Induction heating conditioner

Abstract

To provide an induction heating cooker that controls a cooking vessel so as to increase the heating capacity when using the cooking vessel having different bottom characteristics at the center and the outer periphery.SOLUTION: When an induction heating cooker is used with normal heating control in which high-frequency current of the same frequency is supplied to the inner and outer heating coils for a cooking vessel in which the material properties of the center and outside of the bottom surface are different, with the material properties of the outer bottom surface being "non-magnetic," in an operating condition setting step, a high-frequency current of a frequency suitable for the material properties of the center side of the cooking vessel is supplied to the inner heating coil, and the supply of high-frequency current to the outer heating coil is stopped.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to an induction heating cooker that heats one cooking vessel with a plurality of heating coils. [Background technology]

[0002] A known conventional induction heating cooker has the function of heating one cooking container with multiple heating coils, and stabilizes the power supplied to the heating coils by making the drive frequencies of the multiple heating coils the same (see, for example, Patent Document 1). Patent Document 1 also describes that in the induction heating cooker described above, if the ratio of the current value flowing through the internal heating coil to the current value flowing through the external heating coil during load determination before cooking starts is less than a predetermined value, the limit value of the current flowing through the external heating coil after cooking starts is set lower than when the ratio exceeds this predetermined value, thereby improving the safety of the circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2016-72172 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the induction heating cooker described in Patent Document 1, when the material of the bottom of the cooking vessel is different between the center and the outer periphery, particularly when a cooking vessel is used in which the base is made of a low-resistance material such as aluminum and the center is thermally sprayed or affixed with a magnetic metal such as iron or stainless steel with a high resistance, the internal heating coil below the center must be driven at a drive frequency suitable for the low-resistance material such as aluminum on the outer periphery to prevent damage to the switching element due to overcurrent.As a result, a drive frequency suitable for the material of the center of the cooking vessel cannot be supplied to the internal heating coil, which inhibits heating of the cooking vessel and reduces usability for the user.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an induction heating cooker that improves the amount of heat given to a cooking container and makes it easier for users to use when using a cooking container whose bottom material is different on the center and outside. [Means for solving the problem]

[0006] The induction cooker of the present disclosure includes a top plate on which a cooking container is placed, and a heater provided below the top plate. 、 The inner heating coil heats the center of the cooking vessel, and the heating coil is located under the top plate. 、 an outer heating coil for heating the outside of the cooking vessel; an inverter circuit for supplying high-frequency current to the inner heating coil and the outer heating coil; and a control unit for controlling the inverter circuit; a notification unit that notifies a user of the operating status of the control unit; The control unit has a characteristic acquisition step of acquiring the characteristics of the material of the center side and the outside of the bottom surface of the cooking vessel, and an operating condition determination step of setting the frequency of the high-frequency current to be supplied to the inner heating coil and the outer heating coil in accordance with the characteristics of the material of the cooking vessel, and the control unit determines whether or not the cooking vessel has a "non-magnetic" material characteristic when used under normal heating control in which high-frequency currents of the same frequency are supplied to the inner heating coil and the outer heating coil. 、 A high-frequency current with a frequency suited to the characteristics of the material at the center of the cooking vessel is supplied to the inner heating coil, and the supply of high-frequency current to the outer heating coil is stopped. The notification unit notifies the user that the heating capacity of a cooking vessel is reduced when the cooking vessel has different material properties between the center and outside of the bottom surface and the material property of the outside of the bottom surface is "non-magnetic" and is used under normal heating control in which high-frequency currents of the same frequency are supplied to the inner and outer heating coils. This is what we do. [Effects of the Invention]

[0007] According to the induction heating cooker of the present disclosure, when using a cooking container whose bottom material is different between the center and the outside and the outside has "non-magnetic" properties, the amount of heat supplied to the cooking container can be improved by driving the inner heating coil at a frequency suitable for the properties of the material on the center side of the cooking container. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a schematic diagram showing an entire induction heating cooker according to a first embodiment. [Figure 2] 1 is a schematic diagram showing a heating coil of an induction heating cooker according to a first embodiment. [Figure 3] 1 is a circuit diagram of an induction heating cooker according to a first embodiment. [Figure 4] 3 is a schematic diagram of a notification section of the induction heating cooker according to the first embodiment. FIG. [Figure 5] 1 is a schematic diagram showing the positional relationship between a cooking vessel and a heating coil of an induction heating cooker according to Embodiment 1. FIG. [Figure 6] 1 is a schematic diagram showing the positional relationship between a cooking vessel and a heating coil of an induction heating cooker according to Embodiment 1. FIG. [Figure 7] 1 is a schematic diagram showing the positional relationship between a cooking vessel and a heating coil of an induction heating cooker according to Embodiment 1. FIG. [Figure 8] FIG. 2 is a control block diagram of the induction heating cooker according to the first embodiment. [Figure 9] FIG. 4 is a flowchart showing an operation performed before the start of cooking by the induction heating cooker according to the first embodiment. [Figure 10] FIG. 4 is a flowchart of a center-side characteristic determination step of the induction heating cooker according to the first embodiment. [Figure 11] FIG. 4 is a flow chart of an outside characteristic determination step of the induction heating cooker according to the first embodiment. [Figure 12] FIG. 3 is a database diagram used to set operating conditions for normal heating control of the induction heating cooker according to the first embodiment. [Figure 13] FIG. 3 is a database diagram used to set operating conditions for alternate heating control of the induction heating cooker according to the first embodiment. [Figure 14] 5 is a diagram showing the contents of notification by a display unit and a voice notification unit of the induction heating cooker according to the first embodiment. FIG. [Figure 15] 5 is a diagram showing the contents of notification by a display unit and a voice notification unit of the induction heating cooker according to the first embodiment. FIG. [Figure 16] 5 is a diagram showing the contents of notification by the heat lamp of the induction heating cooker according to the first embodiment. FIG. [Figure 17] 5 is a diagram showing the contents of notification by the heat lamp of the induction heating cooker according to the first embodiment. FIG. [Figure 18] FIG. 4 is a diagram showing the driving time of the inverter circuit 8 when the induction heating cooker according to the first embodiment is operated under alternating heating control. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiment 1 The present disclosure is an invention that can be applied to induction heating cookers in general, and in this embodiment, an induction heating cooker in which an object to be heated is placed on a top plate will be described as an example. The present disclosure can also be applied to other induction heating cookers, such as induction heating rice cookers and hot plates, which have multiple heating coils.

[0010] Here, induction heating is a method known as frequency-shift induction heating, which heats a conductor by using a magnetic field generated by passing a high-frequency current through a coil. Specifically, high-frequency current is passed through a coil to generate magnetic flux lines around it, which heat the cooking vessel from the inside through the two effects of "eddy current loss" and "hysteresis loss."

[0011] Heating due to "eddy current loss" is a phenomenon in which eddy currents generated in a conductor placed in a magnetic field are lost due to the electrical resistance within the conductor, and heating occurs due to the Joule heat generated by this loss.In other words, if the cooking container is made of a material that does not allow current to flow, "eddy current loss" does not generally occur.

[0012] Heating due to "hysteresis loss" is a phenomenon in which alternating magnetic flux, generated by passing an alternating current through a coil, is applied to an easily magnetized material (hereafter referred to as a magnetic body), causing magnetic loss, and the lost energy causes heating. Here, alternating magnetic flux is generated by passing an alternating current through a coil, and the magnitude and direction of the magnetic flux change repeatedly over time. In other words, if the cooking container is made of a material that is not easily magnetized, "hysteresis loss" will generally not occur.

[0013] As described above, induction heating cookers heat cooking vessels through the effects of "eddy current loss" and "hysteresis loss," and therefore the upper limit of the amount of heat that can be generated varies depending on the characteristics of the material of the cooking vessel.

[0014] Next, the configuration and operation of the induction heating cooker according to the first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 17. In each drawing, the same reference numerals indicate the same or corresponding parts, and redundant explanations thereof will be appropriately simplified or omitted.

[0015] First, the overall configuration of an induction heating cooker 1000 will be described with reference to FIGS. Fig. 1 is a schematic diagram showing the whole of induction heating cooker 1000 according to embodiment 1. Fig. 2 is a schematic diagram showing a heating coil of induction heating cooker 1000 according to embodiment 1. Fig. 3 is a circuit diagram of induction heating cooker 1000 according to embodiment 1.

[0016] As shown in FIG. 1, the induction heating cooker 1000 is composed of a top plate 100 on which a cooking container 2000 is placed, and a main body 200 that is arranged below the top plate 100 and contains the equipment necessary for induction heating cooking. The top plate 100 has on its upper surface a placement area display section 300 that indicates the area where the cooking container 2000 should be placed, and a notification section 400 that notifies the user of the operating status. The main body 200 has a heating section 500 that generates a magnetic field using a high-frequency current that utilizes power supplied from an external power source, thereby heating the cooking vessel 2000. Although the induction heating cooker 1000 in this embodiment has two heating areas on the left and right, the effects of the present disclosure can also be obtained with, for example, a one-burner or three-burner. Also, since the structure of the two heating devices of the induction heating cooker 1000 is basically the same, the description of this embodiment will focus on one of the heating devices, and the description of the other heating device will be omitted.

[0017] Next, the structure of the heating unit 500 disposed inside the main body 200 will be described.

[0018] FIG. 2 is a circuit diagram of the heating unit 500. As shown in FIG. The heating unit 500 is mainly composed of a DC power supply circuit 2 that converts the power supplied from an AC power supply 1 into DC current, an inverter circuit 8 that converts the DC current into AC current of a predetermined high frequency, a load circuit 14 that generates a magnetic field from the AC current of the predetermined high frequency, a control unit 19 composed of a microcomputer, and an operation unit 20 that receives instructions from the user. In the induction heating cooker of this embodiment, the heating coil 15 described below is separated into an inner heating coil 15a located inside and an outer heating coil 15b that covers the outside of the inner heating coil 15a. However, the circuit structure for supplying high-frequency current to the inner heating coil 15a and the outer heating coil 15b is the same. Therefore, in the following description, if the structures connected to the inner heating coil 15a and the outer heating coil 15b are different in structure and operation, the circuit connected to the inner heating coil 15a will be marked with an a, and the circuit connected to the outer heating coil 15b will be marked with a b. On the other hand, numbers without an a or b will describe both the circuit connected to the inner heating coil 15a and the circuit connected to the outer heating coil 15b. Also, in the drawings, regardless of the identity of structure and operation, the circuit connected to the inner heating coil 15a will be marked with an a, and the circuit connected to the outer heating coil 15b will be marked with a b.

[0019] The DC power supply circuit 2 is composed of a rectifier diode bridge 3 that rectifies AC power, a reactor 4, and a smoothing capacitor 5. The DC power converted by the DC power supply circuit 2 is supplied to an inverter circuit 8. The input power input to the inverter circuit 8 is detected by the magnitude of the input current to the inverter circuit 8 (input current value) detected by input current detection means 6 and the magnitude of the input voltage to the inverter circuit 8 (input voltage value) detected by input voltage detection means 7. As the input current detection means 6, for example, a current transformer is used.

[0020] The inverter circuit 8 is a half-bridge inverter circuit, and is composed of a high-potential side switching element (hereinafter referred to as upper switch 9) and a low-potential side switching element (hereinafter referred to as lower switch 10) connected in series between the DC buses output from the DC power supply circuit 2, an upper diode 11 connected in anti-parallel to the upper switch 9, and a lower diode 12 connected in anti-parallel to the lower switch 10. The upper switch 9 and the lower switch 10 are each boosted by a boost circuit 13 to a voltage required to drive the switch, and are alternately turned on and off to generate a high-frequency voltage.

[0021] The load circuit 14 is connected to the output point of the inverter circuit 8. The load circuit 14 is composed of a series circuit of a heating coil 15 and a resonant capacitor 16, and a clamp diode 17 connected in parallel with the resonant capacitor 16.

[0022] As will be described later, the heating coil 15 is a coiled conductor disposed below the top plate 100 on which the cooking vessel 2000 (such as a pot) to be heated is placed. 3, the heating coil 15 is composed of an inner heating coil 15a in which a conductor wire is formed into a coil shape on the inside, and an outer heating coil 15b in which a conductor wire is formed into a coil shape so as to cover the outer periphery of the inner heating coil 15a. Specifically, the outer heating coil 15b is formed approximately concentrically with the inner heating coil 15a, and is disposed outside the outer periphery of the inner heating coil 15a so as to surround the inner heating coil 15a.

[0023] Clamp diode 17 clamps the potential at the connection point between heating coil 15 and resonant capacitor 16 to the low-potential bus potential of the DC power supply. Due to the action of this clamp diode 17, the current flowing through heating coil 15 is not commutated when lower switch 10 is in the conductive state. Note that inner heating coil 15a is a heating coil that heats the center of the bottom of cooking vessel 2000, which is the object to be heated, and outer heating coil 15b is a heating coil that heats the outer periphery of the bottom of the object to be heated. The output current flowing through heating coil 15 is detected by output current detection means 18. The output current detection means 18 may be, for example, a current transformer.

[0024] The control unit 19 is configured with a microcomputer, and independently drives and controls the inverter circuits 8a and 8b, and also controls the entire induction cooking appliance 1000. Based on the heating power command set by the user on the operation unit 20, the control unit 19 uses the detected values ​​from the input current detection means 6 and the input voltage detection means 7 to control the power supplied to the heating coil 15 according to the heating power command. The power of the heating coil 15 is controlled by varying the switching frequency of the upper switch 9 and the lower switch 10. Note that a method of controlling by adjusting the duty while keeping the switching frequency of the upper switch 9 and the lower switch 10 constant may also be used in combination.

[0025] The control unit 19 also has a normal heating control for simultaneously driving the inverter circuits 8a and 8b at the same frequency, and an alternate heating control for alternately driving the inverter circuits 8a and 8b.

[0026] In normal heating control, inverter circuits 8a and 8b are driven simultaneously, so inverter circuits 8a and 8b must be driven at the same frequency. This is because, when heating coils 15 are driven at the same frequency, the magnetic flux directions of inner heating coil 15a and outer heating coil 15b are the same. However, when heating coils 15 are driven at different frequencies, the magnetic flux directions of inner heating coil 15a and outer heating coil 15b may be reversed. Here, a characteristic of heating coil 15 is that when the magnetic flux directions of inner heating coil 15a and outer heating coil 15b are reversed, the magnetic fluxes cancel each other out, resulting in reduced heating capacity. Therefore, in normal heating control, inverter circuits 8a and 8b are driven at the same frequency.

[0027] On the other hand, in the internal and external alternating heating control, the first inverter circuit 8a and the second inverter circuit 8b are alternately driven, and therefore they do not necessarily have to be driven at the same frequency.

[0028] Furthermore, since the heating capacity varies depending on the characteristics of the material of the cooking vessel as described above, the control unit 19 has a function of acquiring the characteristics of the material of the cooking vessel before cooking begins. Specifically, control unit 19 passes current through heating coil 15 at a drive frequency corresponding to the characteristics of the material of a given cooking vessel, and determines the material characteristics of cooking vessel 2000 using the magnitude of the input current (input current value) to input current detection means 6 and inverter circuit 8 at that time and the magnitude of the output current (output current value) flowing through heating coil 15 detected by output current detection means 18. In determining the characteristics, control unit 19 determines the material characteristics of the center and outer sides of cooking vessel 2000 using separate steps. Each step also determines whether the material characteristics fall into a "non-magnetic," "magnetic," or "ferromagnetic" range.

[0029] Here, the technical scope of "non-magnetic", "magnetic" and "ferromagnetic" in this embodiment will be explained.

[0030] "Nonmagnetic" refers to a range of properties that have the properties of a conductor with a certain level of electrical resistance but do not have the properties of a magnetic material. Note that not having the properties of a magnetic material means that the material does not become magnetized to a degree that allows it to be used as an induction cooker 1000, not that it does not become magnetized at all. In other words, when the induction cooker 1000 heats a cooking container 2000 with "nonmagnetic" properties, heating due to "hysteresis loss" is hardly expected, and heating occurs solely through "eddy current loss." Therefore, when the induction cooker 1000 uses a cooking container 2000 with "nonmagnetic" properties, the range of selectable heating capacities is lower and narrower than usual. Furthermore, "nonmagnetic" materials that can be used for the cooking container 2000 include copper, aluminum, brass, and nonmagnetic stainless steel. It should be noted that the induction heating cooker 1000 may not be able to use the above-mentioned "non-magnetic" materials for heating if the magnetic field generation capacity is different.

[0031] "Magnetic" refers to a range of properties that have both the properties of a conductor with a certain level of electrical resistance and the properties of a magnetic material. In other words, when the induction heating cooker 1000 heats the cooking container 2000 with "magnetic" properties, it uses both "eddy current loss" and "hysteresis loss." Therefore, the induction heating cooker 1000 has a higher and wider range of selectable heating capabilities when using a cooking container 2000 with "magnetic" properties than when using a cooking container 2000 with "non-magnetic" properties. Furthermore, examples of "magnetic" materials that can be used for the cooking container 2000 include iron.

[0032] "Ferromagnetic" basically corresponds to the above-mentioned "magnetic" characteristic, and is a characteristic range in which a cooking vessel 2000 is particularly susceptible to magnetic fields and exhibits a wide range of hysteresis curves. In other words, when a cooking vessel 2000 with "ferromagnetic" characteristics is heated at an appropriate frequency, it generates a larger "hysteresis loss" than a cooking vessel 2000 with "magnetic" characteristics, resulting in a higher heating capacity. Therefore, when heating a cooking vessel 2000 with "ferromagnetic" characteristics, the induction cooking device 1000 adjusts the frequency of the current supplied to the heating coil 15 to achieve the same heating capacity as when heating a cooking vessel 2000 with "magnetic" characteristics. Furthermore, "ferromagnetic" materials used for the cooking vessel 2000 include ferritic stainless steel, known as SUS430, which has strong magnetic properties.

[0033] Next, a description will be given of the notification unit 400 built into the main body 200. Fig. 4 is a schematic diagram of the notification unit of the induction heating cooker 1000 according to the first embodiment. The notification unit 400 notifies the user of information related to operation inputs and the operating status actually being carried out by the control unit 19, and includes the display unit 25, the thermal power lamp 26, and the audio notification unit 27. The operation of the notification unit 400 is controlled by the control unit 19.

[0034] The display unit 25 is configured as a display capable of displaying any characters or pictures, and is provided on the main body 200. The display unit 25 is configured so that it can be seen by the user through a highly transparent area provided on the top panel 100.

[0035] The heat lamp 26 indicates the heat applied to the cooking vessel 2000, and is configured with a plurality of lighting lamps 26a arranged side by side. 4 shows the heating power lamps 26 in a state where the maximum selectable heating power value is 9, and the target heating power value selected by the user and the set heating power value actually supplied to the cooking vessel 2000 are both 6. Here, nine lighting lamps 26a are provided, the same number as the maximum heating power values, and six lighting lamps 26a, starting from the left lighting lamp 26a, are lit in order according to the set heating power value to notify the user that the cooking vessel 2000 is operating at a heating power value of 6.

[0036] The voice notification unit 27 is configured with a speaker that can generate any sound, and is provided in the main body 200. The voice notification unit 27 is used to notify information set in accordance with input by the user, to notify in the event of danger, and the like.

[0037] Next, the positional relationship between the cooking vessel 2000 used in the induction heating cooker 1000 and the heating coil 15 will be described. 5 to 7 are diagrams showing the positional relationship between the cooking vessel 2000 and the heating coil 15 of the induction heating cooker 1000 according to the first embodiment.

[0038] FIG. 5 is a diagram showing a cooking vessel 2000a, called a small pot, placed on the top plate 100, the cooking vessel 2000a being approximately the same diameter as or smaller than the outer diameter of the inner heating coil 15a.

[0039] 6 is a diagram showing a cooking vessel 2000b called a large pot, which has a radius equal to or larger than the outer diameter of the outer heating coil 15b, placed on a top plate 100. The large pot cooking vessel 2000 shown here is a cooking vessel (regular pot) in which the center and outer sides of the outer bottom surface are made of the same material.

[0040] 7 shows cooking vessel 2000c, known as a composite cauldron, which is about the same size as the cauldron described above but is formed so that the central and outer sides of the vessel's outer bottom surface are made of different materials, placed on top plate 100. Cooking vessel 2000c has plate 21 attached to the central side of the vessel's outer bottom surface, made of a material that is more suitable for induction heating than the material forming the rest of the vessel. As a specific example of the material forming the cooking vessel 2000c, the plate 21 of the cooking vessel 2000c is formed from a magnetic or ferromagnetic material, and the rest of the cooking vessel 2000c is formed from a non-magnetic material that does not have magnetic properties. In other words, the cooking vessel 2000c called a composite cauldron is a vessel in which the magnetic or ferromagnetic plate 21, which is a magnetic material suitable for induction heating, is attached to the center of the bottom surface of a non-magnetic vessel that is not suitable for induction heating. In addition, there is also a cooking vessel 2000c in which the plate 21 is formed from a ferromagnetic material and the rest of the cooking vessel 2000c is formed from a magnetic material.

[0041] Next, the operation of the induction heating cooker 1000 from when it receives an instruction to start cooking from the user until it starts cooking will be described.

[0042] FIG. 8 is a control block diagram of the induction heating cooker 1000 according to the first embodiment.

[0043] As shown in Fig. 8, when a user inputs a heating power setting, such as the heating power level and whether to operate under normal heating control or alternating internal and external heating control, via operation unit 20, control unit 19 receives the information as operation input information. Then, control unit 19 controls the drive frequency of inverter circuit 8 to realize the operation input information, causing a high-frequency current to flow through heating coil 15, and heating cooking container 2000 on top plate 100 by electromagnetic induction. Control unit 19 also notifies the user of information related to the operation input information, the actual operating status, etc., using display unit 25, heating power lamp 26, and audio notification unit 27.

[0044] FIG. 9 is a flowchart showing an operation that the control unit 19 of the induction heating cooker 1000 according to the first embodiment performs before starting cooking.

[0045] When starting cooking, the user inputs desired heating power information into the operation unit 20 provided in the induction heating cooker 1000. When the induction heating cooker 1000 receives operation input information input by the user from the operation unit 20 (step S1: Yes), it carries out a characteristic determination step of determining the characteristics of the cooking container 2000 placed on the top plate 100 (step S2). When the induction heating cooker 1000 has not received operation input information input by the user from the operation unit 20 (step S1: No), the induction heating cooker 1000 waits in a standby mode in which power consumption is reduced.

[0046] In the characteristic determination step (step S2), the induction cooking device 1000 determines the characteristics of the cooking vessel 2000 using the input current value and output current value when a current of a predetermined frequency is passed through the heating coil 15. In the characteristic determination step (step S2), the characteristic of the cooking vessel 2000 is determined to be one of the following ranges: "nonmagnetic," "magnetic," "ferromagnetic," or "none." In addition, in the characteristic determination step (step S2), it is first determined whether the characteristic of the material of the cooking vessel 2000 is "nonmagnetic." This is to suppress the load on the cooking vessel 2000 caused by applying a magnetic field of a frequency lower than "magnetic" to a "nonmagnetic" material. Here, the characteristic of the cooking vessel 2000 being "none" is used as a general term to mean that the cooking vessel 2000 is made of a material that cannot generate heat by electromagnetic induction or that the cooking vessel 2000 is not present above the corresponding heating coil 15.

[0047] The characteristic determination step (step S2) is sufficient if the characteristics of the cooking container 2000 can be acquired, and may be configured to determine the shape and characteristics of the cooking container 2000 from an external database, for example, by inputting the type of cooking container 2000 to be used into a mobile terminal. Moreover, by making a determination of "none" in the characteristic determination step, the induction heating cooker 1000 can also determine a situation in which no cooking container 2000 is placed on the top plate 100 or a cooking container 2000 that is not suitable for electromagnetic induction heating is placed on the top plate 100. Furthermore, the induction heating cooker 1000 also determines the size of the cooking container 2000 and whether it is made of a different material.

[0048] Next, the induction heating cooker 1000 carries out an operating condition setting step of setting operating conditions for the heating coil based on the characteristics of the cooking vessel 2000 (step S3). In the operating condition setting step, a drive frequency that serves as an operating condition for the inverter circuit 8 is set based on the characteristics of the cooking vessel 2000 acquired in the characteristic determination step and information stored in advance in the control unit 19 in a database of induced current frequencies suitable for the characteristics of the cooking vessel 2000. The induced current frequency suitable for the characteristics is a frequency that suppresses overcurrent generated in the circuit of the control unit 19 and can efficiently heat the cooking vessel 2000. In addition, in the case of a cooking vessel 2000 having "ferromagnetic" characteristics, the frequency is adjusted to a value close to the heating amount of a "magnetic" cooking vessel 2000, as described above.

[0049] Thereafter, the induction heating cooker 1000 carries out a notification step of notifying the user of information relating to the set operating conditions using the display unit 25, the heat lamp 26 and the audio notification unit 27 (step S4).

[0050] After carrying out the notification step, the induction heating cooker 1000 drives the inverter circuit 8 under the set operating conditions to pass a high-frequency current through the heating coil 15, thereby heating the cooking vessel 2000 and starting cooking.

[0051] Next, a specific operation of the characteristic determining step (step S2) of determining the characteristic of the cooking vessel 2000 in the induction heating cooker 1000 according to the first embodiment will be described.

[0052] The characteristic determination step is a step in which magnetic fields of frequencies suited to the characteristics of the materials on the center side and the outside of cooking vessel 2000 are applied, and the characteristics are determined from the input and output current values ​​at that time. This step consists of a central characteristic determination step for determining the characteristics of the cooking vessel 2000 on the inner heating coil 15a, followed by an outer characteristic determination step for determining the characteristics of the cooking vessel 2000 on the outer heating coil 15b. In each step, it is determined whether the material of cooking vessel 2000 falls into one of the characteristic ranges of "non-magnetic," "magnetic," "ferromagnetic," or "none."

[0053] The specific operation of the determination step is as follows. First, the control unit 19 drives the inverter circuit 8 at a frequency suitable for the corresponding characteristics, and supplies a current of that frequency to the heating coil 15. At that time, the control unit 19 detects the input and output current values ​​flowing through the heating coil 15, and determines the characteristics of the cooking vessel 2000 above the corresponding heating coil 15. Here, the control unit 19 first determines whether the cooking container 2000 has the "non-magnetic" characteristic, and if not, determines whether the cooking container 2000 has the "magnetic" or "ferromagnetic" characteristic, which would make the cooking container a magnetic body. This is to avoid applying a magnetic field with a lower frequency suitable for "magnetic" or "ferromagnetic" to the cooking container 2000, which has the "non-magnetic" characteristic, and placing a load on the cooking container.

[0054] Next, a central characteristic determination step, which is performed first, for determining the characteristics of the cooking vessel 2000 on the inner heating coil 15a will be described. FIG. 10 is a flowchart of the center-side characteristic determination step of the induction heating cooker 1000 according to the first embodiment.

[0055] First, the control unit 19 determines whether the characteristic of the central side of the cooking vessel 2000 above the inner heating coil 15a is "non-magnetic" (step S201). Specifically, the control unit 19 drives the inverter circuit 8a for a short time at a nonmagnetic frequency (32 kHz) that is suitable for the "nonmagnetic" characteristics, and detects the input current to the inverter circuit 8a and the output current flowing through the inner heating coil 15a that are generated at that time. The control unit 19 determines whether the material on the center side of the cooking vessel 2000 is within the "nonmagnetic" characteristic range from the detected input current value and output current value.

[0056] If the detected input current value and output current value are within the "non-magnetic" characteristic range (step S201: Yes), the control unit 19 determines and stores the characteristics of the material on the center side of the cooking vessel 2000 as "non-magnetic" (step S202), and proceeds to an outer characteristic determination step described below, in which the characteristics of the material on the outside of the cooking vessel 2000 are determined.

[0057] On the other hand, if the detected input current value and output current value are not within the "non-magnetic" characteristic range (step S201: No), the control unit 19 determines whether the characteristic of the material on the center side of the cooking container 2000 is "magnetic" (step S203). Specifically, the control unit 19 drives the inverter circuit 8a for a short time at a magnetic frequency (28 kHz) that is suitable for the "magnetic" characteristic, and detects the input current to the inverter circuit 8a and the output current flowing through the inner heating coil 15a that are generated at that time. The control unit 19 determines whether the material on the center side of the cooking vessel 2000 is within the "magnetic" characteristic range from the detected input current value and output current value.

[0058] If the detected input current value and output current value are within the characteristic range of "magnetic" (step S203: Yes), the control unit 19 determines and stores the characteristic of the central side of the cooking vessel 2000 as "magnetic" (step S204), and proceeds to an outer characteristic determination step to determine the characteristic of the outer side of the cooking vessel 2000 above the outer heating coil 15b described below.

[0059] On the other hand, if the detected input current value and output current value are not within the characteristic range of "magnetic" (step S203: No), the control unit 19 determines whether the characteristic of the material on the center side of the cooking container 2000 is "ferromagnetic" (step S205). Specifically, the control unit 19 drives the inverter circuit 8a for a short time at a ferromagnetic frequency (24.5 kHz), which is a frequency suitable for the "ferromagnetic" characteristics, and detects the input current to the inverter circuit 8a and the output current flowing through the inner heating coil 15a that are generated at that time. The control unit 19 determines whether the material on the center side of the cooking vessel 2000 is within the "ferromagnetic" characteristic range from the detected input current value and output current value.

[0060] If the detected input current value and output current value are within the characteristic range of "ferromagnetic" (step S205: Yes), the control unit 19 determines and stores the characteristics of the material on the center side of the cooking vessel 2000 as "ferromagnetic" (step S206), and proceeds to a step of determining the characteristics of the material on the outside of the cooking vessel 2000, which will be described later.

[0061] On the other hand, if the detected input current value and output current value are not within the characteristic range of "ferromagnetic" (step S205: No), the control unit 19 determines that there is "no" cooking container 2000 on the top plate 100 that can be heated by induction heating (step 207), records the information, and then terminates the characteristic determination step.

[0062] Next, the outer characteristic determining step for determining the characteristics of the material of the cooking vessel 2000 on the outer heating coil 15b will be described. FIG. 11 is a flowchart of the outside characteristic determination step of the induction heating cooker 1000 according to the first embodiment.

[0063] First, the control unit 19 determines whether the material characteristic of the outer surface of the cooking vessel 2000 above the outer heating coil 15b is "non-magnetic" (step S208). Specifically, the control unit 19 drives the inverter circuit 8b for a short time at a nonmagnetic frequency (32 kHz) that is suitable for the "nonmagnetic" characteristics, and detects the input current to the inverter circuit 8b and the output current flowing through the outer heating coil 15b that are generated at that time. The control unit 19 determines whether the outer material of the cooking vessel 2000 is within the "nonmagnetic" characteristic range from the detected input current value and output current value.

[0064] If the detected input current value and output current value are within the characteristic range of "non-magnetic" (step S208: Yes), the control unit 19 determines and stores the characteristic of the outside of the cooking container 2000 as "non-magnetic" (step S209), and ends the characteristic determination step.

[0065] On the other hand, if the detected input current value and output current value are not within the "non-magnetic" characteristic range (step S208: No), the control unit 19 checks whether the characteristic of the material on the center side of the cooking container 2000 is "non-magnetic" (step S210). If the characteristic of the material on the center side of cooking vessel 2000 is stored as "non-magnetic" (step S210: Yes), control unit 19 determines and stores the characteristic of the material on the outside of cooking vessel 2000 as "none" (step S211), and then ends the characteristic determination step.

[0066] On the other hand, if the characteristics of the material on the center side of the cooking container 2000 are stored as other than "non-magnetic" (step S210: No), the control unit 19 determines whether the characteristics of the material on the outside of the cooking container 2000 are "magnetic" (step S212). Specifically, the control unit 19 drives the inverter circuit 8b for a short time at a magnetic frequency (28 kHz) that is suitable for the "magnetic" characteristic, and detects the input current to the inverter circuit 8b and the output current flowing through the outer heating coil 15b that are generated at that time. The control unit 19 determines whether the outer material of the cooking vessel 2000 is within the "magnetic" characteristic range from the detected input current value and output current value.

[0067] If the detected input current value and output current value are within the characteristic range of "magnetic" (step S212: Yes), control unit 19 determines and stores the characteristic of the material of the outside of cooking vessel 2000 as "magnetic" (step S213). Then, the characteristic determination step ends.

[0068] On the other hand, if the detected input current value and output current value are not within the characteristic range of "magnetic" (step S212: No), the control unit 19 checks whether the characteristic of the material on the center side of the cooking container 2000 is "magnetic" (step S214). If the characteristic of the material on the center side of cooking vessel 2000 is stored as "magnetic" (step S214: Yes), control unit 19 determines and stores the characteristic of the material on the outside of cooking vessel 2000 as "none" (step S211), and then ends the characteristic determination step.

[0069] On the other hand, if the characteristics of the material on the center side of the cooking container 2000 are stored as other than "magnetic" (step S214: No), the control unit 19 determines whether the characteristics of the material on the outside of the cooking container 2000 are "ferromagnetic" (step S215). Specifically, the control unit 19 drives the inverter circuit 8b for a short time at a ferromagnetic frequency (24.5 kHz), which is a frequency suitable for the "ferromagnetic" characteristic, and detects the input current to the inverter circuit 8b and the output current flowing through the outer heating coil 15b generated at that time. The control unit 19 determines whether the outer material of the cooking vessel 2000 is within the "ferromagnetic" characteristic range from the detected input current value and output current value.

[0070] If the detected input current value and output current value are within the characteristic range of "ferromagnetic" (step S215: Yes), control unit 19 determines and stores the characteristic of the outer material of cooking vessel 2000 as "ferromagnetic" (step S213). Then, the characteristic determination step ends.

[0071] On the other hand, if the detected input current value and output current value are not within the characteristic range of "ferromagnetic" (step S215: No), control unit 19 determines and stores the characteristic of the outer material of cooking vessel 2000 as "none" (step S211).

[0072] Here, the cooking vessel 2000 whose outer material characteristics are determined to be "none" in step S211 is either a small pot of approximately the same size as the heating coil 15a, or a composite large pot whose outer surface is formed from a material that is not suitable for induction heating.

[0073] As described above, in the characteristic determination step of the present embodiment, when determining the characteristics of cooking vessel 2000, the frequency of the applied magnetic field is applied starting from low to high. This prevents cooking vessel 2000 from being supplied with a high-frequency, high-power magnetic field that is incompatible with the characteristics of the material, thereby preventing unnecessary loads.

[0074] Next, the operating condition setting step (step S3) for setting the operating conditions of heating coil 15 based on the characteristics of cooking vessel 2000 will be described.

[0075] The operating condition setting step is a step in which a pre-stored database is used to set the drive frequency of the inverter circuit 8 so as to supply a high-frequency current to the heating coil 15 that matches the characteristics of the cooking vessel 2000. This step uses different databases for normal heating control and alternating heating control selected by the user, so each control will be explained below.

[0076] First, we will explain how to set the operating conditions for normal heating control, which is normal heating in which the inner heating coil 15a and the outer heating coil 15b are energized simultaneously. In normal heating control, either the inner heating coil 15a or the outer heating coil 15b can be operated, or the inner heating coil 15a and the outer heating coil 15b can be operated simultaneously at the same frequency. FIG. 12 is a database diagram used to set operating conditions for normal heating control of the induction heating cooker 1000 according to the first embodiment.

[0077] The control unit 19 determines which condition in the database of Fig. 12 the cooking vessel 2000 corresponds to, based on the material characteristics of the center and outer sides of the cooking vessel 2000. The control unit 19 then sets the operating condition described in the corresponding condition to the drive frequency of the inverter circuit 8. This allows the induction heating cooker 1000 to supply to the cooking vessel 2000 a magnetic field of a frequency suited to the characteristics of the cooking vessel 2000, thereby enabling the cooking vessel 2000 to be heated efficiently.

[0078] Next, a description will be given of a case where cooking container 2000 having the same material properties on the center side and the outside is used in induction heating cooker 2000. Specifically, a description will be given of the operation when cooking container 2000 having "non-magnetic" properties on the center side and the outside is heated by normal heating control. If the control unit 19 determines in the characteristic determination step that the center and outer sides of the cooking vessel 2000 have the "non-magnetic" characteristic, it determines which condition in the database of Figure 12 the cooking vessel 2000 falls under. If the control unit 19 determines that the cooking vessel 2000 falls under condition A, it sets the operating conditions specified in condition A as the drive conditions of the inverter circuit 8. Specifically, it sets the drive frequency of the inverter circuits 8a and 8b to 35 kHz. During cooking, the induction cooking device 1000 controls so that a current of 35 kHz is supplied from the inverter circuits 8a and 8b to the inner heating coil 15a and the outer heating coil 15b. When heating under normal heating control in this way, the induction heating cooker 1000 switches the drive frequency of the inverter circuit 8 in accordance with the characteristics of the material of the cooking vessel 2000, thereby heating the cooking vessel 2000 efficiently.

[0079] Next, a description will be given of a case where the cooking container 2000 having different material properties on the center side and the outside is used in the induction heating cooker 2000. Specifically, a description will be given of the operation when the cooking container 2000 having "magnetic" properties on the center side and "non-magnetic" properties on the outside is heated by normal heating control. If the control unit 19 determines in the characteristic determination step that the center side of the cooking vessel 2000 has a "magnetic" characteristic and the outer side has a "non-magnetic" characteristic, it determines which condition in the database of Figure 12 the cooking vessel 2000 corresponds to. If the control unit 19 determines that the cooking vessel 2000 falls under condition C, it sets the operating conditions described in condition C as the drive conditions of the inverter circuit 8. Specifically, it sets the drive frequency of the inverter circuit 8a to 27 kHz and the inverter circuit 8b to not be driven. During cooking, the induction cooking device 1000 supplies a current of 27 kHz from the inverter circuit 8a to the inner heating coil 15a, and controls so that no current flows from the inverter circuit 8b to the outer heating coil 15b. In this way, when using normal heating control to heat a cooking vessel 2000 in which the material properties of the center and outside are different and the outside has "non-magnetic" properties, the cooking vessel 2000 is efficiently heated by heating only the center side in accordance with the material properties of the center side, which can be heated by both "eddy current loss" and "hysteresis loss."

[0080] Here, the database used to set the operating conditions for normal heating control of the induction heating cooker 1000 of this embodiment has the following features.

[0081] If it is determined that the characteristics of the material on the center side and the outside of the cooking container 2000 are the same (conditions A, D, H), the control unit 19 sets both the inner heating coil 15a and the outer heating coil 15b to supply current of the same frequency suitable for the characteristics. Under these conditions, the induction heating cooker 1000 determines that the cooking vessel 2000 is a large pot made of a uniform material, and operates the heating coil 15 so that a magnetic field of a frequency suitable for the characteristics is supplied to both the center and outside of the cooking vessel 2000, thereby efficiently heating the cooking vessel 2000.

[0082] If the material characteristics of the center side of the cooking container 2000 are determined and the outer characteristics are determined to be "none" (conditions B, E, I), the operating conditions of the inverter circuit 8 are set so that power is not supplied to the outer heating coil 15b and only a current of a frequency appropriate for the material characteristics corresponding to the inner heating coil 15a is supplied to the inner heating coil 15a. Under these conditions, the induction heating cooker 1000 determines that the cooking container 2000 is a small pot of the same size as the inner heating coil 15a, and heats it efficiently by operating only the inner heating coil 15a on which the cooking container 2000 is placed.

[0083] If the outer material of the cooking container 2000 is determined to be "non-magnetic" and the characteristics of the material in the center are different from "non-magnetic" (conditions C and F apply), the operating conditions of the inverter circuit 8 are set so that power is not supplied to the outer heating coil 15b and a current of a frequency appropriate for the corresponding characteristics is supplied only to the inner heating coil 15a. Under these conditions, the induction cooking device 1000 determines that the cooking vessel 2000 is a composite cauldron with a base material of a "non-magnetic" material and a plate 21 made of a material suitable for induction heating attached to the center, and efficiently heats the plate 21 by supplying a magnetic field of a frequency suitable for the characteristics of the material of the plate 21. In other words, the induction cooking device 1000 sets the operating conditions of the inverter circuit 8 so that a current of a frequency suitable for the characteristics of the material of the plate 21 is supplied only to the inner heating coil 15a below the plate 21.

[0084] If the characteristics of the material on the center side of the cooking container 2000 are determined to be "ferromagnetic" and the characteristics of the material on the outside are determined to be "magnetic" (condition G applies), the inner heating coil 15a and the outer heating coil 15b are set to supply current of the same frequency suitable for "magnetism." Under these conditions, the induction heating cooker 1000 determines that the cooking vessel 2000 is a composite cauldron having a base material made of a "magnetic" material with a plate 21 having "ferromagnetic" properties attached to the center, and efficiently heats the cooking vessel 2000 by supplying a magnetic field of a frequency suitable for "magnetic" properties to both the center and the outside of the cooking vessel 2000. The reason for this is that the operating conditions set for the "magnetic" and "ferromagnetic" properties are close to each other, at "24.5 kHz" and "27 kHz," and therefore sufficient heat can be generated even when a magnetic field of a frequency suitable for "magnetic" properties is supplied to a material having "ferromagnetic" properties, and therefore the cooking vessel 2000 can be heated more efficiently under these operating conditions.

[0085] If the center side of the cooking container 2000 is determined to be "absent" (condition J applies), it is determined that a cooking container 2000 that can be heated by induction heating is not installed on the top plate 100, and the control unit 19 sets the operating conditions of the inverter circuit 8 so that power is not supplied to the heating coil 15.

[0086] Next, we will explain how to set the operating conditions for alternating heating control, which alternately energizes the inner heating coil 15a and the outer heating coil 15b. In alternating heating control, the inner heating coil 15a and the outer heating coil 15b are alternately switched to operate only one of them, so the inner heating coil 15a and the outer heating coil 15b can be operated at different frequencies. FIG. 13 is a database diagram used to set operating conditions for the alternate heating control of the induction heating cooker 1000 according to the first embodiment of the present invention.

[0087] The control unit 19 determines which condition in the database of Fig. 13 the cooking vessel 2000 corresponds to, based on the material characteristics of the center and outer sides of the cooking vessel 2000. The control unit 19 then sets the operating condition described in the corresponding condition as the drive frequency of the inverter circuit 8. This allows the induction heating cooker 1000 to supply to the cooking vessel 2000 a magnetic field of a frequency suited to the material characteristics of the cooking vessel 2000, thereby enabling the cooking vessel 2000 to be heated efficiently.

[0088] Next, a description will be given of a case where cooking container 2000 having the same material properties on the center side and the outside is used in induction heating cooker 2000. Specifically, a description will be given of the operation when cooking container 2000 having "non-magnetic" properties on the center side and the outside is heated by alternate heating control. If the control unit 19 determines in the characteristic determination step that the center and outer sides of the cooking vessel 2000 have the "non-magnetic" characteristic, it determines which condition in the database of Figure 13 the cooking vessel 2000 falls under. If the control unit 19 determines that the cooking vessel 2000 falls under condition A, it sets the operating conditions specified in condition A as the drive conditions of the inverter circuit 8. Specifically, it sets the drive frequency of the inverter circuits 8a and 8b to 35 kHz. During cooking, the induction cooking device 1000 controls so that a current of 35 kHz is alternately supplied from the inverter circuits 8a and 8b to the inner heating coil 15a and the outer heating coil 15b. When heating is performed under alternating heating control in this way, the induction heating cooker 1000 switches the drive frequency of the inverter circuit 8 in accordance with the characteristics of the material of the cooking vessel 2000, thereby heating the cooking vessel 2000 efficiently.

[0089] Next, a description will be given of a case where a cooking container 2000 having different material properties on the center side and the outside is used in the induction heating cooker 2000. Specifically, a description will be given of the operation when a cooking container 2000 having "magnetic" properties on the center side and "non-magnetic" properties on the outside is heated by alternate heating control. If the control unit 19 determines in the characteristic determination step that the center side of the cooking vessel 2000 has a "magnetic" characteristic and the outer side has a "non-magnetic" characteristic, it determines which condition in the database of FIG. 13 the cooking vessel 2000 falls under. If the control unit 19 determines that the cooking vessel 2000 falls under condition C, it sets the operating conditions described in condition C as the drive conditions of the inverter circuit 8. Specifically, it sets the drive frequency of the inverter circuit 8a to 27 kHz and the drive frequency of the inverter circuit 8b to 35 kHz. During cooking, the induction cooking device 1000 is controlled to alternately supply a 27 kHz current from the inverter circuit 8a to the inner heating coil 15a and from the inverter circuit 8b to the outer heating coil 15b. When using this alternating heating control to heat a cooking vessel 2000 in which the material characteristics of the center and outside are different, the cooking vessel 2000 is heated efficiently because it is heated with a magnetic field frequency that matches the characteristics of each material.

[0090] Note that the alternating heating control differs from the normal heating control in that, in the alternating heating control, cooking is not performed if the outer characteristic of cooking vessel 2000 is "none." In other words, in the case of cooking vessel 2000 having a size similar to that of inner heating coil 15a, alternating heating control is not performed because cooking vessel 2000 is not located above outer heating coil 15b.

[0091] Next, a specific example of notification to the user using notification unit 400 will be described. The following description is of a case where a user attempts to cook using cooking container 2000 under condition C shown in Fig. 12 under normal heating control with a target heating power value of 9.

[0092] 14 and 15 are diagrams showing the contents of notification by the display unit 25 and the audio notification unit 27 of the induction heating cooker 1000 according to the first embodiment.

[0093] As shown in Fig. 14, the induction heating cooker 1000 notifies the user of the current operating status using the display unit 25 and audio notification unit 27, which are notification unit 400. Specifically, when the cooking vessel 2000 has the structure of condition C shown in Fig. 12, the induction heating cooker 1000 of this embodiment heats the cooking vessel 2000 only with the inner heating coil 15a, and therefore the upper limit of the heat power that can be supplied is lower than that of, for example, an ordinary large pot as in condition D. Therefore, the control unit 19 notifies the user of the target heat power value (A in Fig. 14) that the user set with the operation unit 20, the type of pot in the cooking vessel 2000 (B in Fig. 14), and the restrictions imposed by using the pot in the cooking vessel 2000 (C in Fig. 14) using the display unit 25 and audio notification unit 27.

[0094] Furthermore, if the target heat value is greater than the maximum heat value that can be selected for the pot in cooking vessel 2000, control unit 19 displays on display unit 25 a message that the target heat cannot be supplied by cooking vessel 2000, along with countermeasures, and notifies via audio notification unit 27. The notification is, for example, as shown in D of Fig. 14, to prompt the user to change to a cooking vessel 2000 that can supply the target heating power value. Also, as shown in D of Fig. 15, the target heating power value input via the operation unit 20 and the set heating power value, which is the heating power value that was actually set, are displayed, and the user is notified of the corresponding measures. For example, the induction heating cooker 1000 has an automatic cooking function that automatically sets the heating power and heating time when a recipe is registered, and when cooking using the automatic cooking function, the heating power value and cooking time are automatically changed and the changes are notified to the user.

[0095] 16 and 17 are diagrams showing the contents of notification by the heat lamp 26 of the induction heating cooker 1000 according to the first embodiment.

[0096] As shown in FIG. 16, the induction heating cooker 1000 displays the actual heating power by lighting the heating power lamp 26, which is the notification unit 400, and notifies the user of it. In the induction heating cooker 1000 of this embodiment, when the cooking vessel 2000 has the structure of condition C shown in FIG. 12 , even if the user sets the target heating power value to 9, the set heating power value indicating the heating power actually supplied to the cooking vessel 2000 will be 6. Therefore, the control unit 19 operates the lighting lamps 26a so that the target heating power value and the set heating power value are displayed differently. Specifically, the control unit 19 lights all nine lighting lamps 26a corresponding to the target heating power value at a low intensity, lights the six lighting lamps 26a from the left that can be selected as the set heating power value at a higher intensity than the other three, and blinks only the sixth lighting lamp 26a from the left that corresponds to the current set heating power value. In other words, the rightmost lighting lamp 26a that is lit at a low intensity indicates the target heating power value set by the user, and the blinking lighting lamp 26a indicates the set heating power value that is the heating power currently supplied to the cooking vessel 2000.

[0097] In this way, by displaying the target heating value and the set heating value differently, the user can intuitively confirm that the heating power supplied to cooking vessel 2000 is limited, and can confirm at a glance the difference between the target heating value set by the user using operation unit 20 and the actually operating set heating value. Note that in this embodiment, a method of displaying the target heating value and the set heating value differently by varying the brightness is realized, but this method is not limited to this as long as the user can confirm the difference; for example, the color or shape of the display may be changed.

[0098] Furthermore, the induction cooking appliance 1000 can change its set heating power value during heating operation. When the control unit 19 receives an operation to change the set heating power value from the user, it flashes only the lighting lamp 26a at the location where the set heating power value is changed in response to the user's operation, as shown in Figure 17. Furthermore, the range that can be selected by this operation is controlled so that it is limited to the selection range of set heating power values ​​that are lit with high intensity, and if an operation that deviates from this selection range is received, the operation is canceled. In this way, by clearly displaying the range that the user can select, it is possible to prevent the user from mistakenly perceiving the cancellation of the user's operation as a malfunction.

[0099] Next, a specific example of alternate heating control will be described. The following description will be given of the operation when a user performs cooking using the cooking container 2000 under condition C shown in Fig. 13. Fig. 18 is a diagram showing the driving time of the inverter circuit 8 when the induction heating cooker 1000 according to embodiment 1 is operated under alternate heating control.

[0100] When performing alternating heating control using the cooking container 2000 under condition C, the control unit 19 controls the inverter circuit 8a that supplies current to the inner heating coil 15a and the inverter circuit 8b that supplies current to the outer heating coil 15b so that currents of different frequencies are alternately switched at predetermined intervals, as shown in Figure 13. Here, if there is a difference in the heating capacity by induction heating due to the material characteristics of the center and outer parts of cooking vessel 2000, control unit 19 extends the drive time of the part with the lower heating capacity by induction heating as shown in FIG. Specifically, when the center side of cooking container 2000 is made of a "magnetic" material and the outside is made of a "non-magnetic" material, control unit 19 makes the driving time of inverter circuit 8b longer than that of inverter circuit 8a so that the time spent heating the outside of cooking container 2000, which has a low heating capacity by induction heating, is longer than the time spent heating the center side of cooking container 2000, which has a high heating capacity by induction heating. In this way, by adjusting the driving times of the inverter circuits 8a and 8b, uneven heating of the object to be heated due to a difference in heating temperature between the center and outside of the cooking container 2000 can be suppressed. [Explanation of symbols]

[0101] 1 AC power supply, 2 DC power supply circuit, 3 rectifier diode bridge, 4 reactors, 5 smoothing capacitors, 6. Input current detection means; 7 input voltage detection means, 8 inverter circuits, 9 upper switch, 10 bottom switch, 11 upper diode, 12 Lower diode, 13 Boost circuit, 14 load circuit, 15 heating coils, 15a inner heating coil, 15b outer heating coil; 16 resonant capacitor, 17 Clamping diode, 18 output current detection means; 19 control section, 20 Operation section, 21 plates, 25 Display section, 26 fire lamps, 26a Lighting lamp, 27 Voice notification unit, 100 baking sheets, 200 main body, 300 placement area display unit, 400 Information Department 500 Heating section 1000 induction cooker, 2000 Cooking Containers

Claims

1. a top plate on which a cooking container is placed; An inner heating coil provided below the top plate for heating the center side of the cooking vessel; an outer heating coil provided below the top plate for heating the outside of the cooking vessel; an inverter circuit that supplies high-frequency current to the inner heating coil and the outer heating coil; a control unit that controls the inverter circuit; a notification unit that notifies a user of an operating status of the control unit; Equipped with The control unit a characteristic acquisition step of acquiring characteristics of the material of the center side and the outer side of the bottom surface of the cooking vessel; an operating condition determination step of setting the frequency of the high-frequency current supplied to the inner heating coil and the outer heating coil according to the characteristics of the material of the cooking vessel; and The control unit When the cooking vessel has different material properties on the center and outside of the bottom surface, and the material property of the outside of the bottom surface is "non-magnetic," and is used under normal heating control in which high-frequency currents of the same frequency are supplied to the inner heating coil and the outer heating coil, a high-frequency current of a frequency suitable for the material property of the center of the cooking vessel is supplied to the inner heating coil, and the supply of high-frequency current to the outer heating coil is stopped; The notification unit When a cooking vessel has different material properties on the center and outside of the bottom surface, and the material property of the outside of the bottom surface is "non-magnetic," and the cooking vessel is used under normal heating control in which high-frequency currents of the same frequency are supplied to the inner heating coil and the outer heating coil, the system notifies the user that the heating capacity of the cooking vessel is decreasing. Induction heating cooker.

2. The control unit When the cooking vessel has different material properties on the center and outer sides of the bottom surface, and the outer side of the bottom surface has a "magnetic" material property, and is used under normal heating control in which high-frequency currents of the same frequency are supplied to the inner heating coil and the outer heating coil, high-frequency currents of a frequency suitable for the "magnetic" property are supplied to the inner heating coil and the outer heating coil. The induction heating cooker according to claim 1 .

3. The notification unit notifies the user of the maximum heating power value when the heating capacity is reduced.

3. The induction heating cooker according to claim 1 or 2.

4. The notification unit notifies information about cooking time required when cooking is continued in a state where the heating capacity is reduced.

3. The induction heating cooker according to claim 1 or 2.

5. The notification unit notifies information indicating that the characteristics of the material on the center side and the material on the outside of the cooking container are different.

3. The induction heating cooker according to claim 1 or 2.

6. The control unit When the cooking vessel has different material characteristics on the center and outside of the bottom surface, and is used under alternating heating control in which high-frequency current is supplied alternately to the inner heating coil and the outer heating coil, a high-frequency current of a frequency suitable for the material characteristics on the center side of the cooking vessel is supplied to the inner heating coil, and a high-frequency current of a frequency suitable for the material characteristics on the outside of the cooking vessel is supplied to the outer heating coil. The induction heating cooker according to claim 1 .

7. The control unit The time for supplying high frequency current to the outer heating coil, whose heating capacity by induction heating has been reduced due to the characteristics of the material of the cooking vessel, is made longer than the time for supplying high frequency current to the inner heating coil.

7. The induction heating cooker according to claim 6.

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