Patent Publication Number: US-8530842-B2

Title: Cooking hob device

Description:
BACKGROUND OF THE INVENTION     
     The invention is based on a hob device, as well as on a method for a hob. 
     A hob device with a monitoring unit which monitors a control panel and a cooking area in a hob, is known from DE 103 37 538 A1. This monitoring unit has an optical sensor unit which is constructed as an infrared camera. 
     BRIEF SUMMARY OF THE INVENTION  
     The object of the invention consists in particular in providing a generic device with improved characteristics with regard to production costs and compact design. 
     The invention is based on a hob device with a monitoring unit for monitoring at least one cooking area of a hob which has at least one sensor unit provided to record in the infrared region. 
     It is proposed that the sensor unit has a plurality of infrared sensors that are arranged in a sensor array. This enables a space-saving hob device to be provided at low production costs. In particular, in comparison with a conventional solution with an infrared camera, a compact and low-cost monitoring unit can be created for a hob by an arrangement of compact and economical infrared sensors in a sensor array. A particularly economical design of the monitoring unit can be achieved if the infrared sensors forming the sensor array have thermocouples. A thermocouple is understood to be in particular an element that produces an electrical potential based on a temperature difference. Compared to sensor elements of an infrared optical system, a sensor unit based on the use of thermocouples is more economical to produce and requires less space. In a particularly advantageous way, the infrared sensors can be constructed as thermopiles or thermocouple piles. 
     A “cooking area” is understood to be, in particular, an area of a hob that is provided for an arrangement of food to be cooked for a cooking process with the food to be cooked. This area preferably corresponds to a three-dimensional area that extends above a hotplate of the hob and is delimited from below by the surface of the hotplate. “Infrared range” is understood to be in particular a wavelength range that includes at least one portion in the range from 780 nm to 1 mm. In this connection each of the infrared sensors advantageously has at least one sensitivity range in a wavelength range that is matched to the temperatures which typically occur in a hob application. By “infrared sensor” is meant in particular a sensor with at least one sensitivity range in the infrared range. By a “sensor array” is meant in particular an arrangement of sensors that is arranged on a common support, for example a level support. Preferably, the support and the sensor array are located in a common sensor housing. Advantageously, immediately adjacent sensors of a sensor array are spaced at a constant distance from one another over the sensor array. “Provided” is understood to be, in particular, specially configured, constructed and/or programmed. 
     A particularly advantageous application of an arrangement of infrared sensors in a sensor array consists in acquiring an image of the monitored cooking area, it being possible for an image of the cooking area to be obtained by the proposed sensor array of infrared sensors, economically and by a simple construction. In this connection, in a preferred embodiment of the invention it is proposed that the hob device has an evaluation unit that is provided for image evaluation of data recorded by the sensor unit. “Image evaluation of data recorded by the sensor unit” means, in particular, data evaluation that is designed to generate an image of the cooking area recorded in the field of vision of the sensor unit. Due to image evaluation, geometrical data of an object in particular can be obtained from the data detected and displayed by means of the data of the sensor unit. In particular, information about the dimensions and/or the contour of objects, which can be displayed by means of the data, can be determined by means of the data from the sensor unit. For this, the evaluation unit is provided in particular with a program or with image processing software. 
     It is proposed in particular that in order to detect an application situation during operation of the hob, the evaluation unit and the sensor unit are provided to act in combination to record and evaluate a chronological sequence of images of the cooking area, thereby enabling a high density of data to be obtained. In this connection, an “image” means in particular a data set that is acquired by the sensor unit and is suitable for generating an image of the monitored cooking area. An evaluation of an image by the evaluation unit can correspond to an evaluation of the data set, without the image having to be displayed by means of a display device. 
     It is also proposed that the evaluation unit be provided to assign an application situation from a change of a contour determined in at least two different images, which enables particularly simple and rapid detection of an application situation. By “contour” in particular is meant an external boundary of an object which can be displayed by means of data from the sensor unit. The contour can be determined by means of the evaluation unit with the aid of the sensor unit data, such as in particular by means of a pre-programmed contour extraction algorithm. A “change” in the contour can mean in particular an enlargement or a reduction whilst retaining a specific geometrical shape and/or a change in the geometrical shape. In this connection, for rapid recognition of an application situation, geometric patterns can be pre-stored in a memory unit of the evaluation unit, it being possible for a determined contour to be compared with a pre-stored pattern. 
     Particularly precise monitoring of the cooking area can be achieved if the arrangement of infrared sensors in the sensor array effects a rasterization of the cooking area to be monitored and if at least eight grids, in particular at least sixteen grids, are assigned to one direction of extension of the cooking area to be monitored. The direction of extension can be in particular one length or one width of the cooking area. 
     The sensor array can be one-dimensional, for example, it being possible for it to correspond to an in-line arrangement of infrared sensors in which the infrared sensors follow each other in one direction. However, it is particularly advantageous if the sensor array is a two-dimensional one. As a result, a larger part of the cooking area, in particular the entire cooking area of the hob, can be detected by the sensor unit. A “two-dimensional array” is understood to be in particular an arrangement in which an unambiguous pair comprising a column number and a row number can be assigned to every element of the arrangement, it being possible for the column numbers and the row numbers to assume at least two values in each case. 
     In this connection, a regular rasterization of the monitored cooking area can be achieved if the sensor array is a square matrix arrangement. 
     It is proposed in a further embodiment of the invention that the sensor unit has a field of vision that extends into a location area for a user of the hob during operation of the hob, whereby advantageously the monitoring unit can check to see whether a continuous cooking process is being carried out under the supervision of the user of the hob. In particular, the field of vision is determined by an optical system upstream of the sensitivity range of the sensor unit and/or by the arrangement of the sensor unit relative to the cooking area. 
     In an advantageous embodiment of the invention, the monitoring unit is designed as a safety device for detecting a hazardous situation during operation of the hob. 
     In this connection, a high level of safety can be achieved if the monitoring unit has an evaluation unit which is provided to differentiate between normal heating of food to be cooked and an at least potentially unintentional application situation. Differentiation between “normal” heating and an at least potentially unintentional application situation takes place for example by means of a comparison of recorded data from the sensor unit and/or an evaluation result of the evaluation unit, with pre-stored data. For this, the evaluation unit advantageously has a memory unit in which criteria which characterize an application situation as a normal application situation, a potentially unintentional application situation or an unintentional application situation, are stored. For example, a criterion can correspond to a temperature value or the shape of a geometrical contour. An “unintentional” application situation means an application situation for which action to remove imminent danger must be taken without delay, in particular immediately. A “potentially unintentional” application situation is an application situation in which the intention of the user of the hob cannot be ruled out. In this case where such an application situation exists, the user of the hob is requested to confirm his intention to implement a cooking process with specific heating parameters. 
     In a particularly advantageous embodiment of the invention it is proposed that the evaluation unit be designed to detect the presence of food to be cooked that is outside a cooking vessel provided to heat it up. This can be achieved in a particularly simple manner by monitoring a contour obtained by means of data from the sensor unit. 
     Furthermore, it is proposed that the hob device has a control unit for controlling a heating operation in at least two cooking zones of the cooking area, which in cooperation with the evaluation unit is provided to alter the heating operation of at least one of the cooking zones according to the position of the unintentional heating in the monitored cooking area when unintentional heating is detected in the cooking area. Alternately, or additionally, the control unit can be designed to switch off all current heating operations of the hob when an unintentional application situation is detected in a cooking zone. 
     Furthermore, the invention is based on a method with a hob in which a cooking area of the hob is monitored by means of a monitoring unit. It is proposed that data from infrared sensors arranged in a sensor array are captured and are evaluated for detection of an application situation. As a result, economical and space-saving elements can be used for a monitoring process. 
     Particularly reliable detection of an application situation can also be achieved if the data are evaluated by means of image evaluation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       Further advantages are disclosed in the following description of the drawing. An exemplary embodiment of the invention is illustrated in the drawing. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will usefully also consider the features individually and in meaningful further combinations. 
         FIG. 1  shows a hob, a cooking vessel arranged in the cooking area of the hob, and internal units of the hob with a monitoring unit to monitor the cooking area, 
         FIG. 2  shows a side view of the hob with a field of vision of the monitoring unit which extends beyond a front area of the hob, 
         FIG. 3  shows a detailed view of a sensor unit of the monitoring unit, with an arrangement of infrared sensors, 
         FIG. 4  shows a plan view of a hotplate of the hob from above and a rasterization of the cooking area produced by the sensor arrangement of  FIG. 3 , 
         FIG. 5   a  shows a first application situation in which a liquid is being heated up in the cooking vessel, 
         FIG. 5   b  shows an image recorded by the sensor unit of the cooking area in the application situation of  FIG. 5   a,    
         FIG. 6   a  shows a second application situation in which the liquid has overflowed out of the cooking vessel, and 
         FIG. 6   b  shows an image recorded by the sensor unit of the cooking area in the application situation of  FIG. 6   a.    
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE  PRESENT INVENTION 
       FIG. 1  shows a hob  10  in a heavily schematized view. The hob  10  has a hotplate  12  which defines a cooking area  16  (also see  FIG. 4 ) forming an arrangement for a cooking vessel  14 . Here cooking area  16  means a three-dimensional area which is arranged above the hotplate  12  and is delimited below by the surface of the hotplate  12 . The hob  10  is mounted in a kitchen countertop, not shown. In an alternate embodiment the hob  10  can be constructed as a component part of an electric cooker. The cooking area  16  has a plurality of cooking zones  18  ( FIG. 4 ), each of which is assigned to a heating unit  20  arranged underneath the hotplate  12 . The heating units  20  can have a heating resistor or an induction unit. As an alternate to division of the hotplate  12  into cooking zones  18  separate from each other, a version of the hob  10  is conceivable in which a cooking process for the cooking vessel  14  can be realized irrespective of the position of the cooking vessel  14 , if for example a matrix arrangement of heating elements, in particular induction coils, forms a coherent cooking zone, which corresponds to the entire hotplate  12 . 
     The hob  10  has a hob device  22 , which includes a control unit  24  which is provided for control of a heating operation in the cooking zones  18 . For this, the control unit  24  acts in conjunction with the heating units  20 . The control unit  24  has at least one arithmetic logic unit (not shown), which is constructed for example as a processor. The hob device  22  also has a monitoring unit  26  which is provided to monitor the cooking area  16 . For this, the monitoring unit  26  includes a sensor unit  28  and an evaluation unit  30  which is provided for evaluation of data recorded by the sensor unit  28 . The sensor unit  28  shown in further detail in  FIG. 3  is arranged above the cooking area  16  and has a field of vision  31  which detects at least the cooking area  16  (see also  FIG. 2 ), and is illustrated schematically in  FIGS. 1 and 2  by means of dashed lines. In the embodiment shown, the sensor unit  28  is arranged above a rear area of the hob  10  and underneath an extractor hood  32 . As  FIG. 2  shows, the sensor unit  28  can be arranged, in particular, in a corner region formed by a wall  34  and the extractor hood  32 . An alternate arrangement of the sensor unit  28  in a position which facilitates the detection of the cooking area  16 , in particular the entire cooking area  16 , is conceivable. In particular, it is possible to arrange the sensor unit  28  in the extractor hood  32 . Data communication between the sensor unit  28  and the evaluation unit  30  can be effected by means of cabling, not shown, and/or a wireless connection. 
       FIG. 3  shows a detailed view of the sensor unit  28 , which has an arrangement of a plurality of infrared sensors  36  denoted as a sensor array  38 . The sensor array  38  is constructed as a two-dimensional array, it being possible for an unambiguous pair, comprising a line number and a column number, to be assigned to each infrared sensor  36 . In particular, the sensor array  38  corresponds to a matrix arrangement with a square matrix of sixteen by sixteen infrared sensors  36 . A further matrix arrangement with at least thirty two by thirty two infrared sensors  36  is conceivable. The sensor unit  28  is designed for detection in the infrared region. In particular, the infrared sensors  36  have thermocouples which form a thermopile or thermoelectric pile, for example. Further sensors which appear meaningful to the person skilled in the art for detection in the infrared region are conceivable. The sensor array  38  is arranged in a housing  40  of the sensor unit  28  (see  FIGS. 1 and 2 ), said housing being a TO-5 type case, for example. 
     As can be seen from  FIG. 4 , the sensor array  38  of  FIG. 3  produces rasterization of the cooking area  16 , it being possible for a grid  42  to be assigned to each infrared sensor  36  of the sensor array  38 . The cooking area  16  has two directions of extension  44 . 1 ,  44 . 2  perpendicular to one another, which are aligned parallel to the sides of the hotplate  12 . Because the sensor array  38  is constructed as a square matrix arrangement, sixteen grids  42  are assigned to each direction of extension  44 . As can be seen from  FIG. 4 , the field of vision  31  of the sensor array  38  extends into the location area  50  in front of the front area of the hob  10 . For the sensor array  38  with a matrix arrangement of sixteen by sixteen infrared sensors  36  for a hob of 60 cm, one grid  42  has an average length of approximately 4 cm, whereby small objects can be resolved in the cooking area  16 . 
     Imaging of the monitored cooking area  16  can be obtained by means of the sensor array  38  of infrared sensors  36  when the monitoring unit  26  is operating. In order to utilize this advantageous application of the sensor array  38 , the evaluation unit  30  is provided for image evaluation of data acquired by the sensor unit  28 . For this, the evaluation unit  30  has an arithmetic logic unit  46  constructed as a microprocessor, and a memory unit  48  in which at least one program is stored for at least one image evaluation of data from the sensor unit  28 . In particular, image processing software can be stored in the memory unit  48 . 
     The principle of operation of the monitoring unit  26  with the sensor unit  28  and the evaluation unit  30 , and their interaction with the control unit  24  is explained in detail with the aid of an example in  FIGS. 5   a ,  5   b ,  6   a  and  6   b.    
     It is assumed in accordance with the illustration in  FIG. 5   a  that an operator of the hob  10  places the cooking vessel  14  in one of the cooking zones  18 , that is to say in cooking zone  18 . 1 . A liquid, that is to say a specified quantity of milk, is to be heated up in the cooking vessel  14 . It is also assumed that after switching on the corresponding heating unit  20 , the operator leaves the room in which the hob  10  is located, so that the continuous heating operation of the hob  10  is left unsupervised. 
     The absence of an operator in a location area  50  in which the operator of the hob  10  is located under the usual operating conditions, can be established by means of the evaluation unit  30  in combination with the sensor unit  28  by recording images acquired by the sensor unit  28  and subsequent evaluation of these image data. For this, the field of vision  31  of the sensor unit  28  extends into the location area  50 , as can be seen in  FIG. 2 . In an alternate embodiment of the monitoring unit  26 , the sensor unit  28  can detect only the cooking area  16 , it being possible to provide a further sensor unit which is specially designed to monitor the location area  50 . This sensor unit can be arranged in particular in the front area of the extractor fan  32 . 
     If the operator is located in the location area  50  in front of the hob  10 , this is detected by the evaluation unit  30  in an image recording of the sensor unit  28  by means of the heat radiated by the human body. If, in the image captured by the sensor unit  28 , there is no area indicating the presence of the operator in the location area  50 , then the absence of the operator is detected by the evaluation unit  30 . After this application situation has been determined by the evaluation unit  30 , a monitoring mode of the monitoring unit  26  in which the current heating operation is continued under the supervision of the monitoring unit  26  is switched on. In this operating mode, a partial area of the cooking area  16  in particular is monitored and is recognized by the evaluation unit  30  as a hot area of the cooking area  16 . In the present example a hot area  52  is formed by the surface of the food to be cooked. Due to the shape of the cooking vessel  14  this hot area  52  has a regular form, which in the present case corresponds to a circular shape. If a cooking vessel with a lid is used for the cooking process, then a hot area corresponds to the surface of the lid.  FIG. 5   b  shows in schematic form an image  16 ′ of the monitored cooking area  16  recorded by the sensor unit  28 , and in which the hot area  52  can be seen in the form of an image  52 ′. Current images  16 ′ of the monitored cooking area  16  are recorded when the monitoring mode is implemented. As a result, due to the interaction of the sensor unit  28  and the evaluation unit  30 , a chronological sequence of images  16 ′ of the cooking area  16  is captured and evaluated. In this chronological sequence of images  16 ′, the contour of the hot area  52  in particular is monitored by the evaluation unit  30 , for example by means of contour extraction and analysis of the contour obtained. 
     The evaluation unit  30  is provided to assign a specific application situation, in particular a hazardous situation, to a change of contour obtained in the chronological sequence of images  16 ′. Consequently, said evaluation unit can distinguish between normal heating-up of food to be cooked, corresponding to the illustration in  FIG. 5   a , and an application situation that is not intended by the operator. In particular, by means of image analysis of the data acquired by the sensor unit  28 , a hazardous situation can be detected in which the food to be heated up is arranged outside of the cooking vessel  14  provided to heat it up, as in the application situation shown in  FIG. 6   a , for example. It is assumed from the illustration of  FIG. 6   a  that in the absence of the operator the heated milk comes out of the cooking vessel  14  and spreads itself around the cooking vessel  14  on the hob  12 . This is detected by the evaluation unit  30  in that the contour of the hot area  52  deviates from the regular, circular form of  FIG. 5   a . An image  16 ′ of the cooking area  16  recorded by the sensor unit  28  is shown in  FIG. 6   b . The evaluation unit  30  recognizes this as an unintentional application situation, in particular a hazardous situation and transmits a signal to an output unit  54  of the monitoring unit  26 , it being possible for an alarm signal to be output by the output unit  54 . The output unit  54  can be constructed as an audible and/or a visual output unit  54 . The monitoring unit  26  also includes a timer  56  which records the time elapsed since the onset of the unintentional application situation. If no operating procedure is actioned by the operator within a preset time interval, a signal is transmitted to the control unit  24 , which switches off the corresponding heating unit  20 . When the monitoring mode is enabled, the monitoring unit  26  has the function of a safety device for recognizing a hazardous situation and in this connection can, in particular, effect an emergency shutdown of at least one heating unit  20 . 
     In a further application situation, instead of a complete shutdown of the heating unit  20 , the heating power can be automatically reduced by the control unit  24 . The development of steam and smoke can also be detected by a contour analysis of an image of a heating area of the monitored cooking area  16 . For example, the development of vapor can be attributed to unintentional heating-up of oil, it being possible for an oil fire to be advantageously prevented through a shut-down process by means of the control unit  24 . 
     Further variants of the monitoring mode of the monitoring unit  26  described above are conceivable. The monitoring mode described above can, for example, be implemented in the presence of the operator in the location area  50 . This monitoring mode can be used advantageously as an aid for an inexperienced cook. In this connection, application situations detected by the evaluation unit  30  with the aid of images  16 ′ of the cooking area  16  can be classified into at least three categories. Here a distinction can be made between normal heating-up of food to be cooked, a potentially unintentional application situation and an unintentional application situation which corresponds in particular to a hazardous situation. If an application situation is classified as potentially unintentional in the presence of the operator, then the operator can be requested by means of the output unit  54  to implement a confirmation process by which he confirms that the current heating operation is intentional. If this confirmation is implemented, then the heating operation is continued unchanged by the control unit  24 . Means for classifying an application situation, in particular criteria which require specific conditions to be met, are stored in the memory unit  48  of the evaluation unit  30 , it being possible for the classification to be implemented, for example, by comparing characteristic values obtained from image data from the sensor unit  28 , with these pre-stored criteria. 
     The temperature characteristic at lids of a cooking vessel or at the surface of food to be cooked can also be monitored by image evaluation by means of the evaluation unit  30 . If the temperature exceeds a certain value, this can be recognized as a potentially unintentional application situation or as a hazardous situation, whereby overcooking can be rapidly detected and prevented at least to some extent. 
     REFERENCE NUMBERS 
     
         
           10  Hob 
           12  Hotplate 
           14  Cooking vessel 
           16  Cooking area 
           16 ′ Image 
           18  Cooking zone 
           20  Heating unit 
           22  Hob device 
           24  Control unit 
           26  Monitoring unit 
           28  Sensor unit 
           30  Evaluation unit 
           31  Field of vision 
           32  Extractor hood 
           34  Wall 
           36  Infrared sensor 
           38  Sensor array 
           40  Housing 
           42  Grid 
           44  Direction of extension 
           46  Arithmetic logic unit 
           48  Memory unit 
           50  Location area 
           52  Heating area 
           52 ′ Image 
           54  Output unit 
           56  Timer