Abstract:
Laundry treating appliances and methods of controlling the same to determine an end-of-cycle condition are disclosed. An example method of operating a laundry treating appliance having a treating chamber in which laundry is received for treatment, and a heated air system having a supply conduit coupled to the treating chamber and an exhaust conduit coupled to the treating chamber includes supplying heated air to the treating chamber via the supply conduit, exhausting air from the treating chamber via the exhaust conduit, repeatedly determining exhaust air temperatures of the air exhausted from the exhaust conduit, determining a windowed derivative of the exhaust air temperature values, determining a zero crossing of the windowed derivative, and initiating the termination of the supplying of heated air in response to the determination of the zero crossing.

Description:
FIELD OF THE DISCLOSURE 
     This disclosure relates generally to laundry treating appliances, and, more particularly, to laundry treating appliances and methods of controlling the same to determine an end-of-cycle condition. 
     BACKGROUND 
     Laundry treating appliances, such as a clothes washer, a clothes dryer, a combination washer-dryer, a refresher and a non-aqueous system, may have a configuration based on a rotating drum that defines a treating chamber in which laundry items are placed for treating according to a cycle of operation. A dispensing system may be provided for dispensing a treating chemistry as part of the cycle of operation. A controller may be operably connected with the dispensing system and may have various components of the laundry treating appliance to execute the cycle of operation. The cycle of operation may be selected manually by the user or automatically based on one or more conditions determined by the controller. 
     SUMMARY 
     A disclosed example method of operating a laundry treating appliance having a treating chamber in which laundry is received for treatment, and a heated air system having a supply conduit coupled to the treating chamber and an exhaust conduit coupled to the treating chamber includes supplying heated air to the treating chamber via the supply conduit, exhausting air from the treating chamber via the exhaust conduit, repeatedly determining exhaust air temperatures of the air exhausted from the exhaust conduit, determining a windowed derivative of the exhaust air temperature values, determining a zero crossing of the windowed derivative, and initiating the termination of the supplying of heated air in response to the determination of the zero crossing. 
     A disclosed example laundry treating appliance includes a treating chamber in which laundry is to be received for treatment, a heated air system having a supply conduit to supply heated air to the treating chamber, and an exhaust conduit to exhaust air from the treating chamber, a sensor to determine exhaust air temperatures of the air exhausted via the exhaust conduit, and a controller programmed to determine a windowed derivative of the exhaust air temperature values, determine a zero crossing of the windowed derivative, and initiate the termination of the supplying of heated air in response to the determination of the zero crossing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a graph depicting example exhaust air temperature profiles. 
         FIG. 2  is a schematic view of an example laundry treating appliance in the form of a clothes dryer. 
         FIG. 3  is a schematic view of an example manner of implementing the example controller of  FIG. 2 . 
         FIG. 4  is a flow chart illustrating an example method of determining an end of cycle condition. 
         FIG. 5  is a graph depicting example slope curves corresponding to the example exhaust temperature profiles of  FIG. 1 . 
         FIG. 6  is a graph depicting example slope derivative curves corresponding to the example slope curves of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     The state or point in a drying cycle when substantially all moisture has evaporated from the surface of the fabric in a laundry load, and the input heat energy primarily raises the temperature of the fabric, is known as critical moisture content state or point. As shown in  FIG. 1 , the slope of the temperature profile undergoes a significant increase past this critical moisture content point  100  compared to the preceding period when there is moisture present on the fabric surface. In  FIG. 1 , three temperature profiles  105 ,  110 ,  115  are shown corresponding to a 1 kilogram (kg) load, a 4 kg load and an 8 kg load, respectively. After determining the change in slope, remaining time needed for the drying process to finish can be determined using a load mass determined using load sensing or some other method. Also, after determining the critical moisture content state or point, the end of cycle behavior can be adjusted by, for example, lowering input power/usage of main actuators such as drum (speed), blower fan (speed), heater (temperature, duty cycle, electric power) to save energy and prevent overheating and/or over drying of the fabric. By more accurately determining the critical moisture content state or point, the examples disclosed herein may achieve greater energy savings, reduce the over drying of fabrics, provide better fabric care through cycle termination at a lower temperature, and/or can display a more accurate indication of the remaining cycle time. Because the examples disclosed herein can determine the critical moisture content state or point using only drum exhaust air temperature, the disclosed examples may be implemented without the complexity and cost of moisture sensing strips, inlet air temperature sensors, and/or humidity sensors. As used herein, “determining” means any manner, direct or indirect, by any actor, human or machine, by which a parameter or condition may be decided, which includes, without limitation sensing, calculating, estimating, experimenting, empirically, theoretically, mathematically, identifying, detecting, computing, measuring, reading an output of a sensor, and reading a sensor output from a memory. 
       FIG. 2  is a schematic view of an example laundry treating appliance  10  in the form of a clothes dryer  10 . The clothes dryer  10  described herein shares many features of a traditional automatic clothes dryer, which will not be described in detail except as necessary for a complete understanding of this disclosure. While examples are described in the context of a clothes dryer  10 , the examples disclosed herein may be used with any type of laundry treating appliance, non-limiting examples of which include a washing machine, a combination washing and drying machine, a non-aqueous system, and a refreshing/revitalizing machine. 
     As illustrated in  FIG. 2 , the clothes dryer  10  may include a cabinet  12  in which is provided a controller  14  that may receive input from a user through a user interface  16  for selecting a cycle of operation and controlling the operation of the clothes dryer  10  to implement the selected cycle of operation. As discussed in more detail below, the controller  14  may be programmed and/or configured to determine an end-of-cycle condition based on drum exhaust air temperatures, and to terminate and/or adjust drying based on the determined end-of-cycle condition. 
     The cabinet  12  may be defined by a front wall  18 , a rear wall  20 , and a pair of side walls  22  supporting a top wall  24 . A chassis may be provided with the walls being panels mounted to the chassis. A door  26  may be hingedly mounted to the front wall  18  and may be selectively movable between opened and closed positions to close an opening in the front wall  18 , which provides access to the interior of the cabinet  12 . 
     A rotatable drum  28  may be disposed within the interior of the cabinet  12  between opposing stationary front and rear bulkheads  30 ,  32 , which, along with the door  26 , collectively define a treating chamber  34  for treating laundry. As illustrated, and as is the case with most clothes dryers, the treating chamber  34  is not fluidly coupled to a drain. Thus, any liquid introduced into the treating chamber  34  may not be removed merely by draining. 
     Non-limiting examples of laundry that may be treated according to a cycle of operation include, a hat, a scarf, a glove, a sweater, a blouse, a shirt, a pair of shorts, a dress, a sock, a pair of pants, a shoe, an undergarment, and a jacket. Furthermore, textile fabrics in other products, such as draperies, sheets, towels, pillows, and stuffed fabric articles (e.g., toys), may be treated in the clothes dryer  10 . 
     The drum  28  may include at least one lifter  29 . In most dryers, there may be multiple lifters. The lifters may be located along an inner surface of the drum  28  defining an interior circumference of the drum  28 . The lifters may facilitate movement of the laundry  36  within the drum  28  as the drum  28  rotates. 
     The drum  28  may be operably coupled with a motor  54  to selectively rotate the drum  28  during a cycle of operation. The coupling of the motor  54  to the drum  28  may be direct or indirect. As illustrated, an indirect coupling may include a belt  56  coupling an output shaft of the motor  54  to a wheel/pulley on the drum  28 . A direct coupling may include the output shaft of the motor  54  coupled to a hub of the drum  28 . 
     An air system may be provided to the clothes dryer  10 . The air system supplies air to the treating chamber  34  and exhausts air from the treating chamber  34 . The supplied air may be heated or not. The air system may have an air supply portion that may form, in part, a supply conduit  38 , which has one end open to ambient air via a rear vent  37  and another end fluidly coupled to an inlet grill  40 , which may be in fluid communication with the treating chamber  34 . A heating element  42  may lie within the supply conduit  38  and may be operably coupled to and controlled by the controller  14 . If the heating element  42  is turned on, the supplied air will be heated prior to entering the drum  28 . 
     The air system may further include an air exhaust portion that may be formed in part by an exhaust conduit  44 . A lint trap  45  may be provided as the inlet from the treating chamber  34  to the exhaust conduit  44 . A blower  46  may be fluidly coupled to the exhaust conduit  44 . The blower  46  may be operably coupled to and controlled by the controller  14 . Operation of the blower  46  draws air into the treating chamber  34  as well as exhausts air from the treating chamber  34  through the exhaust conduit  44 . The exhaust conduit  44  may be fluidly coupled with a household exhaust duct (not shown) for exhausting the air from the treating chamber  34  to the outside of the clothes dryer  10 . 
     The air system may further include various sensors and other components, such as a thermistor  47  and a thermostat  48 , which may be coupled to the supply conduit  38  in which the heating element  42  may be positioned. The thermistor  47  and the thermostat  48  may be operably coupled to each other. Alternatively, the thermistor  47  may be coupled to the supply conduit  38  at or near to the inlet grill  40 . Regardless of its location, the thermistor  47  may be used to aid in determining an inlet temperature. A thermistor  51  and a thermal fuse  49  may be coupled to the exhaust conduit  44 . The thermistor  51  may be used to determine an outlet or exhaust air temperature. 
     A moisture sensor  50  may be positioned in the interior of the treating chamber  34  to monitor the amount of moisture of the laundry in the treating chamber  34 . One example of a moisture sensor  50  is a conductivity strip. The moisture sensor  50  may be operably coupled to the controller  14  such that the controller  14  receives output from the moisture sensor  50 . The moisture sensor  50  may be mounted at any location in the interior of the dispensing dryer  10  such that the moisture sensor  50  may be able to accurately sense the moisture content of the laundry. For example, the moisture sensor  50  may be coupled to one of the bulkheads  30 ,  32  of the drying chamber  34  by any suitable means. 
     A dispensing system  57  may be provided to the clothes dryer  10  to dispense one or more treating chemistries to the treating chamber  34  according to a cycle of operation. As illustrated, the dispensing system  57  may be located in the interior of the cabinet  12  although other locations are also possible. The dispensing system  57  may be fluidly coupled to a water supply  68 . The dispensing system  57  may be further coupled to the treating chamber  34  through one or more nozzles  69 . As illustrated, nozzles  69  are provided to the front and rear of the treating chamber  34  to provide the treating chemistry or liquid to the interior of the treating chamber  34 , although other configurations are also possible. The number, type and placement of the nozzles  69  are not germane to this disclosure. 
     As illustrated, the dispensing system  57  may include a reservoir  60 , which may be a cartridge, for a treating chemistry that is releasably coupled to the dispensing system  57 , which dispenses the treating chemistry from the reservoir  60  to the treating chamber  34 . The reservoir  60  may include one or more cartridges configured to store one or more treating chemistries in the interior of cartridges. A suitable cartridge system may be found in U.S. Pub. No. 2010/0000022 to Hendrickson et al., filed Jul. 1, 2008, entitled “Household Cleaning Appliance with a Dispensing System Operable Between a Single Use Dispensing System and a Bulk Dispensing System,” which is herein incorporated by reference in its entirety. 
     A mixing chamber  62  may be provided to couple the reservoir  60  to the treating chamber  34  through a supply conduit  63 . Pumps such as a metering pump  64  and delivery pump  66  may be provided to the dispensing system  57  to selectively supply a treating chemistry and/or liquid to the treating chamber  34  according to a cycle of operation. The water supply  68  may be fluidly coupled to the mixing chamber  62  to provide water from the water source to the mixing chamber  62 . The water supply  68  may include an inlet valve  70  and a water supply conduit  72 . It is noted that, instead of water, a different treating chemistry may be provided from the exterior of the clothes dryer  10  to the mixing chamber  62 . 
     The treating chemistry may be any type of aid for treating laundry, non-limiting examples of which include, but are not limited to, water, fabric softeners, sanitizing agents, de-wrinkling or anti-wrinkling agents, and chemicals for imparting desired properties to the laundry, including stain resistance, fragrance (e.g., perfumes), insect repellency, and UV protection. 
     The dryer  10  may also be provided with a steam generating system  80  that may be separate from the dispensing system  57  or integrated with portions of the dispensing system  57  for dispensing steam and/or liquid to the treating chamber  34  according to a cycle of operation. The steam generating system  80  may include a steam generator  82  fluidly coupled with the water supply  68  through a steam inlet conduit  84 . A fluid control valve  85  may be used to control the flow of water from the water supply conduit  72  between the steam generating system  80  and the dispensing system  57 . The steam generator  82  may further be fluidly coupled with the one or more supply conduits  63  through a steam supply conduit  86  to deliver steam to the treating chamber  34  through the nozzles  69 . Alternatively, the steam generator  82  may be coupled with the treating chamber  34  through one or more conduits and nozzles independently of the dispensing system  57 . 
     The steam generator  82  may be any type of device that converts the supplied liquid to steam. For example, the steam generator  82  may be a tank-type steam generator that stores a volume of liquid and heats the volume of liquid to convert the liquid to steam. Alternatively, the steam generator  82  may be an in-line steam generator that converts the liquid to steam as the liquid flows through the steam generator  82 . 
     It will be understood that the details of the dispensing system  57  and steam generating system  80  are not germane to this disclosure and that any suitable dispensing system and/or steam generating system may be used with the dryer  10 . It is also within the scope of this disclosure for the dryer  10  to not include a dispensing system or a steam generating system. 
       FIG. 3  is a schematic view of an example manner of implementing the example controller  14  of  FIG. 2 . As shown in  FIG. 3 , the controller  14  is coupled to various components of the dryer  10 . The controller  14  may be communicably coupled to components of the clothes dryer  10  such as the heating element  42 , the blower  46 , the thermistor  47 , the thermostat  48 , the thermal fuse  49 , the thermistor  51 , the moisture sensor  50 , the motor  54 , the inlet valve  70 , the pumps  64 ,  66 , the steam generator  82  and the fluid control valve  85  to either control these components and/or receive their input for use in controlling the components. The controller  14  is also operably coupled to the user interface  16  to receive input from the user through the user interface  16  for the implementation of the drying cycle and provide the user with information regarding the drying cycle. An example method that may be carried out by the controller  14  to determine an end-of-cycle condition, and to terminate and/or adjust a drying processed based on the end-of-cycle condition is described below in connection with  FIG. 4 . 
     The user interface  16  may be provided having operational controls such as dials, lights, knobs, levers, buttons, switches, and displays enabling the user to input commands to a controller  14  and receive information about a treatment cycle from components in the clothes dryer  10  or via input by the user through the user interface  16 . The user may enter many different types of information, including, without limitation, cycle selection and cycle parameters, such as cycle options. Any suitable cycle may be used. Non-limiting examples include, Casual, Delicate, Super Delicate, Heavy Duty, Normal Dry, Damp Dry, Sanitize, Quick Dry, Timed Dry, and Jeans. 
     The controller  14  may implement a treatment cycle selected by the user according to any options selected by the user and provide related information to the user. The controller  14  may also comprise a central processing unit (CPU)  74  and an associated memory  76  where various treatment cycles and associated data, such as look-up tables, may be stored. One or more software applications, such as an arrangement of executable machine-readable commands/instructions may be stored in the memory and executed by the CPU  74  to implement, perform and/or otherwise carry-out the one or more treatment cycles. Example machine-readable instructions that may be executed by the CPU  74  to determine an end-of-cycle condition, and to terminate and/or adjust a drying process based on the end-of-cycle condition are discussed below in connection with  FIG. 4 . 
     In general, the controller  14  will effect a cycle of operation to effect a treating of the laundry in the treating chamber  34 , which may or may not include drying. The controller  14  may actuate the blower  46  to draw an inlet air flow  58  into the supply conduit  38  through the rear vent  37  when air flow is needed for a selected treating cycle. The controller  14  may activate the heating element  42  to heat the inlet air flow  58  as it passes over the heating element  42 , with the heated air  59  being supplied to the treating chamber  34 . The heated air  59  may be in contact with a laundry load  36  as it passes through the treating chamber  34  on its way to the exhaust conduit  44  to effect a moisture removal of the laundry. The heated air  59  may exit the treating chamber  34 , and flow through the blower  46  and the exhaust conduit  44  to the outside of the clothes dryer  10 . The controller  14  continues the cycle of operation until completed. If the cycle of operation includes drying, the controller  14  determines when the laundry is dry.  FIGS. 4-6  illustrate an example method of determining when laundry is dry. 
     During a cycle of operation, one or more treating chemistries may be provided to the treating chamber  34  by the dispensing system  57  as actuated by the controller  14 . To dispense the treating chemistry, the metering pump  64  is actuated by the controller  14  to pump a predetermined quantity of the treating chemistry stored in the cartridge  60  to the mixing chamber  62 , which may be provided as a single charge, multiple charges, or at a predetermined rate, for example. The treating chemistry may be in the form of a gas, liquid, solid, gel or any combination thereof, and may have any chemical composition enabling refreshment, disinfection, whitening, brightening, increased softness, reduced odor, reduced wrinkling, stain repellency or any other desired treatment of the laundry. The treating chemistry may be composed of a single chemical, a mixture of chemicals, or a solution of a solvent, such as water, and one or more chemicals. 
       FIG. 4  is a flow chart of an example method to determine an end-of-cycle condition and terminate and/or adjust drying of laundry based on the determined end-of-cycle condition. A processor, a controller and/or any other suitable processing device such as the example CPU  74  may be used, configured and/or programmed to execute and/or carry out the example method of  FIG. 4 . For example, the example method of  FIG. 4  may be embodied in program code and/or machine-readable instructions stored on a tangible computer-readable medium such as the memory  76 . Many other methods of implementing the example method of  FIG. 4  may be employed. For example, the order of execution may be changed, and/or one or more of the blocks and/or interactions described may be changed, eliminated, sub-divided, or combined. Additionally, any or all of the example method of  FIG. 4  may be carried out sequentially and/or carried out in parallel by, for example, separate processing threads, processors, devices, discrete logic, circuits, etc. 
     As used herein, the term “tangible computer-readable medium” is expressly defined to include any type of computer-readable medium and to expressly exclude propagating signals. As used herein, the term “non-transitory computer-readable medium” is expressly defined to include any type of computer-readable medium and to exclude propagating signals. Example tangible and/or non-transitory computer-readable medium include a volatile and/or non-volatile memory, a volatile and/or non-volatile memory device, a flash memory, a read-only memory (ROM), a random-access memory (RAM), a programmable ROM (PROM), an electronically-programmable ROM (EPROM), and/or an electronically-erasable PROM (EEPROM). 
     The method of  FIG. 4  starts with the controller  14  waiting a pre-determined amount of time t start  to allow the clothes dryer  10  to reach an initial equilibrium (block  405 ). The controller  14  determines at time t start  a reference temperature T o  such as an ambient temperature (block  410 ), and begins periodically determining (e.g., measuring) exhaust air temperatures using, for example, the example thermistor  51  (block  415 ). Example exhaust air temperatures  105 ,  110  and  115  are shown in  FIG. 1  for 1 kg, 4 kg and 8 kg laundry masses, respectively. 
     The controller  14  determines (e.g., computes) a slope of the exhaust air temperatures by computing a difference between a current exhaust air temperature T e  and the reference temperature T o , and computing a product of the difference and an inverse of the time t at which the exhaust air temperature T e  was determined (block  420 ). The slope of the exhaust air temperatures can be expressed mathematically as 
                     s   ⁡     (   t   )       =           T   e     -     T   o       t     .             EQN   ⁢           ⁢     (   1   )                 
Because the slope expressed in EQN (1) is computed with reference to the reference temperature T o  determined at t start  and with a denominator of t, the slope of EQN (1) does not represent a conventional piecewise derivative of the exhaust air temperatures. Example slopes  505 ,  510  and  515  corresponding to the example exhaust air temperature profiles  105 ,  110  and  115  of  FIG. 1  are shown in  FIG. 5 . As shown in  FIG. 5 , the slopes  505 ,  510  and  515  have a local minima corresponding to the critical moisture content points  100  of  FIG. 1 . In some examples, a slope value is determined as each exhaust air temperature is determined.
 
     Returning to  FIG. 4 , to determine (e.g., identifies) the local minima of the slope, the example controller  14  determines (e.g., computes) a derivative of the slope values. A zero-crossing of the slope derivative corresponds to a local minima of the slope. Because the exhaust air temperatures are typically noisy, the slope values will be noisy. To substantially mitigate false determination of a zero-crossing, the derivative of the slope is determined using slope values spaced apart by a window t w . Accordingly, the controller  14  waits until enough initial slope values have been determined before beginning to determine derivatives of the slope (block  425 ). 
     Once enough slope values have been determined, the controller  14  begins determining slope derivative values (block  430 ). In some examples, a new slope derivative value is determined as each slope value is determined. The controller  14  determines (e.g., computes) a slope derivative value by computing a difference between two slope values that are spaced apart by the window t w , which is selected to reduce the occurrence of false zero-crossings, and computing a product of the difference and the inverse of the window t w . The slope derivative can be expressed mathematically as 
     
       
         
           
             
               
                 
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                   EQN 
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     An example value of the window t w  is 250 seconds. Because the example derivative of EQN (2) uses slope values spaced apart by the window t w , the derivative of EQN (2) is referred to herein as a “windowed derivative.” In contrast, a conventional derivative is mathematically expressed as 
                         s   ′     ⁡     (   t   )       =         s   ⁡     (   t   )       -     s   ⁡     (     t   -     Δ   ⁢           ⁢   t       )           Δ   ⁢           ⁢   t         ,           EQN   ⁢           ⁢     (   3   )                 
where Δt is a small value that is substantially smaller than the window t w . The use of a conventional derivative would lead to infrequent false zero-crossing determinations. Example slope derivatives  605 ,  610  and  615  corresponding to the example slopes  505 ,  510  and  515  of  FIG. 5  are shown in  FIG. 6 . As shown in  FIG. 6 , the slope derivatives  606 ,  610  and  615  have a zero-crossing corresponding to the critical moisture content points  100  of  FIG. 1 .
 
     Returning to  FIG. 4 , when the slope derivative of EQN (2) is substantially equal to zero (block  435 ), the controller  14  determines (e.g., estimates) the mass of the laundry in the laundry drying appliance  14  using, for example, a weight and/or volume sensor (block  440 ). Based on the determined load mass, the controller  14  determines an additional amount of time and/or parameters to complete the current drying cycle (block  445 ). For example, a large load (e.g., approximately 8 kg) will be dried for an additional 10 minutes, while a small load (e.g., approximately 1 kg) will be dried for an additional 3 minutes. The controller  14  completes the drying cycle based on the determined time and/or parameters (block  450 ), and control exits from the example method of  FIG. 4 . 
     Returning to block  435 , if the derivative slope is not substantially equal to zero (block  435 ), control returns to block  415  to determine another outlet air temperature. 
     Returning to block  425 , if not enough slope values have been determined to enable the determination of derivative slope values (block  425 ), control returns to block  415  to determine another air temperature and determine another slope value. 
     To the extent not already described, the different features and structures of the various embodiments may be used in combination with each other as desired. That one feature may not be illustrated in all of the embodiments is not meant to be construed that it cannot be, but is done for brevity of description. Thus, the various features of the different embodiments may be mixed and matched as desired to form new embodiments, whether or not the new embodiments are expressly described. 
     Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the claims of this patent.