Inductive heating cooker

An inductive heating cooker includes a main body and a power-receiver device. The main body includes a top plate on which a heating target is placed, a heating coil provided under the top plate and configured to inductively heat the heating target, a drive circuit configured to supply electric power to the heating coil, a power transmission coil configured to transmit the electric power by magnetic resonance, and a power transmission circuit configured to supply the electric power to the power transmission coil. The power-receiver device includes a power reception coil configured to receive the electric power from the power transmission coil by the magnetic resonance, and a load circuit configured to operate by the electric power received by the power reception coil.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of PCT/JP2017/002954 filed on Jan. 27, 2017, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an inductive heating cooker that performs non-contact power transmission using a magnetic resonance method.

BACKGROUND ART

An inductive heating cooker has been proposed in which a temperature detection unit is provided to a top plate. The inductive heating cooker includes a first coil provided at a bottom surface of the top plate, and a second coil provided in the temperature detection unit. When the second coil is provided to face the first coil, the first coil is coupled to the second coil by electromagnetic inductive coupling. Thus, the electric power is supplied from the first coil to the second coil.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the existing inductive heating cooker, the electric power is supplied by the electromagnetic inductive coupling. Thus, a power reception coil (second coil) provided in a power-receiver device (temperature detection unit) needs to face a power transmission coil (first coil) for supplying the electric power, which results in restriction on the installation position of the power-receiver device.

The present invention has been made to solve the above-described problem, and an object of the present invention is to obtain an inductive heating cooker in which the electric power is transmitted from a main body to a power-receiver device, the inductive heating cooker being capable of alleviating restriction on an installation position of the power-receiver device.

Solution to Problem

An inductive heating cooker of an embodiment of the present invention includes a main body and a power-receiver device. The main body includes a top plate on which a heating target is placed, a heating coil provided under the top plate and configured to inductively heat the heating target, a drive circuit configured to supply electric power to the heating coil, a power transmission coil configured to transmit the electric power by magnetic resonance, and a power transmission circuit configured to supply the electric power to the power transmission coil. The power-receiver device includes a power reception coil configured to receive the electric power from the power transmission coil by the magnetic resonance, and a load circuit configured to operate by the electric power received by the power reception coil.

Advantageous Effects of Invention

An inductive heating cooker of an embodiment of the present invention includes a main body having a power transmission coil configured to transmit the electric power by magnetic resonance, and a power-receiver device having a power reception coil configured to receive the electric power from the power transmission coil by the magnetic resonance. Consequently, the restriction on an installation position of the power-receiver device can be alleviated.

DESCRIPTION OF EMBODIMENTS

FIG. 1is an exploded perspective view illustrating a main body of an inductive heating cooker according to Embodiment 1.

FIG. 2is a perspective view illustrating the main body and a power-receiver device of the inductive heating cooker according to Embodiment 1.

As illustrated inFIG. 1andFIG. 2, an upper portion of a main body100of the inductive heating cooker includes a top plate4on which a heating target5such as a pot is placed. A power-receiver device200to which the electric power is transmitted from the main body100is placed on the top plate4and is allowed to be detached from the top plate4. In the inductive heating cooker according to Embodiment 1, the power-receiver device200includes a temperature sensor configured to detect a temperature of the heating target5. The details will be described later.

The top plate4of the main body100includes a first heating area1, a second heating area2, and a third heating area3as heating areas for inductively heating the heating target5. A first heating unit11, a second heating unit12, and a third heating unit13are provided to correspond to the respective heating areas. The main body100is configured to enable inductive heating of the heating target5placed on one of the heating areas.

In Embodiment 1, the first heating unit11and the second heating unit12are provided to be laterally aligned close to the front of the main body100, and the third heating unit13is provided substantially at the center of the main body100close to the rear of the main body100. Note that the arrangement of the heating areas is not limited to the one described above. For example, the three heating areas may be arranged to be aligned laterally in a substantially linear manner. Furthermore, the first heating unit11and the second heating unit12may be provided in such a manner that the respective centers of the first heating unit11and the second heating unit12are different in position in the depth direction. The number of heating areas is not limited to three, and may be one or two, or four or more.

The whole of top plate4is made of an infrared transmitting material such as heat-resistant reinforced glass, crystallized glass, and borosilicate glass. The top plate4is fixed to an outer circumference of an upper opening of the main body100by use of a rubber packing or sealing material interposed between the top plate4and the main body100in such a manner that the outer circumference of the upper opening of the main body100is impermeable to water. On the top plate4, circular pot position marks roughly indicating pot placement positions are formed by painting or printing, for example, corresponding to respective heating ranges (the heating areas) of the first heating unit11, the second heating unit12, and the third heating unit13.

An operation unit40a, an operation unit40b, and an operation unit40c(hereinafter occasionally collectively referred to as the operation units40) are provided close to the front of the top plate4as input devices each for setting heating power to be input (electric power to be input) and a cooking menu (such as boiling mode and frying mode) when the heating target5is heated by the corresponding one of the first heating unit11, the second heating unit12, and the third heating unit13. Furthermore, a display unit41a, a display unit41b, and a display unit41c(hereinafter occasionally collectively referred to as the display units41) for displaying information such as the operating state of the main body100and details of inputs and operations sent from the operation units40are provided close to the operation units40.

Note that the configurations of the operation units40ato40cand the display units41ato41care not limited to particular configurations. For example, the operation units40ato40cand the display units41ato41cmay be provided for the respective heating areas, or an operation unit40and a display unit41may be provided for the heating areas as a whole. Note that the operation units40ato40care made of mechanical switches, such as push switches and tactile switches, or touch switches that detect an input operation through a change in capacitance of an electrode, for example. Furthermore, the display units41ato41care made of liquid crystal devices (LCDs) or LEDs, for example.

Note that the following description will be given of a case in which a display-and-operation unit43configured in such a manner that the operation units40and the display units41are integrated is provided. The display-and-operation unit43is made of a touch panel having touch switches arranged on an upper surface of an LCD, for example.

Under the top plate4, the main body100accommodates the first heating unit11, the second heating unit12, and the third heating unit13, each of which is made of a heating coil. Note that at least one of the first heating unit11, the second heating unit12, and the third heating unit13may be made of an electric heater configured to perform radiation heating, for example (a nichrome wire, a halogen heater, or a radiant heater, for example).

The heating coil is formed by winding a conductive wire made of a given metal (copper or aluminum, for example) and coated with an insulating film. Each of the heating coils is supplied with a high-frequency power by drive circuits50, and thereby generates a high-frequency magnetic field.

The main body100of the inductive heating cooker accommodates the drive circuits50configured to supply the high-frequency power to the heating coils of the first heating unit11, the second heating unit12, and the third heating unit13, and a control unit45configured to control the operation of the entire inductive heating cooker including the drive circuits50.

A power transmission coil65configured to transmit the electric power to the power-receiver device200by magnetic resonance is provided under the top plate4of the main body100. The power transmission coil65is formed by winding a conductive wire made of a given metal (copper or aluminum, for example) and coated with an insulating film. The inductance of the power transmission coil65is smaller than that of the heating coil.

As illustrated inFIG. 1, the power transmission coil65is provided along an edge of the top plate4, for example. The power transmission coil65is provided to surround the first heating unit11, the second heating unit12, and the third heating unit13, in a plan view. Thus, a range can be increased in which one power transmission coil65is provided in an area of the top plate4in which the heating units are not provided.

Note that the shape and arrangement of the power transmission coil65are not limited to the ones described above. For example, the power transmission coil65may be provided to surround one heating unit (heating coil) in a plan view. Furthermore, a plurality of power transmission coils65may be provided.

FIG. 3is a block diagram illustrating a configuration of the main body and the power-receiver device of the inductive heating cooker according to Embodiment 1.

FIG. 3illustrates a state in which the heating target5is placed on one of the heating areas on the top plate4of the main body100of the inductive heating cooker, and the power-receiver device200is placed on an area of the top plate4in which the heater areas are not provided.

A non-contact power transmission system includes the main body100of the inductive heating cooker serving as a non-contact power transmission device, and the power-receiver device200.

As illustrated inFIG. 3, the heating coil11a, the display-and-operation unit43, the control unit45, a main-body communication device47, the drive circuits50, a power transmission circuit60, and the power transmission coil65are provided in the main body100of the inductive heating cooker.

The control unit45is made of a device such as a microcomputer and a digital signal processor (DSP). On the basis of information such as details of operations of the display-and-operation unit43and communication information received from the main-body communication device47, the control unit45controls the drive circuits50. The control unit45further displays information on the display-and-operation unit43depending on factors such as the operating state.

The main-body communication device47is made of a wireless communication interface conforming to a given communication standard, such as a wireless LAN, Bluetooth (registered trademark), infrared communication, and near field communication (NFC), for example. The main-body communication device47conducts wireless communication with a power-receiver communication device85of the power-receiver device200.

The power transmission circuit60supplies the electric power to the power transmission coil65. The details will be described later.

The power-receiver device200placed, for example, on the top plate4receives the electric power from the main body100in a non-contact manner. The power-receiver device200includes a power reception coil80, a power reception circuit81, a power-receiver control unit83, the power-receiver communication device85, and a temperature sensor90serving as a load circuit.

The power reception coil80receives the electric power from the power transmission coil65through electromagnetic resonance. The power reception circuit81supplies the electric power received by the power reception coil80to a load. The details will be described later.

The power-receiver control unit83, the power-receiver communication device85, and the temperature sensor90are operated by the electric power supplied from the power reception circuit81.

The temperature sensor90is made of an infrared ray sensor, for example, and detects the temperature of a side surface of the heating target5placed on the top plate4in a non-contact manner. Note that the temperature sensor90may be made of a contact type sensor such as a thermistor, for example. The temperature sensor90outputs a voltage signal corresponding to the detected temperature to the power-receiver control unit83.

The power-receiver control unit83is made of a device such as a microcomputer and a digital signal processor (DSP). The power-receiver control unit83causes the temperature sensor90to transmit the information on the temperature detected by the temperature sensor90to the power-receiver communication device85.

The power-receiver communication device85is made of a wireless communication interface conforming to the communication standard of the main-body communication device47. The power-receiver communication device85conducts wireless communication with the main-body communication device47.

Note that the temperature sensor90in Embodiment 1 corresponds to a “load circuit” in the present invention.

The power-receiver communication device85corresponds to a “first communication device” in the present invention.

The main-body communication device47corresponds to a “second communication device” in the present invention.

FIG. 4is a diagram illustrating one of the drive circuits of the inductive heating cooker according to Embodiment 1.

Note that the drive circuits50are provided for the respective heating units. The drive circuits50may have the same circuit configuration, or may have different circuit configurations for the respective heating units.FIG. 4illustrates only one of the drive circuits50. As illustrated inFIG. 4, the drive circuit50includes a direct-current power supply circuit22, an inverter circuit23, and a resonant capacitor24.

An input current detecting unit25is made of a current sensor, for example. The input current detecting unit25detects a current to be input to the direct-current power supply circuit22from an alternating-current power supply (commercial power supply)21, and outputs a voltage signal corresponding to the value of the input current to the control unit45.

The direct-current power supply circuit22includes a diode bridge22a, a reactor22b, and a smoothing capacitor22c. The direct-current power supply circuit22converts an alternating-current voltage input to the direct-current power supply circuit22from the alternating-current power supply21into a direct-current voltage, and outputs the direct-current voltage to the inverter circuit23.

The inverter circuit23is an inverter known as a half-bridge inverter, in which IGBTs23aand23bserving as switching elements are each connected in series with the corresponding one of outputs of the direct-current power supply circuit22. In the inverter circuit23, diodes23cand23dare connected in parallel with the IGBTs23aand23b, respectively, as flywheel diodes. The IGBTs23aand23bare driven on and off by a drive signal output from the control unit45. The control unit45outputs the drive signal to alternately turn on and off the IGBTs23aand23bby placing the IGBT23bin the off state when the IGBT23ais turned on and placing the IGBT23bin the on state when the IGBT23ais turned off. The inverter circuit23thereby converts the direct-current power output from the direct-current power supply circuit22into alternating-current power having a specified frequency, and supplies the electric power to a resonant circuit made of the heating coil11aand the resonant capacitor24. Note that the alternating-current power having a specified frequency is alternating-current power having a high frequency ranging from equal to or more than 20 kHz to less than 100 kHz.

With the resonant capacitor24connected in series with the heating coil11a, the resonant circuit has a resonant frequency corresponding to factors such as the inductance of the heating coil11aand the capacitance of the resonant capacitor24. When magnetic coupling with the heating target5(a metal load) is made, the inductance of the heating coil11achanges depending on characteristics of the metal load, and the resonant frequency of the resonant circuit changes depending on the change in the inductance.

With the drive circuit50configured in this manner, a high-frequency current of approximately tens of amperes flows through the heating coil11a, and the heating target5placed on a part of the top plate4immediately above the heating coil11ais inductively heated by a high-frequency magnetic flux produced by the flowing high-frequency current.

Note that each of the IGBTs23aand23bserving as a switching element is made of a semiconductor made of a silicon-based material, for example, but may be made of a wideband gap semiconductor made of a material such as a silicon carbide-based material and a gallium nitride-based material. The use of the wideband gap semiconductor as the switching element enables power supply loss of the switching element to be reduced, and favorable heat transfer from the drive circuit50to be achieved even when the switching frequency (driving frequency) is increased to a high frequency (high speed). Consequently, it is possible to reduce the size of heat transfer fins of the drive circuit50, and thus to reduce the size and cost of the drive circuit50.

A coil current detecting unit26is connected to the resonant circuit made of the heating coil11aand the resonant capacitor24. The coil current detecting unit26is made of a current sensor, for example. The coil current detecting unit26detects the current flowing through the heating coil11aand outputs a voltage signal corresponding to the value of the coil current to the control unit45.

Note thatFIG. 4illustrates the half-bridge drive circuit, but it is needless to say that a full-bridge drive circuit made of four IGBTs and four diodes may be used.

(Power Transmission Using Magnetic Resonance Method)

FIG. 5is a diagram illustrating a configuration of the main body and the power-receiver device of the inductive heating cooker according to Embodiment 1.FIG. 6is a specific circuit diagram of a configuration ofFIG. 5.

Note thatFIG. 5andFIG. 6each illustrate a configuration relating to power transmission using a magnetic resonance method, of the main body100and the power-receiver device200of the inductive heating cooker.

The main body100and the power-receiver device200of the inductive heating cooker form a non-contact power transmission system adopting a magnetic resonance method (resonant coupling type) of performing power transmission using the resonance characteristics. More specifically, the main body100of the inductive heating cooker forms a resonance type power transmission device that transmits the electric power to the power-receiver device200by magnetic resonance. The power-receiver device200is a resonance type power-receiver device that receives the electric power from the main body100by magnetic resonance.

As illustrated inFIG. 5andFIG. 6, the power transmission circuit60of the main body100includes a resonance type power supply60aand a matching circuit60b.

The resonance type power supply60acontrols the supply of electric power to the power transmission coil65, converts direct current or alternating current input power into an alternating current having a predetermined frequency, and outputs this alternating current. This resonance type power supply60ais made of a power supply circuit having a resonance switching method, and has an output impedance Zo, a resonance frequency fo, and a resonance characteristic value Qo.

The resonance frequency fo of the resonance type power supply60ais set to a frequency in a MHz band.

The resonance frequency fo is 6.78 MHz, for example. Note that the resonance frequency fo is not limited to 6.78 MHz, and may be a frequency that is an integral multiple of 6.78 MHz in the MHz band.

The matching circuit60bperforms impedance matching the output impedance Zo of the resonance type power supply60a, and the pass characteristic impedance Zt of the power transmission coil65. This matching circuit60bis made of a filter of π type or L type that includes inductors L and capacitors C, and has the pass characteristic impedance Zp of the filter.

The power transmission coil65receives the alternating current power from the resonance type power supply60avia the matching circuit60b, and performs a resonance operation to generate a non-radiative electromagnetic field in the vicinity of the power transmission coil65, thereby transmitting the electric power to the power reception coil80of the power-receiver device200. This power transmission coil65forms a resonance circuit including a coil and a capacitor C5, and serves as a resonance type antenna. The power transmission coil65has the pass characteristic impedance Zt, a resonance frequency ft, and a resonance characteristic value Qt.

Furthermore, the resonance frequency fo and the resonance characteristic value Qo of the resonance type power supply60aare determined from the output impedance Zo of the resonance type power supply60aand the pass characteristic impedance Zp of the matching circuit60b. The resonance frequency ft and the resonance characteristic value Qt of the power transmission coil65are determined from the pass characteristic impedance Zt of the power transmission coil65and the pass characteristic impedance Zp of the matching circuit60b.

It is then seen that the main body100of the inductive heating cooker has a resonance characteristic value Qtx of the following mathematic formula (1) on the basis of these two resonance characteristic values Qo and Qt.
[Math. 1]
Qtx=√(Qo·Qt)  (1)

The power reception circuit81of the power-receiver device200includes a rectifier circuit81a, and a conversion circuit81b.

The power reception coil80receives the electric power by performing a resonant coupling operation of coupling with the non-radiative electromagnetic field from the power transmission coil65, and outputs the alternating current power. This power reception coil80forms a resonance circuit including a coil and a capacitor C11, and serves as a resonance type antenna. The power reception coil80has the pass characteristic impedance Zr.

The rectifier circuit81ais a matching rectifier circuit having a rectifying function of converting the alternating current power from the power reception coil80into direct current power, and a matching function of performing impedance matching the pass characteristic impedance Zr of the power reception coil80and the input impedance ZRL of the conversion circuit81b. The matching function is performed by a filter of π type or L type that includes inductors L and capacitors C. The rectifier circuit81aalso has a pass characteristic impedance Zs. Although the rectifier circuit81ahaving the rectifying function and the matching function is shown above, the rectifier circuit81ais not limited to the one shown above, and can include only the rectifying function even though its rectifying efficiency drops.

The conversion circuit81breceives the direct current power from the rectifier circuit81a, and converts this direct current power into a predetermined voltage and supplies this predetermined voltage to a load circuit (temperature sensor90or other devices). This conversion circuit81bis made of an LC filter (smoothing filter) for smoothing a high-frequency voltage ripple, a DC-DC converter for converting the direct current power into the direct current power having the predetermined voltage, and other devices, and has the input impedance ZRL of the conversion circuit81b. As an alternative, the DC-DC converter can be eliminated, and the conversion circuit81bcan be made only of the smoothing filter.

Furthermore, the resonance characteristic value Qr and the resonance frequency fr of the power-receiver device200are determined from the pass characteristic impedance Zr of the power reception coil80, the pass characteristic impedance Zs of the rectifier circuit81a, and the input impedance ZRL of the conversion circuit81b.

Then, the characteristic impedance of each of the functional units is set in such a manner that there is provided a correlation among the resonance characteristic value Qo of the resonance type power supply60a, the resonance characteristic value Qt of the power transmission coil65, and the resonance characteristic value Qr of the power-receiver device200. More specifically, the resonance characteristic value Qtx (=√(Qo·Qt)) of the main body100is made to approximate the resonance characteristic value Qr of the power-receiver device200(the following mathematic formula (2)).

More specifically, the resonance characteristic value of the main body100preferably falls within the range given by the following mathematic formula (3).
[Math. 2]
√(Qo·Qt)≈Qr(2)
[Math. 3]
0.5Qr≤√(Qo·Qt)≤1.5Qr(3)

Thus, the reduction in the power transmission efficiency can be decreased by providing a correlation among the three resonance characteristic values of the resonance characteristic value Qo of the resonance type power supply60a, the resonance characteristic value Qt of the power transmission coil65, and the resonance characteristic value Qr of the power-receiver device200. Consequently, comparing the power transmission using the magnetic resonance method (resonant coupling type) with the power transmission using the electromagnetic induction method (electromagnetic induction coupling type), the distance between the power transmission coil65and the power reception coil80can be increased.

An operation of the inductive heating cooker of Embodiment 1 will be described below.

A user places the heating target5such as a pot on one of the heating areas of the top plate4of the main body100.

The user also places the power-receiver device200on the top plate4. When the temperature sensor90of the power-receiver device200is a non-contact type sensor such as an infrared ray sensor, for example, the user places the power-receiver device200at a given position on the top plate4. When the temperature sensor90of the power-receiver device200is a contact type sensor such as a thermistor, for example, the user places the power-receiver device200on the top plate4in such a manner that the power-receiver device200contacts the side surface of the heating target5. As described above, in the power transmission using the magnetic resonance method (resonant coupling type), the distance in which the electric power can be transmitted is long, and consequently the power-receiver device200need not to be provided to face the power transmission coil65.

The user performs operation of starting heating (input heating power) with the display-and-operation unit43.

The control unit45controls the inverter circuit23depending on the set electric power (heating power). High-frequency drive signals with a frequency of, for example, approximately 20 kHz to 100 kHz are input to the IGBTs23aand23bof the inverter circuit23and the IGBTs23aand23bare turned on and off alternately, thereby supplying a high-frequency current to the resonance circuit made of the heating coil11aand the resonant capacitor24. When the high-frequency current flows through the heating coil11a, a high-frequency magnetic field is generated, eddy currents flow at a bottom of the heating target5in such a direction as to cancel off magnetic flux variations, and the heating target5is heated by losses due to the flowing eddy currents.

The control unit45operates the power transmission circuit60and causes the power transmission circuit60to start supply of the electric power to the power transmission coil65. The electric power is thereby supplied from the power transmission coil65to the power reception coil80of the power-receiver device200by magnetic resonance. The electric power received by the power reception coil80is supplied from the power reception circuit81to the power-receiver control unit83, the power-receiver communication device85, and the temperature sensor90.

The temperature sensor90of the power-receiver device200detects the temperature of the heating target5. The power-receiver control unit83causes the temperature sensor90to transmit the information on the temperature detected by the temperature sensor90to the power-receiver communication device85.

The main-body communication device47of the main body100receives the information on the temperature transmitted from the power-receiver communication device85, and outputs this information to the control unit45. The control unit45of the main body100controls the driving of the drive circuits50depending on the information on the temperature acquired from the temperature sensor90of the power-receiver device200.

As described above, in Embodiment 1, the main body100includes the top plate4on which the heating target5is placed, the heating coil11aprovided under the top plate4and configured to inductively heat the heating target5, the drive circuit50configured to supply the electric power to the heating coil11a, the power transmission coil65configured to transmit the electric power by magnetic resonance, and the power transmission circuit60configured to supply the electric power to the power transmission coil65. Furthermore, the power-receiver device200includes the power reception coil80configured to receive the electric power from the power transmission coil65by the magnetic resonance, and the load circuit configured to operate by the electric power received by the power reception coil80.

Comparing with the power transmission using the electromagnetic induction coupling, the restriction on an installation position of the power-receiver device200can thus be more alleviated, the power-receiver device200receiving the electric power from the main body100of the inductive heating cooker.

As the electric power is transmitted to the power-receiver device200from the main body100of the inductive heating cooker by magnetic resonance, the electric power can be transmitted even when the power transmission coil65and the power reception coil80are not arranged to face each other. Consequently, it is possible to increase the degree of freedom in the installation position of the power-receiver device200to be placed on the top plate4and improve the usability. With such a configuration as to transmit the electric power when the distance between the power transmission coil65and the power reception coil80is not less than half of the width or depth of the top plate4, for example, the electric power can be stably transmitted even when the power-receiver device200is placed anywhere on the top plate. Consequently, it is possible to obtain an inductive heating cooker having the increased degree of freedom in the installation position of the power-receiver device200and the improved usability.

As the electric power can be transmitted even when the power transmission coil65and the power reception coil80are not arranged to face each other, a plurality of power transmission coils65need not be provided at respective positions at which the power-receiver device200is placed, and thus to obtain an inexpensive inductive heating cooker.

As the resonance frequency of the power transmission by magnetic resonance is largely different from the frequency of the coil current flowing through the heating coil11ato perform inductive heating, the power transmission from the main body100to the power-receiver device200is not affected by the magnetic field generated by the coil current flowing through the heating coil11a. The inductive heating of the heating target5and the power transmission to the power-receiver device200can be simultaneously performed.

In a case in which the electric power is transmitted using the electromagnetic induction coupling, for example, the frequency of the power transmission approximates the frequency of the coil current flowing through the heating coil11a. As a result, the interference occurs between the magnetic field of the power transmission using the electromagnetic induction coupling and the magnetic field generated from the heating coil11a, which may cause the malfunction. Consequently, in a case in which the electric power is transmitted using the electromagnetic induction coupling, it is difficult to simultaneously perform the inductive heating and the power transmission. Consequently, in a case in which the electric power is transmitted using the electromagnetic induction coupling, it is necessary to reduce the electric power to be input for the inductive heating or to temporarily stop the inductive heating.

On the other hand, in the inductive heating cooker of Embodiment 1, the electric power is transmitted by magnetic resonance, and consequently it is not necessary to reduce the electric power to be input for the inductive heating or to stop the inductive heating. Consequently, it is possible to obtain an inductive heating cooker with which food can be cooked in a short time and having the improved usability.

In a case in which the electric power is transmitted using the electromagnetic induction coupling, for example, significant reduction in the power transmission efficiency is caused when the displacement occurs between the position of the power transmission coil and the position of the power reception coil. Consequently, in the power transmission using the electromagnetic induction coupling, excessive current flows through the power transmission coil, which results in greater heat generation in the power transmission coil. When the positional displacement is further larger, the electric power cannot be transmitted to the power-receiver device.

On the other hand, in the inductive heating cooker of Embodiment 1, the electric power is transmitted by magnetic resonance, and consequently the electric power can be stably transmitted even when the displacement occurs between the position of the power transmission coil65and the position of the power reception coil80, that is, the power transmission coil65and the power reception coil80are not arranged to face each other.

In Embodiment 1, the power transmission coil65is provided to surround a plurality of heating units in a plan view. For example, the power transmission coil65is provided under the top plate4and along the edge of the top plate4.

Thus, a range can be increased in which one power transmission coil65is provided in an area of the top plate4in which the heating units are not provided. As the resonance frequency of the power transmission by magnetic resonance is largely different from the driving frequency of the heating coil11a, the power transmission from the main body100to the power-receiver device200is not affected by the magnetic field generated by the coil current flowing through the heating coil11aeven when the power transmission coil65is provided to surround the heating coil11a.

In a case in which the electric power is transmitted using the electromagnetic induction coupling, for example, the frequency of the coil current flowing through the heating coil approximates the frequency of the power transmission, and consequently the power transmission from the main body to the power-receiver device is more likely to be affected by the magnetic field generated by the coil current flowing through the heating coil. Consequently, in a case in which the electric power is transmitted using the electromagnetic induction coupling, it is necessary to provide the power transmission coil for the power transmission at a position at which the heating coil is not provided, thereby restricting the installation position of the power transmission coil.

On the other hand, in the inductive heating cooker of Embodiment 1, the electric power is transmitted by magnetic resonance, and consequently it is possible to alleviate restriction on an installation position of the power transmission coil65.

In Embodiment 1, the resonance frequency of the magnetic resonance is a frequency in a MHz band. For example, the driving frequency of the drive circuit50ranges from equal to or more than 20 kHz to less than 100 kHz, and the resonance frequency of the magnetic resonance is 6.78 MHz or a frequency that is an integral multiple of 6.78 MHz.

Thus, as the resonance frequency of the power transmission by magnetic resonance is largely different from the frequency of the coil current flowing through the heating coil11a, the power transmission from the main body100to the power-receiver device200is not affected by the magnetic field generated by the coil current flowing through the heating coil11a. Consequently, the electric power can be stably transmitted regardless of the magnitude of the coil current, that is, the magnitude of the electric power to be input.

The conductor (metal) placed on the top plate4is not inductively heated by the magnetic field generated from the power transmission coil65. Even when the metal cooker, for example, is placed on the top plate4, the metal cooker is not inductively heated by the magnetic field generated from the power transmission coil65.

As the resonance frequency of the magnetic resonance is extremely higher than the frequency of the high-frequency current flowing through the heating coil11a, the inductance of the power transmission coil65can be extremely smaller than that of the heating coil11a. Consequently, it is not necessary to provide a magnetic material such as ferrite to the power transmission coil65. Consequently, the size of the main body100can be reduced, thereby obtaining an inexpensive inductive heating cooker.

In Embodiment 1, the power-receiver device200includes the power-receiver communication device85configured to transmit the information on the temperature detected by the temperature sensor90configured to detect the temperature of the heating target5. The main body100includes the main-body communication device47configured to receive the information on the temperature transmitted from the power-receiver communication device85, and the control unit45configured to control the driving of the drive circuits50depending on the information on the temperature.

Thus, the restriction on an installation position of the temperature sensor90configured to detect the temperature of the heating target5can be alleviated, thereby increasing the degree of freedom in the installation position of the temperature sensor90to be placed on the top plate4. Consequently, the installation position of the temperature sensor90can be changed arbitrarily depending on, for example, the shape and size of the heating target5. Consequently, the usability can be improved.

Even when the temperature sensor90is made of a contact type sensor such as a thermistor, for example, and the power-receiver device200is provided to contact the side surface of the heating target5, the power transmission from the main body100to the power-receiver device200is not affected by the magnetic field generated by the coil current flowing through the heating coil11a.

Consequently, the temperature of the side surface of the heating target5can be directly detected by directly attaching the temperature sensor90to the side surface of the heating target5, and thus to obtain an inductive heating cooker with high temperature detection accuracy.

In a case in which the electric power is transmitted using the electromagnetic induction coupling, for example, when the power-receiver device is attached to the side surface of the metal heating target, the magnetic flux produced by the electromagnetic induction interlinks with the metal portion of the side surface of the heating target, thereby screening the magnetic field, so that the electric power cannot be transmitted.

On the other hand, in the inductive heating cooker of Embodiment 1, the electric power is transmitted by magnetic resonance, and consequently the power transmission is hardly affected by the metal portion of the heating target5, which enables the power transmission.

Modified Example 1

FIG. 7is a perspective view illustrating Modified Example 1 of power-receiver devices of the inductive heating cooker according to Embodiment 1.

As illustrated inFIG. 7, a configuration provided with a plurality of power-receiver devices200may be employed. In such a configuration, the plurality of power-receiver devices200each receive the electric power from one power transmission coil65.

The power-receiver control units83of the plurality of power-receiver devices200cause the respective temperature sensors90to transmit the information on the temperatures acquired from the respective temperature sensors90to the respective power-receiver communication devices85. The control unit45of the main body100acquires the information on the temperature from each of the plurality of power-receiver devices200, and controls driving of the drive circuits50using the information on a plurality of temperatures.

For example, the temperature sensors90of the plurality of the power-receiver devices200detect the temperature of one heating target5. The control unit45calculates the average temperature, the maximum temperature, or the minimum temperature on the basis of the received information on the plurality of temperatures, and controls the driving of the drive circuits50on the basis of the calculated values.

For example, a plurality of power-receiver devices200may be provided for the respective heating areas. The power-receiver control units83of the plurality of power-receiver devices200cause the respective temperature sensors90to transmit the identification information indicating the heating areas in addition to the information on the temperatures acquired from the respective temperature sensors90to the respective power-receiver communication devices85. The control unit45of the main body100acquires the information on the temperature from each of the plurality of power-receiver devices200together with the identification information. The control unit45acquires the temperatures of the heating targets5placed on the respective heating areas on the basis of the received information on the plurality of temperatures, and controls the driving of the drive circuits50of the respective heating units.

As described above, providing the plurality of power-receiver devices200each having the temperature sensor90enables the accuracy in detection of the temperature to be enhanced and the temperature variation of the heating target5to be reduced, and thus to obtain an inductive heating cooker with excellent usability. Also in a case in which the plurality of heating targets5are simultaneously heated, the temperature of each of the heating targets5can be simultaneously detected, and thus an inductive heating cooker with excellent usability can be obtained.

Modified Example 2

FIG. 8is a schematic diagram illustrating Modified Example 2 of a power-receiver device of the inductive heating cooker according to Embodiment 1.

As illustrated inFIG. 8, a vibration sensor90bmay be provided as a load circuit of a power-receiver device200. Note that the power-receiver device200may be provided with the vibration sensor90binstead of the above-described temperature sensor90, or may be provided with the vibration sensor90bin addition to the temperature sensor90.

The vibration sensor90bis operated by the electric power supplied from the power reception circuit81. The vibration sensor90bdetects the vibration from a measurement target.

Note that the vibration sensor90bcorresponds to the “load circuit” in the present invention.

In such a configuration, the power-receiver device200is provided to contact the side surface of the heating target5, so that the vibration sensor90bdetects the vibration of the heating target5. When the water in the heating target5is heated, and the water boils, for example, the vibration of the heating target5changes due to a burst of water bubbles. The vibration sensor90boutputs a voltage signal corresponding to the detected vibration to the power-receiver control unit83.

The power-receiver control unit83of the power-receiver device200causes the vibration sensor90bto transmit the information on vibration acquired from the vibration sensor90bto the power-receiver communication device85. The control unit45of the main body100controls driving of the drive circuits50using the information on the vibration acquired from the power-receiver device200.

When an amount of change in vibration detected by the vibration sensor90bexceeds a threshold, for example, the control unit45determines that the water in the heating target5has boiled. When the control unit45determines that the water has boiled, the control unit45controls the input heating power in such a manner that the input heating power is reduced. The control unit45may issue a notification on the display-and-operation unit43that the water has boiled.

Thus, providing the vibration sensor90benables the detection of boiling. The boiling state can be maintained even when the heating power to be input (electric power to be input) is reduced after boiling, and consequently the electric power to be input can be reduced. Reduction in the electric power to be input can decrease the wasteful consumption of electric power, and thus to obtain an inductive heating cooker that achieves electric power saving.

Modified Example 3

FIG. 9is a schematic diagram illustrating Modified Example 3 of a power-receiver device of the inductive heating cooker according to Embodiment 1.

As illustrated inFIG. 9, the power-receiver device200may be provided with a holding unit210configured to hold the power-receiver device200at the side surface of the heating target5.

As described above, comparing the power transmission using the magnetic resonance method (resonant coupling type) with the power transmission using the electromagnetic induction method (electromagnetic induction coupling type), the distance between the power transmission coil65and the power reception coil80can be increased.

Consequently, as illustrated inFIG. 9, the electric power can be transmitted even when the power-receiver device200is provided above the top plate4(to be lifted up from the top plate), and thus to obtain an inductive heating cooker with excellent usability.

In Embodiment 2, a configuration provided with a display-and-operation unit43serving as a load circuit of the power-receiver device will be described below.

Note that in the following description, the same parts as those of Embodiment 1 described above will be denoted by the same reference signs, and the differences from Embodiment 1 will be mainly described.

FIG. 10is an exploded perspective view illustrating a main body of an inductive heating cooker according to Embodiment 2.

FIG. 11is a perspective view illustrating the main body and a power-receiver device of the inductive heating cooker according to Embodiment 2.

FIG. 12is a block diagram illustrating a configuration of the main body and the power-receiver device of the inductive heating cooker according to Embodiment 2.

As illustrated inFIG. 10toFIG. 12, a main body101of the inductive heating cooker according to Embodiment 2 does not include the operation unit40, the display unit41, and the display-and-operation unit43configured in such a manner that the operation unit40and the display unit41are integrated. The other configurations of the main body101are similar to those of the main body100of Embodiment 1 described above.

A power-receiver device201of the inductive heating cooker according to Embodiment 2 includes the display-and-operation unit43serving as a load circuit.

The display-and-operation unit43of the power-receiver device201is operated by the electric power supplied from the power reception circuit81. The display-and-operation unit43is configured in such a manner that the operation unit40for receiving information on operation input to the main body101of the inductive heating cooker and the display unit41for displaying the information on the operation of the main body101are integrated. The other configurations of the power-receiver device201are similar to those of the power-receiver device200of Embodiment 1 described above.

Note that the operation unit40, the display unit41, and the display-and-operation unit43in Embodiment 2 each correspond to the “load circuit” in the present invention.

In such a configuration, the power-receiver control unit83causes the display-and-operation unit43to transmit the information on the input operation received by the display-and-operation unit43to the power-receiver communication device85. The information on this input operation is, for example, information on setting of heating power to be input (electric power to be input) and a cooking menu when the heating target5is heated.

The control unit45of the main body101controls the driving of the drive circuits50depending on the information on the input operation received by the main-body communication device47.

The control unit45transmits the display information on the operation of the main body101to the main-body communication device47. The power-receiver control unit83of the power-receiver device201causes the display-and-operation unit43to display the display information received by the power-receiver communication device85. This display information is, for example, information on setting of heating power to be input (electric power to be input) and a cooking menu when the heating target5is heated and information on the operation state.

As described above, in Embodiment 2, the power-receiver device201includes the display-and-operation unit43configured in such a manner that the operation unit40for receiving information on operation input to the main body101of the inductive heating cooker and the display unit41for displaying the information on the operation of the main body101are integrated.

Consequently, in addition to the effects of Embodiment 1 described above, it is possible to increase the degree of freedom in the installation position of the display-and-operation unit43and improve the usability.

Furthermore, the main body101does not include the operation unit40, the display unit41, and the display-and-operation unit43configured in such a manner that the operation unit40and the display unit41are integrated, thereby capable of simplifying the configuration of the main body101and achieving downsizing.

Note that in Embodiment 2, the configuration in which the power-receiver device201includes the display-and-operation unit43configured in such a manner that the operation unit40and the display unit41are integrated has been described, but the present invention is not limited to the configuration described above. Only one of the operation unit40and the display unit41may be provided in the power-receiver device201.

In Embodiment 2, the configuration in which the main body101does not include the operation unit40, the display unit41, and the display-and-operation unit43has been described, but the present invention is not limited to the configuration described above. Only one of the operation unit40and the display unit41may be provided in the main body101. Both the operation unit40and the display unit41may be provided in each of the main body101and the power-receiver device201. A part of the operation unit40and the display unit41may be provided.

Modified Example

FIG. 13is a perspective view illustrating Modified Example of a power-receiver device of the inductive heating cooker according to Embodiment 2.

As illustrated inFIG. 13, the main body101of the inductive heating cooker is installed in a kitchen300provided with, for example, a sink. A housing portion (not illustrated) to which the main body101of the inductive heating cooker is fitted is formed in the kitchen300, and a flat-plate shaped workboard301is provided on a top surface of the kitchen300. The top plate4of the inductive heating cooker is exposed from the workboard301in a state where the main body101of the inductive heating cooker is incorporated in the kitchen300. The workboard301of the kitchen300is made of insulating (non-metallic) materials such as wood, synthetic resin (for example, an artificial marble), and a stone material, for example.

In such a configuration, the power-receiver device201having the display-and-operation unit43may be placed on the workboard301of the kitchen300.

As the electric power is transmitted to the power-receiver device201from the main body101of the inductive heating cooker by magnetic resonance, the electric power can be transmitted even when the power transmission coil65and the power reception coil80are not arranged to face each other. As the workboard301is made of insulating materials, the power transmission coil65is not screened from the power reception coil80.

Consequently, the electric power can be transmitted from the main body101even when the power-receiver device201is placed on the workboard301. Consequently, the operation and display of the display-and-operation unit43can be performed in a state where the power-receiver device201is placed on the workboard301, thereby improving the usability of the inductive heating cooker.

In Embodiment 3, a configuration in which a heater is provided as a load circuit of the power-receiver device will be described below.

Note that in the following description, the same parts as those of Embodiment 1 described above will be denoted by the same reference signs, and the differences from Embodiment 1 will be mainly described.

FIG. 14is a schematic diagram illustrating a configuration of an inductive heating cooker according to Embodiment 3.

Note thatFIG. 14schematically illustrates a longitudinal section of the main body100and the power-receiver device202viewed from the fronts of the main body100and the power-receiver device202.

As illustrated inFIG. 14, the power-receiver device202of the inductive heating cooker according to Embodiment 3 includes an upper heater91serving as a load circuit.

The upper heater91is connected to the power reception coil80via the power reception circuit81(not illustrated). The upper heater91is made of a heating element that generates heat by the electric power received by the power reception coil80. For example, a sheathed heater serving as a resistance heating element is employed as the upper heater91. A specific configuration of the upper heater91is not limited to the one described above, and a given heating element such as a halogen heater and a far-infrared heater may be employed. The upper heater91is supported above the heating target5by a supporting unit220.

The supporting unit220is formed by a casing serving as an outer shell of the power-receiver device202, for example. The supporting unit220is formed to extend upward from the bottom portion that houses the power reception coil80and then extend horizontally, thereby having an L-shaped cross section. More specifically, the supporting unit220supports the upper heater91so that the upper heater91is located above the heating coil11aand the heating target5when the power-receiver device202is placed on the top plate4.

Note that when the power-receiver device202is placed on the top plate4, the distance between the top plate4and the upper heater91is set to be larger than the height of a pod or a frying pan considered as the heating target5. Note that the supporting unit220may be configured to move the upper heater91up and down.

Note that the upper heater91in Embodiment 3 corresponds to a “load circuit” in the present invention.

In such a configuration, the control unit45of the main body100operates the power transmission circuit60and causes the power transmission circuit60to start the supply of electric power to the power transmission coil65. The electric power is thereby supplied to the power reception coil80of the power-receiver device200from the power transmission coil65by magnetic resonance. The electric power received by the power reception coil80is supplied to the upper heater91from the power reception circuit81.

The upper heater91thereby heats food5bin the heating target5from above by thermal radiation. More specifically, the cooking by inductive heating and the cooking through non-contact power transmission can be simultaneously performed. Furthermore, the cooking by inductive heating and the cooking through non-contact power transmission are independently controllable. Consequently, it is possible to obtain an inductive heating cooker with which food can be nicely cooked in a short time. That is, with the drive circuits50and the power transmission circuit60, it is possible to independently control inductive heating with the heat from the heating target5and upper heating by the upper heater91, and thus to obtain an inductive heating cooker with which food can be nicely cooked in a short time.

In Embodiment 4, a configuration in which a stirring device is provided as a load circuit of the power-receiver device will be described below.

Note that in the following description, the same parts as those of Embodiment 1 described above will be denoted by the same reference signs, and the differences from Embodiment 1 will be mainly described.

FIG. 15is a schematic diagram illustrating a configuration of an inductive heating cooker according to Embodiment 4.

Note thatFIG. 15schematically illustrates a longitudinal section of the main body100and a power-receiver device203viewed from of the fronts of the main body100and the power-receiver device203.

As illustrated inFIG. 15, the power-receiver device203of the inductive heating cooker according to Embodiment 4 includes a stirring device92serving as a load circuit.

The stirring device92includes a motor92a, a shaft92b, and a blade unit92c. The stirring device92is supported above the heating target5by the supporting unit220. When the heating target5such as a pot and a frying pan, containing the food5b, such as stew and fried food, for example, is placed on one of the heating areas of the top plate4, the blade unit92cof the stirring device92is placed in the heating target5.

The motor92ais provided to an upper portion of the casing of the power-receiver device203, for example, and is driven for rotation by the electric power received by the power reception coil80. The shaft92bhas a rotary shaft disposed in the vertical direction, and has one end connected to the motor92ato transmit drive force of the motor92a. The blade unit92cis attached to the shaft92b, and stirs the food5bwith the shaft92bdriven for rotation.

Note that the stirring device92in Embodiment 4 corresponds to a “load circuit” in the present invention.

In such a configuration, the control unit45of the main body100operates the power transmission circuit60and causes the power transmission circuit60to start the supply of electric power to the power transmission coil65. The electric power is thereby supplied to the power reception coil80of the power-receiver device200from the power transmission coil65by magnetic resonance. The electric power received by the power reception coil80is supplied to the stirring device92from the power reception circuit81.

The cooking by induction heating and cooking by stirring through non-contact power transmission can thus be simultaneously performed. Furthermore, the cooking by induction heating and the cooking by stirring through non-contact power transmission are independently controllable. Consequently, it is possible to obtain an inductive heating cooker with which food can be nicely cooked in a short time.

Note that in Embodiments 1 to 4 described above, a configuration in which the power-receiver device has one type of load circuit has been described, but a plurality of load circuits of Embodiments 1 to 4 may be used in combination. That is, a plurality of power-receiver devices are provided, and at least one of the plurality of power-receiver devices may have a load circuit different from the load circuit each in other ones of the plurality of power-receiver devices.

The load circuit of the power-receiver device is not limited to the examples of Embodiments 1 to 4 described above, and may be a cooking device (a fryer, a steamer, a roaster, a toaster, and other devices) used for cooking the food, for example. Furthermore, the load circuit of the power-receiver device may be the cooking device (a blender, a mixer, a mill, a beater, a food processor, and other devices) used for preparing and precooking the food, for example. Moreover, the load circuit of the power-receiver device may be a component detection sensor for detecting components (for example, salinity, sugar content, and other components), the component detection sensor being disposed in the heating target5.

FIG. 16is a diagram illustrating a top plate and a power transmission coil of an inductive heating cooker according to Embodiment 5.

FIG. 16(a)is a plan view of the top plate4when the top plate4is seen from the back, andFIG. 16(b)is a side view of the top plate4.

As illustrated inFIG. 16, the power transmission coil65may be provided on the back surface (bottom surface) of the top plate4. For example, the power transmission coil65may be provided on the back surface of the top plate4by printed wiring.

With such a configuration, the main body100can be miniaturized. The assembling process of the main body100can be facilitated, and thus to obtain an inexpensive inductive heating cooker.

REFERENCE SIGNS LIST