Patent Abstract:
A method and apparatus for sensing the water level and vibration for a washing machine are disclosed. The method includes the steps of measuring a resonant frequency, when a water level of a washtub corresponds to the water level of zero and there is no wash within the washtub, in a water level sensor which converts the variation of water pressure according to the water level of the washtub into the resonant frequency and senses the water level as the converted resonant frequency, setting the measured resonant frequency as a reference resonant frequency, measuring the resonant frequency from the water level sensor, during a dehydration operation among washing operations, and obtaining a deviation of the measured resonant frequency from the reference resonant frequency, and comparing the deviation of the measured resonant frequency from a deviation of the reference resonant frequency to determine whether the dehydration operation is continued, for thereby achieving an optimal washing operation, wherein the method is comprised of the step of sensing the excessive vibration within the washing machine only with an output of existing water level sensor, without having a mechanical vibration sensor.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for sensing a water level and vibration of a washtub for a washing machine based the amount of a laundry, and in particular, to a method and apparatus for accurately sensing a water level and vibration by detecting an abnormal vibration caused by an inclination of the laundry during a dehydration process of a washing control mode as a LC resonant frequency for thereby optimizing a washing control operation and implementing an accurate detection of a water level and vibration of a washing machine. 
     2. Description of the Background Art 
     Generally, a washing machine is designed to detect the amount of a laundry in a washtub. When the amount of the laundry is detected, the water level, the amount of a detergent, and the entire washing time are determined based on the thusly detected amount of the laundry. 
     Based upon the total washing time required, the washing machine executes a washing operation in which the water within the washtub swirls based on the operation of a pulsator to form a frictional force against the laundry for thereby washing the laundry. 
     After the washing operation, the washing machine discharges the polluted water to the outside of the washtub and then execute a rinsing operation in which a fresh water is supplied into the washtub to rinse the laundry by the preset number of times. 
     After the rinsing operation, the washing machine discharges the water to the outside of the washtub and then executes a dehydration operation in which an induction motor rotates at a certain high speed for thereby dehydrating the laundry based on a centrifugal separation force. 
     In the washing operation control of the washing machine, at an initial washing stage, the washing machine opens a water supply valve to receive a certain amount of water in accordance with the amount of the laundry within the washtub, until the water level reaches a set water level. At this time, as a water level sensing method, there is known a sensing method in which a LC resonant frequency is varied based on the pressure of water supplied within the washtub. 
     By way of example, if the pressure of water supplied within the washtub is varied, the LC resonant frequency is varied correspondingly thereto. Then, after the varied LC resonant frequency has been measured, the water level corresponding to the amount of the laundry is determined and the water supply valve is closed to stop the supply of water for thereby implementing a proper water level. 
     During the dehydration operation, since the motor is typically set to rotate at a high speed of about 1700 rotations per minute, a great centrifugal force is generated and drastically affects the laundry within the dehydration tub to thereby cause a strong vibration or noise. Meanwhile, the vibration can not be fully absorbed by means of a balancing device such as a snubber bar which is installed at an upper end portion of the washtub. 
     In addition, the rotation of the dehydration tub is stopped in accordance with a control of the induction motor. However, since the rotating force caused due to inertia is varied in accordance with the amount of the washing water, the rotation of the dehydration tub is temporarily decreased. In the case that the induction motor is stopped, it is gradually increased. Accordingly, it fails to control the rotation of the dehydration tub to prevent the generation of the vibration and noises. 
     To overcome the above problems, an improved washing machine capable of sensing the water level and vibration within the washtub during the washing operation is disclosed. 
     The above improved washing machine has a water level sensor and a vibration sensor. For instance, during the washing and rinsing operations, the water level sensor serves to supply and sense the optimal water level within the washtub, and during the dehydration operation, the vibration sensor functions to sense the vibration generated in the washing machine. 
     FIGS. 1 to  6  illustrate a conventional washing machine in which a water level sensor and a vibration sensor are installed independently. 
     As shown therein, the washing machine including a water level sensor and a vibration sensor includes a tank  100  installed within a casing  102  and having an opened top portion and a closed bottom portion, a snubber bar  107  lying between dampers  108  which are respectively assembled at the upper portion of the casing  102  and the lower portion of the tank  100  for absorbing the impact of the tank  100 , a washing and dehydration tub (hereinafter, called as a washtub)  101  installed in the interior of the tank  100  and mounted in a coaxial state with the tank  100  to execute the washing and dehydration operations, the washtub forming a plurality of conically shaped holes on the surface thereof, an induction motor  103  installed at a lower portion of the outer surface of the tank  100  for implementing a reverse rotation, a clutch  104  assembled with the induction motor  103  by means of a pulley belt  105  for delivering and decelerating the rotating force of the induction motor  103 , a pulsator  106  rotatably installed on the inner bottom surface of the washtub  101  and interposed between the washtub  101  and the clutch  104  for swirling the water within the washtub  101 , a water supply valve  109  connected with a water supply path installed at the upper portion of the tank  100  for supplying the water into the washtub  101 , a water discharging valve  110  installed on the bottom surface of the tank  100  for discharging the polluted water to the outside of the washtub  101 , a vibration sensor  112  installed on the inner surface of one side of the upper portion of the casing  102  for sensing the vibration formed by the contact with the tank  100  due to an eccentric rotation of the washtub  101  in accordance with an eccentrically formed laundry in a certain direction, a water pressure transfer path  113  having one end connected to the lower surface of the tank  100  and the other end vertically extended to the upper portion of the tank  100  for transferring the water pressure generated in accordance with the variation of the water level within the washtub  101 , a water level sensor  111  installed at the other end of the water pressure transfer path  113  for changing and outputting an inherent inductance in accordance with the transferred water pressure, a waveform shaping unit  116  for applying a fixed capacitance to the changed value of the inherent inductance to thereby generate a resonant frequency and for then stabilizing the generated resonant frequency with a voltage waveform to thereby amplify and output the resonant frequency, and a microprocessor  114  for determining the vibration and the water level with the vibration sensed by the vibration sensor  112  and the voltage waveform inputted through the waveform shaping unit  116  and for controlling the operation of the induction motor  103  using a motor driving member  115  and the opening and closing operation of the water supply and discharging valves  109  and  110  and a valve driving member  117  in accordance with the determined vibration and the water level. FIGS. 2 and 3 illustrate the detailed configuration of the water level sensor  111  as shown in FIG.  1 . 
     The water level sensor  111  is comprised of a cylindrical housing  10  which has a through hole connected through the water pressure transfer path  113  to the tank  100  at one side thereof and an opening hole at the other side thereof, a bellows  11  which is installed within the housing  10  and is connected to the water pressure transfer path  113  to be extended or expanded in accordance with the pressure of water within the washtub  101 , a shielding member  12  which is sealed at the top portion of the bellows  11  and have a hook shape to shield the water pressure, a cylindrical coil  14  having an inherent inductance value, which is installed at the center portion of the inner wall of the housing  10  to be separated by a predetermined distance in a vertical direction from the shielding member  12 , a cylindrical core  13  which is hooked at the upper portion of the shielding member  12  and moves vertically in the internal space of the coil  14  in accordance with the extension and expansion of the bellows  11  to thereby vary the inherent inductance value of the coil  14 , a cylindrical support member  16  which is assembled at the top end portion of the coil  14  and serves to support the coil  14  against the housing  10 , a cap  17  which is adapted to cover the opening at the top end portion of the support member  16 , and a coil shape spring  15  which is interposed between the top surface of the core  13  and the bottom surface of the cap  17  to restore the core  13  to the original position thereof. 
     The waveform shaping unit  116 , as shown in FIG. 6, is comprised of an amplifier  116   a  which amplifies an input voltage to a substantial voltage size to provide the amplified voltage to the microprocessor  114 , and condensers C 1  and C 2  which are respectively connected in serial with the input and output terminals of the amplifier  116   a  via resistors R 1  and R 2  and feed back the output voltage from the amplifier  116   a  to the input voltage thereof. In this case, the waveform shaping unit  116  is operated based on a LC resonant circuit configuration in such a manner that both terminals a and b of the coil  14  are respectively connected in parallel with the condensers C 1  and C 2 , and the core  13  moves vertically in the internal space of the coil  14 . 
     The vibration sensor  112  such as a safety switch or a limit switch, as shown in FIG. 5, is comprised of first and second voltage discontinuous members  22  and  23  which are respectively installed at the upper portion of the casing  102  and is electrically short-circuited or opened, a switch leg  20  which is hinged to the first voltage discontinuous member  22  to be separated at a predetermined distance from the tank  100  and rotates by the striking of the tank  100  according to the rotation radius of the washtub  101  to electrically short-circuit the first and second voltage discontinuous members  22  and  23 , and a spring  21  which restores the switch leg  20  to the original position thereof to electrically open the first and second voltage discontinuous members  22  and  23 . An explanation of the operation of the conventional washing machine in which the water level sensor and the vibration sensor are installed, respectively will be discussed in detail with reference to FIGS. 1 to  6 . 
     Firstly, if an operation is started after the washing operation has been set through an operational panel (not shown), the microprocessor  114  controls the water supply valve  109 , the water discharging valve  110  and the induction motor  103  through the valve driving member  117  and the motor driving member  115  to thereby execute the washing, rinsing and dehydration operations in a scheduled sequence. 
     At this time, the microprocessor  114  receives an input signal, which is generated in accordance with the operation states of the water level sensor  111  sensing the water level of the washtub  101  and the vibration sensor  112  sensing the vibration of the washtub  101 , and then outputs a control signal in response to the input signal. 
     In this case, the microprocessor  114  meets the following conditions. It recognizes the state where the core  13  of the water level sensor  111 , as will be described in detail, is not advanced into the internal space of the coil  14 , as the state where the water is not retained within the washtub  101 , i.e. the water level of zero, and contrarily, recognizes the state where the core  13  of the water level sensor  111  moves vertically the internal space of the coil  14 , as the state where the water is retained within the washtub  101  based upon the movement of the core  13 . 
     Under the above conditions, the microprocessor  114  controls, for the purpose of supplying the water within the washtub  101  upon an initial washing operation, the valve driving member  117  to open the water feeding valve  109  such as an electronic control valve in accordance with the amount of the laundry retained within the washtub  101 . 
     If the water is fed into the washtub  101 , the water pressure becomes high. Then, the water pressure is applied, through the water pressure transfer path  113  connected to the tank  100 , to the bellows  11  within the housing  10  of the water level sensor  111 . At this time, the shielding member  12 , which is sealed at the upper portion of the bellows  11 , prevents the water pressure from being continuously increased. This results in the generation of pressure expansion. Thereby, the pressure expansion renders the bellows  11  expanded in proportion to the water pressure. 
     Referring to FIG. 4, if the bellows  11  is expanded, the cylindrical core  13 , which is assembled with the shielding member  12 , moves in the internal space of the coil  14  upwardly in the vertical direction, in step ST 10 . The coil  14  has a diameter larger than that of the core  13  and includes the inherent inductance value. The inherent inductance value is varied in accordance with the upward movement of the core  13 , in step ST 20 . For example, the inherent inductance value is increased as the core  13  moves in the internal space of the coil  14  in the upward direction. 
     The inductance variation value of the coil  14  is multiplied by a capacitance value of the condensers C 1  and C 2  of the waveform shaping unit  116  of FIG. 6 to be produced as a predetermined resonant frequency. The resonant frequency is shaped into a voltage waveform by the waveform shaping unit  116  and is then supplied to the microprocessor  114 . 
     In other words, the both terminals a and b of the coil  14  of the water level sensor  111  are respectively connected in parallel with the condensers C 1  and C 2  of the waveform shaping unit  116 . As a result, the waveform shaping unit  116  is operated based on a single LC resonant circuit configuration by the arrangement of the coil  14  and the condensers C 1  and C 2 , thus to generate the resonant frequency, at step ST 30 . 
     Conventionally, the resonant frequency f 0  of the LC resonant circuit is calculated under the following equation:          f   0     =       1     2      π        LC                    [   Hz   ]                            
     The resonant frequency f 0  is amplified by the amplifier  116   a  to a substantial voltage size, and the amplified voltage waveform is provided to the microprocessor  114 . 
     The microprocessor  114  measures the water level within the washtub  101  on the basis of the resonant frequency f 0  of the waveform shaping unit  116  generated based on the inductance variation value of the water level sensor  111 . Then, it determines as to whether the measured water level is optimal to correspond with the amount of the laundry detected. If determined as optimal, it controls the valve driving member  117  to close the water supply valve  107 . 
     Thereafter, it controls the motor driving member  115  to alternatively electrify the induction motor  103 , which renders the pulsator  106  to be forwardly and reversely rotated in turn. 
     As a result, the water within the washtub  101  is swirled, which causes the frictional force against the laundry to be generated, thus to execute the washing operation. 
     If the washing operation is completed, the microprocessor  114  controls the valve driving member  117  to open the water discharging valve  110  and discharges the polluted water to the outside of the washtub  101 . At the time, the water level sensor  111  senses whether the polluted water within the washtub  101  is completely discharged. 
     In other words, during the discharging operation, the water pressure is decreased as the water level within the washtub  101  is low. Accordingly, if the water pressure is increasingly decreased, the bellows  11  is expanded, based upon the elastic force of the spring  15 , which is interposed between the cap  17  and the core  13  of the water level sensor  111 . Moreover, the core  13  gradually descends vertically in the internal space of the coil  14 , thereby returning to the initial position thereof. 
     If the core  13  is returned to the initial position thereof, the inductance value of the coil  14  is also decreased. Hence, the resonant frequency f 0 , which is obtained by multiplying the inductance variation value of the coil  14  by the capacitance value of the condensers C 1  and C 2 , is changed to the initial value thereof and then inputted to the microprocessor  114 . As a result, the microprocessor  114  determines the completion time of the discharging operation. 
     After the completion of the washing operation, the rinsing operation is implemented through the water feeding and discharging to/from the washtub  101 , as mentioned above. 
     For the dehydration operation after the washing and rinsing operations are performed, the microprocessor  114  controls the induction motor  103  to be rotated at a set rotation speed and senses the vibration generated within the washtub  101  due to the rotation of the induction motor  103  by means of the vibration sensor  112  as shown in FIG.  5 . 
     During the dehydration operation, an appropriate balance or an undesirable vibration within the tank  100  is generated in accordance with the collection of the laundry in a certain direction. 
     If the laundry is uniformly disposed at the internal wall of the washtub  101 , the vibration within the washtub  101  caused due to the rotation speed of the induction motor  103  is not generated after a little amount of vibration has been generated. As a result, the washtub  101  finally reaches a normal dehydration speed, while having the same rotation radius centering around the concentric axis. This creates a balancing state where no vibration within the tank  100  is generated, thus to execute the normal dehydration operation during the set time period. 
     On the other hand, if the laundry is inclined at a certain corner of the wall of the washtub  101 , the washtub  101  eccentrically rotates in every direction as the rotation speed is high, and if the eccentric rotation is severe, the tank  100  undesirably strikes against the washtub  101 . 
     The vibration width is increased in accordance with the strength of the striking at the tank  100 , and as shown in FIG. 5, the switch leg  20  of the vibration sensor  112  such as the safety switch or the limit switch is struck at every rotation. Thereby, the switch leg  20  electrically short-circuits or opens the first and second voltage discontinuous members  22  and  23 , while rotating counterclockwise or clockwise by means of the spring  21 . 
     If the microprocessor  114  inputs an electrical signal from any one of the first and second voltage discontinuous members  22  and  23 , it controls the water supply valve  109  to supply the water within the washtub  101  and thus executes an untwisting operation for the laundry during a predetermined time period. Thereby, the laundry can be uniformly disposed on the wall surface of the washtub  101  to thereby reduce the strength of the vibration formed. 
     If the vibration is decreased, the microprocessor  114  controls the motor driving member  115  to rotate the induction motor  103  at a high speed, thereby completing the dehydration operation. 
     Meanwhile, if the microprocessor  114  continuously inputs the electrical signal from the corresponding voltage discontinuous member, after the untwisting operation for the wash, it halts the induction motor  103  to thereby prevent the generation of the over-vibration. 
     It can be appreciated that the water level and vibration sensing device in the conventional washing machine is capable of sensing, during the washing operation for the wash, the water level of the washtub using the LC resonant circuit in which an inductance variation value of the coil within the water level sensor is calculated and sensing, during the dehydration operation for the wash, the vibration within the washtub using the separate vibration senor such as a limit switch. 
     As known, however, since the conventional washing machine should include independent water level sensor and vibration sensor, there are some problems in that the production cost is high and a manufacturing process is complicate. 
     In addition, since the vibration sensor uses mechanical contact points and a spring, there is a problem in that malfunctions may be generated due to the aged deterioration or corrosion of the contact points. Furthermore, it is impossible for the conventional vibration sensor to accurately sense the vibration within the washtub because of the necessity of the adjustment of the intervals of the contact points and the decrement of the restoring force of the spring. 
     By way of example, if the vibration sensor is installed adjacent to the tank, it senses a slight vibration of the tank, which causes the washing machine to execute an unnecessary operation. However, if installed at some distance, it does not sense the vibration until the vibration becomes severe. Therefore, so as to dispose the initial position of the vibration sensor in an accurate manner, an additional production cost should be required and a productivity efficiency may be degraded. 
     Accordingly, there is a need to provide an improved water level and vibration sensing device which can solve the above problems experienced in the conventional washing machine and cam be manufactured with relative low production cost and high reliability. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a method and apparatus for sensing the water level and vibration in a washing machine that substantially obviates one or more of the problems due to limitations and disadvantages of the related arts. 
     An object of the invention is to provide a method and apparatus for sensing the water level and vibration in a washing machine which installs a unitary sensor to accurately sense both the water level and the vibration, thereby achieving an optimal washing operation, wherein the method is comprised of the step of sensing the excessive vibration within the washing machine only with an output of existing water level sensor, without having a mechanical vibration sensor. 
     Another object of the invention is to provide a method and apparatus for sensing the water level and vibration in a washing machine in which an active control in washing and dehydration operations is made by monitoring and suppressing the vibration state and the water level of the washtub therein, wherein the apparatus is comprised of a unitary sensor which is miniaturized and simply configured to accurately sense both the water level and the vibration of the washtub. 
     Still another object of the invention is to provide a method and apparatus for sensing the water level and vibration in a washing machine which can measure the vibration of a washtub, not in one-way direction, but in three-dimensions, to suppress a vibration error rate and can install control members for measuring the vibration in three-dimensions, while maintaining existing water level sensor function. 
     According to an aspect of the present invention, there is provided a method for sensing the water level and vibration in a washing machine which comprises the steps of measuring a resonant frequency, when a water level of a washtub corresponds to the water level of zero and there is no wash within the washtub, in a water level sensor which converts the variation of water pressure according to the water level of the washtub into the resonant frequency and senses the water level as the converted resonant frequency, setting the measured resonant frequency as a reference resonant frequency, measuring the resonant frequency from the water level sensor, during a dehydration operation among washing operations, and obtaining a deviation of the measured resonant frequency from the reference resonant frequency, and comparing the deviation of the measured resonant frequency from a deviation of the reference resonant frequency to determine whether the dehydration operation is continued. 
     According to another aspect of the present invention, there is provided a method for sensing the water level and vibration in a washing machine comprises the steps of moving the internal space of a coil by the variation of water pressure according to the water level of a washtub, during a washing operation, to vary an inherent inductance of the coil, moving the internal space of the coil by the vibration in a horizontal direction according to an eccentric rotation of the washtub, during a dehydration operation, to vary the inherent inductance of the coil, adding a predetermined capacitance value to the inherent inductance variation value, to thereby vary a resonant frequency, and determining the water level and the vibration within the washtub, on the basis of the variation amount of the resonant frequency. 
     Preferably, the amount of variation of the inherent inductance of the coil is defined as ΔL 1 , during the washing operation and as ΔL 2 , during the dehydration operation, under the conditions ΔL 1  &gt;ΔL 2 . 
     According to still another aspect of the present invention, there is provided a method for sensing the water level and vibration in a washing machine comprises the steps of moving the internal space of a coil by the variation of water pressure according to the water level of a washtub, the coil having at least two or more inherent inductance values, to thereby vary any one inherent inductance value of the coil, freely moving a sliding member centering around a support member in which variation area and non-variation area are divided, according to an eccentric rotation of the washtub, to thereby vary at least one or more inherent inductance of the coil including the inherent inductance value for movement in a vertical direction, adding a predetermined capacitance value to the varied inherent inductance variation value, to thereby vary an inherent resonant frequency, and determining the water level and the vibration within the washtub, on the basis of the variation amount of the resonant frequency. 
     Preferably, the non-variation area is occupied by the portion to which the center of the support member is adjacent, and the variation area is occupied by the portion from which the center of the support member is far. In this case, as the sliding member moves toward the variation area, the inherent inductance value of the coil gradually increases. 
     Assuming that the left and right directions relative to a concentric axis of the washtub is designated as ‘X’, the before and behind directions as ‘Y’, and the top and bottom directions as ‘Z’, preferably, the coil has the inherent inductance value in the directions X, Y and Z, respectively. 
     It is desirable that any one of the directions X, Y and Z of the coil is designated as a water level sensing direction and the other as a vibration sensing direction. 
     Assuming that the vibration in the directions X, Y and Z is denoted as Vx, Vy and Vz, and the inherent inductance values in each direction are as Lx, Ly and Lz, the vibration in each direction is given by the following expressions: Vx=f 1  (Lx, Lz), Vy=f 2  (Ly, Lz), and Vz=f 3  (Vz), where coefficients f 1 , f 2  and f 3  are optional functions. 
     According to yet another aspect of the present invention, there is provided an apparatus for sensing the water level and vibration in a washing machine which comprises a sealing state maintaining member installed within a housing connected via a water pressure transfer path to a tank and moving vertically due to the variation of water pressure according to a water level of a washtub, a substantially cylindrical coil unit installed in the center portion of the internal wall of the housing and having an inherent inductance value, a magnetic media assembled on the upper surface of the sealing state maintaining member and moving vertically the internal space of the coil unit according to the variation of the water pressure to thereby vary the inherent inductance value of the coil unit, an inclined support member by a predetermined angle disposed to be separated by a predetermined distance from the top end portion of the magnetic media on the internal space of the coil unit and moving vertically according to the variation of the water pressure, along with the magnetic media, a sliding member made of a predetermined material, having a predetermined diameter, and moving vertically along the inclined surface of the support member according to an eccentric rotation of the washtub, to thereby vary the inherent inductance value of the coil unit, and a waveform shaping unit for adding a predetermined capacitance value to the varied inherent inductance variation value of the coil unit to thereby generate a resonant frequency and stabilizing the resonant frequency in a voltage waveform to selectively measure the amounts of water level and eccentricity in each direction. 
     According to yet still aspect of the present invention, there is provided an apparatus for sensing the water level and vibration in a washing machine which comprises a sealing state maintaining member installed within a housing connected via a water pressure transfer path to a tank and expanding and moving vertically due to the variation of water pressure according to a water level of a washtub, a coil unit installed at the center portion of the internal wall of the housing and having at least two or one inherent inductance values, a magnetic media hook-assembled on the upper surface of the sealing state maintaining member and moving vertically the internal space of the coil unit according to the variation of the water pressure to thereby vary any one of the inherent inductance values of the coil unit, a support member disposed to be separated by a predetermined distance from the top end portion of the magnetic media on the internal space of the coil unit and moving vertically according to the variation of the water pressure, along with the magnetic media, the support member having the upper surface on which a variation area and a non-variation area are divided on the basis of the center portion thereof, a sliding member made of a predetermined material, having a predetermined diameter, and moving freely to the variation area and the non-variation area of the support member according to an eccentric rotation of the washtub, to thereby vary any one of the inherent inductance values of the coil unit, and a waveform shaping unit for adding a predetermined capacitance value to the varied inherent inductance variation value of the coil unit to thereby generate a resonant frequency and stabilizing the resonant frequency in a voltage waveform to selectively measure the amounts of water level and eccentricity in each direction. 
     Assuming that the left and right directions relative to a concentric axis of the washtub is designated as ‘X’, the before and behind directions as ‘Y’, and the top and bottom directions as ‘Z’, preferably, the coil unit takes a substantially square hexahedral shape and is comprised of a coil which winds horizontally in the directions X, Y and Z, respectively, on the square hexahedron in a predetermined winding ratio. 
     Preferably, any one of the coils in the directions X, Y and Z varies the inductance value by the water level and vibration, and the other coils vary the inductance values according to the amount of eccentricity of the washtub, together with the one coil. 
     The upper surface of the support member is formed to have the portions in the left and right directions inclined to have the same angle as each other, on the center portion thereof, to thereby sense the eccentricity in the direction of X in the washtub, where the inclined angle is 20 degrees. 
     Preferably, the upper surface of the support member is rounded to have a smooth inclined surface in a radial direction, on the center portion thereof, to thereby form a spherical inner rounded surface, on which the sliding member moves freely in the radial direction. 
     Assuming that the vibration in the directions X, Y and Z is denoted as Vx, Vy and Vz, and the inherent inductance values in each direction are as Lx, Ly and Lz, the vibration in each direction is given by the following expressions: Vx=f 1  (Lx, Lz), Vy=f 2  (Ly, Lz), and Vz=f 3  (Vz), where coefficients f 1 , f 2  and f 3  are optional functions. 
     It can be from the above description understood that the unitary sensor according to the present invention can sense, during the washing and dehydration operations, both the water level of the washtub and an amount of vibration according to the eccentric rotation of the washtub. 
     As a result, a method and apparatus for sensing the water level and vibration in a washing machine according to the preferred embodiments of the present invention has the following advantages: a) a precise measuring result for the water level and vibration within the washtub can be extracted; b) an error probability of the vibration sensing value and a time period required for the dehydration can be all reduced; and c) installation of a mechanical vibration sensor is not needed. 
     Additional advantages, objects and features of the invention will become more apparent from the description which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 illustrates a side view of a schematic configuration of a conventional washing machine in which a water level sensor and a vibration sensor are installed independently of each other; 
     FIG. 2 illustrates an enlarged sectional view taken in a vertical direction of the water level sensor in FIG. 1; 
     FIG. 3 illustrates an enlarged view of a coil provided to the water level sensor of FIG. 2; 
     FIG. 4 is an exemplary view showing the principles for measuring the water level within the washtub through an amount of variation of the frequency of the water level sensor of FIG. 2; 
     FIG. 5 illustrates a detailed side view of the vibration sensor in FIG. 1; 
     FIG. 6 illustrates a block diagram of a system for controlling a washing operation in accordance with the action of the water level sensor and the vibration sensor in FIG. 
     FIG. 7 illustrates a sectional view taken in a vertical direction of a unitary water level and vibration sensor in a washing machine according to a first embodiment of the present invention; 
     FIG. 8 illustrates an enlarged sectional view of a first support member of FIG. 7, in which a first sliding member moves in every direction according to the left and right impact of the tank and thus senses the vibration within the tank; 
     FIG. 9 illustrates a sectional view taken in a vertical direction of a unitary water level and vibration sensor in a washing machine according to a second embodiment of the present invention; 
     FIG. 10 illustrates an enlarged sectional view of a second support member of FIG. 9, in which a second sliding member moves in every direction according to the left and right impact of the tank and thus senses the vibration within the tank; 
     FIG. 11 illustrates a sectional view taken in a vertical direction of a unitary water level and vibration sensor in a washing machine according to a third embodiment of the present invention; 
     FIG. 12 illustrates an enlarged perspective view of a third support member of FIG. 11, in which a third sliding member moves freely along the inner rounded surface of the third support member according to the impact in every direction of the tank; 
     FIG. 13 illustrates a sectional view taken in a line I—I of FIG. 12; 
     FIG. 14 illustrates an enlarged view of a coil embodied in the second and third embodiments of the present invention; 
     FIG. 15 illustrates a block diagram of a system for controlling a washing operation by sensing both the water level and the vibration at one time through an inductance variation value of the coil embodied in the second and third embodiments of the present invention; and 
     FIGS. 16A and 16B illustrate graph diagrams in which a method for sensing the water level and vibration in a washing machine according to a fourth embodiment of the present invention is applied to FIGS. 2,  3  and  6 , wherein FIG. 16A is a graph diagram illustrating a resonant frequency measurement result during a no-load dehydration and FIG. 16B is a graph diagram illustrating a resonant frequency measurement result in case of a large amount of the wash. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     The present invention includes, of course, a plurality of embodiments, but hereinafter, an explanation on some preferred embodiments of the present invention will be in detail discussed. 
     In the drawings, like numbers indicate the same or similar elements and an explanation of them will be excluded in this detailed description for the sake of brevity. 
     FIG. 7 illustrates a sectional view taken in a vertical direction of a unitary water level and vibration sensor in a washing machine according to a first embodiment of the present invention, and FIG. 8 illustrates an enlarged sectional view of a first support member of FIG. 7, in which a first sliding member moves in every direction according to the left impact of the washing machine and thus senses the vibration therein. 
     In the first embodiment of the present invention, a water level and vibration sensor  200  includes a cylindrical housing  10  perpendicularly installed at an outer wall of a casing and engaged via a tank  100  and a water pressure transfer path  113 , a bellows  11  installed in the housing  10 , connected with the water level transfer path  113 , and retracted and elongated in accordance with a variation of the water pressure based on the water level in the washtub  101 , a shielding member  12  shielded at an upper portion of the bellows  11  and having a hook shape for shielding the transfer of the water pressure, a circular coil  14  having a certain inductance and installed at an inner wall of the housing  10 , a cylindrical core  13  hooked to the upper surface of the shielding member  12  and vertically moving in the interior of the coil  14  in accordance with a retracting is and elongating operation of the bellows  11  for varying a certain inductance of the coil  14 , a cylindrical support member  16  engaged to an upper portion of the coil  14  for supporting the coil to the housing  10 , a cap  17  for capping an open portion of the support member  16 , a coil shape spring  15  vertically engaged at an upper surface of the core  13  and a lower surface of the cap  17  for returning the position of the core  13  to its original position, a first support member  201  installed in the interior of the coil  14  at a certain distance from the upper portion of the core  13 , vertically moving together with the core  13  based on the retracting and elongating operation of the bellows  11  and having its upper surface having an inclination  201   a , and a first sliding member  202  having a diameter of about 3 mm through 5 mm, horizontally and vertically moving along the inclination surface  201   a  of the first support member  201  by an eccentric rotation of the washtub  101  and varying the inductance of the coil  14 . Both terminals a and b of the coil  14  are parallely connected between the condensers C 1  and C 2  as shown in FIG. 6, so that a waveform shaping unit  116  operates as a LC resonant circuit when the core  13  and the first sliding member  202  vertically move in the interior of the coil  14  and along the inclination surface  201   a  of the first support member  201 . 
     The water level and vibration sensing apparatus according to the first embodiment of the present invention operates as follows with respect to the detection of the vibration level due to the water level and an inclination of the laundry without a sensing error during a washing and dehydration process in the washing control operation. 
     The first embodiment of the present invention will be explained in more detail with reference to the accompanying drawings. 
     First, when a washing process, a rinsing process, and a dehydration process are set using an operation panel (not shown), the microprocessor  114  controls the water supply valve  109 , the dehydration valve  110 , and the induction motor  103  based on the valve driving unit  117  and the motor driving unit  115  for thereby implementing the set washing, rinsing and dehydration processes. At this time, at an initial stage of the washing process, the microprocessor  114  opens the water supply valve  109  using the valve driving unit  117  based on the amount of the laundry in the washtub  101  and supplies water into the washtub  101 . 
     When water is supplied into the washtub  101 , the water pressure is applied to a certain shielding state maintaining unit such as the bellows  11  installed in the housing  10  via the water pressure transfer path  113  connected with the tank  100 . 
     At this time, the transfer of the water pressure is blocked by the shielding member  12  which shields the upper portion of the bellows  11 . In this state, the bellows  11  is elongated in proportion to the water pressure. 
     When the bellows  11  is elongated, namely, the bellows  11  is upwardly moved, the magnetic medium such as a cylindrical core  13  hooked to the shielding member  12  and the first support member  201  are vertically moved in the interior of the coil  14 . At this time, the first sliding member  202  which is formed of a magnetic material is not vertically moved in the leftward and rightward directions along the inclination surface  201   a  of the first support member  201  but vertically moved in a state that the same is positioned at the rightward portion of the first support member  201  as shown in FIG.  8 . Here, the inductance variation of the coil  14  based on the vertical movement of the first support member  201  is neglected. Namely, the inductance of the coil  14  is varied based on the vertical moving distance of the core  13 . As the core  13  is moved in the upward direction in the interior of the coil  14 , the inductance value of the coil  14  is increased. 
     The inductance variation value of the coil  14  is multiplied by the capacitances C of the condensers C 1  and C 2  of the waveform shaping unit  116  as shown in FIG.  6  and is generated as a certain resonant frequency. The thusly varied resonant frequency is amplified to a certain level by an amplification device  116   a  of the waveform shaping unit  116  and is provided to the microprocessor  114 . 
     Since both terminals a and b of the coil  14  are parallely connected between the condensers C 1  and C 2  of the waveform shaping unit  116 , the waveform shaping unit  116  operates as a LC resonant circuit by the coil  14  and the condensers C 1  and C 2  for thereby generating a resonant frequency. 
     The microprocessor  114  compares the variation value of the resonant frequency inputted from the LC resonant circuit with a water level variation for thereby judging the water level of the washing tub  101 . If the judged water level is the optimum water level corresponding to the sensed amount of the laundry, the water supply valve  109  is closed by the valve driving unit  117 , and the washing process is performed. 
     When the washing process is completed, the dehydration valve  110  is opened by the valve driving unit  117  for thereby discharging a polluted water from the washtub  101 . 
     In the water draining mode, as the water level is decreased in the washtub  101 , the water pressure is decreased. When the water pressure is gradually decreased, the bellows  11  is retracted by an elastic force of the coil shape spring  15  engaged between the magnetic medium such as the cap  17  and the core  13 , and the core  13  and the first support member  201  are vertically and downwardly moved in the interior of the coil  14 . 
     When the core  13  and the first support member  201  are returned to their original positions, the inductance of the coil  14  is decreased. The resonant frequency based on the decreased inductance and the capacitances of the condensers C 1  and C 2  are changed to the initial values and are inputted into the microprocessor  114  for thereby judging the completion time of the water draining process. 
     When the washing process is completed, the rinsing process is performed after the water supply and draining processes are performed based on the water level sensing method. 
     After the washing and rinsing processes are performed, the microprocessor  114  operates the inductance motor  103  at a high speed for thereby performing a dehydration process. 
     In the dehydration process, since the water level of the washtub  101  is a zero level, the water pressure applied to the water level sensor becomes the resonant frequency at the time when the water level is zero. 
     In addition, in the dehydration process, when the laundry is uniformly arranged in the washtub  101 , the washtub  101  is uniformly rotated with respect to the co-axis, so that an optimized operation is implemented without vibration of the tank  100 . 
     When the tank  100  is in the balanced state without vibration, as shown in FIG. 8, the first sliding member  202  such as a ball formed of a magnetic material is not moved in the leftward and rightward directions along the inclination surface  201   a  of the first support member  201 . Namely, the same is positioned at the rightward portion of the inclination surface  201   a.    
     When the first sliding member  202  which is formed of a magnetic material is positioned at the rightward portion of the first support member  201 , the inductance of the coil  14  is not varied. Therefore, the same resonant frequency is generated from the LC resonant circuit and is provided to the microprocessor. 
     The microprocessor  114  recognizes the balanced state of the tank  100  using a voltage wave form with respect to the continuously inputted same resonant frequency and accelerates the inductance motor  103  using the motor driving unit  115  during a certain dehydration time for thereby dehydrating the laundry in the washtub  101 . 
     If the laundry is inclined at a certain wall of the washtub  101 , the washtub  101  is eccentrically rotated, and the tank  100  is unbalanced based on the eccentric rotation, so that the tank  100  is vibrated in the every direction. 
     When the tank  100  is vibrated, as the first sliding member  202  formed of a magnetic material having a diameter of 3 mm through 5 mm is moved, the upper surface of the first support member  201  is moved in the leftward and rightward directions along the inclination surface  201   a  at an angle range of 0° through 40°, namely, in the ±X directions and the vertical ±Z direction. 
     For example, as shown in FIG. 8, if a certain force (vibration) is applied in the leftward direction, the first sliding member  202  is moved in the −X direction along the inclination surface  201   a  of the first support member  201  by a reaction operation and is moved in the +Z direction. Namely, the first sliding member  202  is moved in the vertical direction (+Z) direction in accordance with the inclination angle of the first support member  201 . Here, the diameter of the first sliding member  202  is about 4 mm, and the inclination angle of the first support member  201  is 20°. The height D from the lower surface of the first support member  201  to an initial position of the inclination angle is about 0 mm. 
     Continuously, when the first sliding member  202  is moved in the horizontal and vertical directions along the inclination surface  201   a  of the first support member  201  in accordance with the vibration of the tank  100 , the inductance of the coil  14  is changed. 
     When the tank  100  is greatly vibrated, the first sliding member  202  is greatly moved in the vertical direction along the inclination surface  201   a , and then is fallen by the gravity. Therefore, the inductance of the coil  14  is greatly changed. As a result, the resonant frequency of the LC resonant circuit is changed and is inputted into the microprocessor  114 . 
     Therefore, the microprocessor  114  detects the vibration of the tank caused by the eccentric rotation of the washtub  101  using the water level and vibration sensor  200 , and the rinsing and dehydration processes are performed in the above-described manner. 
     In the washing process, assuming that the inductance variation of the coil  14  due to the water level variation of the washtub  101  is Δ 1 , and the inductance variation of the coil  14  due to the vibration of the washtub  101  is ΔL 2 , the variation level of the inductance is ΔL 1  &gt;ΔL 2 . 
     In the washing process, since the vertical direction movement distance that the core  13  is moved in the coil  14  by the pressure of the water supplied based on the amount of the laundry in the washtub  101  is great, the inductance of the coil  14  is greatly changed. In the dehydration process, the vibration is most greatly generated. The first sliding member  202  is moved as long as the length of the inclination surface  201   a  of the first support member  201 . The variation of the inductance of the coil  14  is smaller than the movement of the core  13 . 
     FIGS. 9,  10  and  13  illustrate the second embodiment of the present invention. 
     The water level and vibration sensor  300  according to the second embodiment of the present invention includes a cylindrical housing  10  vertically installed at an outer wall of the upper portion of the casing  102  and connected via the tank  100  and the water pressure transfer path  113 , a bellows  11  installed in the housing and connected with the water pressure transfer  113  and implementing a retraction and elongation movement by the water pressure based on the water level in the washtub  101 , a shielding member  12  having a hook shape and shielding the transfer of the water pressure at the upper portion of the bellows, a coil unit  303  for installed at an inner center portion of the housing  10  and having more than at least three inductances, a cylindrical core  13  which is hooked at the upper portion of the shielding member  12  and is vertically moved in the inner space of the coil unit  303  in accordance with a retracting and elongating operation of the bellows  11  and varies an inductance of the coil unit  303 , a cylindrical support member  16  engaged to the upper portion of the coil unit  303  and supporting the coil unit, a cap  17  for covering the upper open portion of the support member, a spring  15  vertically engaged on the upper surface of the core  13  and the lower surface of the cap  17  and being formed in a spring shape for returning the core  13  to its original position, a second support member  301  installed in the inner space of the coil unit  303  spaced apart from the upper portion of the core  13  and vertically moving together with the core  13  based on the retracting and elongating operation of the bellows  11  and having its inclination surfaces  301   a  and  301   b , a second sliding member  302  having a diameter of amount 3 mm through 5 mm and vertically moving along the inclination surfaces  301   a  and  301   b  at the center portion of the upper surface of the second support member  301  by the eccentric rotation of the washtub  101  and varying an inductance of the coil unit  303  and being formed of a magnetic material, and a waveform shaping unit  304  for providing a fixed capacitance to the inductance of the coil unit  303  based on the vertical movement of the core  13  and the movement of the second sliding member  302 , generating a resonant frequency, and stabilizing and outputting the resonant frequency to a voltage waveform. 
     FIG. 14 illustrates the construction of the coil unit  303  according to the second embodiment of the present invention. 
     The coil unit  303  is formed in a cubic shape and includes coils  303   a  through  303   c  which are wound in the X, Y and Z directions. 
     Namely, The coils  303   a  and  303   b  are wound in the X and Y direction, and the coil  303   c  is wound in the Z direction into or onto the coils  303   a  and  303   b.    
     The Z-direction coil  303   c  is directed to detecting the vertical movement of the core  13  based on the water level, and the X and Y direction coils  303   a  and  303   b  are directed to detecting the current position of the second sliding member  302  based on the two-dimensional manner. 
     As shown in FIG. 15, the waveform shaping unit  304  according to the second embodiment of the present invention includes an amplification device  304   a  for amplifying an input voltage and providing the amplified voltage to the microprocessor  114  and condensers C 1  and C 2  connected in series with resistors R 1  and R 2  at the input and output terminals of the amplification device and feeding back the output voltage of the amplification device as an input voltage. The terminals (a,b), (c,d) and (e,f) of the coil unit  303  are parallely connected with the condensers C 1  and C 2 , so that when the core  13  and the second sliding member  302  are moved in the vertical and horizontal directions in the inner space of the coil unit  303  and along the upper surface of the second support member  301 , the waveform shaping unit  304  operates as a LC resonant circuit. 
     The operation of the water level and vibration detection apparatus for a washing machine according to the second embodiment of the present invention will be explained with reference to the accompanying drawings. 
     When a water is supplied into the washtub  101 , the water pressure of the thusly supplied water is applied to the bellows  11  in the housing  200  of the water level and vibration sensor  300  via the water pressure transfer path  113  connected with the tank  100 . 
     When the water pressure is increased, the pressure of the bellows is increased. When the bellows  11  is upwardly moved, the second sliding member  302  which is formed of a magnetic material and is positioned at the center position of the support member is vertically and upwardly moved in the inner space of the coil unit  303  onto which the coils  303   a  through  303   c  are wound in the X, Y and Z directions. 
     The inductance of the X direction coil  303   c  is varied at the coil unit  303  based on the vertical movement distance of the second support member  301  and the second sliding member  302 . The inductance of the X and Y direction coil  303   a  and  303   b  are not varied. 
     As shown in FIG. 14, since the X and Y direction coils  303   a  and  303   b  are installed in the vertical direction, even when the core  13 , the second support member  301  and the second sliding member  302  are moved in the vertical direction, the X and Y direction coils  303   a  and  303   b  do not receive any effects. Therefore, the inductance of the coils  303   a  and  303   b  do not vary. 
     However, since the Z direction coil  303   c  is installed in the horizontal direction, and the core  13 , the second support member  301  and the second sliding member  302  are moved in the vertical direction in the inner space of the horizontally installed Z direction coil  303   c , only the inductance of the Z direction coil  303   c  is varied. 
     As the core  13 , the second support member  301  and the second sliding member  302  are upwardly moved in the inner space of the Z direction coil  303   c , the inductance of the Z direction coil  303   c  is increased. 
     The inductance variation value of the Z direction coil  303   c  is multiplied by the capacitance C of the condensers C 1  and C 2  of the waveform shaping unit  304  as shown in FIG.  15  and is changed to a certain resonant frequency. The thusly obtained resonant frequency is fully amplified to its limit level by the amplification device  304   a  of the waveform shaping unit  304  and is supplied to the microprocessor  114 . 
     Namely, both terminals a and b of the Z direction coil  303   c  are parallely connected between the condensers C 1  and C 2  of the waveform shaping unit  304 , the waveform shaping unit  304  operates as a LC resonant circuit by the Z direction coil  303   c  and the condensers C 1  and C 2  for thereby generating a resonant frequency. Therefore, it is possible to measure the water level during the washing and rinsing processes using the thusly changed resonant frequency in the same manner as the first embodiment. 
     After the washing and rinsing processes are performed, the microprocessor  114  operates the inductance motor  103  at a high speed for thereby implementing a dehydration process. 
     At this time, if the laundry is uniformly provided in the walls of the washtub  101 , the washtub  101  is uniformly rotated based on the same radius, so that any vibration of the tank  100  does not occur for thereby implementing a balanced rotation. 
     If the tank  100  is not vibrated in the balanced state, as shown in FIG. 10, the second sliding member  302  does not move in the leftward and rightward directions along the inclination surfaces  301   a  and  301   b  of the second support member  301 , namely, in the −X and +X directions, and is positioned in the non-vibration area. 
     Since the second sliding member  302  is positioned in the non-vibration area of the second support member  301 , and the core  13  is not vertically moved by the zero water level of the washtub during the dehydration process, the inductance of the X direction coil  303   a  is not varied. 
     If the second sliding member  302  is continuously positioned in the non-vibration area of the second support member  301  based on the balanced position of the laundry, the same resonant frequency is continuously generated from the LC resonant circuit. 
     The microprocessor  114  recognizes the balance state of the tank  100  based on the voltage wave form with respect to the same resonant frequency and accelerates the inductance motor  103  using the motor driving unit  115  during a set dehydration time for thereby implementing a dehydration process in the washtub  101 . 
     However, if the laundry is non-uniformly provided at the wall of the washtub  101 , the washtub  101  is eccentrically rotated, and the tank  100  is vibrated based on the degree of the eccentric rotation and is leaned in the direction of the eccentrically positioned laundry. 
     When the tank  100  is vibrated, the second sliding member  302  having a diameter of 3 mm through 5 mm slides along the inclination surfaces  301   a  and  301   b  from the upper surface of the second support member  301  at an angle range of zero trough 40° based on the degree of the vibration. Namely, the second sliding member  302  slides in the direction of the vibration area (±X directions). 
     As shown in FIG. 10, when a certain force (vibration) is applied from the right portion, the second sliding member  302  is moved in the rightward direction (±X) via the inclination surface  301   b  from the center portion (non-vibration area) of the second support member  301 , namely, in the vertical direction (±Z) in the vibration area. On the contrary, if a certain force (vibration) is applied from the left portion, the second sliding member  302  is moved in the left direction (−X) via the inclination surface  301   a  from the center portion of the second support member  301 , namely, in the vertical direction (±Z) in the vibration area. 
     As shown in FIG. 14, in a state that the X direction coil  303   a  is installed in the vertical direction, and the Z direction coil  303   c  is horizontally installed, the second sliding member  302  is moved in the horizontal and vertical directions (in the vibration area) along the inclination surfaces  301   a  and  301   b  of the second support member  301 . As a result, the inductance of the X direction coil  303   a  and the Z direction coil  303   c  is changed. 
     In the second embodiment of the present invention, the diameter of the second sliding member  302  is about 4 mm, and the inclination angle of the inclination surfaces  301  and  301   b  is about 20°. 
     The variation value of the inductance of the X direction coil  303   a  and the Z direction coil  303   c  is changed to a resonant frequency based on the condensers C 1  and C 2  as shown in FIG.  15 . Therefore, it is possible to obtain a X direction vibration by a certain function with respect to the X and Z direction inductance variations by the microprocessor  114  based on the thusly obtained variation value. 
     Assuming that the vibration in the X and Z directions are V X  and V Z , the X direction vibration V X =f 1  (L X , L Z ) where f 1  is a certain function. 
     If the X direction vibration occurs, the laundry soaking and dehydration processes are continuously performed. 
     In the second embodiment of the present invention, since the second support member  301  is formed on the inclination surfaces  301   a  and  301   b  (vibration area) at a certain angle in the ±X directions at the upper surface center portion (non-vibration area), the X direction coil  303   a  of the coil unit  303  is not used. Namely, a horizontally arranged cylindrical coil  14  as shown in FIG. 3 is additionally used for thereby computing the  direction vibrations. 
     As shown in FIG. 3, when adapting the coil  14 , the second sliding member  302  is moved in the vertical direction with respect to the horizontally installed coil based on the inclination angle of the inclination surfaces  301   a  and  301   b  of the second support member  301 . 
     FIGS. 11 through 13 illustrate the third embodiment of the present invention. 
     FIG. 11 is a vertical cross-sectional view illustrating a water level and vibration sensing apparatus according to a second embodiment of the present invention, and FIG. 12 is a perspective view illustrating the third support member of FIG. 11, and FIG. 13 is a cross-sectional view taken along the line I—I of FIG.  12 . 
     The third support member  401  of the water level and vibration sensor  400  according to the third embodiment of the present invention includes a three dimensional spherical shape rounded surface having its upper surface which is radially rounded from its center portion for thereby implementing a radial direction free movement of the third sliding member  402  and is directed to detecting the vibrations in the forward and backward directions and the upward and downward directions. 
     In this case, the Z direction coil unit  303  is capable of detecting the movement of the core  13  based on the water level of the washtub during the washing process and is capable of measuring the water level and the upward and downward direction vibrations of the third sliding member  402 . 
     In view of the ±Z direction movements, there are two types of the movements. Namely, the third sliding member  402  formed of a magnetic material is moved in the upward and downward directions at the third support member  401 , and the third sliding member  402  is moved based on an inclination angle at the rounded surface  401   a  of the third support member  401 . 
     Continuously, the X and Y direction coils  303   a  and  303   b  are capable of measuring the current position of the third sliding member  402  which is moved in the forward and backward directions at the rounded surface  401   a  of the third sliding surface  401  in two dimension. 
     Therefore, it is possible to measure the X, Y and Z direction vibrations by measuring the X and Y direction vibrations in the above-described manner. 
     At this time, assuming that the inductances of the X, Y and Z direction coils  303   a  through  303   c  measured in the X, Y and Z directions are L X , L Y , L Z , the expression of V X =f 1  (L X , L Z ), V Y =f 2  (L Y , L Z ), and V Z =f 3  (V Z ). Here, f 1  through f 3  are certain function. 
     FIG. 16 illustrates the fourth embodiment of the present invention. 
     In the fourth embodiment of the present invention, the vibrations in the washing machine are detected using only the water level sensor  111  without the support members  201 ,  301  and  401  and the sliding members  202 ,  302  and  402 . 
     FIG. 16 illustrates the water level and vibration detection method according to the fourth embodiment of the present invention based on FIGS. 2,  3  and  6 . FIG. 16A is a resonant frequence wave form measured based on the water level sensor at the time when the dehydration process is performed in the non-eccentric process, and FIG. 16B is a resonant frequence wave form measured based on the water level sensor at the time when the dehydration process is started in the eccentric process. As shown in FIG. 16A, in the case that there is not eccentricity in the laundry or in the case of the non-load dehydration process, the induction motor  103  is driven in the zero water level state, and even when the speed of the induction motor  104  is increased based on the time lapse, the washtub  101  is not eccentrically rotated. Therefore, the resonant frequency of the water level sensor  111  is not changed. 
     However, as shown in FIG. 16B, in the case that there is a great eccentricity at the laundry, as the speed of the induction motor  103  is increased, the eccentric rotation of the washtub  101  is increased. The thusly increased eccentric rotation operates as an impact force which is applied to the outer casing  102 , and the thusly applied impact force is detected by the water level sensor  111 . The core  13  of the water level sensor  111  is moved in the interior of the coil  14  in the vertical direction based on the impact degree of the outer casing  102 , so that the inductance of the coil  14  is changed. The thusly changed inductance is changed to a resonant frequency by the LC resonant circuit, so that it is possible to measure the vibration by measuring the thusly changed resonant frequency. Namely, as shown in FIG. 16B, in the case that there is a great eccentricity at the laundry, the variation ΔHz of the resonant frequency of the water level sensor  111  is increased. Therefore, it is possible to check the current dehydration vibration state by detecting the variation ΔHz of the resonant frequency. 
     In more detail, the changed water pressure based on the water level of the washtub  101  is changed to the resonant frequency variation. In the case that the water level of the washtub  101  is a zero level checked by the water level sensor  111 , and there is not water to be dehydrated, the resonant frequency H 1  is measured and is set in the microprocessor  114  as a reference resonant frequency. 
     Thereafter, it is confirmed whether the current washing operation is a dehydration process. If the current mode is the dehydration mode, the resonant frequency H 2  is measured in the case that the water level is a zero level measured by the water level sensor  111 , and there is water to be dehydrated for thereby obtaining deviations H 2 -H 1  based on the reference resonant frequency H 1 . The thusly obtained deviation is compared with the reference variation ΔH. If the deviation is smaller than the reference variation ΔH, the induction motor  103  is rotated at a high speed for thereby implementing a normal dehydration. However, if the thusly obtained deviation is larger than the reference variation ΔH, the driving operation of the induction motor  103  is stopped, and the dehydration process is temporarily stopped, so that the over vibration of the washtub  101  is prevented. 
     The reference variation ΔH is a value which is previously set with respect to the values which are obtained based on a characteristic such as a type, capacitance, standard, etc. of the washing machine. In the dehydration process of the fourth embodiment of the present invention, the case that the vibrations are detected was explained. In another embodiment of the present invention, in the case that the induction motor  103  is in the turned on mode, it is possible to detect an over vibration during the entire washing processes by measuring the frequency variation using the water level sensor  111 . 
     In the present invention, it is possible to detect the vibrations of the washing machine based on the water level of the washtub and the rotation of the washtub using the water level and vibration sensor in the washing and dehydration modes compared to the conventional art in which the water level of the washtub is detected using the water level sensor and LC resonant circuit in the washing process, and the vibration of the washing machine is detected using a mechanical vibration sensor such as a limit switch in the dehydration mode. 
     As a result, in the present invention, it is possible to accurately measure the vibration of the washing machine based on the water level of the washtub and the eccentric rotation of the washtub, so that the error of the vibration detection and the time for dehydration are decreased. In addition, the number of the mechanical elements is decreased. 
     As described above, in the present invention, the vibration of the washing machine due to the eccentricity of the laundary and the water level are more accurately measured for thereby preventing the energy increase due to the vibration detection error and the increased dehydration time in the conventional art. 
     In the present invention, the water level and vibrations are accurately detected based on a quick operational response of the sliding member and coils in accordance with the eccentric degree of the laundry, so that it is possible to implement a better washing and dehydration process compared to the conventional washing machine. In addition, the reliability of the product is enhanced by implementing a performance stabilization of the product. 
     In the water level and vibration detection apparatus for a washing machine according to the present invention, the water level of the washtub and the vibration of the washing machine are accurately detected by a unitary sensor or a water level sensor, so that the mechanical vibration detection limit switch is not used for thereby implementing a cost reduction and preventing a complicate structure. 
     In addition, in the present invention, it is possible to implement a three dimensional vibration measurement. If the vibration width of the washing machine is large, it is possible to implement a simple control for stopping the washing and dehydration processes, and an active operation which is directed to detecting the vibration state during the washing and dehydration processes. 
     Although the preferred embodiment of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as recited in the accompanying claims.

Technology Classification (CPC): 3