WO2011132614A1 - Induction cooker - Google Patents

Abstract

Disclosed is an induction cooker which supplies an appropriate high-frequency current to a heating coil by detecting the surface temperature of a pan, which is the object to be heated, accurately and with good responsiveness. The disclosed induction cooker is provided with: a top plate, onto which the object to be heated is placed at a specified interval (δ_ａ) therefrom; a heating coil which is arranged below the top plate and which induction heats the object to be heated; a drive circuit which supplies a high-frequency current to the heating coil; a temperature sensor which is arranged below the top plate and which detects the temperature (T_g) of the top plate; a temperature estimation circuit which calculates the change rate over time (∂T_ｇ／∂ t) of the top plate temperature (T_g) detected by the temperature sensor, and estimates the temperature (T_p) of the surface of the object to be heated on the basis of the interval (δ_ａ) and the change rate over time (∂T_ｇ／∂ t); and a control unit which uses the estimated temperature (T_p) estimated by the temperature estimation circuit to control the drive circuit.

Description

Induction heating cooker

The present invention relates to an induction heating cooking appliance, and particularly to an induction heating cooking appliance capable of accurately estimating the surface temperature of a heated object such as a pan and heating the heated object at an appropriate temperature.

In conventional induction cooking equipment, there has been a strong market demand for the realization of an optimal cooking method by accurately measuring the surface temperature of the pan and supplying appropriate power to the heating coil based on this measurement. Many conventional induction cooking appliances generally measure the temperature of the top plate using a thermal element (contact temperature sensor) such as a thermistor or thermocouple that is in direct contact with the lower surface of the top plate, and are in a thermal equilibrium state. The surface temperature of the pan is detected from the temperature of the top plate based on the fact that the temperature of the top plate and the surface temperature of the pan have a certain relationship.

On the other hand, it passes through a top plate using optical sensors (optical temperature sensor), such as an infrared sensor arrange | positioned under the top plate like the induction heating cooking appliance of patent document 1, for example. Some have been proposed that detect the surface temperature of a pan by measuring radiant energy such as infrared rays.
Japanese Patent Laid-Open No. 2004-227976 (FIG. 1)

However, the temperature of the top plate measured using a contact-type temperature sensor does not reflect the surface temperature of the pan in real time because of the large thermal resistance and heat capacity of the top plate made of heat-resistant glass, etc. Immediately after the start of heating, the surface temperature of the pan detected from the temperature of the top plate rises behind the actual surface temperature of the pan, so that the power supply to the heating coil could not be properly controlled.

On the other hand, the optical temperature sensor utilizes the fact that the radiant energy from a high-temperature object is proportional to the fourth power of the surface temperature. In particular, the temperature reached by the pan surface during normal practical cooking (about 150 ° C.) At the following relatively low temperatures, the radiant energy from the surface of the pan was so small that the surface temperature of the pan could not be accurately detected. That is, when the surface temperature of the pan detected using the optical temperature sensor is lower than the practical cooking temperature (immediately after the start of heating), the temperature detection accuracy is low, and the heating coil is the same as when using the contact temperature sensor. It was not possible to accurately control the power supply to the. In addition, detecting the temperature using an optical temperature sensor is likely to impair the detection accuracy due to, for example, the surface condition of the pan (stained, glossy, etc.), and may be affected by other thermal power, contents, and the surrounding environment. It was easy to receive, making accurate detection of the surface temperature of the pan more difficult.

The present invention has been made in order to solve the above-described problems, and is provided with a top plate on which _a heated object is placed at _a predetermined interval (δ _a ) and a lower portion of the top plate. A heating coil that induction-heats the object to be heated, a drive circuit that supplies a high-frequency current to the heating coil, and a temperature sensor that is disposed below the top plate and detects the temperature (T _g ) of the top plate And a time change rate (∂T _g / ∂t) of the temperature (T _g ) of the top plate detected by the temperature sensor, and the interval (δ _a ) and the time change rate (∂T _g / ∂t) based on the temperature estimation circuit that estimates the surface temperature (T _p ) of the heated object, and the drive circuit is controlled using the estimated temperature (T _p ) estimated by the temperature estimation circuit With a control unit There is provided an electrically heated cooker.

According to the induction heating cooker according to the present invention, it is possible to supply an appropriate high-frequency current to the heating coil by detecting the surface temperature of the pan, which is the object to be heated, accurately and responsively (in real time). .

It is a perspective view showing the whole induction heating cooking appliance concerning the present invention roughly. It is the expanded sectional view seen from the II-II line of the induction heating cooking appliance of FIG. FIG. 3 is an enlarged partial sectional view in which a region indicated by a broken line in FIG. 2 is enlarged. It is a graph which shows the time transition of the estimated temperature of a pan estimated based on the measured temperature of a top plate by this invention with respect to the measured temperature of a pan. FIG. 3 is an enlarged partial sectional view in which a region indicated by a one-dot chain line in FIG. 2 is enlarged. 1 is a circuit block diagram of an induction heating cooker according to Embodiment 1. FIG. In a boiling test, it is a graph which shows the time transition of the estimated temperature of a pot, the measured temperature of foodstuffs, the measured temperature of a top plate, and the estimated temperature of the pot estimated at different intervals. 6 is a circuit block diagram of induction heating cooker 1 according to Embodiment 3. FIG. It is a schematic perspective view similar to FIG. 1 of the induction heating cooking appliance 1 by Embodiment 3, Comprising: A displacement detection area | region is shown. It is a circuit block diagram similar to FIG. 6 of the induction heating cooking appliance 1 by Embodiment 3. It is an example of the temperature sensor using a thermistor.

DESCRIPTION OF SYMBOLS 1 ... Induction heating cooker, 2 ... Case, 3 ... Top plate, 4 ... IH heating part, 5 ... Radiant heating part, 6 ... Grill part, 7 ... Operation panel, 8 ... Thermal power adjustment dial, 9 ... Liquid crystal display part , 20... Heating coil, 25... Projection, 26 and 27... Projection, 28 .. spacer for gap definition (interval maintaining means), 30... Temperature sensor, 40. , 70 ... Setting equipment, 80 ... Warning equipment, 90 ... Displacement sensor, 92 ... Displacement detection area, 94 ... Protection tube (disturbance suppression container or magnetic shield pipe), 100 ... Thermistor, 101 ... High heat transfer structure, 102 ... Folder DESCRIPTION OF SYMBOLS 103 ... Spring, 104 ... Insulator, 105 ... Rib, P ... To-be-heated body (pan, frying pan), B ... Bottom plate of to-be-heated body, A ... Air layer.

Hereinafter, an embodiment of an induction heating cooker according to the present invention will be described with reference to the accompanying drawings. In the description of each embodiment, terms indicating directions (for example, “upward” and “downward”) are used as appropriate for easy understanding. It does not limit the present invention. In the accompanying drawings, the same components are referred to by the same reference numerals.

Embodiment 1 FIG.
A first embodiment of the induction heating cooker according to the present invention will be described in detail below with reference to FIGS. FIG. 1 is a perspective view schematically illustrating the entire induction heating cooker 1 according to the present invention. An induction heating cooker 1 shown in FIG. 1 schematically includes a casing 2, a top plate 3 formed of heat-resistant glass or the like covering substantially the entire upper surface thereof, and a pair of induction heating type disposed symmetrically. It has IH heating units 4a and 4b, a radiant heating type radial heating unit 5, and a grill unit 6 suitable for cooking fish and the like. Each IH heating section 4a, 4b has a heating coil 20 (FIG. 2) that is spirally wound in parallel with the top plate 3.

In the following embodiments, the induction heating cooker 1 having a so-called side grill structure in which the grill portion 6 is arranged to be biased to the left side of the housing 2 will be described as an example, but the present invention is limited to this. In addition, the present invention can be equally applied to an induction heating cooker having a center grill structure in which the grill portion 6 is disposed at substantially the center of the housing 2 or an induction heating cooker that does not include the grill portion 6.
In addition, the radiant heating unit 5 may be an IH heating unit or may have a configuration similar to that of the IH heating units 4a and 4b.

The induction heating cooker 1 also includes an operation panel 7 and heating power adjustment dials 8a, 8b, and 8c used by the user to operate the IH heating units 4a and 4b, the radiant heating unit 5 and the grill unit 6, and controls thereof. A liquid crystal display unit 9 for displaying the state is provided. Furthermore, the induction heating cooker 1 has an intake hole 10 and an exhaust hole 11 provided on the top plate 3 adjacent to the rear wall of the housing 2.

FIG. 2 is an enlarged cross-sectional view of the induction heating cooker 1 of FIG. 1 as viewed from the line II-II. A heated object P (hereinafter simply referred to as “pan”) is placed on the top plate 3. This shows the state. The induction heating cooker 1 according to the present invention has a temperature sensor 30 such as a thermistor disposed so as to abut on the lower surface of the top plate 3, and can measure the temperature (T _g ) of the top plate 3. it can.

As will be described in detail later, the induction heating cooker 1 includes a drive circuit (inverter circuit) 60 for supplying a high-frequency current to the heating coil 20 of each IH heating unit 4 and a top plate 3 measured by the temperature sensor 30. Based on the surface temperature of the pan P estimated from the temperature (T _g ) and the “heating power” (load heating value of the heating coil 20) set by the user with the heating power adjustment dial 8 or the like, an appropriate high-frequency current for the heating coil 20 The control circuit 50 controls the drive circuit 60 so as to supply (FIG. 6).

Next, a method (estimation principle) for estimating the surface temperature of the heated body P from the temperature (T _g ) of the top plate 3 measured by the temperature sensor 30 according to the present invention will be described with reference to FIG. FIG. 3 is an enlarged partial sectional view in which a region indicated by a broken line in FIG. 2 is enlarged.
When the control circuit 50 drives the drive circuit 60 according to a desired heating power set by the user using the operation panel 7 and the heating power adjustment dial 8 and supplies a high frequency current to the heating coil 20 provided below the pan P, An alternating magnetic field (closed magnetic path) including the bottom plate B of the pan P around the heating coil 20 is formed. At this time, an eddy current is formed near the surface of the bottom plate B of the pan P, and the bottom plate B of the pan P is heated by the Joule heat. That is, the pan P that is the object to be heated is directly induction heated.

The amount of heat generated when the bottom plate B of the pan P is heated cooks and heats the food F such as moisture contained in the pan P and is also transmitted to the top plate 3 below the bottom plate B. At this time, in particular, the bottom plate B (and the top plate 3) of the pan P cannot be formed to be completely flat (the flatness is zero) and has a minute curved shape. An air layer A having _a predetermined interval or gap (δ _a ) is formed therebetween.

Here heat is conducted from the lower surface of the bottom plate B of the pan P on the top plate 3 Q ₁ for _(i.e. the amount of heat Q ₁ to conduct air layer A is formed between the lower surface and the top plate 3 of the bottom plate B of the pan _P) Think. At this time, the amount of heat Q ₁ generally increases as the temperature difference (T _p −T _a ) between the temperature (T _p ) of the bottom plate B of the pan P and the surface temperature (T _a ) of the top plate 3 increases. The larger the area (S) to be processed is, the smaller the gap (δ _a ) is. The amount of heat Q ₁ also depends on the thermal conductivity (λ _a ) of the air layer A. Therefore, the amount of heat Q ₁ conducted per unit time from the lower surface of the bottom plate B of the pan P to the top plate 3 is expressed by the following equation.

Further, the amount of heat Q ₂ conducted to the top plate 3 is transmitted from the upper surface to the lower surface of the top plate 3. At this time, when the top plate 3 formed of heat-resistant glass or the like is viewed as a sensible heat storage material, the amount of stored heat Q ₂ is the mass (M), specific heat (c _g ), and temperature (T _g ) of the top plate 3. It is expressed by the following equation using the time change rate (∂T _g / ∂t).

Here, assuming that the thermal conductivity (λ _g ) of the top plate 3 is infinite (that is, T _a is equal to T _g , T _a = T _g ), the above equations (1) and (2) Since the amounts of heat Q ₁ and Q ₂ (Q ₁ = Q ₂ ) on the left side are equal, the following equation can be obtained by arranging them together.

T _p : Estimated temperature of pan P T _g : Temperature of top plate measured by temperature sensor δ _a : Spacing between pan P and top plate ρ _g : Density of top plate c _g : Specific heat of top plate δ _g : Top plate thickness λ _a : Thermal conductivity of air That is, since the coefficient C is a constant uniquely determined by the top plate 3, the temperature T _p of the bottom plate B of the pan P is the lower surface of the bottom plate B of the pan P The distance (δ _a ) of the air layer A formed between the top plate 3 and the temperature T _g of the top plate 3 measured by the temperature sensor 30 and the rate of change over time (∂T _g / ∂t) are used. Can be expressed.

As described above, the following evaluation experiment was performed in order to verify that the relationship shown in the above equation (3) holds even if the thermal conductivity (λ _g ) of the top plate 3 is assumed to be infinite. .
That is, when the pan P is induction-heated by the heating coil 20,
i) the measured temperature (T _g ) of the top plate 3 measured by the temperature sensor 30;
ii) the actual temperature of the pan P measured by another temperature sensor (not shown),
iii) The estimated temperature of the pan P obtained by the above equation (3) was compared.
FIG. 4 is a graph obtained by plotting the temporal transition of the above i) to iii). At this time, a spacer (thickness: 1.5 mm) is arranged between the pan P and the top plate 3 so that the interval (δ _a ) of the air layer A is defined as 1.5 mm, and the heating coil 20 has a high frequency for 250 seconds. After supplying the current to heat the pan P, the power supply to the heating coil 20 was stopped.

As is apparent from the graph of FIG. 4, when 250 seconds have elapsed since the start of heating, the actual temperature of the pan P has reached 200 ° C. or higher, whereas the actual temperature (T _g ) of the top plate 3 measured by the temperature sensor 30. ) Is about 70 ° C., there is a temperature difference of about 130 ° C. or more between the two, and the response is very poor.
On the other hand, the estimated temperature of the pan P obtained by the above equation (3) generally approximates (estimates) the measured temperature of the pan P immediately after the start of heating with good followability. Therefore, according to the method for estimating the temperature of the object to be heated according to the present invention defined by the above formula (3), the surface temperature of the pan P is estimated from the measured temperature (T _g ) of the top plate 3 very precisely with good followability. It was confirmed from the graph of FIG.

As described above, the actual thermal conductivity (λ _g ) of the glass that is the constituent material of the top plate 3 is about 1 W / (m · K), but is assumed to be infinite. Although the formula (3) was derived, it was confirmed that the estimated temperature of the pan P obtained based on the above formula (3) accurately approximates the actually measured temperature of the pan P.
In other words, the density, specific heat, and thickness of the glass constituting the top plate 3 are design matters and are known (the coefficient C is uniquely determined), so that the distance between the pan P and the top plate 3 ( δ _a ), the measured temperature (T _g ) of the top plate 3 and the rate of change over time (∂T _g / ∂t), the temperature of the pan P can be accurately tracked using the above equation (3) (in real time) ) Can be estimated accurately.

FIG. 5 is an enlarged partial sectional view in which a region indicated by a one-dot chain line 24 in FIG. 2 is enlarged. When the distance (δ _a ) between the bottom plate B of the pan P and the top plate 3 varies widely in the entire region of the bottom plate B of the pan P, the variation in Joule heat generated by the region (part) of the heating coil 20 also increases. . When the interval (δ _a ) varies depending on the position where the pan P is placed, the estimated temperature of the pan P obtained by the above equation (3) also varies. Therefore, it is preferable to process the bottom plate B and the top plate 3 of the pan P so as to have high flatness, and it is preferable to maintain or define the distance (δ _a ) as constant as possible.

Therefore, as shown in FIG. 5, in order to uniformly define the interval (δ _a ), the top plate 3 and the bottom plate of the pan P are processed into a shape with high flatness, and a plurality of pieces are formed on the peripheral portion of the bottom plate B of the pan P. The protruding portion 25 (FIG. 5A) or the protruding portion 26 (FIG. 5B) may be formed.
Alternatively, the top plate 3 may be provided with the protrusions 27 (FIG. 5C) at a plurality of positions. At this time, since the position of the pan P placed on the top plate 3 and the size of the pan P are different, the protrusions 27 on the top plate 3 are preferably disposed at various positions in the radial direction. . Further, a ridge shape (not shown) extending radially from the center of the IH heating unit 4 may be used.

Further alternatively, when placing the pan P on the top plate 3, a flat plate or a ring plate 28 (FIG. 5 (d)) having a certain thickness is used as the gap regulating spacer (interval maintaining means). And the top plate 3 may be interposed. The gap defining spacer 28 may be formed using a rigid material or a flexible material.
By configuring the pan P, the top plate 3 or the gap regulating spacer 28 (interval maintaining means) as described above, the interval (δ _a ) between the bottom plate B of the pan P and the top plate 3 is known constant. The value of

FIG. 6 is a circuit block diagram of the induction heating cooker 1 according to the first embodiment of the present invention. As described above, the induction heating cooker 1 includes a drive circuit (inverter circuit) 60 for supplying a high-frequency current to the heating coil 20 and a temperature sensor 30 such as a thermistor for measuring the temperature (T _g ) of the top plate 3. And a temperature estimation circuit 40 that estimates the surface temperature of the pan P from the measured temperature (T _g ) of the top plate 3. Further, the induction heating cooker 1 has a drive circuit so that an appropriate high-frequency current is supplied to the heating coil 20 based on the “heating power” (load heat generation amount) set by the user with the setting device 70 such as the heating power adjustment dial 8. 60 has a control circuit 50 for controlling 60. The control circuit 50 according to the present invention receives information about the temperature (T _p ) of the pan P, which is precisely estimated with good followability as described above, from the temperature estimation circuit 40 so that a more accurate high-frequency current is supplied. The drive circuit 60 is controlled.
The induction heating cooker 1 is preferably described in detail later, but when it is detected that the estimated temperature of the pan P is abnormally high, such as when the estimated temperature of the pan P reaches an abnormally high temperature, A warning device 80 such as a liquid crystal display unit 9 for displaying a beep or a warning display for receiving a warning signal from 50 and generating a warning sound for giving a warning to the user.

The operation of the induction heating cooker 1 according to the present invention will be described with reference to FIG. When the user places a heated object P such as a pan or a frying pan on the top plate 3 and the heating power is set by the setting device 70 such as the operation panel 7 and the heating power adjustment dial 8, the control circuit 50 responds accordingly. The drive circuit 60 is controlled to supply a high frequency current to the heating coil 20. When a high frequency current is supplied to the heating coil 20, a high frequency magnetic field is generated around the heating coil 20, an eddy current is generated in the bottom plate B of the pan P, and the pan P is heated by the Joule heat. The heat generated in the bottom plate B of the pan P by induction heating is transmitted from the pan P to the food F, and the food F is cooked.

On the other hand, the heat generated in the bottom plate B of the pan P is transmitted to the top plate 3 through the air layer A formed therebelow to raise the temperature of the top plate 3. The temperature sensor 30 provided below the top plate 3 continuously measures the temperature (T _g ) of the top plate 3 and transmits the measurement signal to the temperature estimation circuit 40.
And the temperature estimation circuit 40 calculates the time change rate of the temperature (T _g ) based on the measurement signal from the temperature sensor 30 as described above, and the known interval between the pan P and the top plate 3 ( The surface temperature of the pan P is estimated using δ _a ), and the signal is transmitted to the control circuit 50.

The control circuit 50 calls a drive program (default value) stored in a memory (not shown) built in the control circuit 50 in accordance with the input signal set by the setting device 70, and based on this drive program A driving signal is transmitted to the driving circuit 60 and, if necessary, a warning signal is supplied to the warning device 80 to give a warning to the user.

The drive circuit 60 drives a semiconductor switching element such as an IGBT by a drive signal from the control circuit 50, supplies an appropriate high-frequency current to the heating coil 20, and according to an input signal set by the setting device 70. Adjust the heating power to the pan P. The warning device 80 gives a warning to the user based on a warning signal from the control circuit 50.

As described above, the control circuit 50 according to the present invention repeatedly monitors the setting signal from the setting device 70 and the measurement signal from the temperature sensor 30 in the above-described series of operations, so that the cooking state desired by the user is obtained. The drive circuit 60 can be controlled to maintain the above.

According to the prior art, as shown in the graph of FIG. 4, since the measured temperature (T _g ) of the top plate does not change responsively to the measured temperature of the pan P, the accurate temperature of the pan P can be detected in real time. The cooking state desired by the user cannot always be realized. For example, although the actual temperature of the pan P is sufficiently high and the food F is boiling, the pan P may be heated excessively to cause spillage.

However, according to the present invention, by using the time change rate (∂T _g / ∂t) of the measured temperature (T _g ) of the top plate as a new parameter, the responsiveness of the estimated temperature of the pan P is increased and actually Since the temperature can be approximated by the temperature of the pan P, the user can grasp the desired cooking state with good followability.

The top plate 3 is generally a translucent glass plate. However, when a contact temperature sensor such as a thermistor is used in the present invention, a non-translucent glass plate may be used. In addition, the temperature of the pan P can be accurately detected with good responsiveness. Therefore, according to the present invention, it is possible to improve the design by forming a non-translucent film (paint) on the surface of the top plate 3, and the top plate 3 can be colored glass material, resin material, ceramic. It is also possible to improve the heat resistance and impact resistance by using a material and a clad material (for example, a laminated structure in which the surface is made of glass and the back is made of resin or the like, a glass base resin laminated plate).

In particular, resin materials and ceramic materials have excellent impact resistance and moldability, can suppress cracking (crushing) of the top plate 3, and have various shapes (concave shapes, convex shapes, curved shapes at corners). Etc.), and can be formed integrally with a frame member provided on the peripheral portion (not shown) of the top plate 3, thereby reducing the number of parts and manufacturing. Cost can also be reduced.

In addition, by producing the top plate 3 using a material having excellent formability, moisture is generated when the food F is blown out on the surface of the top plate 3 to guide the proper placement position of the pan P or the food F. Concavities and convexities that constitute guides or flow paths for guiding the above can be easily formed. Furthermore, by forming Braille on the top plate 3, it is possible to provide the induction heating cooker 1 that is easy to use even for visually impaired persons.

Here, the ingredients contained in the heated object P such as a pan are foods such as water, soup stock, oil, vegetables, meat and fish. Moreover, the to-be-heated body P means what accommodates the said foodstuffs, such as a pan, a frying pan, a kettle which can be heated by induction heating.

The setting device 70 refers to the operation state of the induction heating cooker 1 such as an ON / OFF switch of a power source, a cooking mode, a thermal power mode, or a pan temperature selection switch in addition to the operation panel 7 and the thermal power adjustment dial 8 described above. This means that a signal for setting is input to the control circuit 50.

For example, when the cooking mode is selected and input from a number of menus stored in advance in the memory of the control circuit 50 using the cooking mode selection switch, the pan P estimated by the temperature estimation circuit 40 according to the present invention is used. On the basis of the temperature (T _p ), the heating power may be adjusted according to the cooking program of the rice cooking mode stored in the memory. Also, select the fried food cooking mode with the cooking mode selection switch, set the pan temperature to “180” ° C. using the pan temperature selection switch, and adjust the heating power so that the oil temperature is kept constant. You can also.

The induction heating cooker 1 also has a communication device (communication cable, infrared sensor, etc.) that enables communication with a slot that accepts an electronic storage medium (SD card, USB) or an external PC or mobile phone as the setting device 70. ) May be included.

The warning device 80 is a warning when the safety standard is deviated by using sounds such as synthetic voice, beep sound, melody, etc. in addition to the liquid crystal display unit 9 or using light such as lighting / flashing of light. Or something that informs the user of the cooking status. Moreover, you may make it display the temperature of the actual pan P in the liquid crystal display part 9 in real time so that it can compare with the temperature of the pan P set with the setting apparatus 70 by the user. Further, the progress of cooking may be displayed on the liquid crystal display unit 9.

As the temperature sensor 30 according to the present invention, in addition to the thermistor (which estimates the temperature by utilizing the characteristic that the electrical resistance of the semiconductor changes depending on the temperature), any sensor can be used as long as it can measure the temperature of the top plate 3 ( Contact temperature sensors and optical temperature sensors) can be used. A contact-type temperature sensor uses, for example, a thermocouple (a weak thermoelectromotive force generated according to the temperature difference between the two ends when a temperature is applied to the joint with a temperature sensor in which one end of two types of metal wires having different properties is joined. Temperature sensor), resistance thermometer (if the material is metal, the temperature is estimated using the property that the electrical resistance increases in proportion to the temperature), radiation thermometer (the object radiates) Infrared energy received by an infrared sensor, and a reference temperature correction, emissivity correction, etc. are applied to estimate the temperature). When the temperature of the pan P is measured using a radiation thermometer of an optical temperature sensor, a film (painting or the like) that suppresses transmission of infrared light may be formed on the lower surface of the top plate 3.

Embodiment 2. FIG.
Embodiment 2 of the induction heating cooker according to the present invention will be described in detail below with reference to FIG. In the induction heating cooker 1 according to the first embodiment, the pan 25 and the top plate 3 are provided with the protrusion 25, the protrusions 26 and 27, or the gap-defining spacer 28 having a known thickness in order to define the interval (δ _a ). However, the induction heating cooker 1 of the second embodiment performs a boiling test for each pot P used to measure and store an appropriate interval (δ _a ). Since it has the same configuration as the electromagnetic cooker 1 of the first embodiment except for the points to be described, the description of the overlapping points is omitted.

As described above, the induction heating cooker 1 according to the second embodiment performs a boiling test in advance before actually using a new pan P, and measures and stores an appropriate interval (δ _a ). It is configured as follows.

First, the boiling test will be described below. Water is put into the pan P and the pan P is heated with a constant heating power. After the temperature of the water stored in the pan P gradually rises and reaches 100 ° C., the water is maintained in a boiling state (100 ° C.), and all the Joule heat generated in the bottom plate B of the pan P is vaporized. Since it is consumed as heat, the temperature of the bottom plate B of the pan P also converges to a constant value.

FIG. 7 shows the measured temperature of water when the pan P containing water is heated for about 12 minutes with a constant heating power, the temperature (T _g ) of the top plate 3 measured by the temperature sensor 30, and another temperature sensor (not shown). 3) is a graph plotting the temporal transition of the temperature of the pan P actually measured in (1). FIG. 7 plots the transition of three types of estimated temperatures T1, T2, and T3.

In the graph of FIG. 7, the temperature of water reaches a boiling state of 100 ° C. after 130 seconds, and similarly the measured temperature of the pan P rises steeply until 130 seconds, and then enters a thermal equilibrium state to reach a substantially constant temperature (about approximately 135 ° C.). The measured temperature (T _g ) of the top plate rises gently as in the graph of FIG. 4, but reaches the measured temperature (about 135 ° C.) of the pan P after about 12 minutes.

On the other hand, three types of estimated temperatures T1, T2, and T3 are calculated based on the measured temperature (T _g ) of the top plate 3 and its time change rate (∂T _g / ∂t) using the above equation (3). The temperature of P is estimated, but different values are used for the interval (δ _a ) between the pan P and the top plate 3. That is, the estimated temperature T1 is estimated using an interval (δ _a ) that is larger than the actual temperature, and after the substantial time has passed after the peak (maximum point) is exceeded, the estimated temperature T1 is changed to the measured temperature of the pan P. The estimated temperature T2 was estimated using _a smaller interval (δ _a ) than the actual temperature, and it took a considerable time to approach the measured temperature of the pan P asymptotically.

On the other hand, the estimated temperature T3 is estimated using a value that most closely matches the actual interval (δ _a ), and converges to the measured temperature of the pan P most rapidly (after 130 seconds). .

In other words, in the boiling test, the interval (δ _a ) when the estimated temperature according to the above equation (3) converges to the predetermined temperature (the measured temperature of the pan P in an equilibrium state) in the shortest time is the pan P and the top plate. 3 is considered to represent the actual spacing between the two.
Specifically, the temperature estimation circuit 40 determines the time until the estimated temperature (T _p ) is determined to converge to a predetermined temperature (for example, the 10-second fluctuation of the estimated temperature is plus or minus 1 ° C. with respect to the predetermined temperature). The interval (δ _a ) that minimizes the time until it is determined that the transition is made in the range of () is determined, and this is a characteristic characteristic of the pan P, and is associated with the pan P in the temperature estimation circuit 40. (Not shown).

Thus, the interval (δ _a ) once associated with the pan P and recorded in the memory is called to the temperature estimation circuit 40 when the pan P is specified by the setting device 70 in use after the boiling test. Then, the temperature estimation circuit 40 sets the interval (δ _a ) individually measured for the pan P in the boiling test, the measured temperature (T _g ) of the top plate 3, and the rate of change over time (∂T _g / ∂t). Based on the above equation (3), the surface temperature of the pan P can be estimated precisely.

Referring to FIG. 7 again, the temperature of the water contained in the pot P increased with a large temperature gradient until about 130 seconds, but after about 130 seconds, the temperature gradient became 0, and the temperature was 100 ° C. (boiling). ). The estimated temperature using an appropriate interval (δ _a ) according to the present invention changes in response to the measured temperature of the pan P, although the temperature changes with a gentle temperature rise gradient in about 110 to about 130 seconds.

Also, the temperature of the pan P increased with a large temperature gradient until about 100 seconds, but after about 100 seconds, the temperature gradient was almost 0, and the temperature converged at 135 ° C. These show that subcooled boiling occurred from about 80 to about 100 seconds and saturated boiling after about 100 seconds. Although there was a time lag, the measured temperature of the pan P, the measured temperature of water, and The estimated temperature of the pan P according to the present invention has a temperature gradient of 0 when boiling starts. Therefore, according to the present invention, it is possible to detect the start of boiling when the estimated temperature gradient changes suddenly or when the temperature gradient becomes almost zero.

Thus, by detecting the boiling, the boiling state is detected in actual cooking, boiling water, boiling disinfection, etc., and the heating coil 20 is optimally driven by the control circuit 50 to adjust the heating power, thereby preventing excessive heating and saving energy. It is possible to improve, and spillage and liquid scattering can be suppressed.

As described above, according to the present invention, in the boiling test, the pan P filled with water is placed on the top plate 3, heated by the heating coil 20, and based on the temperature detected by the temperature sensor 30. estimating a distance ([delta] _a) between the bottom plate B and the top plate 3 of the pot P, since the memory as a characteristic of the pan P, in an actual cooking of boiled testing, proper spacing of pots P according ([delta] _a ) Can be used to accurately estimate the surface temperature of the pan P.

Further, from the transient temperature change predicted based on the three different intervals (δ _a ) shown in FIG. 7, when the appropriate interval (δ _a ) is used, the temperature increase gradient after the start of boiling becomes zero and is constant. Although temperature is shown, when a gap larger than actual is used, it gradually approaches the measured temperature of the pan P while decreasing in a convex curve downward after overshoot. On the other hand, when a gap smaller than the actual one is used, the gradient change of the temperature rise before and after boiling becomes gentle and gradually approaches the measured temperature of the pan P while rising in a convex curve. As described above, when a gap that is not appropriate is used, the temperature changes even after boiling, so that the gap can be corrected using this relationship.

In this way, by performing a boiling test on each pan P in advance, the interval (δ _a ) unique to the pan P is measured and stored, so that the stored data is used when actually cooking. The temperature of the pan P can be accurately measured. Further, by periodically measuring and updating the stored data, errors due to changes in the pan P over time, such as deformation of the pan P and adhesion of dirt, can be reduced.

In addition, the interval (δ _a ) between the bottom plate B and the top plate 3 of the normal pan P is about 0.3 to 0.8 mm, and by setting 0.5 mm as the specified value (default value), Temperature detection suitable for actual use is possible. When the bottom plate B of the pan P is deformed from the beginning (warp pan or the like) or deforms due to use, for example, a calibration button (not shown) provided on the setting device 70 is pushed, and only the specific pan P is pressed. You may calibrate by the said boiling test. This operation is memorized about pan a, pan b, pan c, etc., and the temperature detection suitable for each pan P can be performed by reading the setting of pan B that is actually desired to be used from the setting device.
In addition, although the said method was described as a method calibrated beforehand as a boiling test, it can be implemented also at the time of an actual cooking, and you may optimize _a space | interval ((delta) _a ) at any time.

Moreover, according to the said boiling test, as shown in FIG. 7, the time until the contents accommodated in the pan P boil, that is, the total amount of heat applied to the pan P to boil the water (specified heating amount Q ₀ ) and the difference between the contents and the temperature of the bottom plate B of the pan P (ΔT _p0 ), that is, the degree of superheat (ΔT _P0 ) of the bottom plate B with respect to the specified heating amount (Q ₀ ). At this time, the degree of superheat (ΔT _P ) of the bottom plate B with respect to an arbitrary heating amount (Q) applied to the pan P can be estimated by the following equation.

Here, the index (n) is a value of 0.5 to 0.9, preferably a value of 0.6 to 0.8, and can be determined in advance by a boiling test.
Therefore, the predetermined heating amount (Q ₀ ), the degree of superheat (ΔT _P0 ) of the bottom plate B, and the index (n), which are parameters in the above equation (4), are stored in advance in a memory (not shown), thereby allowing an arbitrary heating amount. The temperature (ΔT _P ) of the bottom plate B when (Q) is added can be estimated from the above equation (4). Thus, the temperature of the food F may be transmitted to the user instead of the temperature of the bottom plate B of the pan P.

Furthermore, in the above boiling test, the temperature of the pan P is estimated by assuming an arbitrary gap larger than the actual one, rather than estimating the interval (δ _a ) between the bottom plate B and the top plate 3 of the pan P. 7, when the estimated temperature starts to decrease (overshoot), it can be determined that the contents stored in the pan P have started to boil. Due to the decrease in the estimated temperature, the start of boiling can be estimated and can be used as a criterion for various controls.
Further, that the time rate of change of temperature (T _g) of the top plate 3 (∂T g _/ ∂t) showed a maximum value may be estimated based on the start of boiling. In addition, since the accuracy of the time change rate (∂T _g / ∂t) is important, it is preferable to perform an averaging process. In particular, the temperature of the top plate 3 (T _g) are averaged by calculating the time rate of change (∂T g _/ ∂t), it is possible to improve the prediction accuracy.

Embodiment 3 FIG.
The third embodiment of the induction heating cooker according to the present invention will be described in detail below with reference to FIG. The induction heating cooker 1 according to the second embodiment measures the interval (δ _a ) for each pan P by a boiling test, but the induction heating cooker 1 according to the third embodiment uses the interval (δ _Since it has the same configuration as the electromagnetic cooker 1 of Embodiment 1 except that a displacement sensor 90 for measuring _a ) is separately provided below the top plate 3, the description of the overlapping points is omitted.

FIG. 8 is a circuit block diagram of the induction heating cooker 1 according to the third embodiment of the present invention. As shown in the figure, the induction heating cooker 1 according to the third embodiment has a displacement sensor 90 that measures _a distance (δ _a ) between the bottom plate B of the pan P and the top plate 3 below the top plate 3. The measured interval signal is input to the temperature estimation circuit 40. That is, according to the induction heating cooker 1 of the third embodiment, the interval (δ _a ) is directly measured using the displacement sensor 90 before or during cooking, and the temperature of the pan P is accurately estimated. Can do. Therefore, unlike Embodiment 2, it is not necessary to perform a boiling test in advance, and for all pans P whose distance (δ _a ) from the top plate 3 is unknown, the pan using the above equation (3) The temperature of P can be estimated precisely.

As the displacement sensor 90 according to the present invention, any sensor can be adopted as long as the distance (δ _a ) between the pan P and the top plate 3 can be estimated. For example, eddy current type, confocal measurement The displacement sensor 90 may be a method, a triangulation method, an autocollimation method, a laser non-contact method, an ultrasonic method, or a capacitance method. A displacement sensor according to each of these methods will be schematically described below.

The eddy current type displacement sensor generates a high-frequency magnetic field by passing a high-frequency current through a coil inside the sensor head, and when there is an object (pan P) in this magnetic field, the surface of the object is perpendicular to the passage of the magnetic field. Directional eddy current flows, and energy loss due to the eddy current changes depending on the distance to the object, and a change in the transmission state due to the eddy current loss is detected to estimate the distance.

According to the confocal measurement type displacement sensor, the laser light passes through the objective lens that moves up and down at high speed by the tuning fork, focuses on the object, and the reflected light is condensed at one point at the position of the pinhole, and the light receiving element The distance can be estimated by measuring the position of the objective lens at that moment with a sensor.

The displacement sensor of the triangulation system diffuses and reflects the projected laser light on the surface of the object, condenses a part of the reflected light with a light receiving lens and forms an image on the CCD, and the object is displaced. Then, the angle at which the diffusely reflected light is collected changes and the imaging position on the CCD moves, but the distance is estimated by detecting the imaging position.

In an autocollimation type displacement sensor, parallel laser light that has been irradiated from a laser light emitting element and then converted in parallel by a collimator lens is reflected by an object, collected by a light receiving lens, and located on the focal length of the lens. An image is formed on a CCD element. Since the image formation position at this time changes depending on the irradiation laser beam and the angle of the object, the image formation position on the CCD also changes when the inclination of the object changes. The distance can be estimated by converting the amount of change into an angle.

In the laser non-contact type displacement sensor, the light in the wide wavelength band emitted from the laser light source is partially reflected by the reference surface inside the head, and the transmitted light is regularly reflected by the object and returned to the head. At this time, the two reflected lights interfere with each other, and the intensity of the interference light of each wavelength is determined by the distance between the reference surface and the object, and becomes maximum when the wavelength is an integral multiple of the wavelength. By separating the interference light for each wavelength with a spectroscope, the light intensity distribution of the wavelength is obtained, and the distance can be estimated by analyzing the waveform.

The ultrasonic displacement sensor transmits ultrasonic waves from the sensor head, receives the ultrasonic waves reflected by the object again with the sensor head, and measures the time from transmission to reception of the sound waves to estimate the distance. Is.

The capacitance type displacement sensor estimates the distance using the change in the capacitance because the capacitance changes with the reciprocal of the distance when an electric field is applied to the object.

Among the displacement sensors, it is preferable to employ a non-optical displacement sensor that is not affected by dirt or liquid spillage on the top plate 3.
Moreover, in the induction heating cooker 1, since the heating coil 20 equivalent to an eddy current sensor or a capacitance sensor is mounted, the heating coil 20 may be used as these displacement sensors. Further, one heating coil 20 of the multiple arranged heating coils 20 may be used so that the displacement sensor 90 and the heating coil 20 are combined.

In order to improve temperature detection accuracy, the temperature sensor 30 is preferably disposed at a position where the distance (δ _a ) is measured by the displacement sensor 90, that is, close to the displacement sensor 90.
In addition, depending on the mounting position with respect to the heating coil 20 and the like, the pan P is formed with a region where the food (especially moisture) is likely to boil (a boiling region) and a region where the boiling is difficult (a non-boiling region). Since more vaporization heat is taken away from the non-boiling region and the temperature becomes low, the temperature distribution may vary in the entire bottom plate B of the pan P. Therefore, it is preferable to provide a large number (a plurality) of temperature sensors 30 at a plurality of positions facing the heating coil 20.

Furthermore, it is preferable that the displacement sensor and the temperature sensor 30 are provided inside the inner diameter of the heating coil 20. Although the pan P generally used has various sizes (diameters), the displacement sensor and the temperature sensor 30 preferably have a radius from the center of the heating coil 20 in order to accurately detect the temperature even in the small-diameter pan P. It arrange | positions within 60 mm, and arrange | positions in the approximate center of the heating coil 20 more suitably.

Alternatively, the displacement sensor 90 may be arranged outside the IH heating unit 4 (and the radiant heating unit 5) as shown in FIG. 9 instead of being provided inside the inner diameter of the heating coil 20.
The induction heating cooker 1 has a displacement detection region 92 for measuring the interval (δ _a ) between the pan P and the top plate 3, and the displacement sensor 90 is substantially at the center of the displacement detection region 92. It is disposed below the top plate 3. The user places the pan P in the displacement detection region 92 before cooking and heating using the pan P, and automatically measures the interval (δ _a ) by pressing a measurement switch (not shown). The interval (δ _a ) is stored in the memory of the temperature estimation circuit 40 or the control circuit 50. Thereafter, the user moves the pan P onto the IH heating unit 4 to start cooking and heating, and the induction heating cooker 1 estimates the temperature of the pan P using the interval (δ _a ) stored in the memory. .

As described above, since the displacement sensor 90 is disposed below the displacement detection region 92 that is maintained at a relatively low temperature, a displacement sensor having a lower heat resistance temperature (lower cost) can be used. Further, even in the induction heating cooker 1 having a plurality of IH heating units 4, the single displacement sensor 90 can be shared, the space in the housing 2 can be effectively used, and the heating coil 20 can be located inside. Complicated circuit wiring can be avoided as compared with the case where it is provided.
In this case, in order to make it easier for the user to place the pan P in the displacement detection area 92, it is preferable to display a marking such as a graphic indicating the displacement detection area 92 on the top plate 3.

On the other hand, the temperature sensor 30 and the displacement sensor 90 are exposed to a strong magnetic field and a high temperature atmosphere by the heating coil 20 especially when provided inside the inner diameter of the heating coil 20, so that as shown in FIG. Alternatively, it is preferable to protect from a strong magnetic field and a high temperature atmosphere by surrounding it with a magnetic shield pipe 94). The temperature sensor 30 and the displacement sensor 90 may be housed in separate protective tubes 94, but may be protected by a single protective tube 94 when arranged adjacent to each other. The protective tube 94 is for suppressing the high-frequency magnetic field from the heating coil 20 and protecting the temperature sensor 30 and the displacement sensor 90. Therefore, the protective tube 94 is made of copper, aluminum, ferrite, or the like that has a magnetic shielding effect and is difficult to be induction-heated. It is preferable that it is a cylindrical tube formed by the following.
The protective tube 94 is preferably a seamless copper tube, and its thickness is 0.8 mm or more, more preferably 1.0 mm or more. Further, since the protective tube 94 is exposed to a high temperature by a strong magnetic field or radiant heat from the heating coil 20, it is preferable to provide a gap between the temperature sensor 30 and the mutation sensor 90. For example, it is preferable that the inner surface of the protective tube 94 is brought into contact with the sensor via a spacer or a rib so that the contact area is made as small as possible.

Moreover, the wiring which transmits a signal from the temperature sensor 30 and the displacement sensor 90 to the temperature estimation circuit 40 employs a twisted line or a covered wiring, or is wound around a ferrite rod a plurality of times, thereby causing noise caused by a high-frequency magnetic field. It is preferable to estimate the temperature of the pan P based on the temperature (T _g ) and the interval (δ _a ) of the top plate 3 more accurately measured while suppressing (disturbance).

Furthermore, the contact-type temperature sensor 30 such as a thermistor usually has a high heat transfer structure (for example, aluminum) that contacts the top plate 3 with as wide a contact area as possible in order to reduce the contact thermal resistance with the top plate 3 as much as possible. However, in place of the high heat transfer structure, it is preferably embedded in a material (for example, ceramic, resin, etc.) that is not induction heated by a high frequency magnetic field. Thereby, it can prevent that the temperature sensor 30 becomes high temperature, and can measure the temperature ( _Tg ) of the top plate 3 more correctly.

Here, an example in which the thermistor 100 is used as the temperature sensor 30 is shown in FIG. 11A is a side sectional view of the thermistor 100 and its peripheral portion, FIG. 11B is a sectional view taken along the line BB in FIG. 11A, and FIG. The CC sectional view in a) is shown. As shown in FIG. 11A, the thermistor 100 is housed in a high heat transfer structure 101, and the high heat transfer structure 101 is attached to the coil base using a resin folder 102. Further, the folder 102 has a folder cage 102a, and a spring 103 for biasing the folder cage 102a upward is provided in order to press the high heat transfer structure 101 against the top plate 3. According to one aspect of the present invention, the protective tube 94 having an inner diameter larger than the outer diameter of the folder 102 is provided. It is preferable to provide an insulator 104 (for example, a mica plate) in order to insulate between the protective tube 94 and the high heat transfer structure 101, as shown in FIGS. 11B and 11C. It is preferable to provide a plurality of ribs 105 on the folder outer wall 102b and the folder basket 102a to provide a gap between the protective tube 94 and the folder 102 and to reduce the contact area between the protective tube 94 and the folder 102.

Further, the temperature sensor 30 is heated by radiant heat from the heating coil 20 particularly when it is disposed close to the heating coil 20. Therefore, in addition to or instead of the protective tube 94, a heat insulating material (not shown) for blocking heat transfer from the heating coil 20 may be provided around the temperature sensor 30. In this case, a gap may be provided between the temperature sensor 30 and the heat insulating material, and cooling may be performed by flowing air (wind) through the gap.

According to the induction heating cooker 1 according to the present invention, based on the surface temperature of the pan P accurately and accurately estimated by the temperature estimation circuit 40, the control circuit 50 can perform various abnormal modes (ignition, oil smoke, bumping). , Spilling, emptying, scorching, etc.) can be detected, and the drive circuit 60 can be emergency stopped or reduced in thermal power (including stepwise reduction), thus improving safety during cooking.

For example, when fried food is cooked, the oil ignites when the temperature of the pan P exceeds a predetermined temperature. In particular, when the amount of oil is small, the temperature rises easily and ignition is likely. Therefore, when the time change rate (∂T _g / ∂t) of the temperature (T _g ) of the top plate 3 obtained by the temperature estimation circuit 40 at this time exceeds a predetermined positive threshold, the control circuit 50 Therefore, the drive circuit 60 is stopped in an emergency.

Further, when spilling occurs, the temperature of the top plate 3 rapidly decreases. Similarly, when the time change rate (時間 T _g / ∂t) obtained by the temperature estimation circuit 40 exceeds a predetermined negative threshold, the control circuit 50 determines that there is a spill and the heating coil The drive circuit 60 is controlled so as to suppress the high-frequency current supplied to 20.

When further scorching occurs, a film made of the carbide of the food material F is formed on the bottom plate B of the pan P, heat is hardly transmitted to the food material F, and the temperature of the pan P gradually increases. When the estimated temperature of the pan P becomes higher than a predetermined temperature, or when the temperature continues to rise, the control circuit 50 stops or suppresses power feeding to the heating coil 20.

Moreover, according to the induction heating cooker 1 according to the present invention, when the abnormal mode is detected, the warning device 80 can be used to give a warning to the user. This is particularly useful when the user leaves the induction heating cooker 1.

For example, when the above abnormal mode is detected, the control circuit 50 controls various warning devices 80, emits a beep, outputs a synthesized voice, lights or flashes a warning lamp, or displays a warning on the liquid crystal display unit 9. Can be made. Thereby, when the abnormal mode is detected, the control circuit 50 promptly notifies the user to call attention and stop or suppress the power supply to the heating coil 20 to realize higher safety. Can do.

Furthermore, according to the induction heating cooker 1 according to the present invention, the control circuit compares the temperature of the pan P set by the heating power adjustment dial 8 or the like with the temperature of the pan P precisely estimated by the above equation (3). In addition, the drive circuit 60 can be controlled so as to heat with an optimum heating power. Moreover, since the actual temperature can be displayed in real time on the liquid crystal display unit 9 instead of the temperature of the pan P set as in the prior art, the heating power adjustment according to the cooking method desired by the user is realized. And it can help you complete delicious dishes more easily.

For example, if you want to cook thoroughly in deep-fried food cooking, set it to 160 ° C. If you want to fry the surface, adjust it to 200 ° C. If you want to heat milk or tea, boil it once and bring it to a boil. Adjust to 90 ° C. At the time of cooking in the town, adjust the temperature so that the cooking ingredients are maintained at 60 ° C., and adjust the temperature so that it does not boil when miso soup is heated. In this way, the user can set a temperature suitable for each cooking method, and there is no need to adjust the heating power depending on the conventional user's sense, and delicious cooking can be performed. In the past, the heating power had to be adjusted based on the content of the food F contained in the pan P. However, since the temperature of the pan P can be estimated accurately and the heating power can be adjusted based on this, It is not necessary to adjust the heating power according to the content, and cooking can be performed more easily.

In addition, when cooking eggs, fried eggs, hamburgers, crepes, dumplings, etc., when the ingredients are put into the pre-heated frying pan P, the temperature of the frying pan P is set in advance to prevent emptying that reaches an abnormal temperature. The frying pan P can be maintained at an appropriate and safe preheating temperature.

Furthermore, the temperature of the pan P can be accurately estimated even when cooking a stewed dish such as oden, or when heated and kept at a low temperature such as hot salmon or milk, so that it can be reliably set to a desired temperature.

At the beginning of heating, when the food F is not boiling (non-boiling state), the temperature increase rate (dT / dt) of the pan P and the food F is determined by the following equation using the heat capacity C and the input heating amount Q: It is represented by

Therefore, by providing a circuit for estimating the heat capacities of the pot P and the food F based on the estimated rate of time change (dT / dt) of the temperature of the pot P and the input electric power, the time until the boiling state is reached is provided. The user can estimate and display, and the user can know the timing of putting the food F into the pan P and the cooking completion time, and can efficiently cook. Also, the cooking time can be controlled and shortened by optimal heating control.

The induction heating cooker 1 is provided with a menu selection device (not shown) that allows a specific menu such as rice cooking to be selected, and controls a cooking program in which cooking time and heating power are set for the selected menu. You may memorize | store in 50 built-in memories, and control a cooking time and a thermal power automatically according to this cooking program ("automatic cooking" is performed).

Furthermore, the induction heating cooker 1 may have an additional memory slot (both not shown) in which an external memory is detachable, and may perform “automatic cooking” according to a cooking program stored in the external memory. In this case, the cooking program stored in the external memory can be freely changed or updated from a PC or an appropriate electronic storage medium, and the latest cooking method, professional cooking method, and cooking method of your choice can be easily done. Can be reproduced.

If necessary, by providing a synthesized voice output device or a video display device (both not shown), the user can perform actual cooking while receiving instructions on the cooking method and procedure guidance of the cooking program stored in advance. You can also enjoy it. Similarly, the user can use these devices to cook while listening to favorite music during cooking.

Note that the degree of superheat due to boiling heat transfer (temperature difference between the heat transfer wall and the boiling point of water) is related by heat flux (transfer heat per unit area). That is, the temperature of the pan P at any thermal power (the temperature obtained by adding the superheat degree to the boiling point of water) is known, and the temperature of the pan P described above is determined by considering the superheat degree associated with the thermal power. The temperature of the food F accommodated in the pan P can be set, and the temperature of the pan P described above can be displayed, set and controlled as the temperature of the food F.

In addition, regarding the temperature estimation method described above, a correction term may be considered in the estimated value. The correction term, the cooling section by the air supply (e.g., the function f _(T g, T _air), where T _air temperature of the cooling air), radiant section from the induction heating coil (for example, the function f _(T g, T _c ), where T _c is the temperature of the induction heating coil), contact thermal resistance between the temperature sensor and the top plate (for example, function f (T _g , Q)), and the like. Therefore, it is preferable to have means for measuring the temperature of the cooling _air (T _air ) and the temperature of the induction heating coil (T _c ).

Claims (14)

1. A top plate on which the object to be heated is placed at _a predetermined interval (δ _a );
   A heating coil disposed under the top plate for induction heating the object to be heated;
   A drive circuit for supplying a high-frequency current to the heating coil;
   A temperature sensor disposed below the top plate for detecting the temperature (T _g ) of the top plate;
   A time change rate (∂T _g / ∂t) of the temperature (T _g ) of the top plate detected by the temperature sensor is calculated, and the interval (δ _a ) and the time change rate (∂T _g / ∂) are calculated. a temperature estimation circuit for estimating a surface temperature (T _p ) of the heated object based on t);
   An induction heating cooker comprising: a control unit that controls the drive circuit using the estimated temperature (T _p ) estimated by the temperature estimation circuit.
2. The induction heating cooker according to claim 1, wherein the temperature estimation circuit estimates a surface temperature (T _p ) of the object to be heated by the following equation.
   

   

   T _p : heated object estimated temperature estimated by the temperature estimation circuit T _g : temperature of the top plate detected by the temperature sensor δ _a : distance between the heated object and the top plate ρ _g : top plate density c _g : Specific heat of the top plate δ _g : Top plate thickness λ _a : Thermal conductivity of air
3. The temperature estimation circuit determines the interval when the estimated temperature (T _p ) of the heated object estimated when the heated object containing water converges to a predetermined value in the shortest time, and the heated object and the top plate The induction heating cooker according to claim 1, wherein the interval is estimated as an interval (δ _a ).
4. The induction heating cooker according to claim 3, wherein the temperature estimation circuit includes storage means for storing the estimated interval (δ _a ) in association with the object to be heated.
5. The induction heating cooker according to any one of claims 1 to 4, wherein a protective tube for suppressing a high-frequency magnetic field from the heating coil is disposed around the temperature sensor.
6. The induction heating cooker according to any one of claims 1 to 5, wherein a heat insulating member is disposed around the temperature sensor.
7. The induction heating cooker according to any one of claims 1 to 6, further comprising interval maintaining means for maintaining a constant interval between the object to be heated and the top plate.
8. The induction heating cooker according to claim 1 or 2, further comprising a displacement sensor that is disposed below the top plate and that measures _a distance (δ _a ) between the object to be heated and the top plate.
9. The induction heating cooker according to claim 8, wherein the displacement sensor is disposed within a radius of 60 mm from the center of the heating coil.
10. 10. The induction heating cooker according to claim 8 or 9, wherein the displacement sensor is arranged in a displacement detection region below the top plate and in which no heating coil is arranged.
11. The induction heating cooker according to claim 5, wherein the protective tube is made of copper and has a thickness of 0.8 mm or more.
12. An arbitrary interval (δ _a ) is assumed, and it is determined that boiling has occurred after the temperature (T _p ) estimated using the above equation (6) shows a maximum value, and predetermined control is performed. The induction heating cooker according to claim 2.
13. Heating an object to be heated disposed at _a predetermined interval (δ _a ) with respect to the insulating plate;
    Detecting a temperature (T _g ) of the insulating plate using a temperature sensor facing the object to be heated via the insulating plate;
    Calculating a rate of time change (∂T _g / ∂t) of the temperature (T _g ) of the insulating plate detected by the temperature sensor;
    Estimating the surface temperature (T _p ) of the object to be heated based on the interval (δ _a ) and the time rate of change of temperature (∂T _g / ∂t);
    And a step of controlling heating of the object to be heated using the estimated temperature (T _p ) estimated by the temperature estimation circuit.
14. The heating control method according to claim 11, further comprising a step of estimating a surface temperature (T _p ) of the object to be heated by the following equation.
    

    

    T _p : Estimated temperature of heated body T _g : Temperature of insulating plate detected by temperature sensor δ _a : Distance between heated body and insulating plate ρ _g : Density of insulating plate c _g : Specific heat of insulating plate δ _g : thickness of insulating plate λ _a : thermal conductivity of air

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