indicative of an airflow circulating through the treating chamber; and a signal provided by a weight sensor.

6. The method according to claim 5, further comprising estimating a laundry treating program execution time (t.sub.pe) depending on the quantity/weight and/or type of the laundry in the treating chamber.

7. The method according to claim 6, further comprising updating the laundry treating program execution time (t.sub.pe) according to the comparison of the laundry moisture indicated by the signal (S.sub.m) and either the first threshold (THR.sub.1) or the second threshold (THR.sub.2).

8. The method according to claim 1, further comprising generating the signal (S.sub.m) indicative of the laundry moisture on the basis of one or more of: electrical impedance of the laundry; electrical current flowing through the laundry; and permittivity of the laundry.

9. The method according to claim 1, wherein the program main phase comprises one or more of: a laundry drying operation; operating a drying air heater to heat an airflow to be passed through the treating chamber; and supplying a treating substance to the laundry.

10. The method according to claim 9, wherein a portion of the program main phase overlaps the machine initialization phase.

11. The method according to claim 1, wherein carrying out only a portion of the selected laundry treating program comprises: performing one or more time-driven portions of the laundry treating program; and supplying a treating substance to the laundry.

12. The method according to claim 1, wherein the program final phase comprises a laundry cooling and/or tumbling operation.

13. The method according to claim 1, providing a notification of dried laundry and/or empty treating chamber and requesting introducing or removing laundry to/from the treating chamber.

14. The method according to claim 1, further comprising providing a notification of dried laundry and/or empty treating chamber to a remote device which communicates with the laundry drying machine through a wireless communication network.

15. A laundry drying machine comprising: a treating chamber adapted to contain laundry to be treated; and a control unit configured to: receive a signal (S.sub.m) indicative of laundry moisture from a moisture sensor; receive a user selection of a laundry treating program comprising a machine initialization phase for detecting physical parameters of the laundry and/or of the laundry drying machine, a program main phase for tumbling the laundry while a heater is ON, and a program final phase for tumbling the laundry while the heater is OFF; perform a machine initialization phase including comparing the laundry moisture indicated by the signal (S.sub.m) to a first threshold (THR.sub.1), which is stored in the control unit and is indicative of dried laundry or an empty treating chamber; and upon determining that the signal (S.sub.m) is equal to or less than the first threshold (THR.sub.1), maintaining the heater OFF while performing one or more of the following: skipping the program main phase by not performing the program main phase and by starting the program final phase, and stopping the laundry treating program by not performing the program main phase and not performing the program final phase.

16. The laundry drying machine according to claim 15, wherein the moisture sensor comprises a couple of electrodes arranged so as to be touched by laundry contained in the treating chamber during a laundry treating program and/or an arrangement forming a capacitor having the laundry as part of its dielectric.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows in a perspective view a laundry drying machine according to an embodiment of the present invention;

(2) FIGS. 2A and 2B show details of the laundry drying machine of FIG. 1, illustrating an exemplary arrangement of a plate of a condenser having the laundry mass to be dried as (part of) the condenser dielectric;

(3) FIG. 3 schematically shows a flow-chart illustrating an embodiment of the method for controlling a laundry drying machine according to the invention;

(4) FIG. 4 shows graphs A-C illustrating the intensity of the signal S.sub.m in three different conditions: empty treating chamber, dried laundry load and wet laundry item(s).

DETAILED DESCRIPTION OF EXEMPLARY AND NON-LIMITATIVE EMBODIMENTS OF THE PRESENT INVENTION

(5) With reference to the drawings, in FIG. 1 there is shown in a perspective view a laundry drying machine 100 according to an embodiment of the present invention, for example, although not limitatively, a laundry dryer, particularly a tumble dryer. It is pointed out that although here and in the following description reference is made to a laundry dryer, this is not to be construed as a limitation, because the present invention also covers and applies to combined laundry washers and dryers (i.e., laundry washing machines also having a laundry drying function).

(6) The laundry drying machine 100 comprises a cabinet 105, for example parallelepiped-shaped. The cabinet 105 accommodates therein a treating chamber 110 for the laundry mass to be dried. The treating chamber 110 is for example defined by the inner space of a rotatable drum which is adapted to contain the laundry mass to be dried (in a combined laundry washer and dryer appliance, the treating chamber comprises a washing basket or drum which is contained in a washing tub). The cabinet 105 also encloses the electrical, electronic, mechanical, aeraulic and hydraulic components necessary for the operation of the laundry drying machine 100.

(7) The laundry drying machine 100 comprises a control unit 117, schematically shown in FIG. 1, which is programmable to carry out a laundry treating program on laundry. The control unit 117 can comprise for example one or more microprocessors, electronic boards, etc.

(8) A front panel 115 of the cabinet 105 has a loading opening 120 providing an access to the rotatable drum 110 for loading/unloading the laundry mass to be dried. The loading opening 120 has a rim 125, preferably substantially annular, in which door hinges 130 as well as door locking means (not shown) are arranged for, respectively, hinging and locking a door 135. The door 135 is adapted for sealably closing the loading opening 120 during the laundry treating program.

(9) The front panel 115 also comprises a user interface 116. Preferably, the user interface is an input selector installed on the front panel 115. In another embodiment the user interface may be available in a remote device which communicates with the laundry drying machine through a wireless communication network. Such a remote device could be a smartphone, a tablet, a computer and the like.

(10) The laundry drying machine 100 comprises a drying air circulation system, for causing drying air to circulate through the drum 110 where the laundry to be dried is loaded. The drying air circulation system is not shown in the drawings, not being of relevance for the understanding of the present invention. Any known drying air circulation system can be adopted, for example an open-loop drying air circulation system (in which drying air is: taken in from the outside ambient, heated up, caused to flow through the drum 110 to extract moisture from the laundry to be dried, then possibly de-moisturized and cooled down and finally exhausted to the outside ambient) or a closed-loop drying air circulation system (in which the drying air is: heated up, caused to flow through the drum 110 to extract moisture from the laundry to be dried, de-moisturized and cooled down, and then again heated up and reintroduced in the drum). The drying air de-moisturizing and cooling system or moisture condensing system can comprise an air-air heat exchanger or a heat pump exploiting a suitable refrigerant fluid. The drying air heater can comprise a Joule-effect heater; in case of use of a heat pump, one of the heat exchangers of the heat pump (refrigerant evaporator) is used to cool down the moisture-laden drying air, while another heat exchanger (refrigerant condenser) of the heat pump can advantageously be exploited for heating the drying air.

(11) The drying air circulation system can for example be designed such that the drying air is introduced into the drum 110 at or proximate to the rear portion thereof (rear with respect to the machine front, corresponding to the front panel 115). After flowing through the drum 110 (and hitting the laundry mass contained therein), the drying air can leave the drum 110 passing through an opening 140 provided close to the rim 125 of the loading opening 120, on the inner side thereof (i.e., looking the machine frontally, behind the rim 125 of the loading opening 120).

(12) The laundry drying machine comprises a moisture sensor 200. In the embodiment shown in the figures the moisture sensor 200 comprises an arrangement forming a capacitor having said laundry as part of its dielectric. FIG. 2A is a view of the front panel 115 from behind, showing the inner side of the loading opening rim 125, facing towards the drum 110 (in FIG. 2A, the front panel 115 is shown dismounted from the rest of the cabinet 110). FIG. 2B is a partial cross-sectional view along lines IIB-IIB indicated in FIG. 2A. There is shown a conductive plate member, e.g. a metal plate 205 (being part of the moisture sensor for measuring the moisture of the laundry to be dried), that is mounted to the inner side of the cabinet front panel 115, in the shown example just below the rim 125 of the loading opening 120, so as to face the drum 110 and, in operation, being in front of the laundry mass to be dried that, while it tumbles inside the rotatable drum 110, falls by gravity to the bottom of the drum 110. Preferably, the conductive plate 205 is arranged so as to not be directly touched by the laundry, being to this purpose protected, covered by a dielectric cover 210, e.g. made of plastic.

(13) A more detailed description of this type of moisture sensor is explained in the application EP3162952A1 of the same Applicant to which the present description refers to.

(14) FIG. 3 schematically shows a flow-chart illustrating an embodiment of the method for controlling a laundry drying machine according to the invention.

(15) At step S1 a laundry treating program is set by a user, using the user interface 116 shown in FIG. 1, and the program is then started, for example by pressing/touching a button on an input selector installed on the front panel 115.

(16) After the program is started, a machine initialization phase takes place, wherein the control unit 117 receives a signal S.sub.m that will be used for the estimation of the quantity/weight of the laundry in the treating chamber 110. In this embodiment such signal S.sub.m is provided by the moisture sensor 200 (Step S2). Such signal S.sub.m is received for a predetermined amount of time t.sub.end1 from the start of the program, such amount being preferably set to 90 sec. Preferably, the machine initialization phase comprises a machine warm up phase, wherein the drying air heater and the drying air fan (not illustrated) are activated to make process drying air circulating through the treating chamber 110. The machine initialization phase may, however, be carried out without activating the drying air fan and the drying air heater or activating, i.e. turning on, the drying air fan only.

(17) Once the predetermined amount of time t.sub.end1 is over, in Step S3 the control unit 117 processes the signals S.sub.m received from the moisture sensor 200 and estimates the quantity/weight of the laundry in the treating chamber 110. Once the estimated quantity/weight of the laundry is available, the control unit 117 classifies laundry in one of a plurality of different categories or load classes. Preferably, the classification is obtained by comparing the estimated quantity/weight of the laundry with one or more predetermined values, stored in the control unit 117 and indicative of a predetermined laundry quantity/weight. Preferably there are three load classes: “small”, “medium” and “large”. For example, if the value of the estimated quantity/weight of the laundry is below a predetermined value W.sub.1, the load class “small” is assigned; if the value of the estimated quantity/weight of the laundry is above a predetermined value W.sub.2, the load class “large” is assigned; if the value of the estimated quantity/weight of the laundry is below W.sub.2 and above W.sub.1, the load class “medium” is assigned. The predetermined values (W.sub.1, W.sub.2) are experimentally calculated, preferably by comparing a known quantity/weight of the laundry with a plurality of estimations that the control unit 117 carries out when such known quantity/weight of the laundry is actually in the treating chamber 110. Values (W.sub.1, W.sub.2) are calculated such that the estimations carried out by the control unit 117 well approximate the real quantity/weight of laundry in the treating chamber 110, limiting as much as possible erroneous estimations. Each load class is associated with a laundry treating program execution time t.sub.pc, such time is then estimated by the control unit 117 once the laundry load contained in the treating chamber is classified in one of said load classes.

(18) During Step S4 the control unit 117 acquires the signal S.sub.m indicative of the moisture of the laundry in the treating chamber 110 from the moisture sensor 200 for a predetermined time interval t.sub.end2, which may be set from 10 to 15 minutes from the start of the program or from the end of Step S3.

(19) In Step S5 the control unit 117 determinates the relation between signal S.sub.m and a first threshold THR.sub.1 to assess whether the laundry contained in the treating chamber 110 is wet, or, instead, the laundry is dry or the treating chamber 110 is empty. In this embodiment, in Step S5, the control unit 117 counts how many times the moisture signal S.sub.m detected during time interval t.sub.end2 is above a first threshold THR.sub.1, which is stored in the control unit 117 and is indicative of dried laundry or empty threating chamber 110. The control unit then calculates a ratio between said count and the overall number of detection samples taken during time interval t.sub.end2. Then, said ratio is compared to a reference value which is determined experimentally. If the ratio is greater than the reference value then the moisture signal S.sub.m is determined to be above the threshold THR.sub.1, while if the ratio is equal or lower than the reference value, the moisture signal S.sub.m is determined to be equal or less than the threshold THR.sub.1.

(20) If the moisture signal S.sub.m is determined to be above the threshold THR.sub.1, the laundry is determined to be wet and the laundry treating program is continued (Step S6) according to the program selected by the user. If the moisture signal S.sub.m is determined to be equal or less than the first threshold THR.sub.1, the laundry is determined to be dried or the treating chamber 110 is determined to be empty and the process is continued to Step S7.

(21) At Step S6 starts the program main phase, which is the program portion wherein the most of the drying and/or conditioning treatments are carried out on laundry. In this phase the drying air heater and the drying air fan are kept working, or activated, and a flow of warm air circulates in the machine for drying the laundry in the treating chamber 110. The rotation of the treating chamber 110, in the form of a drum, causes agitation of the laundry items so that they are hit by the drying air flow and thereby dried.

(22) The program main phase may end when a predetermined level of laundry moisture, which depends from the selected laundry treating program or which is set by the user, is reached. The program main phase may further end when a predetermined duration time is elapsed. Such duration time being dependent from the laundry treating program or from the settings provided by the user.

(23) At the end of the program main phase, the program final phase starts, in such final phase the drying air heater is deactivated and the laundry is prepared for being removed from the laundry drying machine 100, preferably providing cool air and/or laundry tumbling. The laundry treating program is then ended at Step S10.

(24) At step S7, the signal S.sub.m, is then compared to a second threshold THR.sub.2 which is stored in the control unit 117 and is indicative of empty treating chamber 110. The laundry moisture indicated by the second threshold THR.sub.2 is smaller than the laundry moisture indicated by the first threshold THR.sub.1.

(25) If the signal S.sub.m is determined to be above the second threshold THR.sub.2 while being equal or smaller than the first threshold THR.sub.1, the laundry is determined to be dried and the Step S8 takes place. In Step S8 one or more of the following actions will be performed: carrying out only a portion of the selected laundry treating program; skipping the program main phase; starting the program final phase; stopping the laundry treating program; providing a notification of dried laundry and/or empty treating chamber 110.

(26) In this embodiment, in Step S8, the program main phase is skipped and the program final phase is started. During the program final phase the drying air heater is deactivated and the laundry is prepared for being removed from the laundry drying machine 100, preferably providing cool air and/or laundry tumbling. The program final phase may have a predetermined duration time. After Step S8 is completed, the laundry treating program is ended at Step S10.

(27) If in the Step S7 the signal S.sub.m is determined to be equal or less than the second threshold THR.sub.2, the treating chamber 110 is determined to be empty and Step S9 is carried out. In Step S9, the laundry treating program is stopped and/or a notification of empty treating chamber is provided to the user. Preferably, the notification comprises a request for the user to introduce laundry in the treating chamber 110. Further preferably, the notification is provided to a remote device which communicates with the laundry drying machine 100 through a wireless communication network.

(28) After the Step S9 is completed, the laundry treating program is ended at Step S10 and, a new laundry treating program may be started, in particular when the user has actually introduced laundry in the treating chamber 110 as prompted by the laundry drying machine 100.

(29) In Step S7 the determination of the relation between signal S.sub.m and the second threshold THR.sub.2 may be made in the same way described above with reference to the assessment of the relation between signal S.sub.m and the first threshold THR.sub.1.

(30) FIG. 4 shows graphs illustrating the intensity of the signal S.sub.m in three different conditions of the laundry treating chamber 110: graph (A) shows a signal S.sub.m provided when the treating chamber 110 is empty, graph (B) shows a signal S.sub.m provided when the treating chamber 110 contains a dried laundry load, while graph (C) shows a signal S.sub.m provided when the treating chamber 110 contains one or more wet items. As clearly visible in FIG. 4, the signal S.sub.m that is detected by the moisture sensor 200 and provided to the control unit 117, is not constant during the measuring time but it has a path fluctuating between lower and higher values. Therefore the control unit 117 has to carry out one of the methods described above, such as that disclosed at Steps S5, S7, in order to compare the signal S.sub.m with the thresholds THR.sub.1 and THR.sub.2.

(31) From the above description it is clear how the invention solves the previous mentioned aim and objects. The method for controlling a laundry drying machine according to the invention is able to detect a condition of empty treating chamber and/or a treating chamber containing a dried laundry load in an early stage of a laundry treating program. In this way it is possible executing specific actions aimed to reduce the laundry drying time and improve the machine performances, thereby avoiding unnecessary operations of the machine and undesired stresses or damages to laundry due to useless treatments.