Patent Publication Number: US-9890489-B2

Title: Laundry treating appliance and method using inertia detection to control liquid extraction

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 13/469,116, filed May 11, 2012, now U.S. Pat. No. 9,091,011, issued Jul. 28, 2015, which claims the benefit of U.S. Provisional Patent Application No. 61/577,838, filed Dec. 20, 2011, both of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Laundry treating appliances, such as a washing machine, may include a drum defining a treating chamber for receiving and treating a laundry load according to a cycle of operation. The cycle of operation may include a phase during which liquid may be removed from the laundry load, such as an extraction phase during which a drum holding the laundry load rotates at speeds high enough to impart a sufficient centrifugal force on the laundry load to remove the liquid. Typically, the extraction phase comprises one or more speed ramps, where the speed is accelerated, and a speed plateau, which is a constant speed phase. Most acceleration phases comprise multiple repeats of a ramp followed by a speed plateau, which increase the speed of the drum up to a final speed plateau, which represents the highest rotational speed. 
     During the extraction phase, the laundry load may be satellized by centrifugal force to rotate with the drum. Extraction in this manner results in a decrease in the mass of the load as liquid is extracted during the final extraction plateau. The rate of decrease in the mass of the load slows over time as there is the amount of extractable liquid is reduced. Extraction cycles currently utilize time to determine when to terminate the final extraction plateau. On loads that are extracted quickly, remaining time, along with energy and cost, may be expended at this plateau with little or no return. For highly absorbent loads that release liquid slowly, insufficient time may be allotted, and the residual moisture content (RMC) of the load may not be as low as it should be. 
     SUMMARY OF THE INVENTION 
     According to one embodiment, a laundry treating appliance for treating a laundry load according to at least one cycle of operation, comprising: a rotatable drum at least partially defining a treating chamber for receiving the laundry load, a motor rotatably driving the drum in response to a speed control signal; and a controller operably coupled to the motor and programmed to provide a speed control signal to the motor to rotate the drum at a speed plateau at a rotational speed of the drum greater than a satellizing speed to effect an extracting of liquid from the laundry load, monitoring an inertia of the laundry load during the speed plateau, determining a decay rate from the monitored inertia, and terminating the speed plateau upon the decay rate satisfying a reference value. 
     In another embodiment, a method of operating a laundry treating appliance having a rotatable drum at least partially defining a treating chamber for receiving a laundry load for treatment according to at least one cycle of operation, and a motor rotating the rotatable drum, the method comprising: extracting liquid from the laundry load by applying a constant speed control signal to the motor to rotate the drum at a maximum speed plateau for a given cycle of operation, repeatedly determining the inertia of the laundry load during the maximum speed plateau by oscillating the rotational speed of the drum about the maximum speed plateau and determining the inertia from the oscillations, determining a change in the inertia from the repeated determinations of inertia, and terminating the extracting of liquid upon the change in inertia satisfying a reference value. 
     In yet another embodiment, a laundry treating appliance for treating a laundry load according to at least one cycle of operation, comprising: a rotatable drum at least partially defining a treating chamber for receiving the laundry load, a motor rotatably driving the drum in response to a speed control signal, and a controller operably coupled to the motor and providing a speed control signal to the motor to rotate the drum at a maximum speed plateau to effect an extracting of liquid from the laundry load, repeatedly determining the inertia of the laundry load during the maximum speed plateau by oscillating the rotational speed of the drum about the maximum speed plateau and determining the inertia from the oscillations, determining a change in the inertia from the repeated determinations of inertia, and terminating the maximum speed plateau upon the change in inertia satisfying a reference value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic, cross-sectional view of a laundry treating appliance in the form of a horizontal axis washing machine according to one embodiment of the invention. 
         FIG. 2  is a schematic view of a controller of the laundry treating appliance of  FIG. 1 . 
         FIG. 3  is a graphical representation of a sinusoidal torque profile superimposed on the plateau portion of the profile of the drum during a constant speed phase, with the sinusoidal profile to repeatedly determine the inertia of the laundry load during the constant speed phase in the laundry treating appliance of  FIG. 1 . 
     
    
    
     DESCRIPTION OF AN EMBODIMENT OF THE INVENTION 
       FIG. 1  is a schematic, cross-sectional view of a laundry treating appliance in the form of a horizontal axis washing machine  10  according to one embodiment of the invention. While the laundry treating appliance is illustrated as a horizontal axis washing machine  10 , the laundry treating appliance according to the invention may be any machine that treats articles such as clothing or fabrics. Non-limiting examples of the laundry treating appliance may include a front loading/horizontal axis washing machine; a top loading/vertical axis washing machine; a combination washing machine and dryer; an automatic dryer; a tumbling or stationary refreshing/revitalizing machine; an extractor; a non-aqueous washing apparatus; and a revitalizing machine. The washing machine  10  described herein shares many features of a traditional automatic washing machine, which will not be described in detail except as necessary for a complete understanding of the invention. 
     Washing machines are typically categorized as either a vertical axis washing machine or a horizontal axis washing machine. As used herein, the “vertical axis” washing machine refers to a washing machine having a rotatable drum, perforate or imperforate, that holds fabric items and a clothes mover, such as an agitator, impeller, nutator, and the like within the drum. The clothes mover moves within the drum to impart mechanical energy directly to the clothes or indirectly through liquid in the drum. The liquid may include one of wash liquid and rinse liquid. The wash liquid may have at least one of water and a wash aid. Similarly, the rinse liquid may have at least one of water and a rinse aid. The clothes mover may typically be moved in a reciprocating rotational movement. In some vertical axis washing machines, the drum rotates about a vertical axis generally perpendicular to a surface that supports the washing machine. However, the rotational axis need not be vertical. The drum may rotate about an axis inclined relative to the vertical axis. As used herein, the “horizontal axis” washing machine refers to a washing machine having a rotatable drum, perforated or imperforated, that holds fabric items and washes the fabric items by rubbing against one another as the drum rotates. In some horizontal axis washing machines, the drum rotates about a horizontal axis generally parallel to a surface that supports the washing machine. However, the rotational axis need not be horizontal. The drum may rotate about an axis inclined relative to the horizontal axis. In horizontal axis washing machines, the clothes are lifted by the rotating drum and then fall in response to gravity to form a tumbling action. Mechanical energy is imparted to the clothes by the tumbling action formed by the repeated lifting and dropping of the clothes. Vertical axis and horizontal axis machines are best differentiated by the manner in which they impart mechanical energy to the fabric items. The illustrated exemplary washing machine of  FIG. 1  is a horizontal axis washing machine. 
     The washing machine  10  may include a cabinet  12 , which may be a frame to which decorative panels are mounted. A controller  14  may be provided on the cabinet  12  and controls the operation of the washing machine  10  to implement a cycle of operation. A user interface  16  may be included with the controller  14  to provide communication between the user and the controller  14 . The user interface  16  may include one or more knobs, switches, displays, and the like for communicating with the user, such as to receive input and provide output. 
     A rotatable drum  18  may be disposed within the interior of the cabinet  12  and defines a treating chamber  20  for treating laundry. The rotatable drum  18  may be mounted within an imperforate tub  22 , which is suspended within the cabinet  12  by a resilient suspension system  24 . The drum  18  may include a plurality of perforations  26 , such that liquid may flow between the tub  22  and the drum  18  through the perforations  26 . The drum  18  may further include a plurality of lifters  28  disposed on an inner surface of the drum  18  to lift a laundry load (not shown here) received in the laundry treating chamber  20  while the drum  18  rotates. 
     While the illustrated washing machine  10  includes both the tub  22  and the drum  18 , with the drum  18  defining the laundry treating chamber  20 , it is within the scope of the invention for either the drum  18  or tub  22  to define the treating chamber  20  as well as the washing machine  10  including only one receptacle, with the one receptacle defining the laundry treating chamber for receiving a laundry load to be treated. 
     A motor  30  is provided to rotate the drum  18 . The motor  30  includes a stator  32  and a rotor  34 , which are mounted to a drive shaft  36  extending from the drum  18  for selective rotation of the treating chamber  20  during a cycle of operation. It is also within the scope of the invention for the motor  30  to be coupled with the drive shaft  36  through a drive belt and/or a gearbox for selective rotation of the treating chamber  20 . 
     The motor  30  may be any suitable type of motor for rotating the drum  18 . In one example, the motor  30  may be a brushless permanent magnet (BPM) motor having a stator  32  and a rotor  34 . Other motors, such as an induction motor or a permanent split capacitor (PSC) motor, may also be used. The motor  30  may rotate the drum  18  at various speeds in either rotational direction. 
     The washing machine  10  may also include at least one balance ring  38  containing a balancing material moveable within the balance ring  38  to counterbalance an imbalance that may be caused by laundry in the treating chamber  20  during rotation of the drum  18 . The balancing material may be in the form of metal balls, fluid or a combination thereof. The balance ring  38  may extend circumferentially around a periphery of the drum  18  and may be located at any desired location along an axis of rotation of the drum  18 . When multiple balance rings  38  are present, they may be equally spaced along the axis of rotation of the drum  18 . 
     The washing machine  10  of  FIG. 1  may further include a liquid supply and recirculation system. Liquid, such as water, may be supplied to the washing machine  10  from a water supply  42 , such as a household water supply. A supply conduit  44  may fluidly couple the water supply  42  to the tub  22  and a treatment dispenser  46 . The supply conduit  44  may be provided with an inlet valve  48  for controlling the flow of liquid from the water supply  42  through the supply conduit  44  to either the tub  22  or the treatment dispenser  46 . The dispenser  46  may be a single-use dispenser, that stores and dispenses a single dose of treating chemistry and must be refilled for each cycle of operation, or a multiple-use dispenser, also referred to as a bulk dispenser, that stores and dispenses multiple doses of treating chemistry over multiple executions of one or more cycles of operation. 
     A liquid conduit  50  may fluidly couple the treatment dispenser  46  with the tub  22 . The liquid conduit  50  may couple with the tub  22  at any suitable location on the tub  22  and is shown as being coupled to a front wall of the tub  22  in  FIG. 1  for exemplary purposes. The liquid that flows from the treatment dispenser  46  through the liquid conduit  50  to the tub  22  typically enters a space between the tub  22  and the drum  18  and may flow by gravity to a sump  52  formed in part by a lower portion of the tub  22 . The sump  52  may also be formed by a sump conduit  54  that may fluidly couple the lower portion of the tub  22  to a pump  56 . The pump  56  may direct fluid to a drain conduit  58 , which may drain the liquid from the washing machine  10 , or to a recirculation conduit  60 , which may terminate at a recirculation inlet  62 . The recirculation inlet  62  may direct the liquid from the recirculation conduit  60  into the drum  18 . The recirculation inlet  62  may introduce the liquid into the drum  18  in any suitable manner, such as by spraying, dripping, or providing a steady flow of the liquid. 
     The liquid supply and recirculation system may further include one or more devices for heating the liquid such as a steam generator  65  and/or a sump heater  63 . The steam generator  65  may be provided to supply steam to the treating chamber  20 , either directly into the drum  18  or indirectly through the tub  22  as illustrated. The inlet valve  48  may also be used to control the supply of water to the steam generator  65 . The steam generator  65  is illustrated as a flow-through steam generator, but may be other types, including a tank type steam generator. Alternatively, the heating element, in the form of the sump heater  63 , may be used to heat laundry (not shown), air, the rotatable drum  18 , or liquid in the tub  22  to generate steam, in place of or in addition to the steam generator  65 . The steam generator  65  may be used to heat to the laundry as part of a cycle of operation, much in the same manner as heating element  63 , as well as to introduce steam to treat the laundry. 
     Additionally, the liquid supply and recirculation system may differ from the configuration shown in  FIG. 1 , such as by inclusion of other valves, conduits, wash aid dispensers, heaters, sensors, to control the flow of treating liquid through the washing machine  10  and for the introduction of more than one type of detergent/wash aid. Further, the liquid supply and recirculation system need not include the recirculation portion of the system or may include other types of recirculation systems. 
     The controller  14  may be provided in the cabinet  12  and communicably couple one or more components to receive an output signal from components and control the operation of the washing machine  10  to implement one or more cycles of operation, which is further described in detail with reference to  FIG. 2 . The controller  14  may be provided with a memory  64  and a central processing unit (CPU)  66 . The memory  64  may be used for storing the control software in the form of executable instructions that is executed by the CPU  66  in completing one or more cycles of operation using the washing machine  10  and any additional software. Additional software may be executed in conjunction with control software in completing a cycle of operation by the washing machine  10 . For example, additional software may determine at least one of the torque, inertia, and acceleration of drum  18  with laundry within the treating chamber  20 , based on the input from other components and sensors  68 ,  70  during a cycle of operation. The particular program is not germane to the invention. 
     The memory  64  may also be used to store information, such as a database or look-up table, or to store data received from one or more components of the washing machine  10  that may be communicably coupled with the controller  14  as needed to execute the cycle of operation. 
     The controller  14  may be operably coupled with one or more components of the washing machine  10  for communicating with and controlling the operation of the component to complete a cycle of operation. For example, the controller  14  may be coupled with the user interface  16  for receiving user selected inputs and communicating information with the user. The user interface  16  may be provided that has operational controls such as dials, lights, knobs, levers, buttons, switches, sound device, and displays enabling the user to input commands to a controller  14  and receive information about a specific cleaning cycle from sensors (not shown) in the washing machine  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, Heavy Duty, Normal, Delicates, Rinse and Spin, Sanitize, and Bio-Film Clean Out. 
     The controller  14  may further be operably coupled to the motor  30  to provide a motor control signal to rotate the drum  18  according to a speed profile for the at least one cycle of operation, for controlling at least one of the direction, rotational speed, acceleration, deceleration, torque and power consumption of the motor  30 . 
     The controller  14  may be operably coupled to the treatment dispenser  46  for dispensing a treating chemistry during a cycle of operation. The controller  14  may be coupled to the steam generator  65  and the sump heater  63  to heat the liquid as required by the controller  14 . The controller  14  may also be coupled to the pump  56  and inlet valve  48  for controlling the flow of liquid during a cycle of operation. 
     The controller  14  may also receive input from one or more sensors  70 , which are known in the art. Non-limiting examples of sensors that may be communicably coupled with the controller  14  include: a treating chamber temperature sensor, a moisture sensor, a weight sensor, a drum position sensor, a motor speed sensor, a motor torque sensor  68  or the like. 
     The motor torque sensor  68  may include a motor controller or similar data output on the motor  30  that provides data communication with the motor  30  and outputs motor characteristic information such as oscillations, generally in the form of an analog or digital signal, to the controller  14  that is indicative of the applied torque. The controller  14  may use the motor characteristic information to determine the torque applied by the motor  30  using a computer program that may be stored in the controller memory  64 . Specifically, the motor torque sensor  68  may be any suitable sensor, such as a voltage or current sensor, for outputting a current or voltage signal indicative of the current or voltage supplied to the motor  30  to determine the torque applied by the motor  30 . Additionally, the motor torque sensor  68  may be a physical sensor or may be integrated with the motor  30  and combined with the capability of the controller  14 , may function as a sensor. For example, motor characteristics, such as speed, current, voltage, direction, torque etc., may be processed such that the data provides information in the same manner as a separate physical sensor. In contemporary motors, the motors  30  often have their own controller that outputs data for such information. 
     When the drum  18  with the laundry load rotates during an extraction phase, the distributed mass of the laundry load about the interior of the drum is a part of the inertia of the rotating system of the drum and laundry load, along with other rotating components of the appliance. The inertia of the rotating components of the appliance without the laundry is generally known and can be easily tested for. Thus, the inertia of the laundry load can be determined by determining the total inertia of the combined load inertia the appliance inertia, and then subtracting the known appliance inertia. In many cases, as the total inertia is proportional to the load inertia, it is not necessary to distinguish between the appliance inertia and the load inertia. 
     The total inertia can be determined from the torque necessary to rotate the drum. Generally the motor torque for rotating the drum  18  with the laundry load may be represented in the following way:
 
τ= J*{dot over (ω)}+B*ω+C   (1)
 
where, τ=torque, J=inertia, {dot over (ω)}=acceleration, ω=rotational speed, B=viscous damping coefficient, and C=coulomb friction.
 
     Historically, to determine the inertia, it was necessary to have a plateau followed by a ramp. During the plateau, the rotational speed may be maintained to be constant, and the resulting acceleration ({dot over (ω)}) may be zero. Then, from equation (1), the torque may be expressed only in terms of B*ω in the following way:
 
τ= B*ω+C   (2)
 
     C may be taken as zero since the Coulomb friction is typically very small compared to the remaining variables. Rearranging the variables, we have:
 
τ/ω= B.  
 
τ and ω are variables that may be readily determined from torque sensors and velocity sensors. The B is easily calculated during a plateau.
 
     Once B was known, it was possible to determine the inertia by accelerating the drum along a ramp. During such an acceleration, the inertia was the only unknown and could be solved for. The acceleration was normally defined by the ramp or sensed. For example, most ramps are accomplished by providing an acceleration rate to the motor. This acceleration rate can be used for the acceleration in the equation. 
     One shortcoming of this approach is that B tends to be a function of speed and may increase as speed increases. The B calculated on the plateau was not the same value of B where the inertia was calculated. This error was generally minimal compared to the magnitude of the other numbers and could often be ignored. To minimize the error, the inertia could be calculated along the ramp as close as possible to the plateau. 
     Another, and for the current purposes, a more important shortcoming is that the prior method required a plateau followed by a ramp to calculate the inertia, which made it practically impossible to calculate the inertia during the final extraction plateau because there was no subsequent ramp. 
     The following methodology provides for not only determining the inertia during any plateau, but doing so continuously, and doing so without the need for a ramp, either before or after the plateau. The methodology determines the inertia of the laundry load during a constant speed phase greater than the satellization speed. During the constant speed phase, periodic signals are applied to the constant speed profile. It has been observed that the inertia of the laundry load may be determined by applying a periodic torque signal to the constant speed profile to split the periodic signal into two ½ wave sections to solve for the inertia of the laundry load by cancelling out damping and friction forces. 
       FIG. 3  illustrates a plot of a periodic torque signal applied to the constant speed profile of the drum  18  during the constant speed phase. The speed profile  90  may be an extraction speed profile to remove the liquid from the laundry load in the treating chamber  20 . The speed profile  90  may include an initial acceleration phase that may be linear, indicating a constant acceleration. The acceleration phase  90  may be configured to increase the rotational speed up to or exceeding a satellizing speed  100 , at which most of the laundry sticks to the interior drum wall due to centrifugal force. As used herein, the term satellizing speed refers to any speed where at least some of the laundry load satellizes, not just the speed at which satellizing is first observed to occur. 
     The speed profile  90  may transition from the initial acceleration phase  90  to a speed plateau  92  in excess of the satellizing speed  100 . A periodic torque signal  96  may be superimposed on the speed plateau  92  to determine the inertia of the laundry load during the constant speed plateau  92 . For example, the torque from the motor  30  may be configured to periodically increase and decrease by communicating with the motor torque sensor  68  and/or the controller  14 . As a result, the resulting torque profile may be in the form of a periodic trace, such as the sinusoidal profile  96 , or a saw tooth profile (not shown). The sinusoidal profile  96  may have a constant period  98 , and may comprise a plurality of periods. The period  98  may be bisected at a maximum  94 ,  97  into a first half period representing a positive acceleration and a second half period representing a negative acceleration. The first half period may correspond to an increasing trace of the sinusoidal profile  96 . The second half period may correspond to a decreasing trace of the sinusoidal profile  96 . The first half period and the second half period may be symmetrical with respect to the speed plateau  92 . 
     The torque may be determined individually for the first and second half periods. For example, utilizing the relationship expressed in equation (1), the torque for the first half period and the second half period may be determined in the following manner:
 
τ first   =J*{dot over (ω)}+B*ω+C   (3)
 
τ second   =J *(−{dot over (ω)})+ B*ω+C   (4)
 
     The difference between the torque of the motor  30  for a first half period and the torque of the motor  30  for the second half period may be represented in the following equation:
 
τ first −τ second   =J*{dot over (ω)}+B*ω+C −( J *(−{dot over (ω)})+ B*ω+C )=2* J *{dot over (ω)}  (5)
 
     Equation (5) may be solved for inertia, J, so that:
 
 J =(τ first −τ second )/2*{dot over (ω)}  (6)
 
     Both τ first  and τ second  may be determined by the motor torque sensor  68  and/or controller  14 , and the acceleration {dot over (ω)} may be a known value, such as the acceleration provided by the controller  14  to the motor  30 , or may be determined by a suitable sensor. Therefore, the equation (6) may be solved for the inertia after superimposing each single period  98  of the periodic signal  96  to the speed profile  90  during the constant speed plateau  92 . 
     The inertia may also be updated after applying every single period  98  to the periodic signal  96 . Alternatively, the inertia may be updated at a predetermined interval during an constant speed phase. For example, the inertia may be updated after completion of every two, three, or other multiple periods. The inertia may be updated by adjusting the frequency or amplitude of the periodic torque signal  96 . 
     As the extraction progresses, the inertia may decrease in an asymptotic manner. This asymptotic decay in inertia may be continuously monitored by utilizing the methodology described above until the inertia reaches a reference value representing an optimal extraction time and residual moisture content. 
     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation. Reasonable variation and modification are possible within the scope of the forgoing disclosure and drawings without departing from the spirit of the invention which is defined in the appended claims.