INDUCTION HEATING DEVICE

Abstract

 An induction heating device of the present disclosure includes a top plate 13 on which an object to be heated is placed, a plurality of heating coils 11 which are disposed below the top plate, an inverter 16 which supplies a high frequency current to the plurality of heating coils, a control unit 17 which controls an output of the inverter, and a determination unit 18 for the object to be heated which determines a state of the object to be heated. The determination unit 18 for the object to be heated detects the heating coils which correspond to an area in which the object to be heated is placed, and determines that the one object to be heated is placed in the area formed by the heating coils detected in a determination time period of the detected heating coils.

Description

Technical Field

[0001] The present disclosure relates to an induction heating device. The present disclosure relates particularly to an induction heating device which executes an induction heating to an object to be heated such as a metal cooking pan placed on a top plate.

Background Art

[0002] A generally used induction heating cooking device is, as an induction heating device, configured to have, for example, one or two heating coil(s) disposed immediately below a top plate and execute an induction heating to an object to be heated such as a metal cooking pan etc. placed on the top plate using the heating coil(s).

[0003] For the induction heating cooking device, a multi-coil configuration has been proposed that has many heating coils arranged immediately below the top plate (see, e.g., Patent Literature 1).

[0004] The heating cooking device described in Patent Literature 1 is configured to have many heating coils which are disposed each adjacent to each other densely arranged below the top plate, and be able to execute an induction heating to a cooking pan which is an object to be heated even when the object to be heated is placed at any position on the top plate.

[0005] The multi-coil configuration to heat the object to be heated such as a cooking pan using many coils is also described in, for example, Patent Literature 2.

[0006] The heating cooking device described in Patent Literature 2 is configured to supply an AC signal in a radio frequency band to each heating cell and detect an induction signal in a conductive loop positioned between the object to be heated and the heating cell. The induction signal is varied by the presence of the object to be heated, and the position of the object to be heated placed on the top plate can therefore be detected.

Citation List

Patent Literature

[0007] 

PLT 1: DE 102010028549 A1

PLT 2: EP 1206164 B1

Summary of Invention

Technical Problem

[0008] As above, the heating cooking device described in Patent Literature 1 is configured to be able to execute the induction heating to the object to be heated even when the object to be heated is placed at any position on the top plate while the number of heating coils necessary for heating one object to be heated is unknown. The heating cooking device disclosed in Patent Literature 2 can detect whether an object to be heated is placed above each of the heating coils while this heating cooking device cannot determine the number, etc., of objects to be heated. With the traditional induction heating device, a problem arises that the control cannot properly be executed for heating the object to be heated.

[0009] An object of the present disclosure is to provide an induction heating device of the multi-coil configuration having the plurality of heating coils which are disposed below the top plate, that can properly execute its control to heat objects to be heated by determining the number, the size, and/or the shape, etc., of the objects to be heated placed on the top plate.

Solution to Problem

[0010] In order to solve the above problems, an induction heating device of one aspect according to the present disclosure includes:

a top plate on which an object to be heated is placed;

a plurality of heating coils which are disposed below the top plate;

an inverter which supplies a high frequency current to the plurality of heating coils;

a control unit which controls an output of the inverter; and

a determination unit for the object to be heated which determines a state of the object to be heated which is placed on the top plate,

wherein the determination unit for the object to be heated detects the heating coils which correspond to an area in which the object to be heated is placed, and determines a state of the object to be heated to be a state where the one object to be heated is placed in an area formed by the heating coils which are detected in a determination time period for determining the state of the object to be heated of the detected heating coils, and

wherein the control unit controls supply of electric power to the heating coils corresponding to the area in which the object to be heated is placed based on the state of the object to be heated which is determined by the determination unit for the object to be heated.

[0011] When the determination unit for the object to be heated detects the heating coils in the area in which the object to be heated is placed, the determination unit for the object to be heated determines that one object to be heated is placed in the area formed by one, or plural adjacent heating coil(s) detected during a specific time period (the determination time period). When the determination unit for the object to be heated further detects the heating coils after the specific time period (the determination time period) elapses therefrom, the determination unit for the object to be heated determines that another object to be heated other than the object to be heated determined in the previous specific time period (the determination time period) is placed. Plural determination time periods are present and the determination unit for the object to be heated determines that another new object to be heated is placed in an area formed by the heating coils newly detected during each of the determination time periods.

Advantageous Effects of Invention

[0012] The induction heating device of the present disclosure can determine that a second object to be heated which is placed after the specific time period elapses from placement of a first object to be heated is another cooking pan. Therefore, the induction heating device of the present disclosure can execute control of the heating for a desired object to be heated such as starting of the heating. The induction heating device of the present disclosure has the multi-coil configuration having the plurality of heating coils which are disposed below the top plate. The induction heating device of the present disclosure can properly execute the control of heating for objects to be heated by determining the number, the size, and/or the shape, etc., of the objects to be heated placed on the top plate.

Brief Description of Drawings

[0013] 

Fig. 1 is a schematic plan diagram of an induction heating device according to a first embodiment of the present disclosure.

Fig. 2 is a vertical cross-sectional diagram of the induction heating device cut off along an A-A line in Fig. 1.

Fig. 3 is a block diagram of a configuration of the induction heating device according to the first embodiment of the present disclosure.

Fig. 4 is a diagram of a circuit configuration of the induction heating device according to the first embodiment of the present disclosure.

Fig. 5 is an explanatory diagram of a relation between an input current from a power source and an output voltage generated in an inverter of the induction heating device according to the first embodiment of the present disclosure.

Fig. 6 is a time chart of a determination operation for an object to be heated executed when the heating coils corresponding to an area in which the object to be heated is placed are detected by a determination unit for the object to be heated of the induction heating device according to the first embodiment of the present disclosure.

Fig. 7 is a diagram of a content of display on an operation display unit of the induction heating device according to the first embodiment of the present disclosure.

Fig. 8 is a time chart of a determination operation for an object to be heated executed when the heating coils corresponding to an area in which the object to be heated is placed are detected by the determination unit for the object to be heated of an induction heating device according to a second embodiment of the present disclosure.

Fig. 9 is a time chart of a determination operation for an object to be heated executed when the heating coils corresponding to an area in which the object to be heated is placed are detected by the determination unit for the object to be heated of an induction heating device according to a third embodiment of the present disclosure.

Fig. 10 is a diagram of a content of display on the operation display unit of an induction heating device according to the third embodiment of the present disclosure.

Fig. 11 is a schematic plan diagram of a state where objects to be heated are placed on an induction heating device according to a fourth embodiment of the present disclosure.

Fig. 12 is a schematic plan diagram of the state where another object to be heated is placed on the induction heating device according to the fourth embodiment of the present disclosure.

Description of Embodiments

[0014] An induction heating device of a first aspect according to the present disclosure includes:

a top plate on which an object to be heated is placed;

a plurality of heating coils which are disposed below the top plate;

an inverter which supplies a high frequency current to the plurality of heating coils;

a control unit which controls an output of the inverter; and

a determination unit for the object to be heated which determines a state of the object to be heated which is placed on the top plate,

wherein the determination unit for the object to be heated detects the heating coils which correspond to an area in which the object to be heated is placed, and determines a state of the object to be heated to be a state where the one object to be heated is placed in an area formed by the heating coils which are detected in a determination time period for determining the state of the object to be heated of the detected heating coils, and

wherein the control unit controls supply of electric power to the heating coils corresponding to the area in which the object to be heated is placed based on the state of the object to be heated which is determined by the determination unit for the object to be heated.

[0015] According to this configuration, the state of the object to be heated placed on the top plate can be determined, and control for the heating can therefore be executed only for the heating coils corresponding to the area in which the object to be heated is placed. For example, the number, etc., of objects to be heated can be determined by determining whether any object to be heated is placed on the top plate within the determination time period. The control can therefore be executed to heat only the desired object to be heated.

[0016] An induction heating device of a second aspect according to the present disclosure further includes an operation display unit which displays a result of the determination by the determination unit for the object to be heated according to the first aspect and outputs an operation command to the control unit,
wherein the control unit controls the supply of the electric power to the heating coils based on the operation command which is output from the operation display unit.

[0017]  According to this configuration, the state of the object to be heated can be displayed on the operation display unit, and the operation command to heat the object to be heated can be output. The induction heating device can be provided that is usable for the user.

[0018] In an induction heating device of a third aspect according to the present disclosure, the determination unit for the object to be heated according to the first or second aspect has a plurality of determination time periods, and
wherein the determination unit for the object to be heated determines that another new object to be heated is placed in an area formed by the heating coils newly detected in each of the determination time periods.

[0019] According to this configuration, when the determination unit for the object to be heated detects the heating coils in the area in which the object to be heated is placed, the determination unit for the object to be heated determines that one object to be heated is placed in the area formed by one, or plural adjacent heating coil(s) detected during the specific time period (the determination time period). When the determination unit for the object to be heated further detects other heating coils after the specific time period (the determination time period) elapses therefrom, the determination unit for the object to be heated determines that another object to be heated other than the object to be heated determined in the previous specific time period (the determination time period) is placed. The determination unit for the object to be heated can therefore determine the state of the object to be heated such as whether the object to be heated is placed on the top plate during each determination time period, and the control of the heating can therefore be executed only for the desired object to be heated.

[0020] In an induction heating device of a fourth aspect according to the present disclosure, the determination time period according to any one of the first to third aspects is started from a time point at which the heating coils corresponding to the area in which the object to be heated is placed are detected by the determination unit for the object to be heated.

[0021] According to this configuration, the determination time period is started when the heating coils are detected that correspond to the area in which the object to be heated is placed and, thereby, the state of the object to be heated can be determined at a proper timing.

[0022] When the object to be heated is moved after the determination of the state of the object to be heated, the determination unit for the object to be heated can update and then determine the state of the object to be heated. When the object to be heated is moved, the determination unit for the object to be heated does not detect the heating coils corresponding to the position at which the object to be heated is already not placed. The determination unit for the object to be heated detects the heating coils that correspond to the position at which the object to be heated is newly placed, and starts the determination time period. During this determination time period, the determination unit for object to be heated determines that one object to be heated is placed in an area formed by the newly detected heating coils and, the already detected heating coils of the heating coils adjacent to the newly detected heating coils, during this determination time period.

[0023] In an induction heating device of a fifth aspect according to the present disclosure, the determination time period according to any one of the first to third aspects having a specific time period is repeated.

[0024] According to this configuration, the configuration of the determination unit for the object to be heated can be simplified and the state of the object to be heated can easily be determined.

[0025] In an induction heating device of a sixth aspect according to the present disclosure, the determination unit for the object to be heated according to any one of the first to fifth aspects determines number of objects to be heated from number of areas each formed by the heating coils which are detected in the determination time period.

[0026] According to this configuration, the determination unit for the object to be heated can determine the number of objects to be heated based on the number of areas formed by the detected heating coils, and the control can therefore be executed to heat only a desired object to be heated.

[0027] In an induction heating device of a seventh aspect according to the present disclosure, the determination unit for the object to be heated according to any one of the first to sixth aspects determines a size and/or a shape of the object to be heated from a size and/or a shape of the area formed by the heating coils which are detected in the determination time period.

[0028] According to this configuration, the control can be executed to heat only a desired object to be heated based on the size and/or the shape of the object to be heated.

[0029] An induction heating device of an eighth aspect according to the present disclosure further includes a light emitting unit which is disposed around each of the plurality of heating coils according to any one of the first to seventh aspects, the light emitting unit visually observably lighting through the top plate,
wherein the light emitting unit is configured to indicate by lighting a circumference of the area formed by the heating coils which correspond to at least the area in which the object to be heated is placed.

[0030] According to this configuration, the area intended for the heating operation and/or the currently heated area can be checked by visual observation and any erroneous operation is caused to be difficult for the user.

[0031] Embodiments according to the present disclosure are described for their operations and actions with reference to the drawings. The present disclosure is not limited to the embodiments. In all the drawings below, the same or the corresponding parts are given the same reference numerals and are not described again.

(First Embodiment)

[Overall Configuration]

[0032] Fig. 1 is a schematic plan diagram of an induction heating device according to the first embodiment of the present disclosure, and schematically shows the main elements in the present disclosure. Fig. 2 is a vertical cross-sectional diagram of the induction heating device cut off along an A-A line in Fig. 1. Fig. 3 is a block diagram of a configuration of the induction heating device according to the first embodiment.

[0033] As shown in Figs. 1 to 3, the induction heating device 10a according to the first embodiment includes a top plate 13, a plurality of heating coils 11 arranged in lines and disposed below the top plate 13, an inverter 16 which supplies a high frequency current to the heating coils 11, and a control unit 17 which controls the output of the inverter 16. The induction heating device 10a further includes a determination unit 18 for an object to be heated that determines the state of the object to be heated (such as the number, the size, and/or the shape, etc., of the object to be heated) and an operation display unit 12 which displays the result of the determination by the determination unit 18 for the object to be heated and that outputs an operation command to the control unit 17.

[0034] Elements included in the induction heating device 10a according to the first embodiment are described in detail.

[Top Plate]

[0035] The induction heating device 10a according to the first embodiment includes the flat-board top plate 13 in the upper portion thereof. As shown in Fig. 1, a first object 14 to be heated and a second object 15 to be heated such as cooking pans are placed on the top plate 13. The top plate 13 includes an electric insulator such as glass or ceramic.

[Heating Coils]

[0036] The heating coils 11 are in a multi-coil configuration including a plurality of heating coils. The plurality of heating coils 11 are disposed below the top plate 13 arranged in a matrix at predetermined intervals. For example, as shown in Fig. 1, the induction heating device 10a of the first embodiment may be configured to have the plurality of heating coils 11 disposed therein having each five thereof longitudinally arranged and each nine thereof laterally arranged. In the first embodiment, lines of the heating coils 11 are referred to as "a" to "e" rows sequentially from the row of the heating coils 11 close to the operation display unit 12 in Fig. 1, and columns thereof are referred to as "a" to "i" columns sequentially from the column on the left in the induction heating device 10a of Fig. 1. In the first embodiment, therefore, the plurality of heating coils 11 are denoted by reference numerals of the heating coils 11aa to 11ei. Similar reference numerals are attached to the heating coils 11 in the following description. All the heating coils 11 have the substantially same shape and the substantially same configuration. The heating coils 11 execute an induction heating operation in the induction heating device 10a according to the first embodiment.

[Inverter]

[0037] The inverter 16 is connected to the plural heating coils 11. The inverter 16 supplies the high frequency current to each of the plural heating coils 11. The induction heating device 10a of the first embodiment may be configured to include plural inverters 16 each corresponding to the plural heating coils 11 and each connected to any one thereof. For example, as shown in Fig. 2, the induction heating device 10a of the first embodiment may include inverters 16aa to 16ei connected respectively to the heating coils 11aa to 11ei. Otherwise, a configuration, etc., are present to collectively connect some of the heating coils 11 to any one of the inverters 16. Additionally, there is a configuration which switches the inverters 16 to connect to the heating coils 11 requiring a power feeding.

[Control Unit]

[0038] The control unit 17 is connected to the inverter 16, the operation display unit 12, and the determination unit 18 for the object to be heated. For example, the control unit 17 receives an instruction in an operation command from the operation display unit 12 and controls the output of the inverter 16. The control unit 17 may receive a result of the determination of the object to be heated from the determination unit 18 for the object to be heated, and may control the output of the inverter 16. The control unit 17 may produce information necessary for its heating control operation based on the result of the determination by the determination unit 18 for the object to be heated, and may output the produced information to the operation display unit 12. The "information necessary for the heating control" is, for example, the position at which the object to be heated is placed, etc., in addition to the number, the size, and/or the shape, etc., of the object to be heated.

[Operation Display Unit]

[0039] The operation display unit 12 is disposed at the center on the user side (the lower side in Fig. 1) on the top plate 13, and is configured to be usable for the user. The position of the operation display unit 12 is not limited to the position shown in Fig. 1, and the operation display unit 12 may be disposed at an arbitrary position only when the operation display unit 12 is configured to be usable thereat.

[0040] The operation display unit 12 is connected to the control unit 17. The operation display unit 12 outputs to the control unit 17 an operation command signal for indicating the start or discontinuation of the supply of the electric power, electric power adjustment, etc. For example, when the first object 14 to be heated such as a cooking pan is placed on the top plate 13, the operation display unit 12 outputs to the control unit 17 an operation command signal for indicating the start of the heating operation, based on an operation by the user.

[0041] For example, when the control unit 17 receives the result of the determination for the object to be heated from the determination unit 18 for the object to be heated, the operation display unit 12 may receive a signal concerning the display of the object to be heated from the control unit 17 and may display the information necessary for the heating control operation (for example, the number or the size, etc., of the object to be heated).

[Determination Unit for Object to Be Heated]

[0042] The determination unit 18 for the object to be heated is connected to the inverter 16 and the control unit 17. For example, in order to detect the object to be heated, a current detecting unit and/or a voltage detecting unit detect(s) an input current flowing through and/or an output voltage generated in an electrically conductive path for electric power transmission from a power source to the heating coils 11 such as the inverter 16. The determination unit 18 for the object to be heated grabs the state of the object to be heated magnetically coupled with the heating coils 11 such as whether any object to be heated such as a cooking pan is placed above the heating coils 11 that are currently energized, based on the detected value(s) of the input current and/or the output voltage. The determination unit 18 for the object to be heated detects the heating coils 11 that correspond to the area in which the object to be heated is placed. The "heating coils 11 that correspond to the area in which the object to be heated is placed" are, for example, the heating coils 11 immediately below the object to be heated. For example, the result of the detection for the object to be heated, that is, the result of the detected heating coils 11 may be output to the control unit 17 as a signal.

[0043] The determination unit 18 for the object to be heated determines the number of objects to be heated such as whether one object to be heated or two objects to be heated is/are placed on the top plate, or the size and/or the shape of the object(s) to be heated, based on the detected heating coils 11.

[0044] The determination unit 18 for the object to be heated can output at least the determination result for the object(s) to be heated to the control unit 17. Thereby, the control unit 17 can properly control the heating corresponding to the number, the size, and/or the shape of the object(s) to be heated.

[0045] When the heating is controlled for each of the heating coils 11 based on the detection result for each of the heating coils 11, the determination unit 18 for the object to be heated may output the detection result for the heating coils 11 to the control unit 17 at a time point at which the determination unit 18 for the object to be heated detects the heating coils 11 that correspond to the area in which the object to be heated is placed.

[0046] As above, according to the induction heating device 10a of the first embodiment, when the first object 14 to be heated and the second object 15 to be heated are placed on the top plate 13, the heating operation is executed in the area of the placement.

[0047] For example, as shown in Fig. 1, when the first object 14 to be heated is placed on the top plate 13, a proper induction heating operation is executed for the first object 14 to be heated by supplying the high frequency current to the heating coils 11bb, 11bc, 11cb, and 11cc that are present below the first object 14 to be heated.

[0048] As shown in Fig. 1, when the second object 15 to be heated is placed on the top plate 13, another proper induction heating operation is executed for the second object 15 to be heated by supplying the high frequency current to the heating coils 11bd, 11cd, 11be, and 11ce that are present below the second object 15 to be heated.

[Detection Method for Object to Be Heated]

[0049] The detection operation for the first object 14 to be heated is described that is executed when the first object 14 to be heated such as a cooking pan is placed on the top plate 13 of the induction heating device 10a according to the first embodiment.

[0050] Fig. 4 shows an example of the circuit configuration of the induction heating device 10a according to the first embodiment of the present disclosure. Fig. 5 shows the relation between the input current and the output voltage for the determination unit 18 for the object to be heated to determine, in the circuit configuration shown in Fig. 4.

[0051] Fig. 4 shows the circuit of the induction heating device 10a constituted by the heating coils 11, the inverter 16, the control unit 17, the determination unit 18 for the object to be heated, the AC power source 40, the current detecting unit 48, and the voltage detecting unit 49. The inverter 16 includes a diode bridge 41, a choke coil 42, a smoothing capacitor 43, a first switching element 44, a second switching element 45, a resonance capacitor 46, and a snubber capacitor 47.

[0052] In the circuit configuration shown in Fig. 4, in order to convert an AC into a DC to be smoothed, the power source 40 is connected to the diode bridge 41, the choke coil 42, and the smoothing capacitor 43. To supply the high frequency current to the heating coils 11, such elements are connected in series between the ends of the smoothing capacitor 43 as the first switching element 44 including a reverse conductive diode and the second switching element 45 also including a reverse conductive diode.

[0053] The second switching element 45 is connected in parallel to the resonance capacitor 46 to cause a current resonance with the heating coils 11, and the snubber capacitor 47 to reduce the switching loss generated when the first switching element 44 and the second switching element 45 are each turned off.

[0054] The circuit configuration shown in Fig. 4 further includes the current detecting unit 48 for detecting the input current Iin supplied from the power source 40 to the inverter 16, and the voltage detecting unit 49 for detecting the output voltage Vc that is the voltage between the ends of the resonance capacitor 46 in the inverter 16. The detected values of the current detecting unit 48 and the voltage detecting unit 49 are output to the determination unit 18 for the object to be heated.

[0055] In Fig. 5, the detected values of the input current Iin and the output voltage Vc can be plotted on a coordinate plane whose axis of abscissa represents the current Iin and whose axis of ordinate represents the voltage Vc based on the detected values of the input current Iin detected by the current detecting unit 48 and the output voltage Vc detected by the voltage detecting unit 49. Fig. 5 is an explanatory diagram of the relation between the input current Iin from the power source 40 and the output voltage Vc generated in the inverter 16 of the induction heating device 10a according to the first embodiment of the present disclosure.

[0056] For example, the induction heating device 10a of the first embodiment can set conditions for maintaining the input voltage of the power source 40 to be constant in the circuit configuration shown in Fig. 4, and for the determination unit 18 for the object to be heated to detect the presence of the object to be heated when the object to be heated is placed in an area which is equal to or larger than 50% of a heating area of a surface facing the top plate 13 of one of the heating coils 11 (the heating area of the upper surface of the heating coil 11). For the induction heating device 10a of the first embodiment, in the case where the driving variables such as the operation frequency or the duty, etc., of each of the first switching element 44 and the second switching element 45 are varied under this condition, when the detected values of the input current Iin and the output voltage Vc (the voltage between the ends of the resonance capacitor 46) have a correlation to mutually influence each other, a threshold value curved line L shown in Fig. 5 can be depicted by connecting the detected values. The induction heating device 10a of the first embodiment may set the condition such that the presence of the object to be heated is detected, for example, when the object to be heated is placed in an area which is equal to or larger than 40% of the heating area of the upper surface of the heating coil 11. The induction heating device 10a of the first embodiment can arbitrarily set the condition for detecting the presence of the object to be heated.

[0057]  The threshold value curved line L represents a boundary between the state where the heating coil 11 can heat the object to be heated (the state where the object to be heated is present above the heating coil 11) and the state where the heating coil 11 cannot heat the object to be heated (the state where no object to be heated is present above the heating coil 11). On the coordinate plane shown in Fig. 5, an "AREA 1" (an area depicted on the right of the threshold value curved line L) represents the state where the heating coil 11 can heat the object to be heated, and an "AREA 2" (an area depicted on the left of the threshold value curved line L) represents the state where the heating coil 11 cannot heat the object to be heated.

[0058] For example, when no object to be heated is placed above the heating coil 11, the output voltage Vc is increased relatively to the input current Iin. The threshold value curved line L is therefore drawn on the boundary between the state where the heating coil 11 can heat the object to be heated and the state where the heating coil 11 cannot heat the object to be heated, and it can be determined that the heating can be executed (the object to be heated is present) when the detected values of the input current Iin and the output voltage Vc are in the "AREA 1" in Fig. 5, and it can be determined that the heating cannot be executed (no object to be heated is present) when the detected values are in the "AREA 2".

[0059] The detection method for the object to be heated (the method of detecting the heating coils 11 that correspond to the area in which the object to be heated is placed) is not limited to the above and, for example, any method may be employed as the detection method for the object to be heated only when another method is present that enables the detection of whether any object to be heated is placed above the heating coils 11.

[Determination Method for Object to Be Heated]

[0060] A determination method for the number, etc., of objects to be heated is described for the case where the first object 14 to be heated and the second object 15 to be heated such as cooking pans are placed on the top plate 13 of the induction heating device 10a according to the first embodiment.

[0061] Fig. 6 shows a time chart of a determination operation for the object to be heated executed when the heating coils 11 corresponding to the area in which the object to be heated is placed are detected by the determination unit 18 for the object to be heated of the induction heating device 10a according to the first embodiment of the present disclosure.

[0062] Fig. 7 is a diagram of a content of the display on the operation display unit 12 of the induction heating device 10a in the first embodiment of the present disclosure. Fig. 7 shows an example of a diagram displayed on the operation display unit 12 based on the result of the determination by the determination unit 18 for the object to be heated.

[0063] When no object to be heated is placed on the top plate 13, the detected values of the input current Iin and the output voltage Vc detected by the current detecting unit 48 and the voltage detecting unit 49 are positioned in the "AREA 2" shown in Fig. 5. Based on this detection result, the determination unit 18 for the object to be heated determines that no object to be heated is present above the heating coils 11 ("NO OBJECT TO BE HEATED" in Fig. 6).

[0064] When the first object 14 to be heated is placed in the area shown in Fig. 1, the detection of the object to be heated is executed by the four heating coils 11bb, 11cb, 11bc, and 11cc disposed below the first object 14 to be heated. The detected values of the input current Iin by the current detecting unit 48 and the output voltage Vc by the voltage detecting unit 49 are positioned in the "AREA 1" of Fig. 5, and the determination unit 18 for the object to be heated determines that the object to be heated is present (OBJECT TO BE HEATED PRESENT in Fig. 6). The heating coils 11bb, 11cb, 11bc, and 11cc are detected that correspond to the area in which the first object 14 to be heated is placed.

[0065] The reason why the detection timings of the four heating coils 11bb, 11cb, 11bc, and 11cc disposed below the first object 14 to be heated are shifted from each other is that, for example, when the first object 14 to be heated is placed not in parallel to the flat surface of the top plate 13, the detection is executed starting from the point at which the distance is short between the first object 14 to be heated and the heating coil 11 below the top plate 13.

[0066] The detection timings for the object to be heated are also naturally shifted from each other when the detection operation for the object to be heated is intermittently executed and the adjacent heating coils 11 do not concurrently execute the detection operation for the object to be heated.

[0067] When the first object 14 to be heated is placed on the top plate 13 as shown in Fig. 1, the determination unit 18 for the object to be heated first determines that the object to be heated is present for the heating coil 11bb as shown in Fig. 6. Thereafter, the determination unit 18 for the object to be heated sequentially determines that the object to be heated is present for the heating coils 11cb, 11bc, and 11cc. The heating coils 11bb, 11cb, 11bc, and 11cc are sequentially detected that correspond to the area in which the first object 14 to be heated is placed. Using the fact as a trigger that it is first determined for the heating coil 11bb that the object to be heated is present, the determination unit 18 for the object to be heated starts a determination time period Tc1 to determine the number, etc., of the objects to be heated. The determination time period Tc1 is started when the determination unit 18 for the object to be heated detects the heating coil 11 present immediately below the object to be heated.

[0068] The determination unit 18 for the object to be heated determines that the first object 14 to be heated is one object to be heated, that is placed above the heating coils 11bb, 11cb, 11bc, and 11cc for which "OBJECT TO BE HEATED PRESENT" is determined during the determination time period Tc1. The determination unit 18 for the object to be heated determines that one object to be heated is placed in the area formed by the heating coils 11bb, 11cb, 11bc, and 11cc for which "OBJECT TO BE HEATED PRESENT" is detected during the determination time period Tc1. Thereafter, the result of the determination by the determination unit 18 for the object to be heated is output to the control unit 17.

[0069] The second object 15 to be heated is placed on the top plate 13 as shown in Fig. 1. Similarly to the case where the first object 14 to be heated is placed, the determination unit 18 for the object to be heated determines "OBJECT TO BE HEATED PRESENT" sequentially for the heating coils 11bd, 11cd, 11 be, and 11ce as shown in Fig. 6. Using the fact as a trigger that it is first determined for the heating coil 11bd that the object to be heated is present, the determination unit 18 for the object to be heated starts a determination time period Tc2. The determination unit 18 for the object to be heated determines that the second object 15 to be heated is one object to be heated, that is placed above the heating coils 11bd, 11cd, 11be, and 11ce for which "OBJECT TO BE HEATED PRESENT" is determined during the determination time period Tc2. The determination unit 18 for the object to be heated determines that one object to be heated is placed in the area formed by the heating coils 11bd, 11cd, 11be, and 11ce detected during the determination time period Tc2. Thereafter, the result of the determination by the determination unit 18 for the object to be heated is output to the control unit 17.

[0070] The determination time periods Tc1 and Tc2 are each the time period for the determination unit 18 for the object to be heated to determine the state (such as the number, the size, or the shape, etc.) of the object to be heated based on the area formed by the detected heating coils 11. The lengths of the determination time periods Tc 1 and Tc2 may be same or may be different from each other. The determination time periods Tc 1 and Tc2 each only have to be a time period during which the detection for the object to be heated can be executed for at least all the heating coils 11, or may be a time period longer than this. For example, the induction heating device 10a of the first embodiment is set to start the determination time period Tc1 using the fact as a trigger that it is first determined for the heating coil 11 that the object to be heated is present, and end the determination time period Tc1 after the detection operation is executed for at least all the heating coils 11. When it is securely determined that the object to be heated is present after plural detection sessions are executed determining that the object to be heated is present for the heating coils 11 to prevent any false detection of the object to be heated, the determination unit 18 for the object to be heated may be set to end the determination time period Tc1 after two or more detecting operations are executed each for all the heating coils 11.

[0071]  The induction heating device 10a cannot determine the number, the size, and/or the shape etc., of the object to be heated by visual observation as the user can. For example, the determination unit 18 for the object to be heated may therefore determine that the object to be heated is one object to be heated, that is placed above the heating coils 11 detected during a specific time period after the first detection of the object to be heated by the determination unit 18 for the object to be heated and, thereby, may determine the number, the size, or the shape, etc., of the object to be heated. For example, the determining unit 18 for objects to be heated detects the heating coils 11 corresponding to the area in which the object to be heated is placed, that is, the heating coils 11 present immediately below the object to be heated during the determination time period Tc1, and determines that one object to be heated is placed in the area formed by these detected heating coils 11. The determination unit 18 for the object to be heated next determines that another object to be heated is placed in the area formed by the heating coils 11 newly detected during the determination time period Tc2. In this manner, the number, etc., of the objects to be heated may be determined by determining that another new object to be heated is placed in the area formed by the heating coils newly detected in each determination time period.

[0072] In Fig. 6, the second object 15 to be heated is first detected by the heating coil 11bd at a timing delayed by the specific time period (the determination time period Tc1) from the time when the first object 14 to be heated is first detected by the heating coil 11bb. It can therefore be determined that the second object 15 to be heated is an object to be heated different from the first object 14 to be heated.

[0073] Even when plural objects to be heated are simultaneously placed on the top plate 13, the determination unit 18 for the object to be heated can determine the number, the size, or the shape, etc., of the object(s) to be heated based on the number or the size of the area(s) formed by the adjacent heating coils 11 of the detected heating coils 11. The case is described where the first object 14 to be heated is placed above the heating coils 11bb, 11cb, 11bc, and 11cc and the second object 15 to be heated is placed above the heating coils 11 ah, 11bh, 11ai, and 11bi in the configuration shown in Fig. 1. In this case, the placement of the objects to be heated is detected by the heating coils 11bb, 11cb, 11bc, 11cc, 11ah, 11bh, 11ai, and 11bi during the determination time period Tc1, and "OBJECT TO BE HEATED PRESENT" is determined for each of these heating coils. The determination unit 18 for the object to be heated determines that one object to be heated is present in an area formed by the heating coils 11bb, 11cb, 11bc, and 11cc for which "OBJECT TO BE HEATED PRESENT" is determined and one object to be heated is also present in an area formed by the heating coils 11 ah, 11bh, 11ai, and 11bi. Even when plural objects to be heated are simultaneously placed on the top plate 13, the determination unit 18 for the object to be heated can determine the number, the size, or the shape, etc., of the object(s) to be heated based on the number or the size of the area(s) formed by the one or the adjacent plural heating coils 11 for which "OBJECT TO BE HEATED PRESENT" is determined. The determination unit 18 for the object to be heated can also determine the number, the size, or the shape, etc., of each of the plural objects to be heated during the determination time period Tc1.

[0074] Based on the determination result output from the determination unit 18 for the object to be heated, the control unit 17 outputs to the operation display unit 12 information on the number, the size, and the shape of the objects to be heated placed on the top plate 13 or the positions, etc., at which the objects to be heated are placed.

[0075] Fig. 7 shows an example of the display on the operation display unit 12 displayed when the first object 14 to be heated and the second object 15 to be heated are placed on the top plate 13.

[0076] As shown in Fig. 7, the operation display unit 12 displays thereon, for example, display 31 corresponding to the first object 14 to be heated shown in Fig. 1 and display 32 corresponding to the second object 15 to be heated shown in Fig. 1. The operation display unit 12 has the two pieces of display present thereon that are the display 31 and the display 32, and the fact can therefore be easily determined that the number of objects to be heated is two. The sizes, the shapes, the positions for placement on the top plate 13 of the first object 14 to be heated and the second object 15 to be heated can easily be determined based on the sizes, the shapes, and the positions of the display 31 and the display 32 displayed on the operation display unit 12.

[0077] As above, the objects to be heated and the pieces of display corresponding thereto can easily be determined by setting the display corresponding to the first object 14 to be heated as the display 31 and the display corresponding to the second object 15 to be heated as the display 32. The operation display unit 12 becomes operable by pressing or sliding a displayed portion by including a touch panel, and can improve the usability thereof.

(Second Embodiment)

[0078] An induction heating device 10b of the second embodiment is described with reference to Fig. 8.

[0079] Only the parts different from the first embodiment are described in the second embodiment and the same parts as those in the first embodiment are described again.

[0080] Fig. 8 is a timing chart of the determination operation for the object to be heated of the case where the heating coils 11 corresponding to an area in which the object to be heated is placed are detected by the determination unit 18 for the object to be heated of the induction heating device 10b according to the second embodiment of the present disclosure.

[0081]  The second embodiment differs from the first embodiment in that recognition is repeatedly executed by setting the time period for the recognition as one object to be heated to be a specific time period based on the timings at which the heating coils 11 detect the object to be heated.

[0082] As shown in Fig. 8, the determination unit 18 for the object to be heated repeats the determination time period Tc3 having a specific time period and, thereby, determines the number, etc., of the objects to be heated from the number, etc., of the areas each formed by the heating coils 11 detected within each determination time period Tc3. For example, the induction heating device 10b of the second embodiment starts the determination time period Tc3 when the power of the induction heating device 10b is turned on, executes the detection for the objects to be heated using at least all the heating coils 11, thereafter, causes the determination time period Tc3 to come to an end, and starts a new determination time period Tc3. In this manner, in the second embodiment, the determination for the objects to be heated is repeatedly executed during the specific determination time periods Tc3 and, thereby, it is not necessary to detect the trigger for the time when the determination unit 18 for the object to be heated first detects the object to be heated. The determination unit 18 for the object to be heated does not need to detect the fact that the presence of the object to be heated is first determined using the heating coil 11, as the trigger to start the determination time period Tc3. The configuration of the determination unit 18 for the object to be heated can be simplified and the object to be heated can easily be determined.

(Third Embodiment)

[0083] An induction heating device 10c of the third embodiment is described with reference to Figs. 9 and 10.

[0084] Only the parts different from the first or the second embodiment are described in the third embodiment and the same parts as those in the first or the second embodiment are not described again.

[0085] The case is described where a third object 21 to be heated is placed on the induction heating device 10c according to the third embodiment of the present disclosure. Fig. 9 shows a time chart of a determination operation for the object to be heated executed when the heating coils corresponding to an area in which an object to be heated is placed are detected by the determination unit 18 for the object to be heated of the induction heating device 10c according to the third embodiment of the present disclosure. Fig. 10 shows display on the operation display unit 12 of the induction heating device 10c according to the third embodiment of the present disclosure, and shows an example of the display on the operation display unit 12 based on the result of the determination by the determination unit 18 for the object to be heated.

[0086] In the third embodiment, the third object 21 to be heated such as a substantially rectangular-shape (for example, of a size corresponding to eight of the heating coils) cooking pan is placed on the top plate 13. The third embodiment differs from the first or the second embodiment in that the eight heating coils 11bb, 11cb, 11bc, 11cc, 11bd, 11cd, 11 be, and 11ce in the coil configuration shown in Fig. 1 are detected in a specific time period Tc4 for the recognition as one object to be heated.

[0087] The case will be described where the third object 21 to be heated needing the eight heating coils 11 is placed on the induction heating device 10c having the multi-coil configuration of the present disclosure. As shown in Fig. 9, the determination unit 18 for the object to be heated detects the eight heating coils 11bb, 11cb, 11bc, 11cc, 11bd, 11cd, 11be, and 11ce that correspond to the area in which the object to be heated is placed, and determines "OBJECT TO BE HEATED PRESENT" for each of these heating coils. Thereby, the determination unit 18 for the object to be heated determines that the object to be heated is placed.

[0088] The determination unit 18 for the object to be heated determines that one object to be heated is placed in the area formed the heating coils 11bb, 11cb, 11bc, 11cc, 11bd, 11cd, 11be, and 11ce for which "OBJECT TO BE HEATED PRESENT" is determined in the determination time period Tc4. Thereafter, the result of the determination by the determination unit 18 for the object to be heated is output to the control unit 17.

[0089]  Associated with the result of the determination by the determination unit 18 for the object to be heated, the control unit 17 causes the operation display unit 12 to display thereon one piece of display 33 corresponding to the size of the object to be heated as shown in Fig. 10.

[0090] Thereby, even when the size of the object to be heated is changed, one type of heating control is present for the area for which the one object to be heated is recognized and plural operations therefore do not need to be executed, and the usable induction heating device can be provided.

(Fourth Embodiment)

[0091] An induction heating device 10d according to the fourth embodiment will be described with reference to Figs. 11 and 12.

[0092] Only the parts different from the first to the third embodiments are described in the fourth embodiment and the same parts as those in the first to the third embodiments are not described again.

[0093] Fig. 11 is a schematic plan diagram of the state where the first object 14 to be heated and the second object 15 to be heated are placed on the induction heating device 10d according to the fourth embodiment of the present disclosure. Fig. 12 is a schematic plan diagram of the state where the third object 21 to be heated is placed on the induction heating device 10d according to the fourth embodiment of the present disclosure.

[0094] The fourth embodiment differs from the first to the third embodiments in that light emitting units 24 to indicate an area formed by the heating coils 11 corresponding to the area of the object to be heated placed on the top plate 13, are disposed around each of the plural heating coils 11 as shown in Figs. 11 and Fig. 12.

[0095] In the induction heating device 10d of the fourth embodiment, the light emitting units 24 are disposed to surround at least the circumference of each of the heating coils 11 disposed below the top plate 13 on which the object to be heated is placed. The light emitting units 24 emit light and, thereby, the area can be indicated that is formed by the heating coils 11 corresponding to the area in which the object to be heated is placed on the top plate 13. The user therefore can check the determination state (the number, the size, or the shape) for the object to be heated even on the top plate 13 and the visibility can be improved.

[0096] The usability can also be improved by causing the circumference of the object to be heated to emit light, at which the user most frequently look during the use of the induction heating device 10d.

[0097] Fig. 11 shows the case where the first object 14 to be heated and the second object 15 to be heated are placed on the top plate 13. In Fig. 11, because the determination unit 18 for the object to be heated can already determine that the two objects to be heated are placed, the light emitting units 24 indicate on the top plate 13 two heating areas 25 and 26 based on the result by the determination unit 18 for the object to be heated. For example, the light emitting units 24 each emit light in a rectangular frame shape around each of the heating areas 25 and 26 each formed by the heating coils 11 corresponding to each of the areas in which the objects to be heated are placed.

[0098] On the other hand, in Fig. 12, because the determination unit 18 for the object to be heated can already determine that the one third object 21 to be heated is placed that is larger than each of the objects to be heated of Fig. 11, a rectangular heating area 27 whose size matches with the size of the object to be heated is indicated. The area intended for the heating operation or the currently heated area can be checked by visual observation and any erroneous operation is caused to be difficult for the user by properly indicating the sizes or the number of areas indicated on the top plate 13 as above.

[0099] According to the induction heating devices in all the above embodiments, as shown in Fig. 1, the heating coils in each of the longitudinal lines and each of the lateral lines are set to be arranged in a straight line while the effect of the induction heating device of the present disclosure can be achieved as far as the heating coils are arranged in lines, and the configuration of the heating coils is therefore not limited to the above.

[0100] As is clear from the present disclosure, the control of the heating can properly be executed for the object to be heated by determining whether one object to be heated is present, based on the timing at which the object to be heated is detected. The control of the heating coils can properly be executed that correspond to the area in which the object to be heated is placed by determining the number, the size, or the shape, etc., of the object to be heated based on the heating coils for which the presence of the object to be heated is detected in the determining time period that is the specific time period.

Industrial Applicability

[0101] As above, the induction heating device according to the present disclosure can determine that the second object to be heated placed after the specific time period elapses from the placement of the first object to be heated is an object to be heated different from the first object to be heated. Execution of the control for the heating such as the starting of the heating is therefore enabled for a desired object to be heated, and the induction heating device is therefore effective for the use as an induction heating cooking device.

Reference Signs List

[0102] 

10

induction heating device

11

heating coil

12

operation displaying unit

13

top plate

14

first object to be heated (a cooking pan)

15

second object to be heated (a cooking pan)

16

inverter

17

control unit

18

determination unit for the object to be heated

21

third object to be heated

24

light emitting unit

25, 26, 27

heating area

31, 32, 33

display

40

power source

41

diode bridge

42

choke coil

43

smoothing capacitor

44

first switching element

45

second switching element

46

resonance capacitor

47

snubber capacitor

48

current detecting unit

49

voltage detecting unit

Claims

1. An induction heating device comprising:

a top plate on which an object to be heated is placed;

a plurality of heating coils which are disposed below the top plate;

an inverter which supplies a high frequency current to the plurality of heating coils;

a control unit which controls an output of the inverter; and

a determination unit for the object to be heated which determines a state of the object to be heated which is placed on the top plate,

wherein the determination unit for the object to be heated detects the heating coils which correspond to an area in which the object to be heated is placed, and determines a state of the object to be heated to be a state where the one object to be heated is placed in an area formed by the heating coils which are detected in a determination time period for determining the state of the object to be heated of the detected heating coils, and

wherein the control unit controls supply of electric power to the heating coils corresponding to the area in which the object to be heated is placed based on the state of the object to be heated which is determined by the determination unit for the object to be heated.

2. The induction heating device of claim 1, further comprising
an operation display unit which displays a result of the determination by the determination unit for the object to be heated and outputs an operation command to the control unit,
wherein the control unit controls the supply of the electric power to the heating coils based on the operation command which is output from the operation display unit.

3. The induction heating device of claim 1 or 2,
wherein the determination unit for the object to be heated has a plurality of determination time periods, and
wherein the determination unit for the object to be heated determines that another new object to be heated is placed in an area formed by the heating coils newly detected in each of the determination time periods.

4. The induction heating device of any one of claims 1 to 3, wherein
the determination time period is started from a time point at which the heating coils corresponding to the area in which the object to be heated is placed are detected by the determination unit for the object to be heated.

5. The induction heating device of any one of claims 1 to 3, wherein
the determination time period having a specific time period is repeated.

6. The induction heating device of any one of claims 1 to 5, wherein
the determination unit for the object to be heated determines number of objects to be heated from number of areas each formed by the heating coils which are detected in the determination time period.

7. The induction heating device of any one of claims 1 to 6, wherein
the determination unit for the object to be heated determines a size and/or a shape of the object to be heated from a size and/or a shape of the area formed by the heating coils which are detected in the determination time period.

8. The induction heating device of any one of claims 1 to 7, further comprising
a light emitting unit which is disposed around each of the plurality of heating coils, the light emitting unit visually observably lighting through the top plate,
wherein the light emitting unit is configured to indicate by lighting a circumference of the area formed by the heating coils, the area corresponding to at least the area in which the object to be heated is placed.

Drawing