Patent Publication Number: US-9848462-B2

Title: Temperature sensor and induction heating cooker having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of Korean Patent Application No. 2010-0072854, filed on Jul. 28, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments relate to an induction heating cooker having a temperature sensor to sense temperature of a working coil or an object to be heated. 
     2. Description of the Related Art 
     Generally, an induction heating cooker is an apparatus which supplies high-frequency current to a heating coil to generate a strong high-frequency magnetic field in the heating coil and to generate an eddy current in an object to be heated, magnetically coupled to the heating coil, using the high-frequency magnetic field such that the object is heated using Joule&#39;s heat generated by the eddy current, thereby cooking the object. 
     In the induction heating cooker, a position where an object to be heated is to be placed, is displayed on a top plate on which the object is placed, and a container is placed on the position such that the container is heated by a working coil below the top plate. 
     In recent years, the induction heating cooker has been provided with a function to sense the position where a container is placed although the container is not placed at a predetermined position. 
     In this case, a plurality of working coils are disposed throughout a cooking plate. A temperature sensor is provided with respect to the working coils so as to sense heat generated from the working coils. 
     SUMMARY 
     It is an aspect to provide an induction heating cooker including a temperature sensor to measure temperature of working coils. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention. 
     In accordance with one aspect, an induction heating cooker includes a cooking table on which an object to be heated is placed, a working coil and a temperature sensor disposed below the cooking table, and a heat transfer member to transfer heat from the working coil to the temperature sensor. 
     The heat transfer member may partially contact the working coil so as to transfer heat to the working coil. 
     The heat transfer member may be made of a nonmagnetic material exhibiting high thermal conductivity. 
     The heat transfer member may be made of copper, aluminum, or stainless steel. 
     The heat transfer member may include a heat pipe including a hermetically sealed pipe filled with a predetermined amount of an operating fluid phase of which is variable. 
     The temperature sensor may include a contact temperature sensor or a non-contact temperature sensor. 
     The working coil may include a plurality of working coils disposed in the form of a grid or a honeycomb. 
     The working coil may include a plurality of working coils disposed below the cooking table, the temperature sensor may be disposed between working coils, and the heat transfer member may extend from the temperature sensor to the working coils. 
     The heat transfer member may be disposed to transfer heat to each of the working coils adjacent to the temperature sensor. 
     The heat transfer member may be disposed to transfer heat to two or more of the working coils disposed around the temperature sensor. 
     The temperature sensor may have a sensing unit to cover a sensor element, and the heat transfer member may extend from one side of the sensing unit such that the heat transfer member is integrated with the sensing unit. 
     The sensing unit may include a plurality of sensing zones divided by heat insulation walls and sensor elements in the respective sensing zones, and the heat transfer member may extend from one side of each of the sensing zones. 
     In accordance with another aspect, a temperature sensor of an induction heating cooker including a cooking table on which an object to be heated is placed and a plurality of working coils disposed below the cooking table, disposed between the working coils to measure temperature of the object, includes a sensing unit to cover a sensor element and one or more heat transfer members extending from one side of the sensing unit. 
     The one or more heat transfer members may be made of a nonmagnetic material exhibiting high thermal conductivity. 
     The one or more heat transfer members may be disposed around the sensing unit radially. 
     Each of the one or more heat transfer members may include a heat pipe. 
     The temperature sensor may include a platinum resistance temperature sensor, a thermocouple, a thermistor, or an IC temperature sensor. 
     The sensing unit may include a plurality of sensing zones, divided by heat insulation walls, each including a sensor element provided therein, and each of the one or more heat transfer members may extend from one side of each of the sensing zones. 
     In accordance with another aspect, an induction heating cooker includes a main body, a cooking table disposed at a top of the main body such that an object to be heated is placed on the cooking table, a plurality of working coils disposed below the cooking table to heat the object, an inverter unit to supply high-frequency current to the working coils, a drive unit to turn a switching element of the inverter unit on/off, a controller to control the drive unit and other components of the induction heating cooker, a temperature sensor disposed between the working coils to measure temperature of the object, one or more heat transfer member disposed around the temperature sensor radially to transfer heat generated from the object heated by the working coils disposed adjacent to the temperature sensor to the temperature sensor. 
     The controller may detect an output signal based on the temperature measured by the temperature sensor and stop the operation of the inverter unit when the temperature of the object is abnormally increased. 
     The induction heating cooker may further include a signal cutoff unit to turn a signal transmitted from the controller to the drive unit on/off based on the output signal of the temperature sensor, and the signal cutoff unit may cut off the signal transmitted from the controller to the drive unit when the temperature of the object is equal to or greater than a predetermined temperature. 
     In accordance with a further aspect, an induction heating cooker includes a cooking table comprising one or more predetermined zones, at least one working coil and a temperature sensor disposed below each of the one or more predetermined zones, and a heat transfer member to transfer heat from the at least one working coil to the temperature sensor. 
     The at least one working coil may include a plurality of working coils below each of the one or more predetermined zones such that the working coils are adjacent to each other, and the heat transfer member may include a plurality of heat transfer members the number of which corresponds to the number of the working coils below each of the one or more predetermined zones, the heat transfer members extending from the temperature sensor to the respective working coils. 
     The one or more predetermined zones may include a plurality of predetermined zones disposed below the cooking table, the at least one working coil may include a plurality of working coils disposed below the cooking table, the temperature sensor may include a plurality of temperature sensors disposed below the cooking table, and the heat transfer member may include a plurality of heat transfer members disposed below the cooking table. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a perspective view schematically illustrating the structure of an induction heating cooker according to an embodiment; 
         FIG. 2  is an exploded perspective view of  FIG. 1 ; 
         FIGS. 3A to 3E  are views illustrating various arrangement structures of heat transfer members according to an embodiment; 
         FIG. 4  is a control block diagram of the induction heating cooker; and 
         FIG. 5  is a view illustrating a temperature sensor according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
       FIG. 1  is a perspective view schematically illustrating the structure of an induction heating cooker  1  according to an embodiment, and  FIG. 2  is an exploded perspective view of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the induction heating cooker  1  includes a main body  10  forming the external appearance of the induction heating cooker  1  and a cooking table  13  located at the top of the main body  10  such that an object  11  to be heated, for example, a cooking container, is placed on the cooking table  13 . 
     The main body  10  is formed in the shape of a box open at the top thereof. The cooking table  13  covers the open top of the main body  10 . 
     The cooking table  13  is formed in the shape of a flat board on which the object  11  is placed. The cooking table  13  may be made of tempered glass, for example, ceramic glass, such that the cooking table is not easily broken or scratched. 
     A plurality of working coils  20  to induction heat the object  11  placed on the cooking table  13  are mounted below the cooking table  13 . 
     The working coils  20  are uniformly disposed in the main body  10  such that the object  11  is heated over entire area of the cooking table  13 . 
     The working coils  20  may be disposed in the form of a grid including parallel lines intersecting at right angles at regular intervals. The number of the working coils  20  may be changed depending upon the size of the main body  10 . In this embodiment, the number of the working coils  20  is 16 to 20, for example. 
     Meanwhile, arrangement of the working coils  20  is not particularly restricted as long as the intervals of the working coils  20  are reduced such that cooking is performed at any position of the cooking table  13 . For example, the working coils  20  may be disposed in the form of a honeycomb. 
     In this structure, the cooking table  13  may not have specific cooking zones corresponding to the working coils  20 . 
     A controller  50  to control the operation of the induction heating cooker  1  is disposed at the main body  10  in front of the cooking table  13 . The controller  50  includes a manipulation switch  51  to allow a user to input a cooking command and a display  53  to display a state of the induction heating cooker  1 . 
     A plurality of temperature sensors  30  to sense temperature of the working coils  20  or the object  11 , are disposed between the working coils  20 . 
     When the temperature of the object  11  cooked on the cooking table  13  is abnormally increased, the temperature sensors  30  sense the abnormal temperature of the working coils  20  or the object  11  and transmits the sensed temperature to the controller  50  such that the controller  50  stops the operation of the induction heating cooker  1 . 
     Each of the temperature sensors  30  may be embodied as a thermistor element where the internal resistance value of which changes based on the change of ambient temperature. The thermistor may be a negative temperature coefficient (NTC) thermistor, a positive temperature coefficient (PTC) thermistor, or a critical temperature resistor (CTR) thermistor. 
     As shown in  FIG. 2 , each of the temperature sensors  30  includes a thermistor  31  including electrodes provided at opposite sides thereof, a plurality of lead wires  33 , one end of each of the lead wires  33  being connected to a corresponding one of the electrodes, and a sensing unit  35  surrounding the thermistor  31 , a portion of each of the lead wires  33  protecting the thermistor  31 . 
     In this embodiment, each of the temperature sensors  30  is embodied as a contact temperature sensor  30  using a thermistor element, to which, however, embodiments are not limited. For example, each of the temperature sensors  30  may be embodied as a thermocouple, a bimetal, an IC temperature sensor, or an infrared sensor, which is a non-contact sensor. 
     Generally, the number of the temperature sensors  30  is equal to the number of the working coils  20 . In this embodiment, however, the number of the temperature sensors  30  is less than the number of the working coils  20 . 
     To this end, each of the temperature sensors  30  includes a plurality of heat transfer members  40  to transfer heat to the corresponding working coils  20  adjacent to each of the temperature sensors  30 . One end of each of the heat transfer members  40  is connected to a corresponding one of the temperature sensors  30 . 
     That is, as shown in  FIG. 2 , each of the temperature sensors  30  includes a plurality of heat transfer members  40  radially extending from the sensing unit  35 . 
     The heat transfer members  40  may be integrated with the sensing unit  35 . Alternatively, the heat transfer members  40  may be manufactured separately and then coupled to the sensing unit  35 . 
     Each of the heat transfer members  40  may be embodied as a rod made of a nonmagnetic material, such as copper, aluminum, or stainless steel, exhibiting high thermal conductivity such that heat generated from the object  11  heated by a corresponding one of the working coils  20  is transferred to a corresponding one of the temperature sensors  30 . 
     When the heat transfer members  40  are made of the nonmagnetic material, a measurement error, resulting from heating of the heat transfer members  40  due to electromagnetic induction caused by a magnetic field generated from the working coils  20 , may be reduced. 
     Alternatively, each of the heat transfer members  40  may be embodied as a heat pipe (not shown) to rapidly transfer heat generated from the object  11  heated by a corresponding one of the working coils  20  to a corresponding one of the temperature sensors  30 . 
     The heat pipe may be a hermetically sealed pipe, made of copper or aluminum, filled with a predetermined amount of an operating fluid in a vacuum state, which may be varied. The operating fluid may be methanol, ethanol, acetone, ammonia, or freon exhibiting continuous phase change between gas and liquid, low boiling point, and excellent evaporation latent heat. 
     With the above structure, heat is rapidly transferred between opposite ends of the heat pipe, thereby further improving reliability in temperature measurement of the object  11 . 
     Meanwhile, the heat transfer members  40  connected between a corresponding one of the temperature sensors  30  and the working coils  20  may be disposed in various forms. 
       FIGS. 3A to 3E  are views illustrating various arrangement structures of heat transfer members according to an embodiment. 
     Referring to  FIGS. 3A to 3E , the temperature sensors  30  are disposed between the working coils  20  which are uniformly disposed in the form of a grid or a honeycomb, and each of the heat transfer members  40  extends from a corresponding one of the temperature sensors  30  is on top of each of the working coils  20  adjacent to the corresponding one of the temperature sensors  30  in various forms so as to measure temperature of the object  11  heated by the working coils  20 . 
       FIG. 3A  shows an arrangement in which each heat transfer member  40  is disposed to measure temperature of a working coil  20  adjacent to a temperature sensor  30 . A temperature measurement range of the temperature sensor  30  is increased by the heat transfer member  40 , thereby improving reliability in temperature measurement of the object  11  placed on a certain zone of the cooking table  13 . 
       FIG. 3B  shows an arrangement structure in which two heat transfer members  40  are disposed to measure temperature of two adjacent working coils  20  using a temperature sensor  30 . Two heat transfer members  40  may be directed to two working coils  20  disposed about a temperature sensor  30  in upward, downward, left and right directions. 
       FIGS. 3C and 3D  show an arrangement in which three heat transfer members  40  are disposed to measure temperature of three or four adjacent working coils  20  using a temperature sensor  30 . Three or four heat transfer members  40  may be disposed at arbitrary angles such that the each of heat transfer members  40  does not share the same working coil  20 . Alternatively, at least one of the three or four heat transfer members  40  may be disposed above at least two working coils  20  so as to transfer heat from the at least two working coils to the temperature sensor  30 . 
     That is, each of the heat transfer members  40  may be disposed to transfer heat from a working coil to a temperature sensor  30 , or heat from two or more working coils  20  to a temperature sensor  30 . 
     Also, the number of the temperature sensors  30  and the arrangement of the heat transfer members  40  may be changed based on the number of the working coils  20  disposed below the cooking table  13 . 
     For example, the heat transfer members  40  shown in  FIGS. 3A to 3D  may be disposed in various forms depending upon the number and size of the working coils  20  randomly disposed below the cooking table  13 . 
     That is, as shown in  FIG. 3E , the plurality of working coils  20  may be randomly disposed below the cooking table  13  depending upon the size and arrangement of the working coils  20  densely disposed adjacent to each other. 
     In this structure, the temperature sensors  30  are disposed below predetermined zones  13   a ,  13   b ,  13   c , and  13   d  which are divided based on the number of the working coils  20 . The heat transfer members  40  connected to the temperature sensors  30  disposed in the respective zones  13   a ,  13   b ,  13   c , and  13   d  may be disposed in the arrangement structures of  FIGS. 3A to 3D  depending upon the number of the working coils  20  disposed in the respective zones  13   a ,  13   b ,  13   c , and  13   d.    
     The zones  13   a ,  13   b ,  13   c , and  13   d  are zones arbitrarily divided depending upon the number, for example, 2 to 4 of the working coils  20 . 
     Meanwhile, the arrangement structures of the heat transfer members  40  are not limited to the above examples. The heat transfer members  40  may be disposed in different forms depending upon the arrangement structures of the working coils  20  and the temperature sensors  30 . 
     Also, when each of the temperature sensors  30  is embodied as a non-contact sensor, e.g., an infrared sensor, each of the temperature sensors  30  may be provided at the top thereof with a sensing unit  35  to which at least one end of each of the heat transfer members  40  is radially disposed such that the sensing unit  35  measures heat transferred through the heat transfer members  40 . In this case, the infrared sensor measures the amount of infrared light emitted from the sensing unit  35  and temperature of the sensing unit  35  to detect abnormal increase in temperature of the working coils  20 . 
     Hereinafter, the operation of the induction heating cooker having the temperature sensors according to the embodiment will be described.  FIG. 4  is a control block diagram of the induction heating cooker. 
     Referring to  FIG. 4 , the induction heating cooker includes a power supply unit  60 , a rectification unit  61 , a smoothing unit  63 , an inverter unit  65 , a drive unit  67 , working coils  20 , temperature sensors  30 , a signal cutoff unit  69 , and a controller  50 . 
     The rectification unit  61  may be embodied as a bridge diode to rectify alternating current power input through the power supply unit  60  and to output the rectified pulsating voltage. 
     The smoothing unit  63  smoothes the pulsating voltage supplied from the rectification unit  61  and outputs uniform direct current voltage obtained through smoothing, i.e., smoothed voltage. 
     Upon application of voltage rectified and smoothed by the rectification unit  61  and the smoothing unit  63 , the inverter unit  65  is switching-driven to supply high-frequency current to the working coils  20 . 
     The drive unit  67  turns a switching element of the inverter unit  65  on or off according to a control signal of the controller  50 . 
     The temperature sensors  30  detect temperature of the object  11  heated by electromotive force induced to the object  11  magnetically coupled to the working coils  20 . 
     The signal cutoff unit  69  turns a signal of the controller  50  transmitted to the drive unit  67  on or off according to an output signal of the temperature sensors  30 . The signal cutoff unit  69  may be embodied as a fuse disposed on a line to which power is applied. Alternatively, the signal cutoff unit  69  may be embodied as a circuit including a transistor allowing a control signal output from the controller to flow to the ground according to the output signal of the temperature sensors  30  such that the control signal is not transmitted to the drive unit  67 . 
     The controller  50  controls the overall operation of the induction heating cooker  1  and outputs a control signal to adjust frequency of high-frequency power applied to the working coils  20 . 
     In the induction heating cooker  1 , alternating current power is rectified into direct current power, and high-frequency current is supplied to the working coils  20  through switching of the inverter unit  65 . 
     The switching of the inverter unit  65  is adjusted by the drive unit  67 . The drive unit  67  is operated according to a control signal of the controller  50 . 
     A magnetic field is generated from the working coils  20  by alternating current supplied to the working coils  20 , and an eddy current is induced to the object  11  placed on the cooking table  13  due to electromagnetic induction caused by the magnetic field, with the result that the object  11  is heated. 
     When the object  11  is abnormally heated, the working coils  20  may catch fire or internal components of the induction heating cooker may be damaged. To prevent the occurrence of such ignition or damage, an output signal of the temperature sensors  30  according to temperature measured by the temperature sensors  30  to measure temperature of the object  11 , is transmitted to the signal cutoff unit  69 . When the measured temperature is equal to or greater than a predetermined temperature, the signal cutoff unit  69  cuts off a control signal transmitted from the controller  50  to the drive unit  67 , with the result that high-frequency current supplied to the working coils  20  is cut off by the signal cutoff unit  69  without control of the controller  50 . 
     The number of the temperature sensors  30  corresponds to the number of the working coils  20 . In this embodiment, however, each of the temperature sensors  30  includes heat transfer members  40  to transfer heat generated from adjacent working coils  20 , with the result that temperature of the working coils adjacent to each of the temperature sensors  30  is detected through each of the temperature sensors  30 . Consequently, the number of the temperature sensors  30  may be reduced, and, in addition, a space in which the temperature sensors  30  are disposed is reduced, thereby further improving space utilization. 
     In this embodiment, the control signal transmitted to the drive unit is cut off by the signal cutoff unit. Alternatively, the signal cutoff unit may be omitted, and the controller may directly control the drive unit to prevent overheating of the working coils. 
     In this embodiment, the temperature sensors measure temperature of the working coils  20  when temperature of the induction heating cooker  1  is abnormally increased. Alternatively, the temperature sensors may independently detect temperature of the working coils  20 . 
     To this end, as shown in  FIG. 5 , a sensing unit  71  of a temperature sensor  70  may include a plurality of sensing zones  76 ,  77 ,  78 , and  79 , divided by a plurality of heat insulation walls  73 , each including a plurality of sensing elements  75 , and a plurality of heat transfer members  40  from the respective sensing zones  76 ,  77 ,  78 , and  79  on top of a plurality of working coils  20  disposed adjacent to the temperature sensors  70 , thereby independently detecting temperature of the respective working coils  20 . 
     Each of the sensor elements  75  may be embodied as a platinum resistance temperature sensor, a thermocouple, or a thermistor designed for temperature measurement. 
     With the above structure, the temperature sensor  70  may detect the position of the object  11  placed on the cooking table  13 , or adjust heating power or cooking time based on the temperature of the object  11 . 
     Even in this case, temperatures of working coils  20  are independently sensed by a single temperature sensor, thereby improving productivity and space utilization. 
     As is apparent from the above description, the induction heating cooker according to the embodiment has improved productivity and space utilization. 
     Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.