Patent Publication Number: US-7712337-B2

Title: Measuring device comprising an optical sensory array, and method using said measuring device

Description:
FIELD OF THE INVENTION 
   The invention relates to a measuring device comprising an optical sensory array for determining positional changes of a drum which is mounted in a washing machine such that it can be pivoted at least about a rotational axis, and to a method for measuring by way of the measuring device. 
   BACKGROUND OF THE INVENTION 
   The centroid or the centroid axis of a washing machine drum is displaced from the rotational axis (out of the rotational center in an ideal initial position) by nonuniform distribution of the laundry and is therefore spaced apart from the rotational axis. The rotation of the centroid with the spacing from the rotational center causes centrifugal forces on the drum which have to be supported by the bearing arrangement on the washing machine. The greater the centroid axis deviates from the initial position, the greater what is known as the unbalance. This unbalance leads to undesired movements of the washing drum which is usually suspended elastically. The drum can swing out so far from the ideal rotational axis that contact occurs between the washing machine and the drum. Moreover, the rotational axis of the drum cannot coincide with the main axis of inertia of the drum as a result of the nonuniform distribution of the laundry in the drum, that is to say the rotational axis is tilted at the centroid. Dynamic unbalances of this type cause bending moments on the bearing journals during operation of the washing machine, by way of which bearing journals the drum is mounted rotatably in the washing machine, and result in undesired oscillations or in unnecessary bearing stresses. 
   The high bearing forces and oscillations which result from the unbalances can lead to premature wear of the bearing arrangements. 
   The movement and flooding of the is not sufficient in an overfilled washing drum. The cleaning action is insufficient. On the other hand, a washing drum which is not filled sufficiently leads to unnecessary energy and water consumption. In modern washing machines, the filling ratio, that is to say the amount of dry laundry in relation to the drum volume, is a characteristic variable for calculating washing processes which are optimized in terms of consumption and results. The amount is determined in the washing machine by means of a device using the dry weight. Subsequently, the operating criteria are fixed automatically as a function of the filling ratio which is calculated therefrom. 
   Positional changes are therefore to be understood as all changes of the position of the centroid or the centroid axis of the drum, and therefore also at least of one bearing for the drum, with respect to the initial position of the rotational axis in the case of nonstressed and nonrotating drums. Unbalances as a result of nonuniform material distribution on the drum itself are therefore also considered. 
   DE 31 17 106 A1 describes a measuring device of the generic type, by way of which the oscillation amplitudes which result from harmful oscillations and therefore the positional change of the drum with respect to the rotational axis are measured. The optical sensory array of the measuring device is arranged between the drum and one tub of the washing machine and outputs a signal after a limiting value is exceeded of the closeness of the drum and the tub. The signal causes a change and regulation of the rotational speed of the drum, with the target of reducing the unbalances. The measuring device is not suitable for detecting positional changes of the drum by means of the weight of the drum or for continuous measuring operations. 
   SUMMARY OF THE INVENTION 
   It is the object of the invention to provide a measuring device, by way of which the positional changes as a result of the weight of the laundry and also the positional changes which result from unbalances of the drum can be detected using measuring technology. The device should be simple to manufacture and robust, and also be suitable in some circumstances for retrofitting existing washing machine models. 
   This object is achieved according to the subject matter of the characterizing part of claim  1  in that the sensory array has at least one light sensor, at least one variable light passage and at least one light source. The light sensor is directed onto parts of the light of the light source which emanate from the light source, are dependent on changes in the light passage and strike the light sensor. The oscillation amplitudes which result from harmful oscillations and therefore the positional change of the drum with respect to the rotational axis are measured by way of the measuring device. Depending on the measuring state, the signals which emanate from the sensor result in a constant measured value (constant proportion) for the static loading from weight and in a changing signal (sine or rectangular curve) for dynamic loadings from the unbalances. 
   The measuring device has at least one light source. All technical light sources are conceivable, such as light-emitting diodes, laser sources, infrared light sources, lamps, etc. The type of light, as a rule a bundle of rays, can be selected alternatively as a function of the selected light source. 
   At least one of the light passages is made in elastically yielding material between the rotational axis of the drum and the washing machine, it being possible for the material to be deformed elastically at least at the light passage as a result of the positional changes of the drum. The material, for example the material of a supporting ring for a bearing, is seated either between a journal of the drum and the inner ring of the bearing or preferably radially between the bearing for the drum and the housing of the washing machine. In the first case, the stresses from the drum are introduced first into the supporting ring and then relayed via the elastic material to the bearing. In the last-mentioned case, one refinement of the invention, the stresses are transmitted from the drum first to the bearing and then preferably to a supporting ring. In this case, the supporting ring is mounted, for example, on a bearing flange or on a bearing support which is fixed to the housing of the washing machine. 
   The measuring device has at least one or a plurality of light passages which is/are arranged sensibly in the vicinity of the bearing arrangement of the drum, on one or on both bearings of the drum. Thus, one refinement of the invention provides for the light passage to be arranged radially between the rotational axis and the preferably rotary bearing, optionally sliding or roller bearing for the drum on the washing machine side, the drum being mounted in the washing machine by way of the bearing such that it can be pivoted at least about the rotational axis. The outer ring of the bearing is surrounded by the supporting ring which is formed at least partially from the elastically yielding material and in which at least the light passages are formed. The supporting ring can be manufactured as desired from plastic or other suitable materials or from combinations of the former, and can be provided with the light passages. One of the light passages preferably follows the bearing in the direction of gravity, at least for the determination of the weight of the laundry. 
   The supporting ring optionally has at least one web which extends radially from the bearing, the web having at least one of the light passages. Here, at least the web is formed from the elastically yielding material. 
   The light passage is, for example, a gap, a slot or a hole, or a passage for light of another design. Part of the light of the light source is kept back at the edge of the light passage. The other part of the light passes through the passage and strikes the light sensor or a reflector in an unobstructed manner. The passage cross section of the light passage is variable by deformations of the elastically deformable material at the element edges of the light passage which delimit the light passage. It is also conceivable that the edges are displaced with respect to an initial position without being deformed and therefore change the light passage. The stresses of the bearing which were mentioned in the introduction as a result of the weight of the laundry and/or unbalances lead to these elastic deformations of the material, at least in that region, in which the light passage is formed. As a consequence of this, the edges which lie opposite one another and delimit the light passage come closer to each other or move further away from one another. The light passage/gap therefore acts as an aperture. The free opening of the aperture changes in an analogous manner to the magnitude of the stresses which are exerted on the bearing. The portion of light which strikes the light sensor is variable as a function of the element edges which are movable toward one another and away from one another. 
   Moreover, stresses are all of the action and reaction forces which act on the bearing and result from the mounting of a component which can be moved rotationally or linearly. 
   The sensor or sensors is/are depending on the light source all suitable technical transducers of light, such as light-sensitive resistors, photodiodes, phototransistors or the like. 
   In a further alternative refinement of the invention, the sensory array/measuring device at least comprising the light sensors and the light source/sources, connection elements and further electronic components is optionally preassembled as one structural unit, for example, on a mounting plate. The structural unit is plugged into the supporting ring during assembly of the measuring device. 
   The light source and at least one of the light sensors lie opposite one another in a manner which is separated from one another by the supporting ring, in such a way that at least one part of the light is directed onto the light sensor through the light passage. As an alternative to this, the light source and at least one of the light sensors lie opposite a reflector in such a way that at least part of the light can be reflected onto the light sensor by the reflector, either through the light passage again or directly. 
   The changing brightness of the light, ageing of the light source or of the light sensor, fluctuations in the current supply or the influence of the environment such as temperature and air humidity, etc., possibly influence and falsify the measured results. For this reason, the measuring device has, as a rule, a further comparative sensor in addition to the light sensor and/or is provided with a comparison light source in addition to the light source, with the result that a comparison of the actual and the setpoint values can be performed continuously. 
   The measuring device is secured against destruction as a result of overloading. In a case of this type, for example, the elastic regions with the light passages are connected in series or in parallel with rigid parts of the support. The rigid supports absorb the overloading in the sense of an overload safeguard. It is also conceivable that an overload safeguard of this type is provided by the size of the light passage, that is to say by the height of the gap itself. If a defined load is exceeded, the element edges which lie opposite one another at the gap then come into contact with one another, for example, with the result that the gap width of the light passage is equal to zero at least in regions. 
   The device is of simple and robust configuration and can be manufactured inexpensively. The sensor array comprising the light source and the sensor and all necessary further electrical and electronic components are either arranged separately from the supporting ring or are optionally integrated into the latter. 
   Special manufacturing preparation of the bearings for use with a device according to the invention is not necessary. The use of all desired radial or axial bearings, or combinations of these, is conceivable. The essential components of the measuring device can be integrated into an adapter ring/supporting ring. The dimensions of the supporting ring/adapter ring can be adapted without much expenditure to surrounding constructions which are already present. On account of the spatial distance of the light passage from the stressed bearing, the stresses of the bearing point can be measured without the influence of the elastic deformations at bearing rings on the measured values. In the event of corresponding proximity to the bearing and sufficient flexibility of the support in the region of the light passages, however, the influences of deformations of the bearing rings can also be detected by way of the measuring device. 
   The measuring device makes the detection of bearing loads possible in ranges from small to high loads. It is therefore possible to determine unbalances which are characterized by high forces as a rule, and to determine the relatively low dry weight of the laundry by way of one or more of the measuring devices in a washing machine. To this end, for example, sensors with sensitivities and therefore measuring ranges which differ from one another with respect to the light parts which are to be measured are used in a washing machine. 
   In one case, the sensor or sensors is/are adapted to ranges of low loads in order to determine the laundry weight. Here, signals, which are independent of time, rotational speeds and rotational direction about the rotational axis, of positional changes of the drum as a result of static stresses are evaluated. The measuring range is defined, for example, by overall weights of the laundry in the drum from 0 to 10 kg. At the same time, it is possible to evaluate positional changes from unbalances by signals which change in a time-dependent manner, the signals emanating from that light sensor, by way of which the weight of the laundry is also detected. In this case, on account of the magnitude differences of the active forces from weight with respect to the forces from unbalances, the presence of the unbalances and their position are determined, but, as a rule, not their absolute value (for example, at the level of the active centrifugal force). 
   In the other case, one or more of the sensors is/are calibrated to the parts of the light at the maximal permissible stresses. To this end, signals of the light sensor which change in a time-dependent manner are evaluated, which light sensor detects at least those parts of the light which pass through the light gap at the maximal permissible positional changes of the drum. The maximal permissible limits are defined, for example, by the maximum permissible loading from centrifugal forces on the drum, for example by a limit of 4000 N. 
   Furthermore, the measuring ranges of the measuring device are dependent on the design of the light passage and on the rigidity of the elastic material. If the light passage is of rigid design, the magnitude of the unbalances can be determined as an absolute value. If the light passage is of yielding soft design, it is suitable, in particular, for determining the weight of the laundry. In the last case, unbalances can also be detected by way of the same sensory array, but without measurement of the absolute magnitude of said unbalances. 

   
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will be explained in greater detail in the following text using  FIGS. 1 to 5   b.    
       FIG. 1  shows a schematic illustration of a longitudinal section along the rotational axis  5   a  of a washing machine  26 . 
       FIGS. 2   a  and  2   b  show, in simplified form, a measuring device  1  for detecting stresses of a bearing  5  for a washing machine, in a longitudinal section along the rotational axis  5   a  (axis of rotation  5   a ) of the bearing arrangement  5 . 
       FIG. 3  shows, in schematic form, a further exemplary embodiment of a measuring device  16  for detecting stresses of the bearing  17 . 
       FIGS. 4 to 5   b  show, in diagram form, sensor signals  36  to  39  from measurements with one exemplary embodiment of the invention. 
   

   The washing machine  26  has a drum  27 , a tub  28  and, in outlines, a housing  29 . The bearing arrangement of the drum  27  has at least one embodiment of a measuring device  1  with a bearing  5  or a measuring device  16  with a bearing  17 . The drum  27  is mounted pivotably and rotatably in the housing  29  and is driven by means of an electric motor  30  via a belt drive  31  or the like. Laundry  32  in the drum  27  is covered with water  33  in the tub  28 . 
     FIG. 2   a  shows the measuring device  1  before final assembly and  FIG. 2   b  shows it as a finally assembled module. In this case, the bearing  5  is a radial bearing, for example a roller or sliding bearing. The measuring device  1  has at least one light source  2 , at least one light sensor  3  and at least one light passage  4 . The light passage  4  is formed, in a manner which is spatially separated from the bearing arrangement  5 , in an at least partially elastically yielding support  6  which is coupled to the bearing arrangement  5  and is in the form of a supporting ring  6   a . The radial bearing is held in the supporting ring  6   a . The supporting ring  6   a  is a composite part with, for example, an outer ring of the bearing  5 . The outer ring (not shown in further detail) is encapsulated by injection molding with the plastic of the supporting ring  6   a  in order to manufacture the composite. It is also conceivable that the supporting ring is pressed onto the outer ring. 
   The light source  2  and the light sensor  3  are mounted on a common mounting plate  7 , together with further electronic components  8  and conductors or connection elements  9 , to form a unit  10 . The supporting ring  6   a  has a chamber  11  and a further chamber  12 . The chambers  11  and  12  are separated from one another by a radial web  13  of the supporting ring. The web is designed to be at least elastically yielding enough in the radial direction that the radial gap width S of the light passage  4  is variable as a function of the stresses on the bearing arrangement  5 . The light passage  4  is formed in the web  13 . During the assembly of the measuring device  1 , the unit  10  is plugged into the chamber  11  and fastened in the supporting ring  6   a . The chamber  11  is closed at the end by way of a cover  14  which can be provided with plated-through holes for connecting conductors or alternatively closes the chamber  11  in a watertight manner. 
   The light source  2  protrudes into the chamber  12  through the web  13 . A reflector  15  which is directed onto the light passage  4  lies axially opposite the web  13  in the chamber  12 . The chamber  12  is closed also at the end by way of a cover  14 , to which the reflector  15  can optionally be fastened or applied by coating. The light sensor  3  detects the part of the light of the light source  2  which is reflected by the reflector  15  onto the light passage  4  and passes through the light passage  4 . 
   The bearing  17  according to  FIG. 3  is surrounded by a stationary support  18  in the form of a supporting ring  18   a . A journal  22  of the drum  27  is mounted rotatably by way of the bearing  17 . The supporting ring  18   a  is manufactured, for example, from plastic. At least one light passage  19  which is assigned in each case at least one light source  20  and one light sensor  21  is formed in the supporting ring  18   a  in a manner which is separated spatially from the bearing  17 . 
   The stresses of the bearing  17  can be detected using the changes in the gap width S to S x  and vice versa of the light passage  19 . The gap width S is dependent on the stresses F and elastic shape changes which result therefrom on the supporting ring  18   a  in the region of the light passage. One part of the light  23  of the light source  20  which is directed onto the light passage  19  outside the support  18  passes through the light passage  19 . That part of the light  44  which is dependent on the size of the gap width S to S x  and therefore on the stresses, for example on the force F, is detected by a light sensor  21  on the side which lies opposite the light source  20 , is scanned by an evaluation unit  45  and is forwarded by conductors  24 . The sensor system is encapsulated by means of a housing  25  which is shown with a dashed line. 
   Characteristic values for the evaluation of the unbalance are, for example, the oscillations which the bearing is exposed to. The possible sensor signals  36  which result from the measurements by way of the devices  1  and  16  are represented as an amplitude  34  of the oscillation path in an evaluation unit, as shown in the example according to  FIG. 4 . The bearing center point is deflected away from the rotational axis  5   a  in opposite directions per revolution of the drum  27 . A bearing oscillation is produced with the amplitude  34  and with the frequency  35  (periodic duration). In this case, the deflection (amplitude) can be used for determining the positional change of the drum  27  or the deflection of the bearing center point from the standard position. The deflection therefore at the same time describes the travel of the centroid of the drum  27  over time. 
   In the example according to  FIG. 4 , the light passage is so rigid and the measuring range of the light sensor  3  and/or  21  is configured in such a way that the unbalance does not lead to the saturation of the sensor signal  36 . In this case, the level of the centrifugal force from the unbalance can therefore also be concluded from the deflection (amplitude).  FIG. 4  shows only the profile for an unbalance mass by way of the sensor signal  36 , in order to simplify the illustration. In practice, however, unbalances from a plurality of different masses are superimposed as a rule. 
   The diagram according to  FIGS. 5   a  and  5   b  shows the signals of a light sensor  3 ,  21 , the measuring range of which is adapted to determination of the laundry weight and therefore to ranges of low loads. The light passage is accordingly designed to be very soft and to already yield at low loads. The measuring range of the light sensor  3  or  21  is adapted accordingly. 
     FIG. 5   a  is an illustration of the signals from measuring results with respect to the weight of the laundry, with sensor signals  37  (constant proportions) which are independent of time, rotational speeds and rotational direction about the rotational axis from positional changes of the drum  27  in static stresses at a standstill of the drum  27 . The sensor signals  37  are superimposed by sensor signals  38  which are caused by disruptive influences on the measurements, but not by the oscillations from the unbalances which were described in the introduction. 
   At the same time, it is possible to evaluate positional changes from unbalances as a result of signals according to  FIG. 5   b  which change in a time-dependent manner, by way of the light sensor  3  or  21 , the signals of which are shown in  FIG. 5   a . In this case, on account of the different magnitudes of the acting forces from weight with respect to the forces from unbalances, only the pure presence of the unbalances and their position are detected, but not the absolute value of the magnitude of the active centrifugal force. The sensor signal  39  is an approximate square wave signal which moves to and fro with the rotational frequency  40  of the drum from the lower limit  41  of the measuring range  43  of the light sensor  3  and/or  21  to the upper limit  42  of this measuring range  43 . 
   LIST OF DESIGNATIONS 
   
       
         1  Measuring device 
         2  Light source 
         3  Light sensor 
         4  Light passage 
         5  Bearing 
         5   a  Rotational axis 
         6  Support 
         6   a  Supporting ring 
         7  Mounting plate 
         8  Component 
         9  Connection element 
         10  Unit 
         11  Chamber 
         12  Chamber 
         13  Web 
         14  Cover 
         15  Reflector 
         16  Measuring device 
         17  Bearing 
         18  Support 
         18   a  Supporting ring 
         19  Light passage 
         20  Light source 
         21  Light sensor 
         22  Journal 
         23  Light 
         24  Conductor 
         25  Housing 
         26  Washing machine 
         27  Drum 
         28  Tub 
         29  Housing 
         30  Electric motor 
         31  Belt drive 
         32  Laundry 
         33  Water 
         34  Amplitude 
         35  Frequency 
         36  Sensor signal 
         37  Sensor signal 
         38  Sensor signal 
         39  Sensor signal 
         40  Rotational frequency 
         41  Lower limit 
         42  Upper limit 
         43  Measuring range 
         44  Light 
         45  Evaluation unit