WO2011155220A1

WO2011155220A1 - Induction cooker

Info

Publication number: WO2011155220A1
Application number: PCT/JP2011/003306
Authority: WO
Inventors: 祐史山本; 史太佳小笠原; 高志武平; 正也武部; 雅志木下
Original assignee: パナソニック株式会社
Priority date: 2010-06-10
Filing date: 2011-06-10
Publication date: 2011-12-15
Also published as: JPWO2011155220A1; JP5830665B2

Abstract

Disclosed is a highly reliable induction cooker wherein false detection of boiling over from a cooking container when the cooking container is heated is significantly reduced. The boiling over detecting unit (11) of the induction cooker is so configured as to stop a heating operation or reduce heating power to a third set value (P3), which is smaller than a second set value (P2), in the case where the fluctuation range of a high frequency current detected during a load moving detection period (T4) by a current detecting unit (7), said fluctuation range being stored in a storage unit (12), is smaller than a predetermined value, in a boiling over detecting period after the change quantity of a detected capacitance with respect to a reference value becomes equivalent to or larger than a power reduction threshold value (∆V2).

Description

Induction heating cooker

The present invention relates to an induction heating cooker, and particularly to an induction heating cooker having a function of detecting a spill from a heated container such as a pan during cooking.

In a conventional induction heating cooker, the detection of boiling over is performed by providing a plurality of electrodes on the outer periphery of the heating coil as described in Japanese Patent Application Laid-Open No. 2008-159494 (Patent Document 1). It was done based on the change in capacitance.

FIG. 5 is a diagram showing a configuration of a conventional induction heating cooker described in Patent Document 1. In FIG. FIG. 6 is a graph showing a change in capacitance in an electrode for performing the overflow detection described in Patent Document 1.

As shown in FIG. 5, the conventional induction heating cooker is a drive circuit that inputs low frequency power from an AC power supply 101 and supplies high frequency power to the heating coil 104 in order to induction heat a heating container (not shown). 102. A plurality of small disk-shaped electrodes 103 are concentrically distributed on the outer periphery of the heating coil 104. Each electrode 103 that is distributed is connected to a capacitance measuring circuit 106. A capacitance between each electrode 103 and the capacitance measuring circuit 106 is detected by the capacitance measuring circuit 106. Hereinafter, this capacitance is simply referred to as “the capacitance of each electrode 103”. The capacitance of each electrode 103 depends on the arrangement of a dielectric (for example, a top plate) around each electrode 103 and a conductor (for example, a metal heating container, a heating coil 104, etc.). In the conventional induction heating cooker configured as described above, when liquid is spilled from the peripheral portion of a heating container such as a pan placed on the heating coil 104 via a top plate (top plate), There will be liquid spilled on or near the electrode 103. As described above, the capacitance of any one of the electrodes 103 increases when the liquid spilled is present. By detecting such an increase in capacitance, it is intended to detect a spill. When spilling occurs on or near any of the electrodes 103, moisture is interposed between the electrode 103 and the heating container or the heating coil 104, and the electrostatic capacitance of the heating coil 104 and the electrode 103 rapidly increases. To increase. Therefore, it is possible to detect the spillage by detecting the capacitance of the electrode 103 as described above.

In the conventional induction heating cooker, when it is detected that the capacitance of the electrode 103 has increased rapidly (see FIG. 6), the control circuit 105 determines that the spill is over and stops the operation of the drive circuit 102, or The high-frequency current flowing through the heating coil 104 is reduced.

JP 2008-159494 A

As described above, it is possible to detect the spillage by detecting the electrostatic capacity using the electrodes 103 dispersedly arranged on the outer periphery of the heating coil 104, but the capacitance change of the electrode 103 is spilled. There is a problem that is not a phenomenon that occurs only by itself. For example, even when the user places an object containing moisture such as a wet cloth on the top plate near the electrode 103, the capacitance detected by the electrode 103 changes significantly. Further, even when the user shifts the position of the heating container, the capacitance detected by the electrode 103 changes. Even in such a situation where no spilling occurs, the conventional induction heating cooker determines that spilling occurs and stops the operation of the drive circuit 102 or reduces the current of the heating coil 104, which is difficult for the user. It was an inconvenient cooker.

In the induction heating cooker, a top plate having a smooth surface and no unevenness is provided as a cooking surface, and it is configured so that dirt generated by spilling can be easily wiped off. However, there is a problem that if a large amount of spillage occurs, the top surface of the top plate or the periphery of the induction heating cooker will be severely soiled in a short time if the spillage is left as it is. In addition, even when the spillage is small, if the spillage continues for a long time, there is a problem that the dirt becomes severe as well. Therefore, it is important to notify the user immediately when a spill occurs, or to stop or reduce the heating operation. However, if the spilling is not detected and the heating operation is stopped or reduced, the cooking operation unintended by the user is interrupted. If the frequency of such false detections is high, it is easy to use. Is bad, and it becomes a big problem.

An object of the present invention is to provide an easy-to-use induction heating cooker that can reduce erroneous detection of spillage in a heating container that occurs during heating and that can accurately detect the occurrence of spillage.

An induction heating cooker according to a first aspect of the present invention includes a top plate on which a heating container is placed;
A heating coil that is provided below the top plate and induction-heats the heating container;
An inverter for supplying a high frequency current to the heating coil;
An electrode provided on the back surface of the top plate in the vicinity of the periphery of the heating coil;
A capacitance detector for detecting a capacitance of the electrode by supplying a high frequency signal to the electrode;
A load movement detection unit for detecting a fluctuation range of the magnitude of the magnetic coupling between the heating container and the heating coil in a load movement detection period;
A storage unit that stores a reference value corresponding to the capacitance detected by the capacitance detection unit before a spill occurs;
A control unit that controls the heating output to be a set first set value,
When the amount of change with respect to the reference value in the capacitance detected by the capacitance detection unit is greater than or equal to an output reduction threshold and the fluctuation range of the magnitude of the magnetic coupling is less than a predetermined value, The heating output is reduced to a preset second setting value smaller than the first setting value, or a spillage suppression operation for stopping heating is performed, and the change amount is the output reduction threshold during the load movement detection period. It is comprised so that the time of reaching | attaining may be included. The induction heating cooker according to the first aspect of the present invention configured as described above can greatly reduce the erroneous detection of spillage in the heating container that occurs during heating, and reliably detect the occurrence of spillage. Can do.

In the induction heating cooker of the second aspect according to the present invention, the load movement detection unit in the first aspect includes a heating input / output detection unit that detects input / output of the inverter, and the heating input / output detection The variation width of the magnetic coupling may be detected by detecting the change width of the heating output detected by the part.

In the induction heating cooker according to the third aspect of the present invention, the load movement detection unit according to the first aspect includes an on-time detection unit that monitors an on-time of a switching element constituting the inverter, You may comprise so that the fluctuation range of the said magnetic coupling may be detected by detecting the change width of the said on time which an on time detection part detects.

In the induction heating cooker according to the fourth aspect of the present invention, the overflow detection unit in the first aspect is a second overflow detection period set for a predetermined period when the amount of change is equal to or greater than the output reduction threshold. And when it is detected that the fluctuation range of the magnitude of the magnetic coupling detected by the load movement detection unit is less than a predetermined value, the spill suppression operation is performed after the second spill detection period ends. Also good.

In the induction heating cooker according to the fifth aspect of the present invention, the load movement detection unit according to the first or second aspect is a heating coil current detection unit that measures a high-frequency current supplied to the heating coil. It may be configured.

In the induction heating cooker according to the sixth aspect of the present invention, the load movement detection unit according to the first or second aspect may be an input current detection unit that measures an input current of the inverter. .

In the induction heating cooker according to the seventh aspect of the present invention, the drifting detection unit according to the first aspect includes a reference value update mode and a reference value update stop mode, and shifts to the reference value update mode. The capacitance detected by the capacitance detection unit is stored in the storage unit as the reference value, and the capacitance detected by the capacitance detection unit within the reference value detection period is changed with respect to the reference value. When the amount is less than the reference value update stop threshold smaller than the output reduction threshold, the reference value detection period elapses with the capacitance detected by the capacitance detection unit within the reference value detection period as the reference value. Each time it is updated and stored in the storage unit, the amount of change of the capacitance detected by the capacitance detection unit within the reference value detection period with respect to the reference value is greater than or equal to the reference value update stop threshold. If, it may be configured to shift to the reference value update stopping mode for stopping the updating of the reference value to the storage unit.

In the induction heating cooker according to the eighth aspect of the present invention, the overflow detection unit according to the seventh aspect detects the capacitance of the electrode a plurality of times within a reference value detection period, and the capacitance When the amount of change of the plurality of capacitances detected by the detection unit with respect to the reference value is less than the reference value update stop threshold, an average value of the plurality of capacitances detected within the reference value detection period is newly calculated. The reference value may be updated as a reference value.

In the induction heating cooker according to the ninth aspect of the present invention, when the boiling-out detection unit according to the seventh aspect shifts to the reference value update mode, the capacitance of the electrode within the reference value detection period. And when the change amount of the detected plurality of capacitances with respect to the reference value is equal to or greater than the reference value update stop threshold, the reference value for the storage unit is shifted to the reference value update mode. The update may be stopped.

In the induction heating cooker according to the tenth aspect of the present invention, when the overflow detection unit in the seventh aspect does not determine that the overflow has occurred since the amount of change is equal to or greater than the output reduction threshold, After completion of the reference value update stop mode, the mode may be shifted to the second standby mode, and after waiting for the second standby period, the mode may be shifted to the reference value update mode.

In the induction heating cooker according to the eleventh aspect of the present invention, the boiling-out detection unit according to the seventh aspect shifts to a standby mode after starting heating, and shifts to the reference value update mode after a standby period. It may be configured.

In the induction heating cooker according to a twelfth aspect of the present invention, the overflow detection unit according to the first to eleventh aspects is configured so that the capacitance is not less than the reference value update stop threshold. The maximum value in the capacitance detected by the detection unit may be stored, and if the predetermined value or more is decreased from the maximum value, it may be configured not to determine that the overflow is detected.

According to the present invention, it is possible to provide an easy-to-use induction heating cooker that can reduce erroneous detection of spillage in a heating container that occurs during heating and can accurately detect the occurrence of spillage.

The block diagram which shows the structure of the induction heating cooking appliance of Embodiment 1 which concerns on this invention. The block diagram which shows the structure of the electrostatic capacitance detection part in the induction heating cooking appliance of Embodiment 1. FIG. The top view which shows the various electrodes etc. which were formed in the top plate in the induction heating cooking appliance of Embodiment 1. (A) The figure which shows the electrostatic capacitance detection signal detected in the induction heating cooking appliance of Embodiment 1, and (b) The figure which shows an example of the heating output output from the inverter The figure which shows an example of the ON time of the input current in the load movement detection period, a heating coil current, or a switching element It is a figure which shows the state of the menu display part of the operation part in the induction heating cooking appliance of Embodiment 1, and a display part, and is a figure which shows the setting procedure of the overflow detection operation | movement It is a figure which shows the state of the menu display part of the operation part in the induction heating cooking appliance of Embodiment 1, and a display part, and is a figure which shows the setting procedure of the overflow detection operation | movement It is a figure which shows the state of the menu display part of the operation part in the induction heating cooking appliance of Embodiment 1, and a display part, and is a figure which shows the setting procedure of the overflow detection operation | movement It is a figure which shows the state of the menu display part of the operation part in the induction heating cooking appliance of Embodiment 1, and a display part, and is a figure which shows the setting procedure of the overflow detection operation | movement It is a figure which shows the state of the menu display part of the operation part in the induction heating cooking appliance of Embodiment 1, and a display part, and is a figure which shows the setting procedure of the overflow detection operation | movement Block diagram showing the configuration of a conventional induction heating cooker A graph showing the change in capacitance in detecting boiling over in a conventional induction heating cooker

Hereinafter, specific embodiments according to the induction heating cooker of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the specific configurations described in the following embodiments, and is based on the same technical idea as the technical idea described in the embodiment and the common general technical knowledge in this technical field. Is included.

(Embodiment 1)
FIG. 1A is a block diagram showing the configuration of the induction heating cooker according to the first embodiment of the present invention. 1B is a circuit diagram illustrating a configuration of a capacitance detection unit in the induction heating cooker according to Embodiment 1. FIG. In FIG. 1A, the induction heating cooker according to Embodiment 1 is provided below a top plate (top plate) 2 on which a heating container (for example, an iron pan or the like) 1 is placed, and below the top plate 2. When a current is supplied, the heating coil 3 includes a heating coil 3 that generates a high-frequency magnetic field and induction-heats the bottom surface of the heating container 1 disposed opposite to the heating container 1 and one or more switching elements 4a such as IGBTs. Inverter 4 to be supplied, rectifier 5 that rectifies AC power supply 6 and supplies DC current to inverter 4, current transformer 7 aa that monitors the heating coil current flowing in heating coil 3, and heating corresponding to the heating output of inverter 4 A heating coil current detector 7a that detects a coil current (high-frequency current) and functions as a load movement detector, and a current transformer that monitors the input current of the inverter 4 bb and an output signal of the current transformer 7bb are input to detect an input current (low frequency current) corresponding to the heating output of the inverter 4 and to function as a load movement detection unit, and to turn on the switching element 4a The heating output of the inverter 4 is varied based on the on-time detection unit 7c that monitors time, the heating coil current detection signal output from the heating coil current detection unit 7a, and the input current detection signal output from the input current detection unit 7b. The control unit 8 that controls the drive and the back surface of the top plate 2 (in FIG. 1A, the surface on which the heating container 1 is placed is the front surface, and the opposite surface) is patterned in a band shape with a highly conductive material. A plurality of printed electrodes 9, a capacitance detection unit 10 that detects the capacitance of each electrode 9, a size of the capacitance detected by the capacitance detection unit 10, a predetermined amount A storage unit 12 for storing the magnitude of the heating coil current detected by the heating coil current detection unit 7a detected every period and the magnitude of the input current detected by the input current detection unit 7b every predetermined period; And a spill detector 11 that detects a spill state of the heating container 1 based on a capacitance detection signal and a heating output detection signal (including a heating coil current detection signal or an input current detection signal). . Note that “detecting the capacitance of the electrode” means “the magnitude of the capacitance between the electrode and a predetermined potential (for example, the common potential of the capacitance detection unit 10 or the earth potential) and the capacitance between the electrodes. Is detected. Moreover, in the induction heating cooking appliance of Embodiment 1, the structure and function for detecting the boiling state in the heating container 1 are mainly demonstrated, and the function and structure for detecting other states, for example, heating Description of the state detection function other than the spilled state, such as detection when the container 1 is shifted, floated, burned, and a small object load such as a knife or fork is placed on the top plate 2, is omitted. Also in this block diagram, the configuration other than the configuration necessary for explaining the configuration for detecting the overflowing state is omitted.

FIG. 2 is a plan view of the top plate 2 showing various electrodes formed by pattern-printing a conductive paint on the back surface of the top plate 2 in the induction heating cooker of Embodiment 1 and baking at high temperature. is there. The top plate 2 shown in FIG. 2 is formed of heat resistant glass, for example, crystallized glass. Two

circle patterns

2a and 2b are drawn on the surface of the top plate 2 so that the user can recognize the heating position where the heating container (for example, pan) 1 as the object to be heated is to be placed. For example, the position corresponding to the outer periphery of the heating coil 3 having a maximum output of 3 kW is shown. In the first embodiment, a configuration having two heating coils 3 will be described. However, the number of heating coils 3 is not limited to two, and any number of heating coils 3 such as one, three, and four. A circle pattern and electrodes are formed on at least one heating coil 3 according to the number of the heating coils 3.

As shown in FIG. 2, in the top plate 2 in the induction heating cooker according to the first embodiment, a plurality of operation electrodes 16 serving as operation switches for the user to set the operation of the induction heating cooker are provided on the top plate. 2 is printed in the same manner as the electrodes for detecting spillage. The position where the operation electrode 16 is provided is a region closer to the user side than the

circle patterns

2 a and 2 b on the top plate 2. In the following description, the user side in the top plate 2 is referred to as the near side, and the opposite is referred to as the back side. Further, at the position on the drawing shown in FIG. 2, the position on the top plate 2 is specified as the left side and the right side of the top plate 2.

In the vicinity of the outside of the

circle patterns

2a and 2b, that is, in the vicinity of the periphery of the heating coil 3, an electrode group consisting of a plurality of strip-shaped electrodes 9 (spill detection electrodes 9a to 9g) having a predetermined distance from the

circle patterns

2a and 2b. A and electrode group B are formed. These electrode group A and electrode group B serve as state detection electrodes for detecting a spilled state.

In the vicinity of the outer side of the left circle pattern 2a in the top plate 2 shown in FIG. 2, the left rear electrode 9a having an arc-shaped portion along the annular circle pattern 2a on the back side of the left side, and on the front side of the left side A left front electrode 9b having an arc-shaped portion along the circle pattern 2a and a left center electrode 9c having an arc-shaped portion along the circle pattern 2a are formed on the center side. The left circle pattern 2a is surrounded by the electrode group A including the left rear electrode 9a, the left front electrode 9b, and the left center electrode 9c. That is, the electrode group A has a radius larger than that of the circle pattern 2a, and is arranged at a position concentrically with the circle pattern 2a or in the vicinity thereof. In addition,

connection portions

19a, 19b, and 19c that are wider than the arc-shaped portions are formed at one end of each of the left rear electrode 9a, the left front electrode 9b, and the left center electrode 9c. The

connection portions

19a, 19b, and 19c come into contact with one end of a connection terminal 10a, which will be described later, fixed to the capacitance detection portion 10 (see FIG. 1), whereby the capacitance detection portion 10 and the electrode 9a. , 9b, 9c are electrically connected. Since these

connection portions

19a, 19b, and 19c are provided on the top plate 2, when the top plate 2 is attached to the main body provided with the capacitance detection unit 10, the connection terminal 10a and the

connection portions

19a, 19b, Even if there is a slight shift in the mutual positional relationship of 19c, the connection terminal 10a and the

connection portions

19a, 19b, and 19c can be electrically connected reliably.

Similarly, in the vicinity of the outer side of the right circle pattern 2b, the right rear electrode 9d having an arc-shaped portion along the circular pattern 2b on the right side and the circle pattern 2b on the right front side. A right front electrode 9e having an arc-shaped portion along the circle pattern 2b and a right center electrode 9f having an arc-shaped portion along the circle pattern 2b are formed on the center side. The right circle pattern 2b is surrounded by the electrode group B including the right rear electrode 9d, the right front electrode 9e, and the right center electrode 9f. That is, the electrode group B has a larger radius than the circle pattern 2b, and is arranged at a position on or near the circle pattern 2b. In addition,

connection portions

19d, 19e, and 19f that are wider than the arc-shaped portion are formed at one end of each of the right rear electrode 9d, the right front electrode 9e, and the right center electrode 9f. By providing these

connection portions

19d, 19e, and 19f on the top plate 2, when the top plate 2 is attached to the main body provided with the capacitance detection unit 10, as with the

connection portions

19a, 19b, and 19c, the connection terminals Even if there is a slight deviation in the mutual positional relationship between the terminal 10a and the connecting

portions

19d, 19e, and 19f, the connecting terminal 10a and the connecting

portions

19d, 19e, and 19f can be electrically connected reliably.

A protective electrode 9g is provided at the center of the top plate 2, between the left center electrode 9c and the right center electrode 9f, and a wiring pattern 9aa led out from the left rear electrode 9a to the connecting portion 19a, and the right rear electrode. It is provided in a region between the wiring patterns 9dd led out from 9d to the connecting portion 19d. Further, the protective electrode 9g is led out and arranged in a region parallel to the arrangement of the operation electrodes 16 on the near side of the central portion of the top plate 2. Also in the protective electrode 9g, the connection part 19g is formed in the edge part, and it contacts with the end of the connection terminal 10a of the electrostatic capacitance detection part 10 like other electrodes, and the electrostatic capacitance detection part 10 and It has a function as a connection means for electrical connection.

Moreover, in the induction heating cooker of Embodiment 1, the temperature detection part 17 for detecting the temperature of the heating container 1, and the operation part 18 for a user to set the heating conditions of the said induction heating cooker, etc. Is provided. The temperature signal of the heating container 1 from the temperature detection unit 17 and the setting signal from the operation unit 18 are input to the control unit 8 so as to drive and control the inverter 4 having the switching element 4a. Furthermore, the induction heating cooker according to the first embodiment is provided with a display unit 20 so that the heating conditions set by the user, the operation state of the induction heating cooker, and the like are displayed.

FIG. 1B is a circuit diagram illustrating a configuration of the capacitance detection unit 10 in the induction heating cooker according to the first embodiment. As shown in FIG. 1A, the capacitance detection unit 10 includes a connection terminal 10a whose one end contacts the electrode 9, a high-frequency signal generation unit 13 that supplies a high-frequency signal (for example, 350 kHz) to each electrode 9, and a connection terminal. A capacitor 10b connected between the other end of 10a and the high-frequency signal generator 13 and a connection point between the connection terminal 10a and the terminal of the capacitor 10b are connected to each electrode from the high-frequency signal generator 13 via the capacitor 10. 9 includes a rectifying unit 14 that rectifies a high-frequency current supplied to the power supply 9 and a voltage detection unit 15 that detects a DC voltage rectified in the rectifying unit 14. The connection terminal 10a is formed of an elastic body made of a metal having good conductivity such as phosphor bronze whose contact portion is gold-plated. The connection portions (19a to 19g) of the electrodes 9 (9a to 9g) are supplied with a high-frequency signal from the high-frequency signal generation unit 13 of the capacitance detection unit 10, and the electrodes 9 (9a to 9g). ) Is electrically connected to the rectifying unit 14 in order to detect the capacitance.

In the induction heating cooker according to the first embodiment configured as described above, a pan or the like as the heating container 1 is placed at the position indicated by the

circle patterns

2a and 2b, and the user heats at the operation unit 18. Conditions etc. are set and induction heating operation is started. The control unit 8 drives and controls the inverter 4 so that the heating output becomes the first set value P1 (for example, 3 kW) automatically set by the control unit 8 in the operation unit 18 or the automatic control mode. In the initial heating stage in which the induction heating operation is started, there is no spillage, and there is no leakage between the electrode 9 and the heating container 1, between the electrode 9 and the heating coil 3, and around the electrode 9 and the top plate 2. In the metal frame (not shown) which is provided and grounded, the top plate 2 which is mainly an electrical insulator and air exist. Thereafter, by continuing the induction heating operation, the heated contents in the heating container 1 are brought into a boiling state, and the spillage can be generated. When the spilling occurs, a liquid containing an electrolyte is present around the electrode 9. For example, when the liquid that has touched the bottom of the pan spreads continuously directly above or near the electrode 9, capacitive coupling between the electrode 9 and the pan bottom increases. As a result, since the electrostatic capacitance between the heating coil 3 and the electrode 9 facing the pan bottom increases, the capacitive coupling between the electrode 9 and the heating coil 3 becomes larger than when no spilling occurs. As a result, the capacitance at the electrode 9 increases. If the spilling state continues, the increased state of the capacitance changes according to the amount of spilling and the state of spilling.

As described above, in the induction heating operation, even if the temperature of the contents of the heating container 1 reaches the boiling temperature, it is not necessary to detect the spilling state until the spilling starts, but a certain time has elapsed after the heating is started. Thus, when the contents continue to boil, there is a possibility that spilling may occur, so it is necessary to always detect the spilling state. For this reason, in the induction heating cooker according to the first embodiment, 5 seconds is set as a certain time from the start of heating the contents until the spilling operation starts, and the heating operation is stopped by the spilling detection operation for 5 seconds. Or it is comprised so that the suppression operation of a heating output may not be performed.
In the induction heating cooker according to the first embodiment, the detection of the overflowing state is performed by detecting the capacitance detection signal (Vd) from the capacitance detection unit 10 and the heating coil current detection output from the heating coil current detection unit 7a. This is performed in the overflow detector 11 based on the signal and the input current detection signal output from the input current detector 7b.

FIG. 3A shows a capacitance detection signal (Vd) ((a) of FIG. 3A) detected by the induction heating cooker of Embodiment 1 and a heating output (P) output from the inverter 4 (of FIG. 3A). 3B is a waveform diagram illustrating an example of a capacitance detection signal (Vd) input from the capacitance detection unit 10 to the spillover detection unit 11. 3A, the vertical axis indicates the capacitance detection signal (Vd), and the horizontal axis indicates the elapsed time, and (b) of FIG. 3A shows the capacitance shown in (a) of FIG. The relationship between the detection signal (Vd) and the heating output (P) from the inverter 4 is shown.

As shown in FIG. 1B, the electrode 9 forms a capacitor 10 c with the common potential of the capacitance detection unit 10. The capacitance of the capacitor 10c changes depending on the arrangement of the conductor around the electrode 9. Hereinafter, the capacitance of the capacitor 10c is referred to as “the capacitance of the electrode 9”. In FIG. 1B, the voltage Va of the high-frequency signal generator 13 is divided by a capacitor 10b and a capacitor 10c, rectified by a rectifier 14, and further smoothed by a capacitor 10d to become a DC voltage (Vd '). This DC voltage (Vd ′) is input to the voltage detector 15. The voltage detection unit 15 performs AC-DC conversion on the direct-current voltage (Vd ′) and outputs the converted voltage as a capacitance detection signal (Vd) to the overflow detection unit 11. Thus, the electrostatic capacitance detection part 10 detects the electrostatic capacitance of the electrode 9, and outputs the electrostatic capacitance detection signal (Vd) corresponding to the magnitude | size. In FIG. 3A (a), the capacitance detection signal (Vd) decreases due to the occurrence of spillage from the heating container 1 at the time indicated by point A and the increase in the capacitance of any electrode 9. It shows the case.

[Blowout detection operation]
Hereinafter, the overflow detection operation in the state shown in FIG.
First, in the initial stage of the induction heating operation for heating the heating container 1 (not shown in FIG. 3A (a)), the contents of the heating container 1 are not spilled, and the voltage detection of the capacitance detection unit 10 is performed. The capacitance detection signal (Vd) detected by the unit 15 does not change due to spillage. As described above, in the induction heating cooker according to the first embodiment, a certain standby period (for example, 5 seconds) from the start of the induction heating operation becomes the standby mode, and the heating operation is stopped or the heating output is suppressed by the overflow detection operation. It is configured not to operate. That is, the heating operation is stopped or the heating output is suppressed according to the detection result of the overflow detector 11 only when it is determined that the overflow has occurred after the standby time has elapsed.

When a certain waiting period (for example, 5 seconds) elapses from the start of the induction heating operation and the overflow detection operation is started, the high frequency voltage input from each electrode 9 is rectified by the rectifier 14 and the voltage detector 15. Is input. The DC voltage detected by the voltage detector 15 is digitized and output as a capacitance detection signal (Vd). The capacitance detection signal (Vd) may change even when no spill occurs. For this reason, in the induction heating operation of the induction heating cooker according to the first embodiment, the voltage detection unit 15 elapses for a certain period of time (for example, one cycle of the commercial power supply = 16.7 msec or 20 msec) until the time indicated by the point A. Every time, a capacitance detection signal (Vd) corresponding to the capacitance of each electrode 9 is output to the spill detector 11.

In the wipe detection unit 11, the capacitance detection signal (Vd) is input as it is every predetermined time (for example, every time the zero point of the commercial power source is detected twice). Alternatively, when noise is likely to be superimposed on the capacitance detection signal (Vd), an average value every time a predetermined number of times (for example, 5 or 6 times) is input (for example, about every 0.1 sec). May be input as a capacitance detection signal (Vd). Then, an average value of the capacitance detection signal (Vd) in the reference value detection period (T0) (for example, 1 second) is calculated, and the calculated average value is stored in the storage unit 12 as the reference value (V0). Remember. The reference value (V0) calculated as described above corresponds to the capacitance detected by the capacitance detection unit 10 before spilling occurs. Based on the fluctuation amount (ΔV) of the capacitance detection signal (Vd) with respect to the reference value (V0), the overflow detection unit 11 performs arithmetic processing to determine the presence or absence of the overflow state.

[When the change amount (ΔV) of the capacitance detection signal (Vd) is less than the first change amount (ΔV1)]
In the overflow detector 11, the average value of the capacitance detection signal (Vd) in the reference value detection period (T0) detected at the beginning of the overflow detection operation is registered in the storage unit 12 as the reference value (V0). Note that a preset value may be used for the first reference value (V0). The detected capacitance detection signal (Vd) is compared with the registered reference value (V0) until the reference value detection period (T0) elapses again after the reference value (V0) is registered. The amount of change (ΔV) is detected. If the detected change amount (ΔV) is less than a preset first change amount (reference value update stop threshold: ΔV1), the average of the capacitance detection signal (Vd) in the reference value detection period (T0) A value is obtained and updated and registered in the storage unit 12 as a new reference value (V0). As described above, if the change amount (ΔV) of the capacitance detection signal (Vd) with respect to the reference value (V0) is less than the first change amount (ΔV1) during the elapse of the reference value detection period (T0). In the meantime, the average value of the capacitance detection signal (Vd) is updated and registered as the reference value (V0) instead of the reference value (V0) updated up to the previous time.

Therefore, if the change amount (ΔV) of the capacitance detection signal (Vd) in the reference value detection period (T0) is less than the first change amount (ΔV1), the average of the capacitance reference signal (Vd) during that period The value is updated and registered in the storage unit 12 as a new reference value (V0), and this reference value (V0) is compared with the latest capacitance detection signal (Vd). As described above, the latest reference value (V0) is changed during a period in which the amount of change in the capacitance detection signal (Vd) changes within a small fluctuation range determined in advance within the reference value detection period (T0). The storage unit 12 is sequentially updated and stored. In the overflow detection operation, the above-described reference value update processing is sequentially performed. However, if the amount of change (ΔV) becomes equal to or greater than the reference value (V0), the reference value update processing is stopped as described later. The In the induction heating cooker according to the first embodiment, the first change amount (ΔV1) serving as a threshold value whether or not to update and register as the reference value (V0), that is, the reference value update stop threshold value is, for example, “3 digits”. . Here, “1 digit” is the minimum unit of digital display. In the first embodiment, since the power supply voltage of the microcomputer constituting the voltage detection unit 15 is 5 V, 5V / 8 bits = about 19.5 mV is indicated. Yes.

As described above, in the normal induction heating operation in which no spillage occurs, that is, in the state where the capacitance of the electrode 9 does not change abruptly, the latest capacitance detection signal (Vd) is updated and registered. The reference value (V0) is compared and the amount of change is equal to or less than the first change amount (ΔV1: for example, 3 digits), so that the capacitance detection detected during the reference value detection period (T0) elapses. The average value of the signal (Vd) is updated and registered as the reference value (V0) and recorded in the storage unit 12. As described above, in the induction heating cooker according to the first embodiment, in the normal induction heating operation, the detected capacitance detection signal (Vd) is averaged every reference value detection period (T0), and the latest reference value is obtained. Updated as (V0).

[When the change amount (ΔV) of the capacitance detection signal (Vd) is equal to or greater than the first change amount (ΔV1)]
Next, the operation when the capacitance detection signal (Vd) is changed to a first change amount (reference value update stop threshold: ΔV1) or more in comparison with the reference value (V0) in the spill detector 11. explain.
In the graph of (a) of FIG. 3A, when the change amount (ΔV) of the capacitance detection signal (Vd) with respect to the reference value (V0) exceeds the first change amount (ΔV1) indicated by the point B, the implementation is performed. The induction heating cooker of Form 1 enters the reference value update stop mode, and executes the reference value update stop process for prohibiting the above-described reference value update process. That is, since the detected capacitance detection signal (Vd) is larger than the reference value (V0) by the first change amount (ΔV1), the reference value (V0) that has been updated and registered up to the previous time is updated. Continue to be registered without. In FIG. 3A (a), the reference value (V0) at point A is fixed as the reference value. For this reason, the capacitance detection signal (Vd) is compared with the average value of the capacitance detection signal (Vd) in the latest reference value detection period (T0) registered as the reference value (V0) and changed. A quantity (ΔV) is calculated. Thus, in the reference value update stop mode, the reference value (V0) is fixed, and the change amount (ΔV) of the capacitance detection signal (Vd) with respect to the fixed reference value (V0) is calculated. In the first embodiment, the reference value update stop period is set to about 3 seconds, for example.

Even when the change amount of the capacitance detection signal (Vd) with respect to the reference value (V0) is equal to or greater than the first change amount (ΔV1) and the reference value update stop period (also referred to as the overflow detection period) is started, Next, when the detected capacitance detection signal (Vd) returns below the first change amount (ΔV1) compared to the reference value (V0), the reference value update stop mode is canceled, and then The average value of the capacitance detection signal (Vd) detected thereafter is newly registered as the reference value (V0). Accordingly, when the change amount of the capacitance detection signal (Vd) becomes equal to or greater than the first change amount (ΔV1), the reference value update stop state is entered, but the reference value detection period (T0) (for example, 1 second) If the change amount (ΔV) of the capacitance detection signal (Vd) newly detected during () is less than or equal to the first change amount (ΔV1), the spill detector 11 determines that it is a normal induction heating operation. Thus, the reference value update mode is set and the reference value update process is executed.

[When the change amount (ΔV) of the capacitance detection signal (Vd) is equal to or greater than the second change amount (ΔV2)]
In the induction heating cooker according to the first embodiment, a capacitance detection signal (corresponding to the capacitance of the electrode 9 detected by the capacitance detection unit 20 in the reference value update stop mode (spillover determination period)) ( When the change amount (ΔV) with respect to the reference value (V0) in Vd) becomes equal to or greater than the first change amount (ΔV1), the first overflow detection period (T1) is entered. When the amount of change (ΔV) is further greater than or equal to the second amount of change (output reduction threshold: ΔV2) (the time indicated by point C in FIG. 3A), the first overflow detection period (T1) is Ends and enters the second overflow detection period (T2). In the induction heating cooker according to the first embodiment, the output reduction threshold value that is the second change amount (ΔV2) that is a threshold value indicating whether or not to shift to the second boiling over detection period (T2) is, for example, “14 digits”. . Here, “1 digit” indicates the minimum unit of digital display. It is set to enter the third overflow detection period (T3) after the second overflow detection period has elapsed from when the change amount (ΔV) of the capacitance detection signal (Vd) is equal to or greater than the second change amount (output reduction threshold: ΔV2). ing. The third overflow detection period (T3) is set to 1 second in the induction heating cooker of the first embodiment.

In the induction heating cooker according to the first embodiment, the heating output of the inverter 4 is set by the operation unit 18 or is automatically cooked in the first overflow detection period (T1) and the second overflow detection period (T2). The first set value (P1: 3 kW, for example) automatically set in the mode is set. When the third overflow detection period (T3) is entered, the second set value (P2: smaller than the first set value (P1)) is set. For example, it is reduced (watt down) to 0.3 kW).

In the second overflow detection period (T2), the fluctuation state of the heating coil current (high-frequency current) supplied to the inverter 4 and the input current is used for the overflow detection. As a case where the electrostatic capacitance detection signal (Vd) from the electrostatic capacitance detection unit 10 fluctuates, in addition to the occurrence of spilling, for example, the heating container 1 may be moved and cooked by the user. Thus, when the heating container 1 which is a load moves on the top plate 2, since the arrangement of the heating container 1 with respect to the heating coil 3 is changed, the magnitude of the magnetic coupling between the heating coil 3 and the load is large. Changes. When the ON time of the switching element 4a in the inverter 4 is the same, the smaller the distance between the heating container 1 and the heating coil 3, the greater the magnetic coupling, and the smaller the heating coil current and the input current. . Moreover, since input power fluctuates due to a change in magnetic coupling, when feedback control is executed, the ON time of the switching element 4a of the inverter 4 is changed, and the magnitudes of the heating coil current and the input current also fluctuate. It will be. As a result, the high frequency current and the input current supplied from the inverter 4 to the heating coil 3 fluctuate. On the other hand, in the case of occurrence of spillage, the position of the heating container 1 with respect to the heating coil 3 does not change, so that the magnetic coupling does not change and the high-frequency current and input current supplied from the inverter 4 to the heating coil 3 change. There is nothing. Therefore, the input current of the inverter 4 is detected by the input current detector 7b, the high-frequency current supplied from the inverter 4 to the heating coil 3 is detected by the heating coil current detector 7a, and the detected input current and high-frequency current are stored. By storing in the unit 12, it is possible to detect changes in the input current and the high-frequency current, and to detect a change in the magnitude of the magnetic coupling between the heating container 1 and the heating coil 3. In the induction heating cooker of the first embodiment, the input current detection signal and the high frequency current detection signal are input to the boiling detection unit 11 as input / output current signals from the input current detection unit 7b and the heating coil current detection unit 7a every predetermined period (for example, , One cycle of commercial power supply = approximately every 16.7 milliseconds), and sequentially stored while data from the time point before the first predetermined period (T4) (for example, 2 seconds) to the present is updated. Stored in the unit 12.

FIG. 3B is a graph for explaining the detection operation in the load movement detection period (T4), and the vertical axis indicates the magnitude of the input current (Iin), the heating coil current (IL), or the ON time (Ton) of the switching element. The horizontal axis indicates the elapsed time. In the load movement detection period (T4), as shown in FIG. 3B, the spillover detection unit 11 is, for example, a fluctuation range (ΔIL) of the heating coil current (IL) detected by the heating coil current detection unit (load movement detection unit) 7a. ). For example, for the fluctuation range (ΔIL) of the heating coil current (IL), the maximum value (MAX) and the minimum value (MIN) of the heating coil current measured during the load movement detection period (T4) are obtained, and the difference between them is calculated. It is required by that. The load movement detection period (T4) is a change in the capacitance detected by the capacitance detection unit 10 with respect to the reference value (V0) corresponding to the capacitance detected by the capacitance detection unit 10 before spilling occurs. The amount (ΔV) is set so as to include the time point when the output reduction threshold (second variation: ΔV2) is reached. That is, during the load movement detection period (T4), the change amount (ΔV2) with respect to the reference value (V0) of the capacitance detection signal (Vd) indicated by the point C in FIG. 3A is the second change amount (ΔV2). ) Is included in the load movement detection period (T4). Thereby, the fluctuation range (ΔIL) of the heating coil current can be measured before, after, or before and after the time point when the change amount (ΔV) becomes equal to or greater than the output reduction threshold value (ΔV2).

When the fluctuation range (ΔIL) is less than a predetermined value (for example, 15 digits) at the end of the second overflow detection period (T2) indicated by a point D in FIG. It is determined that the change amount (ΔV) of the detection signal (Vd) is likely to have occurred due to spillage, and the third spillover period (T3) is entered, and the fluctuation range (ΔIL) is a predetermined value (for example, In the case of 15 digits) or more, it is determined that it is not caused by a spill, and the reference value update stop mode is shifted to the reference value update mode.
The load movement detection unit includes an on-time detection unit 7c that monitors the on-time (Ton: conduction period) of the switching element 4a instead of or together with the heating coil current detection unit 7a or the input current detection unit 7b. The on-time detection unit 7 c detects the change width of the on-time (conduction period: Ton) of one or more switching elements 4 a constituting the inverter 4, thereby increasing the magnitude of magnetic coupling between the heating coil 3 and the heating container 1. The fluctuation range (ΔTon) of the height is detected. The controller 8 drives the heating coil 3 by controlling on / off of the switching element 4a, and changes the heating output of the inverter 4 by changing the on-time of the switching element 4a (for example, lengthens the on-time). To increase the heating output). The on-time of the switching element 4a (when there are a plurality of switching elements 4a, the on-time of all the switching elements) is the same. For example, when the magnetic coupling decreases, the heating output of the inverter 4 decreases. In this case, in order to perform control to return to the set output, the control unit 8 changes the on-time (Ton) to be increased by feedback control. The on-time detection unit 7c as a load movement detection unit monitors the on-time (conduction period) of the switching element 4a and detects a change in the on-time (Ton) of the switching element 4a that occurs in response to a change in magnetic coupling. To do. In this way, by detecting the variation of the on-time (Ton) by the on-time detector 7c, whether or not the fluctuation is detected by measuring the variation width (ΔIL) of the heating coil current (IL) in the heating coil current detector 7a. As in the case of identifying the switching element 4a, the change in the load movement detection period (T4) of the ON time (Ton) of the switching element 4a is detected, the fluctuation range (ΔTon) of the magnetic coupling is measured, and the capacitance detection signal It is possible to identify whether or not the change amount (ΔV) of (Vd) is due to spillage.

When the capacitance change rate (for example, 8 digits / second) detected by the capacitance detection signal (Vd) is less than a predetermined value in the second leakage detection period (T2), It is determined that the user has touched 1 or the heating container 1 has been shifted, the reference value update stop mode is canceled, and the process proceeds to the reference value update mode. On the other hand, if the rate of change in capacitance detected by the capacitance detection signal (Vd) is greater than or equal to a predetermined value, it is determined that there is a possibility of spilling.
By the end of the second spill detection period (T2), the spill detection unit 11 is based on the capacitance change rate detected by the capacitance detection signal (Vd) and the fluctuation range of the magnitude of the magnetic coupling. Detects spilling. The fluctuation range of the magnitude of the magnetic coupling is not limited to the parameters of the heating coil current, the input current, and the on-time (conduction period) of the switching element, but is determined by the voltage or current generated in the inverter 4. It can be detected by measuring a parameter that fluctuates in response to a change in magnetic coupling and calculating a fluctuation range of each parameter.

After the transition to the third overflow detection period (T3), the overflow detection unit 11 waits by reducing the heating output to the second set value (P2) in order to determine the overflow detection. If it is detected during the third overflow detection period (T3) that the capacitance detection signal (Vd) has changed without being overflowed, the heating output is set to the first set value (without determining the overflow detection). Returning to P1), the reference value update stop process may be terminated. Thereby, it is possible to prevent the cooking from being interrupted unnecessarily.
As a change that does not occur in the capacitance detection signal (Vd), for example, the capacitance detection signal (Vd) is a predetermined value with respect to the maximum value (Vd (min)) detected in the reference value update stop mode. (For example, 15 digits) It is good also as a case where it jumps up.
When the spillage detection unit 11 determines that the spillage has occurred, the spillage detection unit 11 stops heating and displays the occurrence of the spillage on the display unit 20 or informs by voice. In order to perform the heating operation again in this state, it is necessary to first press the heating stop key.

In the reference value update stop mode, which starts when the detected change amount (ΔV) of the capacitance detection signal (Vd) becomes equal to or greater than the first change amount (ΔV1), at least one spilled electrode (9a to 9a to 9g) When the capacitance change rate, which is the change in capacitance in the detection signal from 9g), exceeds a predetermined value (for example, 145 digits / second), the induction heating operation is stopped instantaneously or the heating output May be configured to be reduced to a third setting value (P3: for example, 0.1 kW) lower than the second setting value (P2). In this case, the amount of change of the remaining two electrodes in the three electrodes 9 (left rear electrode 9a, left front electrode 9b, left center electrode 9c, or right rear electrode 9d, right front electrode 9e, right center electrode 9f) ( When both ΔV) are equal to or greater than a predetermined value (for example, 10 digits) with respect to the reference value (V0), it is determined that the heating container 1 may be touched, and the reference value is updated. Transition from the stop mode to the second standby mode. When the overflow detection unit 11 shifts to the second standby mode, the overflow detection operation that is executed in the reference value update mode and the reference value update stop mode is prohibited in the second standby period (for example, 2 seconds). When the second standby mode ends, the process shifts to the reference value update mode. In addition, you may comprise so that it may transfer to the 3rd standby mode which waits until the variation | change_quantity ((DELTA) V) is stabilized before shifting to a 2nd standby mode from a reference value update stop mode. In the third standby mode, if the amount of change (ΔV) with respect to the reference value (V0) stored in the reference value update stop mode is equal to or greater than a predetermined value (for example, 50 digits), the third standby period (for example, 2 (Seconds), and the operation is repeated until the value becomes less than the predetermined value.

The minimum capacitance detection signal (Vd (min)) detected in the reference value update stop mode (spillover determination period) and the detected capacitance detection signal (Vd) are not limited to the second overflow detection period. If a comparison is detected and a jump exceeding a predetermined value (for example, 15 digits) is detected, it is determined that the spillover state has not occurred, and the process returns to the reference value update processing operation after shifting to the second standby mode. This is because the capacitance signal does not jump abruptly in the spilled state.

In the reference value update stop mode, the three electrodes 9 (the left rear electrode 9a, the left front electrode 9b, the left center electrode 9c, or the right rear electrode) for detecting the capacitance of the heating container 1 in each heating coil 3 are used. The relevance of each electrostatic capacitance detection signal from the electrode 9d, the right front electrode 9e, and the right center electrode 9f) is used as a determination material for detection of overflowing. For example, if the capacitances of the three electrodes 9 show significantly different transitions (time changes), there is a possibility of small spills. On the other hand, if the capacitances of the three electrodes 9 show the same transition, there is a possibility that large spillage has occurred or the heating container 1 has been touched. When the capacity changes in the same manner, it may be determined whether or not there is a large spillage depending on the subsequent transition state. In the determination at that time, a threshold value serving as a determination criterion is set to a high value, and when the threshold value is exceeded, it is determined that there is a large spillage, thereby enabling a more accurate determination.
It should be noted that the capacitances of the three electrodes 9 change similarly, for example, in the three electrodes 9, each of the start points of the second overflow detection period (time point C in FIG. 3A) is included within a predetermined period. (For example, any one of the electrodes shifts to the second spill detection period within a period of 0.5 seconds after any one electrode shifts to the second spill detection period) In such a state, it is determined that the capacitance of the three electrodes 9 shows the same transition.

As described above, when the induction heating cooker of Embodiment 1 determines that there is a possibility of spilling in the second spillage determination period (T2), along with the end of the second spillover detection period (T2), It is guided when the third overflow detection period (T3) is entered and the heating output is reduced (the second setting value is changed to P2), and it is determined that the overflow has occurred after the third overflow detection period T3 ends. The heating operation is stopped. This state is shown in FIGS. 3A (a) and (b). As shown in (a) and (b) of FIG. 3A, the change amount (ΔV) from the reference value (V0) in the capacitance detection signal (Vd) is the first change amount (reference value update stop threshold: ΔV1). When this is the case, the reference value update mode ends and the reference value update stop mode is entered. In the reference value update stop mode, the capacitance detection signal (capacitance voltage at point A in FIG. 3A (a)) detected immediately before entering the reference value update stop mode is used as the reference value (V0). . When the detected capacitance detection signal (Vd) becomes larger than the second change amount (output reduction threshold: ΔV2) during the reference value update stop period, the process shifts to the second overflow detection period and is set in advance. When the second overflow detection period (T2), which is the period, ends, the process shifts to the third overflow detection period. When the third overflow detection period (T3) starts, the heating output of the inverter 4 is reduced (second set value: P2, for example, 0.3 kW). Thereafter, when the third overflow detection period (T3), which is a preset period, ends, the overflow detection is confirmed and the heating output is stopped.
In addition, the rate of change per unit time of the capacitance detection signal (Vd) is equal to or greater than a predetermined value (for example, 145 digits / second) in the second overflow detection period (T2) and the third overflow detection period (T3). When the heating output is further reduced (third set value P3: changed to 0.1 kW, for example) or heating is stopped, the spillage determination is confirmed.

In addition, during the induction heating operation of the induction heating cooker according to the first embodiment, when the user changes the output (changes the heating power) in the operation unit 18, the above-described overflow detection operation is reset and a new one is generated. The spill detection operation is started. However, in the newly set initial stage of the induction heating operation, the second standby time during which the heating output suppression operation of stopping the heating by the spillover detection operation or reducing to the third heating output is not performed is performed at the start of heating. It is set shorter than the waiting time (for example, 3 seconds). It should be noted that the length of the standby time during which no overflow detection operation is performed in this initial stage is appropriately set according to the situation (output, temperature, etc.).

The overflow detection unit 11 of the induction heating cooker according to the first embodiment compares the capacitance signal (Vd) output by the voltage detection unit 15 every predetermined period (for example, commercial power cycle) with a reference value (V0). Although the example configured as described above has been described, the capacitance of the electrode 9 is detected a plurality of times (for example, 5 or 6 times) within a predetermined detection period (for example, about 0.1 second), and a plurality of detected electrostatic capacitances are detected. An average value of the capacitance may be calculated and adopted as the capacitance signal (Vd), and the average value of the capacitance may be compared with the reference value (V0). With the latter configuration, when noise or the like is superimposed on the capacitance signal (Vd), it is possible to improve the detection accuracy of the overflowing state.

In addition, in the induction heating cooker of the first embodiment, the spill detector 11 is in any one of a plurality of capacitances detected a plurality of times within a reference value detection period (T0) (for example, 1 second). When the amount of change with respect to the reference value (V0) becomes equal to or greater than the reference value update stop threshold (3 digits), the update of the reference value (V0) to the storage unit 12 is stopped, and the detection period at that time is reset and new Alternatively, the measurement of the reference value detection period may be started, and the storage unit 12 may be configured to execute the reference value update process.

In the induction heating cooker according to the first embodiment, the capacitance detected by any one of the plurality of electrodes 9 (9a to 9g) provided near the periphery of each heating coil 3 is the reference value (V0). ), The reference value update process is executed when the amount of change is less than the reference value update stop threshold, and the reference value update stop process is executed when the amount of change is greater than the reference value update stop threshold. Furthermore, the induction heating cooker of Embodiment 1 reduces the heating output of the inverter 4 when the detected capacitance has a change amount equal to or greater than an output reduction threshold (for example, 14 digits) (second set value: P2), and when the fluctuation value of the high-frequency current detection signal in the overflow detection period becomes equal to or less than the predetermined fluctuation value, the induction heating cooker is stopped or the heating output of the inverter 4 is further reduced (third Set value: P3).

[Menu display]
4A to 4E show the states of the operation display unit 18 and the menu display unit of the display unit 20 in the induction heating cooker according to the first embodiment, and show the procedure for setting the overflow detection operation.
FIG. 4A is a display state diagram of the menu display unit in the operation unit 18 and the display unit 20 when the user sets the heating conditions before the induction heating operation of the first embodiment is performed. As shown in FIG. 4A, only the “menu” operation switch is displayed in the menu display section. When the user selects (presses) the “menu” mark, as shown in FIG. 4B, in addition to the “menu”, “heating”, “pan mark”, “fried food”, “baked food”, “kettle mark”, “Koketsu” and “Off / Start” marks are displayed. At this time, only the “heating” mark blinks.

In the state shown in FIG. 4B, when the “cut / start” mark is selected (pressed), the induction heating operation is started and the burn-in detection operation is started. The burning detection operation is to detect burning of the contents of the heating container 1 and is detected by the temperature detection unit 17 based on information such as a rapid temperature rise. During this induction heating operation, only the burn-out detection operation is activated, and the overflow detection operation is not started.

In the state shown in FIG. 4B, when the “menu” mark is selected (pressed), a menu display portion is displayed as shown in FIG. 4C. As shown in FIG. 4C, “Fukibokore” mark is newly displayed from the menu display section shown in FIG. 4B, and “Heating” and “Pot mark” are blinkingly displayed. That is, when the user selects (presses) the “cut / start” mark in this state, the induction heating operation is started, and the burn-in detection operation and the overflow detection operation are started. FIG. 4D shows the display state of the menu display section during the induction heating operation. As shown in FIG. 4D, “heating”, “pan mark”, “menu”, and “off / start” are displayed during the induction heating operation, and the user can change the menu at any time during the induction heating operation. It is possible to stop the heating operation.

As described above, during the induction heating operation in which the overflow detection operation is set, as a result of the above-described overflow detection operation, when the overflow detection is confirmed and the occurrence of the overflow is detected, as shown in FIG. “Blowout” flashes. In addition, in the induction heating cooker of Embodiment 1, it is the structure by which "Fukikobo" flashes and is displayed on the menu display part when it detects the overflow, but "Fukikobo" flashes and is in the state of being overflowing. It is good also as a structure alert | reported by an audio | voice.

In the menu display section of the induction heating cooker according to the first embodiment, every time the “menu” mark is pressed and selected, the “fried food”, “baked food”, “kettle mark” next to “heating” Then, “heating” blinks sequentially, and the object to be heated is selected. The “kettle mark” indicates a kettle operation.
The operation unit 18 in the induction heating cooker according to the first embodiment includes operation switches (left and right movements) required in the induction heating cooker such as selection of a heater, temperature setting (heating power adjustment), timer setting, and the like. Arrow marks to indicate, marks to indicate increase / decrease (+,-), and the like).

As described above, as specifically illustrated in the embodiment, the induction heating cooker of the present invention includes signals and inverters from a plurality of arc-shaped electrodes provided on the back of the top plate near the periphery of the heating coil. Based on the high-frequency current output by the sensor, the amount of change in capacitance generated in the electrode and the fluctuation state of the high-frequency current are detected with high accuracy, greatly reducing false detection of spillage in the heating vessel during induction heating operation. In addition, the occurrence of spilling can be reliably detected, and the induction heating cooker is highly reliable and safe.

It is possible to provide a highly reliable induction heating cooker that can greatly reduce the erroneous detection of spillage in the heating container that occurs during the induction heating operation to the market.

2 Top plate 3 Heating coil 4 Inverter 5 Rectifier 6 AC power supply 7a Heating coil current detection part (load movement detection part)
7b Input current detector (load movement detector)
7c On-time detector (load movement detector)
DESCRIPTION OF SYMBOLS 8 Control part 9 Electrode 9a-9f Electrode 10 Capacitance detection part 11 Overflow detection part 12 Memory | storage part 13 High frequency signal generator 14 Rectification part 15 Voltage detection part 18 Operation part 20 Display part

Claims

A top plate on which the heating container is placed;
A heating coil that is provided below the top plate and induction-heats the heating container;
An inverter for supplying a high frequency current to the heating coil;
An electrode provided on the back surface of the top plate in the vicinity of the periphery of the heating coil;
A capacitance detector for detecting a capacitance of the electrode by supplying a high frequency signal to the electrode;
A load movement detection unit for detecting a fluctuation range of the magnitude of the magnetic coupling between the heating container and the heating coil in a load movement detection period;
A storage unit that stores a reference value corresponding to the capacitance detected by the capacitance detection unit before a spill occurs;
A control unit that controls the heating output to be a set first set value,
When the amount of change with respect to the reference value in the capacitance detected by the capacitance detection unit is greater than or equal to an output reduction threshold and the fluctuation range of the magnitude of the magnetic coupling is less than a predetermined value, The heating output is reduced to a preset second setting value smaller than the first setting value, or a spillage suppression operation for stopping heating is performed, and the change amount is the output reduction threshold during the load movement detection period. An induction heating cooker configured to include a point in time reached.
The load movement detection unit includes a heating input / output detection unit that detects input / output of the inverter, and detects the variation range of the heating output detected by the heating input / output detection unit, thereby reducing the variation range of the magnetic coupling. The induction heating cooker of claim 1 configured to detect.
The load movement detection unit includes an on-time detection unit that monitors an on-time of a switching element that constitutes the inverter, and detects a change width of the on-time that is detected by the on-time detection unit. The induction heating cooker of Claim 1 comprised so that a fluctuation range might be detected.
When the amount of change is equal to or greater than the output reduction threshold, the overflow detection unit shifts to a second overflow detection period set for a predetermined period, and the fluctuation range of the magnitude of the magnetic coupling detected by the load movement detection unit is increased. 2. The induction heating cooker according to claim 1, wherein when it is detected that the value is less than a predetermined value, the operation of suppressing the overflow is performed after the end of the second overflow detection period.
The induction heating cooker according to claim 1 or 2, wherein the load movement detection unit is a heating coil current detection unit that measures a high-frequency current supplied to the heating coil.
The induction heating cooker according to claim 1 or 2, wherein the load movement detection unit is an input current detection unit that measures an input current of the inverter.
The overflow detection unit includes a reference value update mode and a reference value update stop mode, and when transitioning to the reference value update mode, the capacitance detected by the capacitance detection unit is stored in the storage unit as the reference value. When the change amount of the capacitance detected by the capacitance detection unit within the reference value detection period with respect to the reference value is less than the reference value update stop threshold smaller than the output reduction threshold, the reference value detection is performed. The capacitance detected by the capacitance detection unit within a period is updated as the reference value every time the reference value detection period elapses and is stored in the storage unit, and the electrostatic capacitance is detected within the reference value detection period. When the change amount of the capacitance detected by the capacitance detection unit with respect to the reference value is equal to or greater than the reference value update stop threshold, the reference value update stop mode for stopping the update of the reference value to the storage unit. Induction heating cooker according to claim 1 configured to shift to de.
The overflow detection unit detects the capacitance of the electrode a plurality of times within a reference value detection period, and a change amount of the plurality of capacitances detected by the capacitance detection unit with respect to the reference value is updated to the reference value. The induction heating cooking of Claim 7 comprised so that the said reference value might be updated by making the average value of several electrostatic capacitance detected within the said reference value detection period into the said new reference value when it is less than a stop threshold value. vessel.
When the overflow detection unit shifts to the reference value update mode, the capacitance of the electrode is detected a plurality of times within the reference value detection period, and a change amount of the detected plurality of capacitances with respect to the reference value is detected. The induction heating cooker of Claim 7 comprised so that the update of the said reference value with respect to the said memory | storage part may be stopped until it transfers to the said reference value update mode, when it is more than the said reference value update stop threshold value.
If the amount of change is equal to or greater than the output reduction threshold and does not determine that overflow is detected, the overflow detection unit shifts to the second standby mode after waiting for the reference value update stop mode and waits for the second standby period. The induction heating cooker according to claim 7, which is configured to shift to the reference value update mode later.
The induction cooking device according to claim 7, wherein the spill detector is configured to shift to a standby mode after starting heating and to shift to the reference value update mode after a standby period.
The overflow detection unit stores a maximum value of the capacitance detected by the capacitance detection unit after the amount of change becomes equal to or greater than the reference value update stop threshold, and when the capacitance decreases from the maximum value by a predetermined value or more, The induction heating cooker according to any one of claims 1 to 11, wherein the induction heating cooker is configured not to determine that the spilling is detected.