JP2006114371A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker in which heat changes of a heated object can be detected at a high speed without using a new temperature detecting means such as an infrared ray sensor, and the temperature control more suited for cooking can be carried out. <P>SOLUTION: This is arranged so that a prescribed value of changing amount in control by a control means 10 is set to become larger the longer the time elapses, and in the case there is more change than the prescribed value, the temperature variation of the heated object 1 is determined to be excessive, thereby, the output of an inverter 5 is suppressed or suspended. By this, without using the new temperature detecting means such as the infrared ray sensor, the temperature change of the heated object 1 can be detected at a high speed so that a temperature control more suited for cooking can be carried out. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an induction heating cooker used in general homes, offices, restaurants and the like.

Conventionally, in an induction heating cooker that heats an object to be heated such as a pan, a plurality of methods have been proposed as a method for detecting the temperature of the object to be heated (see, for example, Patent Document 1). That is, a method of detecting the temperature with a thermistor through a top plate on which the object to be heated is placed, a method of detecting the temperature by detecting infrared rays radiated from the side surface of the object to be heated with an infrared sensor at the rear of the top surface of the top plate, or In this method, an infrared sensor is arranged on the lower surface of the top plate, and infrared rays from the object to be heated are detected through the top plate.
Japanese Patent Laid-Open No. 3-184295

  However, the conventional configuration has a problem in stable temperature detection and control in any method. That is, in the method of detecting the temperature of the object to be heated with the thermistor through the top plate, the top plate is made of ceramic having a low heat transfer coefficient. Error occurs, and the temperature of the object to be heated cannot be accurately detected. Also, in the method of detecting the temperature by detecting the infrared radiation radiated from the side of the object to be heated by the infrared sensor behind the top surface of the top plate, the infrared sensor behind the top surface of the top plate is affected by disturbance light such as sunlight and lighting. However, accurate temperature detection is not possible. In addition, an infrared sensor is placed on the bottom of the top panel to detect infrared rays from the object to be heated through the top panel, especially in the case of airing, the temperature difference between the part that is heated by induction and the center part of the object to be heated Since the temperature of the heated portion first increases, the temperature cannot be controlled even when the temperature becomes high, or the temperature unevenness increases.

  The present invention solves the above-mentioned conventional problems, and can detect a temperature change of an object to be heated at high speed without using a new temperature detecting means such as an infrared sensor, and can be used for temperature control more suitable for cooking. An object of the present invention is to provide an induction heating cooker that can be used.

  In order to solve the conventional problem, the induction heating cooker according to the present invention sets a predetermined value of the control change amount by the control means so as to increase as time goes on, and there is a change greater than the predetermined value. In this case, it is determined that the temperature change of the object to be heated is large, and the output of the inverter is suppressed or stopped.

  Thereby, it is possible to detect the temperature change of the object to be heated at high speed without using a new temperature detecting means such as an infrared sensor, and temperature control more suitable for cooking can be performed.

  The induction cooking device of the present invention can detect a temperature change of an object to be heated at high speed without using a new temperature detecting means, and can perform temperature control more suitable for cooking.

  A first invention is a heating coil that generates a high-frequency magnetic field and heats an object to be heated, an inverter that supplies a high-frequency current to the heating coil, and a control that controls the inverter so that an input current of the inverter is constant The control means sets a predetermined value of the amount of change in the control so as to increase as time goes on, and when there is a change over the predetermined value, the temperature change of the object to be heated Detects the temperature change of the object to be heated at high speed without using a new temperature detecting means such as an infrared sensor by using an induction heating cooker that suppresses or stops the output of the inverter. Temperature control more suitable for cooking.

  In particular, according to the second invention, in the first invention, there is provided a material discriminating means for discriminating the material of the object to be heated, and the predetermined value is set in accordance with the material of the object to be heated. Stable temperature control according to

  According to a third aspect of the invention, in particular, in the first or second aspect of the invention, the control means determines that a load has been applied to the object to be heated when the change in the amount of control over time has decreased by a predetermined value or more. By increasing or maintaining the output, the temperature of the object to be heated can be kept constant by quickly detecting a temperature drop and adjusting the heating power even when a load is applied.

  The fourth invention has temperature detection means for detecting the temperature of the heating coil, particularly in any one of the first to third inventions, and the control amount of the control means corrects the change due to the temperature of the heating coil. By doing so, temperature detection and temperature adjustment can be performed with higher accuracy.

  In particular, according to a fifth invention, in any one of the first to fourth inventions, the fifth invention has an automatic cooking mode, and suppresses or stops the output of the inverter based on information preset in accordance with the automatic cooking mode. By doing so, stability due to boiling can be detected by a change in the control amount of the inverter, and usability is improved.

  In particular, the sixth invention has a voltage detection means for detecting the power supply voltage in any one of the first to fifth inventions, and when the power supply voltage fluctuates or is instantaneously stopped, it depends on a change in the control amount over time. Since the control is not performed, the induction heating cooker that does not impair the feeling of use can be obtained without stopping when the power supply is unstable.

  In particular, the seventh invention has a voltage detection means for detecting the power supply voltage in any one of the first to fifth inventions, and when the power supply voltage fluctuates or stops instantaneously, the control amount time only during that time. By ignoring the change and making a determination including the previous change after return, temperature stability can be maintained even when the power supply voltage fluctuates.

  In an eighth aspect of the invention, in particular, in any one of the first to fifth aspects of the invention, there is provided voltage detecting means for detecting the power supply voltage, and when the power supply voltage fluctuates or stops instantaneously, the time variation of the control amount is changed. By resetting and re-measurement after return, temperature stability can be maintained without impairing the feeling of use.

  In particular, the ninth invention includes any one of the first to eighth inventions, comprising timer setting means, and suppresses or stops the output of the inverter when the time change of the control amount during the timer operation becomes a predetermined value or more. By doing so, particularly in the case of a stewed product during the timer operation, it is possible to immediately cope with a case where a sudden temperature rise occurs due to evaporation of moisture.

  In a tenth aspect of the invention, in particular, in any one of the first to ninth aspects of the invention, the thermal power adjustment operation means is provided, and when the user changes the set value, the change amount of the control amount is reset and measured. By correcting it, it is possible to cope with the adjustment of the thermal power and realize a stable temperature according to the type of the object to be heated.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
1 to 4 show an induction heating cooker according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the induction heating cooker of the present embodiment generates a high-frequency magnetic field and heats a heated object 1 such as a pan on the top plate 2, and the heating coil 3 has a high frequency. An inverter 5 for supplying current, a rectifying / smoothing unit 7 to which a commercial power source 6 is input, a control means 10 for controlling the inverter 5 so that an input current of the inverter 5 is constant, and a commercial power source 6 for the inverter 5 Current transformer 14 for detecting the power supply current from the power supply, and a power supply current detection circuit 15 for inputting a detection signal of the current transformer 14 and outputting a detection signal proportional to the magnitude of the power supply current to the control means 10.

  The inverter 5 and the heating coil 3 constitute a high frequency inverter. The inverter 5 is provided with a series connection body of a first switching element 5c and a second switching element 5d (both are IGBTs in the present embodiment). The first diode 5e is connected to the first switching element 5c, and the second diode 5f is connected to the second switching element 5d in antiparallel. A series connection body of the heating coil 3 and the resonance capacitor 5g is connected between the connection point of the switching elements 5c and 5d of the series connection body and the negative terminal of the rectifying and smoothing unit 7.

  The rectifying / smoothing unit 7 is connected to a full-wave rectifier composed of a bridge diode and a low-pass filter composed of a choke coil and a smoothing capacitor between its DC output terminals. An inverter 5 is connected to the output of the rectifying / smoothing unit 7.

  Then, the control means 10 sets a predetermined value of the change amount of the control so as to increase as the time increases, and when the change exceeds the predetermined value, the temperature change of the object to be heated 1 is large. Therefore, control is performed so as to suppress or stop the output of the inverter 5.

  The operation of the induction cooking device configured as described above will be described. The commercial power supply 6 is rectified by the rectifying / smoothing unit 7 and supplies power to the high-frequency inverter having the inverter 5 and the heating coil 3.

  FIG. 2 shows the waveform of each part in the present embodiment. Waveform (a) shows the drive signal of the second switching element 5d, which is on in the HIGH state and off in the LOW state. A waveform (A-1) indicates a waveform of a current flowing through the first switching element 5c and the diode 5e. A waveform (A-2) shows a waveform of a current flowing through the second switching element 5d and the diode 5f. A waveform (c) shows a voltage generated between the collector and the emitter of the second switching element 5d.

  When the first switching element 5c is on, a resonance current is generated in a closed circuit of the first switching element 5c (or the second diode 5f), the heating coil 3, and the resonance capacitor 5g. When the first switching element 5c is turned off, a current flows through the second diode 5f. After the first switching element 5c is turned off, the second switching element 5d is turned on. Therefore, after a current flows through the second diode 5f, the second switching element 5d (or the first diode 5e) is turned on. A resonance current flows through a closed circuit including the heating coil 3 and the resonance capacitor 5g. The driving frequency of the first switching element 5c and the second switching element 5d is varied in the vicinity of about 20 kHz, and the driving time ratio is varied in the vicinity of about ½ as shown in FIG.

  Since the control means 10 receives an output signal proportional to the magnitude of the power supply current from the power supply current detection circuit 15, the first switching element 5c and the second switching element 5d receive input power (output value of the high frequency inverter). The drive frequency is varied and controlled so as to be constant (predetermined value).

  FIG. 3 shows the correlation between the drive frequency and the input power, and the solid line indicates when the temperature of the object to be heated 1 is low, and the broken line indicates when the temperature of the object to be heated 1 is high. The correlation changes depending on the temperature of the heated object 1 because the resistivity of the heated object 1 changes as the temperature rises (generally, the resistivity increases as the temperature rises), and as a result, the heating coil 3 This is because the magnetic coupling of the object to be heated 1 changes. More specifically, since the equivalent series resistance increases and the equivalent inductance also increases, the resonance frequency decreases and Q also decreases. As shown in the figure, for example, when power of 2000 W is to be supplied stably, the drive frequency gradually decreases as the temperature of the article 1 to be heated increases (from point A to point B in the figure). Therefore, the drive frequency when a constant power is supplied is as shown in FIG.

  4A shows the temperature of the article 1 to be heated, FIG. 4B shows the driving frequency, and FIG. 4C shows the input power. As the temperature of the article to be heated 1 rises, the driving frequency decreases. When the temperature of the article to be heated 1 becomes constant, the driving frequency becomes constant. From the above relationship, the temperature change of the object to be heated 1 can be understood by the time change of the drive frequency. With this configuration, it can be seen that the inverter 5 stabilizes the temperature when the control amount of the control means 10 is a change amount that is equal to or less than a predetermined value within a predetermined time. For example, the time required for the change in the control amount varies depending on the difference in heat capacity between the case where the heated object 1 contains food and the case where the object is heated. Therefore, when the time change of the control amount decreases by a predetermined value or more, it is determined that a load (foodstuff) is input to the article 1 to be heated, and the output of the inverter 5 is increased or maintained, so that the temperature can be increased even when the load is applied. By quickly detecting the decrease and adjusting the heating power, the temperature of the object to be heated 1 can be kept constant. In addition, in the case of air-fired, a part of the heat becomes concentrated and the amount of change in control when the maximum temperature reaches a predetermined temperature is less than that of a large heat capacity that increases the temperature as a whole. Less. For this reason, when the time is long, the predetermined value of the change amount is increased. With this setting, a constant temperature control can be performed regardless of the heat capacity.

  That is, the control means 10 is set so that the predetermined value of the control change amount increases as the time increases, and when the change exceeds the predetermined value, the temperature change of the object to be heated 1 changes. It is judged that the output is large, and the output of the inverter 5 is controlled to be suppressed or stopped.

  Thereby, the temperature change of the to-be-heated object 1 can be detected at high speed without using new temperature detection means such as an infrared sensor, and temperature control more suitable for cooking can be performed.

(Embodiment 2)
FIG. 5 shows an induction heating cooker according to Embodiment 2 of the present invention. The same elements as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in the figure, the induction heating cooker according to the present embodiment has a material discriminating means 16 for discriminating the material of the object to be heated 1, and by setting a predetermined value according to the material of the object to be heated 1. The temperature can be controlled stably according to the type of the object 1 to be heated.

  The material discriminating means 16 measures, for example, the voltage value at both ends of the resonance capacitor 5g to determine the type of the object to be heated 1, and matches a predetermined value of the change amount of the control amount with the type of the object to be heated 1. By changing the value to a value, there is little change in characteristics with respect to temperature, for example, non-magnetic SUS has little change with respect to an iron heated object, and more stable temperature control can be performed according to the characteristics. Become.

  In the first and second embodiments, the temperature detecting means for detecting the temperature of the heating coil 3 is provided, and the control amount of the control means 10 corrects the change due to the temperature of the heating coil 3 by the detected temperature of the temperature detecting means. By doing so, temperature detection and temperature adjustment can be performed with higher accuracy. Moreover, it has an automatic cooking mode, and by suppressing or stopping the output of the inverter 5 based on information set in advance in accordance with the automatic cooking mode, the stability due to boiling can be improved by changing the control amount of the inverter 5. It can be detected and is easier to use.

(Embodiment 3)
FIG. 6 shows an induction heating cooker according to Embodiment 3 of the present invention. The same elements as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in the figure, the induction heating cooker of the present embodiment has voltage detection means 17 for detecting the power supply voltage of the commercial power supply 6, and when the power supply voltage fluctuates or stops instantaneously, the control variable changes with time. The control by is not performed. As a result, in the case of unstable power supply fluctuation, the feeling of use is not impaired without stopping.

  Note that if the power supply voltage fluctuates or stops instantaneously, the time variation of the control amount is ignored only during that time, and after the return, the determination including the previous change is made, so that the temperature can be changed even when the power supply voltage fluctuates. It can maintain stability. In addition, when the power supply voltage fluctuates or stops instantaneously, temperature stability can be maintained without impairing the feeling of use by resetting the time change of the control amount and measuring again after the return.

  Furthermore, a timer setting means is provided, and in the case of a set long-time simmered food or the like, when the time change of the control amount during the timer operation becomes a predetermined value or more, the output of the inverter 5 is suppressed or stopped to In particular, in the case of stewed food, it is possible to immediately cope with a sudden temperature rise caused by evaporation of water. In addition, it has thermal power adjustment operation means, and when the user changes the set value, it can respond to the thermal power adjustment by resetting the amount of change in the control amount and re-measurement. It is possible to realize a stable temperature according to the temperature.

  In each of the first to third embodiments described above, a two-stone SEPP inverter configuration is used. However, for example, a one-stone voltage resonance inverter such as a one-stone voltage resonance type inverter whose input current changes due to a change in magnetic coupling with a load (object to be heated). Any configuration or control type inverter may be used. Furthermore, although the power is varied using the frequency, this is not limited, and it goes without saying that, for example, a method of changing the conduction ratio of the two stone switching elements at a constant frequency may be used. And each structure shown by each Embodiment 1-3 can be combined suitably as needed, and is not restricted to embodiment itself.

  As described above, the induction heating cooker according to the present invention can detect a temperature change of an object to be heated at high speed without using a new temperature detection means, and can perform temperature control more suitable for cooking. It can be applied to cookers used in general homes, offices, restaurants, etc.

The block diagram which shows the induction heating cooking appliance in Embodiment 1 of this invention The figure which shows the operation | movement waveform of each part of an inverter in the induction heating cooking appliance The figure which shows the frequency and input power correlation at the time of the temperature change of the to-be-heated material in the induction heating cooking appliance. The figure which shows the time change of the temperature of a to-be-heated material, a drive frequency, and input electric power in the same induction heating cooking appliance. The block diagram which shows the induction heating cooking appliance in Embodiment 2 of this invention The block diagram which shows the induction heating cooking appliance in Embodiment 3 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Object to be heated 2 Top plate 3 Heating coil 5 Inverter 6 Commercial power supply 7 Rectification smoothing part 10 Control means 16 Material discrimination means 17 Power supply voltage detection means

Claims (10)

A heating coil that generates a high-frequency magnetic field and heats an object to be heated; an inverter that supplies a high-frequency current to the heating coil; and a control unit that controls the inverter so that an input current of the inverter is constant, The control means sets a predetermined value of the change amount of the control so as to increase as time goes on, and determines that the temperature change of the object to be heated is large when there is a change over the predetermined value. An induction heating cooker that suppresses or stops the output of the inverter. The induction heating cooker according to claim 1, further comprising a material discriminating unit for discriminating a material of the object to be heated, wherein a predetermined value is set according to the material of the object to be heated. 3. The control unit according to claim 1, wherein the control unit determines that a load is applied to the object to be heated when the change in the control amount with time decreases by a predetermined value or more, and increases or maintains the output of the inverter. Induction heating cooker. The induction heating cooker according to any one of claims 1 to 3, further comprising temperature detecting means for detecting the temperature of the heating coil, wherein a control amount of the control means corrects a change due to the temperature of the heating coil. . The induction heating cooker according to any one of claims 1 to 4, further comprising an automatic cooking mode, wherein the output of the inverter is suppressed or stopped based on information preset in accordance with the automatic cooking mode. The induction according to any one of claims 1 to 5, further comprising a voltage detection means for detecting a power supply voltage, wherein the control based on a change in the amount of control over time is not performed when the power supply voltage fluctuates or stops instantaneously. Cooking cooker. There is a voltage detection means for detecting the power supply voltage, and when the power supply voltage fluctuates or stops instantaneously, the time change of the control amount is ignored only during that time, and after the return, the judgment including the previous change is made. Item 6. The induction heating cooker according to any one of items 1 to 5. 6. A voltage detection means for detecting a power supply voltage, and when the power supply voltage fluctuates or stops instantaneously, the time change of the control amount is reset and measured again after returning. The induction heating cooker described in 1. The induction heating cooker according to any one of claims 1 to 8, further comprising a timer setting unit, wherein the output of the inverter is suppressed or stopped when a time change of the control amount during the timer operation becomes a predetermined value or more. The induction heating cooker according to any one of claims 1 to 9, further comprising a heating power adjusting operation means, wherein when the user changes a set value, the change in the controlled variable is reset and measured again. .

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