JP4134971B2 - Induction heating cooker - Google Patents

Description

The present invention relates to an induction heating cooker that determines warpage of the bottom surface of an object to be heated at the start of heating.

Conventionally, as this type of induction heating cooker, there is one in which a plurality of temperature detecting means are arranged on the lower surface of the top plate (see, for example, Patent Document 1).

FIG. 7 shows a cross-sectional view of a conventional induction heating cooker described in Patent Document 1. As shown in FIG. In FIG. 7, the object to be heated 24 is a cooking utensil such as a pan or a frying pan. Into the object to be heated 24, ingredients not shown are placed and heated directly or indirectly from the cooking heater 25 to be heated. The ingredients in 24 are heated and cooked. The cooking heater 25 includes a top plate 26, a plurality of temperature sensors (temperature detection means) 27 a, 27 b, 27 c, 27 d, heating sources 28 a, 28 b, and the like, and an object to be heated 24 placed on the top plate 26. The temperature of the object to be heated 24 is measured from the temperature detected by the temperature sensor 27a, and the food in the object to be heated 24 is cooked by performing heating control. The top plate 26 is made of glass or the like, and is used for placing the object 24 to be heated. The temperature sensors 27a, 27b, 27c, and 27d measure the temperature of the object to be heated 24. The heating sources 28 and 28b are for heating the article 24 to be heated.

  When the difference between the measured value of the temperature sensor 27a arranged in the vicinity of the center and the measured values of the other temperature sensors 27b, 27c, 27d is equal to or larger than the reference value, as shown in the temperature sensor arrangement of FIG. If the object to be heated is warped, the center of the pan bottom will rise and the heating efficiency will be worse compared to the surroundings of the floating pan. For example, the coupling with the heating coils that are the heating sources 28a and 28b will deteriorate, and the difference in measurement temperature will increase. It can be determined that the bottom of the heated object 24 has warp. In the case of a pan bottom with a warp, it was determined and reflected in control such as applying correction to the error occurring in the measured temperature of the object 24 to be heated.

  In addition, there is one that determines and corrects that a loaded fried food material has been introduced (see, for example, Patent Document 2).

  FIG. 9 shows a block diagram of a conventional cooking device described in Patent Document 2. As shown in FIG. In FIG. 8, a commercial power source is supplied from a commercial AC power source 29, the induction heating device 30 is composed of a high frequency power source 30a and a heating coil 30b, and a load pan 31 is a ceramic plate 32 installed on the upper surface of the heating coil 30b. Is placed on top. The temperature detection means 33 measures the temperature by changing the resistance value of the thermistor 34 a of the temperature detection element provided so as to be in contact with the lower surface of the ceramic plate 32.

FIG. 10 is a diagram showing the behavior of the thermistor (temperature sensor) 34a of the cooking device according to the conventional example described in Patent Document 2. In FIG. The actual oil temperature indicated by (1) is lowered, and the actually detected thermistor 34a detection temperature indicated by the solid line is delayed. Here, the temperature detected by the thermistor 34a begins to decrease after the temperature of the pot 31 decreases and the temperature of the ceramic plate 32 decreases after the oil temperature decreases. When the temperature measured by the temperature detection means 33 falls below the determination temperature θ2 within the determination time T1, it is determined by the temperature control means 34b that the fried food material has been added, and the control temperature is increased from S0 to S1. It was a thing.
JP 2004-164882 A JP-A-6-140140

  However, in the case of the conventional configuration and Patent Document 1, when the temperature of the object to be heated 24 is lowered due to the input of a load such as cooked food, the detected temperatures of the temperature sensors 27a, 27b, 27c, and 27d are drastically lowered. However, the difference between the temperature sensor 27a and the measured values of the other temperature sensors 27b, 27c, and 27d becomes small, and if there is a warp, it is erroneously determined that it is not warped, or the difference becomes large and warps. When there is no, there was a problem that it was determined that it was warped by mistake.

  In the case of Patent Document 2, the thermistor 34a is configured to detect the temperature of the pan 31 at one point. This is effective when the type of the pan 31 is limited, but the temperature change amount of the thermistor 34a differs depending on the temperature distribution and shape of the pan. Had the problem of detecting.

  Moreover, when the threshold value of the overheat prevention means is switched using the result of determining the bottom surface warpage of the object to be heated, there is a problem in that there is a reduction in cooking performance if the presence or absence of warpage is erroneously determined.

The induction heating cooker of the present invention solves the above-described conventional problems. Even when a load is applied during the bottom warpage determination of an object to be heated, the warp is accurately detected, and the overheating is detected based on the detection result. The purpose is to secure cooking performance and safety by switching the threshold of the ascent prevention means.

In order to solve the conventional problem, the induction heating cooker of the present invention includes a first temperature detecting means for detecting the temperature of the bottom surface of the object to be heated via the top plate and a distance from the center of the heating coil. a second temperature detecting means for detecting the temperature of the bottom surface of the first of the top plate an object to be heated via disposed on an outer circumferential side of the heating coil distant from the temperature detecting means, said first temperature sensing A first change amount detecting means for detecting a first change amount of the temperature detected by the means with respect to time; a temperature detected by the first temperature detecting means; and a temperature detected by the second temperature detecting means. a temperature difference detecting means for obtaining a temperature difference, the temperature difference time exceeds a predetermined temperature difference from the base Hazuki start of heating is there warpage larger than within value, if no warpage predetermined time a predetermined time and judged to the Check the amount of warpage of the bottom of the heated object A first warp detecting operation for performing the warp detecting operation, and an overtemperature that stops heating or lowers the heating output when the temperature detected by the first temperature detecting means is equal to or higher than the first temperature. And a first temperature switching unit configured to switch the first temperature low when it is determined that there is a warp based on a warp amount detected by the first warp detection operation. The means detects the temperature detected by the first temperature detecting means within a predetermined time 1 after the first warp detection operation is determined to be warped during detection of the warp amount and after the first warp detection operation is completed. When the threshold value is 4 or more, when the first change amount falls below a predetermined threshold value 1, a re-warp detection operation is performed to detect a warp amount based on the magnitude of the first change amount, and the re-warp detection operation is detected. Switching the first temperature based on the result Thus, even when a load is applied during the first warp determination operation and the temperature difference that is a parameter of the first warp determination operation is affected, the accurate warp amount can be determined. The temperature can be switched correctly.

The induction heating cooker of the present invention detects that a load has been applied while detecting the amount of warping of the bottom of the object to be heated, and again determines the amount of warping. Thus, by detecting the case where the environments are different and performing different warp amount determination operations, it is possible to accurately determine the warp amount. And in order to change the control temperature of the overheat prevention means based on the detected accurate warpage amount, in a pan with a large warpage amount, the control temperature is lowered to ensure safety, and in a pan with a small warpage amount, High control temperature can be maintained to maintain high heat power cooking.

A first invention includes a top plate on which an object to be heated is placed, a heating means for heating the object to be heated, a heating coil constituting the heating means disposed below the top plate, and the top plate. a first temperature detecting means for detecting the temperature of the bottom surface of the heated object through the distance from the heating coil center is disposed on the outer periphery of the heating coil farther than said first temperature sensing means Second temperature detecting means for detecting the temperature of the bottom surface of the object to be heated via the top plate, and first change for detecting a first change amount with respect to time of temperature detected by the first temperature detecting means. A quantity detection means, a temperature difference detection means for obtaining a temperature difference between the temperature detected by the first temperature detection means and the temperature detected by the second temperature detection means, and a predetermined time from the start of heating based on the temperature difference . Time exceeding temperature difference It is determined that there is warpage larger than the warp without predetermined time if it is within a predetermined time the first and the warp detection operation for warpage detection operation for detecting the amount of warpage of the object to be heated bottom, the first temperature sensing When the temperature detected by the means is equal to or higher than the first temperature, the temperature of the object to be heated is stopped or the heating output is reduced, and the temperature rise prevention means, and the amount of warpage detected by the first warpage detection operation causes warpage. And a first temperature switching unit that switches the first temperature to a low level, and the first temperature switching unit warps during detection of the amount of warp in the first warp detection operation. after determination, and if the first change amount if the predetermined threshold value 4 or more temperature the detection to the first of said first temperature sensing means of the warp detection operation ends after a predetermined time within 1 falls below a predetermined threshold value 1, The amount of warpage is determined by the magnitude of the first change amount. And re-warp detecting operation of knowledge, the by the switching between the first temperature based on the detection result of the re-warped detection operation, the first load in the warp determination operation is turned, the first even if you are affected before Symbol temperature difference as a parameter of the warp determining operation, it enables determination of the exact amount of warpage, by performing the switching of the first temperature correctly, ensuring both the cooking performance and safety To do.

  In addition, it is possible to determine the amount of warping when a load is applied, and to ensure both cooking performance and safety by correctly switching the first temperature.

  In addition, if the temperature detected by the first temperature detection means within the predetermined time 1 is equal to or higher than the predetermined threshold value 4, the re-warp detection operation is performed by performing the re-warp detection operation so that a load is applied. In an environment where the detection operation is hardly affected, only the first warp detection operation is performed.

  In addition, if the amount of warpage detected by the first warpage detection operation is equal to or greater than a predetermined amount, the amount of warpage detected by the first warpage detection operation is determined by performing the rewarpage detection operation. The re-warping detection operation is performed only when erroneous detection is performed.

According to a second aspect of the present invention, there is provided a top plate on which an object to be heated is placed, a heating means for heating the object to be heated, a heating coil constituting the heating means disposed below the top plate, and the top plate. a first temperature detecting means for detecting the temperature of the bottom surface of the heated object through the distance from the heating coil center is disposed on the outer periphery of the heating coil farther than said first temperature sensing means The temperature difference between the temperature detected by the second temperature detecting means for detecting the temperature of the bottom surface of the object to be heated via the top plate, the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means. A temperature difference detecting means for obtaining a warpage, and if the time exceeding a predetermined temperature difference from the start of heating based on the temperature difference is within a predetermined time, it is determined that there is a warp if there is no warp and greater than a predetermined time . Detect the amount of warping A first warp detecting operation for performing a warp detecting operation, and an excessive temperature rise that stops heating or lowers the heating output when the temperature detected by the first temperature detecting means is equal to or higher than the first temperature. And a temperature detected by the temperature difference detecting means, a first temperature switching means for switching the first temperature low when it is determined that there is a warp based on the amount of warpage detected by the first warp detecting operation. and a third change amount detecting means for detecting the amount of change over time of the difference, the first temperature switching means, after the determination that there is warping in detecting the amount of warpage in the first warp detection operation, and if the third amount of change if the temperature difference is a predetermined threshold value 6 or more detection to the temperature difference detecting means in the first warp detection operation ends after a predetermined time 3 falls below a predetermined threshold value 3, the third detecting the amount of warpage by the variation in size By performing a warp detection operation and switching the first temperature based on the detection result of the re-warp detection operation, the load application is detected without being affected by the amount and position of the load to be applied. The warpage amount can be determined again. Thus, the first of the load in warp determination operation is turned, even if there is influence before Symbol temperature difference as a parameter of the first warp determination operation, by re-warp detecting operation, accurate warpage It is possible to determine both of the cooking performance and safety by correctly switching the first temperature and controlling the heating.

  In addition, it is possible to determine the amount of warping when a load is applied, and to ensure both cooking performance and safety by correctly switching the first temperature.

  Further, if the temperature difference detected by the temperature difference detection means within the predetermined time 3 is equal to or greater than the predetermined threshold value 6, the first warp detection operation is affected by the application of a load by performing the re-warpage detection operation. In a difficult environment, only the first warp detection operation is performed.

  In addition, if the amount of warpage detected by the first warpage detection operation is equal to or greater than a predetermined amount, the amount of warpage detected by the first warpage detection operation is determined by performing the rewarpage detection operation. The re-warping detection operation is performed only when erroneous detection is performed.

In the third aspect of the invention, in particular, the first temperature switching means of the first or second aspect of the invention performs the re-warp detection operation for a predetermined time 4 so that the influence of the load application is eliminated after the predetermined time elapses. In the case of the failure, the re-warp detection operation is not performed.

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

(Embodiment 1)
FIG. 1 is a block diagram showing an induction heating cooker according to the first embodiment of the present invention. In FIG. 1, an induction heating device 2 is an induction heating device comprising a heating power control means 2a, a high frequency current source 2b, and a heating coil 2c for supplying a commercial AC power source 1 after converting it into a high frequency current. It is placed on the top plate 4 installed on the upper surface of the coil 2c.

  The first temperature detecting means 5 measures the temperature by changing the resistance value of the first thermistor 5 a of the temperature detecting element provided so as to be in contact with the lower surface of the top plate 4. The second temperature detection means 6 is provided so as to be in contact with the lower surface of the top plate 4, and the second thermistor 6a of the temperature detection element provided on the outer peripheral side of the heating coil 2c as compared with the first thermistor 5a. The temperature is measured by changing the resistance value.

  The temperature difference detection means 7 detects the temperature difference between the temperature detected by the first temperature detection means 5 and the temperature detected by the second temperature detection means 6. The first warpage detection means 8 is the temperature difference detection means 7. Based on the detected temperature difference, the amount of warpage of the bottom surface of the article to be heated 3 is detected.

  The first change amount detection means 9 detects the change amount of the temperature detected by the first temperature detection means 5 at the time Δt, and the second change amount detection means 10 detects the second temperature detection means 6. The third change amount detection means 11 for detecting the change amount of the temperature at the time Δt detects the change amount of the temperature difference detected by the temperature difference detection means 7 at the time Δt.

  The re-warp detection operation 12 detects the amount of bottom warp of the article 3 to be heated again after the first warp detection operation 8 is completed.

  The overheat prevention means 13 stops heating the object to be heated 3 based on the first detection temperature 15 detected by the first temperature detection means 5 or reduces the output of the heating. When the predetermined first temperature is exceeded, a signal for reducing the heating output is transmitted to the thermal power control means 2a. The first temperature switching means 14 switches the first temperature based on the detection result of the first warpage detection operation 8 or the re-warpage detection operation 12.

  FIG. 2 is a diagram showing the behavior of the first and second temperature detecting means when the warp of the pan is small, and represents the time transition of the detected temperature.

  In FIG. 2, the temperature transition 15 is detected by the first temperature detection means 5 and the temperature transition 16 is detected by the second temperature detection means 6 when the pan bottom warpage amount of the object to be heated is small. The first detected temperature and the temperature transition 17 represent the time transition of the temperature difference between the first detected temperature and the second detected temperature detected by the temperature difference detecting means 7.

  FIG. 3 is a diagram showing the behavior of the temperature detection means when the pan warpage is large. In FIG. 3, the temperature transition 18 in the case where the pan bottom warpage amount of the article to be heated 3 is large is the first temperature detection means 5. Is detected by the second temperature detecting means 6, and the temperature change 20 is detected by the temperature difference detecting means 7 and the second detected temperature. It represents the time transition of the temperature difference from the detected temperature.

  The operation | movement is demonstrated below about the induction heating cooking appliance which is a heating cooking appliance shown in FIG. 1, FIG.

  The thermal power control means 2a controls the output of the high frequency current source 2b so as to heat the article 3 to be heated with the thermal power corresponding to the set thermal power, and supplies the high frequency current to the heating coil 2c.

  The first temperature detection means 5 detects the bottom surface temperature of the article to be heated 3 propagated through the top plate 4 as the first detection temperature 15. The second temperature detection means 6 detects the bottom temperature of the heated object 3 on the outer peripheral side of the heating coil 2 c as the second detection temperature 16 from the first temperature detection means 5.

  In FIG. 2, when the object to be heated 3 without warping (substantially flat) is heated, the second detected temperature transition 16 starts to rise immediately after heating, and then the first detected temperature transition 15 rises. start. At this time, the temperature difference transition 17 becomes minimum at tb and then increases.

  In the first warpage determination operation, the warpage determination operation is started from the heating start time t0, and the time ts when the temperature difference transition 17 exceeds a predetermined temperature difference threshold Te1 (+ 1 ° C. in this embodiment) is a predetermined time. If it is within the threshold value tsh1 (40 s to 80 s in this embodiment), it is determined that there is no warp.

  As shown in FIG. 3, when the object to be heated 3 having a concave warp (inward warp) on the bottom surface is heated, the second detected temperature transition 19 rises regardless of the warp, but the first detected temperature transition 18 is Due to the warping of the bottom surface, the temperature followability is worse than that of the heated object 3 without warping, so the time for starting to rise is delayed. Due to this influence, ts of the temperature difference transition 20 becomes larger than tsh1. From this result, it is determined that the pan bottom of the article to be heated 3 is warped (the warp is large if the difference is large due to the time difference).

  The first warp detection operation 8 is performed from t0 to tsh1.

  If it is determined that there is a warp (2 mm or more in the present embodiment) from the above-described warp detection results, the first temperature switching means 14 sets the first temperature low. When the first detected temperature transition 15 or 18 exceeds the first temperature, the overheat prevention means 13 requests the thermal power control means 2a to lower the thermal power by one level from the current thermal power.

However, even when heating an object 3 with no Ri凹反the pan bottom, as shown in diagram illustrating the behavior (time transition) of the temperature detecting means at the time of re-warp detecting transition of FIG. 4, first at the start of pressurization heat 1 When the detected temperature transition 21 is equal to or higher than the predetermined temperature Tt at the start (155 ° C. in the present embodiment), the first detected temperature transition 21 hardly increases, and a load is applied during the first warpage determination. Then, it will fall under the influence. For this reason, the temperature difference transition 23 does not increase even if it exceeds tsh1, and it is determined that there is a warp.

  Therefore, if it is determined that there is a warp in the first warp determination operation and the first detected temperature transition 21 at the start of heating is equal to or higher than the predetermined temperature Tt at the start, the first warp determination is completed, and then the first When the change amount θ1 at the time Δt detected by the change amount detection means becomes equal to or less than a predetermined threshold value Ts2 (−2 ° C. in this embodiment), the re-warp detection operation 12 is performed.

  The re-warpage detection operation 12 is performed from tsh1 to tsh2 (in this embodiment, tsh1 + 20s).

  In the re-warp detection operation 12, the warp amount of the pan bottom of the article 3 to be heated is determined by the magnitude of θ1, and the first temperature switching means 14 determines the first temperature corresponding to the warp amount.

  The warpage detection operation can be switched between when the load is applied and when the load is not detected by detecting the input of the load based on the time change amount of the first detected temperature. When the load is applied during the first warpage detection and the first detection temperature is lowered, the pan bottom warpage amount of the object to be heated 3 is detected by the re-warpage detection operation 12 to be erroneously detected due to the effect of the load application. This makes it possible to accurately determine the amount of warp.

(Embodiment 2)
The configuration of the induction heating cooker of the second embodiment is the same as that of the first embodiment, and the description thereof is omitted. FIG. 5 is a block diagram showing an induction heating cooker according to the second embodiment of the present invention. In FIG. 5, the second change amount detection means 10 detects the change amount θ2 of the temperature detected by the second temperature detection means 6 in the Δt time, and the third change amount detection means 11 detects the temperature difference detection means 7. The amount of change θ3 in the Δt time of the detected temperature difference is detected.

  When a load is applied during the first warp detection operation 8, the bottom surface temperature of the article 3 to be heated decreases, and both the first detection temperature 21 and the second detection temperature 22 decrease. Therefore, as shown in the diagram showing the behavior (time transition) of the temperature detection means at the time of transition to re-warp detection in FIG. 6, it is determined that there is warp in the first warp detection operation 8, and the second at the start of heating. If the detected temperature transition 22 is equal to or higher than a predetermined temperature Tt2 (155 ° C. in the present embodiment) at the start, the change amount θ2 detected by the second change amount detecting means after the first warp detection operation 8 is completed. When the predetermined threshold value Ts2 or less is reached, a re-warp detection operation 12 is performed. The rewarping detection operation 12 is performed from tsh1 to tsh2.

  In the re-warp detection operation 12, the warp amount of the pan bottom of the article 3 to be heated is determined by the magnitude of θ2, and the first temperature switching means 14 determines the first temperature according to the warp amount.

  Alternatively, if it is determined that there is a warp in the first warp detection operation 8 and the temperature difference 23 at the start of heating is equal to or greater than the predetermined temperature Tt3 at the start, after the first warp detection operation 8 ends, When the change amount θ3 detected by the change amount detection means 11 is equal to or less than a predetermined threshold value Ts3, a re-warp detection operation 12 is performed. The rewarping detection operation 12 is performed from tsh1 to tsh2.

  In the re-warp detection operation 12, the warp amount of the pan bottom of the article 3 to be heated is determined according to the magnitude of θ3, and the first temperature switching means 14 determines the first temperature according to the warp amount.

  When detecting the load application, by using the time change amount θ2 of the second detection temperature 22 or the time change amount θ3 of the temperature difference 23, the load input is not affected by the amount and position of the input load. Can be detected. Based on the detection result, the warp detection operation can be switched between when the load is applied and when the load is not applied. When the load is applied during the first warpage detection and the first detection temperature is lowered, the pan bottom warpage amount of the object to be heated 3 is detected by the re-warpage detection operation 12 to be erroneously detected due to the effect of the load application. This makes it possible to accurately determine the amount of warp.

  In general, the temperature followability of the temperature detection means varies depending on the detection means due to differences in configuration. In the present embodiment, even if the temperature followability of the first temperature detecting means 5 and the second temperature detecting means 6 is reversed, for example, the case where the center of the article 3 to be heated is inwardly warped and In the case of a convex warp, the effect of the present invention can be obtained.

In the above embodiment, not intended to be limited to the thermistor with respect to temperature sensing means. In addition, the threshold used for the determination and the sampling interval for obtaining the temperature difference increase are not unique and must be designed for each device.

Further, in the above embodiment, the first warp detection operation 8, it is detecting the Ri凹反re warp detection operation 12 both bottom.

  Furthermore, in the above embodiment, the first warpage detection operation detects the presence or absence of warpage using one threshold value tsh1 based on the detected amount of warpage, and switches the first temperature based on the detection result. Based on the detected amount of warpage, a plurality of warpage levels are set, and a first temperature is set according to the warpage of the bottom of the article 3 to be heated by switching the first temperature according to each level. Heating operation can be performed with the optimum heating power for the warp level.

  Similarly, when a plurality of warp levels are set according to the warp amount detected in the re-warp detection operation, and the first temperature corresponding to each warp level is set, the heating operation can be performed with the optimum thermal power for each warp level. it can.

As described above, the induction heating cooker according to the present invention determines the warpage of the bottom surface of the object to be heated regardless of the type of pan or the contents. It can be applied to uses such as cooking equipment that performs normal cooking such as cooking and boiled food, automatic cooking, and the like.

The block diagram which shows the induction heating cooking appliance in Embodiment 1 of this invention The figure which shows the behavior of the temperature detection means in case the curvature of the pan in Embodiment 1, 2 of this invention is small. The figure which shows the behavior of the temperature detection means in case the curvature of the pan in Embodiment 1, 2 of this invention is large. The figure which shows the behavior of the temperature detection means at the time of re-warping detection transfer in Embodiment 1, 2 of this invention. The block diagram which shows the induction heating cooking appliance in Embodiment 2 of this invention The figure which shows the behavior of the temperature detection means at the time of re-warping detection transfer in Embodiment 2 of this invention. Cross-sectional view of an induction heating cooker in a conventional example Temperature sensor layout diagram of induction heating cooker in the conventional example Block diagram of induction heating cooker in the conventional example The figure which shows the behavior of the temperature sensor of the induction heating cooking appliance in a prior art example

Explanation of symbols

2a Thermal power control means (heating means)
2b High-frequency current source (heating means)
2c Heating coil (heating means)
Reference Signs List 3 Heated object 4 Top plate 5 First temperature detection means 6 Second temperature detection means 7 Temperature difference detection means 8 First warp detection operation 9 First change amount detection means 10 Second change amount detection means 11 Third change amount detection means 12 Re-warp detection operation 13 Overtemperature prevention means 14 First temperature switching means

Claims (3)

A top plate for placing the object to be heated, a heating means for heating the object to be heated, a heating coil constituting the heating means disposed below the top plate, and the object to be heated via the top plate First temperature detecting means for detecting the temperature of the bottom surface of the heating coil, and the top plate disposed on the outer peripheral side of the heating coil at a distance from the center of the heating coil farther from the first temperature detecting means. a second temperature detecting means for detecting the temperature of the bottom surface of the object to be heated, a first change amount detecting means for detecting a first change amount over time of the detected temperature of the first temperature sensing means, Temperature difference detecting means for obtaining a temperature difference between the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means; and a time exceeding a predetermined temperature difference from the start of heating based on the temperature difference. When The first and warpage detection operation, the first temperature detection means for performing a warping detection operation for detecting the amount of warpage of less value, if there warpage larger than a predetermined time without warping the determination to the object to be heated bottom When the temperature to be detected is equal to or higher than the first temperature, it is determined that there is a warp based on the temperature rise prevention means for stopping the heating of the object to be heated or reducing the heating output, and the warp amount detected by the first warp detection operation. And a first temperature switching unit that switches the first temperature to a low level when the first temperature switching unit determines that there is a warp during detection of the warp amount in the first warp detection operation. and when the first change amount if the temperature is a predetermined threshold value 4 or more detection for the first temperature detection means in the first warp detection operation ends after a predetermined time within 1 falls below a predetermined threshold value 1, the The amount of warpage is detected by the magnitude of the first change amount. That re-warping performs detection operation, the induction heating cooker switches the first temperature based on the detection result of the re-warped detection operation. A top plate for placing the object to be heated, a heating means for heating the object to be heated, a heating coil constituting the heating means disposed below the top plate, and the object to be heated via the top plate First temperature detecting means for detecting the temperature of the bottom surface of the heating coil, and the top plate disposed on the outer peripheral side of the heating coil at a distance from the center of the heating coil farther from the first temperature detecting means. Second temperature detection means for detecting the temperature of the bottom surface of the object to be heated, and temperature difference detection for obtaining a temperature difference between the temperature detected by the first temperature detection means and the temperature detected by the second temperature detection means Based on the temperature difference, if the time exceeding the predetermined temperature difference from the start of heating is within the predetermined time, no warpage is detected. Warping A first warp detecting operation for performing an intelligent operation, and an excessive temperature rise that stops heating or lowers the heating output when the temperature detected by the first temperature detecting means is equal to or higher than the first temperature. And a temperature detected by the temperature difference detecting means, a first temperature switching means for switching the first temperature low when it is determined that there is a warp based on the amount of warpage detected by the first warp detecting operation. And a third change amount detecting means for detecting a third change amount with respect to the elapsed time of the difference, wherein the first temperature switching means is warped during detection of the warp amount in the first warp detecting operation. If the temperature difference detected by the temperature difference detection means within the predetermined time 3 after the determination and the first warp detection operation ends is greater than or equal to a predetermined threshold 6, the third change amount falls below the predetermined threshold 3, The amount of warpage is detected by the magnitude of the third change amount. That re-warping performs detection operation, the induction heating cooker switches the first temperature based on the detection result of the re-warped detection operation. The induction heating cooker according to claim 1 or 2 , wherein the first temperature switching means performs a re-warp detection operation for a predetermined time 4 only.

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