JP5523606B2 - Cooker - Google Patents

Description

  The present invention relates to a cooking device capable of detecting the temperature of an object to be heated placed on a top plate.

  As a method of detecting the temperature of the pan, which is the object to be heated, placed on the top plate of the cooking device, a thermistor, which is a contact temperature sensor, is brought into contact with the top plate and transmitted from the pan through the top plate. There are a thermistor method for detecting the temperature to be detected and an infrared sensor method for detecting the infrared radiation energy radiated from the pan in a non-contact manner through the top plate.

  In the thermistor method, the thermistor is brought into close contact with the lower surface of the top plate, and the temperature of the pan is detected by the thermistor through the top plate. For this reason, the temperature of the pan is not directly transmitted to the thermistor, and there is a problem that the followability of the temperature detection of the thermistor to the temperature change of the pan is poor.

  In addition, the infrared sensor system has an infrared sensor disposed below the central space of the heating coil and the space between the inner coil and the outer coil, and the infrared radiation energy radiated from the pan placed on the top plate is spatially transmitted. The temperature of the pan is detected by the amount of energy.

  Unlike the thermistor method, this infrared sensor method does not cause a follow-up problem between the temperature of the pan and the detection value of the infrared sensor, but the detection accuracy is affected by the difference in the color of the pan bottom. That is, since the emissivity from the infrared radiation surface varies depending on the color of the pan bottom, the amount of infrared radiation energy radiated from the pan may differ even if the pan temperature is the same. For this reason, even if the temperature of a pan is actually the same, there exists a problem measured as different temperature.

  The top plate itself is also heated by heat conduction from the heated pan. For this reason, an infrared sensor will also detect the infrared rays radiated | emitted from a top plate. Therefore, the more the top plate is heated, the more difficult it is to accurately detect the temperature of the pan desired to be acquired. If the temperature of the pan cannot be accurately detected and the pan is heated excessively, for example, if it is a pan for frying, the oil in the pan will be at a high temperature, and the pan will be empty. If the pan is baked, there is a risk of problems such as deformation and breakage of the fluorine coating.

  Therefore, for the purpose of more accurately detecting the temperature of the pan, as shown in Patent Document 1, as shown in Patent Document 1, as shown in Patent Document 1, a band-pass filter that transmits light of a predetermined band wavelength to the light receiving surface of the infrared sensor. There is a heating cooker configured to cut infrared rays and disturbance light radiated from the top plate itself, which becomes a measurement error. In this cooking device, the reflectance of the pan is measured and the emissivity is calculated from the reflectance, and the infrared radiation energy from the pan detected by the infrared sensor through the bandpass filter is measured. The pan temperature is calculated from the value of the radiant energy.

  Further, as shown in Patent Document 2, a correspondence relationship between the temperature of the top plate and the infrared radiation energy radiated from the top plate is obtained in advance, and from the infrared radiation energy detected by the infrared sensor, a contact-type temperature sensor is used. By removing the infrared radiant energy corresponding to the detected temperature of the top plate, the infrared radiant energy radiated from the pan is obtained, and this infrared radiant energy is converted into temperature to estimate the temperature of the pan. is there.

  Moreover, as shown in Patent Document 3, “the infrared sensor 4 outputs an infrared detection signal 25a when the bottom surface temperature of the cooking container 2 is about 140 to 200 ° C., and when the bottom surface temperature is about 200 to 250 ° C. The infrared detection signal 25b is output, and the infrared detection signal 25c is output when the bottom surface temperature is about 250 to 330 ° C. The infrared sensor 4 is infrared when the bottom surface temperature of the cooking container 2 is less than about 140 ° C. There is a cooking device configured such that the detection signal 25 is not output.

Japanese Patent No. 4123036 (pages 4 to 6) JP 2011-34743 A (pages 7 and 8) JP 2010-282860 A (page 9, FIG. 4)

  The invention disclosed in Patent Document 1 removes infrared rays radiated from the top plate itself when measuring infrared radiation energy with a band-pass filter. The bandpass filter has a transmission wavelength range of 0.76 μm to 3 μm, and this wavelength range indicates a range in which the transmission ratio of infrared rays emitted from the top plate is small.

However, the transmission wavelength of 0.76 to 3 μm of the band-pass filter has a small transmission rate of infrared rays emitted from the top plate, but does not pass through the band-pass filter unless the infrared energy emitted from the pan also becomes high temperature. Therefore, for example, in the temperature range of 180 ° C., it is necessary to increase the amplification factor of the output of the infrared sensor, and there is a problem that the detection value is not stable due to the influence of electromagnetic noise and emissivity.
In addition, although the proportion of radiation from the top plate received by the infrared sensor by the bandpass filter is small, the temperature of the top plate rises as the pan is heated, and the infrared sensor detects the top plate itself. It also receives infrared radiant energy emitted by. Therefore, in order to extract only the infrared rays from the pan, the infrared radiation energy from the top plate must be removed from the output of the infrared sensor.

  For this reason, in Patent Document 2, the emissivity of the pan is estimated based on the rate of temperature rise and the reflectance of the pan at the same time of the infrared sensor and the top thermistor, and from the amount of infrared radiation energy output from the infrared sensor, The amount of infrared radiant energy emitted from the top plate is subtracted, and the subtracted value is multiplied by the emissivity.

However, when the pan is warped and a part of the pan bottom is floating, there is an air layer between the top plate and the pan bottom, and the infrared rays emitted from the pan bottom are attenuated before reaching the top plate. . Therefore, the temperature increase rate of the top plate is different depending on whether the bottom of the pan is floating from the top plate or not. For this reason, in the configurations of Patent Document 2 and Patent Document 3, it is difficult to subtract the influence of the top plate from the amount of infrared radiation energy detected by the infrared sensor. Moreover, since the rate of temperature rise of the top plate and the rate of temperature rise of the infrared sensor differ depending on the amount of the pan floating or warping, the emissivity may be set erroneously. Thus, there existed a subject about the accuracy of the temperature of the detected pan.
Further, the energy calculation becomes a fourth power calculation formula for the output temperature as shown by the Stefan-Boltzmann formula, and the calculation load increases.

  Moreover, in patent document 3, it is the structure which can detect only after the infrared rays radiated | emitted from a pan are received by an infrared sensor, without considering the influence of the emissivity of a pan, and a high sensitivity is requested | required of an infrared sensor. Therefore, it becomes high cost. Moreover, in order not to receive the radiation influence of a top plate, it is comprised so that an infrared sensor may detect infrared rays with a wavelength of 3.0 micrometers or less, and it is about 80 degreeC-about 140 degreeC used for a kettle and cooking. There was a problem that the sensitivity of the infrared sensor was very low for infrared rays from the pan in the temperature range.

  As described above, in the techniques described in Patent Documents 1 to 3, a device for improving the accuracy of detecting the temperature of the pan is made, but there remains a problem with respect to the accuracy. If the temperature of the pan is mistakenly determined, the pan may be excessively heated to increase the temperature, but the heating control in such a case has not been studied.

  This invention is made | formed against the background as mentioned above, and provides the heating cooker which can perform the heating control which suppresses the excessive high temperature of a to-be-heated material.

  The heating cooker according to the present invention includes a top plate on which an object to be heated is placed, a heating unit disposed under the top plate, an operation unit for setting a target temperature of the object to be heated, and the top plate An infrared sensor that detects infrared rays emitted from above, an infrared temperature detection means that converts the output value of the infrared sensor into a temperature, a top plate temperature detection means that detects the temperature of the top plate, A calculation based on the detection results of the infrared temperature detection means and the top plate temperature detection means, a control means for controlling the heating means based on the calculation results, and a constant heating power after starting heating by the heating means. Based on the amount of increase in the output value of the top plate temperature detecting means when it is put for a predetermined time, the surface of the top plate and the heated object A gap distance calculation unit that calculates a gap distance that is a distance between the surface and the control means, from the infrared temperature correction value obtained by multiplying the output value of the infrared temperature detection means by a first correction coefficient, Heated object temperature estimation processing for estimating the first heated object temperature by subtracting the top plate temperature correction value obtained by multiplying the output value of the top plate temperature detecting means by the second correction coefficient, and the infrared temperature detection The second heated object temperature is estimated by subtracting the top plate temperature correction value from the infrared temperature correction value obtained by multiplying the output value of the means by the third correction coefficient that is larger than the first correction coefficient. Overheating suppression temperature estimation processing is performed, and the first heated object temperature is set to a heated object target value that is the temperature of the heated object corresponding to the target temperature set by the operating means. In When the heating means is controlled and the second heated object temperature exceeds a first overheating suppression threshold value that is higher than the preset heated object target value, heating by the heating means is performed. Or at least one of the first correction coefficient and the second correction coefficient is selected from prestored values according to the gap distance.

  According to the heating cooker of the present invention, the object temperature estimation process and the overheating suppression temperature estimation process as described above are executed in parallel, and the heating means is determined based on the result of the object temperature estimation process. On the other hand, when the result of the overheating suppression temperature estimation process exceeds the first overheating suppression threshold, heating is stopped or the heating power is reduced. For this reason, the heating control which suppresses the excessive high temperature of a to-be-heated material can be performed.

3 is a top view of the induction heating cooker according to Embodiment 1. FIG. It is a block diagram explaining the structure and function of the principal part of the induction heating cooking appliance which concerns on Embodiment 1. FIG. It is a figure explaining the structural example of the thermopile sensor which can be mounted in the induction heating cooking appliance which concerns on Embodiment 1. FIG. It is a graph which shows the permeation | transmission characteristic of the top plate of the induction heating cooking appliance which concerns on Embodiment 1. FIG. It is a graph which shows the relationship between the permeation | transmission characteristic of the top plate of the induction heating cooking appliance concerning Embodiment 1, and the spectral radiance curve in each temperature. It is a figure explaining the operation part and thermal-power display part which were provided corresponding to the left heating coil of the induction heating cooking appliance which concerns on Embodiment 1. FIG. It is a graph which shows the radiation characteristic of the top plate of the induction heating cooking appliance which concerns on Embodiment 1. FIG. 4 is a graph showing an example of transmission characteristics of a bandpass filter of the induction heating cooker according to Embodiment 1. It is an atmospheric transmission characteristic graph. It is a clearance distance level setting table of the induction heating cooking appliance which concerns on Embodiment 1. FIG. It is an emissivity setting table of the induction heating cooking appliance which concerns on Embodiment 1. It is a correction coefficient setting table based on the gap distance and emissivity of the induction heating cooker according to Embodiment 1. It is a flowchart demonstrated centering on the clearance distance determination process of the induction heating cooking appliance which concerns on Embodiment 1. FIG. It is a flowchart demonstrated centering on the emissivity determination process and heating control of the induction heating cooking appliance which concerns on Embodiment 1. FIG. It is a graph which shows an example of various temperature of the induction heating cooking appliance which concerns on Embodiment 1, and the electric power input into a heating coil. It is a correction coefficient setting table of the induction heating cooking appliance which concerns on Embodiment 2. FIG. It is a graph which shows an example of various temperature of the induction heating cooking appliance which concerns on Embodiment 2, and the electric power input into a heating coil.

  Hereinafter, a case where the heating cooker according to the present invention is applied to a built-in type (built-in type) IH cooking heater in which two heating ports by induction heating are provided on the right and left sides and one on the back side of the center will be described as an example. In addition, this invention is not limited by the form of drawing shown below. Further, in the following description, terms for indicating directions (for example, “up”, “down”, “right”, “left”, “front”, “back”, etc.) are used as appropriate for easy understanding. This is for explanation and these terms do not limit the present invention.

Embodiment 1 FIG.
[Configuration of cooking device]
1 is a top view of the induction heating cooker according to Embodiment 1. FIG.
The induction heating cooker 100 includes a main body 1 and a top plate 2 disposed on the upper surface of the main body 1, and an object to be heated such as a pan or a frying pan placed on the top plate 2 is transferred to the main body 1. Heating is performed by induction heating means provided inside. In the first embodiment, heating ports 6 are respectively provided on the left front side, the right front side, and the center side back of the top plate 2. In the following description, the object to be heated may be referred to as “pan”.

  On the upper surface of the main body 1, an operation unit 3 that receives an input operation of a heating condition or a heating instruction is arranged corresponding to each heating port 6. When a user places a pan or frying pan, which is an object to be heated, on the top plate 2 and performs an operation input on an operation key provided in the operation unit 3 corresponding to each heating port 6, induction heating is performed according to the operation input. The object to be heated is heated by the means. Information relating to settings such as the progress of heating and cooking mode is displayed on the display unit 4 having liquid crystal or the like disposed on the upper surface of the top plate 2 corresponding to each heating port 6, and the thermal power of heating is the thermal power display unit 5. Is displayed.

  Behind the main body 1, there are intake ports 9 a and 9 b that take in air for cooling the inside of the main body 1 (hereinafter, may be collectively referred to as the intake port 9), and an exhaust port 8 that exhausts air in the main body 1. Provided. When a blower (not shown) provided in the main body 1 operates, external air flows into the main body 1 from the intake port 9 as cooling air, and the cooling air causes the substrate and elements (not shown) inside the main body to be inductively heated. The heating coil 14 and the lower surface of the top plate 2 are cooled. The cooling air after cooling the inside of the main body 1 is discharged from the exhaust port 8 to the outside.

  The portion corresponding to the heating port 6 of the top plate 2 is provided with, for example, a circular display indicating a place where the pan is placed by printing or the like, so that the user can know the place where the pan should be placed. ing.

  A heating coil 14 as a heating means is provided below the heating port 6 in the main body 1. In FIG. 1, the rough arrangement of the heating coil 14 is indicated by a broken line. An eddy current is generated in the pan placed on the top plate 2 by flowing a high-frequency current through the heating coil 14, and the pan bottom itself generates heat due to the generated eddy current and the resistance of the pan itself, so the pan bottom is directly heated. Cooking with good heating efficiency can be realized. In addition, you may provide other heating means, such as an electric heater, as a heating means of the heating port 6 of the induction heating cooking appliance 100. FIG.

  In addition, a transmission window 7 having a substantially circular shape in plan view is provided inside the heating port 6 in the top plate 2. The transmissive window portion 7 is a region that has been subjected to a process that facilitates the transmission of infrared rays. For example, the top plate 2 is provided with a coating 13 for making the internal structure difficult to see from the outside (see FIG. 2), but the transmission window portion 7 is reduced in coating amount or is not coated. Etc. are applied. By doing so, infrared rays are easily received by the infrared sensor 12 (see FIG. 2), which will be described later, provided in the main body 1 through the transmission window portion 7.

FIG. 2 is a block diagram illustrating a configuration and functions of main parts of the induction heating cooker according to the first embodiment. In FIG. 2, only the structure corresponding to one heating port 6 is illustrated, and a pan 200 as an object to be heated is also illustrated.
A heating coil 14 is disposed below the heating port 6 provided in the top plate 2. In the first embodiment, the heating coil 14 has a double ring shape including a substantially annular inner heating coil 14a and a substantially annular outer heating coil 14b provided outside thereof. A substantially annular gap is provided between the inner heating coil 14 a and the outer heating coil 14 b, and this gap is referred to as a gap 15. The heating coil 14 is held at a predetermined distance from the lower surface of the top plate 2 by a heating coil support 16 that accommodates the heating coil 14.

  An infrared sensor 12 is provided in the gap 15 between the inner heating coil 14a and the outer heating coil 14b and below the upper surface of the heating coil 14 to output an output corresponding to the detected amount of infrared when detecting infrared rays. Yes. The output from the infrared sensor 12 is input to an infrared temperature detection unit 24 provided in the main body 1. The infrared temperature detector 24 calculates the temperature based on the output from the infrared sensor 12. More specifically, the storage unit 21 stores in advance a temperature conversion table in which the output amount of the infrared sensor 12 is associated with the temperature data calculated based on the output amount and a predetermined emissivity. When receiving the output from the infrared sensor 12, the infrared temperature detecting unit 24 refers to the temperature conversion table and calculates the temperature. Here, ε = 1.0 is set as an example of the emissivity ε used in the temperature conversion table.

  As the infrared sensor 12, a sensor having sensitivity in a wide wavelength with respect to an infrared region, such as a thermopile sensor, is used. Here, a configuration example of a thermopile sensor used as the infrared sensor 12 will be described.

FIG. 3 is a diagram illustrating a configuration example of a thermopile sensor that can be mounted on the induction heating cooker according to the first embodiment.
FIG. 3A shows a condensing lens type thermopile sensor (infrared sensor 12). The infrared sensor 12 shown in FIG. 3A is a package of a convex condensing lens 121 provided on the upper surface, a thermopile chip 122 and a self-temperature detection thermistor 123 provided inside. By making the condensing lens 121 convex, the field of view of the infrared sensor 12 is narrowed to suppress the influence of ambient light.

  FIG. 3B shows a built-in mirror condensing type thermopile sensor (infrared sensor 12). The infrared sensor 12 shown in FIG. 3B is a package of a flat plate 124 provided on the upper surface, a reflector 125 provided on the lower side of the flat plate 124, a thermopile chip 122, and a self-temperature detection thermistor 123. It is. The reflector 125 is for condensing infrared rays, and a mirror finish is applied to the inner peripheral surface formed so as to have a wider opening as it approaches the flat plate 124. The combination of the flat plate 124 and the reflector 125 restricts the visual field range of the infrared sensor 12 and suppresses the influence of ambient light.

  Silicon can be used as a base material for the condenser lens 121 and the flat plate 124. Silicon has a low wavelength dependency of about 50 to 60% in the infrared region, and does not absorb anything other than the transmission in the infrared region. In addition, since silicon is a material having a high thermal diffusivity, the infrared radiation from the condenser lens 121 and the flat plate 124 itself may affect the detection of the amount of infrared rays when the base material itself absorbs heat. Hateful. Further, since silicon has high thermal diffusivity, even if the condenser lens 121 and the flat plate 124 absorb infrared rays and the temperature rises, the thermal diffusion does not easily affect the detection of the amount of infrared rays. In this way, by using a silicon base material as the base material for the condenser lens 121 and the flat plate 124, the condenser lens 121 and the flat plate 124 of the infrared sensor 12 can be used even in a usage environment provided near the top plate 2. The influence on the detection of the amount of infrared rays due to the rise in temperature hardly occurs. In addition, the base material of the condensing lens 121 and the flat plate 124 is not limited to silicon, and any material having similar transmission characteristics and thermal diffusibility can be used. Further, the specific configuration of the infrared sensor 12 is not limited to that illustrated in FIG.

  The field of view 126 (see FIG. 2) of the condensing part of the infrared sensor 12 is a narrow range with respect to the opening diameter of the transmission window part 7 provided on the top plate 2. In the case of the condenser lens 121 shown in FIG. 3A, the convex curvature is set so that the detection intensity is 80% or more.

Next, the transmission characteristics of the top plate 2 and the filter provided on the condensing surface of the infrared sensor 12 will be described.
FIG. 4 is a graph showing the transmission characteristics of the top plate of the induction heating cooker according to the first embodiment. The graph of FIG. 4 shows, as an example, the transmittance τ of the top plate 2 made of crystallized glass having a thickness of about 4 mm and high heat resistance. Moreover, FIG. 5 is a graph which shows the relationship between the permeation | transmission characteristic of the top plate of the induction heating cooking appliance concerning Embodiment 1, and the spectral radiance curve in each temperature. FIG. 5 shows the spectral radiance curve and the transmittance τ of the top plate 2 when the pan temperature is 150 ° C., 200 ° C., and 250 ° C.

  The condensing surface of the infrared sensor 12 (for example, the condensing lens 121 in the case of the thermopile sensor shown in FIG. 3A) has a wavelength band of 0.6 μm to 2.8 μm having a high transmittance in the top plate 2, It has been found that the use of a filter having transmission characteristics in the range of 3.0 μm to 4.5 μm is desirable for efficiently detecting infrared light transmitted through the top plate 2. In particular, the wavelength band of 3.0 μm to 4.5 μm has a transmittance of about 60% at the peak value of the transmittance of the top plate 2, but the pan temperature is 150 ° C., 200 ° C., as shown in FIG. When the spectral radiance curves at 250 ° C. are also compared, it can be seen that the absolute value of the amount of infrared energy that can be detected from the pan is large. Therefore, in order to particularly increase the transmittance in the range of 3.0 μm to 4.5 μm, at least one of the upper surface and the lower surface of the condenser lens 121 is transmitted in an infrared region such as SiO, ZnS, Ge, and sapphire. A thin film is formed by vapor deposition with a material having absorption / reflection and different refractive index, and has a transmission characteristic of 50% or more in a peak value in a range of 3.0 μm to 4.5 μm, and 3.0 μm to 4 In a region other than 0.5 μm, a band pass filter structure having a transmission characteristic that does not reach half the peak value of 3.0 μm to 4.5 μm is provided except for the region of 0.6 μm to 2.8 μm. By doing in this way, detection with high noise tolerance is possible in a wavelength band in which the energy radiated from the pan passes through the top plate 2.

  In the case of the thermopile provided with the silicon flat plate 124 and the reflector 125 shown in FIG. 3B, the same effect can be obtained by forming the above-described band-pass filter on which the thin film is deposited on the flat plate 124. . In addition, when the flat plate 124 is used, a shape such as a hexagonal column or an octagonal column is formed in addition to cutting into a circular shape by forming a bandpass filter by thin film deposition on a silicon substrate and then cutting it to match the shape of the infrared sensor 12. This is advantageous in that the yield is improved and the manufacturing cost is reduced.

The description of FIG. 2 is continued below.
The infrared sensor 12 is covered with a sensor case 18 so that the cooling air flowing in the vicinity of the heating coil 14 is not directly hit. The infrared sensor 12 is held in the sensor case 18 while maintaining a spatial distance so that the ambient temperature around the infrared sensor 12 is uniform. The sensor case 18 is fixed to the heating coil support portion 16 with a tapping screw or the like, or partly formed integrally with the heating coil support portion 16, and the distance between the top plate 2 and the infrared sensor 12. Is kept constant.

  In the first embodiment, in order to detect the infrared rays of the pan that passes through the top plate 2, it is desirable that the transmission window portion 7 on the upper surface portion of the infrared sensor 12 does not have the coating 13. However, if the transmission window 7 is not coated, the internal heating coil 14 and wiring may be visible from the upper surface of the top plate 2, which is not desirable in design. For this reason, when the coating 13 is not applied to the transmission window 7, a cylinder or a plate is provided in the direction of the top plate 2 on the heating coil support 16 or the sensor case 18 that holds the heating coil 14. What is necessary is just to make it difficult to see the heating coil 14, wiring, etc. from the outside by doing in this way. In addition, instead of covering the entire surface of the transmission window portion 7 with the coating 13, the coating 13 is applied to the transmission window portion 7 in the form of dots or stripes so as to manage the ratio of the unpainted openings. Well, it is possible to ensure design and functionality by doing so.

  Further, two contact temperature sensors 17 which are contact temperature detecting means such as a thermistor are provided in the annular gap 15 between the inner heating coil 14a and the outer heating coil 14b (FIG. 2 shows one contact temperature sensor 17). Only the contact temperature sensor 17 is shown). The two contact temperature sensors 17 are provided at positions shifted by 180 degrees with respect to the center of the heating coil 14. The contact temperature sensor 17 is provided so as to be in close contact with the lower surface of the top plate 2 and outputs a signal corresponding to the temperature of the lower surface of the top plate 2. The output signal of the contact temperature sensor 17 is input to the top plate temperature detector 25 provided in the main body 1. The top plate temperature detector 25 detects the temperature of the top plate 2 based on the signal from the contact temperature sensor 17. In the first embodiment, the contact temperature sensor 17 and the top plate temperature detection unit 25 constitute the top plate temperature detection means of the present invention. As long as the temperature of the top plate 2 can be detected more accurately with less time delay, not only the contact-type temperature sensor 17 such as a thermistor, but any other one can be used as the top plate temperature detection means. .

  In the first embodiment, the contact temperature sensor 17 is provided in the gap 15 between the inner heating coil 14a and the outer heating coil 14b. However, the arrangement of the contact temperature sensor 17 is not limited to this. For example, the contact temperature sensor 17 may be disposed in the vicinity of the outer periphery of the outer heating coil 14 b or may be disposed in the center of the heating coil 14. Moreover, the number of the contact-type temperature sensors 17 is not limited to two, and may be one or two or more.

The output of the contact-type temperature sensor 17 is used when calculating the temperature of the pan based on the amount of infrared rays detected by the infrared sensor 12 as will be described later. For this reason, in order to detect the temperature of a pan more accurately, it is desirable that the contact temperature sensor 17 be installed in the vicinity of the infrared sensor 12.
Note that it is indeterminate where the pan to be heated is placed on the top plate 2, and the pan shape is also indeterminate, so that a wider range of temperatures can be detected and the cost can be reduced. The infrared temperature detection unit 24 and the top plate temperature detection unit 25 may be arranged apart from each other by giving priority to realization.

  If the number of the contact-type temperature sensors 17 is small, the acquisition temperature may vary depending on the position and shape of the object to be heated placed on the top plate 2. For this reason, the average value of the detection values of the plurality of contact-type temperature sensors 17 and the detection value of the output of the highest temperature among the plurality of contact-type temperature sensors 17 are used for the temperature detection of the pan described later. May be. By doing in this way, even when the number of installation of the contact-type temperature sensor 17 is small, temperature detection resistant to variations can be performed.

  Information set by the operation unit 3 and outputs from the infrared temperature detection unit 24 and the top plate temperature detection unit 25 are input and stored in the storage unit 21 provided in the main body 1.

  The calculating part 22 is comprised, for example with a microcomputer etc., and performs the various arithmetic processing which calculates the temperature of a pan.

  The control unit 23 controls the high-frequency inverter 26 based on the setting content of the operation unit 3 and the temperature information of the pan detected based on the physical information detected by the infrared sensor 12 and the contact-type temperature sensor 17. The high-frequency current flowing through the coil 14 is controlled. By doing in this way, heating control of a to-be-heated material is performed.

  In addition, the calculating part 22 and the control part 23 of this Embodiment 1 are equivalent to the control means of this invention.

  FIG. 6 is a diagram illustrating an operation unit and a thermal power display unit provided corresponding to the left heating coil of the induction heating cooker according to the first embodiment. The operation unit 3 and the thermal power display unit 5 respectively corresponding to the heating coil 14 provided on the left side, the right side, and the center of the induction heating cooker 100 have the same configuration. The operation unit 3 and the thermal power display unit 5 provided correspondingly will be described as an example.

The operation unit 3 includes a heating power setting key 31 for setting a heating power (input power) for heating an object to be heated, and a menu key 32 for setting a cooking menu.
The thermal power setting key 31 includes a “low heat” key, a “medium fire” key, a “high fire” key, and a “3 kW” key, and the user uses these keys to select four levels of thermal power (input power). ) Can be set either. By providing keys individually according to the thermal power, the user can input the necessary thermal power settings with a single operation.

  The menu key 32 includes a “fried food” key, a “preheat” key, a “boiled” key, and a “timer” key. When these keys are pressed, the control unit 23 performs heating control so that the temperature of the object to be heated becomes the target temperature in accordance with a control sequence preset for each menu and stored in the storage unit 21.

  The thermal power display unit 5 displays thermal power in a plurality of stages based on the thermal power input by the thermal power setting key 31 and the menu set by the menu key 32, and the display mode is switched according to the thermal power. The display of the thermal power display unit 5 can indicate to the user that it is operating. The thermal power display unit 5 includes, for example, a plurality of LEDs, and expresses thermal power by switching the lighting states (lighting, extinguishing, blinking, etc.) of these LEDs or switching the lighting color. By doing in this way, the user can perform notification which is easy to understand intuitively.

  Although not shown in FIG. 6, the display unit 4 (see FIG. 1) configured with a liquid crystal screen or the like has, for example, a thermal power and progress status such as “during preheating” and “appropriate temperature reached”, set menus, etc. Information on the contents of the is displayed.

  In the induction heating cooker 100 having such a configuration, for example, when fried food cooking is performed, the user puts oil for performing fried food in the pan and places the pan on the heating port 6 of the top plate 2. When the user performs an operation input for starting heating at the operation unit 3, the control unit 23 causes a high-frequency current flowing through the heating coil 14 to flow based on the signal from the operation unit 3 and the estimated temperature of the pan, This heats the pan.

[Pot temperature estimation process]
(Constitution)
Next, the configuration related to the estimation of the pan temperature will be further described.
As described above, the infrared sensor 12 detects infrared energy emitted from the bottom of the pan and infrared energy emitted from the lower surface of the top plate 2 when the top plate 2 is heated by heat conduction.

In the first embodiment, as described above, in the transmission window portion 7 of the top plate 2 that is within the range of the visual field 126 of the infrared sensor 12, the coating 13 is applied in the form of dots or stripes, and the coating is applied to other portions. By reducing this, it is possible to prevent design problems such as the coil wire of the heating coil 14 being seen from above the top plate 2, and an output of 10% or more with respect to the peak value of the infrared detection value in the transmission window 7. The field of view of the infrared sensor 12 is narrowed to enter.
Further, a thin film of ZnS, SiO, Ge or the like is deposited on at least one of the upper surface and the lower surface of the condensing surface of the infrared sensor 12 (the condensing lens 121 and the flat plate 124 illustrated in FIG. 3). A band pass filter having a transmittance of 50% or more in a peak value in a wavelength band of 3.0 μm to 4.5 μm depending on the amount.

Here, the band pass filter will be described.
First, the radiation characteristic of the top plate 2 is represented by Kirchhoff's law [absorption rate (α) + transmittance (τ) + reflectance (ρ) = 1]. The transmission characteristic of the transmittance τ of the top plate 2 is shown in FIG. 4, and the top plate 2 is mostly absorbed rather than reflected in the region of 3.0 μm to 4.5 μm.
For this reason, from the above-mentioned Kirchhoff's law, the absorptance (α) = emissivity (ε) is represented, and the radiation characteristic of the top plate 2 is represented as shown in FIG.

As shown in FIG. 4, the top plate 2 is about 60% at the highest transmittance at 3.0 μm to 4.5 μm, and the infrared sensor 12 is about 40% from the top plate 2. Radiant energy will be detected.
However, the wavelength region other than 3.0 μm to 4.5 μm, particularly the wavelength region (4.5 μm to 10 μm), which is greatly affected by the radiation characteristics of the top plate 2, is blocked by the above-described bandpass filter. Almost no light is received.

  As can be seen from the transmission characteristics in the range of 3.0 μm to 4.5 μm in FIG. 4, the transmission characteristics change in the wavelength region around 3.6 μm.

The transmission characteristics of the bandpass filter are determined in consideration of the radiation characteristics and transmission characteristics of the top plate 2.
FIG. 8 is a graph showing an example of transmission characteristics of the band-pass filter of the induction heating cooker according to the first embodiment. In FIG. 8, the transmission characteristics of the bandpass filter and the transmission characteristics of the top plate 2 are displayed side by side. The band-pass filter is a filter having a transmittance of about 90% at maximum in the range of 3.4 μm to 4.2 μm. In addition, although the band pass filter illustrated in FIG. 8 has transmission characteristics even in a region with a wavelength shorter than 2.8 μm, it is 200 ° C., which is a normal use temperature of the top plate 2 of the induction heating cooker 100. If it is about the extent, when the radiation characteristic of the top plate 2 is taken into consideration, the influence of the infrared energy emitted from the top plate 2 on the infrared sensor 12 is small. For this reason, even if the bandpass filter has the transmission characteristics as described above, the influence on the detection accuracy of the infrared sensor 12 is small.

  By using the bandpass filter, the infrared energy emitted from the pan and transmitted through the top plate 2 is detected by the infrared sensor 12 from the time when the temperature of the pan reaches about 80 ° C. The detection value of the infrared sensor 12 increases exponentially as the temperature of the pan increases. However, as described above, since the bandpass is applied to the region where the transmittance of the top plate 2 is not 100%, the infrared sensor 12 also detects the infrared radiation energy from the top plate 2, and the top plate 2 Since the transmission characteristics have different transmittances for each wavelength, the ratio between the amount of infrared radiation energy from the pan and the amount of infrared radiation energy from the top plate 2 varies depending on the temperature of the pan bottom and the temperature of the top plate 2.

  If a bandpass filter is not provided, if a silicon base material is used for the condensing part of the infrared sensor 12, the transmission characteristic that silicon transmits about 50% to 60% in the infrared wavelength region shorter than 8 μm. Therefore, it can be very large compared to the ratio of infrared energy from the top plate 2. Then, since a problem arises with respect to detection accuracy, it is preferable to provide a band-pass filter in the configuration of the first embodiment.

  Further, by using the same material as the top plate 2 as a band pass filter, it is possible to detect infrared energy from the pan that has passed through the top plate 2. However, as described above, due to the characteristics of the material of the top plate 2, the absorption rate in the infrared region is high, so the filter itself is heated by the infrared rays emitted from the top plate 2 and the internal heating coil 14, and the filter itself. As a result, the infrared rays emitted from the infrared rays affect the infrared detection of the infrared sensor 12. For this reason, it is necessary to take measures such as providing temperature detection means in the filter to cancel out radiation from the filter itself, and the cost increases due to the addition of temperature detection means provided in the filter. For this reason, in this Embodiment 1, it is preferable to provide the above band pass filters.

  As described above, the ratio of the amount of infrared energy detected by the infrared sensor 12 varies depending on the temperature of the pan and the temperature condition of the top plate 2. It is a fluctuation factor. In particular, in the induction heating cooker as in the first embodiment, since pans with various emissivities are placed, emissivity ε does not assume various conditions from 0.1 to 0.9, for example. Must not. The method for estimating the emissivity ε will be described later. In order to accurately estimate the temperature of the pan placed on the top plate 2, the temperature of the pan placed on the top plate 2 is estimated. It is desired to estimate the temperature difference between the top plate 2 and the temperature of the top plate 2 and to estimate the bottom emissivity of the pan placed on the top plate 2.

  Therefore, in the pan temperature estimation process according to the first embodiment, when the pan temperature is estimated by subtracting the influence of the top plate 2 from the temperature detected by the infrared temperature detector 24, the bottom surface of the pan and the top plate 2 are estimated. A gap amount determination process for estimating a gap distance between the surface and the emissivity estimation process for estimating the emissivity of the bottom surface of the pan is performed. Hereinafter, an outline of each process will be described in order.

(Gap amount judgment processing)
The gap amount determination process is a process of estimating a gap distance between the bottom surface of the pan and the surface of the top plate 2. Here, the gap distance refers to the height distance of the gap between the bottom surface of the pan and the surface of the top plate 2, and refers to the height at which the bottom surface of the pan floats from the surface of the top plate 2. When the bottom of the pan is warped or when an object is sandwiched between the top plate 2 and the pan, a gap (air layer) is created between the bottom of the pan and the top plate. Detect the height distance of the gap.

The clearance distance is determined based on an output value from the initial heating stage of the contact-type temperature sensor 17 disposed in contact with the lower surface of the top plate 2. The thermal conductivity is, for example, 16 W / (m · K) for a stainless steel pan and 1.5 W / (m · K) for the top plate 2, whereas the thermal conductivity of air is 0.024 W / This is a very small value (m · K). For this reason, if the gap distance between the pan bottom and the top plate 2 is 0.5 mm, the amount of temperature rise of the top plate 2 detected by the contact-type temperature sensor 17 becomes small. Further, as shown in the atmospheric transmission characteristic graph of FIG. 9, the atmosphere also has a transmittance, and a gap is formed between the pan bottom and the top plate 2, so that the amount of infrared rays radiated from the pan is attenuated. Occurs. Therefore, the greater the gap distance between the pan bottom and the top plate 2, the less the infrared energy that reaches the top plate 2, and the smaller the temperature rise value detected by the contact temperature sensor 17.
For this reason, the gap distance between the pan bottom and the surface of the top plate 2 is determined based on the temperature increase detected by the contact temperature sensor 17 and the gap distance level setting table shown in FIG. be able to.

  In the gap amount determination process for determining the gap distance, a constant heating power is input in the initial stage of heating, and the gap distance is determined based on the magnitude of the temperature rise value of the contact-type temperature sensor 17 after a predetermined time. The output of the contact temperature sensor 17 used for the determination of the gap distance may be an average value of the output values of the plurality of contact temperature sensors 17 or indicates the highest temperature among the output values of the plurality of contact temperature sensors 17. A value may be used, or a value obtained by averaging the upper two output values for detecting a high temperature among the output values of the plurality of contact temperature sensors 17 may be used. As described above, by using the output values of the plurality of contact-type temperature sensors 17, it is possible to suppress variations in temperature detection.

  In addition, the determination of the gap distance in the initial stage of heating is based on the characteristics of the oil in the pan used in fried food cooking. That is, when oil is used in deep-fried food cooking, the viscosity of the oil is high, and the temperature rises almost uniformly without convection even after the heating power is added. As the oil temperature rises, the viscosity decreases and the convection starts and the heat diffuses. However, if the heating is performed for a predetermined time, for example, about 50 seconds, the bottom of the pan is almost constant regardless of the amount of oil. Become.

  Thus, the gap distance, which is the height of the gap between the pan bottom and the top plate 2, can be estimated using the temperature rise value of the contact-type temperature sensor 17 when heated with a constant heating power for a predetermined time from the initial stage of heating. .

(Emissivity estimation processing)
In the first embodiment, the emissivity of the pan bottom is determined by the temperature rise value detected by the infrared temperature detection unit 24 after a predetermined time has elapsed from the start of heating. Comparing the temperature rise value of the infrared temperature detection unit 24 for a predetermined time, the temperature rise value becomes large at the pan bottom with high emissivity, and the temperature rise value becomes small at the pan bottom with low emissivity. Determine the emissivity of the pan bottom.

  In the first embodiment, the emissivity estimation process is started not after the initial heating but after the elapse of a predetermined first time (for example, 50 seconds) from the start of heating, and then after the elapse of a predetermined second time (for example, 30 seconds) This is performed based on the temperature rise value detected by the infrared temperature detection unit 24 later. Since the infrared sensor 12 used in the first embodiment uses a band-pass filter in the band of 3.0 μm to 4.5 μm, it starts after a predetermined first time has elapsed. This is because the output value of the infrared sensor 12 does not increase unless the temperature reaches about 80 ° C. Therefore, a specific numerical value for the first time may be determined in consideration of the wavelength received by the infrared sensor 12.

  Moreover, in this Embodiment 1, after the above-mentioned gap | interval amount determination process is complete | finished, based on the temperature rise value detected by the infrared temperature detection part 24, the emissivity of a pan is estimated. By starting the determination of the emissivity of the pan using the infrared temperature detection unit 24 after the gap amount determination is completed, the information detected by the infrared temperature detection unit 24 is obtained using the known gap distance. It can correct | amend and can improve the detection accuracy of a temperature rise value. That is, the ratio of radiation from the top plate 2 is large when there is no gap distance (small), and small when the gap distance is large. To reflect. More specifically, the emissivity of FIG. 11 stored in advance in the storage unit 21 based on the gap distance and the amount of increase in the correction value of the output value of the infrared temperature detection unit 24 obtained using the gap distance. The emissivity is derived with reference to the setting table. Note that the measurement by the infrared temperature detection unit 24 may be started before the gap amount determination process is finished, and the result of the pot gap distance determination may be fed back to the measurement result.

  Although it is the influence of the atmospheric transmittance shown in FIG. 9, in the wavelength band of the bandpass filter used in the first embodiment (see FIG. 4), there is almost no influence of the attenuation of infrared rays by the atmosphere. Even if the bottom of the pot floats and the distance between the bottom of the pot and the infrared sensor 12 increases, detection with no variation can be performed without any problem.

(Pot temperature estimation process)
The control unit 23 of the induction heating cooker 100 estimates the pan temperature based on the output values of the infrared temperature detection unit 24 and the top plate temperature detection unit 25 (the estimated pan temperature is referred to as “pan temperature estimation value Tn”). ) So that the estimated pan temperature becomes the temperature of the pan corresponding to the target temperature set by the operation unit 3 or the target temperature set according to the cooking menu (referred to as “target value to be heated”). The high frequency power supplied to the heating coil 14 is controlled by controlling the high frequency inverter 26.

Here, of the infrared energy amount received by the infrared sensor 12 due to the difference between the gap distance and the emissivity as described above, the infrared energy amount radiated from the top plate 2 and the radiated from the pan and transmitted through the top plate 2. The proportion of infrared energy is different. Therefore, in calculating the pan temperature estimated value Tn, the correction coefficients α and β are derived from the correction coefficient setting table shown in FIG. 12 based on the calculated gap distance and emissivity, and the following equation (1) is used. The pan temperature estimated value Tn is estimated.
Pan temperature estimated value Tn = α × IR−β × TH (1)
However, the code | symbol of Formula (1) is as follows.
IR: output value of infrared temperature detection unit 24 TH: output value of top plate temperature detection unit 25 α: first correction coefficient β: second correction coefficient

  As shown in Expression (1), in the first embodiment, the output value of the infrared temperature detection unit 24 is multiplied by a correction coefficient α (first correction coefficient) to obtain an infrared temperature correction value, and the top plate The output value of the temperature detection unit 25 is multiplied by a correction coefficient β (second correction coefficient) to obtain a top plate temperature correction value. And the pan temperature estimated value Tn of the pan is obtained by subtracting the top plate temperature correction value from the infrared temperature correction value. In addition, the pan temperature estimated value Tn is corresponded to the 1st to-be-heated material temperature of this invention.

Conventionally, infrared energy radiated from the pan detected by the infrared sensor 12 and transmitted through the top plate 2 and infrared radiation radiated from the top plate 2 obtained by the top plate temperature detector 25 from the infrared energy radiated from the top plate 2. The energy calculation when subtracting the energy required a multiplication of the fourth power and the emissivity with respect to the output temperature as derived from the Stefan-Boltzmann equation.
However, since calculation of the fourth power by the calculation unit 22 such as a microcomputer increases the load, the first embodiment employs the simplified formula (1) obtained from the experimental results.

  The correction coefficient table shown in FIG. 12 is a table in which a combination of a gap distance (mm) and an emissivity, a correction coefficient α (first correction coefficient), and a correction coefficient β (second correction coefficient) are combined. As shown in FIG. 12, in the case of the same emissivity, when the gap distance is large, the correction coefficient β (second correction coefficient) is a smaller value than when the gap distance is small. This indicates that the larger the gap between the pan bottom and the top plate 2, the greater the temperature difference between the pan bottom and the top plate 2 when the temperature is stabilized, and the smaller the proportion of infrared rays emitted from the top plate 2 is. . Therefore, the larger the gap distance is, the smaller the correction coefficient β applied to the output value of the top plate temperature detector 25 is reduced, thereby reducing the amount of deducting the influence of the top plate 2 in calculating the pan temperature estimated value Tn. . Note that the same effect can be obtained by increasing the correction coefficient α instead of decreasing the correction coefficient β.

  As shown in FIG. 12, when the gap distance level is the same, the correction coefficient α (first correction coefficient) is larger when the emissivity is low than when it is high. This is because the lower the emissivity, the smaller the infrared energy radiated from the bottom of the pan, the smaller the amount of infrared light that passes through the top plate 2, and the need for amplification correction. For the same reason, when the gap distance level is the same, the correction coefficient β (second correction coefficient) is smaller when the emissivity is low than when it is high. By doing in this way, the amount which deducts the influence part of the top plate 2 is reduced in calculating the pan temperature estimated value Tn.

As described above, by multiplying the correction coefficient α determined from the determined result by the output value of the infrared temperature detection unit 24 and by multiplying the correction coefficient β by the output value of the top plate temperature detection unit 25, The temperature at the bottom of the pan can be estimated.
Note that the correction coefficient setting table shown in FIG. 12 is configured with values obtained in advance through experiments or the like, and is stored in the storage unit 21.

  In this way, the pot temperature estimated value Tn is estimated, and the control unit 23 supplies power to the heating coil 14 so that the pot temperature estimated value Tn reaches the object to be heated target value.

(Temperature estimation process for overheating suppression)
As described above, it is possible to accurately calculate the pan temperature estimated value Tn by using the gap distance and the emissivity. For example, the top plate 2 may already start heating in a high temperature state. The initial temperature of the plate 2 is not constant, and a pan having an indefinite structure, such as a deformed pan having irregularities on the bottom surface or a thin pan, can be used. Then, the radiation and heat conduction form applied to the top plate 2 change, the gap distance and the emissivity are erroneously detected, and the actual pan temperature becomes higher than the calculated pan temperature estimated value Tn. If so, the temperature of the oil may become excessively high.
In consideration of such an irregular case, in the first embodiment, processing for avoiding and suppressing excessive heating is executed in parallel with the above-described heating control.

Specifically, the calculation unit 22 derives the correction coefficients γ and β from the correction coefficient setting table shown in FIG. 12 based on the output value of the infrared temperature detection unit 24 and the output value of the top plate temperature detection unit 25. The overheating monitoring temperature Tem is estimated from the equation (2).
Overheating monitoring temperature Tem = γ × IR−β × TH (2)
However, the code | symbol of Formula (2) is as follows.
IR: output value of infrared temperature detection unit 24 TH: output value of top plate temperature detection unit 25 γ: third correction coefficient β: second correction coefficient

  As shown in the equation (2), in the first embodiment, the output value of the infrared temperature detector 24 is multiplied by a correction coefficient γ (third correction coefficient) to obtain a second infrared temperature correction value. The output value of the top plate temperature detector 25 is multiplied by a correction coefficient β (second correction coefficient) to obtain a top plate temperature correction value. The overheating monitoring temperature Tem is obtained by subtracting the top plate temperature correction value from the second infrared temperature correction value. The overheating monitoring temperature Tem corresponds to the second heated object temperature of the present invention.

  As shown in FIG. 12, the third correction coefficient γ is a value larger than the first correction coefficient α used for calculating the pan temperature estimated value Tn. Therefore, the overheating monitoring temperature Tem becomes a value larger than the pan temperature estimated value Tn.

  Then, when the overheating monitoring temperature Tem reaches a preset overheating suppression threshold, the control unit 23 stops heating or reduces the thermal power. That is, the control unit 23 basically controls the magnitude of the thermal power based on the pan temperature estimated value Tn, but the overheating monitoring temperature Tem is one of the conditions for stopping the heating or lowering the thermal power. Use the value.

  When the pan temperature estimated value Tn is calculated using the correction coefficients α and β shown in FIG. 12, when a false detection occurs in the gap distance and the emissivity, the pan temperature estimated value Tn and the actual pan temperature The largest difference occurs in the case where it is determined that <the gap distance is small and the emissivity is high> while the gap distance is large and the emissivity is low. In this case, while the output value of the infrared temperature detection unit 24 is the smallest, the correction coefficient α is also the smallest, and before it is determined that the pot temperature estimated value Tn has reached the target heating target value, the actual pot Becomes higher than the target value of the object to be heated. Therefore, as shown in FIG. 12, the correction coefficient γ has the largest difference between the estimated pot temperature Tn and the actual pot temperature when the gap distance and the emissivity are erroneously detected. Is small and the emissivity is high> (second line from the top in FIG. 12), the largest value is set. By doing so, even if the gap distance and the emissivity are erroneously determined, the overheating monitoring temperature Tem reaches the overheating suppression threshold relatively quickly and heating is stopped.

[Heating control operation of cooking device]
Next, regarding the heating control for keeping the temperature of the heated object substantially constant at the target temperature and the heated object temperature detecting process for detecting the temperature of the heated object, the flowcharts of FIGS. The description will be given with reference. FIG. 13 is a flowchart illustrating mainly the gap distance determination process of the induction heating cooker according to the first embodiment.

It is assumed that a pan, which is a heated object filled with oil, is placed on the heating port 6 of the top plate 2.
In FIG. 13, when the power is turned on (S101) and the fried food mode is selected with the menu key 32 of the operation unit 3 (S102), the control unit 23 determines a target temperature (S103). The temperature of fried food varies depending on the cooking menu (for example, “tempura”, “tonkatsu”, “kara fried”, etc.), and when such a cooking menu is set, the temperature corresponding to that cooking menu is set to the target temperature. And

  When an instruction to start heating is input to the operation unit 3 by the user who has confirmed that the pan is placed on the heating port 6, the control unit 23 drives and controls the high-frequency inverter 26 to control the heating coil. A high frequency current is supplied to 14 and heating is started (S104).

  The control unit 23 stores the output value TH_t0 of the top plate temperature detection unit 25 when heating is started in the storage unit 21 as Tth0, and starts a timer counter (S105). Further, the control unit 23 controls the high-frequency inverter 26 to input a high-frequency current having a predetermined amount and a predetermined frequency, and measures the impedance of the pan based on the current value detected at that time. It is determined whether or not the placed pan is a usable pan. After performing such a pan material determination process, the control unit 23 inputs a thermal power of 1.5 kW if the pan is usable (S106). In addition, although not shown in figure, when the control part 23 determines that the unusable pan is mounted in the top plate 2 by the pan material determination process, it is a pan which cannot be used without heating. This is notified using the display unit 4.

  The controller 23 applies 1.5 kW to the heating coil 14 until the timer counter reaches a predetermined first time (50 seconds in the first embodiment), and when the predetermined first time (50 seconds) elapses. (S107; Yes), the output value TH_t50 of the top plate temperature detection unit 25 at that time is stored in the storage unit 21 as Tth50 (S108).

  The calculation unit 22 calculates a difference ΔTth between Tth0 that is the output value of the top plate temperature detection unit 25 when heating is started and Tth50 that is the output value of the top plate temperature detection unit 25 after 50 seconds (S109). ).

  Next, the calculation unit 22 performs a gap amount determination process for determining the gap distance of the pan by comparing ΔTth calculated in step S109 with the gap distance level table illustrated in FIG. 10 (S110). The gap distance level table shown in FIG. 10 is a table in which the temperature difference ΔTth at the start of heating and a predetermined time after the start of heating, the gap distance (mm), and the level of the gap distance are associated with each other. The gap distance level table is a table of values obtained through experiments or the like, and is stored in the storage unit 21 in advance. In this Embodiment 1, the amount of floats (gap distance) of the pan is divided into seven stages from levels G0 to G6. When the gap amount determination process ends, the control unit 23 branches the process according to the gap distance level (S111, S112,... S117).

  Here, the case where the gap distance determined in step S110 is level G0 will be described with reference to FIG. FIG. 14 is a flowchart illustrating mainly emissivity determination processing and heating control of the induction heating cooker according to the first embodiment. The case where the gap distance is level G1 to G7 will not be described in detail in the first embodiment, but the same processing as that in the case where the gap distance shown below is level G0 is executed.

As shown in FIG. 14, the control unit 23 changes the thermal power to 1.0 kW (S201). That is, when a predetermined first time (50 seconds in the first embodiment) elapses after heating is started (step S106 in FIG. 13), the heating power is reduced.
Next, the control unit 23 stores the output IR_t50 of the infrared temperature detection unit 24 at this time as Tir50 in the storage unit 21, and starts the timer counter (S202).

  When a predetermined second time (30 seconds in the first embodiment) elapses (S203; Yes), the control unit 23 stores the output IR_t80 of the infrared temperature detection unit 24 at this time in the storage unit 21 as Tir80 ( S204).

The calculation unit 22 calculates a difference ΔT_IR that is a difference value between Tir80 and Tir50 (S205).
Next, the calculation unit 22 calculates a difference value ΔT_IR between Tir80 and Tir50 calculated in step S205 (that is, an increase value after 80 seconds from the start of heating to 80 seconds), and a threshold value of the difference value illustrated in FIG. An emissivity estimation process for estimating the emissivity of the pan by comparing with (the threshold value of ΔIR) is performed (S206). Since the influence of the infrared rays from the top plate 2 is different according to the gap distance of the pot, the threshold when estimating the emissivity is different depending on the gap distance level of the pot, as shown in FIG. . For example, when the gap distance is level G0, the emissivity of the pan is estimated by comparing ΔT_IR calculated in step S205 with the threshold value (40 ° C.) of ΔIR corresponding to level G0. The table shown in FIG. 11 is a table of values obtained by experiments or the like, and is stored in the storage unit 21 in advance.

  Next, the calculation unit 22 determines the correction coefficients α and β with reference to the correction coefficient table of FIG. 12 based on the gap distance determined in step S109 and the emissivity of the pan bottom determined in step S206. (S207).

  Next, the computing unit 22 estimates the temperature of the pan placed on the top plate 2 using the above-described equation (1) using the correction coefficients α and β determined in step S207 ( S208). Thereafter, until step S216 is reached, the calculation unit 22 detects the pan temperature estimated value Tn at a predetermined period using the above-described equation (1).

  And the control part 23 determines whether the pan temperature estimated value Tn has reached | attained 130 degreeC lower 50 degreeC than the to-be-heated target value (180 degreeC) (S209), and the thermal power is 1.25 kW in the reached stage. (S210). Next, the control unit 23 determines whether the pan temperature estimated value Tn has reached 150 ° C., which is 30 ° C. lower than the target heating value (180 ° C.) (S211). The power is reduced to 0 kW (S212). Next, the control unit 23 determines whether the pan temperature estimated value Tn has reached 170 ° C. at a value 10 ° C. lower than the target heating target value (180 ° C.) (S213), and when it reaches the heating power, The power is reduced to 0.8 kW (S214). When the estimated temperature Tn of the pan reaches the target heating target value (S215; Yes), the control unit 23 uses the voice notification unit (not shown) such as the display unit 4, the buzzer, and the speaker to finish preheating. Is notified (S216). Although the specific numerical value illustrated in FIG. 14 is an example, the pot is heated by gradually reducing the heating power as the pot temperature estimated value Tn approaches the target heating value (S209 to S214). When reaching the object target value, it is possible to suppress so-called overshooting that the temperature is raised to a temperature higher than the target object value to be heated.

  In parallel with the processing in steps S208 to S215, the calculation unit 22 estimates the overheating monitoring temperature Tem using the correction coefficients γ and β determined in step S207 and the above equation (2) (S301). . And the control part 23 compares the overheating monitoring temperature Tem with the preset overheating suppression threshold value (290 degreeC in this Embodiment 1) (S302). If the overheating monitoring temperature Tem has not reached the overheating suppression threshold (S302; No), step S301 and step S302 are repeated. On the other hand, when the overheating monitoring temperature Tem reaches the overheating suppression threshold (S302; Yes), the display unit 4, a buzzer, a voice notification unit (not shown) such as a speaker, etc. is used to notify that preheating has ended ( S216). In addition to or instead of this, when the overheating monitoring temperature Tem reaches the overheating suppression threshold, the display unit 4 or the voice notification unit is used to notify the user that a problem has occurred, Heating may be stopped (or the heating power is reduced).

  FIG. 15 is a graph showing an example of various temperatures of the induction heating cooker according to Embodiment 1 and the amount of electric power input to the heating coil. In FIG. 15, when the actual pan state is <large gap distance level (G6) and emissivity: low>, when the gap distance and emissivity are correctly determined (FIG. 15 (a)), This is shown in comparison with the case of erroneous determination (FIG. 15B).

  As shown in FIG. 15 (a), when the gap distance and emissivity are correctly determined, when the actual temperature of the pan rises with heating, the estimated pan temperature Tn estimated by the induction heating cooker 100 is also calculated. It rises as well as the actual pan temperature. When the pot temperature estimated value Tn reaches the target object value to be heated (180 ° C. in the example of FIG. 15), the input power to the heating coil 14 is reduced and the current temperature is maintained. In this case, the overheating monitoring temperature Tem does not reach the overheating suppression threshold (290 ° C. in the example of FIG. 15), and heating stops before the pan temperature estimated value Tn reaches the target heating target value. Absent.

  As shown in FIG. 15 (b), when the gap distance and emissivity are erroneously determined, the actual temperature of the pan rises with heating, but the estimated pan temperature Tn is higher than the actual pan temperature. Calculated as a low value. For this reason, the electric energy input into the heating coil 14 based on the pan temperature estimated value Tn is larger than that in FIG. 15A, and the pan temperature estimated value Tn reaches the target heating target value (180 ° C.). Before, the temperature of the actual pan rises and reaches the target value to be heated (180 ° C.). If the heating is continued as it is, the pan will become excessively heated, but the overheating monitoring temperature Tem rises and reaches the overheating suppression threshold, so that the heating amount decreases.

  As described above, in the first embodiment, the output value of the infrared temperature detection unit 24 and the top plate are calculated based on the correction coefficients α and β derived based on the gap distance between the pan bottom and the top plate 2 and the emissivity of the pan bottom. The temperature of the pan bottom is detected by correcting the output value of the temperature detector 25 and subtracting the corrected temperature of the top plate temperature detector 25 from the corrected temperature of the infrared temperature detector 24. For this reason, even when the pan placed on the top plate 2 is floating or warping, the temperature of the pan bottom can be detected with high accuracy. Since it is possible to control the energization of the high-frequency power to the heating coil 14 based on the accurate temperature information detected in this way, it is possible to obtain a cooking device capable of suppressing wasteful heating and insufficient heating. it can.

  Further, in the first embodiment, in parallel with the heated object temperature estimation process and the heating control based on the result as described above, the infrared temperature detection unit 24 uses the correction coefficient γ that is larger than the correction coefficient α. The overheat monitoring temperature Tem is calculated by correcting the output value. When the overheating monitoring temperature Tem reaches the overheating suppression threshold, heating is stopped or the heating power is reduced. For this reason, even when the gap distance and the emissivity are erroneously determined, it is possible to suppress the pan from being excessively heated.

Embodiment 2. FIG.
The basic configuration of the induction heating cooker shown in the second embodiment is the same as that of the first embodiment. In the above-described first embodiment, the operation control in the case where the temperature of the object to be heated is kept substantially constant has been described by taking the fried food cooking menu as an example. However, in the second embodiment, the user manually sets the heating power. The operation control when heating is performed will be described. In the second embodiment, the difference from the first embodiment will be mainly described.

  When heating by manual operation, the control for keeping the temperature of the pan substantially constant as shown in Embodiment 1 is not performed. That is, in the manual operation, the controller 23 basically does not perform the heating control so as to calculate the pan temperature estimated value Tn and reach the target heating target value. Operation control is performed such that high-frequency power is supplied to the heating coil 14 so as to obtain the thermal power set in (1).

  However, even when heating is performed manually, the pan may be excessively heated depending on conditions such as the emissivity and gap distance of the pan. Then, the induction heating cooking appliance 100 of this Embodiment 2 performs control for suppressing that a pan becomes high temperature excessively, performing electricity supply control so that the set thermal power may be obtained.

Specifically, the calculation unit 22 uses the output value of the infrared temperature detection unit 24 and the output value of the top plate temperature detection unit 25 and the correction coefficients δ and η shown in FIG. Is used to estimate the overheating monitoring temperature Tr_em for the normal mode.
Overheating monitoring temperature Tr_em = δ × IR−η × TH (3)
However, the code | symbol of Formula (3) is as follows.
IR: output value of infrared temperature detector 24 TH: output value of top plate temperature detector 25 δ: fourth correction coefficient η: fifth correction coefficient

  As shown in Equation (3), in the second embodiment, the output value of the infrared temperature detection unit 24 is multiplied by a correction coefficient δ (fourth correction coefficient) to obtain an infrared temperature correction value, and the top plate The output value of the temperature detection unit 25 is multiplied by a correction coefficient η (fifth correction coefficient) to obtain a top plate temperature correction value. Then, the overheating monitoring temperature Tr_em for the normal mode is obtained by subtracting the top plate temperature correction value from the infrared temperature correction value.

  Then, the control unit 23 compares the value of the overheating monitoring temperature Tr_em for the normal mode calculated in a predetermined cycle with the overheating suppression threshold, and the overheating monitoring temperature Tr_em for the normal mode reaches the overheating suppression threshold. Then, heating is stopped or thermal power is reduced.

  The correction factors δ and η are conditions in which the temperature of the pan does not reach an excessively high temperature (for example, 330 ° C.) even under a condition where the emissivity is low and the gap distance is large, and the emissivity is high and there is no gap distance. Even below, for example, it is set to a value such that heating is not stopped or heating power is not reduced at a temperature lower than that required for fried food cooking (for example, 250 ° C.). By doing in this way, it can suppress giving a user a feeling of malfunction by excessively high temperature of a pan, or a thermal power falling unnecessarily.

  By the way, unlike the first embodiment, the fourth correction coefficient δ and the fifth correction coefficient η for the normal mode calculated by the above equation (3) are the gap distance between the actual pan and the top plate 2 and the radiation of the pan. Instead of calculating and deriving the rate, it is a predetermined value. The correction coefficients δ and η are derived by experiments or the like under intermediate conditions of both conditions so that a proper overheating monitoring temperature Tr_em for the normal mode can be obtained even when the gap distance is large and small. Is preferred.

However, since the temperature difference between the top plate 2 and the pan bottom is large and the emissivity of the pan is small due to the large gap distance between the pans, the infrared energy reaching the infrared sensor 12 is relatively small. Further, the value of the overheating monitoring temperature Tr_em for the normal mode is also reduced.
If empty baking is performed with high heating power under such conditions, the surface temperature of the pan may exceed 300 ° C. in several tens of seconds, for example. If it does so, when the fluorine processing is given to the surface of the pan, the fluorine processing peels off and there is also a possibility that the pan may be deformed.

Therefore, in the second embodiment, for example, even when the actual emissivity of the pan is low and the gap distance between the pan bottom and the top plate 2 is large, the frying pan is effectively suppressed, so that the calculation unit 22 is effectively suppressed. Uses the output value of the infrared temperature detection unit 24 and the output value of the top plate temperature detection unit 25 and the correction coefficients ζ and η shown in FIG. 16 to estimate the air baking monitoring temperature Tr_fr by the following equation (4). To do.
Empty firing monitoring temperature Tr_fr = ζ × IR−η × TH (4)
However, the code | symbol of Formula (4) is as follows.
IR: output value of infrared temperature detection unit 24 TH: output value of top plate temperature detection unit 25 ζ: sixth correction coefficient η: fifth correction coefficient

  As shown in Expression (4), in the second embodiment, the output value of the infrared temperature detection unit 24 is multiplied by a correction coefficient ζ (sixth correction coefficient) to obtain an infrared temperature correction value, and the top plate The output value of the temperature detection unit 25 is multiplied by a correction coefficient η (fifth correction coefficient) to obtain a top plate temperature correction value. Then, by subtracting the top plate temperature correction value from the infrared temperature correction value, the air baking monitoring temperature Tr_fr is obtained.

As shown in FIG. 16, the sixth correction coefficient ζ is a value larger than the fourth correction coefficient δ used for calculating the overheating monitoring temperature Tr_em for the normal mode. Accordingly, the burn-in monitoring temperature Tr_fr is a value higher than the overheating monitoring temperature Tr_em for the normal mode.
Then, the control unit 23 compares the value of the burning temperature monitoring temperature Tr_fr calculated at a predetermined period with the overheating suppression threshold, and when the burning temperature monitoring temperature Tr_fr reaches the overheating suppression threshold, heating is stopped or heating power Reduce.

Since the correction coefficient ζ used for calculating the grill monitoring temperature Tr_fr is a value larger than the correction coefficient δ used for calculating the overheating monitoring temperature Tr_em for the normal mode, when the emissivity of the pan is low and the gap distance is large, It can be detected with higher sensitivity whether or not the pan is heated excessively.
The overheating monitoring temperature Tr_em and the air baking monitoring temperature Tr_fr for the normal mode correspond to the third heated object temperature of the present invention.

  In the case where heating is performed by manual operation, the control unit 23 switches between determination using the overheating monitoring temperature Tr_em for the normal mode and determination using the unburned monitoring temperature Tr_fr. This is because, in the case of the determination using the grilling monitoring temperature Tr_fr, when the actual pan emissivity is low and the gap distance is large, the grilling can be detected more effectively, but the actual pan emissivity is This is because if it is high or the gap distance is small, it is determined to be baked at a relatively low temperature and the heating is stopped or the thermal power is reduced, which may give the user a sense of malfunction. Moreover, in the case of the determination using the overheating monitoring temperature Tr_em for the normal mode, in the case where the actual pan emissivity is high or the gap distance is small, an excessively high temperature of the pan can be effectively detected. This is because when the actual pan emissivity is low and the gap distance is large, detection of the baked state can be delayed as described above.

  Switching between the determination using the overheating monitoring temperature Tr_em for the normal mode and the determination using the empty baking monitoring temperature Tr_fr is performed based on the output value of the top plate temperature detection unit 25. This is because when the heating is performed except when the actual emissivity of the pan is low and the gap distance is large (when the mirror-finished pan is floating from the top plate 2), it is usually caused by heat conduction or infrared radiation from the pan bottom. This is because the temperature of the top plate 2 becomes relatively high. Therefore, it is possible to determine whether or not <when the emissivity is low and the gap distance is large> than the temperature of the top plate 2. The threshold value (determination switching threshold value) of the top plate temperature detection unit 25 for switching between the determination using the overheating monitoring temperature Tr_em for the normal mode and the determination using the unbaking monitoring temperature Tr_fr is, for example, a water heater. The temperature is preferably set to 100 ° C. or lower so as not to cause a problem.

  In the calculation of the firing temperature monitoring temperature Tr_fr, the fifth correction coefficient η multiplied by the output value of the top plate temperature detection unit 25 is the same value as that used for calculating the overheating monitoring temperature Tr_em for the normal mode. The reason for using the burn-in monitoring temperature Tr_fr is when the temperature of the top plate 2 is difficult to rise (low emissivity and large gap distance), and the output of the top plate temperature detection unit 25 is used. This is because it has been found that even if the correction coefficient multiplied by the value is changed, the influence on the improvement of detection accuracy is small.

  FIG. 17 is a graph showing an example of various temperatures of the induction heating cooker according to the second embodiment and the amount of power input to the heating coil. FIG. 17 shows that the frying pan is set by the thermal power setting using the thermal power setting key 31 under the condition that the determination switching threshold value for switching between the blank firing monitoring temperature Tr_fr for blank firing and the overheating monitoring temperature Tr_em for the normal mode is 70 ° C. The data of the experiment which performed the fried food using are shown. The frying pan used is under the conditions that the gap distance between the pan bottom and the surface of the top plate 2 is 1.0 mm, the emissivity ε = 0.18 of the pan bottom, and the heating power is 2000 W.

  As shown in FIG. 17, the frying pan is heated in an air-baked state at 2.0 kW from the start of heating, and the surface temperature of the frying pan rises rapidly. Under the condition that the temperature of the top plate 2 at the initial stage of heating is low (the output value TH ≦ 70 ° C. of the top plate temperature detection unit 25), the determination using the air baking monitoring temperature Tr_fr using the sixth correction coefficient ζ is performed. In FIG. 17, the overheating monitoring temperature T_em for the normal mode is also virtually indicated by a broken line Y. Then, at time T <b> 1 from the start of heating, the empty firing monitoring temperature Tr_fr reaches the overheating suppression threshold (290 ° C.), so that the input power to the heating coil 14 is suppressed. At this time, the surface temperature of the frying pan is also approaching 290 ° C., but by reducing the input power based on the determination using the air baking monitoring temperature Tr_fr, the occurrence of air baking is suppressed, and the fluorine processing of the frying pan is damaged. Deformation can be suppressed. The frying pan surface temperature shows a slightly decreasing tendency due to a decrease in input power.

  Then, when the output value of the top plate temperature detection unit 25 exceeds the determination switching threshold (70 ° C.) at time T2, the determination using the overheating monitoring temperature Tr_em for the normal mode is performed from the determination using the unburned monitoring temperature Tr_fr. Switch to Then, the overheating monitoring temperature Tr_em for the normal mode is smaller than the idling monitoring temperature Tr_fr and does not reach the overheating suppression threshold (290 ° C.). For this reason, the control unit 23 returns the input power to the heating coil 14 to the set value of 2000 W. Since the output value TH of the top plate temperature detection unit 25 exceeds the determination switching threshold (70 ° C.), the determination using the overheating monitoring temperature Tr_em for the normal mode is performed thereafter. Note that the broken line X shown in FIG. 17 virtually indicates the burn-in monitoring temperature Tr_fr.

  At time T3, the user changes the heating power to 1500 W and puts food into the frying pan. If it does so, while the surface temperature of a frying pan will fall, output value IR of the infrared temperature detection part 24, output value TH of the top plate temperature detection part 25, and overheating monitoring temperature Tr_em for normal modes will also fall.

  As described above, in the second embodiment, the output value of the infrared temperature detection unit 24 and the output value of the top plate temperature detection unit 25 are respectively multiplied by correction coefficients obtained in advance by experiments regarding the gap distance and the emissivity of the pan. By subtracting the corrected temperature of the top plate temperature detecting unit 25 from the corrected temperature of the infrared temperature detecting unit 24, the overheating monitoring temperature (overheating monitoring temperature Tr_em, And air baking monitoring temperature Tr_fr). When this overheating monitoring temperature reaches the overheating suppression threshold, heating is stopped or the heating power is reduced. For this reason, in the heating by manual operation, it can suppress that a pan becomes high temperature too much.

  In the second embodiment, two types of overheating monitoring temperatures (normal mode overheating monitoring temperature Tr_em and idling monitoring temperature Tr_fr) having different sensitivities are switched to perform the above determination. did. For this reason, even under conditions where the emissivity and gap distance of the pan are different, it is possible to suppress a feeling of inconvenience that the heating power during cooking is unnecessarily lowered, and to suppress excessive heating of the pan.

  DESCRIPTION OF SYMBOLS 1 Main body, 2 Top plate, 3 Operation part, 4 Display part, 5 Thermal power display part, 6 Heating port, 7 Transmission window part, 8 Exhaust port, 9 Intake port, 12 Infrared sensor, 13 Coating, 14 Heating coil, 14a Inside Heating coil, 14b outer heating coil, 15 gap, 16 heating coil support, 17 contact temperature sensor, 18 sensor case, 21 storage unit, 22 calculation unit, 23 control unit, 24 infrared temperature detection unit, 25 top plate temperature detection Part, 26 high frequency inverter, 31 heating power setting key, 32 menu key, 100 induction heating cooker, 121 condenser lens, 122 thermopile chip, 123 self-temperature detection thermistor, 124 flat plate, 125 reflector, 126 field of view, 200 pan.

Claims (1)

A top plate on which an object to be heated is placed;
Heating means disposed under the top plate;
Operating means for setting a target temperature of the object to be heated;
An infrared sensor that is provided under the top plate and detects infrared rays emitted from above;
An infrared temperature detecting means for converting the output value of the infrared sensor into a temperature;
A top plate temperature detecting means for detecting the temperature of the top plate;
Control based on detection results of the infrared temperature detection means and the top plate temperature detection means, and control means for controlling the heating means based on the calculation results;
Based on the amount of increase in the output value of the top plate temperature detection means when a constant heating power is applied for a predetermined time after starting heating by the heating means, the surface of the top plate and the bottom surface of the object to be heated A gap distance calculation unit that calculates a gap distance that is a distance between,
The control means includes
The top plate temperature correction value obtained by multiplying the output value of the top plate temperature detection means by the second correction coefficient is subtracted from the infrared temperature correction value obtained by multiplying the output value of the infrared temperature detection means by the first correction coefficient. A heated object temperature estimation process for estimating the first heated object temperature,
By subtracting the top plate temperature correction value from the infrared temperature correction value obtained by multiplying the output value of the infrared temperature detection means by a third correction coefficient that is larger than the first correction coefficient, a second heated object is obtained. Overheating suppression temperature estimation processing for estimating the object temperature,
Controlling the heating means so that the first heated object temperature becomes a heated object target value that is a temperature of the heated object corresponding to the target temperature set by the operating means;
When the temperature of the second object to be heated exceeds a first overheating suppression threshold that is higher than the preset target value of the object to be heated, the heating by the heating means is stopped or the heating power is reduced. It is what
At least one of the first correction coefficient and the second correction coefficient is selected from values stored in advance according to the gap distance.

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