JP2008159494A - Induction cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an induction cooker in which time until starting induction heating is shortened, and in which small articles, positional deviation of a pan, warpage of the pan bottom, boiling, and boiling over or the like are accurately detected, to carry out controls, such as heating stoppage and outputting alerts. <P>SOLUTION: Electrodes 3 are dispersed to the center part of a heating coil 2, between spirals of neighboring heating coils 2, and outside the heating coil, and is disposed under a top plate 8. In a control circuit 6, if the number of the electrodes is larger than a prescribed number, when the combined value of electrostatic capacitance between the electrodes 3 and the prescribed potential or the pan 9, which is measured by an electrostatic capacitance measuring circuit 7, is equal to or larger than the prescribed value; a determination that the pan 9 has been loaded on the cooker is made and a drive circuit 5 is controlled so as to drive the heating coil 2; and this is smaller than the prescribed number, the determination is made that a small article has been loaded on the cooker, and the driving circuit 5 is prohibited from being driven. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an induction heating cooker, and more particularly, to an induction heating cooker that detects warping of the bottom of the cooking device, spilling, boiling, and the like.

An induction heating cooker converts an AC power source into a DC power source using a rectifier circuit, supplies the DC power source to an inverter circuit, converts it into a high-frequency AC current, and flows the high-frequency AC current through the induction heating coil. To generate an alternating magnetic field. This alternating magnetic field causes an eddy current to be generated at the bottom of a metal cooking utensil made of a magnetic material such as a pan placed close to the heating coil via the top plate, and the generated eddy current and the resistance of the metal cooking utensil are generated. Cooking is performed using the heat generated by.
By the way, as the first prior art of the induction heating cooker, the ON period of the switching element in the inverter is shortened at the start of the inverter oscillation, and this ON period is gradually increased so that the input rises rapidly at the start of the oscillation. After performing a soft start that eliminates the startup sound generated by, the input power to the inverter is detected, and load determination based on this input power is performed more accurately and safely than conventional methods, such as small loads such as knives and forks, or A method of stopping the drive of the inverter when there is no load is disclosed (for example, see Patent Document 1).

Further, as a second conventional technique, a method is disclosed in which heating is performed at a constant power at the start of heating, and the amount of warpage of the pan bottom is determined based on a second-order differential value (acceleration) depending on the time of temperature sensor output at that time ( For example, see Patent Document 2).
In addition, as a third conventional technique, a method for determining boiling, spilling, and pan deviation based on a temperature detected by a temperature sensor is disclosed. That is, when a continuous time in which the temperature detected by the temperature sensor is within a predetermined value has reached a predetermined time, it is determined that the temperature is boiling, and the increasing gradient of the temperature detected by the temperature sensor is constant, for a predetermined time. If the temperature gradient suddenly increases after the lapse of time and the temperature becomes constant thereafter, it is determined that there is a spill, and if the temperature gradient increases suddenly and then decreases rapidly immediately after that, it is determined that the pan is slipping. (For example, refer to Patent Document 3).
In addition, as a fourth conventional technique, a method for detecting boiling based on a difference in spectral distribution of vibrations generated when water in a pot boils is disclosed (for example, see Patent Document 4).

JP-A-60-198082 (FIGS. 1 and 3, page 3, lower left column, line 18 to page 5, upper right column, second line) Japanese Unexamined Patent Publication No. 2001-351717 (FIG. 2, paragraphs 0026 to 0028) JP 2006-278099 A (FIG. 2, paragraph 0027) JP-A-61-233988 (FIG. 2, page 2, lower right column, line 2 to page 3, upper left column, line 4)

In the conventional example shown in Patent Document 1, since load determination is performed by soft start, there is a problem that the determination takes time and induction heating cannot be started instantaneously.
Further, in the conventional example shown in Patent Document 2, since the amount of warpage of the pan bottom is determined by a change in the temperature sensor, heating is performed with a reduced power so that the temperature does not overshoot until the determination is completed. Take it. Further, since the amount of warpage of the pan bottom is estimated from the temporal change (acceleration) of the temperature, there is a problem that it is easy to be influenced by the surrounding temperature environment and the accurate amount of warpage of the pan bottom cannot be determined.
In addition, as a conventional technique, when there is no object for detecting the pan placement position, the magnetic field generated by the heating coil does not intersect the pan when the pan is placed at a position shifted from the heating coil. There was a problem that efficiency decreased.
Moreover, in the conventional example shown in Patent Document 3, since the spillage is detected by the temperature gradient, there is a problem that the detection takes time and the spillage amount increases.
Further, in the conventional example shown in Patent Document 4, since the vibration frequency varies depending on the natural frequency of the pan, there is a problem that a wide detection frequency is required and there are many malfunctions.

  The present invention has been made to solve the above-described problems. It shortens the time until the start of induction heating and accurately detects small items, pan misalignment, pan bottom warp, boiling, spilling, etc. The purpose is to obtain an induction heating cooker that controls heating stop and alarm output.

  An induction heating device according to the present invention includes a top plate on which a pan is placed, a heating coil provided under the top plate, a drive circuit that converts an alternating voltage into a high frequency voltage and flows a high frequency current through the heating coil, and An electrode provided under the top plate, a capacitance measuring means for measuring a capacitance between the electrode and a predetermined potential, and a control circuit for controlling the drive circuit based on a measurement result of the capacitance measuring means; , With.

  According to the present invention, the load determination is performed based on the capacitance between the electrode arranged in the vicinity of the heating coil and the predetermined potential, and the drive circuit is controlled. While shortening, it is possible to accurately detect small items, pan misalignment, pan bottom warp, boiling, spilling, etc., and control heating stop and alarm output.

Embodiment 1 FIG.
FIG. 1 is an explanatory diagram showing a schematic configuration of an induction heating apparatus according to Embodiment 1 of the present invention. In the figure, an induction heating apparatus 1 includes a heating coil 2, an electrode 3 installed between the heating coil central portion and the heating coil, and an outer periphery of the heating coil, and an AC voltage of an AC power source 4 converted into a high-frequency voltage. A drive circuit 5 for driving the drive circuit, a control circuit 6 for controlling the drive circuit 4, and a capacitance measurement circuit 7 (capacitance) for measuring the capacitance between the electrode 3 and the top plate mounting object. Measuring means).

  FIG. 2 is a side view of the heating coil portion of FIG. In FIG. 2, a pan 9 is placed on the top plate 8 as a cooking utensil, and a plurality of electrodes 3 are placed under the top plate 8 between the vortices of the heating coil. Next, Embodiment 1 of the present invention will be described with reference to FIG. 1 and FIG. The capacitance measuring circuit 7 measures a capacitance (parasitic capacitance) between the electrode 3 and a predetermined potential, for example, a ground potential (hereinafter also referred to as GND).

Moreover, FIG. 3 is a figure which shows the relationship between the distance and the area between the electrode 3 and GND or a pan in Embodiment 1 of this invention.
FIG. 4 is a graph showing the relationship between the plurality of electrodes 3 and the capacitance detected by each electrode 3 in Embodiment 1 of the present invention. Here, the capacitances of the first to fifth electrodes 3 corresponding to the five electrodes 3 arranged as shown in FIG. 1 are shown.
FIG. 5 is a main part plan view showing the arrangement of the individual electrodes 3 on the top plate in the first embodiment of the present invention.

Next, Embodiment 1 will be described with reference to FIGS.
As shown in FIG. 3, the relative dielectric constant (mainly air) between the electrode 3 of area A and GND is K, the distance is d, and the vacuum dielectric constant is ε0.
When there is no pan, the capacitance C is
C = K × ε0 × A / d
It becomes. When the pan is placed, an electrode having an area nA (n is a real number larger than 1) is sandwiched between the distances d. The capacitance C at this time is C1, where the capacitance between the electrode and the pan is C1.
C1 = K × ε0 × A / d1,
If the capacitance between the pan and the predetermined potential is C2,
C2 = K × ε0 × nA / d2
And
C = C1 × C2 / (C1 + C2) = K × ε0 × A / (d1 + d2 / n)
It becomes. Here, since n> 1, (d1 + d2 / n) <d, and the capacitance C increases when the pan is placed.

  Therefore, in the no-load state, the capacitance between the electrode 3 and GND is small as shown in FIG. 4A, and when the pan 9 is placed, the capacitance becomes large as shown in FIG. 4C. . In addition, when small items such as spoons and forks are placed, only the capacitance between the nearby electrode and GND increases as shown in FIG. The capacity remains. Therefore, by checking the number of electrodes having a large electrostatic capacity, it is possible to determine whether the one placed on the top plate is a pan, a small object, or no load.

  The control circuit 6 receives the capacitance between each electrode 3 measured by the capacitance measuring circuit 7 and the predetermined potential or the pan 9 and compares them relative to each other. Then, by this relative comparison, the number of adjacent electrodes 3 that have detected a capacitance larger than a predetermined value (predetermined value is 120 in the example of FIG. 4) is a predetermined number (for example, in the example of FIG. If the predetermined number is 3 among the first to fifth electrodes 3, it is determined that a pan with a large bottom area is placed, and the drive of the drive circuit 5 is immediately started. To do. For example, in the example of FIG. 4C, since the capacitances of all the first to fifth electrodes 3 are larger than 120, the control circuit 6 determines that a pan having a large bottom area is placed. In this case, since there is no time-consuming soft start process at the start of driving of the drive circuit 5, it is possible to shorten the time until the induction heating is started as compared with the prior art. When a small object such as a spoon or fork is placed on the top plate, the control circuit 6 has a smaller number of electrodes 3 that have detected a high capacitance than a predetermined number (for example, FIG. 4B). In the example, in the case where only the third electrode 3 has a high capacitance among the first to fifth electrodes 3), it is determined that a small object having a small surface area is placed, and the drive circuit 5 Is prohibited.

  In addition, in an induction heating cooker having two heating coils on the left and right, the electrode 3 is arranged so that the electrode 3 on the back side is narrower than the near side. The reason for this arrangement is as follows. Since the person who cooks tends to put an object in a place where the front is wide and the periphery or the back is narrow from the viewpoint of ease of operation, when the electrode is arranged in such a position, the electrode 3 is placed in the front and back as well. The positional deviation of the pan 9 can be detected more accurately than the case where it is arranged.

As described above, according to the first embodiment, the load determination can be performed based on the magnitude of the capacitance. In addition, since a plurality of electrodes are installed and the placement of the pan or small object is determined by relative comparison of the capacitance between each electrode and a predetermined potential, it is possible to detect the pan or small object. Furthermore, since the plurality of electrodes are distributed and arranged in the heating coil central portion, between the heating coils, and in the heating coil diameter direction outside the heating coil, the pan detection or the small object detection can be reliably performed. Moreover, since the control circuit starts induction heating immediately without passing through the soft start when detecting the placement of the pan, the time until the induction heating starts can be shortened. Further, when the control circuit determines that a small object is placed, the operation of the drive circuit is prohibited, so that useless power is not consumed.
In addition, there is a high possibility that the pan is placed on the front side where the operation unit is located or on the inner side or the rear side having a wider space than the left and right edge directions. When the electrodes are arranged so that the electrodes on the back side are narrower than the front side, it is possible to reliably detect even when the electrodes are shifted.

Embodiment 2. FIG.
In this Embodiment 2, the form which measures the amount of curvature of a pan bottom and controls heating is demonstrated.
FIG. 6 is an explanatory diagram showing a schematic configuration of the induction heating apparatus according to Embodiment 2 of the present invention. In the figure, the same reference numerals as those in FIG. The temperature sensor 11 is installed between the vortices of the heating coil under the top plate.
FIG. 7 is a graph showing the relationship between the plurality of electrodes 3 and the capacitance detected by each electrode 3 in Embodiment 2 of the present invention.
Next, Embodiment 2 will be described with reference to FIGS. Description of the same parts as those in the first embodiment will be omitted, and different parts will be described.

  The control circuit 6 controls the drive circuit so that the value of the temperature sensor 11 becomes a predetermined value. The capacitance measuring circuit 7 measures the capacitance between each electrode 3 and the pan 9. As shown in FIG. 6, when the bottom of the pan is warped, for the capacitance between each electrode pan, an air layer with a small relative dielectric constant is formed in the portion where the amount of warp of the pan bottom is large. The capacitance becomes smaller (FIG. 7). Moreover, when there exists an air layer, the detected value of the temperature sensor 11 also shows a value lower than the actual temperature of the pan 9. The control circuit 6 compares the capacitances of the electrodes detected by the capacitance measuring circuit 7 to determine the warp amount of the pan bottom, converts the temperature difference according to the warp amount of the pan bottom, and based on this temperature difference. Then, the detection value of the temperature sensor 11 is corrected to determine the pan temperature. For example, when it is determined that the amount of warpage of the pan bottom converted from the capacitance is 5 mm, the temperature of the pan itself is estimated to be higher than the value of the temperature sensor 11 by a predetermined value A degrees. The sum is determined as the pan temperature and the drive circuit is controlled. In addition, when converting the temperature difference from the amount of warp at the bottom of the pan, it can be calculated using a predetermined mathematical formula, or a correspondence table between the amount of warp at the bottom of the pan and the temperature difference can be created by prior learning. It is also possible to estimate the temperature difference corresponding to the amount of warpage of the pan bottom by using this correspondence table.

  According to the second embodiment, the amount of warpage of the pan bottom is determined based on the detected capacitance, and the pan circuit temperature is corrected based on the amount of warpage of the pan bottom to control the drive circuit, so that the heating time can be shortened. . In addition, since a plurality of electrodes are installed and the amount of warpage of the pan bottom is determined by a relative comparison of capacitance between each electrode and a predetermined potential, accurate determination is possible. Further, since the plurality of electrodes are distributed and arranged in the heating coil diameter direction outside the heating coil, between the heating coil central portion, between the heating coils, and more accurate determination can be performed.

Embodiment 3 FIG.
In the third embodiment, an embodiment provided with alarm means will be described.
FIG. 8 is an explanatory diagram showing a schematic configuration of the induction heating apparatus according to Embodiment 3 of the present invention. In the figure, the same reference numerals as those in FIG. 2 denote the same or corresponding parts, and thus the description thereof will be omitted and different parts will be described. The alarm unit 12 is provided, for example, in the operation unit 10 and is connected to the control circuit 6.
FIG. 9 is a graph showing the relationship between the plurality of electrodes 3 and the capacitance detected by each electrode 3 in Embodiment 3 of the present invention.

Next, Embodiment 3 will be described with reference to FIGS. Description of the same parts as those in the first embodiment will be omitted, and different parts will be described.
When the pan 9 is placed at a position shifted from the heating coil 2, the electrostatic capacitance between each electrode 3 and the pan 9 is biased as shown in FIG. In this case, the control circuit 6 determines that the pan 9 is biased and displays a message to that effect on the alarm means 12 or outputs a voice to alert the user to the pan position. Encourage responses such as corrections.

  In this way, when the pan is placed out of position, the user is notified of the pan misalignment by an alarm, so the user can correct the pan position. When the pan position is corrected by the user, the magnetic field generated from the heating coil crosses the pan, so that an induction heating cooker with good heating efficiency is obtained.

Embodiment 4 FIG.
In this Embodiment 4, the form which drives individually the heating coil divided into 2 inside and outside is demonstrated.
FIG. 10 is an explanatory diagram showing a schematic configuration of the induction heating apparatus according to Embodiment 4 of the present invention. In the same figure, except for the heating coil 2, the same reference numerals as those in FIG. The heating coil is divided into two parts, an inner side 2a and an outer side 2b, and the drive circuit 5 can individually drive the heating coils 2a and 2b.
FIG. 11 is a graph showing the relationship between the plurality of electrodes 3 and the capacitance detected by each electrode 3 in Embodiment 4 of the present invention.

Next, this Embodiment 4 is demonstrated using FIG. 10 and FIG. Description of the same parts as those in the first embodiment will be omitted, and different parts will be described.
When a large pan is placed, the capacitance between all the electrodes and the pan becomes large, so that it can be determined as a large pan. In the case of a small pan, the electrode installed outside does not cover the pan, so the capacitance of the outer electrode remains small. Thereby, a large pot and a small pot can be distinguished.

The control circuit 6 receives the capacitance between each electrode 3 measured by the capacitance measuring circuit 7 and the predetermined potential or the pan 9 and compares them relative to each other. And if all the electrodes 3 detect a high electrostatic capacitance by this relative comparison, it will determine with the large pan | drum having a very large bottom area mounted, and will operate both the inner side heating coil 2a and the outer side heating coil 2b. Thus, the drive of the drive circuit 6 is started immediately.
Further, when the small pan is placed on the top plate 8, even if the outer heating coil 2 b is driven, the magnetic field generated from the outer heating coil 2 b does not intersect with the pan 9 and is wasted. Therefore, as a result of the relative comparison, when a part of the electrodes 3 detects a low capacitance, the control circuit 6 determines that a small pan with a small bottom area is placed, drives only the inner heating coil 2a, and The driving circuit 5 is controlled so as to stop the driving of the heating coil 2b.

  According to the fourth embodiment, as described above, it is possible to identify whether the pan placed on the top plate 8 is a large pan or a small pan. When the pan is used, the driving of the outer heating coil is stopped, so that useless power is used. A highly efficient induction heating cooker can be provided.

Embodiment 5. FIG.
In the fifth embodiment, a mode for detecting a spill will be described.
FIG. 12 is an explanatory diagram showing a schematic configuration of the induction heating apparatus according to Embodiment 5 of the present invention. In the same figure, except for the electrode 3, the same reference numerals as those in FIG. The plurality of electrodes 3 are concentrically arranged on the outer periphery of the heating coil 2.
Moreover, FIG. 13 is a graph showing the time change of the electrostatic capacitance in Embodiment 5 of the present invention.

Next, the fifth embodiment will be described with reference to FIGS. Description of the same parts as those in the first embodiment will be omitted, and different parts will be described.
The plurality of electrodes can be entirely monitored around the pan by being arranged concentrically on the outside of the heating coil. Therefore, no matter which part of the peripheral edge of the pan is spilled, if the capacitance between at least one of the plurality of concentrically arranged electrodes outside the heating coil and the predetermined potential increases, Since the determination is made, it is possible to accurately detect spillage.
When there is no spillage, air with a relative permittivity of 1 is mainly present between the electrode 3 and the pan 9, but when a spill occurs, water with a relative permittivity of 80 enters, so the capacitance increases rapidly. To do. Therefore, it is possible to detect spillage by examining the presence or absence of a sudden increase in capacitance.

The control circuit 6 checks whether or not the capacitance detected by the capacitance measuring circuit 7 constantly or periodically exceeds the reference value. For example, a storage means for storing a predetermined delay time is used as a delay circuit and a comparison circuit. By this storage means, the previous capacitance and the current capacitance are input to the comparison circuit to output a differential voltage, and the differential voltage and the reference voltage configured by dividing the voltage are compared to the comparison circuit. It is determined whether or not the capacitance has increased rapidly depending on whether or not the output is a positive voltage.
Then, when the capacitance increases rapidly, the control circuit 6 determines that a spill has occurred and stops the operation of the drive circuit 5 or controls the drive circuit 5 so as to reduce the current flowing through the heating coil 2. To do. In addition, since spilling usually occurs when the temperature of the pan contents is high, detection of spilling is prohibited for a predetermined time from the start of heating or until the value of the temperature sensor reaches a predetermined value.

  According to the fifth embodiment, since the spillage is immediately recognized and stopped by the change in the capacitance as described above, the spillage amount can be minimized. In addition, since the detection of the spillage is prohibited for a predetermined time from the start of heating at which no spillage occurs or until the value of the temperature sensor reaches the predetermined value, malfunction can be prevented.

Embodiment 6 FIG.
In the sixth embodiment, a mode for detecting boiling will be described.
1 and 3 are also used in the sixth embodiment.
FIG. 14 is a graph showing temporal changes in the differential value of capacitance in Embodiment 6 of the present invention. With the configuration shown in FIG. 1, the differential value at the time of boiling of one electrode is shown. The operation is shown.
Next, the sixth embodiment will be described with reference to FIG.
As shown in FIG. 14, when boiling, the distance d1 between the electrode 3 and the pan 9 shown in FIG. 3 changes due to the vibration of the pan, so that the differential value obtained by differentiating the capacitance with respect to time is greater than or equal to the judgment value. fluctuate. Therefore, it is possible to determine whether or not it is boiling by examining whether or not the differential value of the capacitance is equal to or greater than the determination value.

  The control circuit 6 compares the differential value of the capacitance between the electrode 3 and the pan 9 measured by the capacitance measuring means 7 and the determination value, and determines the differential value of the capacitance (differential value by time). When fluctuations exceeding the value continue for a predetermined time or more, it is determined that boiling has occurred, and the operation of the drive circuit 5 is stopped, or the drive circuit so as to reduce the current flowing through the heating coil 2 5 is controlled.

  According to the sixth embodiment, as described above, since boiling is detected by a change in capacitance generated by a change in the time axis of the distance between the top plate and the pan due to vibration, the influence of the natural frequency of the pan Therefore, malfunction can be prevented. Further, since the boiling detection is prohibited for a predetermined time from the start of heating at which boiling does not occur or until the value of the temperature sensor reaches a predetermined value, malfunction can be prevented.

Embodiment 7 FIG.
In the seventh embodiment, the measurement timing of capacitance will be described.
The capacitance measurement of the capacitance measurement circuit 7 is preferably performed when little or no current flows through the heating coil 2. Accordingly, the capacitance is measured in a stopped state before the current flows through the heating coil 2, or in a stopped state in which the drive circuit is stopped and no current flows through the heating coil, or the AC voltage is measured. The heating coil current near the zero crossing is performed in the part where there is little.

  According to the seventh embodiment, as described above, the drive circuit is stopped or the capacitance is measured in the vicinity of the AC zero cross with a small current, so that erroneous detection due to noise can be prevented.

Embodiment 8 FIG.
In the eighth embodiment, the material of the electrode will be described.
The electrode is preferably made of a nonmagnetic material, and is preferably made of an aluminum material which is a nonmagnetic material.
When an aluminum material is used in this way, since aluminum is a metal having a low resistance and a low relative magnetic permeability, heat generation can be suppressed to a minimum even when receiving a magnetic field generated from a heating coil.

Embodiment 9 FIG.
In the ninth embodiment, when measuring the capacitance, an IC is used in which a high frequency voltage is applied between the electrode 3 and a predetermined potential, and the capacitance is measured based on the attenuation level of the applied voltage.
As a result, when the frequency of the high frequency voltage is f and the capacitance is C, the impedance becomes 1 / 2πfC. As the capacitance increases, the impedance decreases in inverse proportion to the size of the capacitance, and thus the high frequency voltage attenuates. By measuring the amount of attenuation, the capacitance can be easily detected instantaneously.

Embodiment 10 FIG.
Further, the predetermined potential is GND.
Thus, GND is the most stable potential, and measuring the capacitance between the electrode and GND can reduce capacitance measurement errors.

  In the above description, the control circuit 6 is described as a circuit, but it goes without saying that a microcomputer may be used.

It is explanatory drawing which shows schematic structure of the induction heating apparatus in Embodiment 1 of this invention. It is the figure which looked at the heating coil part of FIG. 1 from the side. It is a figure which shows the relationship between the distance and the area between the electrode 3 and GND or a pan in Embodiment 1 of this invention. It is a graph which shows the relationship between the some electrode 3 in Embodiment 1 of this invention, and the electrostatic capacitance detected by each electrode 3. FIG. It is a principal part top view which shows each electrode 3 arrangement | positioning on the top plate in Embodiment 1 of this invention. It is explanatory drawing which shows schematic structure of the induction heating apparatus in Embodiment 2 of this invention. It is a graph which shows the relationship between the electrostatic capacitance detected by the some electrode 3 and each electrode 3 in Embodiment 2 of this invention. It is explanatory drawing which shows schematic structure of the induction heating apparatus in Embodiment 3 of this invention. It is a graph which shows the relationship between the several electrode 3 in Embodiment 3 of this invention, and the electrostatic capacitance detected by each electrode 3. FIG. It is explanatory drawing which shows schematic structure of the induction heating apparatus in Embodiment 4 of this invention. It is a graph which shows the relationship between the electrostatic capacitance detected by the some electrode 3 and each electrode 3 in Embodiment 4 of this invention. It is explanatory drawing which shows schematic structure of the induction heating apparatus in Embodiment 5 of this invention. It is a graph showing the time change of the electrostatic capacitance in Embodiment 5 of this invention. It is a graph showing the time change of the differential value of the electrostatic capacitance in Embodiment 6 of this invention.

Explanation of symbols

1 induction heating device, 2 heating coil, 2a heating coil, 2b heating coil, 3 electrode, 4 AC power supply, 5 drive circuit, 6 control circuit, 7 capacitance measuring circuit, 8 top plate, 9 pan, 10 operation unit, 11 Temperature sensor, 12 Alarm means.

Claims (34)

A top plate on which the pan is placed;
A heating coil provided under the top plate for heating the pan;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
A plurality of electrodes provided under the top plate;
A capacitance measuring means for measuring a capacitance between the electrode and a predetermined potential;
An induction heating cooker comprising: a control circuit that controls the drive circuit based on a measurement result of the capacitance measuring means. A plurality of the electrodes are provided so as to cross the heating coil,
The control circuit determines placement of pots or small items based on the number of electrodes adjacent to each other whose capacitance value measured by the capacitance measuring means is equal to or greater than a predetermined value. The induction heating cooker according to 1.   The control circuit determines that a pan is placed and permits the operation of the driving circuit if the number of the electrodes whose capacitance value is equal to or greater than a predetermined value is equal to or greater than a predetermined value. The induction heating cooker according to claim 2.   The control circuit determines that an accessory is placed and prohibits the operation of the driving circuit if the number of the electrodes whose capacitance value is equal to or greater than a predetermined value is equal to or less than the predetermined value. The induction heating cooker according to claim 2.   2. The induction heating cooker according to claim 1, wherein the control circuit determines placement of a pan or a small object by a relative comparison of capacitance between each electrode and the predetermined potential. The top plate has an operation part at least on the front surface,
One heating coil is provided on each of the left and right sides,
The plurality of electrodes are arranged so as to cross substantially the diameter of each heating coil, and connect a straight line connecting the electrodes arranged in the one heating coil and each electrode arranged in the other heating coil. The induction heating cooker according to any one of claims 2 to 5, wherein a plane formed by a straight line formed by is a surface whose back side is narrower than the front side when viewed from the operation unit.   The induction heating cooker according to claim 6, wherein the electrodes are arranged in a distributed manner at the center of the heating coil, between the heating coils, and outside the heating coil. A top plate on which the pan is placed;
A heating coil provided under the top plate for heating the pan;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
A temperature sensor that indirectly measures the temperature of the pan placed via the top plate;
A control circuit for controlling the drive circuit so that the value of the temperature sensor becomes a predetermined temperature;
A plurality of electrodes provided under the top plate;
A capacitance measuring means for measuring a capacitance between each electrode and a predetermined potential;
And the control circuit estimates the amount of warpage of the pan based on the measurement result of the capacitance measuring means.   The induction heating cooker according to claim 8, wherein the control circuit corrects the output value of the temperature sensor in accordance with the amount of warpage of the pan.   The induction heating according to claim 8 or 9, wherein the control circuit determines whether or not the pan is placed by relative comparison of capacitance between each electrode and the predetermined potential. Cooking device. The top plate has an operation part at least on the front surface,
One heating coil is provided on each of the left and right sides,
The plurality of electrodes are arranged so as to cross substantially the diameter of each heating coil, and connect a straight line connecting the electrodes arranged in the one heating coil and each electrode arranged in the other heating coil. The induction heating cooker according to claim 10, wherein the plane formed by the straight line is a surface whose back side is narrower than the front side when viewed from the operation unit.   The induction heating cooker according to claim 11, wherein the electrodes are distributed and arranged in a central portion of the heating coil, between the heating coils, and outside the heating coil. A top plate on which the pan is placed;
A heating coil provided under the top plate for heating the pan;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
A temperature sensor that indirectly measures the temperature of the pan placed via the top plate;
A control circuit for controlling the drive circuit so that the value of the temperature sensor becomes a predetermined temperature;
A plurality of electrodes provided under the top plate;
A capacitance measuring means for measuring a capacitance between each electrode and a predetermined potential;
And the control circuit determines the position of the pan on the top plate by relative comparison of capacitance between each electrode measured by the capacitance measuring means and a predetermined potential. Cooking cooker. Provide alarm means to inform the outside of the pan mounting state,
The control circuit outputs a message to the alarm means that the pan placement position is not correct when it is determined that the center portion of the pan placement position has shifted from the center portion of the heating coil by a predetermined value or more. The induction heating cooker according to claim 13. The top plate has an operation part at least on the front surface,
One heating coil is provided on each of the left and right sides,
The plurality of electrodes are arranged so as to cross substantially the diameter of each heating coil, and connect a straight line connecting the electrodes arranged in the one heating coil and each electrode arranged in the other heating coil. The induction heating cooker according to claim 13 or 14, wherein a plane constituted by a straight line formed by is a surface whose back side is narrower than the front side when viewed from the operation unit. A top plate on which the pan is placed;
A heating coil provided under the top plate for heating the pan;
A driving circuit for converting an alternating voltage into a high frequency voltage and causing a high frequency current to flow through each of the divided heating coils;
A control circuit for controlling the drive circuit;
A plurality of electrodes disposed in non-contact with the heating coil so as to cross the heating coil;
A capacitance measuring means for measuring a capacitance between each electrode and a predetermined potential;
The induction heating cooker is characterized in that the control circuit determines the size of the pan based on the measurement result of the capacitance measuring means. The heating coil is divided into a plurality of concentric circles,
The induction heating cooker according to claim 16, wherein the control circuit does not drive the divided heating coils outside the determined pot size. A top plate on which the pan is placed;
A heating coil provided under the top plate for heating the pan;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
A temperature sensor for indirectly measuring the temperature of the pan placed through the top plate;
A control circuit for controlling the drive circuit so that the value of the temperature sensor becomes a predetermined temperature;
An electrode provided under the top plate;
A capacitance measuring means for measuring a capacitance between the electrode and a predetermined potential;
And the control circuit determines that spillage has occurred when the capacitance between the electrode and the predetermined potential increases above a predetermined value while driving the heating coil. Cooking device.   The control circuit controls the drive circuit to stop the drive circuit or to reduce a high-frequency current flowing through the thermal coil when it is determined that a spill has occurred. Induction heating cooker.   The induction heating cooker according to claim 18 or 19, wherein a plurality of the plurality of electrodes are concentrically distributed on the outside of the heating coil.   The control circuit determines that the spillage occurs when a capacitance between at least one of a plurality of concentrically arranged electrodes outside the heating coil and a predetermined potential increases. The induction heating cooker described.   The induction heating cooker according to any one of claims 18 to 21, wherein the control circuit prohibits detection of boiling over for a predetermined time from the start of driving of the heating coil. A temperature sensor for indirectly detecting the temperature of the pan placed via the top plate;
The induction heating cooker according to any one of claims 18 to 22, wherein the control circuit prohibits detection of spillage when the temperature detected by the temperature sensor is equal to or lower than a predetermined value. A top plate on which the pan is placed;
A heating coil provided under the top plate for heating the pan;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
A temperature sensor that indirectly measures the temperature of the pan placed via the top plate;
A control circuit for controlling the drive circuit so that the value of the temperature sensor becomes a predetermined temperature;
An electrode provided under the top plate;
A capacitance measuring means for measuring a capacitance between the electrode and a predetermined potential;
The control circuit calculates a differential value of the capacitance measured by the capacitance measuring means, and when the change of the differential value exceeds a predetermined value, the contents of the pan are boiling An induction heating cooker characterized by determining.   When the control circuit determines that the contents of the pan are boiling, the control circuit stops the drive circuit or controls the drive circuit so as to reduce the high-frequency current flowing through the heating coil. The induction heating cooker according to claim 24.   The induction heating cooker according to claim 24 or 25, wherein the control circuit prohibits detection of boiling for a predetermined time from the start of driving of the heating coil. A temperature sensor for indirectly measuring the temperature of the pan placed via the top plate;
27. The induction heating cooker according to any one of claims 24 to 26, wherein the control circuit prohibits the detection of boiling when the temperature measured by the temperature sensor is equal to or lower than a predetermined value.   The induction heating cooker according to any one of claims 1 to 17, wherein the capacitance measuring unit performs capacitance measurement in a stop state before driving the heating coil.   24. The capacitance measurement unit according to any one of claims 1 to 23, wherein the capacitance measurement unit performs capacitance measurement in a stopped state in which the drive circuit is stopped and no current flows through the heating coil. Induction heating cooker.   The induction according to any one of claims 1 to 27, wherein the capacitance measuring means performs capacitance measurement when a current flowing through the heating coil near the zero cross of an AC voltage is small. Cooking cooker.   The induction heating cooker according to any one of claims 1 to 30, wherein the electrode is made of a nonmagnetic material.   32. The induction heating cooker according to claim 31, wherein the nonmagnetic material of the electrode is an aluminum material.   The capacitance measuring means uses an IC that applies a high-frequency voltage between the plurality of electrodes and a predetermined potential, and measures the capacitance of the plurality of electrodes based on an attenuation level of the applied voltage. The induction heating cooker according to any one of claims 1 to 32.   The induction heating cooker according to any one of claims 1 to 33, wherein the predetermined potential is a ground potential.

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