JP2010244999A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an infrared light receiving means to be used for a conventional induction heating cooker is subjected to radiation heat from a cooking vessel, and radiation heat and conduction heat from surrounding heating components including a coil and a ferrite to put an infrared sensor under severe circumstances of high temperature which the sensor has to withstand. <P>SOLUTION: This induction heating cooker includes a thermopile for detecting the amount of radiated infrared light, a window material having the same optical characteristics as a top plate arranged on the light receiving front face of the thermopile, a temperature detecting circuit for detecting the temperature of the bottom face of a cooking vessel from the output of the thermopile, an infrared light emitting means for projecting light to the bottom face of the cooking vessel and the lower face of the top plate near the thermopile, an infrared light receiving means for receiving reflected light from the cooking vessel and the lower face of the top plate, and a temperature correcting means for correcting the output of the temperature detecting circuit rather than the output of the infrared light receiving means. The thermopile, the infrared light emitting means and the infrared light receiving means are arranged on the same printed wiring board, and the printed wiring board is stored in a resin case and sealed by the window material to allow for accurate detection of the temperature of a pan. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an induction heating cooker that can accurately detect the temperature of a pan on a top plate.

  Conventionally, as a method for detecting the temperature of a pan in an induction heating cooker, a temperature sensor such as a thermistor that is in contact with the back of the top plate on which the pan is placed is used to indirectly detect the temperature of the pan bottom, or infrared rays emitted from the pan bottom. Is detected with an infrared sensor through the top plate to detect the temperature (Patent Document 1).

  In the pan temperature detection method using an infrared sensor, even if the pan bottom temperature is the same, if the emissivity is different, there is a problem that the temperature detected by the infrared sensor is different, so the technology to solve this is based on the emissivity of the pan bottom A technique for correcting the temperature detected by the infrared sensor is also known (Patent Document 2). In addition, a technique for reducing the influence of electromagnetic noise, disturbance light, and temperature inside the main body on the infrared sensor by housing the infrared sensor in a magnetic shielding case is also known (Patent Document 3).

JP 2004-164883 A Japanese Patent Application Laid-Open No. 11-225881 JP 2008-226573 A

  The infrared sensor used in Patent Document 1 or Patent Document 2 uses a thermal thermopile that detects the amount of radiant heat, a quantum photodiode, or the like. These infrared sensors are arrange | positioned in the position adjacent to the center of a heating coil and a heating coil inner periphery so that patent document 1 and patent document 3 may demonstrate.

  However, the temperature of the pan bottom at the position adjacent to the center of the heating coil or the inner periphery of the heating coil is greatly different from the maximum temperature of the pan bottom, so the pan bottom temperature is detected at these positions, and the thermal power is based on the detected temperature. Even if it is controlled, there is a problem that it is difficult to appropriately control the maximum temperature of the pan bottom.

  The 1st subject of this invention is providing the induction heating cooking appliance which can detect the temperature of the maximum temperature vicinity of the pan bottom.

  Further, Patent Document 2 does not describe where and how to install a light receiving sensor that outputs a signal to the reflection detection circuit, and reduces accuracy degradation of reflectance measurement based on the output of the light receiving sensor. Was not considered. For example, this light receiving sensor has a problem that the accuracy of reflectance measurement deteriorates due to the influence of radiant heat, conduction heat, electromagnetic noise, disturbance light, and the like from surrounding heat generating components.

  Further, in Patent Document 2, since the three members of the light emitting means, the infrared sensor, and the light receiving means are independent, the light emitting means, the light receiving means are used to accurately obtain the reflectance at the pan bottom position measured by the infrared sensor. Needed to be installed with high accuracy. In other words, when the installation positions of the light emitting means and the light receiving means are not appropriate, the reflectance at a position that is not the pan bottom position measured by the infrared sensor is measured, and infrared light is detected using this incorrect reflectance. When the pan bottom temperature measured by the sensor is corrected, there is also a problem that the measured temperature cannot be corrected appropriately.

  The second problem of the present invention is to provide an induction heating cooker that appropriately corrects the measurement temperature by reducing the accuracy degradation of reflectance measurement.

  The above-described problems include a top plate on which a pan is placed, a heating coil that is provided below the top plate and includes an inner coil and an outer coil, and a high-frequency power supply that supplies high-frequency power to the heating coil. A circuit, an infrared sensor module provided below a gap between the inner and outer coils, a temperature detection circuit for calculating the temperature of the pan based on an output of the infrared sensor module, and the infrared sensor module An emissivity calculation circuit for calculating the emissivity of the pan based on the output of the pan, and the temperature of the pan calculated by the temperature detection circuit is corrected using the emissivity of the pan calculated by the emissivity calculation circuit, This is solved by an induction cooking device comprising a control circuit that controls the high-frequency power supply circuit in accordance with the corrected temperature.

  According to the present invention, the temperature near the maximum temperature of the pan bottom can be detected, and the detection temperature based on the reflectance can be corrected appropriately.

The external appearance perspective view of the induction heating cooking appliance of one Example. The heating coil top view of the induction heating cooking appliance of one Example. The heating coil bottom view of the induction heating cooking appliance of one Example. Sectional drawing of the induction heating cooking appliance of one Example. The functional block diagram of the pot heating control system of the induction heating cooking appliance of one Example, and sectional drawing of an infrared detection module. The heating coil top view of the conventional induction heating cooking appliance. The pan heating distribution map by the heating coil of the conventional induction heating cooker. The sensor position schematic diagram of the induction heating cooking appliance of one Example. The sensor position schematic diagram of the induction heating cooking appliance of one Example. The pot heating distribution map by the heating coil of the induction heating cooking appliance of one Example. The figure which shows the pan distance at the time of frying pan lifting. The infrared transmission characteristic graph of the top plate of one Example. Sectional drawing of the infrared sensor module 407 of one Example.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is an external perspective view of an induction heating cooker. First, in FIG. 1, 1 is a main body of an induction heating cooking device. 2 is a top plate made of crystallized glass with high heat resistance, and is placed horizontally on the upper surface of the main body 1 to place a metal load such as a pot 501 made of a magnetic material such as iron or a non-magnetic material such as aluminum. It is. The top plate 2 has an optical characteristic of transmitting infrared light having a wavelength of 4 μm or less and cutting infrared light having a longer wavelength. Reference numerals 3a to 3c denote three heating units disposed on the upper portion of the main body 1, and each has a heating coil for induction heating the pan 501 placed on the top plate 2 below. Reference numerals 31 a to 31 c denote infrared transmission regions that transmit infrared rays emitted from the bottom of the pan to the lower side of the top plate 104. Here, the number of heating units is three, but the number of heating units may be one or two. Reference numeral 4 denotes an air inlet that opens upward at the rear portion of the main body 1 and takes cooling air into a control unit (not shown) inside the main body 1. Reference numeral 5 denotes an exhaust port, which opens upward at the rear portion of the main body 1 and discharges the exhaust that has cooled the inside of the main body 1. In this embodiment, the intake port 4 is disposed on the right side of the rear portion of the main body 1 and the exhaust port 5 is disposed on the left side. Reference numeral 6 denotes a grill heating unit provided at the left front portion of the main body 1. Reference numerals 7a to 7c denote operation units provided on the upper surface side of the main body 1 for setting and operating the heating units 3a to 3c. Reference numerals 8a to 8c denote display units that are provided on the upper part of the front surface of the top plate 2 and display the energization states of the heating units 3a to 3c in conjunction with an output control board (not shown).

  FIG. 2 is a top view of the vicinity of the heating coil 200 below the heating unit 3a. The heating coil 200 is composed of an inner peripheral heating coil 201 and an outer peripheral heating coil 202 provided on the same plane with a concentric gap G interposed therebetween, so that current in the same direction flows through both coils. The outer end of the inner peripheral heating coil 201 and the inner end of the outer peripheral heating coil 202 are electrically connected. In this embodiment, the inner peripheral heating coil 201 is provided at a distance of about 30 to 45 mm from the coil center, and the outer peripheral heating coil 202 is provided at a distance of about 55 to 90 mm from the coil center. And 203 is a coil base for holding the heating coil 200, 204 is a detection area of an infrared sensor module provided at a distance of 45 to 55 mm from the center of the coil, and infrared rays emitted from the bottom of the pan are sent to an infrared sensor module 407 to be described later. This is the guiding area. In this embodiment, the size of the detection area 204 of the infrared sensor module is about 10 mm in diameter. Reference numerals 205 to 208 denote thermistors (contact temperature sensors) for measuring the temperature of the lower surface of the top plate 104.

  FIG. 3 is a bottom view of the coil base 203. In FIG. 3, 301 to 312 are radially provided ferrite cores for efficiently inputting the magnetic fields generated by the inner peripheral heating coil 201 and the outer peripheral heating coil 202 to the pan on the top plate 2. is there. The pitch between the ferrite cores 301 and 302 is larger than the pitch of other ferrite cores in order to provide the detection area 204 of the infrared sensor module.

  4 is a cross-sectional view of the main body taken along the plane AA ′ of FIG. In FIG. 4, 401 is a cooling fan, 402 is a motor that drives the cooling fan 401, 403 to 405 are high-frequency power supply circuits that supply high-frequency power to the heating coil 200, and 406 is a flow of cooling air sucked by the cooling fan 401. Reference numeral 407 denotes an infrared sensor module. The coil base 203 is in close contact with the lower surface of the top plate 2 by a spring (not shown).

  FIG. 5 is a functional block diagram showing the pan heating control system. In FIG. 5, reference numeral 501 denotes a pan that is an object to be heated, 502 a temperature detection circuit that calculates the temperature of the pan 501 based on the outputs of the infrared sensor module 407 and the thermistors 205 to 208, and 26 is based on the output of the infrared sensor module 407. An emissivity calculation circuit for calculating the emissivity of the pan 501, 503 corrects the temperature calculated by the temperature detection circuit 502 based on the output of the emissivity calculation circuit 26, and sets the high frequency power supply circuit 405 according to the corrected temperature. It is a control circuit that controls the power supplied to the heating coil 200. Reference numeral 508 denotes a waveguide that guides the infrared rays emitted from the pan 501 to the lower infrared sensor module 407 and prevents the infrared rays emitted from the heating coil 200 from entering the infrared sensor module 407.

  Next, the operation of this embodiment will be described. When the user places the pan 501 on the top plate 2 and operates the operation unit 7a to start heating, the control circuit 503 controls the high-frequency power supply circuit 405 to supply predetermined power to the heating coil 200. When a high-frequency current is supplied to the heating coil 200, an induction magnetic field is generated from the heating coil 200, and an eddy current is generated in the pan on the top plate to be induction heated. This induction heating raises the temperature of the pan, and the food in the pan is cooked.

  In general, an object itself emits infrared rays according to its temperature. The intensity of the infrared rays increases with the temperature of the object. Therefore, if the amount of infrared rays emitted from the pan is measured using the infrared sensor module, the temperature of the pan can be measured instantaneously.

  The problem here is that when induction heating is performed using a heating coil, the temperature at the bottom of the pan does not become uniform, so even if an infrared sensor module is used, the maximum temperature at the bottom of the pan may not be accurately measured. . The temperature measurement by the infrared sensor in the conventional induction heating cooker is demonstrated using FIG. 6, FIG. FIG. 6 is a top view of the vicinity of a conventional heating coil, in which 601 is an integrated heating coil formed at a distance of about 36 mm to about 88 mm from the coil center, and 602 is provided at a position about 15 mm from the coil center. It is a detection area of an infrared sensor module. FIG. 7 shows that when the heating coil 601 is used to heat a stainless steel pan having a relatively thin bottom with high heating power, the maximum temperature of the pan bottom surface temperature reaches about 360 ° C. (ignition temperature of tempura oil). Was measured at a distance of 10 mm from the coil center. As can be seen from FIG. 7, the minimum temperature at the bottom of the pan is about 30 ° C. near the center, and the maximum temperature at the bottom of the pan is about 350-360 ° C. near a distance of 50 to 70 mm from the coil center. That is, the temperature difference between the lowest temperature and the highest temperature is about 330 degrees. This is because the integrated coil 601 has a donut shape, and on the principle of induction heating, the pot portion on the heating coil has the largest eddy current and the largest temperature rise. This is because the temperature rise is small because the current is small. In the detection area 602 of the conventional infrared sensor module provided at a position about 15 mm from the coil center, only a pot bottom temperature of about 60 ° C. could be observed. That is, the temperature difference between the maximum temperature and the observed temperature reached about 270 ° C.

  In the induction heating cooker of this embodiment, in order to measure the pan bottom temperature at a distance of 50 to 70 mm from the coil center where the pan bottom temperature becomes the highest, as shown in FIG. The outer peripheral side heating coil 202 is divided, and the detection area 204 of the infrared sensor module is provided at a distance of 50 mm from the coil center. The detection area 204 provided at a distance of 50 mm from the coil center is a position included in the position of 50 to 70 mm from the coil center where the pan bottom temperature is highest, and at the same time, as shown in FIG. Even when heating a small-diameter pan with the smallest diameter of 120 mm among the high pans, the pan bottom can completely cover the detection area 204 of the infrared sensor module, and the temperature of the pan bottom can be measured. is there.

  FIG. 10 shows a case where a heating pot 200 is used to heat a stainless steel pan having a relatively thin bottom with high heating power, and when the highest point of the pan bottom surface temperature reaches about 360 ° C. (ignition temperature of tempura oil). Was measured at a distance of 10 mm from the coil center. As can be seen from FIG. 10, the minimum temperature at the bottom of the pan is about 50 ° C. near the center, and the maximum temperature at the bottom of the pan is about 360 ° C. near a distance of 70 mm from the center of the coil. The pan bottom temperature observed at a position of about 50 mm from the coil center where the detection area 204 is provided is about 320 ° C. That is, if the configuration of the present embodiment is used, the temperature difference between the maximum temperature and the observed temperature can be only about 40 ° C., and the thermal power control based on the observed temperature can be suitably performed.

  Note that if the gap G between the inner peripheral heating coil 20 and the outer peripheral heating coil 202 shown in FIG. 2 is wide, the pan bottom temperature on the detection area 204 is lowered. Therefore, the narrower the gap G, the better. If it is too much, the detection area is also narrowed, and infrared rays emitted from the bottom of the pan cannot be sufficiently captured. Therefore, it is desirable to set the gap G to a certain extent to about 10 to 20 mm. In this embodiment, the gap G is set to 15 mm.

  Further, as shown in FIG. 3, the thermistor 205 is installed next to the ferrite core 301 next to the detection area 204, and the thermistors 206 and 207 are arranged so as to form a substantially equilateral triangle by the thermistors 205 to 207. The thermistor 208 is arranged at the center of the equilateral triangle. As a result, as shown in Fig. 9, even if the 120mm diameter pan bottom moves within the circle of 200mm diameter, which is the coil heating range, there are always multiple thermistors under the pan bottom, so the temperature at the pan bottom can be detected. It becomes. If there is no infrared sensor module detection area 204 under the pan bottom, high heating power input is not performed and relatively slow heating control is performed.

  In addition, as shown in FIG. 11, when a user cooks using a frying pan or the like, the frying pan 111 may be tilted. In this case, most of the operations are lifting the front side (operation unit side) of the frying pan 111. In this embodiment, since the detection area 204 of the infrared sensor module is located on the opposite side of the operation unit side from the coil center, the distance H between the top plate and the frying pan 111 is shortened, so that the pan bottom temperature is accurately measured even when slightly lifted. it can.

  Next, details of the infrared sensor module 407 will be described with reference to FIG. FIG. 13A is a cross-sectional view in the vicinity of the infrared sensor module 407, and FIG. 13B is a plan view of the infrared sensor module 407 as viewed from above.

  As shown in FIG. 13A, the infrared sensor module 407 includes a resin case 16, an opening 14 provided above the resin case 16, and a magnetic shield that covers the outer shell of the resin case 16 except for the opening 14. A case 13, a window member 15 provided in the opening 14, a thermal infrared detection circuit 131, a reflectance detection circuit 132, and a printed wiring board 27 provided inside the resin case 16 are provided.

  Since the opening 14 of the resin case 16 is sealed by the window material 15, the cooling air does not directly hit the thermal infrared detection circuit 131 and the reflectance detection circuit 132 inside the infrared sensor module 407. That is, with this configuration, the influence of the cooling air on the thermal infrared detection circuit 131 and the reflectance detection circuit 132 is reduced.

  Further, the resin case 16 is made of a resin having a low thermal conductivity, thereby preventing the temperature inside the infrared sensor module 407 from rapidly changing. That is, this configuration prevents the temperatures of the thermal infrared detection circuit 131 and the reflectance detection circuit 132 from changing suddenly due to heat transfer.

  Further, by providing the window member 15 with an optical characteristic that cuts infrared rays (4 μm or more) having a high temperature-raising effect emitted from the top plate 2, the heating coil 200, etc., which have become high temperature, the wavelength having a high temperature-raising effect Are prevented from entering the inside of the infrared sensor module 407. That is, with this configuration, the temperature of the thermal infrared detection circuit 131 and the reflectance detection circuit 132 is prevented from suddenly changing due to infrared rays having a high temperature-raising effect. In the present embodiment, the infrared transmission characteristics of the top plate 2 and the infrared transmission characteristics of the window member 15 are the same.

  Furthermore, the magnetic shielding case 13 is made of non-magnetic aluminum, so that the electromagnetic noise entering the infrared sensor module 407 is reduced, and the radiation heat received by the magnetic shielding case 13 is easily radiated.

  By adopting such a configuration, the infrared detection circuit 131 and the reflectance detection circuit 132 can reduce the adverse effects of cooling air, abrupt changes in ambient temperature, infrared rays having a high temperature-raising effect, and electrical noise. In the wide temperature range from 150 to 300 ° C., a highly accurate signal can be output, and the temperature of the pan 501 can be measured accurately.

  Next, signal detection in the infrared sensor module 407 will be described. The infrared rays radiated from the bottom surface of the pan 501 reach the thermal infrared detection circuit 131 via the path 30 (the top plate 2, the waveguide 508, and the window material 15) that is the radiant infrared visual field range. Infrared light emitted from the reflectance detection circuit 132 reaches the pan 501 via the path 29 (window member 15, waveguide 508, top plate 2), and infrared light reflected by the pan 501 passes through the path 29. It returns to the reflectance detection circuit 132 through the return path (top plate 2, waveguide 508, window material 15). That is, it can be seen that infrared rays reach both the thermal infrared detection circuit 131 and the reflectance detection circuit 132 through both the top plate 2 and the window material 15.

  Since the infrared ray transmission characteristics of the window member 15 and the infrared ray transmitting member 507 are the same as those of the top plate 2, the short wavelength infrared ray transmitted through the top plate 2 among the infrared rays emitted from the pan 501 is the window member 15 and the infrared ray transmitting member 507. Also penetrates. On the other hand, the long-wavelength infrared light cut by the top plate 2 is also cut by the window material 15 and the infrared transmitting member 507. The window material 15 also receives infrared rays radiated from the lower surface of the top plate 2 that has become hot due to heat transfer from the pan 501, but most of the infrared rays are long-wavelength infrared rays that are cut by the window material 15. Therefore, most of the infrared rays emitted from the top plate 2 are cut by the window material 15. That is, most of the infrared rays radiated from the top plate 2 do not reach the infrared rays that reach the thermal infrared detection circuit 131 and the reflectance detection circuit 132. Therefore, the thermal infrared detection circuit caused by the infrared rays emitted from the top plate 2 131 and the reflectance detection circuit 132 can prevent deterioration of the output signal.

  Next, the thermal infrared detection circuit 131 will be described in detail. The thermal infrared detecting circuit 131 amplifies the output of the thermopile 12, the infrared transmitting member 507 obtained by processing the same material as the top plate 2 into a lens shape, the infrared pile 12 that detects infrared rays emitted from the bottom of the pan 501, and the like. The amplifier 21 is configured. Although the infrared energy that reaches the thermopile 12 is weak, integrating the thermopile 12 and the amplifier 21 can reduce electromagnetic noise mixing between the thermopile 12 and the amplifier 21. Then, a signal with a low S / N ratio is output from the thermal infrared detection circuit 131 by amplifying a signal with little noise contamination after being amplified 5000 to 10,000 times by the amplifier 21.

  Here, the principle of the thermopile 12 will be described. The thermopile 12 outputs a voltage proportional to the received infrared energy, and is a collection of thermocouples in one place. For this reason, when the temperature of the pan rises, the infrared radiation intensity from the pan bottom increases, the amount of infrared energy received by the thermopile 12 increases, and the output signal voltage of the thermopile 12 increases. In general, there is Stefan-Boltzmann's law (Equation 1) that the infrared energy emitted from an object is proportional to the fourth power of the absolute temperature of the object, and the higher the temperature, the higher the infrared energy that is radiated. That is, if the radiation amount W per unit area can be known using the thermopile 12, the absolute temperature of the radiating object can be calculated based on Equation 1.

W = (2π ⁵ κ ⁴ / 15c ² h ³ ) × T ⁴ = σT ⁴ (Formula 1)
W: Radiation amount per unit area (W / cm ² · μm)
κ: Boltzmann constant = 1.3807 × 10 ⁻²³ (W · s / K)
c: speed of light = 2.999 × 10 ¹⁰ (cm / s)
h: Planck's constant = 6.6261 × 10 ⁻³⁴ (W · s ² )
σ: Stefan-Boltzmann constant = 5.6706 × 10 ⁻¹² (W / cm ² · K ⁴ )
T: Absolute temperature of the radiating object (K)

  Next, FIG. 12 is used to show the relationship between the transmittance and wavelength of various materials, and the relationship between the radiant energy of the black body temperature and the wavelength. As shown in the upper graph of FIG. 12, quartz, sapphire, and silicon have high transmittance in a predetermined wavelength band, whereas the crystallized glass used for the top plate 2 in this embodiment has a wavelength of about 0.5. The transmittance exceeds about 80% in the band of ~ 2.6 μm, the transmittance is about 30% or more at the wavelength of about 0.42 to 2.7 μm and about 3.2 to 4 μm, and the wavelength is about 0.3. The transmittance is less than about 30% at 42 μm or less, about 2.7 to 3.2 μm, and about 4 μm or more. As shown in the lower graph of FIG. 12, the heat radiation energy of a black body at 100 ° C. takes a maximum value at about 2 μm and a minimum value at about 7 μm, and the heat radiation energy of a black body at 200 ° C. is about 1 It takes a maximum value at .5 μm and a minimum value at about 6 μm. The peak wavelength of about 1.5 to 2 μm of infrared rays emitted by a black body at 100 to 200 ° C. falls within a band where the transmittance of crystallized glass exceeds about 80%, so the peak emitted by the pan 501 at 100 to 200 ° C. Most of the infrared rays of the wavelength pass through the crystallized glass top plate 2 and the window material 15, and can go to the thermopile 12 in the infrared sensor module 407. On the other hand, since most of the wavelengths of 4 μm or more having a high heating effect among infrared rays radiated from the pan 501 are cut by the top plate 2, the inside of the main body 1 is prevented from being heated by infrared rays having a high heating effect. be able to.

  Next, the reflectance detection circuit 132 will be described in detail. The reflectance detection circuit 132 includes an infrared light emitting element 19 and an infrared light receiving element 20. The infrared light emitting element 19 is, for example, an infrared LED having an emission wavelength of 930 nm. For example, the infrared light receiving element 20 is a phototransistor having a peak sensitivity wavelength of 800 nm and a sensitivity at a wavelength of 930 nm of 80% of the peak sensitivity. The infrared light emitted from the infrared light emitting element 19 passes through the path 29, is reflected by the pan 501, and returns to the infrared light receiving element 20. In the infrared light receiving element 20, a voltage proportional to the amount of received infrared light is generated, and the amount of received infrared light can be known from the voltage value. That is, the reflectance detection circuit 132 can detect the reflectance ρ of the pan 501 from the ratio of the infrared light emission amount and the infrared light reception amount. Note that 930 nm is adopted as the emission wavelength of the infrared light emitting element 19 is the infrared light having a wavelength that transmits the top plate 2, the window material 15, and the infrared transmitting member 507, and is hardly included in the infrared light emitted from the pan 501. This is because the wavelength is infrared. Therefore, it can be determined that the 930 nm infrared ray received by the infrared light receiving element 20 is the infrared ray reflected by the pan 501, and the reflectance of the pan 501 can be accurately detected based on this infrared ray.

Here, a method in which the emissivity calculation circuit 26 calculates the emissivity based on the reflectivity obtained by the reflectivity detection circuit 132 will be described. Equation 2 is established according to Kirchhoff's law between the emissivity ε of the infrared energy (E = εσT ⁴ ) radiated from the surface of the metal material at the temperature T according to Kirchhoff's law (where the transmittance α = 0). And). That is, if the reflectance ρ of the pan 501 can be known, it can be understood that the emissivity ε of the pan 501 can be calculated based on Equation 3 obtained by modifying Equation 2.

ε + ρ = 1 (Formula 2)
ε = 1−ρ (Formula 3)

  When the emissivity ε is different, the infrared energy to be radiated is different even at the same temperature. Therefore, the temperature of the pan 501 can be uniquely determined from the infrared energy detected by the thermopile 12 in the thermal infrared detection circuit 131. There is a problem that you can not. In order to solve this problem, the control circuit 23 corrects the temperature of the pan bottom calculated by the temperature detecting means 131 using the emissivity ε calculated by the emissivity calculation circuit 26, so that the pan 501 having a different reflectance ρ. Even when using, detect the pan bottom temperature appropriately. Therefore, the control circuit 23 can suitably control the power supplied to the heating coil 200 based on the pan bottom temperature corrected using the emissivity ε.

  13B, the thermopile 12 included in the thermal infrared detection circuit 131 and the infrared light emitting element 19 and the infrared light receiving element 20 included in the reflectance detection circuit 132 are placed on the same printed wiring board 27. Adjacent to each other. When the pan bottom is dirty, the infrared reflectance and emissivity vary greatly depending on the location even in the same pan. In this embodiment, since the thermal infrared detection circuit 131 and the reflectance detection circuit 132 are provided on the same printed wiring board 27, the reflectance and emissivity near the pan bottom where the thermopile 12 observed the temperature can be obtained. The control circuit 23 can perform appropriate temperature correction using this emissivity. Moreover, since it is not necessary to adjust the position of the element on the printed wiring board 27, the assembly efficiency of the induction heating cooker can be increased.

  According to the induction heating cooker of the present embodiment described above, the temperature near the maximum temperature of the pan bottom can be detected, and the detected temperature based on the reflectance can be corrected appropriately. Furthermore, the temperature change to the infrared sensor can be reduced, and electromagnetic noise is also reduced, so that the pan temperature can be accurately detected, that is, the heating can be controlled using the accurately detected temperature. It becomes possible to cook.

DESCRIPTION OF SYMBOLS 1 Main body 2 Top plate 3a-3c Heating part 4 Intake port 5 Exhaust port 6 Grill heating part 7 Operation part 8 Display part 11 Air path 12 Thermopile 13 Magnetic shielding case 14 Opening part 15 Window material 16 Resin case 17 Thermistor 18 Cooling wind 19 Infrared Light emitting element 20 Infrared light receiving element 21 Amplifier 23 Control circuit 26 Emissivity calculation circuit 27 Printed wiring boards 31a to 31c Infrared transmission region 131 Thermal infrared detection circuit 132 Reflectance detection circuit 200 Heating coil 201 Inner peripheral heating coil 202 Outer peripheral heating Coil 203 Coil base 205 to 208 Thermistor 301 to 312 Ferrite core 403 to 405 High frequency power supply circuit 407 Infrared sensor module 501 Pan 502 Temperature detection circuit 508 Waveguide

Claims (8)

A top plate on which the pan is placed;
A heating coil provided below the top plate and configured by an inner peripheral coil and an outer peripheral coil;
A high frequency power supply circuit for supplying high frequency power to the heating coil;
An infrared sensor module provided below the gap between the inner and outer coils;
A temperature detection circuit for calculating the temperature of the pan based on the output of the infrared sensor module;
An emissivity calculation circuit for calculating the emissivity of the pan based on the output of the infrared sensor module;
A control circuit that corrects the temperature of the pan calculated by the temperature detection circuit using the emissivity of the pan calculated by the emissivity calculation circuit, and controls the high-frequency power supply circuit according to the corrected temperature; An induction heating cooker comprising: The induction heating cooker according to claim 1,
The infrared sensor module is
A thermopile detection circuit integrated with a thermopile that outputs a signal corresponding to the amount of infrared radiation emitted by the pan, and an amplifier that amplifies the signal output from the thermopile;
A reflectance detection circuit comprising: an infrared light emitting element that emits infrared light toward the pan; and an infrared light receiving element that receives infrared light reflected by the pan;
Is placed adjacent to the same printed wiring board,
The temperature detection circuit calculates the temperature of the pan based on the output from the thermal infrared detection circuit,
The said emissivity calculation circuit calculates the emissivity of the said pan based on the output of the said reflectance detection circuit, The induction heating cooking appliance characterized by the above-mentioned. The induction heating cooker according to claim 2,
The infrared sensor module is
Surrounding the printed wiring board, and a resin case having an opening above,
A window material having infrared transmission characteristics equivalent to the infrared transmission characteristics of the top plate;
An aluminum magnetic shielding case covering the outer shell of the resin case;
With
An induction heating cooker, wherein an opening of the resin case is sealed with the window material. In the induction heating cooker according to any one of claims 1 to 3,
The said infrared sensor module is provided in the position of 45-55 mm from the center of the said heating coil, The induction heating cooking appliance characterized by the above-mentioned. A top plate made of crystallized glass with a cooking vessel on top;
A heating coil provided under the top plate;
A high frequency power supply circuit for supplying high frequency power to the heating coil;
A thermopile for detecting the amount of infrared radiation emitted from the bottom of the cooking container;
A window material having the same optical characteristics as the top plate disposed on the light-receiving front surface of the thermopile;
A temperature detection circuit for detecting the bottom temperature of the cooking container from the thermopile output;
Infrared light emitting means for projecting the bottom surface of the cooking container and the bottom surface of the top plate in the vicinity of the thermopile, an infrared light receiving means for receiving reflected light from the bottom surface of the cooking container and the top plate, and an output of the infrared light receiving means, Temperature correction means for correcting the output, the thermopile, the infrared light emitting means, and the infrared light receiving means are arranged on the same printed wiring board, the printed wiring board is housed in a resin case, and the window material An induction heating cooker characterized by being sealed.   The induction heating cooker according to claim 5, wherein the resin case and the window material are housed in a magnetic shielding case.   The said magnetic-shield case has an opening part for guiding light through a window material, and each surface other than the said opening part is covered with the said magnetic-shield case. The induction heating cooker described.   The induction heating cooker according to claim 5, wherein the magnetic shielding case is made of a nonmagnetic material.

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