Abstract:
A washing machine spin balancing control includes a sensor for sensing vibration of the washing machine cabinet. The floor permits the cabinet to vibrate during the rotation of the basket, the controller senses this vibration and reduces the speed of the basket in response to the vibration caused by imperfections in the floor.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to an appliance spin control and method adaptable to floor structure.  
           [0002]    Washing machine appliances include washing baskets that spin about a basket axis during one or more washing machine cycles. Weak, unstable or unlevel supporting floors often cause a washing machine to become unbalanced, and therefore it is necessary to provide a system which compensates for a lack of rigidity, stability, or levelness of the floor below the machine. Because the floor condition will vary from one washing machine installation to another, it is desired in accordance with the present invention to have the machine automatically adjust the rotational speed of the basket in relation to the characteristics of the supporting floor.  
           [0003]    Therefore a primary object of the present invention is the provision of an improved appliance spin control and method which automatically adjusts the spin of the washing basket in response to the particular characteristics of the supporting floor structure.  
           [0004]    A further object of the present invention is the provision of a spin balance control that utilizes a vibration sensor attached to the washing machine cabinet for sensing the vibration of the cabinet during rotation of the washing machine basket.  
           [0005]    A further object of the present invention is the provision of a spin control which adjusts the rotational speed of the basket to prevent unbalance vibration for each variation of supporting floor structure.  
           [0006]    A further object of the present invention is the provision of an improved appliance spin control and method which are economical in manufacture, durable in use, and efficient in operation.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    The foregoing objects may be achieved by a washing machine spin balancing system comprising in combination a support floor and a washing machine cabinet supported on the support floor. A washing machine basket is mounted within the cabinet for rotation about a basket axis. A drive is connected to the basket for causing rotation of the basket. The drive is capable of rotating the basket at a high rotational speed or alternative at one or more low rotational speeds slower than the high rotational speed. A vibration sensor is attached to the cabinet for sensing the vibration of the cabinet. A controller is connected to the sensor and to the drive. The controller is adapted to cause the drive to rotate the basket at the high rotation speed in response to the vibration sensor sensing less than a predetermined amount of vibration of the cabinet. The controller is adapted to cause the drive to rotate the basket at a low rotational speed in response to the vibration sensor sensing more than the predetermined amount of vibration of the cabinet.  
           [0008]    According to one feature of the invention the vibration sensor comprises an accelerometer. However, the particular structure of the accelerometer or vibration sensor may vary without detracting from the invention. All that is required is that the vibration sensor be capable of sensing the vibration of the washing machine cabinet.  
           [0009]    According to another feature of the invention, the slower rotational speed is approximately 67% of the higher rotational speed.  
           [0010]    The foregoing control system permits the reduction of the rotational speed of the basket in response to various types of floors. A floor with imperfections causes the threshold unbalance vibration to be reached more easily at the higher rotational speed than would be the case if the floor were without these imperfections.  
           [0011]    According to another feature of the invention, the method comprises placing the washing machine cabinet on a floor having unique characteristics of stability, strength, and levelness which affect the magnitude of vibration of the washing machine cabinet in response to rotation of the basket within the washing machine cabinet. A drive is used to rotate the washing machine basket at a first rotational speed. During rotation a sensor senses the magnitude of vibration of the washing machine cabinet. A controller connected to the vibration sensor and to the drive causes the drive to reduce the rotational speed of the basket to a second rotational speed slower than the first rotational speed in response to the sensed magnitude of vibration of the washing machine basket exceeding a predetermined magnitude of vibration. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a schematic pictorial view of a washing machine having a rotatable washing machine basket therein.  
         [0013]    [0013]FIG. 2 is a pictorial view of an example of an accelerometer that may be used with the present invention.  
         [0014]    [0014]FIG. 3 is a block diagram showing the interrelationship of the sensor, the controller and the drive motor.  
         [0015]    [0015]FIG. 4 is a flow diagram showing the method for controlling rotational speed of the basket. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Referring to the drawings the numeral  10  designates a washing machine cabinet. Cabinet  10  includes cabinet feet  12  which are shown schematically, and which support the cabinet  10  on a supporting floor  14 . The structure of the feet  12  is intended to be shown only in a schematic sense, and various types of supporting legs, feet or devices are used with washing machines to support the washing machine cabinet on a supporting floor.  
         [0017]    Many supporting floors differ in their characteristics. Some floors are not level. Others are weak and likely to vibrate in response to vibration of the cabinet. Others may have depressions or other weak parts which cause the cabinet  10  to vibrate more easily than would be the case if the cabinet were supported on a level sturdy floor.  
         [0018]    A basket  16  is rotatably mounted with the cabinet  10  and is driven by a drive motor  18  shown schematically in FIG. 1. Mounted on the cabinet  10  is a controller  20  for controlling the drive motor. Also mounted on the cabinet  10  is a sensor box  22 . Within sensor box  22  is a sensor  24  which is adapted to sense the vibration of the cabinet  10 .  
         [0019]    The preferred vibration sensor  24  is an accelerometer such as shown in FIG. 2. The accelerometer  24  in FIG. 2 is electronically connected to the controller  20  and is mounted on cabinet  10  to sense machine vibration. Although the accelerometer can be positioned in a variety of different locations about the washing machine cabinet  10 , mounting the accelerometer  24  toward the top of the washing machine cabinet  10  has been found to produce the most reliable results. The accelerometer includes a piezoelectric film  26  with a mass  28  attached to the end of the film  26 . Leads  30  are also attached to the film  26 . The accelerometer  24  is well suited for measuring vibration because acceleration of the mass  28  and the vibration of the cabinet  10  are proportional. The accelerometer  24  shown in FIG. 2 is only an example, and other forms of accelerometers or vibration sensors may be used without detracting from the invention.  
         [0020]    Referring to FIG. 3 the sensor or accelerometer  24  is connected electrically to the controller  20 , and the controller  20  is also connected to the drive motor  18 . Drive motor  18  is adapted to rotate the basket  16  at two or more different speeds. The normal speed is the fastest, but if an unbalance situation arises where the vibration of cabinet  10  is too great then the motor  18  is capable of reducing the rotational speed of the basket to one or more lesser speeds.  
         [0021]    [0021]FIG. 4 shows a flow diagram of the method of the present invention. The numeral  32  refers to the start of the method. After the start the motor  18  rotates the basket  16  at its normal high speed. This step is identified by the numeral  34 .  
         [0022]    The numeral  36  refers to the sensing of the vibration of the cabinet  10  by means of the accelerometer  24 . The numeral  38  refers to the analysis done by the controller  20  to determine whether or not the sensed vibration exceeds a predetermined magnitude representing undesirable unbalance situations. The numeral  40  represents a “no” analysis that the vibration is below the unbalance condition. In that situation the controller  20  causes the motor  18  to continue rotating the basket  16  at its highest speed.  
         [0023]    However, if an unbalance condition is sensed at any time during the rotation of the device, as represented by the numeral  42 , the controller automatically causes the drive  18  to reduce the rotational speed of the basket to a slower rotating speed. There may be only a single slower rotating speed, or there may be multiple rotating speeds in descending order, all less than the initial rotating speed represented by the numeral  34 .  
         [0024]    During the rotation at the slower speed, the accelerometer continues to sense the vibration of the machine, and if the vibration ceases, the controller can again initiate the rotation of the basket  16  at the faster speed.  
         [0025]    The controller may set so that it continues at the slower speed, or it can be set so that after a pre-determined time frame it could retry to attain the faster speed. As it accelerates from the slower speed to the faster speed, the sensor may sense the vibration and switch back to the slower speed. It is not required that the faster speed be used for adequate performance.  
         [0026]    The advantage of the present invention is that the controller automatically adjusts the rotational speed of the basket  16  in relation to the type of floor  14  upon which the cabinet  10  is supported. If the floor is weak or not level, the vibration sensed by the sensor  24  reaches the predetermined unbalance condition very easily, thereby causing the controller to reduce the speed of the basket. On other floors that provide a better supporting surface, there may be little or no sensing of an unbalance condition, and the basket continues to rotate at its higher speed. Furthermore, if at some time during the spin cycle the contents of the basket  16  become unevenly distributed, an unbalance condition may arise, and the controller will automatically reduce the speed of the basket during this temporary unbalance condition.  
         [0027]    In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in the form and the proportion of parts as well as in the substitution of equivalents are contemplated as circumstances may suggest or render expedient without departing from the spirit or scope of the invention as further defined in the following claims.