Induction cooker

Abstract

To obtain an induction heating cooker by which it is possible to determine, by a user whether a factor of impossibility of heating is a failure of an electric circuit in an early period.SOLUTION: An induction heating cooker includes: a heating coil that heats a cooking container; a control part that controls operation of an inverter circuit for supplying a high frequency current to the heating coil; input current detection means of detecting an input current value to the inverter circuit; coil current detection means of detecting the coil current value; and a display part. The control part makes the display part display a determination result by determining whether, after power conduction start to the heating coil, a failure of an electric circuit occurs on the basis of determination whether the input current value is less than a first threshold value and the coil current value is less than a second threshold value, and determining whether the cooking container is not arranged onto the heating coil, a size of the cooking container is not adopted to a size of the heating coil or a material of the cooking container is not adopted to the heating on the basis of the determination whether the input current value is belonged to a first range larger than the first threshold value, and the coil current value is belonged to a second range larger than a second threshold value.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure relates to an induction cooker including a heating coil.

Background Art

[0002] As a conventional induction cooker, there is known one that detects an input current value flowing through an inverter circuit and an output current value flowing through a heating coil, and uses the input current value and the output current value to determine the presence or absence of a cooking container to be heated and the appropriateness of the material (see, for example, Patent Document 1).

[0003] The induction cooker disclosed in Patent Document 1 has an internal heating coil disposed below a top plate on which a cooking container is placed, and an external heating coil disposed outside the internal heating coil. This induction cooker determines the material of a cooking container located above the internal heating coil at the time of initial load detection before the start of cooking, determines the presence or absence or material of a cooking container located above the external heating coil, and controls the inverter circuit of each heating coil according to these determination results. Thereby, it is possible to suppress an excessive current from flowing through the switching element of the inverter circuit and improve the safety of the circuit.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when the electric circuit inside the main body of the induction heating cooker disclosed in Patent Document 1 fails, it is impossible to detect values suitable for determining the presence or absence and material of the cooking container for the input current value flowing through the inverter circuit and the output current value flowing through the heating coil. Therefore, the induction heating cooker erroneously determines the presence or absence and material of the cooking container, cannot appropriately control the inverter circuit, and notifies the user that the heating control has stopped. In this case, there has been a problem that the user cannot immediately determine whether the cause of the heating stop is a failure of the main body or inappropriate usage method, and it takes time to determine the cause.

[0006] The present disclosure has been made to solve the above problems, and provides an induction heating cooker that enables a user to quickly determine whether the cause of the inability to heat is a failure of the electric circuit.

Means for Solving the Problems

[0007] The induction heating cooker according to the present disclosure includes a top plate on which a cooking container for accommodating an object to be heated is placed, a heating coil provided below the top plate for heating the cooking container, an inverter circuit for supplying a high-frequency current to the heating coil, a control unit for controlling the operation of the inverter circuit, an input current detection means for detecting an input current value which is a value of the current input to the inverter circuit, a coil current detection means for detecting a coil current value which is the current input to the heating coil, and a display unit for displaying information. The control unit, after starting energization of the heating coil, determines whether a failure has occurred in the electric circuit including the inverter circuit based on whether the input current value detected by the input current detection means is less than a predetermined first threshold value and whether the coil current value detected by the coil current detection means is less than a predetermined second threshold value. The control unit also makes a second determination to determine whether the cooking container is not placed on the heating coil, whether the size of the cooking container does not match the size of the heating coil, or whether the material of the cooking container is not suitable for heating based on a determination of whether the input current value belongs to a predetermined first range greater than the first threshold value and whether the coil current value belongs to a predetermined second range greater than the second threshold value. The control unit has display control means for causing the display unit to display the determination results of the first determination means and the second determination means. information indicating that the determination is in progress until it is determined It has and the first determination means repeatedly makes a first determination of whether or not the input current value is less than the first threshold value and the coil current value is less than the second threshold value from the start of energization of the heating coil, counts the number of times the input current value is less than the first threshold value and the coil current value is less than the second threshold value, and determines that the failure determination of the electric circuit is in progress when the continuously counted number of times is 1 or more and less than a predetermined first specified number of times, and determines that a failure has occurred in the electric circuit when the continuously counted number of times is greater than the first specified number of times. The second determination means repeatedly makes a second determination of whether or not the input current value belongs to the first range and the coil current value belongs to the second range from the start of energization of the heating coil, counts the number of times the input current value does not belong to the first range and the number of times the coil current value does not belong to the second range, or measures the time from the start of energization, and determines that the determination of the user's usage method is in progress when the continuously counted number of times is 1 or more and less than a predetermined second specified number of times, or when the measured time is less than or equal to a predetermined specified time, and determines that the user's usage method is inappropriate when the continuously counted number of times is greater than the second specified number of times, or when the measured time is greater than the specified time. The display control means makes the display state of the display unit different between the case where the first determination means determines that a failure has occurred in the electric circuit and the case where the second determination means determines that the user's usage method is inappropriate. such features.

Advantages of the Invention

[0008] According to the present disclosure, after starting energization of the heating coil, based on the input current value input to the inverter circuit and the coil current value input to the heating coil, a determination is made as to whether a failure has occurred in the electric circuit and whether the user's usage method is appropriate, and the determination results are displayed on the display unit. By referring to the determination results displayed on the display unit, the user can understand whether it is a failure of the electric circuit, whether the usage method is inappropriate, or for what reason heating cannot be performed, and can shorten the time until the cause is determined.

Brief Description of the Drawings

[0009]

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Best Mode for Carrying Out the Invention

[0010] Hereinafter, the induction heating cooker according to the present disclosure will be described with reference to the drawings. The cooker shown in the drawings shows an example of a device to which the induction heating cooker of the present disclosure is applied, and the induction heating cooker of the present disclosure is not limited by the induction heating cooker shown in the drawings. Further, in the following description, terms representing directions are appropriately used for ease of understanding. Terms representing directions are, for example, "up", "down", "right", "left", "front", and "rear" based on the position where the user stands when using the cooker. Also, in some of the drawings, for convenience of explanation, three axes of the X-axis, Y-axis, and Z-axis that define the direction are shown in the figure. These terms indicating directions and the three axes are for explaining the configuration of the cooker and do not limit the direction of the induction heating cooker of the present disclosure. Furthermore, in each figure, those with the same reference numerals are the same or corresponding thereto, and are common throughout the entire text of the specification.

[0011] Embodiment 1. The configuration of the induction heating cooker 1 of Embodiment 1 will be described. FIG. 1 is an external perspective view showing an installation example of the induction heating cooker 1 according to Embodiment 1. FIG. 2 is a perspective schematic view when the induction heating cooker 1 shown in FIG. 1 is viewed from the side.

[0012] The induction heating cooker 1 of Embodiment 1 is a heating cooker called an IH (Induction Heating) cooking heater. In the installation example shown in FIG. 1, the induction heating cooker 1 is a built-in type IH cooking heater that is incorporated and used in a kitchen furniture 2 having a cooking table on the upper part. The induction heating cooker 1 has a main body 3 and a top plate 4 installed on the main body 3. The top plate 4 is exposed on the kitchen top plate that constitutes the top surface of the kitchen furniture 2.

[0013] The top plate 4 is composed of, for example, a heat-resistant glass plate and a metal frame attached to the periphery of the glass plate. Further, the top plate 4 is fixed in a watertight state via a rubber packing or a sealing material between the outer periphery of the upper surface opening of the main body 3 of the induction heating cooker 1. On the upper surface of the top plate 4, two heating ports, a left heating port 5a and a right heating port 5b, are provided. The left heating port 5a and the right heating port 5b indicate the area where a cooking container such as a pot or a frying pan is placed. An exhaust port cover 6 is provided on the back side of the top plate 4. The exhaust port cover 6 is composed of a perforated metal or a lattice-shaped metal member having air permeability, has air permeability, and has little air flow resistance. The perforated metal is a metal plate in which through holes are formed with a press mold. The exhaust from the induction heating cooker 1 passes through the exhaust port cover 6 and flows out of the induction heating cooker 1.

[0014] On the front surface of the main body 3 of the induction heating cooker 1, a heating door 8 for opening and closing the front surface of the heating chamber 7 disposed inside the main body 3 is provided. The heating door 8 is provided with a handle 9 for opening and closing the heating door 8.

[0015] As shown in FIG. 2, a right heating coil 10b is provided below the right heating port 5b. A left heating coil 10a (see FIG. 3) is provided below the left heating port 5a shown in FIG. 1. These heating coils are, for example, heating coils in which a conductor such as a copper wire or an aluminum wire is wound in a spiral shape and processed so that the outer periphery becomes circular. When a high-frequency current is supplied to the left heating coil 10a and the right heating coil 10b, a high-frequency magnetic field is generated. Thereby, the cooking container placed on the left heating port 5a and the right heating port 5b is induction-heated.

[0016] Inside the main body 3, below the left heating coil 10a and the right heating coil 10b, a heating chamber 7 is provided. The heating chamber 7 is a device for heating the food in the cooking container accommodated in the heating chamber 7. An opening for taking in and out the cooking container is formed on the front surface of the heating chamber 7. The opening of the heating chamber 5 is covered by a heating door 8 so as to be openable and closable. The heating door 8 is rotatably supported by the main body 3 with a hinge and an arm (not shown). Thus, the heating door 8 is configured to open forward with the lower end as the fulcrum of the rotation center. Note that the heating door 8 may be configured to be pulled out integrally with a support member that supports the cooking container from below by a slide rail.

[0017] An opening / closing detection unit 11 for detecting the opening and closing of the heating door 8 is provided on the heating door 8. The opening / closing detection unit 11 is, for example, a microswitch or an infrared sensor. Behind the heating chamber 7, microwave heating means 12 for heating the food in the cooking container accommodated in the heating chamber 7 is provided. The microwave heating means 12 performs so-called range heating to heat the food placed in the heating chamber 7 by irradiating microwaves into the heating chamber 7.

[0018] In addition, upper radiant heat heating means 13c and lower radiant heat heating means 13d for performing so-called heater heating on the food from above and below are provided in the heating chamber 7. The upper radiant heat heating means 13c is arranged on the ceiling surface inside the heating chamber 7, and the lower radiant heat heating means 13d is arranged on the floor surface inside the heating chamber 7. Each of the upper radiant heat heating means 13c and the lower radiant heat heating means 13d is a sheathed heater.

[0019] In addition, a non-contact temperature sensor for detecting the temperature of the food in the heating chamber 7 in a non-contact manner is provided in the heating chamber 7. The non-contact temperature sensor is, for example, an infrared sensor 14. The temperature range detected by the infrared sensor 14 is set to, for example, -20°C to 100°C. Thus, the infrared sensor 14 can accurately detect the degree of heating of the food in real time, for example, in 1°C increments.

[0020] In addition, the heating chamber 7 is provided with an indoor temperature sensor for detecting the ambient temperature inside the heating chamber 7 or the wall surface temperature of the heating chamber 7. The indoor temperature sensor is, for example, a thermistor sensor 15. Since the thermistor sensor 15 captures the change in temperature as a change in electrical resistance to detect the temperature, the upper limit value of the detectable temperature is about 250°C.

[0021] (Operation unit and display unit) FIG. 3 is a top view of the induction heating cooker 1 shown in FIG. 1. As shown in FIG. 3, an operation unit 16 for the user to operate the induction heating cooker 1 and a display unit 17 for displaying information to the user are provided on the upper surface of the top plate 4 of the induction heating cooker 1. The operation unit 16 includes a left operation unit 16a, a right operation unit 16b, and a central operation unit 16e. The display unit 17 includes a left display unit 17a, a right display unit 17b, and a central display unit 17e, and a left heating power display unit 18a and a right heating power display unit 18b.

[0022] As shown in FIG. 3, a left operation unit 16a, a central operation unit 16e, and a right operation unit 16b are arranged on the front side of the upper surface of the top plate 4. A left heating power display unit 18a is arranged on the back side of the left operation unit 16a, and a right heating power display unit 18b is arranged on the back side of the right operation unit 16b. Further, a left display unit 17a is arranged on the back side of the left heating power display unit 18a. A central display unit 17e is arranged on the back side of the central operation unit 16e. A right display unit 17b is arranged on the back side of the right heating power display unit 18b.

[0023] In addition, a main power key 19 is provided at a position adjacent to the right operation unit 16b. The main power key 19 is a key operated when turning on or off the main power of the induction heating cooker 1. When the main power of the induction heating cooker 1 is off and the main power key 19 is pressed by the user for, for example, several tens of seconds, the main power turns on. Also, when the main power of the induction heating cooker 1 is on and the main power key 19 is pressed by the user for, for example, several tens of seconds, the main power turns off.

[0024] Figure 4 is an enlarged view of the left display unit 17a, the left heating power display unit 18a, and the left operation unit 16a shown in Figure 3. The left display unit 17a displays information related to cooking in the left heating port 5a, and is composed of, for example, a liquid crystal display. Specifically, the left display unit 17a displays the set time for timer cooking for the food placed on the left heating port 5a, the elapsed time since the operation in the left heating port 5a started, or the remaining time until the set time for timer cooking ends. Further, when preheating cooking in the left heating port 5a is selected, the left display unit 17a automatically displays the preset temperature or the current temperature. The preset temperature is referred to as the initial set temperature.

[0025] The left heating power display unit 18a is composed of a plurality of LEDs (Light Emitting Diodes) and displays the heating power of the left heating port 5a in a plurality of stages. The left heating power display unit 18a expresses the heating power by switching the lighting state of the plurality of LEDs or switching the lighting color. The lighting state is, for example, lighting, extinguishing, or blinking. Thereby, it is possible to provide the user with a direct and easy-to-understand heating power notification.

[0026] The left operation unit 16a is for the user to input operations related to heating cooking in the left heating port 5a. As shown in Figure 4, the left operation unit 16a includes five input keys 20a, 21a, 22a, 23a, and 24a. The input keys 20a, 21a, 22a, 23a, and 24a are, for example, capacitance-type touch sensors that can be input using the change in capacitance when the user lightly touches them with a finger or the like. Further, a light emitting unit 25a is provided corresponding to the positions of the respective input keys of the input keys 20a, 21a, 22a, 23a, and 24a. The light emitting unit 25a is composed of LEDs and emits light according to the operations of the input keys 20a, 21a, 22a, 23a, and 24a.

[0027] The input key 20a is a key that is operated when selecting timer cooking at the left heating port 5a. Timer cooking is a cooking method in which the user sets the cooking time and performs an induction heating operation only for the set time. The input key 21a is a key that is operated when selecting a cooking menu to be performed at the left heating port 5a. Each time the input key 21a is pressed, one of a plurality of cooking menus can be selected. The cooking menus are, for example, boiling water, stewing, fried foods (automatic cooking), etc. For each cooking menu, the driving time, heating power, or driving pattern of the left heating coil 10a is different.

[0028] The input key 22a is a key that is operated to start or stop the heating cooking at the left heating port 5a. That is, when the input key 22a is pressed, the left heating coil 10a disposed below the left heating port 5a is driven. When the input key 22a is pressed while the left heating coil 10a is being driven, the driving of the left heating coil 10a is stopped and the heating is stopped.

[0029] The input keys 23a and 24a are keys that are operated when specifying the heating power during heating cooking at the left heating port 5a. By pressing the input key 23a, the heating power is decreased step by step, and by pressing the input key 24a, the heating power is increased step by step.

[0030] FIG. 5 is an enlarged view of the right display unit 17b, the right heating power display unit 18b, and the right operation unit 16b shown in FIG. 3. The right display unit 17b displays information related to heating cooking at the right heating port 5b, and is composed of, for example, a liquid crystal display. The information related to heating cooking at the right heating port 5b displayed on the right display unit 17b is the same as the information related to heating cooking at the left heating port 5a.

[0031] The right heating power display unit 18b is composed of a plurality of LEDs and displays the heating power of the right heating port 5b in multiple steps. The right heating power display unit 18b expresses the heating power by switching the lighting state or the lighting color of the plurality of LEDs in the same manner as the left heating power display unit 18a. The lighting state is, for example, lighting, extinguishing, or blinking.

[0032] The right operation unit 16b is for the user to input operations related to cooking by heating at the right heating port 5b. As shown in FIG. 5, the right operation unit 16b includes five input keys 20b, 21b, 22b, 23b, and 24b. The input keys 20b, 21b, 22b, 23b, and 24b are capacitance-type touch sensors that can be input, for example, by using the change in capacitance when the user lightly touches them with a finger or the like. Also, corresponding to the input keys 20b, 21b, 22b, 23b, and 24b, a light-emitting unit 25b is provided. The light-emitting unit 25b is an LED and emits light according to the operations of the input keys 20b, 21b, 22b, 23b, and 24b.

[0033] The input key 20b is a key that is operated when selecting timer cooking at the right heating port 5b. The input key 21b is a key that is operated when selecting a cooking menu to be performed at the right heating port 5b. The input key 22b is a key that is operated to start or stop cooking by heating at the right heating port 5b. The input keys 23b and 24b are keys that are operated when specifying the heating power during cooking by heating at the right heating port 5b. By pressing the input key 23b, the heating power is decreased step by step, and by pressing the input key 24b, the heating power is increased step by step.

[0034] FIG. 6 is an enlarged view of the central display unit 17e and the central operation unit 16e shown in FIG. 3. The central display unit 17e displays information and warnings about the entire induction heating cooker 1 and is composed of a liquid crystal display. The central display unit 17e displays the selection results of the left heating coil 10a, the right heating coil 10b, the microwave heating means 12, the upper radiant heat heating means 13c, and the lower radiant heat heating means 13d. Further, the central display unit 17e displays the operating states of the respective heating means of the left heating coil 10a, the right heating coil 10b, the microwave heating means 12, the upper radiant heat heating means 13c, and the lower radiant heat heating means 13d, caution information regarding cooking by each heating means, or warning information. Although the central display unit 17e is a single liquid crystal display in terms of hardware, it has three display areas: a first display area 26, a second display area 27, and a third display area 28, as shown in FIG. 6. The central display unit 17e can also perform different displays for each of the display areas of the first display area 26, the second display area 27, and the third display area 28.

[0035] The central operation unit 16e mainly inputs operations related to cooking in the heating chamber 7. As shown in FIG. 6, the central operation unit 16e includes nine input keys 29, 30, 31, 32, 33, 34, 35, 36, and 37. The input keys 29, 30, 31, 32, 33, 34, 35, 36, and 37 are, for example, capacitance-type touch sensors that can be input by utilizing changes in capacitance when the user lightly touches them with a finger or the like. Further, corresponding to the input keys 29, 30, 31, 32, 33, 34, 35, 36, and 37, a light emitting unit 25e is provided. The light emitting unit 25e is composed of LEDs and emits light according to the operations of the input keys 29, 30, 31, 32, 33, 34, 35, 36, and 37.

[0036] The input key 29 is a key operated to start cooking in the heating chamber 7, and the input key 30 is a key operated to stop or end cooking in the heating chamber 7. The input key 31 is a key operated when displaying the cooking menu to be executed in the heating chamber 7 on the central display unit 17e.

[0037] The input keys 32 and 33 are arranged adjacent to the first display area 26 of the central display unit 17e, and are keys for switching the image displayed in the first display area 26 of the central display unit 17e. Here, an example of switching of the image displayed in the first display area 26 will be described.

[0038] FIG. 7 is a diagram showing an image example of the three display areas shown in FIG. 6. In the image example shown in FIG. 7, when the input key 32 is operated, "Range Manual" displayed in the first display area 26 moves forward, and "Warm" displayed on the rear side is displayed in the center. Further, when the input key 33 is operated, "Range Manual" displayed in the first display area 26 moves backward, and "Boil Leafy Vegetables" displayed on the front side is displayed in the center. The user can select the cooking menu to be performed in the heating chamber 7 by operating the input keys 32 and 33. Then, when the input key 29 is operated, the cooking menu displayed in the center is executed.

[0039] As shown in FIG. 6, the input keys 34 and 35 are arranged adjacent to the second display area 27 of the central display unit 17e. The input keys 34 and 35 are keys for switching the screen displayed in the second display area 27 of the central display unit 17e. Referring to the image example of FIG. 7, when the input key 34 is operated, the wattage displayed in the second display area 27 decreases by one step. When the input key 35 is operated, the wattage displayed in the second display area 27 increases by one step. The user can select the wattage of the range cooking to be performed in the heating chamber 7 from a plurality of types of wattages by operating the input keys 34 and 35.

[0040] As shown in FIG. 6, the input keys 36 and 37 are arranged adjacent to the third display area 28 of the central display unit 17e. The input keys 36 and 37 are keys for switching the screen displayed in the third display area 28 of the central display unit 17e. Referring to the image example of FIG. 7, when the input key 36 is operated, the time displayed in the third display area 28 increases by one step. When the input key 37 is operated, the time displayed in the third display area 28 decreases by one step. The user can select the range cooking time to be performed in the heating chamber 7 by operating the input keys 36 and 37.

[0041] (Electrical Circuit) Next, the configuration of the electrical circuit of the induction heating cooker 1 will be described. FIG. 8 is a diagram showing a configuration example of the electrical circuit of the induction heating cooker 1 according to Embodiment 1. Among the plurality of heating units, the circuit configurations of the left heating coil 10a and the right heating coil 10b are the same. Therefore, in Embodiment 1 of the present invention, the circuit configuration related to the energization control of the left heating coil 10a will be described, and the description of the circuit configuration of the right heating coil 10b will be omitted. Further, among the plurality of heating units, since the heating chamber 7 is not the object to which the determination method of Embodiment 1 is applied, the description of the circuit configuration of the heating chamber 7 will be omitted.

[0042] The induction heating cooker 1 is connected to an AC power supply 38. As shown in FIG. 8, the induction heating cooker 1 includes a DC power supply circuit 39 connected to the AC power supply 38, an inverter circuit 40, a drive circuit 48, a load circuit 49, a control unit 53, an input current detection means 44, an input voltage detection means 45, and a coil current detection means 52. The operation unit 16 is connected to the control unit 53.

[0043] The DC power supply circuit 39 converts the AC power supplied from the AC power supply 38 into DC power and supplies the DC power to the inverter circuit 40. The DC power supply circuit 39 includes a rectifier diode bridge 41 that rectifies the AC power into DC power, a reactor 42 that smooths the change in current, and a smoothing capacitor 43 that smooths the change in voltage. The DC power converted by the DC power supply circuit 39 is supplied to the inverter circuit 40.

[0044] The input current detection means 44 is provided in the wiring connecting the AC power supply 38 and the DC power supply circuit 39. The input current detection means 44 detects the input current value Ib which is the current input to the inverter circuit 40. As the input current detection means 44, for example, a current transformer is used. The input voltage detection means 45 is connected to two DC buses to which DC power is supplied to the inverter circuit 40 in the DC power supply circuit 39. The input voltage detection means 45 detects the input voltage value Vb which is the voltage applied between the DC buses of the inverter circuit 40. The input power P supplied to the inverter circuit 40 is calculated by the input current value Ib detected by the input current detection means 44 and the input voltage value Vb detected by the input voltage detection means 45.

[0045] The inverter circuit 40 is, for example, a half-bridge inverter circuit as shown in FIG. 8. The inverter circuit 40 has two switching elements connected in series between the DC buses output from the DC power supply circuit 39. Among the two switching elements, the high-potential side switching element is referred to as the upper switch 46c, and the low-potential side switching element is referred to as the lower switch 46d. An upper diode 47c is connected in anti-parallel to the upper switch 46c. A lower diode 47d is connected in anti-parallel to the lower switch 46d. Each switch of the upper switch 46c and the lower switch 46d is alternately switched between the on state and the off state by the drive circuit 48 to generate a high-frequency voltage.

[0046] The load circuit 49 is connected to the output point of the inverter circuit 40. The load circuit 49 has a series circuit in which the left heating coil 10a and the resonance capacitor 50 are connected in series, and a clamp diode 51 connected in parallel to the resonance capacitor 50. The coil current detection means 52 is provided in the series circuit to which the left heating coil 10a and the resonance capacitor 50 are connected. The coil current detection means 52 detects the coil current value Ic which is the current input to the left heating coil 10a. As the coil current detection means 52, for example, a current transformer is used.

[0047] The clamping diode 51 clamps the connection potential between the left heating coil 10a and the resonance capacitor 50 to the low-potential side bus potential of the DC power supply. Due to the function of this clamping diode 51, when the lower switch 46d is conducting, the current flowing through the left heating coil 10a does not commutate.

[0048] Next, the configuration of the control unit 53 will be described. The control unit 53 controls the entire induction heating cooker 1. The control unit 53 is, for example, a microcomputer. The control unit 53 includes a memory (not shown) that stores programs, and a processor (not shown) such as a CPU (Central Processing Unit) that executes processing according to the programs. The memory (not shown) provided in the control unit 53 stores a plurality of types of programs used for controlling the induction heating cooker 1, parameters used in various programs, and data of images displayed on the display unit 17 including the central display unit 17e.

[0049] FIG. 9 is a functional block diagram showing a configuration example of the control unit 53 of the induction heating cooker 1 according to Embodiment 1. The control unit 53 includes a first determination means 61, a second determination means 62, a material determination means 63, a heating control means 64, a display control means 65, an audio control means 66, and a timer 67 that measures time.

[0050] The control unit 53 is mounted, for example, on an electronic circuit board (not shown) on which electronic components such as a control circuit that controls the operations of each part constituting the induction heating cooker 1 are mounted. Here, the case of heating control using the left heating coil 10a will be described, and a detailed description of the case of heating control using the right heating coil 10b will be omitted.

[0051] When the energization of the left heating coil 10a is started, the first determination means 61 determines the presence or absence of a failure in the electric circuit based on the input current value Ib detected by the input current detection means 44 and the coil current value Ic detected by the coil current detection means 52. This determination is referred to as the first determination. A failure in the electric circuit means, for example, a state in which a failure occurs in an electric circuit including at least the inverter circuit 40, such as the electric circuit shown in FIG. 8, and induction heating using the left heating coil 10a cannot be performed.

[0052] When the energization of the left heating coil 10a is started, the second determination means 62 determines whether the user's usage method is appropriate based on the input current value Ib detected by the input current detection means 44 and the coil current value Ic detected by the coil current detection means 52. This determination is referred to as the second determination. Appropriate usage means, for example, that the cooking container is placed on the left heating port 5a of the top plate 4, that the material of the cooking container placed on the left heating port 5a is a material suitable for induction heating, and that the size of the cooking container placed on the left heating port 5a matches the size of the left heating coil 10a. The size of the cooking container is the area of the surface of the cooking container that contacts the top plate 4, or the diameter of the circle if the surface of the cooking container that contacts the top plate 4 is circular. The size of the left heating coil 10a is the area of the surface facing the top plate 4, or the diameter of the circular coil.

[0053] When there is no failure in the electric circuit and the cooking container is placed on the left heating port 5a of the top plate 4, the material determination means 63 determines the material of the cooking container. The result of the material determination is reflected in the heating control executed by the heating control means 64.

[0054] The determination methods of the first determination means 61, the second determination means 62, and the material determination means 63 will be described with reference to FIG. 10. FIG. 10 is a diagram for explaining the method by which the control unit 53 determines the presence and material of the cooking container. The horizontal axis in FIG. 10 indicates the input current value Ib detected by the input current detection means 44, and the vertical axis in FIG. 10 indicates the coil current value Ic detected by the coil current detection means 52. A memory (not shown) provided in the control unit 53 stores the information of the graph shown in FIG. 10.

[0055] The case where there is no load with no cooking container placed on the left heating port 5a is referred to as "no container". Further, the case where a cooking container made of a metal material not suitable for induction heating and difficult to heat is placed on the left heating port 5a is referred to as "inappropriate container". The metal materials not suitable for induction heating are, for example, aluminum or copper. The case where a cooking container made of a magnetic metal or the like suitable for induction heating and easy to heat is placed on the left heating port 5a is referred to as "appropriate container".

[0056] As shown in FIG. 10, the range specified by the input current value Ib and the coil current value Ic is divided into a first region AR11 and a second region AR12. The second region AR12 is divided into a third region AR13 and a fourth region AR14. That is, among the entire range specified by the input current value Ib and the coil current value Ic shown in FIG. 10, the remaining region excluding the first region AR11 and the third region AR13 becomes the fourth region AR14. The first region AR11 is the range of the input current value Ib and the coil current value Ic when the electric circuit fails. The fourth region AR14 is the range of the input current value Ib and the coil current value Ic in the case of "no container" or "inappropriate container". The third region AR13 is the range of the input current value Ib and the coil current value Ic in the case of "appropriate container".

[0057] The third region AR13 is divided into three material type regions, namely material type regions AR31 to AR33, according to the difference in the material of the cooking container. The material type region AR31 is the range of the input current value Ib and the coil current value Ic when the material of the cooking container is non-magnetic. The material type region AR32 is the range of the input current value Ib and the coil current value Ic when the material of the cooking container is magnetic. The material type region AR23 is the range of the input current value Ib and the coil current value Ic when the material of the cooking container is ferromagnetic.

[0058] In FIG. 10, the first determination means 61 determines whether the input current value Ib detected by the input current detection means 44 and the coil current value Ic detected by the coil current detection means 52 belong to the first region AR11. As a result of the determination, if the detected input current value Ib and coil current value Ic belong to the first region AR11, the first determination means 61 determines that the electric circuit has failed.

[0059] In FIG. 10, the second determination means 62 determines whether the input current value Ib detected by the input current detection means 44 and the coil current value Ic detected by the coil current detection means 52 belong to the third region AR13 or the fourth region AR14. As a result of the determination, if the detected input current value Ib and coil current value Ic belong to the third region AR13, the second determination means 62 determines that the cooking container corresponds to an "appropriate container", the cooking container is suitable for heating, and the user's usage method is appropriate. On the other hand, if the detected input current value Ib and coil current value Ic belong to the fourth region AR14, the second determination means 62 determines that there is "no container" or the cooking container corresponds to an "inappropriate container", and the user's usage method is inappropriate.

[0060] Since the heating method changes depending on the material of the cookware that can be heated in FIG. 10, the material determination means 63 determines to change the control according to which of the material type regions AR31 to AR33 the input current value Ib detected by the input current detection means 44 and the coil current value Ic detected by the coil current detection means 52 belong to. As a result of the determination, when the detected input current value Ib and coil current value Ic belong to the material type region AR31, the material determination means 63 determines that the material of the cookware is non-magnetic. When the detected input current value Ib and coil current value Ic belong to the material type region AR32, the material determination means 63 determines that the material of the cookware is magnetic. When the detected input current value Ib and coil current value Ic belong to the material type region AR33, the material determination means 63 determines that the material of the cookware is ferromagnetic.

[0061] The heating control means 64 controls the left heating coil 10a, the right heating coil 10b, the microwave heating means 12, the lower radiant heat heating means 13d, and the upper radiant heat heating means 13c. Specifically, the heating control means 64 controls the energization of the left heating coil 10a via the drive circuit 48 and the inverter circuit 40 based on the operation by the user of the left operation unit 16a and the temperature of the cookware on the top plate 4. The heating control means 64 controls the energization of the right heating coil 10b via the drive circuit 48 and the inverter circuit 40 based on the operation by the user of the right operation unit 16b and the temperature of the cookware on the top plate 4. Further, the heating control means 64 controls the microwave heating means 12 based on the operation of the central operation unit 16e and the detection values of the infrared sensor 14 and the thermistor sensor 15 to irradiate the heating chamber 7 with microwaves, and controls the energization of the upper radiant heat heating means 13c and the lower radiant heat heating means 13d.

[0062] When the heating control means 64 controls the energization of the left heating coil 10a via the drive circuit 48 and the inverter circuit 40, it controls the input power P calculated from the detection values of the input current detection means 44 and the input voltage detection means 45 based on the heating power instruction set by the user at the left operation unit 16a. At this time, the heating control means 64 controls the input power P corresponding to the material determined by the material determination means 63. Specifically, the heating control means 64 controls the input power P by changing the switching frequency of the upper switch 46c and the lower switch 46d. Also, the heating control means 64 controls so that the coil current value Ic detected by the coil current detection means 52 does not exceed a predetermined constant value, which is a limit current value, corresponding to the material determined by the material determination means 63, so that an overcurrent does not flow through electronic components such as the drive circuit 48 during the heating operation. Note that the heating control means 64 may also use a control method in which the switching frequencies of the upper switch 46c and the lower switch 46d are kept constant and the on-times of the upper switch 46c and the lower switch 46d are adjusted for the control of the input power P.

[0063] The display control means 65 controls the display unit 17. Specifically, the display control means 65 controls the display of the left display unit 17a and the left heating power display unit 18a based on the operation of the left operation unit 16a. The display control means 65 controls the display of the right display unit 17b and the right heating power display unit 18b based on the operation of the right operation unit 16b. The display control means 65 controls the display of the central display unit 17e based on the open signal from the open / close detection unit 11 and the operations of the left operation unit 16a, the right operation unit 16b, and the central operation unit 16e. The display control means 65 causes the central display unit 17e to display the determination results by the respective determination means of the first determination means 61, the second determination means 62, and the material determination means 63. The voice control means 66 controls the voice notification unit 54. For example, the voice control means 66 activates the voice notification unit 54 as necessary, such as when a problem occurs during the operation of the induction heating cooker 1, and notifies the user of the state of the induction heating cooker 1 by voice.

[0064] Next, the operation of the induction heating cooker 1 according to Embodiment 1 will be described. FIG. 11 is a flowchart showing the operation procedure of the induction heating cooker 1 according to Embodiment 1.

[0065] FIG. 11 shows the operation procedure when a small amount of heating power is generated in the cooking container before the energization control is started according to the heating power instruction set by the user, and each determination means performs a determination process. Therefore, in FIG. 11, the operation procedure when the heating control means 64 energizes and controls the left heating coil 10a according to the heating power instruction set by the user is omitted. Also, here, the case where the heating control target is the left heating coil 10a will be described, but the heating control target may be the right heating coil 10b.

[0066] In step S11, when an instruction to start heating is input via the left operation unit using the left heating coil 10a by the user, the heating control means 64 starts the energization control of the left heating coil 10a to generate the minimum required heating power for each determination process. Specifically, the heating control means 64 instructs the drive circuit 48 connected to the inverter circuit 40 of the left heating coil 10a to alternately switch the upper switch 46c and the lower switch 46d between the on state and the off state. Thereby, the inverter circuit 40 supplies a high-frequency voltage to the left heating coil 10a.

[0067] In step S12, the control unit 53 acquires detection values from the input current detection means 44 and the coil current detection means 52, respectively. Specifically, the control unit 53 acquires the input current value Ib as the detection value from the input current detection means 44, and acquires the coil current value Ic as the detection value from the coil current detection means 52. The control unit 53 stores the acquired detection values in a memory (not shown).

[0068] In step S13, the first determination means 61 performs a first determination process using the acquired input current value Ib and coil current value Ic to determine whether a failure has occurred in the electric circuit. The details of the first determination process will be described later with reference to FIGS. 12 and 13. If, as a result of the determination, the first determination means 61 determines that no failure has occurred in the electric circuit, the control unit 53 proceeds to the process of step S14.

[0069] In step S14, the second determination means 62 performs a second determination process using the acquired input current value Ib and coil current value Ic to determine whether the user's usage method is appropriate. The determination as to whether the usage method is appropriate is, for example, to determine whether the cooking container is placed on the top plate 4, or whether the size of the cooking container is appropriate, or whether a cooking container made of a material with a low resistance value and prone to overcurrent flow is being used. Overcurrent means a large current that can destroy electronic components including the drive circuit 48. The details of the second determination process will be described later with reference to FIGS. 14 and 15.

[0070] In step S15, the material determination means 63 determines the material of the cooking container using the acquired input current value Ib and coil current value Ic. The details of the material determination process will be described later with reference to FIGS. 16 and 17. When the material of the cooking container is determined by the material determination means 63, the control unit 53 proceeds to the process of step S16. In step S16, the heating control means 64 continues to heat the cooking container with the left heating coil 10a. Then, the heating control means 64 starts the energization control of the left heating coil 10a according to the heating power instruction set by the user. The material determination is performed by the second determination and the material determination. In the second determination, it is determined whether the cooking container is suitable for heating, and the material determination is performed to change the control method such as overcurrent protection during heating according to the material among the cooking containers suitable for heating.

[0071] Next, with reference to FIGS. 12 and 13, the first determination process of step S13 executed by the first determination means 61 will be described in detail.

[0072] FIG. 12 is an enlarged view of a portion of the first region AR11 shown in FIG. 10. Regarding the input current value Ib and the coil current value Ic, the first region AR11 is a range when a failure occurs in the electric circuit, and the second region AR12 is a range when no failure occurs in the electric circuit. The first threshold value X11 shown in FIG. 12 is, for example, 0.2 A. The second threshold value Y11 shown in FIG. 12 is, for example, 1 A.

[0073] FIG. 13 is a flowchart showing an example of the operation procedure in step S13 shown in FIG. 11. The first determination means 61 reads the input current value Ib and the coil current value Ic acquired in step S12 from a memory (not shown) and proceeds to the process of step S31.

[0074] In step S31, the first determination means 61 determines whether the input current value Ib is less than the first threshold value X11. As a result of the determination in step S31, if the input current value Ib is less than the first threshold value X11 (in the case of step S31: Yes), the first determination means 61 proceeds to the process of step S32. On the other hand, as a result of the determination in step S31, if the input current value Ib is greater than or equal to the first threshold value X11 (in the case of step S31: No), the first determination means 61 determines that no failure has occurred in the electric circuit, and the control unit 53 proceeds to the second determination process.

[0075] In step S32, the first determination means 61 determines whether the coil current value Ic is less than the second threshold value Y11. As a result of the determination in step S32, if the coil current value Ic is greater than or equal to the second threshold value Y11 (in the case of step S32: No), the first determination means 61 determines that no failure has occurred in the electric circuit, and the control unit 53 proceeds to the second determination process.

[0076] On the other hand, in step S32, when the coil current value Ic is less than the second threshold value Y11 (when step S32: Yes), the first determination means 61 determines that a failure has occurred in the electric circuit. Here, in order to prevent misjudgment, as shown in FIG. 13, the first determination means 61 may perform the first determination using the first threshold value X11 and the second threshold value Y11 a plurality of times to determine whether a failure has occurred in the electric circuit.

[0077] In the first embodiment, the first determination means 61 repeatedly performs the process of step S12 and the first determination a plurality of times, counts the number of times Nc1 when Ib < X11 and Ic < Y11, and when the continuously counted number of times Nc1 is greater than a predetermined first specified number of times NCth1, determines that a failure has occurred in the electric circuit. The first specified number of times NCth1 is, for example, 3 times.

[0078] Referring to FIG. 13 for explanation, as a result of the determination in step S32, when the coil current value Ic is less than the second threshold value Y11, the first determination means 61 counts the number of times Nch1 (step S33) and increments the number of times Nch1 by one. In step S34, the first determination means 61 determines whether the number of times Nch1 is greater than the first specified number of times NCth1. When the number of times Nch1 is less than or equal to the first specified number of times NCth1 (when step S34: No), the first determination means 61 proceeds to step S36.

[0079] In step S36, the first determination means 61 determines whether the display unit 17 is displaying that "judgment is in progress". The message "judgment is in progress" is displayed, for example, on the central display unit 71e. When the display unit 17 is displaying "judgment is in progress", the first determination means 61 causes the display control means 65 to continue displaying "judgment is in progress" on the display unit 17 (step S37), and then returns to step S12. On the other hand, when the display unit 17 is not displaying "judgment is in progress", the first determination means 61 causes the display control means 65 to start displaying "judgment is in progress" on the display unit 17 (step S38), and then returns to step S12. Then, in step S12, after newly acquiring the input current value Ib and the coil current value Ic, the first determination means 61 performs the first determination according to steps S31 and S32.

[0080] In steps S36 to S38, while the first determination by the first determination means 61 is repeated, in order to notify the user that the judgment is in progress, the display control means 65 causes the display unit 17 to display information indicating that the judgment is in progress. As a result, the user does not have to worry even if the heating of the cooking container does not start at the set heating power.

[0081] On the other hand, if the result of the determination in step S34 is that the number of times Nc1 is greater than the first specified number of times NCth1 (in the case of step S34: Yes), the first determination means 61 determines that a failure has occurred in the electric circuit (step S35). In this case, the heating control means 64 stops energizing the left heating coil 10a. Further, the display control means 65 causes the display unit 17 to display FIG. 24 in order to notify the user of information indicating that "a failure has occurred in the electric circuit" and information indicating that "the heat treatment cannot be performed". As a result, the user can quickly understand that the heat treatment cannot be performed at the left heating port 5a due to a failure of the induction heating cooker 1.

[0082] Next, with reference to FIGS. 14 and 15, the second determination process in step S14 executed by the second determination means 62 will be described in detail.

[0083] FIG. 14 is a diagram showing a different classification method in the third region AR13 shown in FIG. 10. In FIG. 14, the first region AR11 is not shown in the figure. FIG. 14 shows that the third region AR13 is divided into two regions in terms of the input current value Ib and the coil current value Ic according to the size of the surface of the cooking container that contacts the top plate 4. As shown in FIG. 14, the third region AR13 is divided into a size-based region AR21 and AR22. The size-based region AR21 has a shape with a trapezoid horizontal. The size-based region AR22 has a rectangular shape.

[0084] In FIG. 14, the range of the input current value Ib in the third region AR13 is referred to as the first range, and the range of the coil current value Ic in the third region AR13 is referred to as the second range. The minimum value X21 of the first range is, for example, 2A. The maximum value X22 of the first range is, for example, 8A. For the input current value Ib, the third threshold value X23, which is the boundary value between the size-based regions AR21 and AR22, is, for example, 4A.

[0085] The lower limit value Y21 of the second range is constant and is, for example, 8A. The upper limit value Y23 of the coil current value Ic when the input current value Ib is the minimum value X21 is, for example, 12A. The upper limit value Y24 of the size-based region AR22 is constant and is, for example, 50A. The upper limit value Y22 of the size-based region AR21 changes in proportion to the input current value Ib and is represented by, for example, Equation (1). Upper limit value Y22 of coil current value Ic = 10 × input current value Ib + 12 ···(1)

[0086] Note that in FIG. 14, although the first region AR11 is not shown in the figure, the minimum value X21 of the first range is a value larger than the first threshold value X11 shown in FIG. 12. Also, the lower limit value Y21 of the second range is a value larger than the second threshold value Y11 shown in FIG. 12.

[0087] FIG. 15 is a flowchart showing an example of the operation procedure in step S14 shown in FIG. 11. In the operation procedure shown in FIG. 15, in order to determine the size of the lower surface of the cooking container, before the second determination means 62 performs the process of step S41, the heating control means 64 energizes the left heating coil 10a so that the input current value Ib becomes larger than that at the time of the first determination process. The second determination means 62 acquires the input current value Ib from the input current detection means 44 and the coil current value Ic from the coil current detection means 52 in step S12, and proceeds to the process of step S41.

[0088] Although not shown in FIG. 15, by increasing the input current value Ib to be larger than that at the time of the first determination process and then re-acquiring the input current value Ib and the coil current value Ic, it is possible to reduce the occurrence of misjudgment caused by the coil current value Ic flowing through the left heating coil 10a being too small.

[0089] In step S41, the second determination means 62 determines whether or not the input current value Ib satisfies the condition of being equal to or greater than the minimum value X21 and equal to or less than the maximum value X22 of the first range. As a result of the determination in step S41, if the input current value Ib is equal to or greater than the minimum value X21 and equal to or less than the maximum value X22 of the first range (in the case of step S41: Yes), the second determination means 62 proceeds to the process of step S42.

[0090] In step S42, the second determination means 62 determines whether or not the input current value Ib is equal to or less than the third threshold value X23. As a result of the determination in step S42, if the input current value Ib is equal to or less than the third threshold value X23 (in the case of step S42: Yes), the second determination means 62 proceeds to the process of step S43.

[0091] In step S43, the second determination means 62 determines whether or not the coil current value Ic satisfies the condition of being equal to or greater than the lower limit value Y21 and equal to or less than the upper limit value Y22 of the second range. Here, since the upper limit value Y22 changes in proportion to the input current value Ib, the second determination means 62 calculates the upper limit value Y22 by substituting the input current value Ib into formula (1). As a result of the determination in step S43, when the coil current value Ic is equal to or greater than the lower limit value Y21 and equal to or less than the upper limit value Y22 of the second range (when step S43: Yes), the second determination means 62 determines that a cooking container suitable for heating is being used and the user's usage method is appropriate.

[0092] Specifically, the second determination means 62 determines that the cooking container is placed at the left heating port 5a of the top plate 4, and the size of the cooking container is compatible with the size of the left heating coil 10a, and the cooking container is suitable for heating. In this case, the cooking container belongs to the size-specific area AR21 shown in FIG. 14. When the second determination means 62 determines that a cooking container suitable for heating is being used and the user's usage method is appropriate, the control unit 53 proceeds to the material determination process.

[0093] On the other hand, as a result of the determination in step S42, when the input current value Ib is greater than the third threshold value X23 (when step S42: No), the second determination means 62 proceeds to the process of step S44. In step S44, the second determination means 62 determines whether or not the coil current value Ic satisfies the condition of being equal to or greater than the lower limit value Y21 and equal to or less than the upper limit value Y24 of the second range. As a result of the determination in step S44, when the coil current value Ic is equal to or greater than the lower limit value Y21 and equal to or less than the upper limit value Y24 (when step S44: Yes), the second determination means 62 determines that the user's usage method is appropriate.

[0094] Specifically, the second determination means 62 determines that the cooking container is placed at the left heating port 5a of the top plate 4, and the size of the cooking container is compatible with the size of the left heating coil 10a. In this case, the cooking container belongs to the size-specific area AR22 shown in FIG. 14. When the second determination means 62 determines that the user's usage method is appropriate, the control unit 53 proceeds to the material determination process.

[0095] In the determination of steps S41, S43, and S44, if none of the conditions are satisfied, the second determination means determines that the cooking container is not placed above the heating coil, is not suitable for heating, a cooking container with a small bottom diameter is being used, or a cooking container made of a material with a small resistance value and prone to overcurrent flow is being used, and determines that the user's usage method is inappropriate. Here, in order to prevent misjudgment, as shown in FIG. 15, the second determination means 62 may perform the second determination using the first range and the second range a plurality of times to determine whether the user's usage method is appropriate.

[0096] In the first embodiment, the second determination means 62 repeatedly performs the process of step S12 and the second determination a plurality of times, counts the number of times Nc2 that the conditions of the determination in steps S41, S43, and S44 are not satisfied, and when the continuously counted number of times Nc2 is greater than a predetermined second specified number NCth2, it is considered that the cooking container is not placed above the heating coil, is not suitable for heating, a cooking container with a small bottom diameter is being used, or a cooking container made of a material with a small resistance value and prone to overcurrent flow is being used, and determines that the user's usage method is inappropriate. The second specified number NCth2 is, for example, 15 times.

[0097] Referring to FIG. 15 for explanation, in the determination of steps S41, S43, and S44, if any of the conditions are not satisfied, the second determination means 62 counts the number of times Nch2 (step S45) and increments the number of times Nch2 by one. In step S46, the second determination means 62 determines whether the number of times Nch2 is greater than the second specified number NCth2. If the number of times Nch2 is less than or equal to the second specified number NCth2 (in the case of "No" in step S46), the second determination means 62 proceeds to step S36 shown in FIG. 13.

[0098] In step S36, the second determination means 62 determines whether the display unit 17 is displaying that "judgment is in progress". When the display unit 17 is displaying "judgment is in progress", the second determination means 62 causes the display control means 65 to continue displaying "judgment is in progress" on the display unit 17 (step S37), and then returns to step S12. On the other hand, when the display unit 17 is not displaying "judgment is in progress", the second determination means 62 causes the display control means 65 to start displaying "judgment is in progress" on the display unit 17 (step S38), and then returns to step S12. Then, in step S12, after newly acquiring the input current value Ib and the coil current value Ic, the second determination means 62 performs a second determination according to steps S41 to S44.

[0099] In steps S36 to S38, while the second determination by the second determination means 62 is repeated, in order to notify the user that the judgment is in progress, the display control means 65 causes the display unit 17 to display information indicating that the judgment is in progress. Thereby, even if the heating of the cooking container is not started at the set heating power, the user does not have to worry.

[0100] As a result of the determination in step S46, when the number of times Nc2 is greater than the second specified number of times NCth2 (in the case of step S46: Yes), the second determination means 62 determines that the input current value Ib and the coil current value Ic belong to the region where the cooking container is not placed above the heating coil, a cooking container with a small bottom diameter that is not suitable for heating is used, or a cooking container made of a material with a small resistance value and prone to overcurrent is used, and determines that the user's usage method is inappropriate (step S47). In this case, the heating control means 64 stops energizing the left heating coil 10a to prevent the electric circuit from failing. In addition, the display control means 65 notifies information indicating that "the cooking container is not placed in the left heating port 5a of the top plate 4, the size of the cooking container does not match the size of the left heating coil 10a, or the material of the cooking container is inappropriate" and information indicating that "the heating process cannot be started", and causes the display unit 17 to display FIG. 25. Thereby, the user can quickly understand that the heating process cannot be performed at the left heating port 5a because the usage method is inappropriate.

[0101] In addition, when the second determination means 62 performs the second determination again, after the determination in step S34, it may return to step S12 after a predetermined stop time has elapsed. The time for a series of processes from step S12 to steps S41 to S46 is, for example, 3 seconds including the stop time.

[0102] Next, with reference to FIGS. 16 and 17, the material determination process in step S15 executed by the material determination means 63 will be described in detail.

[0103] FIG. 16 is a diagram showing a portion of the third region AR13 shown in FIG. 10. In FIG. 16, the first region AR11 is omitted from the figure. As described with reference to FIG. 10, in FIG. 14, the third region AR13 is divided into three regions, the material type regions AR31 to AR33. The material of the material type region AR31 is non-magnetic, the material of the material type region AR32 is magnetic, and the material of the material type region AR33 is ferromagnetic. By referring to the information shown in FIG. 16, the material determination means 63 can determine which of non-magnetic, magnetic, and ferromagnetic materials the material of the cooking container belongs to based on the input current value Ib and the coil current value Ic.

[0104] Regarding the coil current value Ic, the boundary value Y31 between the material type regions AR31 and AR32 changes in proportion to the input current value Ib and is represented by, for example, Equation (2). Also, regarding the coil current value Ic, the boundary value Y32 between the material type regions AR32 and AR33 changes in proportion to the input current value Ib and is represented by, for example, Equation (3). Boundary value Y31 of coil current value Ic = 4 × input current value Ib + 17 ···(2) Boundary value Y32 of coil current value Ic = 2 × input current value Ib + 9 ···(3)

[0105] FIG. 17 is a flowchart showing an example of the operation procedure in step S15 shown in FIG. 11. In step S16 shown in FIG. 11, when the heating control means 64 starts the energization control to the left heating coil 10a according to the heating power instruction set by the user, if a large current flows through a material with a small resistance value, the electric circuit may fail. Therefore, the material determination means 63 determines the material of the cooking container and notifies the determination result to the heating control means 64 to reflect it in the energization control. Thereby, it is possible to prevent the electric circuit from failing.

[0106] The material determination means 63 reads the input current value Ib and the coil current value Ic obtained in step S12 of the second determination process from a memory (not shown) and proceeds to the process of step S51. In step S51, the material determination means 63 determines whether or not the coil current value Ic is equal to or greater than the boundary value Y31. Here, since the boundary value Y31 changes in proportion to the input current value Ib, the material determination means 63 substitutes the input current value Ib into Equation (2) to calculate the boundary value Y31.

[0107] As a result of the determination in step S51, when the coil current value Ic is equal to or greater than the boundary value Y31 (Yes in step S51), the material determination means 63 determines that the material of the cooking container is non-magnetic (step S53). On the other hand, as a result of the determination in step S51, when the coil current value Ic is less than the boundary value Y31 (No in step S51), the material determination means 63 proceeds to the process of step S52.

[0108] In step S52, the material determination means 63 determines whether the coil current value Ic is equal to or greater than the boundary value Y32. Here, since the boundary value Y32 changes in proportion to the input current value Ib, the material determination means 63 substitutes the input current value Ib into equation (3) to calculate the boundary value Y32. As a result of the determination in step S52, if the coil current value Ic is equal to or greater than the boundary value Y32 (in the case of step S52: Yes), the material determination means 63 determines that the material of the cooking container is magnetic (step S54). On the other hand, as a result of the determination in step S52, if the coil current value Ic is less than the boundary value Y32 (in the case of step S52: No), the material determination means 63 determines that the material of the cooking container is ferromagnetic (step S55).

[0109] When the material determination means 63 determines the material of the cooking container, it notifies the determination result to the heating control means 64. The heating control means 64 controls the coil current value Ic detected by the coil current detection means 52 so as not to exceed the limit current value according to the material notified from the material determination means 63 so that no overcurrent flows through electronic components such as the drive circuit 48 during the heating operation. In step S53, when the material determination means 63 determines that the material of the cooking container is non-magnetic, the heating control means 64 sets the limit current value to a value lower than that in the case of magnetic or ferromagnetic because non-magnetic is a material through which overcurrent easily flows. In step S54, when the material determination means 63 determines that the material of the cooking container is magnetic, the heating control means 64 sets the limit current value to a value higher than that in the case of non-magnetic but lower than that in the case of ferromagnetic. In step S55, when the material determination means 63 determines that the material of the cooking container is ferromagnetic, the heating control means 64 sets the limit current value to a value higher than that in the case of magnetic because ferromagnetic is a material through which overcurrent hardly flows. Then, the control unit 53 proceeds to heating continuation shown in FIG. 11. In step S16 shown in FIG. 11, the heating control means 64 controls the energization of the left heating coil 10a according to the material of the cooking container determined by the material determination means 63 and the heating power instruction set by the user. Further, the display control means 65 causes the display unit 17 to display information indicating that heating has been started for the cooking container placed in the left heating port 5a according to the set heating power instruction.

[0110] Further, after shifting to step S16, the control unit 53 erases determination information such as the variable upper limit value Y22 from a memory (not shown) in preparation for a heating instruction by the user at the left heating port 5a next time, and initializes each of the counts Nc1 and Nc2 to a zero value.

[0111] When the determination is finalized in step S35, step S47, or step S16, or when heating is started in step S11, the control unit 53 may erase determination information such as the variable upper limit value Y22 from a memory (not shown) and initialize each of the counts Nc1 and Nc2 to a zero value.

[0112] Although the case where the display control means 65 causes the display unit 17 to display the determination result has been described with reference to FIGS. 11 to 17, the voice control means 66 may control the voice notification unit 54 to notify the user of the determination result information by voice.

[0113] Next, a case will be described where the determination process described with reference to FIGS. 11 to 17 is performed for a plurality of types of cooking containers with respect to the material of the cooking container and the size of the lower surface of the cooking container. FIGS. 18 to 20 are diagrams showing a failure of an electric circuit and determination results for a plurality of types of cooking containers by the induction heating cooker 1 according to Embodiment 1. In FIGS. 18 to 20, the vertical axis represents the coil current value Ic, and the horizontal axis represents the input current value Ib.

[0114] The types of cooking containers used as the object of the determination process executed by the induction heating cooker 1 of the present Embodiment 1 are 11 types in total. The types of materials are 5 types: aluminum, copper, non-magnetic, magnetic, and ferromagnetic. Among these materials, the materials suitable for induction heating by the induction heating cooker 1 are non-magnetic, magnetic, and ferromagnetic. All the cooking containers have a circular lower surface, and the types of the diameters of the lower surfaces of the cooking containers are 3 types: 100 mm, 140 mm, and 200 mm. Among these diameters, the diameters suitable for induction heating by the induction heating cooker 1 are 140 mm and 200 mm.

[0115] When the materials are copper and aluminum, they have low resistance values and are materials through which overcurrent easily flows, so they are not suitable for induction heating. Therefore, one type of cooking container with unspecified diameter was prepared for each. When the materials are non-magnetic, magnetic, and ferromagnetic, three types of cooking containers with different diameters were prepared for each, so there are 3 × 3 = 9 types. The total number of types of cooking containers is 11 as described above.

[0116] In FIGS. 18 to 20, the case of a cooking container made of copper is indicated by a triangle, and the case of a cooking container made of aluminum is indicated by a rhombus. The case of a non-magnetic cooking container is indicated by a quadrilateral, the case of a magnetic cooking container is indicated by an inverted triangle, and the case of a ferromagnetic cooking container is indicated by a circle. Regardless of the material and diameter of the cooking container, the case of a failure in the electric circuit is indicated by a star. Also, symbols Φa to Φc representing the diameter of the cooking container are described beside the symbols indicating the material of each cooking container. Φa = 100 mm, Φb = 140 mm, and Φc = 200 mm.

[0117] First, the case of performing the above-described first determination process on these multiple types of cooking containers will be described. FIG. 18 is a diagram showing the result of the first determination process executed by the induction heating cooker 1 according to Embodiment 1 on multiple types of cooking containers.

[0118] As shown in FIG. 18, the cooking containers marked with a star belong to the first region AR11. Therefore, when the first determination means 61 performs the first determination on multiple types of cooking containers according to the procedure shown in FIG. 13, in the case of the cooking containers marked with a star, it is determined that the electric circuit is faulty. On the other hand, referring to FIG. 18, since the cooking containers other than the star belong to the second region AR12, it is determined that the electric circuit is not faulty. The cooking containers other than the star proceed to the second determination process.

[0119] Next, the case of performing the second determination process on the 11 types of cooking containers that passed the first determination process will be described. FIG. 19 is a diagram showing the result of the second determination process executed by the induction heating cooker 1 according to Embodiment 1 on multiple types of cooking containers.

[0120] Among the 11 types of cooking containers, in the determination process of step S41 shown in FIG. 15, as shown in FIG. 19, a cooking container with a non-magnetic material and a diameter of Φa = 100 mm and a cooking container with a magnetic material and a diameter of Φa are determined as "no container" or "inappropriate container". Also, in the determination process of step S43 shown in FIG. 15, since a cooking container made of copper and a cooking container made of aluminum are materials with a small resistance value and are likely to have an overcurrent flowing through them, as shown in FIG. 19, they are determined as "no container" or "inappropriate container".

[0121] On the other hand, cooking containers with Φb = 140 mm, non-magnetic (square), magnetic (inverted triangle), and ferromagnetic (round mark) materials are subject to the determination process of step S43 because the input current value Ib is equal to or less than the third threshold value X23 in the determination of step S42 shown in FIG. 15 (when step S42: Yes). And these three cooking containers belong to the size-specific region AR21 as shown in FIG. 19 because the coil current value Ic belongs to the range of not less than the lower limit value Y21 and not more than the upper limit value Y22 in the determination of step S43 (when step S43: Yes).

[0122] Also, cooking containers with Φc = 200 mm, non-magnetic (square), magnetic (inverted triangle), and ferromagnetic (round mark) materials are subject to the determination process of step S44 because the input current value Ib is greater than the third threshold value X23 in the determination of step S42 shown in FIG. 15 (when step S42: No). And these three cooking containers belong to the size-specific region AR22 as shown in FIG. 19 because the coil current value Ic belongs to the range of not less than the lower limit value Y21 and not more than the upper limit value Y24 in the determination of step S44 (when step S44: Yes).

[0123] In this way, three cooking containers with Φb = 140 mm, non-magnetic (square), magnetic (inverted triangle), and ferromagnetic (round mark) materials and three cooking containers with Φc = 200 mm, non-magnetic (square), magnetic (inverted triangle), and ferromagnetic (round mark) materials are determined as "appropriate containers". And these six cooking containers proceed to the material determination process.

[0124] Next, a case where a material determination process is performed on the six types of cooking vessels that have passed the second determination process will be described. FIG. 20 is a diagram showing the results of the material determination process executed by the induction heating cooker 1 according to the first embodiment for a plurality of types of cooking vessels.

[0125] As shown in FIG. 20, the third region AR13 is divided into three material type regions AR31 to AR33 by two boundary lines of boundary values Y31 and Y32. For cooking vessels with a non-magnetic (square) material and Φb = 140 mm and Φc = 200 mm, in step S51 shown in FIG. 17, since the coil current value Ic is equal to or greater than the boundary value Y31 (in the case of step S51: Yes), as shown in FIG. 20, it belongs to the material type region AR31, and the material is determined to be "non-magnetic".

[0126] On the other hand, for cooking vessels with a magnetic (inverted triangle) material and Φb = 140 mm and Φc = 200 mm, in step S51 shown in FIG. 17, since the coil current value Ic is smaller than the boundary value Y31 (in the case of step S51: No), it becomes the object of the determination process in step S52. And for these two cooking vessels, in the determination of step S52, since the coil current value Ic is equal to or greater than the boundary value Y32 (in the case of step S52: Yes), as shown in FIG. 20, it belongs to the material type region AR32, and the material is determined to be "magnetic".

[0127] Also, for cooking vessels with a ferromagnetic (circle) material and Φb = 140 mm and Φc = 200 mm, in step S51 shown in FIG. 17, since the coil current value Ic is smaller than the boundary value Y31 (in the case of step S51: No), it becomes the object of the determination process in step S52. And for these two cooking vessels, in the determination of step S52, since the coil current value Ic is smaller than the boundary value Y32 (in the case of step S52: No), as shown in FIG. 20, it belongs to the material type region AR33, and the material is determined to be "ferromagnetic".

[0128] As described with reference to FIGS. 18 to 20, for a plurality of actual cooking vessels to be determined, the induction cooker 1 of the first embodiment can determine "electrical circuit failure", "suitable vessel", "no vessel", or "unsuitable vessel". And when the cooking vessel to be determined by the induction cooker 1 of the first embodiment is a "suitable vessel", the material can be determined in order to continue the heating control.

[0129] During the heating operation, in order to prevent an overcurrent from flowing through electronic components such as the drive circuit 48, the control unit 53 controls so that the coil current value Ic detected by the coil current detection means 52 does not exceed the limit current value. When the induction cooker 1 shifts to the heating continuation in step S16 shown in FIG. 11, if the material of the cooking vessel is determined to be non-magnetic in the material determination, since non-magnetic is a material through which an overcurrent easily flows, the heating control means 64 sets the limit current value to a value lower than that in the case of magnetic or ferromagnetic. On the other hand, if the material of the cooking vessel is determined to be magnetic, the heating control means 64 sets the limit current value to a value higher than that in the non-magnetic case but lower than that in the ferromagnetic case. Also, if the material of the cooking vessel is determined to be ferromagnetic, since an overcurrent hardly flows through ferromagnetic, the heating control means 64 sets the limit current value to a value higher than that in the magnetic case. In this way, the heating control means 64 performs energization control so that the heating power is generated efficiently corresponding to the material for the cooking vessel, thereby preventing an overcurrent from flowing through the electric circuit.

[0130] Next, the display on the display unit 17 when the user operates the operation unit 16 of the induction cooker 1 to input a heating instruction to the cooking vessel will be described with reference to FIGS. 21 and 22.

[0131] FIG. 21 is a diagram showing an example of a message displayed on the central display unit 17e when the induction heating cooker 1 according to Embodiment 1 is started. FIG. 22 is a table summarizing the content displayed in the first display area 26 to the third display area 28 of the central display unit 17e shown in FIG. 6 and the initial setting display items when the user operates the central operation unit 16e in the induction heating cooker 1 according to Embodiment 1. In the table shown in FIG. 22, the left display area means the first display area 26 shown in FIG. 6, the central display area means the second display area 27 shown in FIG. 6, and the right display area means the third display area 28 shown in FIG. 6.

[0132] When the user presses the main power key 19 to turn on the main power of the induction heating cooker 1, the left operation unit 16a, the central operation unit 16e, and the right operation unit 16b become in a state of accepting operations, and the display control means 65 causes the central display unit 17e to display the image shown in FIG. 21. After the display control means 65 displays the image shown in FIG. 21 on the central display unit 17e for a predetermined time, the items of the initial settings shown in FIG. 22 are displayed for the first display area 26, the second display area 27, and the third display area 28. Thereby, the user can know the state of the heating control of the heating chamber 7 at present by looking at the content displayed on the central display unit 17e.

[0133] In addition, in this Embodiment 1, although detailed description is omitted, when the main power of the induction heating cooker 1 is turned on, the items of the initial settings of the left heating port 5a are displayed on the left display unit 17a, and the items of the initial settings of the right heating port 5b are displayed on the right display unit 17b.

[0134] Next, an example of the display method by the display unit 17 when the user places the cooking container to be heated on the left heating port 5a or the right heating port 5b and operates the left operation unit 16a or the right operation unit 16b to heat the cooking container with the induction heating cooker 1 will be described with reference to FIGS. 23 to 26. The display by the display unit 17 including the left display unit 17a is controlled by the display control means 65 shown in FIG. 9.

[0135] Here, the case where the user uses the left heating port 5a will be described. When the user places the cooking container to be heated on the left heating port 5a and operates the left operation unit 16a to input a heating power instruction or the like, the induction cooker 1 operates according to the procedure shown in FIG. 11.

[0136] (1) After the control unit 53 performs the process of step S36 shown in FIG. 13, until the determination is finalized, it displays that it is in the determination process. FIG. 23 is a diagram showing an example of a display method indicating that the induction cooker 1 according to the first embodiment is executing a determination process. When the control unit 53 determines whether the cooking container placed on the left heating port 5a is an appropriate container, as shown in FIG. 23, the left display unit 17a displays operation information such as the heating power set by the user. The left heating power display unit 18a blinks a plurality of LEDs. The left heating power display unit 18a shown in FIG. 23 shows a case where the blinking timings of the LEDs at odd positions from the left and the LEDs at even positions are shifted. The second display area 27 of the center display unit 17e displays a message "Determining".

[0137] (2) When the control unit 53 shifts to the process of step S35 shown in FIG. 13 and determines that a failure has occurred in the electric circuit, it causes the left display unit 17a etc. to display as shown in FIG. 24. FIG. 24 is a diagram showing an example of a display method when the induction cooker 1 according to the first embodiment determines that a failure has occurred in the electric circuit. The left display unit 17a displays an error code such as "E8". The left heating power display unit 18a turns off all the LEDs. The center display unit 17e displays a message indicating that an abnormality has occurred in the electric circuit.

[0138] (3) If the control unit 53 shifts to the process of step S47 shown in FIG. 15 and determines that the user's usage method is inappropriate because of "no container" or "inappropriate container", that is, no cooking container is placed above the heating coil, an inappropriate cooking container for heating is used, a cooking container with a small bottom diameter is used, or a cooking container made of a material with a small resistance value and prone to overcurrent flow, the left display unit 17a etc. are controlled as shown in FIG. 25. FIG. 25 is a diagram showing an example of the display method when the induction heating cooker 1 according to Embodiment 1 determines that the user's usage method is inappropriate. As shown in FIG. 25, the display control means 65 turns off the left display unit 17a and the center display unit 17e, and turns off all the LEDs of the left heating power display unit 18a.

[0139] (4) When the control unit 53 shifts to the process of step S16 shown in FIG. 11 and continues to heat the cooking container, the left display unit 17a etc. are displayed as shown in FIG. 26. FIG. 26 is a diagram showing an example of the display method when the induction heating cooker 1 according to Embodiment 1 performs heating control on an appropriate cooking container. As shown in FIG. 26, the left display unit 17a displays operation information such as the heating power set by the user. The left heating power display unit 18a turns on the number of LEDs corresponding to the heating power set by the user. In FIG. 26, five LEDs of the left heating power display unit 18a are on, and among them, one LED is for keeping warm, indicating that the heating level is "4". The second display area 27 of the center display unit 17e displays the message "Heating".

[0140] In this way, the induction heating cooker 1 can determine whether an electrical circuit failure has occurred by comparing the detected input current value Ib and coil current value Ic with the threshold value for determining the presence or absence of an electrical circuit failure. Therefore, when the induction heating cooker 1 determines that an abnormality due to an electrical circuit failure has occurred, it can notify the user of the state of the main body of the induction heating cooker 1 at an early stage by displaying the determination result.

[0141] The induction heating cooker 1 according to Embodiment 1 includes a top plate 4 on which a cooking container for accommodating an object to be heated is placed, a heating coil provided below the top plate 4 for heating the cooking container, an inverter circuit 40 for supplying a high-frequency current to the heating coil, a control unit 53 for controlling the operation of the inverter circuit 40, input current detection means 44, coil current detection means 52, and a display unit 17 for displaying information. The heating coil is the left heating coil 10a or the right heating coil 10b. The input current detection means 44 detects an input current value Ib which is the current input to the inverter circuit 40. The coil current detection means 52 detects a coil current value Ic which is the current input to the heating coil. The control unit 53 includes a first determination means 61, a second determination means 62, and a display control means 65. The first determination means 61 makes a first determination as to whether or not a failure has occurred in the electric circuit including the inverter circuit 40 based on whether or not, after the start of energization of the heating coil, the input current value Ib detected by the input current detection means 44 is less than a predetermined first threshold value X11 and the coil current value Ic detected by the coil current detection means 52 is less than a predetermined second threshold value Y11. The second determination means 62 makes a second determination as to whether or not the cooking container is not placed on the heating coil, the size of the cooking container does not match the size of the heating coil, or the material of the cooking container is not suitable for heating based on whether or not the input current value Ib belongs to a predetermined first range greater than the first threshold value X11 and the coil current value Ic belongs to a predetermined second range greater than the second threshold value Y11. The display control means 65 causes the display unit 17 to display the determination results by the first determination means 61 and the second determination means 62.

[0142] According to Embodiment 1, after the start of energization of the heating coil of the left heating coil 10a or the right heating coil 10b, based on the input current value Ib and the coil current value Ic, it is determined whether or not a failure has occurred in the electric circuit and whether or not the user's usage method is appropriate, and the determination results are displayed on the display unit 17. By referring to the determination results displayed on the display unit 17, the user can understand whether it is a failure of the electric circuit, an inappropriate usage method, or the reason why heating cannot be performed due to any cause, and can shorten the time until the cause is determined.

[0143] Also, consider the order of the first determination process for determining the presence or absence of a failure in the electric circuit and the second determination process for determining whether the user's usage method is appropriate. The case where the user's usage method is inappropriate is, for example, when the cooking container is not placed on the heating coil, when using a cooking container based on an aluminum material with a small resistance value, or when using a small-sized cooking container that does not fit the sizes of the left heating port 5a and the right heating port 5b. In the first embodiment, the first determination process is performed prior to the second determination process. This is because if the electric circuit is faulty, it is obvious that when starting to energize the heating coil, one or both of the input current value Ib and the coil current value Ic cannot be detected, and the second determination process cannot be performed. By performing the first determination process first, the time for discovering a failure in the electric circuit can be shortened.

[0144] Furthermore, in the first embodiment, the control unit 53 may obtain the result by performing the determination a plurality of times as shown in FIGS. 13 and 15, instead of obtaining the result with a single determination for each of the first determination process and the second determination process. In the first embodiment, the results of each determination process of the first determination process and the second determination process are displayed on the display unit 17 and notified to the user. Before energizing the heating coil at the heating power set by the user, in each determination process, energization for determination is performed on the heating coil, and the determination is performed a plurality of times based on the input current value Ib and the coil current value Ic. Therefore, in each determination process, it is possible to reduce the occurrence of misjudgment and lower the probability of notifying the user of an incorrect determination result.

[0145] Here, let's compare the magnitudes of the first specified number of times NCth1 in step S34 shown in FIG. 13 and the second specified number of times NCth2 in step S46 shown in FIG. 15. In the first embodiment, as a specific example, the first specified number of times NCth1 is set to 3 times, and the second specified number of times NCth2 is set to 15 times for explanation. That is, the second specified number of times NCth2 is set to a value larger than the first specified number of times NCth1. This is because when the electric circuit is faulty, it is more important to notify the user of the circuit failure earlier than to determine the appropriateness of the user's usage method.

[0146] Furthermore, according to the first embodiment, when it is determined by the first determination means 61 that a failure has occurred in the electric circuit, or when it is determined by the second determination means 62 that the user's usage method is inappropriate, the heating control means 64 stops the energization of the heating coil. Therefore, the safety of the electric circuit can be enhanced.

[0147] Embodiment 2. In the second embodiment, in the second determination process described in the first embodiment, the determination of whether the user's usage method is appropriate is made based on time instead of the number of times. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted. Also, since the configuration of the induction heating cooker 1 in the second embodiment is the same as the configuration described in the first embodiment, detailed descriptions thereof are omitted.

[0148] The operation of the induction heating cooker 1 according to the second embodiment will be described. In the second embodiment, since the second determination process described in the first embodiment is different, the operation of the second determination means 62 will be mainly described.

[0149] Figure 27 is a flowchart showing the operation procedure of the first determination process shown in FIG. 11 in the induction heating cooker 1 according to Embodiment 2. The operations of steps S11 and S12 shown in FIG. 27 are the same as the operations of steps S11 and S12 described with reference to FIGS. 11 and 13, and thus detailed description thereof is omitted. Also, the operations of steps S31 to S35 shown in FIG. 27 are the same as the operations of steps S31 to S35 described with reference to FIG. 13, and thus detailed description thereof is omitted. In this Embodiment 2 as well, the case of energization control of the left heating coil 10a will be described.

[0150] After the control unit 53 acquires the detection values from the input current detection means 44 and the coil current detection means 52 respectively (step S12), in step S61, it starts measuring the time T from the start of energization until the determination is finalized. After starting the measurement of the time T, the control unit 53 proceeds to step S31. This time T is used in the determination performed within the flowchart of the second determination.

[0151] Figure 28 is a flowchart showing the operation procedure of the second determination process shown in FIG. 11 in the induction heating cooker 1 according to Embodiment 2. The operations of steps S41 to S44 shown in FIG. 28 are the same as the operations of steps S41 to S44 described with reference to FIG. 15, and thus detailed description thereof is omitted.

[0152] The second determination means 62 refers to the time measured by the timer 67, acquires the input current value Ib and the coil current value Ic from the start of energization, and measures the time T for performing a plurality of times until the determination is finalized with one cycle being the time from the start of energization to the determination in step S62. This time T is referred to as the continuous determination time. A stop period may be provided during any of the processes of step S12, step S61, step S13, and steps S41 to S44. In this case, the stop period is included in the continuous determination time T. The continuous determination time T is a time for reducing false determination for the second determination process.

[0153] In the determination of any one of steps S41, S43, and S44, if the conditions are not met, the second determination means 62 proceeds to the determination process of step S62. In step S62, the second determination means 62 determines whether the continuous determination time T is greater than a predetermined specified time Tth. The specified time Tth is, for example, 60 seconds. If the continuous determination time T is less than or equal to the specified time Tth (in the case of No in step S62), the second determination means 62 proceeds to step S36.

[0154] In step S36, the second determination means 62 determines whether the display unit 17 is displaying that "determination is in progress". If the display unit 17 is displaying "determination is in progress", the second determination means 62 causes the display control means 65 to continue the display of "determination is in progress" on the display unit 17 (step S37), and then returns to step S12. On the other hand, if the display unit 17 is not displaying "determination is in progress", the second determination means 62 causes the display control means 65 to start the display of "determination is in progress" on the display unit 17 (step S38), and then returns to step S12. Then, after newly acquiring the input current value Ib and the coil current value Ic in step S12, the second determination means 62 continues to measure the continuous determination time T (step S61), and performs the second determination according to steps S41 to S44.

[0155] The continuous determination time T is the total time of determination until the determination is finalized for error detection prevention, with one cycle being the time taken for a series of processes from step S12 to step S13 and S14 and then back to step S12 again in the flowcharts shown in FIGS. 27 and 28, including the stop period and the time for which the determination process is being performed.

[0156] On the other hand, after the second determination means 62 repeats the second determination a plurality of times, if the conditions are not satisfied in any of the determinations in steps S41, S43, and S44, the process proceeds to the determination process in step S46. As a result of the determination, if the continuous determination time T is greater than the specified time Tth (in the case of step S62: Yes), the second determination means 62 determines that the user's usage method is inappropriate (step S47). In this case, the heating control means 64 stops the energization of the left heating coil 10a to prevent the electric circuit from malfunctioning. Further, the display control means 65 causes the display unit 17 to display information to the effect that "Is the cooking container not placed in the left heating port 5a of the top plate 4, is the size of the cooking container not compatible with the size of the left heating coil 10a, or is the material of the cooking container inappropriate?" and information to the effect that "The heat treatment cannot be performed". Thereby, it is considered that the cooking container is not arranged above the heating coil, a cooking container with a small bottom diameter that is not suitable for heating is being used, or a cooking container made of a material with a small resistance value and prone to overcurrent is being used, and the user can quickly understand that the heat treatment cannot be performed at the left heating port 5a because the usage method is inappropriate. Note that the voice control means 66 may control the voice notification unit 54 to notify the user of the determination result information by voice.

[0157] In addition, when the cooking container cannot be heated due to a malfunction of the electric circuit, it is desirable to quickly notify the user that the electric circuit is malfunctioning. Therefore, in the first determination process described with reference to FIG. 13, the time until Nc1>NCth1 (in the case of step S34: Yes) from the start of energization and it is determined that the electric circuit is malfunctioning is preferably shorter than the specified time Tth.

[0158] In the second embodiment, an example of the display method by the display unit 17 for the induction cooker 1 to notify the user in correspondence with the above-described operation procedure will be described with reference to FIGS. 23 to 26. Here, the case where the user uses the left heating port 5a will be described. Regarding FIGS. 23 to 26, the same description as that described in the first embodiment will be omitted.

[0159] (1) In steps S37 and S38 shown in FIG. 27, the control unit 53 causes the display unit 17 to display as shown in FIG. 23 until the determination is finalized. When the control unit 53 determines whether the cooking container placed on the left heating port 5a is an appropriate container, as shown in FIG. 23, the left display unit 17a displays operation information such as the heating power set by the user.

[0160] (2) In step S35 shown in FIG. 27, when the control unit 53 determines that a failure has occurred in the electric circuit, it causes the left display unit 17a etc. to display as shown in FIG. 24. As shown in FIG. 24, the left display unit 17a displays an error code such as "E8".

[0161] (3) In step S47 shown in FIG. 28, when the control unit 53 determines that the user's usage method is inappropriate due to "no container" or "inappropriate container", it controls the left display unit 17a etc. as shown in FIG. 25. As shown in FIG. 25, the display control means 65 turns off the left display unit 17a and the center display unit 17e, and turns off all the LEDs of the left heating power display unit 18a.

[0162] (4) In step S16 shown in FIG. 11, when the control unit 53 continues to heat the cooking container, it causes the left display unit 17a etc. to display as shown in FIG. 26. As shown in FIG. 26, the left display unit 17a displays operation information such as the heating power set by the user. The left heating power display unit 18a turns on the number of LEDs corresponding to the heating power set by the user. The second display area 27 of the center display unit 17e displays a message of "heating".

[0163] In this way, also in the second embodiment, when the induction cooker 1 determines that an abnormality due to a failure in the electric circuit has occurred, by displaying the determination result, the user can be notified early about the state of the main body of the induction cooker 1.

[0164] In the induction heating cooker 1 according to the second embodiment, the second determination means 62 repeatedly makes the second determination from the start of energization of the left heating coil 10a, measures the time during which the input current value Ib does not belong to the first range and the time T during which the coil current value Ic does not belong to the second range, and determines that the user's usage method is inappropriate when the measured time T is greater than a predetermined specified time Tth.

[0165] In the first embodiment, in the determination process of step S46 described with reference to FIG. 15, when the number of times Nch2 continuously becomes greater than the second specified number of times NCth2, it is determined that the user's usage method is inappropriate. The second specified number of times NCth2 is, for example, 15 times. On the other hand, in the second embodiment, when it is determined that the user's usage method is inappropriate for a specified time Tth, for example, 60 seconds, information indicating that the user's usage method is inappropriate is notified to the user. Also in the second embodiment, as in the first embodiment, after making multiple determinations for each of the first determination process and the second determination process, the presence or absence of a failure in the electric circuit and the determination result as to whether the user's usage method is appropriate are notified to the user. Therefore, in each determination process, it is possible to reduce the occurrence of misjudgment and lower the probability of notifying the user of an incorrect determination result.

[0166] Also, after shifting to step S16, the control unit 53 erases determination information such as the variable upper limit value Y22 from a memory (not shown) in preparation for the next heating instruction by the user at the left heating port 5a, and initializes each of the number of times Nc1 and the time T to a value of zero.

[0167] Alternatively, when the determination is finalized in step S35, step S47, or step S16, or when heating is started in step S11, the control unit 53 may erase determination information such as the variable upper limit value Y22 from a memory (not shown) and initialize each of the number of times Nc1 and the time T to a value of zero.

[0168] As described above, the induction heating cooker 1 has been described in detail with respect to the preferred embodiments. However, without being limited to the above-described embodiments, various changes and substitutions may be made to the above-described embodiments without departing from the scope described in the claims.

[0169] Hereinafter, various aspects of the induction heating cooker 1 of the present disclosure will be summarized as appendices.

[0170] (Appendix 1) A top plate on which a cooking container for accommodating an object to be heated is placed, A heating coil provided below the top plate for heating the cooking container, An inverter circuit for supplying a high-frequency current to the heating coil, A control unit for controlling the operation of the inverter circuit, Input current detection means for detecting an input current value which is the value of the current input to the inverter circuit, Coil current detection means for detecting a coil current value which is the current input to the heating coil, A display unit for displaying information, having The control unit After the energization of the heating coil starts, based on whether the input current value detected by the input current detection means is less than a predetermined first threshold value and whether the coil current value detected by the coil current detection means is less than a predetermined second threshold value, a first determination means for making a first determination as to whether a failure has occurred in the electric circuit including the inverter circuit; Based on a determination as to whether the input current value belongs to a predetermined first range greater than the first threshold value and whether the coil current value belongs to a predetermined second range greater than the second threshold value, a second determination means for determining that the cooking container is not placed on the heating coil, the size of the cooking container does not match the size of the heating coil, or the material of the cooking container is not suitable for heating; Display control means for causing the display unit to display the determination results by the first determination means and the second determination means. Induction heating cooker (Appendix 2) The first determination means When the input current value is less than the first threshold value and the coil current value is less than the second threshold value from the start of energization of the heating coil, the first determination is repeated, and the number of times the input current value is less than the first threshold value and the coil current value is less than the second threshold value is counted. When the continuously counted number of times is greater than a predetermined first specified number of times, the energization of the heating coil is stopped. The induction heating cooker according to Appendix 1 (Appendix 3) The second determination means When the input current value does not belong to the first range or the coil current value does not belong to the second range from the start of energization of the heating coil, the second determination is repeated, and the number of times of repetition is further counted. When the continuously counted number of times is greater than a predetermined second specified number of times, the energization of the heating coil is stopped. The induction heating cooker according to Appendix 1 or 2 (Appendix 4) The second determination means When the input current value does not belong to the first range or the coil current value does not belong to the second range from the start of energization of the heating coil, the second determination is repeated, and the time from the start of energization is further measured. When the measured time is greater than a predetermined specified time, the energization of the heating coil is stopped. The induction heating cooker according to Appendix 1 or 2 (Appendix 5) The second determination means When the input current value belongs to the first range and is less than or equal to a third threshold value determined based on the area of contact between the cooking container and the top plate, the upper limit value of the second range is changed in proportion to the input current value. The induction heating cooker according to any one of Appendices 1 to 4 (Appendix 6) The display control means While the first determination by the first determination means is repeated, cause information indicating that the determination is in progress to be displayed on the display unit. When the number of times continuously counted by the first determination means is greater than the first specified number of times, cause information for notifying that the electric circuit has failed to be displayed on the display unit. The induction heating cooker according to Supplementary Note 2.

Explanation of Signs

[0171] 1 Induction heating cooker, 2 Kitchen furniture, 3 Main body, 4 Top plate, 5 Heating chamber, 5a Left heating port, 5b Right heating port, 6 Exhaust port cover, 7 Heating chamber 8 Heating door, 9 Handle, 10a Left heating coil, 10b Right heating coil, 11 Open / close detection unit, 12 Microwave heating means, 13c Upper radiant heat heating means, 13d Lower radiant heat heating means, 14 Infrared sensor, 15 Thermistor sensor, 16 Operation unit, 16a Left operation unit, 16b Right operation unit, 16e Central operation unit, 17 Display unit, 17a Left display unit, 17b Right display unit, 17e Central display unit, 18a Left heating power display unit, 18b Right heating power display unit, 19 Main power key, 20a~24a, 20b~24b Input keys, 25a, 25b, 25e Light emitting units, 26 First display area, 27 Second display area, 28 Third display area, 29~37 Input keys, 38 AC power supply, 39 DC power supply circuit, 40 Inverter circuit, 41 Rectifier diode bridge, 42 Reactor, 43 Smoothing capacitor, 44 Input current detection means, 45 Input voltage detection means, 46c Upper switch, 46d Lower switch, 47c Upper diode, 47d Lower diode, 48 Drive circuit, 49 Load circuit, 50 Resonance capacitor, 51 Clamp diode, 52 Coil current detection means, 53 Control unit, 54 Voice notification unit, 61 First determination means, 62 Second determination means, 63 Material determination means, 64 Heating control means, 65 Display control means, 66 Voice control means, 67 Timer.

Claims

1. A top plate on which a cooking container for containing an object to be heated is placed, A heating coil provided below the top plate for heating the cooking container, An inverter circuit for supplying a high-frequency current to the heating coil, A control unit for controlling the operation of the inverter circuit, Input current detection means for detecting an input current value which is the value of the current input to the inverter circuit, Coil current detection means for detecting a coil current value which is the current input to the heating coil, A display unit for displaying information, having, The control unit, After starting energization of the heating coil, based on whether or not the input current value detected by the input current detection means is less than a predetermined first threshold value and the coil current value detected by the coil current detection means is less than a predetermined second threshold value, first determination means for performing a first determination as to whether or not a failure has occurred in the electric circuit including the inverter circuit, Based on the determination as to whether or not the input current value belongs to a predetermined first range greater than the first threshold value and the coil current value belongs to a predetermined second range greater than the second threshold value, second determination means for determining that the cooking container is not placed on the heating coil, the size of the cooking container does not match the size of the heating coil, or the material of the cooking container is not suitable for heating, Display control means for causing the display unit to display information indicating that the determination is in progress until the determination by the first determination means and the second determination means is finalized, having, The first determination means, Repeating the first determination for determining whether or not the input current value is less than the first threshold value and the coil current value is less than the second threshold value since the start of energization of the heating coil, Counting the number of times the input current value is less than the first threshold value and the coil current value is less than the second threshold value, When the continuously counted number of times is 1 or more and less than a predetermined first specified number of times, determining that the failure determination of the electric circuit is in progress, and when the continuously counted number of times is greater than the first specified number of times, determining that a failure has occurred in the electric circuit, The second determination means, Repeating the second determination for determining whether or not the input current value belongs to the first range and the coil current value belongs to the second range since the start of energization of the heating coil, Count the number of times the input current value does not belong to the first range and the number of times the coil current value does not belong to the second range, or measure the time from the start of energization. When the continuously counted number of times is 1 or more and less than a predetermined second specified number of times, or when the measured time is less than or equal to a predetermined specified time, it is determined that the user's usage method is being judged. When the continuously counted number of times is greater than the second specified number of times, or when the measured time is greater than the specified time, it is determined that the user's usage method is inappropriate. The display control means Differentiates the display state of the display unit between the case where it is determined by the first determination means that a failure has occurred in the electric circuit and the case where it is determined by the second determination means that the user's usage method is inappropriate. Induction heating cooker.

2. The second determination means When the input current value belongs to the first range and is less than or equal to a third threshold value determined based on the area of contact between the cooking container and the top plate, the upper limit value of the second range is changed to be proportional to the input current value. The induction heating cooker according to claim 1.

3. The control unit Has heating control means for controlling the operation of the inverter circuit corresponding to the determination results of the first determination means and the second determination means. The heating control means When it is determined by the first determination means that a failure has occurred in the electric circuit, or when it is determined by the second determination means that the user's usage method is inappropriate, stops energization to the heating coil. The induction heating cooker according to claim 1.

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