Abstract:
Systems and methods for controlling locking of a washing machine lid are described. The washing machine includes an agitation element and a basket. The method, in one example embodiment, comprises the steps of sensing a spin speed associated with a spin speed of at least one of the agitation element and the basket, and causing the lid to be locked when the sensed spin speed exceed a first predetermined speed.

Description:
BACKGROUND OF INVENTION  
         [0001]    This invention relates generally to washing machines, and more particularly, to methods and systems for locking a washing machine lid.  
           [0002]    Washing machines typically include a cabinet that houses an outer tub for containing wash and rinse water, a perforated clothes basket within the tub, and an agitator within the basket. A drive and motor assembly is mounted underneath the stationary outer tub to rotate the clothes basket and the agitator relative to one another, and a pump assembly pumps water from the tub to a drain to execute a wash cycle. See, for example, U.S. Pat. No. 6,029,298.  
           [0003]    With at least some motor assembly configurations, the spin speed can exceed 600 rpm. At a predetermined upper spin speed, the washer lid is locked and at a predetermined lower spin speed, the washer lid is unlocked. For example, and in one configuration, the lid is locked at spin speeds of 100 rpm and higher and is unlocked at spin speeds of 50 rpm and lower.  
           [0004]    When in spin, the basket and tub spin in one direction. When in agitate, the basket is held in a stationary position with a brake and the agitator spins in both directions. The brake, however, may not hold completely and as a consequence, the speed sensed by the speed sensor may oscillate at apparent speeds approaching the 50 to 100 rpm range, resulting in locking the washer lid even though the actual spin speed is well below 50 rpm.  
         SUMMARY OF INVENTION  
         [0005]    In one aspect, a method for controlling locking a washing machine lid is provided. The washing machine includes an agitation element and a basket. The method, in one example embodiment, comprises the steps of sensing a spin speed associated with at least one of the agitation element and the basket, and causing the lid to be locked when the sensed spin speed exceeds a first predetermined speed.  
           [0006]    In another aspect, a lid lock system for a washing machine is provided. The washing machine includes an agitation element, a basket, and a transmission and clutch system. The transmission and clutch system includes a drive shaft coupled to the agitation element and basket for causing the agitation element and basket to spin. The lid lock system comprises a sensor for generating an output signal associated with a spin speed of at least one of the agitation element and basket, a lid lock solenoid for controlling operation of a lid lock, and a control circuit for energizing the lid lock solenoid based on the sensor output signal. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0007]    [0007]FIG. 1 is a perspective cutaway view of an exemplary washing machine.  
         [0008]    [0008]FIG. 2 is front elevational schematic view of the washing machine shown in FIG. 1.  
         [0009]    [0009]FIG. 3 is a schematic block diagram of a control system for the washing machine shown in FIGS. 1 and 2.  
         [0010]    [0010]FIG. 4 is a schematic illustration of a sensor assembly including two sensors and one magnet secured to a drive shaft.  
         [0011]    [0011]FIG. 5 is a schematic illustration of another sensor assembly including one sensor and two magnets secured to a drive shaft.  
         [0012]    [0012]FIG. 6 is a circuit schematic diagram of a frequency to voltage converter.  
         [0013]    [0013]FIG. 7 is a circuit schematic diagram of an alternative frequency to voltage converter. 
     
    
     DETAILED DESCRIPTION  
       [0014]    [0014]FIG. 1 is a perspective view partially broken away of an example washing machine  50  including a cabinet  52  and a cover  54 . A backsplash  56  extends from cover  54 , and a control panel  58  including a plurality of input selectors  60  is coupled to backsplash  56 . Control panel  58  and input selectors  60  collectively form a user interface input for operator selection of machine cycles and features, and in one embodiment a display  61  indicates selected features, a countdown timer, and other items of interest to machine users. A lid  62  is mounted to cover  54  and is rotatable about a hinge (not shown) between an open position (not shown) facilitating access to a wash tub  64  located within cabinet  52 , and a closed position (shown in FIG. 1) forming a sealed enclosure over wash tub  64 . As illustrated in FIG. 1, machine  50  is a vertical axis washing machine.  
         [0015]    Tub  64  includes a bottom wall  66  and a sidewall  68 , and a basket  70  is rotatably mounted within wash tub  64 . A pump assembly  72  is located beneath tub  64  and basket  70  for gravity assisted flow when draining tub  64 . Pump assembly  72  includes a pump  74  and a motor  76 . A pump inlet hose  80  extends from a wash tub outlet  82  in tub bottom wall  66  to a pump inlet  84 , and a pump outlet hose  86  extends from a pump outlet  88  to an appliance washing machine water outlet  90  and ultimately to a building plumbing system discharge line (not shown) in flow communication with outlet  90 .  
         [0016]    [0016]FIG. 2 is a front elevational schematic view of washing machine  50  including wash basket  70  movably disposed and rotatably mounted in wash tub  64  in a spaced apart relationship from tub side wall  64  and tub bottom  66 . Basket  12  includes a plurality of perforations therein to facilitate fluid communication between an interior of basket  70  and wash tub  64 .  
         [0017]    A hot liquid valve  102  and a cold liquid valve  104  deliver fluid, such as water, to basket  70  and wash tub  64  through a respective hot liquid hose  106  and a cold liquid hose  108 . Liquid valves  102 ,  104  and liquid hoses  106 ,  108  together form a liquid supply connection for washing machine  50  and, when connected to a building plumbing system (not shown), provide a fresh water supply for use in washing machine  50 . Liquid valves  102 ,  104  and liquid hoses  106 ,  108  are connected to a basket inlet tube  110 , and fluid is dispersed from inlet tube  110  through a known nozzle assembly  112  having a number of openings therein to direct washing liquid into basket  70  at a given trajectory and velocity. A known dispenser (not shown in FIG. 2) may also be provided to produce a wash solution by mixing fresh water with a known detergent or other composition for cleansing of articles in basket  70 .  
         [0018]    In an alternative embodiment, a known spray fill conduit  114  (shown in phantom in FIG. 2) may be employed in lieu of nozzle assembly  112 . Along the length of the spray fill conduit  114  are a plurality of openings arranged in a predetermined pattern to direct incoming streams of water in a downward tangential manner towards articles in basket  70 . The openings in spray fill conduit  114  are located a predetermined distance apart from one another to produce an overlapping coverage of liquid streams into basket  70 . Articles in basket  70  may therefore be uniformly wetted even when basket  70  is maintained in a stationary position.  
         [0019]    An agitation element  116 , such as a vane agitator, impeller, auger, or oscillatory basket mechanism, or some combination thereof is disposed in basket  70  to impart an oscillatory motion to articles and liquid in basket  70 . In different embodiments, agitation element  116  may be a single action element (i.e., oscillatory only), double action (oscillatory movement at one end, single direction rotation at the other end) or triple action (oscillatory movement plus single direction rotation at one end, singe direction rotation at the other end). As illustrated in FIG. 2, agitation element  116  is oriented to rotate about a vertical axis  118 .  
         [0020]    Basket  70  and agitator  116  are driven by motor  120  through a transmission and clutch system  122 . A transmission belt  124  is coupled to respective pulleys of a motor output shaft  126  and a transmission input shaft  128 . Thus, as motor output shaft  126  is rotated, transmission input shaft  128  is also rotated. Clutch system  122  facilitates driving engagement of basket  70  and agitation element  116  for rotatable movement within wash tub  64 , and clutch system  122  facilitates relative rotation of basket  70  and agitation element  116  for selected portions of wash cycles. Motor  120 , transmission and clutch system  122  and belt  124  collectively are referred herein as a machine drive system.  
         [0021]    Washing machine  50  also includes a brake assembly (not shown) selectively applied or released for respectively maintaining basket  70  in a stationary position within tub  64  or for allowing basket  70  to spin within tub  64 . Pump assembly  72  is selectively activated to remove liquid from basket  70  and tub  64  through drain outlet  90  and a drain valve  130  during appropriate points in washing cycles as machine  50  is used. In an exemplary embodiment, machine  50  also includes a reservoir  132 , a tube  134  and a pressure sensor  136 . As fluid levels rise in wash tub  64 , air is trapped in reservoir  132  creating a pressure in tube  134  that pressure sensor  136  monitors. Liquid levels, and more specifically, changes in liquid levels in wash tub  64  may therefore be sensed, for example, to indicate laundry loads and to facilitate associated control decisions. In further and alternative embodiments, load size and cycle effectiveness may be determined or evaluated using other known indicia, such as motor spin, torque, load weight, motor current, and voltage or current phase shifts.  
         [0022]    Operation of machine  50  is controlled by a controller  138  which is operatively coupled to the user interface input located on washing machine backsplash  56  (shown in FIG. 1) for user manipulation to select washing machine cycles and features. In response to user manipulation of the user interface input, controller  138  operates the various components of machine  50  to execute selected machine cycles and features.  
         [0023]    In an illustrative embodiment, clothes are loaded into basket  70 , and washing operation is initiated through operator manipulation of control input selectors  60  (shown in FIG. 1). Tub  64  is filled with water and mixed with detergent to form a wash fluid, and basket  70  is agitated with agitation element  116  for cleansing of clothes in basket  70 . That is, agitation element is moved back and forth in an oscillatory back and forth motion. In the illustrated embodiment, agitation element  116  is rotated clockwise a specified amount about the vertical axis of the machine, and then rotated counterclockwise by a specified amount. The clockwise/counterclockwise reciprocating motion is sometimes referred to as a stroke, and the agitation phase of the wash cycle constitutes a number of strokes in sequence. Acceleration and deceleration of agitation element  116  during the strokes imparts mechanical energy to articles in basket  70  for cleansing action. The strokes may be obtained in different embodiments with a reversing motor, a reversible clutch, or other known reciprocating mechanism.  
         [0024]    [0024]FIG. 3 is a schematic block diagram of an exemplary washing machine control system  150  for use with washing machine  10  (shown in FIG. 2). Control system  150  includes controller  138  which may, for example, be a microcomputer  140  coupled to a user interface input  141 . An operator may enter instructions or select desired washing machine cycles and features via user interface input  141 , such as through control interface  58  (shown in FIG. 1). A memory  142  is also coupled to microcomputer  140  and stores instructions, calibration constants, and other information as required to satisfactorily complete a selected wash cycle. Memory  142  may, for example, be a random access memory (RAM). In alternative embodiments, other forms of memory could be used in conjunction with RAM memory, including but not limited to electronically erasable programmable read only memory (EEPROM).  
         [0025]    Power to control system  150  is supplied to controller  138  by a power supply  146  configured to be coupled to a power line L. Analog to digital and digital to analog converters (not shown) are coupled to controller  138  to implement controller inputs and executable instructions to generate controller output to washing machine components such as those described above in relation to FIGS. 1 and 2. More specifically, controller  138  is operatively coupled to machine drive system  148  (e.g., motor  120  and clutch system  122  shown in FIG. 2), a brake assembly  151  associated with basket  70  (shown in FIG. 2), machine water valves  152  (e.g., valves  102 ,  104  shown in FIG. 2) and machine drain system  154  (e.g., drain pump assembly  72  and/or drain valve  130  shown in FIG. 2) according to known methods. In a further embodiment, water valves  152  are in flow communication with a dispenser  153  (shown in phantom in FIG. 3) so that water may be mixed with detergent or other composition of benefit to washing of garments in wash basket  70  (shown in FIG. 1).  
         [0026]    In response to manipulation of user interface input  141  controller  138  monitors various operational factors of washing machine  10  with one or more sensors or transducers  156 , and controller  138  executes operator selected functions and features according to known methods. Of course, controller  138  may be used to control washing machine system elements and to execute functions beyond those specifically described herein.  
         [0027]    With regard to lid locking operations, when the spin speed of agitator  116  or basket  70 , or both, exceeds a first predetermined speed, the washer lid is locked, and when agitator  116  and basket  70  spin speeds are below a second predetermined speed, the washer lid is unlocked. The spin speed can be detected, for example, by placing a magnet on the drive shaft extending from clutch system  122  and coupled to basket  70  and agitator  116 , and positioning a sensor so that the sensor generates a signal (e.g., a pulse) each time the magnet rotates by the sensor. By counting the number of pulses during a predefined period of time, the speed of the drive shaft can be detected. Since the speed of the drive shaft is associated with the spin speed of basket  70  and/or agitator  116 , the sensor signal can be used to control locking of the lid. For example, and in one specific embodiment, when the sensor signal represents a spin speed in excess of 100 revolutions per minute, the washer lid should be locked and when the sensor signal represents a spin speed below 50 revolutions per minute, the lid should be unlocked.  
         [0028]    During agitation operation, however, an oscillation effect may impact the accuracy of the sensed speed. Specifically, during agitation, basket  70  is held in a stationary position with a brake and agitator  116  spins in both directions. The brake intended to hold basket  70  stationary, however, may not hold completely and as a consequence, the speed represented by the signal generated by the sensor may oscillate at apparent speeds approaching the 50 to 100 rpm range, resulting in locking the washer lid even though the actual spin speed is well below 50 rpm.  
         [0029]    To protect against the impact of the oscillation effect on the accuracy of the sensed speed, multiple sensors can be used to detect drive shaft rotation. Specifically, and referring to FIG. 4, a magnet  200  is mounted to drive shaft  202 , and two sensors  204  and  206  spaced about 180 degrees apart are positioned to generate a pulse signal when magnet  200  passes thereby. With such multiple sensor configuration, a pattern of signals can be expected during agitation operation. That is, after energizing first sensor  204 , second sensor  206  is energized before first sensor  204  is again energized. By placing sensors  204  and  206  far enough apart, the oscillation of basket  70  will not affect the accuracy of the speed determined from the sensor signals.  
         [0030]    With a two sensor configuration as shown in FIG. 4, a circuit that accepts only one signal from sensor  204  and then expects a signal from sensor  206  before accepting another signal from sensor  204  is used. One such circuit is an R S flip flop. The output of the flip flop is a square wave. The flip flop output during agitate operation would remain either positive or negative with occasional changes at the same rate as the basket precess rate.  
         [0031]    Referring to FIG. 5, and rather than a two sensor configuration, a one sensor  210 , two magnet  212  and  214  configuration can be used. Specifically, by placing two magnets  212  and  214  on shaft  202  with opposite polarities and 180 degrees apart, a single latching Hall sensor  216  is positioned to generate signals representative of rotation of shaft  202  without being significantly impacted by the oscillation effect. That is, agitate oscillations are not sensed unless shaft  202  oscillates by greater than about 150 degrees.  
         [0032]    The square wave output generated by sensor  216  illustrated in FIG. 5 or the combined output of sensors  204  and  206  illustrated in FIG. 4 through an R S flip flop, is used to control the lid lock solenoid. Specifically, the lid lock solenoid is energized at a first predetermined speed, e.g., at about 100 rpm, and is de-energized at a second predetermined speed, e.g., at about 50 rpm. When the lid lock solenoid is energized, the lid lock closes. When the lid lock solenoid is de-energized, the lid lock opens.  
         [0033]    For frequency detection, i.e., detection of the square wave output generated by the sensor(s), and in one embodiment, a frequency to voltage converter is used. An example converter is illustrated in FIG. 6, which is a circuit diagram of a LM2917 frequency to voltage converter  220 . Converters such as the LM2917 converter are commercially available, for example, from National Semiconductor Corporation, Santa Clara, Calif. Converter  220  detects a frequency and switches a load  222  (e.g., the lid lock solenoid) whenever the frequency is above a value dependent on capacitor C and resistor R. With a capacitor C of 1 uF and a frequency equivalent to 75 rpm, the equation f IN &gt;1/[2 RC] yields a resistance value R of 400 K ohms. Note that if the converter is not rated to operate at this low a frequency, a value of 1 uF for capacitor C may be large enough to make the response time too long.  
         [0034]    An alternative circuit for frequency detection is illustrated in FIG. 7. In this circuit, a 555 timer  250  is used as a missing pulse detector and will reset a 7474 flip flop  252  if the next pulse doesn&#39;t come within a defined amount of time. The combination of 7474 flip flops  252  and  254  then delays sending a valid output until 2 cycles of the input have completed at a frequency above the missing pulse detector&#39;s threshold value. Therefore, an output occurs only when the frequency output of the sensor (e.g., sensor  216  (FIG. 5)) is high enough to disable the missing pulse detector. Thus, the output should energize the lid lock solenoid at about 75 rpm. Timers such as the 555 timer and flip flops such as the 7474 flip flops are well known and commercially available for example, from National Semiconductor Corporation, Santa Clara, Calif. (for a 555 timer) and from Fairchild Semiconductor Corporation, South Portland, Maine (for a 7474 flip flop).  
         [0035]    The lid lock circuits described herein include sensor-magnet assemblies as shown in FIGS. 4 and 5, and frequency to voltage converters as shown in FIGS. 6 and 7. Of course, other embodiments and combinations are possible. For example, controller  138  can be configured to determine spin speed from a sensor assembly and to directly control the lid lock solenoid.  
         [0036]    The above described systems and methods facilitate lid locking operation when the spin speed of agitator or basket exceeds a first predetermined speed, and unlocking of the washer lid with the agitator or basket spin speed is below a second predetermined speed. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.