JP2015035333A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect pot temperature with high accuracy and stably and in a highly responsive and non-contact manner even in an environment of a wide temperature range and where temperature changes.SOLUTION: An induction heating cooker comprises: a top plate composed of crystallized glass, on a top face of which a cooking container is placed; a heating coil provided under the top plate, for generating an induction field to heat the cooking container; infrared detection means for detecting infrared rays radiated from a bottom of the cooking container and provided under the heating coil; and pot temperature detection means for detecting pot temperature from an output of the infrared detection means. The induction heating cooker further comprises, in addition to the infrared detection means: first temperature measurement means; second temperature measurement means; temperature compensation output calculation means for introducing a correction output from a temperature difference between the first and second temperature measurement means; and means for compensating for an output of the infrared detection means by the temperature compensation output.

Description

  The present invention relates to an induction heating cooker that detects a pan temperature using a thermopile disposed under a top plate.

  An induction heating cooker has a concentric induction heating coil (hereinafter abbreviated as “heating coil”) installed under a top plate made of crystallized glass, etc., and a high-frequency current is passed through the top heating plate. An eddy current is induced at the bottom of the pan, which is a cooking vessel placed on top, and the pan, which is a cooking vessel, is directly heated by this Joule heat.

  As a means for detecting the temperature of a pan in an induction heating cooker, there are many currently used devices that detect the temperature by observing the infrared rays emitted from the bottom of the pan heated at a good response speed with an infrared sensor through the top plate. . As this infrared sensor, a quantum type such as a photodiode or a thermal type sensor such as a thermopile is often used. This infrared sensor is placed near the center gap of the heating coil, the infrared radiation emitted from the bottom of the pan is detected by the infrared sensor through the top plate, the heating coil is driven according to the output, and the inverter circuit output is controlled. The cooking temperature is adjusted.

  However, there is little radiant infrared energy at cooking temperature (100 to 250 ° C), and furthermore, due to the optical characteristics of the top plate, the wavelength transmitted through the top plate is only about 2 μm with a width of 1 μm to 3 μm. Only 1-2% can pass through the top plate. For this reason, the sensitivity of the infrared sensor to be used is required to be one digit higher than that used in thermometers. Further, since the sensor output signal is a DC voltage, a DC amplification circuit having a high amplification factor is required. For this reason, these infrared sensors are very sensitive to fluctuations in ambient temperature, and the sensor output voltage fluctuates due to fluctuations in the temperature inside the machine during cooking, which greatly affects the accuracy of detecting the pot temperature.

  As means for solving this problem, Patent Documents 1 to 4 are listed.

  In Patent Document 1, a first detection unit (thermopile) that outputs a signal according to infrared incidence from a detection target and a second detection unit (thermopile) that outputs a signal according to infrared incidence from the surrounding environment. And the structure which is comprised by the differential amplifier which outputs the difference of the output signal of a 1st, 2nd detection part and detects only the infrared rays from a detection target is disclosed.

  In Patent Document 2, a container having an incident window through which infrared rays are incident, a first infrared detecting element (thermal infrared detecting element) disposed opposite to the incident window in the container, and a first infrared detecting element are mounted. And a second infrared detection element (thermal infrared detection element) for temperature-compensating the detection output of the first infrared detection element disposed in the container, and the infrared ray incident from the incident window is the substrate A configuration is disclosed in which the second infrared detection element is disposed at a position shielded by the above, and the reduction in detection accuracy due to a change in ambient temperature is suppressed.

  Patent Document 3 discloses an infrared temperature sensor that measures the temperature of a heat source in a non-contact manner, and is a light-sensitive element for detecting the amount of infrared radiation emitted from the heat source and a light-shielding device that detects the amount of heat from the external environment. A heat-compensating element for temperature compensation and a heat inflow / outflow part where heat flows in / out between the external environment and the infrared sensor are provided, and the heat conduction from the heat inflow part to the detecting element and the compensating element becomes substantially equal. A configuration that enables accurate temperature compensation is disclosed.

  Patent Document 4 relates to temperature detection means (thermopile) that detects the temperature of a measurement target member from the measurement target by the intensity of infrared rays, and correlates with the temperature of the opposing member facing the measurement target member or the temperature change of the opposing member. Compensating temperature measuring means for measuring the temperature of the temperature-changing member, and calculating means for correcting the detected temperature obtained by the temperature detecting means with the corrected temperature obtained by the correcting temperature measuring means, and infrared rays from the opposing member A configuration for measuring an accurate temperature without being affected by the above is disclosed.

JP 2007-85840 A JP-A-11-132857 JP 2011-75365 A JP 2004-191075 A

  In Patent Document 1, the difference between a first detection unit output to which infrared rays from a detection target and the surrounding environment (ambient temperature) are incident and a second detection unit output to which infrared rays from the surrounding environment are incident are amplified. The detection accuracy is improved by canceling output fluctuation due to infrared rays from the environment using a high CMRR (Common-Mode Rejection Ratio) of the differential amplifier. In Patent Document 1, it is assumed that the amount of infrared rays from the surrounding environment incident on the first detection unit is equal to the amount of infrared rays incident on the second detection unit. Further, it is assumed that the infrared detection sensitivity and temperature characteristics of each element are the same.

  However, in practice, it is difficult to equalize the infrared rays amount or temperature of each detection unit from the surrounding environment. In a specific circuit, a buffer amplifier is required before the differential amplifier. This is because the internal resistance (approximately 50 to 150 kΩ) of the thermopile is large, and this output resistance is reduced in a circuit to make the next differential amplifier operate normally. Furthermore, it is known that the output (sensitivity) characteristic of an infrared sensor varies by about 30% even if it is produced by the same process. For this reason, it is difficult to realize differential amplification with two element outputs. In the case of mass-produced products such as home appliances, it is necessary to suppress this variation by finely adjusting the amplification factor of the differential amplifier. As is well known, a differential amplifier cannot maintain a high CMRR unless the resistance ratio and value connected to the inverting input and the resistance ratio and value connected to the non-inverting input are the same. For this reason, the fine adjustment of the amplification factor for suppressing the sensitivity variation of the infrared sensor needs to maintain the high CMRR by adjusting the resistance value to the same value at two locations simultaneously. This is also difficult. As described above, the configuration of Patent Document 1 has a problem that it is difficult to realize a differential amplifier and the circuit cost is high.

  In Patent Document 2, a first infrared detection element and a second infrared detection element for temperature-compensating the output are assembled in the same container, and consideration is given to placing each infrared detection element in the same temperature environment. In addition, infrared rays are incident on the first infrared detecting element from the incident window, and infrared rays are not incident on the second infrared detecting element disposed on the back surface of the first infrared detecting element. The first infrared detection element (thermistor) and the second infrared detection element (thermistor) are connected in series, and the output signal at the connection point is amplified to compensate for temperature. In the case of the thermistor, the resistance value is determined by the ambient temperature, and in the case of the same structure, the resistance value is almost the same. Therefore, when these are connected in series and a constant voltage is applied, the voltage at the connection point is determined by the resistance ratio of the series elements, and therefore does not change with respect to changes in the ambient temperature. That is, temperature compensation is performed.

  However, in the configuration of Patent Document 2, there is a risk that infrared light from the incident window is reflected and stray in the container and enters the second infrared detection element. In order to prevent the incident, another countermeasure (for example, a countermeasure such as forming another light shielding wall in the container) needs to be performed on the second infrared detection element. Further, the temperature compensation that can be easily performed by connecting the elements in series is limited to a temperature sensitive resistance element such as a thermistor as described above. In addition, an example is also disclosed in which a Wien bridge is configured with the above-described series elements, and the output is differentially amplified to perform temperature compensation with higher accuracy. Other problems are the same as in Patent Document 1.

  In Patent Document 3, as in Patent Document 2, the infrared detecting thermal element and the light-shielded temperature compensating thermal element are placed in the same container so that heat transfer from the heat inflow / outflow site to the container is substantially uniform. The temperature compensation is performed by arranging (for example, a point-symmetrical position) and differentially amplifying the connection point between each element and the resistor. In Patent Document 3, as in Patent Document 2, it is necessary that the element be a temperature-sensitive resistance element that can be compensated by this amplification configuration. Other problems are the same as in Patent Document 1.

  In Patent Document 4, the thermopile is composed of a thermistor corresponding to a cold junction and a correction temperature sensor installed in the vicinity of the measurement target member, so that the temperature changes even if the ambient environment temperature of the thermopile and the measurement target member changes. Use the corresponding correction to improve detection accuracy. Since the thermopile is output in proportion to the temperature difference between the hot and cold junctions of the thermopile, the ambient temperature change of the thermopile can be corrected in Patent Document 4, but the ambient temperature of the thermopile is suddenly increased by blowing cooling air or the like. When the temperature fluctuates, a temperature difference occurs between the hot junction and the cold junction inside the thermopile, and the correction in Patent Document 4 in which only the cold junction temperature is measured cannot be handled. Further, since the correction temperature sensor is not arranged in the vicinity of the thermopile, it cannot cope with correction under an environment where the temperature of the thermopile itself changes suddenly. That is, temperature compensation is insufficient in an environment where the ambient temperature of the thermopile fluctuates rapidly, and there is a problem that the temperature detection accuracy of the measurement target member decreases.

  The above-mentioned Patent Documents 1 to 4 describe a change in temperature environment at the time of steady state, that is, when the changed environmental temperature becomes constant after a long time, if the amount of infrared rays from the detected object is the same, the temperature and change before the change. The temperature compensation is performed so that the output of the infrared sensor does not change even if the later temperature is different (with respect to the difference in environmental temperature). There is no mention of temperature compensation (transient) when the ambient temperature is changing gradually. In the case where the temperature gradually changes during cooking, such as an induction heating cooker, it is important to compensate for this transient temperature environment change.

  The present invention is a pan temperature detecting means using a thermopile as an infrared sensor, such as an induction heating cooker, even in a transient temperature environment in which the environmental temperature gradually changes and in a steady temperature environment, Induction heating cooker that eliminates the effects of infrared sensor output fluctuations, reduces infrared sensor output fluctuations even when the power is turned on, and enables stable and accurate detection of a wide range of pan bottom temperatures, improving safety and ease of use The purpose is to provide.

  The above-described problems include a top plate having a cooking container on the top surface, a heating coil provided under the top plate for induction heating the cooking container, an inverter circuit for supplying driving power to the heating coil, and the heating coil An induction heating cooker comprising: a pan temperature detecting device for detecting a pan temperature; and a microcomputer for controlling the inverter circuit based on an output of the pan temperature detecting device, wherein the pan temperature is In the detection device, infrared detection means for detecting infrared rays radiated from the bottom of the cooking container, a first temperature sensor for detecting a first ambient temperature, and a second for detecting a second ambient temperature. A temperature sensor, and the microcomputer is based on a temperature difference between the first ambient temperature detected by the first temperature sensor and the second ambient temperature detected by the second temperature sensor. Te, it can be solved by the induction heating cooker in which the infrared detecting device corrects the pot temperature detected.

  Further, a top plate on which the cooking container is placed, a heating coil provided under the top plate for induction heating the cooking container, an inverter circuit for supplying driving power to the heating coil, the heating coil, and the heating coil A cooling fan that supplies cooling air to the inverter circuit, an air passage that guides the cooling air from the cooling fan to the heating coil or the inverter circuit, and a pan temperature that is provided below the heating coil and in the air passage. A pan temperature detection device for detecting, an infrared detection means for detecting infrared rays radiated from the bottom of the cooking container, and the inverter circuit controlled based on the output of the pan temperature detection device A microcomputer, a first temperature sensor provided in the air passage for detecting a first ambient temperature, a second temperature sensor provided in the pan temperature detector, and a second atmosphere An induction heating cooker including a second temperature sensor for detecting an air temperature, wherein the microcomputer includes the first ambient temperature detected by the first temperature sensor and the second temperature sensor. It can also be solved by an induction heating cooker that corrects the pan temperature detected by the infrared detection device based on the detected temperature difference between the second ambient temperatures.

  According to the present invention, there is a pan temperature detecting means composed of an infrared detecting means and a DC amplifying means for outputting a DC voltage proportional to the amount of input infrared rays, like a quantum type such as a photodiode or a thermal type sensor such as a thermopile. In an induction heating cooker, the output of the infrared detecting means is stabilized against a temperature change (transient temperature change) inside the casing during cooking, and even if a temperature change occurs due to cooking inside the casing, An induction heating cooker that accurately detects the temperature can be provided.

  And the induction heating cooking appliance which enables safe and optimal cooking by controlling the high frequency electric power to a heating coil can be provided.

The perspective view which shows the structure of the induction heating cooking appliance of Example 1. FIG. Sectional drawing which shows the structure of the induction heating cooking appliance of Example 1. Sectional drawing which shows the detail of the right side heating coil periphery of Example 1 Sectional drawing which shows the detail of the left side heating coil periphery of Example 1. The top view which shows arrangement | positioning of the heating coil of Example 1, and a pan temperature detection apparatus. The top view which shows the back surface of the heating coil of Example 1 Plane and cross-sectional view of the pan temperature detecting device of Example 1 The figure which shows the reflection type photointerrupter of Example 1. Plane and sectional view showing details of thermopile for detecting pan infrared radiation of Example 1 Control block diagram of induction heating cooker of embodiment 1 The figure which shows the details of the conventional infrared detection circuit The figure which shows the temperature characteristic of the conventional infrared detection circuit output Experimental example showing output fluctuation when ambient temperature of conventional infrared detection circuit output changes The figure which shows the relationship between the temperature difference of the temperature sensor of Example 1, and sensor output V1. Flowchart of pan temperature detection of embodiment 1 Experimental example showing output fluctuation at the time of ambient temperature change of the infrared detection circuit output of Example 1 Sectional drawing of the pan temperature detection apparatus of Example 2 Sectional drawing of the pan temperature detection apparatus of Example 3 Sectional drawing which shows the detail of the right side heating coil periphery of Example 1 of Example 4

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a main body 1 of an induction heating cooker according to a first embodiment, and FIG. 2 is a schematic longitudinal sectional view when a cooking pan 7 is placed on a portion indicated by a one-dot chain line AA ′ in FIG. . In the following, there are 2 pans on the left and right where induction heating is possible, 1 pan on the side that can be heated by the radiant heat of a heater such as a radiant heater or halogen heater (heating source), induction cooking with a fish grill However, the object of application of the present invention is not limited to this, and for example, an induction heating cooker provided with three pan storage locations capable of induction heating may be used. The cooking pan 7 may be a magnetic iron pan suitable for induction heating, or may be a non-magnetic aluminum pan or copper pan.

  As shown in FIGS. 1 and 2, a top plate 2 formed of a nonmagnetic material such as crystallized glass is provided on the upper surface of the main body 1. Further, an operation display unit 3 is provided in front of the top plate 2 in which a switch for instructing heating start or heating course of each port and grill and a display for displaying the heating state (temperature, etc.) of each port are provided. ing. The final characters of the following symbols are R and L, respectively, indicating the parts below the right and left heating ports, and those without these characters indicate the common structural components on the right and left.

  On the upper surface of the top plate 2, a circle 4 having a radius that approximately matches the outermost radius of the heating coil 8 or the radiant heater disposed thereunder is printed to indicate a place where the pan can be heated. In addition, the top plate 2 is normally transparent to visible light, so the upper surface is coated with heat-resistant and durable design with heat-resistant paint mixed in the frit glass, and the lower surface is coated with a heat-resistant surface so that the inside of the device cannot be seen. It is. An infrared transmitting window 5 that is not printed or painted for detecting the pot temperature described later is provided at a position shifted by about 50 mm from the center of the circle 4 at the two pot setting places where induction heating is possible. This infrared transmission window 5 is for transmitting infrared light, and a visible light cut member (heat-resistant film or glass) that is transparent to infrared light only on this portion may be attached to the lower surface.

  A cooking pan 7 is placed in each mouth (circle 4) on the upper surface of the top plate 2 and cooking is performed. As shown in FIG. 2, when a high frequency current is supplied to the heating coil 8 from the inverter circuit 9 (high frequency current supply means), the heating coil 8 is divided into a first coil 8a on the outer peripheral side and a second coil 8b on the inner peripheral side. The heating coil 8 generates a high-frequency magnetic field 10 (indicated by a broken line in the figure), and this high-frequency magnetic field is linked to the pan 7 to generate an eddy current. The cooking pan 7 itself is induction-heated by the Joule heat to generate heat. . Accordingly, the food in the cooking pan 7 is cooked by the heat generated by the cooking pan 7 itself. At this time, the top plate 2 under the cooking pan 7 also becomes high temperature due to heat transfer or radiant heat from the cooking pan 7 that has generated heat.

  An inverter circuit 9 is disposed below the right heating coil 8R on the right side of the top plate, and a grill cabinet 6 is disposed on the left side and below the left heating coil 8L. In the grill cabinet 6, tube heaters 6a and 6b are arranged one above the other so that grilled fish and the like can be cooked.

  FIG. 3 shows a cross section around the right heating coil 8R in detail. As shown in FIG. 3, a heating coil 8 divided by a coil gap 8c between the first coil 8a on the outer peripheral side and the second coil 8b on the inner peripheral side is made of heat-resistant plastic on the lower surface of the top plate 2. The coil base 10 is disposed by being concentrically wound (spiral). Below the heating coil 8, U-shaped ferrites 11 are radially arranged inside the coil base member with the convex portions up. The ferrite 11 is arranged to efficiently guide the magnetic flux generated by the heating coil 8 to the cooking pan 7 which is a cooking container on the top plate 2. Further, the magnetic flux is prevented from leaking to the lower part of the coil base 10. This is because the ferrite 11 has a high magnetic permeability and almost all the magnetic flux passes through the ferrite 11.

  A coil cooling air passage 15 for cooling the heating coil 8 is installed under the coil base 10. The coil cooling air passage 15 is divided into two, one is connected to the inner peripheral side of the first coil 8a, and the coil upper surface cooling air passage 15a for cooling the upper surfaces of the second coil 8b and the first coil 8a, The other one is a coil lower surface cooling air passage 15b for cooling the lower surface of the first coil 8a. On the upper surface of the coil upper surface cooling air passage 15a located below the center portion of the coil base 10, a circular coil upper surface cooling air sending hole 15c is opened.

  The central portion of the coil base 10 is a cylindrical inner cavity 14a, and an inner peripheral side of the first coil 8a is a cylindrical outer cavity wall 14b connected to a radial beam incorporating the ferrite 11. . A coil upper surface cooling air sending hole 15c of the coil upper surface cooling air passage 15a is connected to the lower portion of the outer cavity wall 14b. A sealing material 16 such as glass wool is provided around the coil upper surface cooling air sending hole 15c and connected to the outer cavity wall 14b.

  Below the cooling air passage 15 to the right heating coil 8R, circuit cooling air passages 17a and 17b containing a circuit board such as an inverter circuit 9 are provided in two layers, and the right and left heating coils 8L and 8R are respectively stacked. An inverter circuit 9 and the like are incorporated. These cooling air passages are fixed to the main body 1.

  The coil base 10 is pressed by the spring 13 from the three coil base receivers 12 fixed to the coil lower surface cooling air passage 15b or the circuit cooling air passage 17a, and is pressed against the lower surface of the top plate 2.

  A pan temperature detecting device 18 is disposed in the coil upper surface cooling air passage 15a below the coil cooling air delivery hole 15c. The pan temperature detection device 18 detects the bottom surface temperature of the cooking pan 7 heated by induction from the infrared rays transmitted through the infrared transmission window 5 of the top plate 2.

  During cooking, outside air is introduced from a fan (not shown) built in the main body 1 into the coil upper surface cooling air passage 15a, the coil lower surface cooling air passage 15b, and the circuit cooling air passages 17a, 17b. However, since the cooling air is warmed by the heat generated by the inverter circuit power element, the heat generated by the ferrite 11, and the heat generated by the heating coil 8 itself, the ambient temperature of the pan temperature detecting device 18 increases with time. When cooking is finished, the ambient temperature decreases with time. The cooling air flowing in the coil upper surface cooling air passage 15a raises the coil gap 7c and the inner cavity 14a in the cylindrical outer cavity wall 14b from the coil upper surface cooling air sending hole 15c while cooling the pan temperature detecting device 18, and the coil From the gap 8c and the upper portion of the inner cavity 14a, the top plate 2 blocks the flow between the top plate 2 and the heating coil 8, and the upper surface of the heating coil 8 and the lower surface of the top plate 2 are cooled. A plurality of small holes are formed in a portion corresponding to the lower surface of the coil 8a of the coil lower surface cooling air passage 15b, and the cooling air flowing through the coil lower surface cooling air passage 15b is jetted from here toward the lower surface of the coil 8a to cool it. .

  FIG. 4 shows a detailed cross section around the left heating coil 8L. The heating coil 8, the coil base 10, the cooling air passage, and the coil base support structure are the same as in FIG. An upper pipe heater 6a and a lower pipe heater 6b are arranged inside the grill cabinet 6, and a net plate 6c is fixed therebetween, and a cooked food (fish or the like) is placed here to cook the grilled food. When grilled food is cooked in the grill cabinet 6, the upper surface of the grill cabinet 6 and the lower surface of the coil upper surface cooling air passage 15a of the heating coil 8L are in a high temperature state. This temperature heats the lower surface of the pan temperature detector 18L.

  FIG. 5 shows details of the top view of FIG. 3 excluding the top plate 2. It is a detailed block diagram of the heating coil 8, the coil base 10, and the coil upper surface cooling air path 15a. The positional relationship in the horizontal surface of the heating coil 8, the inner cavity 14a, and the pan temperature detection apparatus 18 is shown.

  The heating coil 8 is concentrically wound in the same direction with a litz wire that is insulated with Teflon (registered trademark) or the like, and is divided into a first coil 8a on the outer peripheral side and a second coil 8b on the inner peripheral side. The The gap 8c has a concentric band shape with a width of about 15 mm, and the winding end of the first coil 8a bridges the gap 8c to start winding of the second coil 8b. The first coil 8a, the bridging wire 8d, The heating coil 8 is constituted by the coil 8b. The coil base 10 is provided with a cylindrical outer cavity wall 14b on the inner peripheral side of the first coil 8a, and the inside thereof is a coil gap portion 8c. An inner cavity 14a is provided on the inner peripheral side of the second coil 8b. Furthermore, a cylindrical sensor visual field cylinder 19 is provided between a portion of the coil gap portion 8 c and the two radially arranged ferrites 11, and a pan temperature detecting device 18 is installed under the sensor visual field cylinder 19.

  In the heating coil 8 wound concentrically in the embodiment, the induction magnetic field in the vicinity of the center of the winding width is the strongest, and when the pan is induction-heated, the temperature at the center portion of the winding width becomes the highest. The reason why the heating coil 8 is divided into two is that a pan temperature detection device 18 is provided under the division gap to detect the pan temperature of this high temperature portion.

  A thermistor 20 is installed on the upper side of the sensor visual field cylinder 19 so as to be in contact with the lateral lower surface of the infrared transmission window 5 of the top plate 2.

  Infrared rays from the bottom of the pan heated by induction pass through the infrared transmission window 5 of the top plate 2 and enter the thermopile (thermocouple) 25 built in the pan temperature detecting device 18 described in detail later from the sensor field tube 19. To do.

  FIG. 6 shows a view of the heating coil 8 of FIG. The coil base 10 is provided with two coil terminals 21a and 21b, the low voltage terminal 21a is connected to the start of winding of the first coil 8a, and the high voltage terminal 21b is connected to the end of winding of the second coil. Is done. The output lines 22a and 22b of the inverter circuit 9 are fixed to the terminals with screws. In a non-magnetic pot such as copper or aluminum, a high voltage output line 22b that outputs a high voltage of 4 to 5 kV is connected to a high voltage terminal 21b.

  As described with reference to FIGS. 5 and 6, the pan temperature detecting device 18 avoids the vicinity of the bridge line 8d and is disposed in the coil gap portion 8c located at a position away from the high voltage terminal 21b to which the high voltage output line 22b is connected. The case window 30 is installed under the sensor field cylinder 19 provided. The reason for avoiding the installation in the vicinity of the bridge line 8d is to prevent the magnetic field here from being disturbed and the magnetic field further leaking to the lower part, and heating the metal case 32 for electromagnetic shielding of the sensor case described later.

  The structure described in FIGS. 5 and 6 is the same for the left and right heating coils. In order to distinguish left and right, the last character of the code is indicated by R and L. For example, 8R indicates a right side heating coil and 8L indicates a left side heating coil. A part of the right cooling air flows through the left cooling air passage. However, it is obvious that an independent intake fan may be provided on the left side to separate the air flowing in the left and right cooling air passages.

  FIG. 7 shows details of the pan temperature detecting device 18. FIG. 7A shows a plan view of the pan temperature detecting device 18. The pan temperature detection device 18 is mainly composed of an infrared sensor (thermopile 25) to which infrared rays radiated from the bottom of the cooking container are incident and a reflective photo interrupter 26.

  The thermopile 25 and the reflection type photo interrupter 26 are arranged on an electronic circuit board 27 on which an infrared detection circuit 72 and a reflectance detection circuit 73 for amplifying the output signal of the thermopile 25 are mounted, and the infrared detection thermopile 25 and the reflection type interrupter 26 are mounted. The photo interrupter 26 and the electronic circuit board 27 are hermetically sealed in an infrared sensor case 28 (indicated by a one-dot chain line) made of a plastic member. The thermopile 25 and the reflective photo interrupter 26 are installed on the substrate 27 so as to look inside the sensor visual field cylinder 19.

  The electronic circuit board 27 is provided with a first temperature sensor 40 for measuring the ambient temperature above the board. The first temperature sensor 40 is disposed in the vicinity of the thermopile 25 and detects a temperature corresponding to a hot junction of the thermopile 25. The electronic circuit board 27 is also provided with a second temperature sensor 41 for measuring the ambient temperature on the back surface of the board. The second temperature sensor 41 is disposed on the back surface of the thermopile 25 and detects a temperature corresponding to the cold junction of the thermopile 25. Further, the electronic circuit board 27 includes a temperature detection circuit (temperature sensor temperature detection circuit for hot contact) 76 for the first temperature sensor 40 and a temperature detection circuit (temperature sensor for cold junction) for the second temperature sensor 41. A temperature detecting circuit 77 is arranged.

  The infrared sensor case 28 is provided with a case window 30 for transmitting infrared rays. Crystallized glass having almost the same optical characteristics as the crystallized glass constituting the top plate 2 is cut into a thin square in the case window 30. Is fitted as a crystallized glass optical filter 31.

  A thermopile 25 and a reflective photo interrupter 26 are mounted on an electronic circuit board 27 under the crystallized glass optical filter 31. The infrared sensor case 28 is covered with a metal case 32 (indicated by a two-dot chain line) having a permeability of approximately 1 such as aluminum. Naturally, the previous case window 30 is opened. Further, the aluminum metal case 32 is covered with an outer infrared sensor case 33 made of a plastic member. Of course, the previous case window 30 is opened. That is, the thermopile 25 is covered with a triple case.

  The pan temperature detecting device 18 configured as described above is installed in the coil upper surface cooling air passage 15a so that the case window 30 desires the inside of the sensor visual field cylinder 19 of the coil base 10.

  FIG. 7B shows a cross-sectional view along the line AA ′ in FIG. This is because the thermopile 25 and the reflective photo interrupter 26, the first temperature sensor 40, the second temperature sensor 41, and the infrared sensor case 28 that are mounted on the electronic circuit board 27 installed in the infrared sensor case 28. 30 is a cross-sectional view showing the positional relationship with the crystallized glass optical filter 31. FIG.

  In the present embodiment, an example in which the first temperature sensor 40 and the second temperature sensor 41 are arranged on the electronic circuit board 27 will be described. However, the application target of the present invention is not limited to this, and the first temperature sensor 40 is It arrange | positions in the vicinity of the thermopile 25, and detects the temperature corresponded to the hot junction of the thermopile 25. The second temperature sensor 41 may be disposed on the back side of the substrate and may detect the temperature corresponding to the cold junction of the thermopile 25. The reason why the thermopile 25, the first temperature sensor 40, and the second temperature sensor 41 are built in the same case is to match the ambient temperature conditions of these elements as much as possible.

  FIG. 8 shows details of the reflective photo interrupter 26. The reflection type photo interrupter 26 is obtained by molding an infrared LED 50 as an infrared light emitting element and an infrared phototransistor 51 as an infrared light receiving element on the same plastic member. A lens is made of plastic on the light emitting surface of the infrared LED 50, and infrared light near 930 nm is irradiated upward with a thin beam. A lens is made of visible light blocking plastic on the light receiving surface of the infrared phototransistor 51, and the reflected infrared light at the object (pan bottom) of the previous irradiated infrared light is received with a narrow viewing angle, and the amount of received light A current proportional to is output. This reflection type photo interrupter 26 is composed of a pair of an infrared light emitting element and a light receiving element, and measures the reflectance of the bottom surface of the cooking pan 7 placed on the top plate 2.

  The light emitting and receiving portions on the front surface of the reflective photointerrupter 26 are arranged immediately below the lower surface of the crystallized glass optical filter 31. This is to prevent infrared light from being reflected and received by the crystallized glass optical filter 31 directly above.

  Infrared light emitted from the infrared LED 50 passes through the crystallized glass optical filter 31 by 85% or more, but the remaining 15% is reflected and received by the adjacent infrared phototransistor 51. If there is a gap of several millimeters between the top (light emitting and light receiving surface) of the reflective photo interrupter 26 and the crystallized glass optical filter 31, the above-mentioned reflection is received and is reflected on the originally intended top plate 2. Affects the reception of reflected light at the bottom of a pan. For this reason, in this embodiment, as shown in the figure, the distance between the crystallized glass optical filter 31 and the light emitting / receiving surface of the reflective photointerrupter 26 (infrared LED 50 and infrared phototransistor 51) is brought close to within 500 μm, The infrared phototransistor 51 prevents light from being reflected from the crystallized glass optical filter 31 of the emitted infrared rays. Ideally, the lower surface of the crystallized glass optical filter 31 and the upper surface of the reflective photointerrupter 26 are preferably brought into contact with each other.

  FIG. 9 shows details of the thermopile 25 for detecting infrared rays. FIG. 9A shows a perspective view of the thermopile 25. 9B is a cross-sectional view of the thermopile 25 taken along the line BB ′ in FIG. 9A, and FIG. 9C is the line taken along the line CC ′ in FIG. 9B. It is a top view of a cross section. Here, the infrared absorption film is omitted so that the thermocouple can be seen.

  The thermopile 25 has a large number of thermocouples (thermocouples) connected in cascade (piling), and is incorporated in a metal case made of a metal can 25-1 such as a nickel-plated steel plate and a metal stem 25-2. A silicon oxide film 25-5 is formed on the surface of the silicon substrate 25-4 having a thickness of about 300 μm to electrically and thermally insulate, and polysilicon and aluminum are sequentially deposited on the silicon oxide film 25-5 to form a polysilicon deposited film 25-9. A large number of thermocouples are formed with the aluminum vapor deposition film 25-10, and these are connected in cascade. An infrared absorption film 25-3 such as a rubidium oxide film or a polyimide film close to a black body is formed as a protective film at the center of the silicon substrate 25-4 having a polysilicon / aluminum junction (temperature measuring contact). One end of the polysilicon vapor-deposited film 25-9 and the aluminum vapor-deposited film 25-10 is a cold junction portion 25-6, which is disposed around the silicon substrate 25-4. The back surface of the silicon substrate 25-4 is etched to 290 μm, leaving the periphery (cold junction portion), and the thickness of the silicon substrate 25-4 having the temperature measuring contact portion is formed to 10 μm. This is because by thinning silicon having good thermal conductivity, the heat conduction of the temperature measuring contact portion 25-8 and the cold junction portion 25-6 is reduced, and the temperature measuring contact portion 25-8 and the cold junction portion 25-6 are heated. This is to insulate.

  The silicon substrate 25-4 is fixed to the metal stem 25-2 with a bond or the like. At the same time, an NTC thermistor 25-11 formed on a ceramic is similarly arranged on the metal stem 25-2. This is to detect the ambient temperature of the thermocouple in the metal case and correct the thermoelectromotive force of the thermocouple. Details of this will be described later. Four metal pins 25-12, which are insulated and sealed, are disposed through the metal stem 25-2, and the output of the previous thermocouple and the NTC thermistor 25-11 are wire-connected to the metal pin 25-12. . A cylindrical metal can 25-1 is placed on and welded to the metal stem 25-2 in an inert gas such as nitrogen. A small hole window 25-13 is formed on the upper surface of the metal can 25-1, and a glass lens 25-14 is attached thereto from the inside.

  The silicon base material 25-4 is fixed so that the temperature measuring contact portion 25-8 (under the infrared absorbing film 25-3) is positioned below the small hole. The glass lens 25-14 is designed so that the visual field range of the infrared transmission window 5 forms an image on the infrared absorption film 25-3. This is to narrow the visual field characteristics of the thermopile 25 and increase the light collection efficiency.

  The thermocouple temperature measuring contact 25-25 (below the infrared absorbing film 25-3) in the thermopile 25 is heated by infrared rays that pass through the small hole window 25-13 and are condensed by the glass lens 25-14. This heating temperature rise is proportional to the infrared energy that has passed, and a voltage proportional to the temperature difference between the cold junction 25-6 and the temperature measuring contact 25-8 of the thermocouple is applied to the metal pin 25-12 of the thermocouple output. Is output.

  The control block diagram of the induction heating cooking appliance of a present Example is shown in FIG. The microcomputer 60 controls the operation of the induction heating cooker. In the following, symbol R represents a block relating to the induction heating port located on the right side in FIG. 1, and symbol L represents a block relating to the induction heating port located on the left side in FIG. The two inverter circuits 9R and 9L supply high-frequency current to the heating coils 8R and 8L. The frequency control circuits 61R and 61L and the power control circuits 62R and 62L adjust the operating frequency of the inverter circuits 9R and 9L and the power supplied to the coils. The reason for changing the operating frequency is that the induction heating efficiency changes at the frequency of the high-frequency current depending on the metal type of the pan. In general, a frequency of 20 kHz is used for iron, copper having a lower resistivity than this, and a frequency of 70 kHz or more is used for aluminum. This frequency switching is performed by the microcomputer 60 controlling the frequency control circuit 61 based on the judgment of the pan type discrimination means (not shown).

  A DC voltage is supplied from the rectifier circuit 63 to each of the inverter circuits 9R and 9L. The rectifier circuit 63 is connected to a commercial power supply 65 having three terminals 200V via a power switch 64. The ground terminal of the commercial power supply is connected to the metal part of the main body 1 with a ground wire. A commercial power supply 65 is connected to the radiant heater 66 through a radiant heater circuit 67, and the radiant heater circuit 67 controls power supplied to the radiant heater 66. Further, a commercial power supply 65 of 3 terminals 200V is connected to the upper grill heater 6a and the lower grill heater 6b via a grill heater control circuit 68. The grill heater control circuit 68 controls the power supplied to the upper grill heater 6a and the lower grill heater 6b.

  The microcomputer 60 is connected with an operation switch 69 and a display circuit 70 of a display / operation unit, and accepts a user's operation instruction and displays an operation state of the device. Further, a buzzer 71 is connected to notify a user of an operation button press or a warning such as an error. The microcomputer 60 controls the frequency control circuits 61R and 61L, the power control circuits 62R and 62L, the radiant heater circuit 67, and the grill heater control circuit 68 according to the instructions of the user, and the cooking pan 7 or grill box on the top plate 2 is controlled. 6 is heated.

  The thermopile 25 is connected to the infrared detection circuit 72 so that the output of the thermopile 25 is amplified and input to the AD terminal of the microcomputer 60. The photo interrupter 26 is connected to the reflectance detection circuit 73, the light emission of the light emitting element is controlled by the port output of the microcomputer 60, the infrared light reflected by the cooking pan 7 is received by the light receiving element, and the output signal is amplified. And input to the AD terminal of the microcomputer 60. Details of operations of the infrared detection circuit 72 and the reflectance detection circuit 73 will be described later. Further, the thermistor 20R is connected to the thermistor temperature detection circuit 74R, and its output is input to the AD terminal of the microcomputer 60. Similarly, the thermistor 20L is also connected to the thermistor temperature detection circuit 74L, and its output is also input to the AD terminal of the microcomputer 60. These detect the temperature of the top plate 2.

  The output of the first temperature sensor 40 installed on the thermopile 25 side of the electronic circuit 27 is converted into temperature information by a temperature detection circuit (temperature sensor temperature detection circuit for hot junction) 76 and then the AD terminal of the microcomputer 60. Is input. The output of the second temperature sensor 41 disposed on the back surface of the electronic circuit 27 is converted into temperature information by a temperature detection circuit (cold junction temperature sensor temperature detection circuit) 77 and then input to the AD terminal of the microcomputer 60. The The microcomputer 60 outputs the first temperature sensor 40 and the second temperature sensor 41 from the outputs of the temperature detection circuit (temperature sensor temperature detection circuit for hot junction) 76 and the temperature detection circuit (temperature sensor temperature detection circuit for cold junction) 77. A correction voltage corresponding to the temperature difference is derived, and the output detected by the thermopile 25 is corrected. These are temperature correction operations, and this processing method will be described later.

  Further, the microcomputer 60 knows the infrared reflectance of the cooking pot 7 from the output of the reflectance detection circuit 73 and corrects it with the reflectance to detect the temperature of the cooking pot 7. This process is also performed by the software of the microcomputer 60. And it converts into pan temperature with the temperature conversion table (The relationship between the output voltage of the infrared detection circuit 72 and pan temperature) created beforehand.

  The microcomputer 60 controls heating of the cooking pan 7 via the power control circuit 62 based on the pan temperature. Details of this processing method will be described later.

  FIG. 11 shows details of a conventional infrared detection circuit 72. Thermopile output (thermoelectromotive force) of thermopile 25 (voltage between symbols (+) and (-) in the figure) is amplified about 3000 times by an operational amplifier (hereinafter abbreviated as OP amplifier) 72-1, and output terminal 7-2 and input to the AD terminal of the microcomputer 60. The amplification factor G of the OP amplifier 72-1 is determined by the resistors R1 and R2 (amplification factor G = (R2 / R1 + 1)).

  The NTC thermistor 25-11 in the thermopile 25 is connected in series with a resistor R8 to a voltage source (both ends of the resistor R6) obtained by dividing the circuit power supply voltage Vcc (= 5V) by the resistors R5, R6, and R7. Is done. A connection point (shown by a in the figure) with the resistor R8 is connected to an input of a buffer amplifier (voltage follower) constituted by an OP amplifier 72-3, and the voltage at the connection point a is directly output from the OP amplifier 72-3. Appear in The voltage at the point indicated by b in this figure (the output of the OP amplifier 72-3) is applied to the connection point of the resistor R1 and the thermocouple output terminal (-) as the bias voltage Vbias of the OP amplifier 72-1. The output impedance of the buffer amplifier constituted by the OP amplifier 72-3 is almost zero, and the bias voltage Vbias (same as the voltage at the connection point a) that is the output of the OP amplifier 72-3 is used as an ideal voltage source. To -1. The OP amplifier 72-1 uses the Vbias value as an operation reference voltage (value when the output voltage of the thermopile 25 is zero), and the thermocouple output of the thermopile 25 (DC voltage between (+) and (−) symbols in the figure). Is multiplied by G = (R2 / R1 + 1) and added to the Vbais value for output. The Vbias value is designed to be 0.5 V as a resistance value of the NTC thermistor 25-11 at a temperature of 25 ° C. The bias voltage Vbais value offset by 0.5 V from the zero voltage is used for detecting the failure of the infrared detection circuit 72. If the operational amplifier 72-1 is broken, the output terminal 72-2 is opened, or the output terminal 72-2 is short-circuited to the power supply VCC or circuit ground, the voltage read by the microcomputer 60 is different from 0.5 V. .

  In the circuit diagram shown in FIG. 11, the electronic circuit board 27 in which both ends of R6 are short-circuited so that the temperature resistance value change of the NTC thermistor 25-11 does not affect the Vbias value, and the amplification factor G of the OP amplifier 72-1 is set to 2700. 7, the infrared detector circuit 72 shown in FIG. 11 was mounted on the pan temperature detector 18 shown in FIG. 7, and the output of the OP amplifier 72-1 was measured while varying the temperature inside the thermostatic bath.

  FIG. 12 shows sensor output fluctuations when the temperature of the pan temperature detecting device is changed from about 25 ° C. to 40 ° C. in the thermostat. In the induction heating cooker, the ambient temperature gradually rises when the pan is heated and the heat of the inverter circuit power element, the heat of the ferrite 11, and the heat of the heating coil 8 is included in the infrared detection circuit 72. For example, the cooling air to 18 is warmed. Moreover, in the state which is heating with the grill warehouse 6, in addition to the above-mentioned, the bottom face of the pan temperature detection apparatus 18 is warmed largely. This is a result of simulating this gradually warming in a thermostatic bath.

  When the ambient temperature changes, the sensor output dip greatly (0.5V is reduced to 0.2V by about 0.2V output), and after reaching 40 ° C for a sufficient time, the design bias voltage Vbias = 0.5V. That is, it can be seen that the output voltage is the same under steady conditions of ambient temperature of 25 ° C. and 40 ° C., and temperature compensation in the steady state is performed by the thermistor 25-11. However, it can be seen that the sensor output changes greatly in a transient state where the temperature changes. When cooking with an induction heating cooker, as described above, the ambient temperature of the pan temperature detecting device 18 changes every moment. When the pan temperature is detected in this state, the fluctuation becomes a pan temperature detection error in the process of converting the output voltage of the infrared sensor described above into the pan temperature. Details will be described later.

The cause of the output fluctuation is due to the structure of the sensor element (see FIG. 9). The output fluctuation at the time of temperature change is explained by the heat transfer delay from the cold junction part 25-6 to the temperature measurement junction part 25-8. The cold junction 25-6 is on bulk silicon, and the temperature measuring junction 25-8 is on a 10 μm silicon film and a 10 μm silicon oxide film. For this reason, the cold junction 25-6 becomes the same as the ambient temperature of the metal stem 25-2 and the metal can 25-1 in a relatively short time, but the temperature measuring junction 25-8 is delayed for a long time because of the heat transfer delay. Thus, the ambient temperature of the metal can 25-1 is reached. Now, if there is no infrared incidence, the temperature of the cold junction 25-6 is T1, and the temperature of the temperature measuring junction 25-8 is T2, T2 is a heat transfer coefficient proportional to the temperature difference (T1-T2) T1 The temperature rises with a delay, and the same temperature T1 = T2 is obtained after a long time. In the thermopile used in the experiment, the same temperature is reached after several tens of minutes as shown in FIG. In such a transient state where the ambient temperature is changing, the temperatures of the cold junction portion 25-6 and the temperature measuring contact portion 25-8 are different, and a voltage is generated at both ends of the thermocouple, that is, the thermopile 25 terminals. This is amplified by the amplification circuit and output to the output terminal 72-2 of the infrared detection circuit 72. While the ambient temperature rises, T1 reaches the ambient temperature relatively quickly, but T2 delays to the ambient temperature as described above. Therefore, during the rise, T1> T2 and a negative voltage is output. On the contrary, if the ambient temperature is decreasing, the temperature decrease of T2 is delayed, and T2> T1, and a positive voltage is generated. (The thermopile 25 outputs a voltage proportional to (T2-T1) to the (+) terminal with respect to the (-) terminal.)
In such a state, when the pan temperature on the top plate 2 is detected, the voltage fluctuation becomes an error in detecting the infrared radiation from the pan, and the pan temperature detection accuracy is deteriorated.

  FIG. 13 shows the sensor output when the ambient temperature of the pan temperature detecting device 18 changes in the main body 1 and the measured temperature difference obtained by subtracting the second temperature sensor 41 from the first temperature sensor 40. The measurement condition of this data is a result of changing the cooling air temperature for cooling the inside of the main body 1 without heating the cooking pan 7.

  The sensor output decreases in the transition period of the process in which the ambient temperature rises (25 → 40 ° C.), and when the temperature rise stabilizes at 40 ° C., the operation returns to the bias voltage Vbias = 0.5V. (This operation is the same as in FIG. 12) The sensor output increases in the transitional period of the process of lowering the ambient temperature (40 → 25 ° C.) and returns to the bias voltage Vbias = 0.5V when the temperature stabilizes at 25 ° C. I take the. The cause of the sensor operation so far is as described above with reference to FIG.

  Next, in this embodiment, an operation when the ambient temperature changes will be described with the difference obtained by subtracting the temperature of the second temperature sensor 41 from the first temperature sensor 40 as the temperature difference of the temperature sensor. When the ambient temperature rises, the temperature difference of the temperature sensor decreases to a negative temperature, and when the temperature is stabilized at 40 ° C., the temperature difference of the temperature sensor returns to zero. When the temperature falls, the temperature difference of the temperature sensor increases to a positive temperature, and when the temperature stabilizes at 25 ° C., the temperature difference of the temperature sensor returns to zero.

  Further, the peak points of the sensor output fluctuation at the time of temperature rise and fall coincide with the peak discharge of the temperature difference of the temperature sensor, and when the ambient temperature of the pan temperature detecting device 18 changes, the fluctuation of the sensor output and the temperature of the temperature sensor. An operation in which the fluctuation of the difference is interlocked occurs.

  As described above, the thermopile 25 changes the output of the temperature of the cold junction portion 25-6 by T1 and the temperature of the temperature measuring contact portion 25-8 by the temperature difference of T2 due to the ambient temperature fluctuation. When the measured temperature of the first temperature sensor 40 is Th1 and the measured temperature of the second temperature sensor 41 is Th2, the relationship of (Th1-Th2) ≈ (T2-T1) is established. Therefore, the measured temperature Th1 of the first temperature sensor 40 corresponds to the temperature T2 of the temperature measuring contact 25-8, and the measured temperature Th2 of the second temperature sensor 41 corresponds to the temperature T1 of the cold junction 25-6. Accordingly, the output of the thermopile 25 fluctuates in proportion to (Th1-Th2).

  FIG. 14 shows a correlation graph of the temperature difference (Th1-Th2) of the temperature sensor, where the sensor output of FIG. 13 is V1. The temperature difference of the temperature sensor and the sensor output V1 can be expressed by a proportional relationship. The sensor output V1 corresponding to the temperature difference of the temperature sensor is registered in the microcomputer 60 and used in the temperature correction process of the thermopile 25 described below.

  FIG. 15 shows a temperature correction flow for correcting the sensor output due to the ambient temperature fluctuation of the pan temperature detecting device 18. Infrared light from the cooking pan 7 is output from the output of the thermopile 25 to the infrared detection circuit 72 and amplified, and the operation of taking the output result V0 into the microcomputer 60 is referred to as a thermopile output measurement 80. The output measured by the first temperature sensor 40 is converted into a temperature output by a temperature detection circuit (temperature sensor temperature detection circuit for a hot junction) 76, and is taken into the microcomputer 60 to convert Th1. The output measured by the second temperature sensor 41 is converted into a temperature output by a temperature detection circuit (cold junction temperature sensor temperature detection circuit) 77, and taken into the microcomputer 60 to convert Th2. In the Th1-Th2 temperature difference measurement 81, the microcomputer 60 determines the temperature difference Th1-Th2. From the result of the Th1-Th2 temperature measurement 80, a Th1-Th2 correction voltage V1 calculation 82 is performed. In this process, the sensor output V1 appropriate for the temperature difference of the temperature difference measurement 81 of Th1-Th2 is calculated from the correlated data of the temperature difference of the temperature sensor and the sensor output V1 shown in FIG.

  The thermopile output V0 measurement 80 and the processing result of the Th1-Th2 correction voltage V1 calculation 82 are subjected to temperature correction processing by the thermopile output V2 calculation 83 after temperature change correction. In this processing step, a correction formula of thermopile output V2 = thermopile output V0−correction voltage V2 is used. Next, the temperature of the cooking pan 7 is calculated from the result of the thermopile temperature correction flow 84 in a pan temperature conversion 85.

  FIG. 16 shows the result of the corrected thermopile output V2 processed in the thermopile temperature correction flow 84 of FIG. 15 by changing the ambient temperature of the pan temperature detecting device 18 by changing the cooling air temperature in the main body 1. The thermopile output V0, which is the output result of the thermopile output measurement 80, varies as the ambient temperature rises (25 → 40 ° C.) and falls (40 → 25 ° C.). The thermopile output V2 obtained by the thermopile output V2 calculation 83 after the temperature change correction is stabilized even when the ambient temperature changes due to temperature rise and fall. If the thermopile output V2 at the start of temperature change is bias voltage Vbias = 0.5V, even if the ambient temperature of the pan temperature detecting device 18 changes transiently, it will be maintained at about 0.5V.

  When the pan temperature on the top plate 2 is detected in such a state, the pan temperature detection can be accurately measured by detecting the infrared radiation from the pan regardless of the ambient temperature change of the pan temperature detection device 18. .

  It is assumed that the first temperature sensor 40 and the second temperature sensor 41 of this embodiment are small and inexpensive chip thermistors that can be arranged on an electronic substrate. However, it is not limited to the chip thermistor, and any temperature detecting element that can measure the ambient temperature without affecting the thermopile output may be used.

  Further, although the NTC thermistor 25-11 built in the thermopile 25 is used as the temperature detecting element in the steady state, the present invention is not limited to this. Obviously, an NTC thermistor provided on the substrate may be used. Further, the semiconductor element is not limited to the NTC thermistor, and may be a semiconductor element such as a temperature detecting element using a change in the forward voltage of the diode.

  Next, a second embodiment of the present invention will be described. The second embodiment is an example in which the arrangement of the first temperature sensor 40 inside the pan temperature detecting device 18 described in the first embodiment is changed.

  As described in the first embodiment, the first temperature sensor 40 only needs to be able to measure the temperature corresponding to the side hot junction of the thermopile 25. In the present embodiment, the first temperature sensor 40 is arranged in addition to the electronic circuit board 27.

  FIG. 17 shows a first temperature sensor installed inside the pan temperature detecting device 18. FIG. 17A has the same structure as that of FIG. 7 except for the first temperature sensor. Since the installation position is preferably arranged between the electronic circuit board 27 on which the thermopile 25 is arranged and the crystallized glass optical filter 31, the first temperature sensor 40-1 is placed inside the infrared sensor case corresponding to this condition. Deploy. The first temperature sensor 40-2 is disposed on the metal can 25-1 of the thermopile 25. The first temperature sensor 40-3 is disposed on the crystallized glass optical filter 31. The first temperature sensor 40-4 is disposed in the thermopile 25.

  FIG. 17 (b) shows the pan temperature detecting device 18 in which the heat pile 25-13 is attached to the thermopile 25. The temperature change when the ambient temperature of the thermopile 25 is changed by the heat sink 25-13 can be slowed down, and it is used for suppressing the sensor output fluctuation at the time of sudden temperature change. In such a structure, the first temperature sensor 40-2 is disposed on the heat sink 25-13.

  Based on the temperature difference between the temperatures measured by the first temperature sensor and the second temperature sensor in the same manner as in the first embodiment by disposing at any one of the first temperature difference sensors 40-1 to 40-4, the pan By detecting the radiant infrared rays from the pan regardless of the ambient temperature change of the temperature detecting device 18, the pan temperature detection can be accurately measured.

  Next, a third embodiment of the present invention will be described. Example 3 is the content regarding arrangement | positioning of the 2nd temperature sensor inside the pan temperature detection apparatus 18 demonstrated in Example 1. FIG.

  As described in the first embodiment, the second temperature sensor only needs to measure the temperature corresponding to the cold junction of the thermopile 25. In this embodiment, an arrangement example other than the electronic circuit board 27 will be described.

  FIG. 18 shows a second temperature sensor installed inside the pan temperature detector 18. FIG. 18 has the same structure as that of FIG. 7 except for the second temperature sensor. The installation position is preferably arranged between the bottom surface of the thermopile 25 and the bottom surface of the outer infrared sensor case 33. The second temperature sensor 41-1 is arranged inside the infrared sensor case corresponding to this condition. The second temperature sensor 41-2 is disposed on the bottom surface of the metal stem 25-2 of the thermopile 25. Since the cold junction 25-6 of the thermopile 25 conducts heat with the metal stem 25-2 via the silicon oxide film 25-5 and the silicon base material 25-4, the second temperature sensor is disposed.

  By detecting the radiant infrared rays from the pan regardless of the ambient temperature change of the pan temperature detection device 18 as in the first embodiment by arranging it in any location of the second temperature difference sensors 41-1 and 41-2, The pan temperature detection can be accurately measured.

  Next, a fourth embodiment of the present invention will be described. The third embodiment is a content in which the first temperature sensor is arranged between the air passages to the coil cooling air passage 15 by introducing outside air from the cooling fan built in the main body 1.

  FIG. 19 is a cross-sectional view showing the periphery of the right heating coil. 3 is different from FIG. 3 in the first embodiment in that 40-5 is provided as a first temperature sensor in the coil upper surface cooling air passage 15a, and 41-3 is provided as a second temperature sensor in the pot temperature detecting device 18. It is a point.

As described in the first embodiment, the pan temperature detecting device 18 changes the ambient temperature due to the exhaust heat of the heating coil 8 and the cooling air temperature increased by the exhaust heat of the inverter circuit 9 cooled by the cooling fan. This causes a temperature difference between the side hot contact portion 25-8 and the cold junction portion 25-6 of the thermopile 25, which causes the sensor output to fluctuate. The temperature of the cooling air blown to the pan temperature detection device 18 from the cooling fan built in the main body 1 is measured by the first temperature sensor 40-5, and the second temperature sensor 41-3 disposed close to the thermopile 25. Measure with By measuring the temperature difference between the first and second temperature sensors, by processing in the same manner as the temperature correction flow of FIG. 15, by detecting the infrared radiation from the pan regardless of the ambient temperature change due to cooling air, The pan temperature detection can be accurately measured.

DESCRIPTION OF SYMBOLS 1 ... Main body of induction heating cooker 2 ... Top plate 3 ... Operation display part 4 ... Circle (circle display which shows the position which puts a cooking pan)
5 ... Infrared transmitting window 6 ... Grill chamber 6a ... Upper grill heater, 6b ... Lower grill heater, 6c ... Net plate 7 ... Cooking pan 8 ... Heating coil 8a ... First coil, 8b ... Second coil, 8c ... Coil Gap, 8d ... Bridge 9 ... Inverter circuit 10 ... Coil base 11 ... Ferrite 14a ... Inner cavity 14b ... Outer cavity wall 15 ... Coil cooling air passage 15a ... Coil upper surface cooling air passage, 15b ... Coil lower surface cooling air delivery hole 15c ... Coil upper surface cooling air sending hole 16 ... Sealing material 18 ... Pan temperature detecting device 19 ... Sensor field cylinder 20 ... Thermistor 21a ... Low voltage terminal, 21b ... High voltage terminal 25 ... Thermopile 25-1 ... Metal can 25-2 ... Metal stem 25-3 ... Infrared absorbing film 25-4 ... Silicon substrate 25-5 ... Silicon oxide film 25-6 ... Cold junction part 25-8 ... Temperature measuring contact part 25-9 ... Polysilicon vapor deposition film 2 -10 ... Aluminum vapor deposition film 25-11 ... NTC thermistor 25-12 ... Metal pin 25-13 ... Window 25-14 ... Glass lens 26 ... Reflective photo interrupter 27 ... Electronic circuit board 28 ... Infrared sensor case 30 ... Case window 31 ... Crystallized glass optical filter 32 ... Metal case 33 ... Outside infrared sensor case 40 ... First temperature sensor 40-1 to 5 ... First temperature sensor 41 ... Second temperature sensors 41-1 and 41-2 ... second temperature sensor 50 ... infrared LED
51 ... Infrared phototransistor 60 ... Microcomputer 61 ... Frequency control circuit 62 ... Power control circuit 63 ... Rectifier circuit 64 ... Power switch 68 ... Grill heater control circuit 69 ... Operation switch 70 ... Display circuit 71 ... Buzzer 72 ... Infrared detection circuit 72 -1, 72-3, 72-4 ... OP amplifier 73 ... Reflectance detection circuit 74 ... Thermistor temperature detection circuit 76 ... Temperature sensor temperature detection circuit for hot junction 77 ... Temperature sensor temperature detection circuit for cold junction

Claims (7)

A top plate with a cooking container on top,
A heating coil provided under the top plate for inductively heating the cooking vessel;
An inverter circuit for supplying driving power to the heating coil;
A pan temperature detecting device that is provided under the heating coil and detects the pan temperature;
A microcomputer for controlling the inverter circuit based on the output of the pan temperature detecting device;
An induction heating cooker comprising:
In the pan temperature detecting device,
Infrared detecting means for detecting infrared radiation emitted from the bottom of the cooking vessel;
A first temperature sensor for detecting a first ambient temperature;
A second temperature sensor for detecting a second ambient temperature;
With
The microcomputer detects the infrared detection device based on a temperature difference between the first ambient temperature detected by the first temperature sensor and the second ambient temperature detected by the second temperature sensor. An induction heating cooker characterized by correcting the pan temperature. The induction heating cooker according to claim 1,
The first temperature sensor detects the ambient temperature of the hot junction of the infrared detection means,
The induction heating cooker, wherein the second temperature sensor detects an ambient temperature of a cold junction of the infrared detection means. The induction heating cooker according to claim 2,
Between the top plate and the pan temperature detecting device, there is provided a light guide tube that blocks infrared rays emitted from the heating coil and guides infrared rays emitted from the bottom of the cooking container to the infrared detecting means. And
The said pan temperature detection apparatus is covered with the windproof case which provided the window material which permeate | transmits infrared rays in the upper part, The induction heating cooking appliance characterized by the above-mentioned. The induction heating cooker according to claim 2,
The first temperature sensor is provided above the bottom surface of the infrared detection means,
The induction heating cooker, wherein the second temperature sensor is provided below the bottom surface of the infrared detection means. The induction heating cooker according to claim 2,
The first temperature sensor is provided above a substrate on which the infrared detection means is provided,
The induction heating cooker, wherein the second temperature sensor is provided below a substrate on which the infrared detecting means is provided. A top plate with a cooking container on top,
A heating coil provided under the top plate for inductively heating the cooking vessel;
An inverter circuit for supplying driving power to the heating coil;
A cooling fan for supplying cooling air to the heating coil and the inverter circuit;
An air path for guiding cooling air from the cooling fan to the heating coil or the inverter circuit;
A pan temperature detection device that is provided under the heating coil and in the air path, and detects the pan temperature;
An infrared detecting means built in the pan temperature detecting device for detecting infrared rays emitted from the bottom of the cooking vessel;
A microcomputer for controlling the inverter circuit based on the output of the pan temperature detecting device;
A first temperature sensor provided in the air passage for detecting a first ambient temperature;
A second temperature sensor provided in the pan temperature detecting device for detecting a second ambient temperature;
An induction heating cooker comprising:
The microcomputer detects the infrared detection device based on a temperature difference between the first ambient temperature detected by the first temperature sensor and the second ambient temperature detected by the second temperature sensor. An induction heating cooker characterized by correcting the pan temperature. In the induction heating cooker according to any one of claims 1 to 6,
The induction heating cooker, wherein the infrared detecting means is a thermopile.