JP6831350B2 - Induction heating cooker - Google Patents

Description

The present invention relates to an induction cooker.

In an induction heating cooker, an induction heating coil (hereinafter abbreviated as "heating coil") is installed under a top plate made of heat-resistant glass such as crystallized glass or borosilicate glass, and a high-frequency current is passed through it to generate an induction heating coil. A vortex current is induced in the bottom of the cooking pot placed on the top plate by the magnetic field, and the pot is directly heated by this Joule heat.

As a means for detecting the temperature of the bottom of an induction cooker, an infrared sensor that detects the temperature by observing infrared rays radiated from the bottom of the heated pot with a good response speed through the top plate is often used. As this infrared sensor, a quantum type sensor such as a photodiode or a thermal type sensor such as a thermopile is used. This infrared sensor is placed below the center gap of the heating coil, detects infrared rays radiated from the bottom of the pot through the top plate, outputs the temperature of the bottom of the pot, and controls the output of the inverter circuit according to the output to control the heating coil. It drives and regulates the temperature of the pot. The pan placed on the top plate is heated in the cooking temperature range (about 80 ° C to 250 ° C).

The temperature detection of the bottom of the pot can be detected by the infrared sensor receiving infrared rays radiated from the bottom of the pot and detecting the output voltage of the infrared sensor. However, the radiant energy when the infrared sensor receives the infrared rays generated at the bottom of the cooking pot is small. This is due to the optical properties of the top plate. This is because the wavelength transmitted through the top plate is only about 4.0 μm in width of 1.0 μm to 5.0 μm, and only 1 to 2% of the total radiated infrared energy of the pot can be transmitted through the top plate. Therefore, the sensitivity of the infrared sensor used is required to be an order of magnitude higher than that used for a thermometer or the like. Further, since the sensor output signal is small, an amplifier circuit having a high amplification factor is required, and as a result, these infrared sensors become very sensitive to fluctuations in ambient temperature. The thermopile type infrared sensor generates a sensor output voltage proportional to the temperature of the hot contact side and the cold contact side of the heat sensitive element when infrared rays are incident on it. Therefore, in an environment where the temperature around the sensor changes rapidly, the temperature of the heat sensitive element is high. The contact side and the cold contact side become non-uniform, and the sensor output fluctuates.

Further, the infrared sensor has an incident energy 1 radiated from the bottom of the pot, an incident energy 2 radiated from a top plate heated by heat transfer from a heated cooking pot, and further between the top plate and the infrared sensor. The arranged member receives the incident energy 3 radiated by being heated by the radiant heat from the induction heating coil. In the detection of the temperature at the bottom of the pot, the incident energy 2 and the incident energy 3 become disturbances.

As a means for solving this problem, there is one listed in Patent Document 1.

Patent Document 1 includes a first infrared sensor having a thermistor so as to detect a change in ambient temperature, detecting infrared rays radiated from the bottom of a cooking container, and outputting a DC voltage proportional to the amount of infrared rays. By blocking the infrared rays radiated from the bottom of the cooking container and the first DC amplifier that amplifies the infrared sensor output of 1, the infrared rays radiated from the bottom of the cooking container are not incident and are proportional to the amount of infrared rays. A second infrared sensor that outputs a DC voltage to be generated and a second DC amplifier that inverts and amplifies the output of the second infrared sensor are provided, and the output of the second DC amplifier is used as the output of the first DC amplifier. By inputting as the bias voltage of the DC amplifier and outputting the output of the first DC amplifier to the infrared detecting means, the atmospheric temperature of the infrared sensor (thermopile) changes slowly (steady state) following the change in room temperature. It is equipped with an infrared detection means that can stably detect the temperature of the pot even if a sudden change (transient state) in the atmospheric temperature occurs during cooking or cooking, and the temperature of the bottom of the pot In order to improve the detection accuracy, a crystallized glass optical filter that cuts infrared rays in a specific wavelength range is placed between the infrared sensor and the heating coil, and in the specific wavelength range of the incident energy 2 that is radiated from the top plate and becomes a disturbance. Block infrared rays. Further, in order to reduce the incident energy 3 in which the members (crystallized glass optical filter 31 and sensor viewing tube 19 and the like) arranged between the top plate and the infrared sensor are heated and radiated by radiant heat from the induction heating coil and become disturbance. The glass convex lens used for the infrared sensor is made of glass with an optical characteristic of 5 μm short pass characteristic, and infrared rays emitted in a low temperature range of 5 μm or more reach the infrared absorbing film of the thermopile during cooking. I'm removing the infrared.

Japanese Unexamined Patent Publication No. 2013-206644

In the infrared detecting means shown in Patent Document 1, there is a problem that it is not possible to correct the deviation according to the variation in the heat transfer characteristics of the two thermopile used.

The deviation of the heat transfer characteristics is caused by the difference between the thermopile for detecting pan-radiated infrared rays having a convex lens on the detection element and the thermopile of the temperature compensating element covered with a light-shielding metal can and the mutual distance, which will be explained in detail below. To do.

The thermopile for detecting infrared rays emitted from the pot and the thermopile of the temperature compensating element covered with a light-shielding metal can are placed in independent metal cans and metal stems, respectively, and because they are provided separately, the temperature due to ambient temperature unevenness, etc. There is a problem that a deviation occurs due to a temperature difference due to a difference and a difference in heat transfer. Further, the thermopile for detecting the infrared radiation from the pot receives the incident energy through the glass convex lens, and the thermopile of the temperature compensating element covered with the light-shielding metal can receives the energy radiated by the light-shielding metal can. Both the glass convex lens and the light-shielding metal can are affected by the ambient temperature change, and the incident energy due to the infrared rays emitted from the glass convex lens and the light-shielding metal can differs due to the temperature change of the glass convex lens and the light-shielding metal can. There is a problem that the temperature shift occurs.

Next, the infrared rays received by the thermopile for detecting the infrared rays emitted from the pot include the infrared rays radiated from the bottom of the pot and the paths provided to receive the infrared rays emitted from the bottom of the pot and the parts in the paths. There is a problem that infrared rays emitted from are included. The details of the problem will be described below.

As described above, the incident energy received by the thermopile for detecting infrared rays emitted from the pot includes the incident energy 1 attenuated when the infrared rays radiated from the bottom of the pot of the cooking pot pass through the top plate and the crystallized glass optical filter. Infrared rays radiated from the top plate heated by heat transfer from the heated cooking pot and members placed between the top plate and the infrared sensor are radiated from the sensor viewing tube heated by radiant heat from the induction heating coil. The incident energy 2 in which the infrared rays were transmitted through the crystallized glass optical filter and attenuated, and the member arranged between the top plate and the infrared sensor were radiated from the crystallized glass optical filter heated by the radiant heat from the induction heating coil. There is an incident energy 3 in which infrared rays are transmitted and attenuated through a glass convex lens provided in a thermopile for detecting pan-radiated infrared rays, and an incident energy 4 in which infrared rays radiated from the glass convex lens are incident.

In the thermopile for detecting the infrared rays emitted from the pan, the incident energy 2, the incident energy 3, and the incident energy 4 other than the incident energy 1 required for detecting the temperature of the pan are unnecessary disturbances.

The incident energy 2 that becomes a disturbance is transmitted through the crystallized glass optical filter, and the incident energy 3 is transmitted through the glass convex lens, so that it is radiated at a low temperature other than the temperature range (about 80 to 350 ° C.) required for cooking. Since infrared rays of 5 μm or more are blocked and the incident energy 4 directly reaches the infrared absorbing film, there is a problem that the change in radiant energy due to the temperature change of the glass convex lens is a large disturbance.

From the above, Patent Document 1 has two problems. The first is the deviation according to the variation in the heat transfer characteristics of the two thermopile, and the second is the problem that the change in radiant energy due to the temperature change of the glass convex lens becomes a big disturbance.

An object of the present invention is to provide an induction heating cooker that accurately detects the temperature of the bottom of a cooking pot.

The present invention has been made to solve the above problems, and is a heating in which a top plate on which a cooking pot is placed on the upper surface and a heating provided below the top plate to generate an induced potential for heating the cooking pot. The coil, the inverter means for supplying electric power to the heating coil, the infrared sensor that detects the temperature of the cooking pot through the top plate, the detection circuit that amplifies the output of the infrared sensor, and the output of the detection circuit. In an induction heating cooker provided with a control means for controlling the output of the inverter means accordingly, the infrared sensor includes a first heat-sensitive element and a second heat-sensitive element in the same metal case, and the detection circuit. The reference potential is arbitrarily set, the first amplifier uses the reference potential as the first bias input to amplify the output of the first heat sensitive element, and the reference potential is used as the first bias input. A second amplifier that amplifies the output of the second heat-sensitive element, and a third amplifier that amplifies the amplified output of the first heat-sensitive element by using the amplified output of the second heat-sensitive element as a second bias input. It is prepared.

According to the present invention, it is possible to provide an induction heating cooker that accurately detects the temperature of the bottom of a cooking pot. Issues, configurations and effects other than those described above will be clarified by the following description of the embodiments.

The perspective view which shows the structure of the induction heating cooker which concerns on this invention. Top view of the induction cooker according to the present invention excluding the top plate. The block diagram which shows the structure of the pot bottom temperature detecting means mainly which left and right heating coils of the induction heating cooker which concerns on this invention. The cross-sectional view which shows the detail of the pot temperature detection apparatus which concerns on this invention. Top view of the pan temperature detector according to the present invention. The figure which shows the detail of the infrared sensor which concerns on this invention. The figure which shows the outline of the infrared ray detecting means which concerns on this invention. The figure which shows the visual field characteristic of the infrared sensor which concerns on this invention. The figure which shows the spectral radiant energy by the distribution rule of Planck which concerns on this invention. The figure which shows the optical property of the top plate which concerns on this invention. Explanatory drawing of the reflection type photo interrupter which concerns on this invention. Explanatory drawing of the detection circuit of this invention. Explanatory drawing of another embodiment of the detection circuit of this invention.

Hereinafter, examples of the present invention will be described with reference to the drawings and the like. The following description shows specific examples of the contents of the present invention, and the present invention is not limited to these descriptions. Various changes and modifications can be made by those skilled in the art within the scope of the technical ideas disclosed in the present specification, and it is planned from the beginning that the configurations of the following examples are appropriately combined. Further, in all the drawings for explaining the present invention, those having the same function may be designated by the same reference numerals, and the repeated description thereof may be omitted.

(Example)
FIG. 1 is a perspective view of the main body 1 of the induction heating cooker, FIG. 2 is a top view of the induction heating cooker excluding the top plate 2, and FIG. 3 is a pan bottom temperature mainly composed of the left and right heating coils 3 of the induction heating cooker. It is a block diagram which shows the structure of the detection means.

In the following, an induction heating cooker having three pot storage locations where induction heating is possible will be described as an example, but the application of the present invention is not limited to this, and one port at the central rear portion is a radiant heater or a halogen heater. It may be a place where a pot can be heated by the radiant heat of a heater (heating source) such as the above, or an induction heating cooker having a number of heaters. The cooking pot 30 to be heated is a magnetic iron pot suitable for induction heating, a non-magnetic aluminum pot, a copper pot, or the like.

In FIG. 1, a top plate 2 is arranged on the upper surface of the main body 1 of the induction heating cooker. The top plate 2 is made of heat-resistant crystallized glass, and a cooking pot 30 is placed on the top plate 2. The top plate 2 of this embodiment will be described by taking crystallized glass as an example, but the top plate 2 is not limited to this as long as it has excellent heat resistance and satisfies the specifications of the induction cooking device, and for example, borosilicate glass may be used.

The entire upper surface of the top plate 2 is painted with a specific design so that the inside of the main body 1 cannot be seen, and the mounting portion 4 of the cooking pot 30 is printed. An infrared transmission window 5 is provided in the mounting portion 4 of the cooking pot 30. In the infrared transmitting window 5, in order to transmit infrared rays radiated from the bottom of the cooking pot 30 to the lower part of the top plate 2, the state of the material of the top plate 2 and a paint that transmits infrared rays are applied without applying the coating. I have just done it.

Upper surface operation portions 6a, 6b, and 6c corresponding to the respective heater portions (heating coil 3 shown in FIG. 2) are provided on the upper surface on the front surface side of the top plate 2, and the energized state of the heating coil 3 can be set. Perform the operation. Further, corresponding upper surface display units 7a, 7b, 7c are provided in the vicinity of the upper surface operation units 6a, 6b, 6c to display the energized state of each heating coil 3.

The upper surface operation unit 6a inputs the thermal power of the heating coil 3 on the right side of the main body 1, the upper surface operation unit 6b inputs the thermal power of the heating coil 3 at the rear center of the main body 1, and the upper surface operation unit 6c inputs the thermal power of the heating coil 3 on the left side of the main body 1. Input the thermal power of the heating coil 3 and the like.

A grill 8 for baking fish, pizza, etc. is provided on the left side of the front surface of the main body 1, and the grill 8 has a box shape with an open front, and heat generated by a sheathed heater or the like in the internal cooking chamber. A thermistor for detecting the temperature inside the body and the inside is provided, and the front portion is closed by a grill door 8b to which a handle 8a is attached. A saucer is attached to the back side of the grill door 8b, and the grill door 8b is stored in the kitchen so as to be freely taken in and out from the front opening, and foods such as fish and pizza are placed on the saucer or a grill to cook.

On the right side of the front surface of the main body 1, a main power switch 9 for supplying power to the main body 1 and a front operation unit 10 for inputting cooking conditions and the like of the grill storage 8 are provided. The front operation unit 10 is of a so-called kangaroo pocket type in which the upper part of the operation panel is tilted toward the front side with the rotation axis provided below as the center and the operation keys are exposed toward the upper side.

An inverter board or control board (not shown) provided in the main body 1 for cooling air taken in from an opening (not shown) that takes in outside air into the main body 1 by a fan (not shown) provided in the main body 1. , The heating coil 3 and the pot bottom temperature detecting device 20 for detecting the temperature of the pot bottom are passed to cool the pot. An exhaust port 11 for exhausting the cooling air that has cooled the inside of the main body 1 is provided at the rear portion of the main body 1.

As shown in FIG. 2, the heating coils 3 formed in an annular shape are arranged on the left and right sides of the upper part of the main body 1 and at the rear part of the center, respectively, below the top plate 2 corresponding to the mounting portion 4. The cooking pot 30 and the like placed on the above are induced and heated. The heater portions of the heating coils 3 arranged on the left and right and the central rear portion are each composed of an annular inner heating coil 3a and an annular outer heating coil 3c arranged with an annular gap 3b provided on the outer side thereof. .. The reason for providing the gap 3b is to disperse the magnetic flux generated by the inner heating coil 3a and the outer heating coil 3c to make the temperature of the cooking pot 30 uniform.

Although each heating coil 3 is configured to have a gap 3b, the present invention is not particularly limited to this. For example, the inner heating coil 3a and the outer heating coil 3c may be wound without a gap to form a heating coil 3 having no gap 3b.

As shown in FIG. 3, the heating coil 3 has an inner heating coil 3a, a gap 3b, and an outer heating coil 3c installed on the coil base 12. Further, the gap spacer 13 is provided by a support member 13a attached to the outer peripheral edge portion of the coil base 12 so as to maintain an appropriate interval from the outer periphery of the coil base 12 toward the center side, and a plurality of coil bases 12 are provided. By being urged in the direction of the top plate 2 by a spring (not shown), the heating coil 3 is substantially parallel to the top plate 2, and the cooking pot 30 and the heating coil 3 placed on the top plate 2 The gap is kept constant.

The inner heating coil 3a and the outer heating coil 3c employ litz wire in order to suppress the skin effect, and a voltage of several hundred V is applied to the cooking pot 30 at a high frequency of several tens of kHz by the inverter means 54 described later. On the other hand, a high-frequency magnetic field is applied to generate an eddy current in the cooking pot 30, and the cooking pot 30 is self-heated to be heated.

A plurality of temperature sensors 14 composed of thermistors are arranged on the heating coils 3 arranged on the left and right and in the center. An inner temperature sensor 14a is provided in close contact with the lower surface of the top plate 2 near the center of the heating coil 3, and the temperature of the cooking pot 30 placed above the heating coil 3 is measured via the top plate 2. To detect. In this embodiment, a thermistor is used as the temperature detecting means of the top plate 2, but the present invention is not particularly limited to this, and a detector such as a thermocouple may be used. Similarly, outside temperature sensors 14b and 14c (FIG. 2) configured by thermistors are provided in the gap 3b of the heating coil 3 at equal distances from the center of the heating coil 3 via a cushioning material (not shown). The temperature of the top plate 2 is detected by being in close contact with the lower surface of the top plate 2.

The outer temperature sensors 14b and 14c are provided in the gap 3b of the heating coil 3, but the present invention is not particularly limited to this. For example, it may be provided near the outer periphery of the outer heating coil 3c, or near the outer periphery of the heating coil 3 having no gap 3b in which the inner heating coil 3a and the outer heating coil 3c are wound without a gap. Further, the number of the outer temperature sensors 14b and 14c is not limited to two, and may be one or two or more.

A pan temperature detecting device 20 is installed below the gap 3b of the heating coil 3. Below the gap 3b, a light guide tube 28 shown in FIG. 4 to be described later, which is provided in the pot temperature detection device 20, is arranged. The pot temperature detecting device 20 is radiated from the bottom surface of the cooking pot 30, passes through the infrared transmitting window 5 of the top plate 2, and receives infrared rays guided by the light guide tube 28.

FIG. 4 is a diagram illustrating the details of the pot temperature detecting device 20. FIG. 4 shows a cross-sectional view of the pot temperature detecting device 20 as seen from the XX cross section shown in FIG. The pan temperature detection device 20 is provided with an infrared sensor 21 which is a first infrared sensor and a reflective photointerrupter 22 which is a second infrared sensor described later in FIG. The infrared sensor 21 will be described by taking a thermopile of a thermal detection element as an example. The infrared sensor 21 and the reflective photo interrupter 22 are arranged on an electronic circuit board 23 provided with an amplifier circuit that amplifies the output of the infrared sensor 21 and an amplifier circuit that amplifies the output of the reflective photo interrupter 22. Each output of the infrared sensor 21 and the reflective photo interrupter 22 is output from the output terminal 23a (shown in FIG. 5) of the electronic circuit board 23, and the output signal is input to the temperature conversion means 50.

FIG. 11 is a diagram illustrating a reflective photo interrupter 22. As shown in the figure, the reflective photo interrupter 22 is composed of an infrared LED 22a as an infrared emitting means and an infrared phototransistor 22b as an infrared receiving means.

A lens made of plastic is formed on the light emitting surface of the infrared LED 22a, and infrared light of a thin beam is irradiated upward through the infrared transmission window 5 of the top plate 2. Further, a plastic lens is mounted on the light receiving surface of the infrared phototransistor 22b, and the infrared light emitted by the infrared LED 22a is reflected by an object (bottom surface of the cooking pot 30) covering the infrared transmission window 5. Is received, and a current corresponding to the amount of the received light is output. The output of the infrared phototransistor 22b of the reflective photointerruptor 22 is input to the temperature conversion means 50.

This will be described with reference to FIGS. 4 and 5. FIG. 5 shows a top view of the pot temperature detecting device 20. 5 (a) is a top view of the sensor case 24 containing the electronic circuit board 23, FIG. 5 (b) is a top view of the metal case 27, and FIG. 5 (c) is a top view of the light guide tube 28. is there.

The electronic circuit board 23 on which the infrared sensor 21 and the reflective photointerruptor 22 are installed is entirely housed in a sensor case 24 made of a plastic member, which is a second case. A case window 25 is opened above the sensor case 24 to transmit infrared rays, and the case window 25 has similar optical characteristics to the crystallized glass constituting the top plate 2 (described with reference to FIG. 10). As described above, the optical characteristics on the long wavelength side of 1 μm or more are almost the same as those of the top plate 2. However, when the wavelength is 1 μm or less, the transmittance is small and visible rays are cut off), and the optical filter 26 is fitted. The infrared sensor 21 and the reflective photo interrupter 22 are arranged below the optical filter 26.

The upper surface and side surfaces of the sensor case 24 are covered with a metal case 27 such as aluminum having a magnetic permeability of substantially 1, and an opening 27a opened above the case window 25 is provided.

A light guide tube 28 is arranged on the upper portion of the metal case 27, and the light guide tube 28 is provided with an opening of an upper end opening 28a and an opening of a lower end opening 28b. The condensing lens 21a (shown in FIG. 5) of the infrared sensor 21 and the reflective photointerruptor 22 are arranged so as to face the top plate 2 via the upper end opening 28a and the lower end opening 28b. The light guide tube 28 guides infrared rays from the cooking pot 30 to the infrared sensor 21, and as will be described later in FIG. 11, the infrared rays projected by the reflective photo interrupter 22 are reflected by the cooking pot 30, and the reflected infrared rays are reflected. It is an optical path leading to the photo interrupter 22.

From FIG. 5A, the infrared sensor 21 and the reflective photo interrupter 22 are arranged below the optical filter 26 arranged in the case window 25 of the sensor case 24. The condenser lens 21a of the infrared sensor 21 and the reflective photo interrupter 22 are arranged so as to face the optical filter 26. From FIG. 5B, the opening 27a of the metal case 27 faces the optical filter 26 arranged below. From FIG. 5C, the upper end opening 28a of the light guide tube 28 is arranged so as to face the optical filter 26. That is, an optical path is formed in which the infrared sensor 21 and the reflective photo interrupter 22 face the bottom of the cooking pot 30 through the infrared transmission window 5 of the top plate 2. In this embodiment, the upper end opening 28a of the light guide tube 28 will be described in a configuration in which the upper end opening 28a is arranged below the inner heating coil 3a and the outer heating coil 3c, but the present invention is not limited to this, and the upper end opening 28a is an infrared transmission window. It may be placed below 5.

FIG. 6 shows the details of the infrared sensor 21. FIG. 6A shows a perspective view of the infrared sensor 21. FIG. 6B shows a cross-sectional view of the infrared sensor 21 along the line indicated by AA in FIG. 6A. FIG. 6C shows the optical characteristics of the condenser lens and the positional relationship of the heat sensitive element.

The infrared sensor 21 is a thermal infrared detection element in which a large number of thermocouples are connected in series, and is built in a metal case 33, which is a first case and is composed of a metal can 31 such as a nickel-plated steel plate and a metal stem 32.

A pot detection element 35a and a temperature compensation element 35b are arranged on the surface of the silicon substrate 34. The pot detection element 35a and the temperature compensation element 35b are formed by sequentially pattern-depositing polysilicon and aluminum to form a large number of thermocouples from the polysilicon-deposited film and the aluminum-deposited film, and these are connected in tandem. A rubidium oxide film or polyimide close to a black body is located at the center of each of the heat-sensitive element (pot detection element) 35a and the heat-sensitive element (temperature compensation element) 35b having a polysilicon and aluminum junction (temperature measuring contact). An infrared absorbing film such as a film is formed as a protective film, and one end of the polysilicon and aluminum vapor deposition film is a cold contact. The silicon substrate 34 is fixed to the metal stem 32 of the metal case 33 with a bond or the like.

A plurality of metal pins 36 that are insulated and sealed are penetratingly arranged on the metal stem 32, and the output of the thermocouple is connected to the tip of the metal pins 36 by a wire. The metal stem 32 is covered with a tubular metal can 31 in an inert gas such as nitrogen and welded.

An opening 37 of a small hole is formed on the upper surface of the metal can 31. A condenser lens 21a is attached to the opening 37.

Next, using FIG. 6C, the optical characteristics of the two heat-sensitive elements (pot detection element 35a (first heat-sensitive element) and temperature compensation element 35b (second heat-sensitive element)) and the condenser lens. The relationship with is explained.

It is desirable that the optical characteristics of the condenser lens 21a are close to those of the top plate 2 so that the infrared rays of the pan can be efficiently incident and the thermal disturbance can be cut. In this implementation, borosilicate glass is used as the material of the condenser lens. Instead of borosilicate glass, crystallized glass or quartz glass having similar optical characteristics may be used.

The positional relationship between the pot detection element 35a for detecting the temperature of the cooking pot 30 and the condenser lens 21a is perpendicular to the lens surface through the center 35a1 of the infrared light receiving surface of the pot detection element 35a and the center of the condenser lens 21a. The infrared rays 35a2, which are in a positional relationship that substantially coincides with the optical axis 21a1 and are incident in parallel with the optical axis 21a1, are focused on the infrared receiving surface of the pot detection element 35a.

Next, the pot detection element 35a is provided on the circumference around the center, and the temperature compensation element 35b is provided at a position adjacent to the pot detection element 35a. The positional relationship between the temperature compensating element 35b and the condensing lens 21a is such that the infrared rays 35b2 incident parallel to the inclined optical axis 21a2 connecting the center of the infrared receiving surface of the temperature compensating element 35b and the center of the condensing lens 21a. Is provided at a position where light is substantially collected on the infrared light receiving surface of the temperature compensating element 35b.

From the above, approximately the same amount of infrared rays emitted by the condenser lens 21a is incident on both the pot detection element 35a and the temperature compensation element 35b.

In this embodiment, two independent chips of the pot detection element 35a and the temperature compensation element 35b will be described on the surface of the silicon substrate 34, but the present invention is not limited to this, and two elements are arranged on one chip. It may be configured. By using two elements and one chip, the temperature conditions on the cold contact side of each thermal element become the same, and the level of output fluctuation due to the temperature characteristics can be suppressed to the same level. In addition, the assembly process of the infrared sensor 21 can be simplified, which contributes to the cost reduction of the sensor.

FIG. 7 shows an outline of the detection circuit 40. Inside the infrared sensor 21, the output ((+), (-) symbols in the figure) -side of the pot detection element 35a and the-side of the temperature compensation element 35b are connected in series. As for the output of the pan detection element 35a, the + side is connected to the operational amplifier (hereinafter abbreviated as OP amplifier) 41, and the + side of the temperature compensation element 35b is connected to the OP amplifier 41. The output signal obtained by amplifying the potential difference between the + side of the pan detection element 35a and the + side of the temperature compensation element 35b by about 3000 times by the OP amplifier 41 is input from the output terminal 23a of the electronic circuit board 23 to the temperature conversion means 50. Will be done. The potential on the + side of the pot detection element 35a is proportional to the incident energy from the cooking pot 30, and the potential on the + side of the temperature compensation element 35b is the incident energy transmitted through the optical filter 26 and the condenser lens 21a. Is proportional to.

When the pot temperature detection device 20 is heated by radiant heat from the heating coil 3 and the ambient temperature of the infrared sensor 21 changes, the temperature of the metal case 33 changes, and the cold contact temperatures of the pot detection element 35a and the temperature compensation element 35b change. To do. Since the pot detection element 35a and the temperature compensation element 35b are adjacent to each other and the temperature changes are the same, "the potential on the + side of the pot detection element 35a" = "the potential on the + side of the temperature compensation element 35b". The potential difference becomes 0, and the output fluctuation due to the change in the ambient temperature of the infrared sensor 21 can be suppressed.

FIG. 8 shows the visual field characteristics of the infrared sensor 21 in the cross-sectional view of FIG. 6B. As for the relative sensitivity in the figure, 100% is the sensitivity incident on the pan detection element 35a from the central axis of the condenser lens (viewing angle 0 °). As shown in the circuit diagram of FIG. 7, the temperature compensation element 35b has a negative output value when infrared rays are incident on the temperature compensation element 35b because the + and-outputs of the heat sensitive element are reversed from those of the pot detection element 35a. It becomes about -100% near the viewing angle of + 40 °. The visual field characteristics of the relative sensitivity of 50% or more are about −10 ° to + 10 ° for the pot detection element 35a and about + 30 ° to + 50 ° for the temperature compensation element 35b.

This visual field characteristic is shown in the cross-sectional view of FIG. 6B as a detection range 38 of the pot detection element 35a and a detection range 39 of the temperature compensation element 35b. The maximum peak sensitivity position 38a (relative sensitivity 100%) of the pot detection element 35a is a position where the bottom of the cooking pot 30 is detected through the infrared transmission window 5 of the top plate 2 (optical axis 21a1 (FIG. 6 (c))). ). The maximum peak sensitivity position 39a (relative sensitivity of about -100%) of the temperature compensating element 35b is provided so as to be a position (optical axis 21a2 (FIG. 6C)) for detecting the inner wall of the light guide tube 28. However, the above-mentioned viewing angle + 40 ° is not limited.

Next, the characteristics of the optical path in which infrared rays from the bottom surface of the cooking pot 30 are incident on the infrared sensor 21 will be described.

The cooking pot 30 placed on the top plate 2 generates heat by induction heating. By this heating, the temperature of the cooking pot 30 starts to rise, and infrared rays proportional to the temperature are radiated from the bottom surface. This total radiant energy E is proportional to the fourth power of the pot temperature T (E = εσT ⁴ ; Stefan-Boltzmann's law).

FIG. 9 shows the spectral radiant energy of the blackbody temperature calculated from Planck's distribution law. By integrating this spectral radiant energy in the entire wavelength range, the total radiant energy can be obtained, which is proportional to the fourth power of the temperature (absolute temperature). This is the Stefan-Boltzmann law described above, and this coefficient σ is the Stefan-Boltzmann coefficient. The peak wavelength of the spectral radiant energy is 5 to 8 μm at a cooking temperature of 100 to 300 ° C. according to the Viennese variation law.

The inducedly heated pot bottom emits the total radiant energy obtained by multiplying the total radiant energy E of the blackbody temperature by the emissivity ε of the pot bottom according to the temperature. That is, the ratio of the total radiant energy E of the blackbody temperature to that of the pot bottom temperature (E'= εσT ⁴ ) is the emissivity ε.

On the other hand, the optical characteristics of the non-magnetic crystallized glass (top plate 2) are shown by solid lines in FIG. As shown by the solid line in FIG. 10, the crystallized glass transmits 80% or more of light having a wavelength of 0.4 to 2.9 μm and transmits light having a wavelength of 3 to 4.5 μm by up to 50%. It hardly transmits light with wavelengths longer than .5 μm and wavelengths shorter than 0.4 μm. Borosilicate glass also requires almost the same optical properties. The optical characteristics of the optical filter 26 are shown by a dashed line in FIG. As described above, the optical characteristics on the long wavelength side of 1 μm or more have characteristics close to those of the top plate 2, and the range on the short wavelength side is narrow so that light having a wavelength shorter than 0.5 μm is hardly transmitted. Therefore, by passing through the optical filter 26, the influence of infrared rays radiated from parts (for example, the light guide tube 28) due to the temperature change (normal temperature to about 75 ° C.) in the main body of the induction heating cooker during cooking is almost eliminated. it can.

The infrared radiant energy radiated from the bottom of the induction-heated cooking pot 30 has the transmittance of each of the three types of optical characteristics of the infrared transmission window 5 of the top plate 2, the optical filter 26, and the condensing lens 21a of the infrared sensor 21. The product is incident on the infrared sensor 21. Therefore, most of the infrared radiant energy radiated from the cooking pot 30 (wavelength 4 μm or more and 0.5 μm or less) cannot be received by the infrared sensor 21. When the infrared radiant energy with a transmittance of 100% (without the top plate 2 and the optical filter 26) is 100% in the entire wavelength range, the infrared radiant energy received by the infrared sensor 21 is radiated from the cooking pot 30. It is about 1 to 2% of the total infrared radiant energy. In order to efficiently detect the infrared radiant energy at the bottom of the pot, it is desirable that the top plate 2, the optical filter 26, and the condenser lens 21a have the same wavelength transmission characteristics.

In addition, a visible light cut function (0.1) is used to prevent visible light (wavelength 0.4 to 0.8 μm) from entering the infrared sensor 21 from illumination or the like on any of the top plate 2, the optical filter 26, and the condenser lens 21a. It is necessary to have a transmittance of μm or less (which is close to 0%), and in this implementation, the transmittance of the optical filter 26 is attenuated at 1 μm or less, and light having a wavelength shorter than 0.5 μm is hardly transmitted. Therefore, the incident of visible light (wavelength range 0.4 to 0.8 μm) on the infrared sensor 21 is suppressed.

In this embodiment, the visible light cut function is provided to the optical filter 26, but when the infrared transmission window 5 of the top plate 2 has the visible light cut function, even if the optical filter 26 does not have the visible light cut function. good.

Further, when a silicon lens or the like having a visible light cutting function is used for the condensing lens 21a of the infrared sensor 21, the infrared transmitting window 5 and the optical filter 26 do not have to have the visible light cutting function. The optical characteristics of the silicon lens are that it cuts wavelengths of 0.8 μm or less, has a transmittance of 50% from 1 to 25 μm, and cuts the wavelength region of visible light of 0.4 to 0.8 μm.

Next, the infrared radiant energy received by the pot detection element 35a and the temperature compensation element 35b will be described below.

Infrared rays transmitted from the cooking pot 30 through the top plate 2 and the optical filter 26 and attenuated are incident on the pot detection element 35a as incident energy Q1, and the top plate 2 is heated by heat conduction from the heated pot or the like. The infrared rays radiated from the infrared rays are transmitted through the optical filter 26 and attenuated, and the infrared rays are incident as incident energy Q2, and the members arranged between the top plate 2 and the optical filter 26 are heated by radiant heat from the induction heating coil or the like. Infrared rays radiated from the optical filter 26 affected by the fluctuating temperature inside the main body pass through the condenser lens 21a and are incident as incident energy Q3 as disturbance, and infrared rays radiated from the condenser lens 21a are incident as disturbance. When incident as energy Q4 and the ambient temperature of the infrared sensor 21 suddenly changes, the temperature generated due to a temperature difference between the hot and cold contacts of the pot detection element 35a due to heat conduction from the metal can 31 and the metal stem 32. Disturbance energy Q5 (variation in heat transfer characteristics) is added. Therefore, the total incident energy Q = Q1 + Q2 + Q3 + Q4 + Q5 on the pot detection element 35a.

Further, the temperature compensating element 35b has a viewing angle shifted from that of the pot detecting element 35a due to the lens effect of the condensing lens 21a, so that the incident energy Q1 from the cooking pot 30 and the incident energy Q2 from the top plate 2 are A member that is shielded from light and is arranged between the top plate 2 and the optical filter 26 is heated by radiant heat from an induction heating coil or the like, and infrared rays emitted from the optical filter 26 affected by the fluctuating temperature inside the main body are condensed lenses. When the incident energy Q3 is incident as a disturbance through 21a, the infrared rays radiated from the condenser lens 21a are incident as incident energy Q4 as a disturbance, and the ambient temperature of the infrared sensor 21 suddenly changes, the metal can 31 and the metal stem Temperature disturbance energy Q5 (variation in heat transfer characteristics) generated by causing a temperature difference between the hot contact and the cold contact side of the temperature compensating element 35b due to heat transfer from 32 is added. Therefore, the total incident energy Q = Q3 + Q4 + Q5 on the temperature compensating element 35b.

The field of view (detection range 39) of the temperature compensation element 35b is different from that of the pan detection element 35a due to the lens effect of the condenser lens 21a. The peak sensitivity position 39a (relative sensitivity of about -100%), which is the maximum in the field of view (detection range 39) of the temperature compensating element 35b, detects the inner wall of the light guide tube 28. However, in the temperature range (normal temperature to about 75 ° C.) affected by the light guide tube 28 due to the temperature change (normal temperature to about 75 ° C.) in the main body during cooking, the infrared rays emitted from the light guide tube 28 are the optical filter 26. Therefore, the influence of the temperature compensating element 35b as the received energy is very small.

Next, with respect to the above-mentioned disturbance affecting both the pot detection element 35a and the temperature compensation element 35b, the magnitude of each incident energy for each incident energy will be described.

The incident energy Q3 received by the pan detection element 35a and the temperature compensation element 35b is such that infrared rays radiated from the optical filter 26 are transmitted through the condenser lens 21a and received. The optical filter 26 is provided at a position that is not easily affected by the cooling air on the pan temperature detecting device 20 side of the light guide cylinder 28 so as to suppress the occurrence of uneven temperature distribution. Further, the infrared rays received by the pot detection element 35a and the temperature compensation element 35b are emitted from the optical filter 26, and the infrared rays emitted by the optical filter 26 received by the pot detection element 35a and the temperature compensation element 35b are emitted. , The optical filter 26 has substantially the same position and the same size. Therefore, the incident energy Q3 received by the pot detection element 35a and the incident energy Q3 received by the temperature compensating element 35b have substantially the same magnitude and change timing of the incident energy Q3.

The incident energy Q4 received by the pot detection element 35a and the temperature compensation element 35b is infrared rays radiated from the condenser lens 21a incident on the pot detection element 35a and the temperature compensation element 35b. As described above, the pot detection element 35a and the temperature compensation element 35b are installed so as to have different fields of view by different installation positions with respect to the optical axis of the condenser lens 21a. However, the infrared rays emitted by the condenser lens 21a are received in the same manner by both the pot detection element 35a and the temperature compensation element 35b. Therefore, the respective magnitudes of the incident energy Q4 received by the pan detection element 35a and the temperature compensating element 35b and the timing at which each magnitude changes are the same.

The temperature disturbance energy Q5 that is heat-transferred between the pot detection element 35a and the temperature compensation element 35b has a temperature difference between the hot contact and the cold contact side of the pot detection element 35a, and the temperature contact and the cold contact of the temperature compensation element 35b. It is caused by a temperature difference on the side and a temperature difference between the pot detection element 35a and the temperature compensation element 35b. However, in this embodiment, both the pot detection element 35a and the temperature compensation element 35b are housed in one metal case 33 composed of one condenser lens 21a, one metal can 31 and a metal stem 32, and are the same. Since it is arranged on the silicon substrate 34, the structure is such that a temperature difference is unlikely to occur between the pot detection element 35a and the temperature compensation element 35b. Therefore, the temperature disturbance energy Q5 generated by the pot detection element 35a and the temperature compensation element 35b has the same magnitude, and the timing of change is also the same.

From the above, the incident energy Q3 input to the pot detection element 35a, the incident energy Q3 input to the temperature compensation element 35b, the incident energy Q4 input to the pot detection element 35a, and the temperature compensation element 35b The input incident energy Q4, the temperature disturbance energy Q5 input to the pot detection element 35a, and the temperature disturbance energy Q5 input to the temperature compensation element 35b are equal to each other.

Since the pot detection element 35a and the temperature compensation element 35b are connected by the circuit shown in FIG. 7, the potential difference obtained by subtracting the output of the temperature compensation element 35b from the output of the pot detection element 35a is amplified. It is configured to output an electric signal. Therefore, the incident energy Q3, the incident energy Q4, and the temperature disturbance energy Q5 input by the pot detection element 35a and the temperature compensation element 35 as disturbances are input to the pot detection element 35a because their magnitudes and change timings are the same. The output of the pot detection element 35a due to the total incident energy Q = Q1 + Q2 + Q3 + Q4 + Q5 is corrected by the total incident energy Q = Q3 + Q4 + Q5 input to the temperature compensation element 35b, and the output of the pot detection element 35a is corrected by the temperature compensation element 35b. The electric signal output by amplifying the potential difference obtained by subtracting the output is the value obtained by amplifying the incident energy Q = Q1 + Q2 input to the pot detection element 35a.

Next, a method of converting the bottom temperature of the cooking pot 30 will be described.

Since the output of the infrared sensor 21 is an electric signal corresponding to the temperatures of the incident energy Q1 and the incident energy Q2, in order to obtain the temperature of the bottom of the cooking pot 30, the disturbance corresponding to the incident energy Q2 must be corrected. Therefore, more accurate temperature can be detected.

For the correction of the disturbance incident energy Q2, the output signal of the infrared sensor 21 according to the temperature of the top plate 2 measured by the temperature sensor 14b is set as the correction voltage V2 and registered in the temperature conversion means 50. The output signal V1 detected by the infrared sensor while heating the cooking pot 30 is input to the temperature conversion means 50, and the temperature of the top plate 2 measured by the temperature sensor 14b is input to the temperature conversion means 50 to calculate the correction voltage V2. By performing the conversion process of the output signal V1-correction voltage V2 in the temperature conversion means 50, the disturbance (incident energy Q2 from the top plate 2) can be excluded, and the accurate temperature of the pot bottom can be detected.

Further, in order to detect the temperature of the cooking pot 30, the amount of infrared rays emitted from the pot bottom differs depending on the material, color, scratches, etc. of the pot bottom even if the cooking pot 30 has the same temperature. Therefore, the infrared rays detected by the infrared sensor 21 The temperature of the cooking pot 30 cannot be uniquely obtained from the amount. In order to obtain the temperature of the bottom of the cooking pot 30, it is possible to correct the amount of infrared rays detected by obtaining the emissivity of the bottom of the pot and detect the accurate temperature.

The emissivity is derived from the equation (ε + ρ = 1) according to Kirchhof's law, which holds between the emissivity ε of the infrared energy (E = εσT ⁴ ) radiated from the surface of the metallic material and the reflectance ρ of the surface (however, transmission). If the reflectance ρ of the cooking pot 30 can be known (the emissivity α = 0), the emissivity ε of the pot 30 can be calculated. Here, σ is the Stefan-Boltzmann coefficient, and T is the absolute temperature. The reflectance of the bottom surface of the cooking pot 30 placed on the top plate 2 is measured by the reflective photo interrupter 22, and the emissivity of the cooking pot 30 is calculated by the temperature conversion means 50. In the temperature conversion means 50, the emissivity is multiplied by the output signal obtained by subtracting the correction voltage V2 obtained by converting the temperature of the temperature sensor 14b from the output signal V1 from the infrared sensor 21, so that the temperature conversion means is accurate according to the emissivity of the cooking pot 30. It is possible to detect the temperature of a hot pot.

Here, a method of heating the cooking pot 30 will be described with reference to a block diagram showing the configuration of the pot bottom temperature detecting means of FIG. The upper surface operation unit 6a includes a heating power setting means 52 for setting the heating power and a menu setting means 53 for selecting a cooking menu. Further, the inverter means 54 generates a voltage of several hundred V at a high frequency of several tens of kHz and supplies it to the heating coil 3.

The control means 51 controls the inverter means 54 so that the cooking pot 30 can be heated by the heat set by the heat power setting means 52, or selects a menu selected from the automatic menus preliminarily incorporated in the menu setting means 53. The inverter means 54 is controlled based on this. When the set temperature is selected by the menu setting means 53 and heating is started, the temperature of the cooking pot 30 is supplied to the heating coil 3 based on the information of the value converted by the temperature converting means 50 in order to maintain the temperature at the determined temperature. Control power. Further, when the cooking pot 30 is abnormally overheated, the control means 51 controls the heating power decrease, the stop signal, and the like based on the temperature information of the cooking pot 30 detected by the temperature conversion means 50, so that cooking can be performed safely.

As described above, the infrared sensor 21 of this embodiment has two heat sensitive elements (pot detection element 35a (first)) in one metal case 33 including one condenser lens 21a, one metal can 31 and a metal stem 32. (Heat sensitive element) and temperature compensation element 35b (second heat sensitive element) are provided, and the center 35a1 of the infrared receiving surface of the pot detection element 35a and the optical axis 21a1 passing through the center of the condensing lens 21a and perpendicular to the lens surface Infrared rays 35a2 incident parallel to the optical axis 21a1 are focused on the infrared receiving surface of the pot detection element 35a, and are located on the circumference of the pot detection element 35a and detect the pot. A temperature compensating element 35b is provided at a position adjacent to the element 35a, and the positional relationship between the infrared light receiving surface of the temperature compensating element 35b and the condensing lens 21a is such that the center of the infrared receiving surface of the temperature compensating element 35b and the condensing lens 21a. The following effects can be obtained by providing the infrared rays 35b2 incident parallel to the inclined optical axis 21a2 connecting the center with the lens 21a at a position where the infrared rays 35b2 are substantially focused on the infrared receiving surface of the temperature compensating element 35b.

Since the pan detection element 35a and the temperature compensation element 35b are housed in one metal case 33 composed of the same condensing lens 21a, one metal can 31, and a metal stem 32, the deviation due to heat transfer characteristics is caused. The temperature can be detected accurately without any problems.

Further, during the induced heating of the cooking pot 30, the pot temperature detection device 20 is transient between room temperature and + 20 ° C. due to the radiant heat from the heating coil 3 and the cooling air that cools the electronic components inside the main body. Although temperature fluctuation occurs, by canceling the output signal of the pot detection element 35a with the output signal of the temperature compensation element 35b, the output fluctuation due to the disturbance of the infrared sensor 21 can be suppressed, and the ambient temperature of the infrared sensor 21 changes. Even under the detection conditions, the temperature of the cooking pot 30 can be detected accurately. Further, if the infrared sensor 21 is used, the incident energy of the optical filter 26 heated by the radiant heat from the heating coil 3 can be canceled, so that the thermal disturbance from the optical filter 26 can be suppressed. Since the optical filter 26 also contributes to the suppression of thermal disturbance below the top plate 2, the incident energy from the top plate 2 and the optical filter 26, which is a disturbance, can be suppressed, so that the temperature of the cooking pan 30 can be detected accurately.

Further, in receiving infrared light from the pot detection element 35a and the temperature compensation element 35b, by using one condensing lens 21a in common, the pot detection element 35a and the temperature compensation element 35b can condense light. Since the temperature disturbance energy Q4, which is adversely affected by the lens 21a, is generated as the same amount of energy at the same time, it can be accurately corrected regardless of the magnitude of the temperature disturbance energy Q4. Further, regarding the temperature unevenness of the condenser lens 21a, the temperature disturbance energy Q4 is generated in the same time as the same amount of energy as the same temperature unevenness in the pot detection element 35a and the temperature compensation element 35b, so that there is no problem. Because it can be deleted accurately, the pot temperature can be detected accurately.

Therefore, the temperature of the cooking pot 30 can be accurately detected even under the conditions of long-time cooking, continuous cooking, and simultaneous cooking with the grill cooking in the cooking pot 30 where the ambient temperature of the infrared sensor 21 changes.

However, the output by Q3 + Q4 + Q5 of the total incident energy Q = Q1 + Q2 + Q3 + Q4 + Q5 input to the pan detection element 35a and the output by the total incident energy Q = Q3 + Q4 + Q5 input to the temperature compensation element 35b are when the incident energies are equal. Even if there is a difference in the sensitivity of each heat sensitive element, they are not equivalent. In this case, the potential difference obtained by subtracting the output of the temperature compensating element 35b from the output of the pot detection element 35a is amplified and the output electric signal is amplified by the incident energy Q = Q1 + Q2 input to the pot detection element 35a. The electrical signal is affected by the difference in sensitivity with respect to Q3 + Q4 + Q5.

FIG. 12 is an example of the detection circuit of the present invention.

The detection circuit 40 of the infrared sensor 21 uses an arbitrarily set reference potential 70, a first amplifier 61 that uses the reference potential 70 as a first bias input and amplifies the output of the pot detection element 35a, and a reference potential 70. The second amplifier 62 that amplifies the output of the temperature compensating element 35b as the first bias input, and the amplification output 74 of the temperature compensating element 35b as the second bias input amplifies the amplification output 73 of the pot detection element 35a. It is composed of a third amplifier 63.

The reference potential (V0) 70 can be set by the power supply voltage (Vc) 76, the voltage dividing resistor (R01) 80, and the voltage dividing resistor (R02) 81.
V0 = Vc × R02 / (R01 + R02)
Can be calculated. Even if the reference potential (V0) 70 is connected to the circuit ground 77 without using the voltage dividing resistor, the detection circuit of the present invention can be operated and the noise resistance performance of the detection circuit can be improved.

In the first amplifier 61, the amplification factor k1 can be set by the amplification factor setting resistor (R11) 82 and the amplification factor setting resistor (R12) 83, and the amplification output (V1') 73 of the pot detection element 35a is
V1'= (1 + R12 / R11) x V1 + V0 = k1 x V1 + V0
Can be done.

In the second amplifier 62, the amplification factor k2 can be set by the amplification factor setting resistor (R21) 84 and the amplification factor setting resistor (R22) 85, and the amplification output (V2') 74 of the pot detection element 35b can be set.
V2'= (1 + R22 / R21) x V2 + V0 = k2 x V2 + V0
Can be done.

Further, in the third amplifier 63, the amplification factor k3 can be set by the amplification factor setting resistor (R31) 86 and the amplification factor setting resistor (R32) 87, and the output voltage (Vs) 75 of the detection circuit can be set.
Vs = (1 + R32 / R31) x (V1'-V2') + V2'
= K3 × (V1'-V2') + V2'
= K3 × (k1 × V1 + V0-k2 × V2-V0) + k2 × V2 + V0
= K3 x {k1 x V1-k2 x V2 + (k2 / k3) x V2} + V0
Can be done.

In the above formula, for the second and third terms in parentheses,
-K2 x V2 + (k2 / k3) x V2
=-{K2 × (1-1 / k3)} × V2
= -K2 x V2
Can be transformed. Here, when amplifying the output of the thermal element, it is generally used that the amplification factor is k3 >> 1.

Therefore, the output voltage (Vs) 75 of the detection circuit is
Vs = k3 x {k1 x V1-k2 x V2 + (k2 / k3) x V2} + V0
= K3 × (k1 × V1-k2 × V2) + V0
Can be done.

The outputs of the pot detection element 35a and the temperature compensation element 35b can be corrected by the amplification factors k1 and the amplification factor k2, and then the detection circuit output can be obtained at the amplification factor k3.

For example, when the sensitivity of the temperature compensation element 35b is 0.8 times the sensitivity of the pot detection element 35a, the sensitivity can be set by setting the amplification factor k2 = 1.25 times and the amplification factor k1 = 1 times. The difference can be corrected. When it is desired to increase the amplification factor k1 to 1, the amplification factor setting resistor (R12) 83 is set to 0Ω (jumper connection), and the OP amplifier 41 is used as a buffer.

As described above, even if there is a difference in sensitivity between the pot detection element 35a and the temperature compensation element 35b of the infrared sensor 21, the difference in sensitivity can be corrected by the detection circuit of the present invention, so that in the cooking pot 30 where the ambient temperature changes. Even when the change of incident energy Q3 + Q4 + Q5 becomes a problem under the conditions of long-time cooking, continuous cooking, simultaneous cooking with grill cooking, etc., the temperature of the cooking pan 30 can be detected more accurately.

FIG. 13 is another embodiment of the detection circuit of the present invention. A similar detection circuit can also be used in a method in which the infrared sensor 21 is composed of one heat sensitive element and two infrared sensors 21 are connected in opposite directions.

1 ... Main body of induction heating cooker 2 ... Top plate 3 ... Heating coil 3a ... Inner heating coil, 3b ... Gap, 3c ... Outer heating coil 4 ... Mounting part 5 ... Infrared transmission window 6a, 6b, 6c ... Top operation part 7a, 7b, 7c ... Top display part 8 ... Grill storage, 8a ... Handle, 8b ... Grill door 9 ... Main power switch 10 ... Front operation part 11 ... Exhaust port 12 ... Coil base 13 ... Gap spacer, 13a ... Support member 14 ... Temperature sensor, 14a ... Inner temperature sensor, 14b, 14c ... Outer temperature sensor,
20 ... Pot temperature detector 21 ... Infrared sensor, 21a ... Condensing lens 22 ... Reflective photo interrupter, 22a ... Infrared LED,
22b ... Infrared phototransistor 23 ... Electronic circuit board 24 ... Sensor case 25 ... Case window 26 ... Optical filter 27 ... Metal case 28 ... Light guide tube 30 ... Cooking pot 31 ... Metal can 32 ... Metal stem 33 ... Metal case 34 ... Silicon Substrate 35a ... Pot detection element (first heat sensitive element)
35b ... Temperature compensation element (second heat sensitive element)
36 ... Metal pin 37 ... Opening 38 ... Detection range of pot detection element 35a, 38a ... Peak sensitivity position 39 ... Detection range of temperature compensation element 35b, 39a ... Peak sensitivity position 40 ... Detection circuit 41 ... OP amplifier 50 ... Temperature conversion means 51 ... Control means 52 ... Thermal power setting means 53 ... Menu setting means 54 ... Inverter means 61 ... First amplifier 62 ... Second amplifier 63 ... Third amplifier 70 ... Reference potential (V0) (First Bias input)
71 ... Output voltage (V1) of the pan detection element 35a
72 ... Output voltage (-V2) of temperature compensating element 35b
73 ... Amplified output (V1') of the pan detection element 35a
74 ... Amplified output (V2') of temperature compensating element 35b (second bias input)
75 ... Output voltage (Vs) of detection circuit
76 ... Power supply voltage (Vc)
77 ... Circuit ground 80 ... Voltage dividing resistor (R01)
81 ... Voltage dividing resistor (R02)
82 ... Amplification rate setting resistor (R11)
83 ... Amplification rate setting resistor (R12)
84 ... Amplification rate setting resistor (R21)
85 ... Amplification rate setting resistor (R22)
86 ... Amplification rate setting resistor (R31)
87 ... Amplification rate setting resistor (R32)

Claims (3)

A top plate on which the cooking pot is placed on the top and
A heating coil provided below the top plate to generate an induced magnetic field to heat the cooking pot,
Inverter means for supplying electric power to the heating coil and
An infrared sensor that detects the temperature of the cooking pot through the top plate,
A detection circuit that amplifies the output of the infrared sensor,
In an induction heating cooker provided with a control means for controlling the output of the inverter means according to the output of the detection circuit.
The infrared sensor includes a first heat sensitive element and a second heat sensitive element in the same metal case.
The detection circuit has an arbitrarily set reference potential, a first amplifier that uses the reference potential as a first bias input to amplify the output of the first heat-sensitive element, and a first bias input that uses the reference potential as a first bias input. A second amplifier that amplifies the output of the second heat-sensitive element, and a third amplifier that amplifies the amplified output of the first heat-sensitive element by using the amplified output of the second heat-sensitive element as a second bias input. An induction heating cooker characterized by being equipped with. In the induction heating cooker according to claim 1,
An induction heating cooker characterized in that the first heat-sensitive element and the second heat-sensitive element are arranged on one chip. In the induction heating cooker according to claim 1 or 2.
It is provided between the top plate and the second case, and includes a cylinder through which infrared rays passing through a window provided on the top plate pass.
The peak sensitivity position where the relative sensitivity in the visual field range of the first heat sensitive element is maximized is the position where the cooking pot is detected.
An induction heating cooker characterized in that the peak sensitivity position where the relative sensitivity in the visual field range of the second heat sensitive element is maximized is a position where the inner wall of the cylinder is detected.

Images