JP5838314B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker having a scoring detection function.

  As a conventional induction heating cooker having a scorch detection function, for example, the one described in Patent Document 1 is known. This induction heating cooker has an automatic cooking mode. Specifically, the boiling detection operation is performed after the start of heating, and the cooking pot is determined according to the temperature and input power when the boiling is detected, and the temperature change pattern until the boiling. Measure the viscosity and volume of the food present inside to determine the cooking power required for heating after boiling, and if the soup runs out and the temperature at the bottom of the pan rises above the specified value, Detects burning.

  Hereinafter, an induction heating cooker according to an exemplary prior art will be described with reference to FIGS. 12 and 13. FIG. 12 is a block diagram of an induction heating cooker according to an exemplary prior art, and FIG. 13 is a flowchart showing an operation of the induction heating cooker of FIG.

  In FIG. 12, the induction heating cooker includes a top plate 102, an induction heating coil 103, a thermistor 104, an inverter circuit 108, a burn detection circuit 105, a power switch 106, an operation panel 110, and a controller 107. Prepare. The top plate 102 is a crystallized ceramic plate provided on the upper surface of the induction heating cooker, and the induction heating coil 103 and the thermistor 104 are provided below the top plate 102. When the cooking container 101 such as a pan is heated, the cooking container 101 is placed on the top plate 102 so that the bottom faces the induction heating coil 103, and high frequency current is supplied from the inverter circuit 108 to the induction heating coil 103. Is done. The thermistor 104 detects the temperature of the cooking container 101 by measuring the back surface temperature of the top plate 102, and sends a temperature signal of the detection result to the controller 107. The temperature signal is further sent from the controller 107 to the scoring detection circuit 105. The scoring detection circuit 105 detects the presence or absence of scoring based on the temperature signal and sends a scoring detection result signal indicating the detection result to the controller 107. The controller 107 controls the operation of the inverter circuit 108 based on the temperature signal, the burn detection result signal, and the control signal from the power switch 106 and the operation panel 110. Specifically, the inverter circuit 108 includes a switching element and a resonance capacitor (not shown), and the controller 107 controls the on / off of the switching element of the inverter circuit 108 to heat the cooking vessel 101. The output power of 108 is controlled. Furthermore, the controller 107 stops the heating of the cooking container 101 when the burn detection circuit 105 detects the burn.

  The operation panel 110 operated by the user has a heating start / end key 110a for instructing the start and end of the heating operation, a setting key 110b for setting output power and the like, and an operation mode of the induction heating cooker. Mode selection key 110c is provided. For example, the setting key 110b changes the output power setting value each time it is pressed in order to select one of a plurality of different output power setting values (corresponding to the output power of the inverter circuit 108) that can be set in the induction heating cooker. A down key 110bb that decreases by one step and an up key 110ba that increases the output power set value by one step each time the key is pressed are included. The operation mode of the induction heating cooker includes, for example, a “heating mode” in which the cooking container 101 is heated with the output power of the inverter circuit 108 corresponding to the output power set value selected by the setting key 110b, and a predetermined small output. It includes a “boiled mode” in which the cooking container 101 is heated with electric power and burnt detection is performed.

  The operation of the induction heating cooker according to the prior art will be described below with reference to FIG.

  In FIG. 13, when the power switch 106 is turned on (step S1), the controller 107 enters a standby state. In the standby state, the heating operation of the induction heating cooker is stopped, and at this time, by operating the mode selection key 110c of the operation panel 110, a plurality of operation modes of the induction heating cooker (for example, the heating mode and the stew mode described above). ) Can be selected.

  When one operation mode is selected in the standby state (step S2) and the heating start / end key 110b is pressed (step S3), the heating operation is started in the selected operation mode. When the stew mode is selected and the heating operation is started (YES in step S4), the controller 107 prohibits changing the output power setting value with the setting key 110b and detects the burn using the burn detection circuit 105. (Step S6). Preferably, as described in Patent Document 1, the output power for heating is automatically controlled after detecting the boiling, and when it is detected that the temperature of the cooking vessel 101 has risen abnormally, it is determined that scorching has occurred. Detect.

  When the heating operation is started by selecting the heating mode, for example, when the heating operation is started (NO in step S4), the controller 107 does not execute the burn detection (step S5), and the output power setting value is set by the setting key 110b. When changed, the output power of the inverter circuit 108 is controlled in accordance with the output power set value.

Japanese Patent Laid-Open No. 10-149875

  However, in the conventional configuration, the operation mode in which the burn-in detection can be performed is limited to the stew mode, and in the stew mode, it is prohibited to change the output power set value by the setting key 110b. In other words, in the heating mode in which the user can change the output power setting value with the setting key 110b, the burn-in detection cannot be performed. In order to use the burn-in detection, the output power of the inverter circuit 108 is automatically set. There was a problem that a stew mode to be set had to be selected.

  The present invention solves the above-mentioned conventional problems, and the user arbitrarily selects an induction heating cooker capable of performing scoring detection without distinction between the stew mode and the heating mode, that is, the output power for heating the cooking container. An easy-to-use induction heating cooker that can perform scoring detection when necessary (heating mode) and can suppress the scoring detection function from operating unnecessarily and adversely affecting normal cooking. The purpose is to provide.

In order to solve the conventional problem, the induction heating cooker of the present invention is
A top plate on which the cooking container is placed;
An induction heating coil provided under the top plate for heating the cooking vessel;
An inverter circuit for supplying a high-frequency current to the induction heating coil with a predetermined output power;
An infrared sensor that is provided under the top plate and that measures the temperature of the bottom of the cooking container by detecting infrared radiation emitted from the bottom of the cooking container and transmitted through the top plate;
A selection device for obtaining one output power setting value selected from a plurality of output power setting values;
In an induction heating cooker comprising: a controller that controls the inverter circuit so that the output power of the inverter circuit becomes an output power corresponding to the selected output power setting value;
The controller is
When the temperature is less than a predetermined first threshold at a predetermined time after starting the heating of the cooking container or at a time when a predetermined integrated electric energy is consumed since the heating of the cooking container is started, When the second threshold value higher than the first threshold value is used as a burn-in threshold value to start burn-in detection, and the temperature increases above the burn-in threshold value, the contents of the cooking container Detects burnt objects,
When the temperature is lowered over a predetermined temperature drop amount or when the temperature does not rise over a predetermined time, a cooking operation for the contents of the cooking container is detected,
When neither the burn-in nor the cooking operation is detected within a predetermined first time period from the start of the burn-in detection, the second threshold value is substituted for the second threshold value. The burn detection is continued using a small third threshold as the burn threshold.

  According to the induction heating cooker of the present invention, when cooking in a heating mode that is heated with output power selected by the user and cooking boiled food with medium or low heat, the type of cooking container (heat capacity) Even if the bottom surface temperature of the cooking container is difficult to increase due to foodstuffs, etc., it can be reliably detected when it is burnt, and the burn can be prevented from becoming serious. According to the induction heating cooker of the present invention, in addition, when cooking that is not boiled, by switching the burnt threshold to a higher value or not suppressing the output power, boiling or frying When cooking with high output power typified by things, such as when the user is near a cooking container and cooking is not required, the burn detection function works and is unnecessary In addition, it is possible to prevent the heating from being stopped or the output power from being lowered, and the user can continue cooking without feeling uncomfortable, so that the usability is not deteriorated.

  The induction cooking device of the present invention is a cooking container when the user performs heating operation in a heating mode that is an operation mode in which cooking is performed by selecting output power and cooking boiled food with a low heating power Even if the temperature at the bottom of the pan is difficult to rise due to the type of food (such as a large heat capacity) or ingredients, it will reliably detect scorching when burnt, and it may not be useful when cooking at high temperatures such as fried foods. It is possible to improve the usability of the induction heating cooker by preventing the burn detection function from operating as necessary.

The whole block diagram of the induction heating cooking appliance in embodiment of this invention Schematic circuit diagram of the infrared sensor 4 of FIG. The figure which shows the temperature-voltage characteristic of the infrared sensor 4 of FIG. The figure for demonstrating the boiled food determination performed with the induction heating cooking appliance of FIG. The figure for demonstrating the modification of the boiled food determination performed with the induction heating cooking appliance of FIG. The figure for demonstrating the burning detection performed by the induction heating cooking appliance of FIG. The figure for demonstrating the 1st modification of the burning detection performed by the induction heating cooking appliance of FIG. The figure for demonstrating the 2nd modification of the burning detection performed by the induction heating cooking appliance of FIG. The figure for demonstrating the temperature control performed by the induction heating cooking appliance of FIG. 1 when the temperature of the cooking vessel 2 of FIG. 1 reaches the burning detection temperature Temp2. The figure for demonstrating the temperature control performed by the induction heating cooking appliance of FIG. 1 when the temperature of the cooking vessel 2 of FIG. 1 reaches the burning detection temperature Temp2. The figure for demonstrating the temperature control performed by the induction heating cooking appliance of FIG. 1 when the temperature of the cooking vessel 2 of FIG. 1 reaches the burning detection temperature Temp2. Block diagram of induction heating cooker according to the prior art The flowchart which shows operation | movement of the induction heating cooking appliance of FIG.

The first invention is
A top plate on which the cooking container is placed;
An induction heating coil provided under the top plate for heating the cooking vessel;
An inverter circuit for supplying a high-frequency current to the induction heating coil with a predetermined output power;
An infrared sensor that is provided under the top plate and that measures the temperature of the bottom of the cooking container by detecting infrared radiation emitted from the bottom of the cooking container and transmitted through the top plate;
A selection device for selecting one output power setting value selected from a plurality of output power setting values;
In an induction heating cooker comprising: a controller that controls the inverter circuit so that the output power of the inverter circuit becomes an output power corresponding to the selected output power setting value;
The controller is
When the temperature is less than a predetermined first threshold at a predetermined time after starting the heating of the cooking container or at a time when a predetermined integrated electric energy is consumed since the heating of the cooking container is started, When the second threshold value higher than the first threshold value is used as a burn-in threshold value to start burn-in detection, and the temperature increases above the burn-in threshold value, the contents of the cooking container Detects burnt objects,
When the temperature is lowered over a predetermined temperature drop amount or when the temperature does not rise over a predetermined time, a cooking operation for the contents of the cooking container is detected,
When neither the burn-in nor the cooking operation is detected within a predetermined first time period from the start of the burn-in detection, the second threshold value is substituted for the second threshold value. The burn detection is continued using a small third threshold as the burn threshold.
According to the present invention, when cooking boiled food with medium or low heat (ie, output power), it is difficult to raise the temperature of the bottom of the cooking container due to the type of cooking container (such as a large heat capacity) or food Even so, when it is burned, it can be reliably detected and the burn can be prevented from becoming serious, so the usability of the induction heating cooker can be improved.
According to the present invention, it is possible to discriminate between the fried food and the boiled food regardless of the output power setting value selected by the user. It is possible to prevent the burnt state from getting worse, and since the burnt detection does not work unnecessarily in fried cooking, the usability of the induction heating cooker can be improved.

According to a second aspect of the invention, in particular, in the first aspect of the invention, the controller is configured such that the temperature reaches the first threshold when a predetermined second time period has elapsed since the heating of the cooking container was started. When the value is less than the value, the burning detection is started.
According to the present invention, it is possible to discriminate between the fried food and the boiled food regardless of the output power setting value selected by the user. It is possible to prevent the burnt state from getting worse, and since the burnt detection does not work unnecessarily in fried cooking, the usability of the induction heating cooker can be improved.

In a third aspect of the invention, in particular, in the first or second aspect of the invention, the controller has detected neither the burning nor the cooking operation within the first time period from the start of the burning detection. The burnout detection is continued using one of a plurality of different third threshold values smaller than the second threshold as the burnout threshold instead of the second threshold. The third threshold value used increases as the selected output power setting value increases.
According to the present invention, according to the selected output power setting value, it is possible to reliably detect scoring even when the output power is low, and not to detect scoring unnecessarily when a cooking operation is detected. can do.

In a fourth aspect of the present invention, in particular, in any one of the first to third aspects, the controller uses the first time period as a cycle, and the burn is performed within the first time period. When neither cooking operation nor the cooking operation is detected, the burn-in detection is repeated and continued.
According to the present invention, when simmered cooking is performed in which the bottom temperature of the cooking container is not easily raised, the third threshold value is again switched to the third threshold value smaller than the second threshold value. If it is above, it is possible to detect scoring, so that scoring can be reliably detected when scoring detection is necessary.

According to a fifth aspect of the present invention, in particular, in the fourth aspect of the present invention, when the controller does not detect either the burning or the cooking operation within the first time period, the second threshold value is used. Instead of using the one of a plurality of different third threshold values smaller than the second threshold value as a burned threshold value, the burnout detection is continuously repeated, and the used second threshold value is used. The threshold value of 3 is reduced each time the burnout detection is repeated.
According to the present invention, it is possible to reliably detect scorching even when the heating power is low or when a cooking container or food that does not easily rise in temperature is used.

In a sixth aspect of the invention, in particular, in any one of the first to fifth aspects of the invention, when the controller uses the third threshold value as a burning threshold value, the cooking operation is performed. When detected, the burn detection is performed by using the second threshold value or a fourth threshold value larger than the second threshold value as the burn threshold value instead of the third threshold value. It is characterized by continuing.
According to the present invention, when the cooked food is not boiled, the burn threshold is switched to a higher value so that the burn is detected when the user is cooking near the cooking container and does not need the burn detection function. The function can be avoided and the user can continue cooking without feeling uncomfortable.

In a seventh aspect of the present invention, in particular, in any one of the first to sixth aspects, the controller stops heating the cooking container when it detects the burning.
According to the present invention, it is possible to prevent the burnt state from deteriorating.

The eighth invention is characterized in that, in particular, in any one of the first to sixth inventions, the controller reduces the output power of the inverter circuit when the burn is detected.
ADVANTAGE OF THE INVENTION According to this invention, when a user does not want to stop a heating easily (when cooking which wants to make it burn), the usability of an induction heating cooking appliance can be improved.

In a ninth aspect of the invention, in particular, in any one of the first to sixth aspects of the invention, when the controller detects the burning, the second threshold is used instead of the second threshold value. The burn detection is continued using a fifth threshold value higher than the value, and heating of the cooking container is stopped when the temperature increases to the fifth threshold value or more. .
ADVANTAGE OF THE INVENTION According to this invention, when cooking which wants to be burnt like steaming is performed, it can be made not to detect burnt easily.

  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)
FIG. 1 is an overall configuration diagram of an induction heating cooker according to an embodiment of the present invention. The induction heating cooker of the present embodiment includes a top plate 1, an induction heating coil 3, an infrared sensor 4, a rectifier circuit 8, an inverter circuit 12, an input current detector 7, an operation panel 16, and a controller. 17.

  The top plate 1 is a plate made of an electrical insulator such as ceramic or glass provided on the upper surface of the induction heating cooker, and transmits infrared rays. The induction heating coil 3 is provided below the top plate 1. When the cooking container 2 such as a pan is heated, the cooking container 2 is placed on the top plate 1 so that the bottom surface faces the induction heating coil 3, and high frequency current is supplied to the induction heating coil 3 from the inverter circuit 12. Is done. The induction heating coil 3 induction-heats the cooking container 2 by generating a high-frequency magnetic field and generating an eddy current in the cooking container 2 on the top plate 1. The induction heating coil 3 is divided into two concentric circles to form an outer coil 3a and an inner coil 3b.

  In the present embodiment, a gap is provided between the outer coil 3a and the inner coil 3b of the induction heating coil 3, and an infrared sensor 4 for detecting the bottom surface temperature of the cooking container 2 is provided below the gap. Infrared rays are emitted from the bottom surface of the cooking vessel 2 in accordance with the bottom surface temperature of the cooking vessel 2, and the emitted infrared rays pass through the top plate 1 and then pass through the gap between the outer coil 3a and the inner coil 3b. And received by the infrared sensor 4. The infrared sensor 4 detects the amount of received infrared rays and outputs an infrared detection signal 5 having a voltage corresponding to the detected amount of infrared rays to the controller 17. The position where the infrared sensor 4 is installed is not limited to the gap between the outer coil 3a and the inner coil 3b, and may be any position as long as the bottom surface temperature of the cooking container 2 can be detected.

  FIG. 2 is a schematic circuit diagram of the infrared sensor 4 of FIG. The infrared sensor 4 includes a photodiode 21, an operational amplifier 22, and resistors 23 and 24. One ends of the resistors 23 and 24 are connected to the photodiode 21, and the other ends are connected to the output terminal and the inverting output terminal of the operational amplifier 22, respectively. The photodiode 21 is a light receiving element formed of InGaAs or the like. This is a current that flows when an infrared ray having a wavelength of about 3 microns or less is irradiated. The higher the temperature of the irradiated infrared ray, the higher the current that flows. The size and the rate of increase are increased. The current generated by the photodiode 21 is amplified by the operational amplifier 22 and output as an infrared detection signal 5 (represented by a voltage value V0) indicating the temperature of the cooking vessel 2. Since the infrared sensor 4 receives infrared rays emitted from the cooking container 2, the infrared sensor 4 has better thermal response than a thermistor that detects the temperature via the top plate 1.

  FIG. 3 is a diagram showing temperature vs. voltage characteristics of the infrared sensor 4 of FIG. In FIG. 3, the horizontal axis represents the bottom surface temperature (° C.) of the cooking container 2, and the vertical axis represents the voltage value (V) of the infrared detection signal 5 output from the infrared sensor 4.

  Since the photodiode 21 is a light receiving element in which the magnitude and increase rate of the flowing current increases as the temperature of the irradiated infrared light increases, the temperature is divided into a plurality of ranges, and an infrared detection signal is detected for each temperature range. The amplification factor of 5 may be switched. For example, as shown in FIG. 3, it has the characteristic of “5a” in the temperature range (low temperature range) of 120 ° C. to 200 ° C., and “5b” in the temperature range of 200 ° C. to 250 ° C. (medium temperature range). The amplification factor of the infrared detection signal 5 may be switched for each temperature range so as to have the characteristic “5c” in the temperature range (high temperature range) of 250 to 330 ° C. The amplification factor of the infrared detection signal 5 may be switched in a temperature calculation circuit 34 (described later) of the controller 17, or the amplification factor of the circuit itself in the infrared sensor 4 may be variable.

  The infrared sensor 4 does not output the infrared detection signal 5 when the bottom surface temperature of the cooking vessel 2 is less than about 120 ° C. “Do not output the infrared detection signal 5” in this case is not only the case where the infrared detection signal 5 is not output at all, but also the fact that the controller 17 does not output substantially, that is, the controller 17 is based on the change in the magnitude of the infrared detection signal 5. This includes a case where a weak signal that cannot substantially read the temperature change of the bottom surface of the cooking container 2 is output. The voltage value of the infrared detection signal 5 increases exponentially when the temperature of the cooking vessel 2 reaches about 120 ° C. or higher.

  The infrared sensor 4 is not limited to a photodiode, and may be any sensor that can detect a temperature change using infrared rays, such as a thermopile.

  Referring again to FIG. 1, the rectifier circuit 8 converts alternating current supplied from the commercial power supply 6 into direct current, and the inverter circuit 12 generates a high-frequency current from the direct current supplied from the rectifier circuit 8, and generates the generated high-frequency signal. An electric current is output to the induction heating coil 3. The rectifier circuit 8 includes a full-wave rectifier 9 constituted by a bridge diode, and a low-pass filter constituted by a choke coil 10 and a smoothing capacitor 11 connected between output terminals of the full-wave rectifier 9. The inverter circuit 12 includes a switching element 14 (IGBT in the present embodiment), a diode 15 connected in antiparallel to the switching element 14, and a resonance capacitor 13 connected in parallel to the induction heating coil 3. By turning on / off the switching element 14 of the inverter circuit 12, a high-frequency current is generated with a predetermined output power. Further, an input current detector 7 such as a current transformer for detecting an input current flowing from the commercial power supply 6 to the rectifier circuit 8 is provided between the commercial power supply 6 and the rectifier circuit 8.

  The operation panel 16 is provided on the user side of the induction cooking device when viewed from the top plate 1. The operation panel 16 includes a plurality of capacitance type switches 16a to 16c for inputting instructions regarding cooking. The switches 16a to 16c are provided corresponding to the number of induction heating coils. The switches 16a to 16c are not limited to the capacitance type, and may be a push button type such as a tact switch. In addition, a display panel (not shown) is provided between the operation panel 16 and the cooking container 2.

  A specific function is assigned to each of the switches 16a to 16c. The switch 16a is a heating start / end key for instructing the start and end of the heating operation, the switch 16b is a setting key for selecting an output power set value, and the switch 16c is an induction heating cooking It is a mode selection key for selecting the operation mode of the device.

  For example, the setting key 16b selects an output power setting value each time it is pressed in order to select one of a plurality of different output power setting values (corresponding to the output power of the inverter circuit 12) that can be set in the induction heating cooker. An up key 16ba that increases by one step and a down key 16bb that decreases the output power set value by one step each time the key is pressed are included. The user operates the up key 16ba and the down key 16bb to set output power setting values including a plurality of different stages (for example, seven stages including “100 W, 500 W, 700 W, 1000 W, 1450 W, 2000 W, 3000 W”, Or, one of “100 W, 500 W, 700 W, 1000 W, 2000 W, 3000 W” is selected, and the selected output power setting value is notified to the controller 17.

  The operation mode of the induction heating cooker includes, for example, a “heating mode” in which the cooking container 2 is heated with the output power of the inverter circuit 12 corresponding to the output power set value selected by the setting key 16b. In the induction heating cooker according to the prior art, the stew mode had to be selected as the operation mode in order to detect burnt, but the induction cooker according to the present embodiment performs burnt detection even in the heating mode. It is not necessary for the user to select a specific operation mode in advance in order to detect burn-in. Therefore, in the following description, it is assumed that the induction heating cooker operates in the heating mode (that is, the heating mode is selected by the mode selection key 16c). Moreover, the operation | movement when the burning of the contents of the cooking container 2 is detected is selected by the mode selection key 16c (after-mentioned).

  Based on the setting information (output power setting value and the like) of the induction heating cooker input from the operation panel 16 by the user and the bottom surface temperature of the cooking vessel 2 detected by the infrared sensor 4, the controller 17 is connected to the inverter circuit 12. To control the output power. Specifically, the controller 17 controls on / off of the switching element 14 of the inverter circuit 12 so as to control the output power of the inverter circuit (inverter control).

  Based on the input from the operation panel 16, the controller 17 controls the output power of the inverter circuit 12 as follows, for example. In a standby state in which the heating operation of the induction heating cooker is stopped, an operation mode (for example, a heating mode) during heating can be selected. When the heating start / end key 16a is pressed while the heating mode is selected and the standby state is set, the heating operation is started, and the controller 17 automatically sets the output power of the inverter circuit 12 to, for example, “1000 W”. Set. When the induction heating cooker is operating in the heating mode, the output power of the inverter circuit 12 can be changed by operating the setting key 16b. When the output power setting value of the inverter circuit 12 is changed by the setting key 16b, the changed output power setting value is sent to the controller 17. The controller 17 monitors the input current of the inverter circuit 12 with the input current detector 7 and controls the output power of the inverter circuit 12 so as to be the output power corresponding to the selected output power setting value. As a result, a high-frequency current having a required magnitude is supplied to the induction heating coil 3.

  The controller 17 includes an inverter control circuit 31, a timer 32, a memory 33, a temperature calculation circuit 34, a current measurement circuit 35, and a burnout detection circuit 36. The inverter control circuit 31 controls on / off of the switching element 14 of the inverter circuit 12. The timer 32 generates and supplies time information used in the burn detection of the burn detection circuit 36. The memory 33 stores various data required during operation (temperature threshold, temporary data during operation, etc.). The temperature calculation circuit 34 converts the voltage of the infrared detection signal 5 into a temperature and notifies the burn detection circuit 36 of the temperature. The temperature calculation circuit 34 may be omitted, and the voltage of the infrared detection signal 5 may be directly notified to the burn detection circuit 36 instead of the temperature. The current measurement circuit 35 measures the current detected by the input current detector 7. The burn detection circuit 36 includes an integrating wattmeter 41, a cooking operation detection circuit 42, and a determination circuit 43. The integrated wattmeter 41 measures the integrated amount of power consumed by heating the cooking vessel 2 from the current measured by the current measuring circuit 35. The cooking operation detection circuit 42 detects whether the user of the induction heating cooker is performing a cooking operation (described later) on the contents of the cooking container 2. The determination circuit 43 detects the burning of the contents of the cooking container 2.

  The scoring detection circuit 36 acquires the temperature of the cooking container 2 from the temperature calculation circuit 34 and determines whether or not the cooking currently being performed is boiled cooking. Specifically, the scoring detection circuit 36 determines that the cooking is boiled when the temperature is lower than a first threshold value (for example, 130 ° C.) at a predetermined time after the heating of the cooking container 2 is started, A second threshold temperature higher than the first threshold (for example, about 159 ° C.) is used as a burning threshold, and burning detection (described later) is started.

  FIG. 4 is a diagram for explaining boiled food determination executed by the induction heating cooker of FIG. 1. The scoring detection circuit 36 acquires time data from the timer 32, and when the predetermined time period (for example, 1 minute) has elapsed after the heating of the cooking container 2 has started, the bottom surface temperature of the cooking container 2 is the first temperature. When it is less than the threshold Temp1, it is determined that the food is boiled and the scorch detection is started.

  Preferably, the burn-in detection circuit 36 may use the integrated power amount measured by the integrated wattmeter 41 in place of the time data acquired from the timer 32 in order to perform the boiled food determination. FIG. 5 is a diagram for explaining a modified example of the boiled food determination executed by the induction heating cooker of FIG. 1. The scoring detection circuit 36 has a bottom surface temperature of the cooking container 2 that is lower than the first threshold Temp1 at a time point Time1 when a predetermined integrated power amount (which may be arbitrarily set) is consumed after the heating of the cooking container 2 is started. If it is, it is determined that the cooking is boiled, and detection of burnt is started. The integrated power amount may be set to a different value for each material of the cooking vessel 2 (for example, aluminum, magnetic stainless steel, nonmagnetic stainless steel, etc.). The material of the cooking vessel 2 can be determined by a known method, for example, based on the relationship between the input current and the resonance voltage.

  Referring to FIG. 1 again, the cooking operation detection circuit 42 acquires the temperature of the cooking container 2 from the temperature calculation circuit, and the user is performing the cooking operation on the contents of the cooking container 2 (that is, the temperature). It is detected whether or not a certain load is applied. The cooking operation includes, for example, putting ingredients into the cooking container 2 and stirring the contents of the cooking container 2, and the cooking operation detection circuit 42 has a bottom surface temperature of the cooking container 2 that is a predetermined short time from the temperature at an arbitrary time. When the temperature has decreased over a predetermined temperature decrease amount (for example, 3 ° C.) within a time period (for example, several seconds), it is detected that there has been a cooking operation. The amount of temperature decrease used for the cooking operation can be any amount as long as it does not cause erroneous detection. For example, any temperature decrease amount of 2 ° C to 5 ° C can be used. is there. The cooking operation detection circuit 42 also detects that there has been a cooking operation even when the cooking vessel 2 is heated and the bottom surface temperature of the cooking vessel 2 does not rise over a predetermined time.

  The determination circuit 43 acquires the temperature of the cooking container 2 from the temperature calculation circuit, acquires time data from the timer 32, acquires an integrated power amount from the integrated wattmeter 41, and detects a cooking operation detection result from the cooking operation detection circuit 42. And the burning of the contents of the cooking container 2 is detected. When the temperature is lower than the first threshold value at a predetermined time after the heating of the cooking container 2 is started, the determination circuit 43 burns the second threshold value higher than the first threshold value. Use as a threshold value to start scoring detection, and when the temperature increases above the scoring threshold, the scoring of the contents of the cooking container 2 is detected, and within the first time period from the start of scoring detection When neither scorching nor cooking operation is detected, scoring detection is performed using the temperature of the third threshold value smaller than the second threshold value as the scoring threshold value instead of the second threshold value. continue. The determination circuit 43 stops the heating of the cooking container 2 (described later) when it detects the burning.

  The determination circuit 43 uses the first time period as a cycle, and repeats the scoring detection when neither scoring nor cooking operation is detected within each periodic first time period. In addition, the determination circuit 43 replaces the second threshold value with a plurality smaller than the second threshold value when neither scoring nor cooking operation is detected within each periodic first time period. One of the different third thresholds is used as the burn threshold, and the burn detection continues repeatedly, and the third threshold used decreases each time burn detection is repeated To do.

  The one or more third threshold values are, for example, temperatures between the first threshold value (eg about 130 ° C.) and the second threshold value (eg about 159 ° C.), instead. The temperature may be equal to or lower than the first threshold value. When the temperature is equal to or lower than the first threshold value, the temperature is preferably set to be equal to or higher than the temperature at which water boils.

  FIG. 6 is a diagram for explaining scoring detection performed by the induction heating cooker of FIG. 1. As described with reference to FIGS. 4 and 5, when scoring detection is started at time Time 1, the determination circuit 43 uses the second threshold value Temp 2 as the initial value of the scoring threshold value. . When the bottom surface temperature of the cooking container 2 has increased to the second threshold Temp2 or more within the time period (for example, 600 seconds) from the time Time1 to the time Time2 when the scoring detection is started, Detect burnt contents. On the other hand, when the burn is not detected within the time period from time Time1 to time Time2 and the cooking operation is not detected by the cooking operation detection circuit 42, the determination circuit 43 sets the second threshold Temp2. Instead, the third threshold Temp3a smaller than the second threshold Temp2 is used as the burn threshold, and the burn detection is continued.

  The determination circuit 43 uses the time period from the time Time1 to the time Time2 as a cycle, and when neither scorching nor cooking operation is detected within each periodic time period, the scoring detection is repeated and continued. In the present embodiment, for example, Time Time 1 to Time Time 2, Time Time 2 to Time Time 3, Time Time 3 to Time Time 4, and Time Time 4 to Time Time 5 are the same time period (for example, 600 seconds).

  The determination circuit 43 may use a plurality of different third threshold values Temp3a, Temp3b, and Temp3c that are smaller than the second threshold value Temp2. When the determination circuit 43 detects neither burning nor cooking operation within each periodic time period, the determination circuit 43 replaces the second threshold value Temp2 with a plurality of different third threshold values Temp3a, Temp3b, Temp3c. Use one of them as the burn threshold to repeat burn detection and continue. The third threshold value that is used decreases each time it repeats scoring detection. In the example shown in FIG. 6, the burn-in threshold Temp3a is used in the time period from time Time2 to time Time3, neither burning nor cooking operation is detected, and burning detection is continuously repeated in the next time period. . Next, in the time period from time Time3 to time Time4, the burning threshold Temp3b (Temp3b <Temp3a) is used, neither burning nor cooking operation is detected, and burning detection is continuously repeated in the next time period. . In the time period from time Time4 to time Time5, the burn-in threshold Temp3c (Temp3c <Temp3b) is used, and the bottom surface temperature of the cooking container 2 has reached the burn-in threshold Temp3c. Burning is detected.

  Further, the third threshold value that is actually used as the burned threshold value among the plurality of third threshold values Temp3a, Temp3b, and Temp3c is the output power setting selected by the user using the setting key 16b. Depending on the value, it may be set to increase as the output power set value increases (ie, decrease as the output power set value decreases). For example, when the output power setting value “100 W, 500 W, 700 W” or the like is selected, the third threshold value is smaller than when the output power setting value “1000 W, 2000 W, 3000 W” or the like is selected. Is used.

  Further, it is not always necessary to decrease the third threshold value every time the burn-in detection is repeated. After the third threshold value is decreased by a predetermined number of times, the burn-in detection may be repeated. The same third threshold may continue to be used.

  However, when any of the third threshold values Temp3a, Temp3b, and Temp3c is used as a burning threshold value, the determination circuit 43 burns the second threshold value Temp2 when a cooking operation is detected. Use as a threshold to continue scoring detection. FIG. 7 is a diagram for explaining a first modification of scoring detection performed by the induction heating cooker of FIG. 1. When a cooking operation is detected at time Time7, instead of the third threshold Temp3b, the second threshold Temp2 is used as the burn threshold and the burn detection is continued.

  In addition, when the determination circuit 43 uses any one of the third threshold values Temp3a, Temp3b, and Temp3c as a burning threshold value, when the cooking operation is detected, instead of the third threshold value, The burn-in detection may be continued by using the fourth threshold Temp 4 larger than the second threshold Temp 2 as the burn-in threshold. When the cooking operation is detected, it is considered that the user is near the cooking container 2, so that unnecessary scoring detection can be avoided even if a scoring threshold value larger than the second threshold value is used. . However, the fourth threshold value Temp4 is set to a temperature lower than the temperature at which scorching occurs when general fried food cooking is performed. FIG. 8 is a diagram for explaining a second modified example of scoring detection performed by the induction heating cooker of FIG. 1. When a cooking operation is detected at time Time7, instead of the third threshold Temp3b, the fourth threshold Temp4 is used as the burn threshold, and the burn detection is continued.

  Hereinafter, with reference to FIG. 9 to FIG. 11, a case where burning is detected will be described. FIGS. 9-11 is a figure for demonstrating the temperature control performed by the induction heating cooking appliance of FIG. 1 when the temperature of the cooking container 2 of FIG. 1 reaches scoring detection temperature Temp2.

  As illustrated in FIG. 9, the determination circuit 43 may detect the burning by reaching a burning threshold (for example, the second threshold Temp2) and stop heating the cooking container 2 as it is.

  Further, as shown in FIG. 10, the determination circuit 43 does not stop the heating of the cooking container 2 even if it is detected that the burn-in threshold value (for example, the second threshold value Temp2) has been reached, Heating may be continued while suppressing the output power of the inverter circuit 12.

  In addition, as shown in FIG. 11, the determination circuit 43 immediately stops heating the cooking container 2 even if it is detected that the burn-in threshold value (for example, the second threshold value Temp2) has been reached. First, a fifth threshold Temp5 (for example, about 250 ° C.) larger than the burn threshold is set, and the cooking container 2 is heated when the temperature of the cooking container 2 reaches the fifth threshold Temp5. May be stopped.

  The determination circuit 43 does not stop heating the cooking container 2 even if it detects a burn due to reaching a burn threshold (for example, the second threshold Temp2), and displays the burn detection information on the display panel or Heating may be continued by notifying the user by an alarm or the like (not shown).

  In order to select the operation (FIGS. 9 to 11) when the burn is detected, the user of the induction heating cooker can set using the mode selection key 16c.

  As described above, according to the present embodiment, when scoring detection is started, the scoring threshold temperature is set based on the time measured by the timer 32 and the temperature detected by the infrared sensor 4. Since it is switched to the low temperature side, it is possible to reliably detect scorching even when cooking with low heating power (boiled food cooking) in which the bottom temperature of the cooking container 2 is difficult to rise, and prevent scorching from occurring at low temperatures. be able to.

  Also, when a cooking operation is detected, the burnt threshold value is switched to the high temperature side, so the burnt detection operation can be performed easily, such as when cooking a stir-fry or when adding moisture during steaming. I will not.

  If the temperature detected by the infrared sensor 4 does not reach the burn-in threshold when the predetermined time has elapsed during the time count by the timer 32, the time is initialized and time is measured again, and the burn-in occurs. Since the threshold value is gradually switched to the low temperature side, even when cooking at low heating power, even when the bottom surface temperature is difficult to rise due to the characteristics of the cooking container 2 (such as a large heat capacity), it is reliably detected. can do.

  In addition, since the burn-in threshold is reduced as the user selects a smaller output power for the induction heating cooker, characteristics of the cooking container (such as a large heat capacity) ), It is possible to reliably detect burning even when the pan bottom temperature is difficult to rise.

  In addition, when determining the simmered food based on the integrated power amount and the temperature detected by the infrared sensor, even when the output power fluctuates, the simmered food and the fried food cooking are determined with high accuracy. be able to.

  In addition, when scoring detection is performed, the progress of scoring can be prevented by stopping heating when the scoring threshold is reached.

  In addition, when burning detection is performed, heating is not stopped when the burning threshold is reached, heating is suppressed, or heating is continued by notifying the user of burning detection information (for example, display and notification). By doing so, the heating can be stopped based on the judgment of the user.

  In addition, when scoring is detected, heating is not stopped immediately when the scoring threshold is reached, but a fifth threshold value (for example, about 250 ° C.) greater than the scoring threshold value is detected. Then, the heating may be stopped. In this case, when cooking the grilled food directly after evaporating the moisture by steaming cooking, or when performing cooking that you want to burn, the induction will not be stopped easily by detecting the burning. Usability of the cooking device can be improved.

  In addition, according to the present embodiment, since the bottom surface temperature of the cooking container 2 is detected by the infrared sensor 4, the pan bottom temperature can be detected with higher responsiveness than when using a temperature sensitive element such as a thermistor. Burning can be accurately detected.

  Although the components 31 to 36 of the controller 17 are shown as a plurality of independent circuits in FIG. 1, the present invention is not limited to this, and may be configured by one general-purpose processor.

  As described above, according to the induction heating cooker according to the present invention, it is detected that the contents of the cooking container 2 are burnt even when the user operates to heat with the output power selected by the user. In addition, in cooking such as stir-fry cooking, the burn-in detection is not operated unnecessarily, and cooking can be performed continuously without stopping the heating. It is effective for an induction heating cooker that can set output power for home use or business use, such as a desktop type used or a stationary type used on a table.

DESCRIPTION OF SYMBOLS 1 Top plate 2 Cooking container 3 Induction heating coil 3a Outer coil 3b Inner coil 4 Infrared sensor 5 Infrared detection signal 6 Commercial power supply 7 Input current detector 8 Rectifier circuit 9 Full wave rectifier 10 Choke coil 11 Smoothing capacitor 12 Inverter circuit 13 Resonant capacitor DESCRIPTION OF SYMBOLS 14 Switching element 15 Diode 16 Operation panel 16a Heating start / end key 16b Setting key 16ba Up key 16bb Down key 16c Mode selection key 17 Controller 21 Photodiode 22 Operational amplifier 23, 24 Resistance 31 Inverter control circuit 32 Timer 33 Memory 34 Temperature calculation circuit 35 Current measurement circuit 36 Burning detection circuit 41 Integrating power meter 42 Cooking operation detection circuit 43 Determination circuit

Claims (9)

A top plate on which the cooking container is placed;
An induction heating coil provided under the top plate for heating the cooking vessel;
An inverter circuit for supplying a high-frequency current to the induction heating coil with a predetermined output power;
An infrared sensor that is provided under the top plate and that measures the temperature of the bottom of the cooking container by detecting infrared radiation emitted from the bottom of the cooking container and transmitted through the top plate;
A selection device for obtaining one output power setting value selected from a plurality of output power setting values;
In an induction heating cooker comprising: a controller that controls the inverter circuit so that the output power of the inverter circuit becomes an output power corresponding to the selected output power setting value;
The controller is
When the temperature is less than a predetermined first threshold at a predetermined time after starting the heating of the cooking container or at a time when a predetermined integrated electric energy is consumed since the heating of the cooking container is started, When the second threshold value higher than the first threshold value is used as a burn-in threshold value to start burn-in detection, and the temperature increases above the burn-in threshold value, the contents of the cooking container Detects burnt objects,
When the temperature is lowered over a predetermined temperature drop amount or when the temperature does not rise over a predetermined time, a cooking operation for the contents of the cooking container is detected,
When neither the burn-in nor the cooking operation is detected within a predetermined first time period from the start of the burn-in detection, the second threshold value is substituted for the second threshold value. An induction heating cooker characterized in that the burn detection is continued using a small third threshold as the burn threshold.   The controller starts the scoring detection when the temperature is lower than the first threshold when a predetermined second time period elapses after the cooking container starts to be heated. The induction heating cooker according to claim 1.   When the controller does not detect both the burning and the cooking operation within the first time period from the start of the burning detection, the controller replaces the second threshold value with the second threshold value. Continuing the burn detection using one of a plurality of different third thresholds less than a threshold as a burn threshold, wherein the third threshold used is the selected threshold The induction heating cooker according to claim 1, wherein the induction heating cooker increases as the output power set value increases.   The controller uses the first time period as a cycle, and repeats the scoring detection when neither the scorching nor the cooking operation is detected within each first time period. The induction heating cooker according to any one of claims 1 to 3.   When the controller does not detect both the burning and the cooking operation within each first time period, the controller replaces the second threshold value and has a plurality of different values smaller than the second threshold value. Repeating the burn detection using one of the third thresholds as the burn threshold, and the third threshold used is repeated each time the burn detection is repeated. It decreases, The induction heating cooking appliance of Claim 4 characterized by the above-mentioned.   When the controller uses the third threshold value as a burn-in threshold value, when the cooking operation is detected, the controller uses the second threshold value or the second threshold value instead of the third threshold value. The induction heating cooking according to any one of claims 1 to 5, wherein the burn detection is continued using a fourth threshold value larger than the second threshold value as the burn threshold value. vessel.   The induction heating cooker according to any one of claims 1 to 6, wherein when the controller detects the burn, the controller stops heating the cooking container.   The induction heating cooker according to any one of claims 1 to 6, wherein the controller reduces the output power of the inverter circuit when the burn is detected.   When the controller detects the burn, the controller continues the burn detection using a fifth threshold value higher than the second threshold value instead of the second threshold value, and the temperature The induction heating cooker according to any one of claims 1 to 6, wherein heating of the cooking container is stopped when the value increases to the fifth threshold value or more.

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