JP2020042969A - Induction heating cooker - Google Patents

Abstract

To provide a highly safe, reliable and efficient induction heating cooker capable of reliably maintaining the components below the respective temperature limit by appropriately adjusting the heating output according to the load including various matters to be heated.SOLUTION: The induction heating cooker has a control part (9) that controls and drives an inverter circuit (4) for supplying a high-frequency current to a heating coil (5) that heats the matters to be heated by high-frequency current flowing thereon. The induction heating cooker is configured to control stepwise the heating output of the heating coil according to the electrical characteristics of the heating coil, which changes depending on the object to be heated so as to control the duration of each step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an induction heating cooker for induction heating an object to be heated, and more particularly to an induction heating cooker made of a non-magnetic material such as copper or aluminum and capable of induction heating an object to be heated of a low-resistance material.

  The induction heating cooker is provided with a heating coil for induction heating an object to be heated, an inverter circuit for supplying a high-frequency current to the heating coil, a control unit for controlling the inverter circuit, and the like. These components generate heat due to losses in the components during the induction heating operation, and the component temperature rises. In particular, heating components such as a heating coil, a switching element provided in an inverter circuit, and a capacitor have a large loss and a high temperature. Therefore, it is necessary to control the drive to ensure that the temperature is not higher than a heat-resistant temperature.

  A conventional induction heating cooker has a configuration in which the temperature of a heat-generating component is detected and the output of a heating coil is reduced based on the detected temperature (for example, see Patent Document 1).

JP 2004-158278 A

  The induction heating cooker generates high-frequency magnetism by passing a current of several tens of kHz from the inverter to the heating coil, and an eddy current flows to a cooking pot, which is a heated object magnetically coupled to the heating coil, The pot itself generates heat. Non-magnetic materials have extremely low magnetic permeability compared to magnetic materials such as iron, and copper and aluminum have low resistance. In order to induction-heat a cooking pot made of such a material, the current flowing through the heating coil becomes large, and it is necessary to flow a high-frequency current. As a result, the induction heating cooker has a configuration in which a cooling mechanism is provided for the heat-generating component to cool it, and the component temperature is detected and the output is controlled so as not to exceed the heat-resistant temperature.

  The induction heating cooker disclosed in Patent Literature 1 is configured to drive and control the temperature of the component to be equal to or lower than the heat-resistant temperature based on the detected temperature of the component. In such a configuration in which the output is controlled based on the temperature detection, there is a high possibility that the detected temperature is affected by the ambient temperature, and the detected temperature is not highly reliable. Further, the temperature sensor has a problem that the response to the component temperature is poor. For this reason, in order to enhance the safety as a cooker, it is necessary to perform the output control based on the detected temperature with a margin between the output temperature and the heat-resistant temperature. Also, in the control based on the detected temperature, in order to ensure the safety of components even in the case of a sudden temperature change, it is necessary to set the upper limit temperature to a temperature lower than the heat resistant temperature of the components and perform output control. there were.

  The present invention, by appropriately adjusting the heating output according to the load of the various objects to be heated, it is possible to reliably maintain the temperature below the heat-resistant temperature of the component, appropriately perform temperature management for the component, An object of the present invention is to provide an induction heating cooker with high safety, reliability and efficiency.

An induction heating cooker according to one embodiment of the present invention,
A heating coil through which a high-frequency current flows to heat the object to be heated;
An inverter circuit for supplying a high-frequency current to the heating coil;
A control unit for driving and controlling the inverter circuit,
The heating output of the heating coil is controlled in a stepwise manner, and the duration of each step is controlled in accordance with the electrical characteristics of the heating coil that vary according to the object to be heated.

  The induction heating cooker of the present invention appropriately controls the heating output in accordance with the load, which is various kinds of objects to be heated, appropriately performs the temperature management for the components, reliably holds the components at the heat-resistant temperature or lower, It is possible to maintain a desired heating power, and it becomes a safe, reliable and efficient cooking appliance.

FIG. 1 is a block diagram illustrating a configuration of an induction heating cooker according to a first embodiment of the present invention. Graph showing the results of an experiment conducted by placing various objects to be heated on a heating coil Graph showing experimental results of measuring electrical characteristics of a heating coil on which various “non-magnetic metal pots” are placed Flow chart showing induction heating operation in the induction heating device of the first embodiment. Flow chart showing power down processing in the induction heating device of the first embodiment. Flow chart showing power down processing in the induction heating device of the first embodiment. FIG. 3 is a diagram showing a first power-down operation table in the induction heating device according to the first embodiment. FIG. 4 is a diagram showing a second power-down operation table in the induction heating device according to the first embodiment. In the induction heating cooker according to the first embodiment, a graph showing transition of a cycle, a heating output, a coil temperature, and a capacitor temperature in a power down process and a power adjustment process.

  Hereinafter, an embodiment of an induction heating cooker according to the present invention will be described with reference to the accompanying drawings. In addition, the induction heating cooker of the present invention is not limited to the configuration of the induction heating cooker described in the following embodiment, and is based on a technical idea equivalent to the technical idea described in the following embodiment. Therefore, the present invention can be applied to the configuration of various devices using induction heating.

First, various embodiments of the induction heating cooker of the present invention will be described.
The induction heating cooker according to the first aspect of the present invention comprises:
A heating coil through which a high-frequency current flows to inductively heat the object to be heated;
An inverter circuit that supplies a high-frequency current to the heating coil; and a control unit that drives and controls the inverter circuit.
The heating output of the heating coil is controlled in a stepwise manner, and the duration of each step is controlled in accordance with the electrical characteristics of the heating coil that vary according to the object to be heated. In the induction heating cooker according to the first aspect thus configured, the heating output is appropriately adjusted according to various types of objects to be heated, the temperature is reliably maintained at or below the heat resistant temperature of the component parts, and the desired heating power is maintained. can do.

  An induction heating cooker according to a second aspect of the present invention is the induction heating cooker, wherein the control unit according to the first aspect is configured such that the control unit outputs a heating output from the heating coil in accordance with an inductance of the heating coil that changes according to an object to be heated. And the duration of each stage may be controlled.

  In the induction heating cooker according to a third aspect of the present invention, the control unit according to the first aspect or the second aspect is configured such that, in accordance with a resistance component of the heating coil that changes according to an object to be heated, The heating output of the heating coil may be controlled stepwise, and the duration of each step may be controlled.

The induction heating cooker according to a fourth aspect of the present invention, in the first aspect, further includes a coil current detection unit that detects a coil current flowing through the heating coil in the induction heating of the object to be heated,
The control unit may be configured to control the heating output of the heating coil in a stepwise manner based on the coil current detected by the coil current detecting unit, and to control the duration of each step.

According to a fifth aspect of the present invention, there is provided the induction heating cooker according to the first or fourth aspect, wherein the period detecting unit detects a period of a coil current flowing through the heating coil in the induction heating of the object to be heated. With
The control unit may be configured to control the heating output of the heating coil stepwise based on a cycle detected by the cycle detection unit.

  An induction heating cooker according to a sixth aspect of the present invention is the induction heating cooker according to any one of the first to fifth aspects, wherein the control unit comprises a nonmagnetic metal whose object to be heated contains aluminum or copper. When constituted by, the heating output in the heating coil may be controlled stepwise according to the electrical characteristics of the heating coil, and the duration of each step may be controlled.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same components are denoted by the same reference numerals, and description thereof may be omitted. In the drawings, each component is schematically shown mainly for easy understanding.

  Each of the embodiments described below shows one specific example of the present invention. The numerical values, shapes, configurations, steps, order of steps, and the like shown in the following embodiments are merely examples, and do not limit the present invention. Among the components in the following embodiments, components that are not described in independent claims indicating the highest concept are described as arbitrary components.

(Embodiment 1)
FIG. 1 is a block diagram illustrating a configuration of an induction heating cooker according to a first embodiment of the present invention. As shown in FIG. 1, the induction heating cooker according to the first embodiment includes a rectifier circuit 2 for rectifying an AC from an AC power supply 1, a smoothing circuit 3 including a choke coil and a capacitor, and a switching element such as an IGBT. The apparatus includes an inverter circuit 4 and a heating coil 5 to which a high-frequency current is supplied from the inverter circuit 4 and inductively heats the magnetically coupled object 10 to be heated. In the induction heating cooker according to the first embodiment, the coil current detecting unit 6 that detects the coil current flowing through the heating coil 5, the cycle detecting unit 7 that detects the cycle of the coil current flowing through the heating coil 5, and the inverter circuit 4. A pot type judging unit 8 that detects a flowing coil current or the like and judges the type of the object to be heated 10 arranged on the top plate on the heating coil 5, a coil current detecting unit 6, a period detecting unit 7, and a pan type judging. A control unit 9 is provided for driving and controlling the switching elements of the inverter circuit 4 based on various information from the unit 8 and the like.

  In the first embodiment, in addition to the above-described configuration, a configuration generally provided in the induction heating cooker, for example, various detection means (for example, temperature detection and position detection), and a configuration for the user to perform a setting operation Operation means and the like are provided. Further, the induction heating means including the heating coil is not limited to one set, but may be configured to have a plurality of sets. In the induction heating cooker of the present invention, a resistance heating means such as a radiant heater or a halogen heater may be provided as another heating means, or an oven using a sheathed heater or the like may be provided.

  In the induction heating cooker according to the first embodiment, when induction heating is started, the control unit 9 outputs a control signal to the inverter circuit 4 to drive a switching element of the inverter circuit 4. When the switching element of the inverter circuit 4 is driven, a high-frequency current is supplied to the heating coil 5. When a high-frequency current is supplied to the heating coil 5, an object to be heated 10 (for example, an iron pot, a stainless steel pot, a copper pot, or an aluminum pot) placed on a top plate immediately above the heating coil 5 is generated by high-frequency magnetism from the heating coil 5. Various cooking metal pans such as pans) are induction heated. In the following description, an iron pot, a stainless steel pot, or the like in which induction heating is performed by a high-frequency current of a low frequency (for example, about 20 kHz) flowing through the heating coil 5 is referred to as a “magnetic metal pot”, and a high frequency flowing through the heating coil 5 is used. A copper pot or an aluminum pot in which induction heating is performed with a high-frequency current (for example, about 90 kHz) is referred to as a “non-magnetic metal pot”.

  In the induction heating cooker according to the first embodiment, in the initial stage of induction heating, the type of the cooking pot as the object to be heated 10 placed at a predetermined heating position on the top plate is determined. The pot type determination unit 8 provided in the induction heating cooker performs the pot type determination process for a certain period immediately after the start of the induction heating. The pot type determination process is based on the current flowing through the inverter circuit 4 in the initial stage of the induction heating, the voltage between the elements, and the like, and determines whether or not the cooking pot is capable of induction heating and, if induction heating is possible, the “magnetic metal pot” It is determined whether it is a "non-magnetic metal pot". As a result of the determination by the pan type determining unit 8, if the cooking pot is capable of induction heating, the control unit 9 outputs a control signal to the inverter circuit 4. As a result, in the induction heating cooker according to the first embodiment, a desired high-frequency current is supplied from the inverter circuit 4 to the heating coil 5, and the induction heating of the object 10 arranged on the top plate on the heating coil 5 is performed. Is executed.

  Generally, in an induction heating cooker, a high frequency magnetism is generated by flowing a current of several tens of kHz from an inverter circuit to a heating coil, and an eddy current flows in a metal pot magnetically coupled to the heating coil. In this configuration, the metal pot itself generates heat. In particular, "non-magnetic metal pots" have lower magnetic permeability than "magnetic metal pots" such as iron, and copper and aluminum have low resistance. In order to inductively heat such a “non-magnetic metal pot”, the current flowing through the heating coil increases, and it is necessary to flow a high-frequency current. As a result, in a conventional induction heating cooker, a cooling mechanism for a heat-generating component is provided, and output control is performed based on the detected component temperature.

  The induction heating apparatus according to the first embodiment of the present invention has a configuration in which a power-down process described later is performed when an “nonmagnetic metal pan” such as a copper pan or an aluminum pan is induction-heated. This power-down process is not based on the component temperature, but is a configuration in which the output is appropriately adjusted according to the material and shape of the object to be heated 10 serving as a load, and the arrangement (positional displacement) with respect to the heating coil 5. .

  The power consumption P in the induction heating device is proportional to the skin resistance Rs determined by the material of the cooking pot as the object to be heated 10 and the like, and proportional to the square of the magnetic field H. The skin resistance Rs is proportional to the square root of a value obtained by multiplying the resistivity ρ of the cooking pot, the magnetic permeability μ of the cooking pot, and the frequency of the coil current flowing through the heating coil 5, and the magnetic field H is the number of turns (turns) of the heating coil 5. N) is proportional to the current I flowing through the heating coil 5. Therefore, the power consumption P can be expressed by the following equation (1).

  From the formula (1), "non-magnetic metal pan" such as copper pan and aluminum pan has a smaller magnetic permeability than "magnetic metal pan" such as iron pan, so that the same electric power flows through the heating coil 5 to obtain the same electric power. It is necessary to set the frequency of the current (coil current) high or increase the current value of the coil current. In the induction heating device according to the first embodiment, when the object to be heated 10 is determined to be a “non-magnetic metal pot” by the pot type determination unit 8, a higher driving frequency (“magnetic metal pot”) is used. For example, it is set to 90 kHz.

  In a general resonance circuit, the resonance frequency (f) of the heating coil (L) and the resonance capacitor (C) is given by the following equation (2).

  In the induction heating apparatus according to the first embodiment, an object to be heated (“non-magnetic metal pan” or “magnetic metal pan”) 10 is placed directly above the heating coil 5 via a top plate. And the object to be heated 10 are magnetically coupled. Therefore, the resonance frequency at the time of induction heating in the induction heating device is affected by the object to be heated 10 on the heating coil 5.

  The inventor has proposed various objects to be heated 10 to be subjected to induction heating, for example, iron pans, copper pans, and aluminum pans having different shapes of pan bottoms having large, medium, and small diameters, and different pans of the pan bottoms. An experiment was conducted in which various cooking pots were placed on the heating coil 5 and electric characteristics of the heating coil 5 to which the object to be heated 10 was magnetically coupled were examined. As electrical characteristics, an inductance (Ls [μH]) and a resistance component (Rs [Ω]) were measured.

  FIG. 2 is a graph showing the results of an experiment in which various objects to be heated (“non-magnetic metal pan” or “magnetic metal pan”) 10 are arranged immediately above the heating coil 5 and are magnetically coupled. In this experiment, the test was carried out on various cooking pots distributed on the market as the object to be heated 10, and various types of cooking pots having different applications and cooking pots having different materials, shapes and thicknesses were used. . In FIG. 2, the horizontal axis represents the inductance (Ls [μH]), and the vertical axis represents the resistance component (Rs [Ω]). In the graph of FIG. 2, a hatched area indicated by a symbol A is an area where measured values appear when various “non-magnetic metal pots” are disposed immediately above the heating coil 5. A hatched area indicated by a symbol B is an area where measured values appear when the “magnetic metal pot” is disposed immediately above the heating coil 5. In the experiment shown in FIG. 2, a signal of a frequency (for example, 23 kHz) when the “magnetic metal pot” is induction-heated to the heating coil 5 was supplied to measure the electrical characteristics.

  FIG. 3 shows a case where various “non-magnetic metal pots” are arranged and a signal of a frequency (for example, 90 kHz) when the “non-magnetic metal pot” is induction-heated to the magnetically coupled heating coil is supplied. 5 is a graph showing an experimental result of measuring electric characteristics. As a result of measuring the inductance and the resistance component of the heating coil to which the “non-magnetic metal pot” was magnetically coupled, it was understood that there was a certain tendency in various “non-magnetic metal pots” having different materials, shapes, and the like. As shown in the graph of FIG. 3, when the general copper pan and the aluminum pan are simply compared, the copper pan has a lower electrical resistance component [Ω]. When only the diameter of the pot bottom is compared, the smaller the diameter, the larger the inductance [μH] of the electrical characteristics. Further, with respect to the warpage of the pot bottom, the larger the warpage, the larger the inductance [μH] and the smaller the resistance component [Ω]. However, the above tendency is in principle, and the electrical characteristics change due to factors such as the manufacturing method, the thickness of the pot, the difference in the shape and the configuration due to the difference in use, and the like, in addition to the material and the shape.

  In the graph shown in FIG. 3, the cycle of the coil current frequency flowing through the heating coil 5 increases as the inductance increases. Also, as the resistance component decreases, the coil current increases. Therefore, in general, when a copper pot of “non-magnetic metal pot” is placed on the heating coil 5 as the object to be heated 10, the coil current becomes larger than when an aluminum pot is placed. Further, when the diameter of the pot bottom of the object to be heated 10 is small, the cycle of the coil current frequency becomes large as compared with the case where the diameter of the pot bottom is large.

  As described above, the electrical characteristics of the heating coil 5 are greatly different depending on the object to be heated 10 which is arranged on the heating coil 5 and magnetically coupled. In the induction heating cooker according to the first embodiment, the pot type determination process is performed based on the change in the electrical characteristics of the heating coil 5 and the components (the heating coil 5, the switching element, and the like) are set to the heat-resistant temperature. A power-down process, which will be described later, can maintain a desired thermal power while reliably holding the power below.

  FIG. 4 is a flowchart illustrating an induction heating operation performed in the induction heating device according to the first embodiment. When the user places the cooking pot, which is the object to be heated 10, at a predetermined position on the top plate, sets the heating power, the heating time, and the like, and performs an operation of starting cooking, the induction heating operation is started. In step 101, the above-described pot type determination processing is executed. In the pot type determination process, based on the current flowing through the inverter circuit 4, the voltage between the elements, and the like, if the cooking pot is capable of induction heating, and if the cooking pot is capable of induction heating, the cooking pot is a “magnetic metal pot”. The pot type is determined whether it is a "non-magnetic metal pot".

  In step 102, it is determined whether the object to be heated 10 is a “non-magnetic metal pot” or a “magnetic metal pot” based on the detection result of the pot type determination process. If the object to be heated 10 is a “magnetic metal pot”, in step 104, the control unit 9 drives the inverter circuit 4 at a drive frequency for the “magnetic metal pot”, and supplies the first coil current frequency to the heating coil 5. The electric current of F1 flows and the object to be heated 10 is induction-heated.

  On the other hand, if the object to be heated 10 is a “non-magnetic metal pot”, the control unit 9 drives the inverter circuit 4 at the drive frequency for the “non-magnetic metal pot” in step 103, and The current of the two-coil current frequency F2 flows, and the object to be heated 10 is induction-heated. The second coil current frequency F2 for inductively heating the “non-magnetic metal pan” is a higher frequency than the first coil current frequency F1 for inductively heating the “magnetic metal pan”, for example, the second coil current frequency. F2 is in the range of 60 kHz to 90 kHz, and the first coil current frequency F1 is in the range of 20 kHz to 30 kHz (F2> F1).

  After the induction heating is started in step 103, a "power-down process" for maintaining a desired heating power while reliably maintaining the components (the heating coil 5, the switching element, and the like) at or below the allowable temperature limit is performed (step 103). 105). In the case where the object to be heated 10 is a “non-magnetic metal pot”, the current flowing through the heating coil 5 is larger than in the case of the “magnetic metal pot”, so that the temperature of the heating coil 5 increases more. For this reason, in the induction heating apparatus of the first embodiment, after the pot type determination processing, induction heating is performed at the first heating output, and a power-down processing described later is performed for a rise in the temperature of the heating coil. In addition, after the start of heating, a low heat power may be set for a while, and a configuration may be adopted in which empty baking detection is performed to detect a large rise in the temperature of the pan when the amount of food or oil in the pan is small. .

(Power down processing)
5A and 5B are flowcharts showing a power down process in the induction heating device according to the first embodiment. In the induction heating device of the first embodiment, when the induction heating operation of heating target 10 by heating coil 5 is started, the power-down process is started.

  When the power-down process starts, a cycle (CYC) of a coil current flowing through the heating coil 5 magnetically coupled to the object to be heated 10 is detected (step 201). Further, the coil current (IL) after a predetermined time has elapsed from the start of heating is detected (steps 202 and 203). Since the current immediately after the start of the heating has fluctuations, the current is detected when the coil current (IL) is stabilized after a certain period of time. The detection of the coil current (IL) is always performed, and an average value of the coil current during a predetermined period, for example, 30 seconds may be used.

  Based on the detected cycle (CYC) and coil current (IL), the first power-down process is performed using the first power-down operation table Ta1 for the non-magnetic metal pot. FIG. 6A is a diagram showing the first power-down operation table Ta1. In FIG. 6A, “a1”, “b1”, and “c1” indicate specific numerical values of the cycle (CYC), and “A1”, “B1”, “C1”, and “D1” This shows specific numerical values of the coil current (IL). These numerical values have a relationship of “a1” <“b1” <“c1” and “A1” <“B1” <“C1” <“D1”.

  As shown in FIG. 6A, the detected cycle (CYC) is assigned to any of the first, second, third, and fourth periodic zones divided into four as the periodic condition. It is determined whether this is the case. Further, in the corresponding periodic zone, it is determined which of the five divided current zones the detected coil current (IL) corresponds to, and the time for reducing the heating output (first power down) Time PD1) is determined (step 204). In the first power-down operation table Ta1 shown in FIG. 6A, the specific numerical values of the division of the period condition into four, the division of the coil current condition into five, and the power-down time from the start of heating are exemplary, and the present invention is not limited thereto. The present invention is not limited to this example, and is configured to appropriately divide the power into a desired number so as to have a desired power down time and perform an appropriate power down process that can reliably maintain the heat resistant temperature of the component.

  In step 205, it is determined whether the determined first power down time PD1 has elapsed. If the first power down time PD1 has not elapsed, the process returns to step 201, and the cycle (CYC) of the coil current is detected. In the power-down process, the cycle (CYC) is constantly detected and the corresponding cycle is determined in order to determine whether or not a so-called “pan shift” that shifts the cooking pot as the object to be heated 10 during the induction heating has occurred. Confirmation of the zone is performed.

  If the first power down time PD1 has elapsed, a process of reducing the output from the first heating output to the second heating output is performed (Step 207). For example, after the elapse of the first power down time PD1, the heating output is reduced from 2600 W (first heating output) to 2000 W (second heating output). Steps 201 to 206 described above constitute the first stage power down processing.

  In the second-stage power-down process performed next, the same process as the first-stage power-down process is performed. That is, the cycle (CYC) of the coil current is detected (Step 207), and the coil current (IL) is detected (Step 208).

  In step 209, based on the detected cycle (CYC) and coil current (IL), a second-stage power-down process is performed using the second power-down operation table Ta2 for the non-magnetic metal pot. FIG. 6B is a diagram showing the second power-down operation table Ta2. In FIG. 6B, “a2”, “b2”, and “c2” indicate specific numerical values of the cycle (CYC), and “A2”, “B2”, “C2”, “D2”, “E2”, “F2”, and “G2” indicate specific numerical values of the coil current (IL). These numerical values have a relationship of “a2” <“b2” <“c2” and “A2” <“B2” <“C2” <“D2” <“E2” <“F2” <“G2”.

  In the power-down process of the second stage, similarly to the power-down process of the first stage, the second power-down operation table Ta2 shown in FIG. 6B is used to reduce the heating output (second power-down time PD2). Is determined (step 209). In the second power-down operation table Ta2 shown in FIG. 6B, similarly to the first power-down operation table Ta1 shown in FIG. 6A, the period condition is divided into four, the coil current condition is divided into eight, and the power from the start of heating is calculated. The specific numerical value of the down time is an example, and the present invention is not limited to this example and is set as appropriate.

  If the second power-down time PD2 determined using the second power-down operation table Ta2 has elapsed, the output is reduced from the second heating output to the third heating output (see step 211 in FIG. 5B). For example, when the second power-down time PD2 (up to 10 minutes from the start of heating) has elapsed, the heating output is reduced from 2000 W (second heating output) to 1800 W (third heating output). Steps 207 to 211 in the flowcharts shown in FIGS. 5A and 5B are the second stage power down processing.

  After the completion of the power-down process of the second stage, it is determined that the heating operation of the heating coil 5 in the induction heating cooker has been completed and the set heating power has been reached, and a normal power adjustment process is performed. In the power adjustment process, if the coil current (IL) detected in step 212 exceeds the power down threshold, power down adjustment of the heating output is performed so as to decrease by a predetermined power (for example, 100 W). On the other hand, if the detected coil current (IL) is below the power-up threshold, power-up adjustment of the heating output is performed so as to increase by a predetermined power (for example, 100 W) (see step 213 in FIG. 5B).

  As described above, when the heating end command is issued in a situation where the power adjustment process that maintains the predetermined temperature in the induction heating operation is performed, for example, when the cooking time set by the user ends, or when the user When the operation for ending the heating cooking is performed, the induction heating operation ends.

  As the coil current (IL) used in the power down process and the power adjustment process in the induction heating operation, an average value of current values detected during a predetermined period (for example, a period of 30 seconds) may be used. . Further, as the coil current (IL), the current fluctuates immediately after the heating output largely changes, so that the coil current for a predetermined period (for example, 5 seconds) may be excluded from the detection target immediately after the heating output is changed.

  FIG. 7 shows the cycle (CYC), heating output (power consumption), coil temperature, and capacitor temperature in the first and second stages of the power-down process and the power adjustment process in the induction heating cooker according to the first embodiment. 5 is a graph showing the transition of. As shown in FIG. 7, the temperatures of the heating coil 5 and the capacitor to which the current is supplied from the inverter circuit 4 are maintained at or below the respective heat-resistant temperatures, and the temperature difference up to the heat-resistant temperature is used to ensure the safety of the components. It is possible to maintain a temperature zone near the temperature limit that can be achieved.

  In the induction heating cooker according to the first embodiment, when the object to be heated 10 is a metal having a low resistance including aluminum or copper and a low magnetic permeability, the control unit 9 determines the electrical characteristics of the heating coil 5. Accordingly, an example has been described in which the heating output of the heating coil 5 is controlled stepwise and the duration of each step is controlled, but the present invention is not limited to such a configuration. For example, as a modification of the induction heating cooker, even when the object to be heated 10 is a high resistance metal including iron or stainless steel and has a high magnetic permeability, the object to be heated 10 In the case where the component temperature increases due to the shape (dimensions) of the object or the arrangement (positional deviation) of the object to be heated 10 with respect to the heating coil, a configuration similar to the power down process described in the first embodiment may be adopted. Good.

  As described above, the induction heating cooker according to the first embodiment includes the cycle and current value of the coil current flowing through the heating coil 5 immediately below the top plate on which the object to be heated 10 is placed, that is, the object to be heated. In accordance with the electrical characteristics of the magnetically-coupled heating coil, power-down processing for the heating output from the start of heating is performed stepwise, and the duration of the heating output in each stage is controlled. In this way, by performing the power-down process stepwise and controlling the duration of the heating output in each step, it is possible to appropriately perform temperature control on components such as the heating coil and the capacitor in the induction heating operation. Become.

  As described in the first embodiment, the induction heating cooker according to the present invention starts heating in accordance with the electrical characteristics (including, for example, the resistance component and the inductance) of the heating coil to which the object to be heated is magnetically coupled. The heating output from the heater is controlled stepwise, and the duration of each step is controlled according to the electrical characteristics of the heating coil to which the object to be heated is magnetically coupled. As described above, the induction heating cooker of the present invention has a configuration in which the heating output from the start of heating is controlled stepwise according to the load, and the duration of the heating output in each step is controlled. As a result, in the induction heating cooker of the present invention, in the induction heating operation, it is possible to appropriately perform temperature management for components such as a heating coil and a capacitor to which a current from the inverter circuit is input, and to achieve safety and reliability. A highly efficient and efficient cooking utensil can be constructed.

  Although the present invention has been described in some embodiments with some detail, this configuration is exemplary and the disclosed content of the embodiments should vary in the details of the configuration. In the present invention, the replacement, combination, and change of the order of the elements in the embodiments and the modified examples can be realized without departing from the scope and spirit of the claimed invention.

  INDUSTRIAL APPLICABILITY The induction heating cooker of the present invention can construct a safe, reliable, and efficient cookware, and thus has high market value.

REFERENCE SIGNS LIST 1 AC power supply 2 Rectifier circuit 3 Smoothing circuit 4 Inverter circuit 5 Heating coil 6 Coil current detection unit 7 Period detection unit 8 Pot type determination unit 9 Control unit 10 Heated object

Claims (6)

A heating coil through which a high-frequency current flows to inductively heat the object to be heated;
An inverter circuit that supplies a high-frequency current to the heating coil, and a control unit that drives and controls the inverter circuit,
Induction heating cooking in which the heating output of the heating coil is controlled in a stepwise manner and the duration of each step is controlled in accordance with the electrical characteristics of the heating coil that varies according to the object to be heated. vessel.   The control unit is configured to control a heating output in the heating coil in a stepwise manner and to control a duration of each step in accordance with an inductance of the heating coil that changes according to an object to be heated. Item 2. An induction heating cooker according to Item 1.   The control unit is configured to control the heating output in the heating coil in a stepwise manner according to a resistance component of the heating coil that changes in accordance with an object to be heated, and to control the duration of each step. The induction heating cooker according to claim 1. A coil current detection unit that detects a coil current flowing through the heating coil during induction heating of the object to be heated,
The control unit is configured to control a heating output of the heating coil in a stepwise manner based on a coil current detected by the coil current detection unit and to control a duration of each step. 2. The induction heating cooker according to 1 .. In the induction heating for the object to be heated, a period detecting unit that detects a period of a coil current flowing through the heating coil,
The induction heating cooker according to claim 1, wherein the control unit is configured to control a heating output of the heating coil in a stepwise manner based on a cycle detected by the cycle detection unit.   When the object to be heated is made of a non-magnetic metal including aluminum or copper, the control unit controls the heating output of the heating coil in a stepwise manner according to the electrical characteristics of the heating coil. The induction heating cooker according to any one of claims 1 to 5, wherein the induction cooker is configured to control a duration of the heating.

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