JPH0878148A - Electromagnetic cooker - Google Patents

Abstract

(57) [Summary] [Purpose] The heating pattern has been improved for large pans,
Provide an electromagnetic cooker that does not cause a reduction in heating power or a leakage magnetic field for small pots. [Structure] One flat spiral coil is connected to terminals S1, S2,
The coils are electrically divided by S1A and S2A to form the inner coil 11 and the outer coil 12, and the high frequency power generation circuits 2A and 2B individually output the high frequency power to the coils 11 and 12, respectively. At that time, by using the control circuit 3, the high-frequency power generation circuits 2A, 2
The output timing of B is controlled, and the high frequency power to each coil 11 and 12 is alternately switched so that the duty ratio, the output time interval, or the combination thereof can be arbitrarily adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic cooker, and more particularly to the structure of a heating coil and a power supply system for outputting high frequency power to the heating coil.

[0002]

2. Description of the Related Art An electromagnetic cooker includes a heating coil formed by spirally winding a conducting wire such as a litz wire from the center toward the outer circumference, and a high-frequency power generation circuit (power supply) for outputting high-frequency power to the heating coil. And a top plate provided on the casing frame of the cooker substantially parallel to the main surface of the heating coil, and outputs high-frequency power to the heating coil to induction-heat an object to be heated on the top plate, for example, a cooking pot. To do. Usually, the heating coil is formed in a flat spiral shape having a relatively small coil diameter with respect to the cooking pot, and only one high frequency power generation circuit is provided for the heating coil. Further, the heating of the cooking pot is performed on the portion of the pot bottom that is close to the heating coil and faces the main surface thereof.

[0003]

As described above, the heating of the cooking pot by the electromagnetic cooker is performed on the portion of the pot bottom that faces the main surface of the heating coil. Therefore, the bottom diameter not larger than the diameter of the heating coil is used. For cooking pans with a small number (hereinafter referred to as small pots for convenience), it does not pose a problem in terms of heating power, but a cooking pot with a bottom diameter significantly larger than the diameter of the heating coil (hereinafter, for convenience, a large pot). (Referred to as a pot),
Since it is possible to heat only an area as narrow as the diameter of the heating coil, there is a problem that the heating pattern on the bottom of the pan is significantly biased, which makes cooking inconvenient. In this case, it is possible to obtain sufficient heating power by increasing the diameter of the heating coil, but then, the heating power in the annular region near the outer periphery of the heating coil becomes relatively stronger than that in the central portion, and the heating pattern becomes a donut. As a result, the above-mentioned cooking problem cannot be solved, but rather the problem is promoted.

When a small pot having a bottom diameter smaller than that of the heating coil is placed on the top plate for heating, the portion of the heating coil that does not contribute to induction heating, that is, the no-load region appears in an annular shape. The high-frequency magnetic field in the no-load region leaked around the small pot, causing the following problems. (1) The heating power for the small pot becomes insufficient. (2) The surrounding area of the small pan is abnormally heated. (3) In the case of a pan with a metal handle or a frying pan, the handle is also heated, which makes it difficult to handle. (4) Other metal cooking utensils placed around the small pot are heated. (5) Harmful or unnecessary radio noise increases, and particularly adversely affects electronic devices worn on the human body, such as wristwatches and magnetic cards.

The object of the present invention is to solve the above problems,
An electromagnetic cooking system in which the heating pattern is improved for an object to be heated such as a large pan and at least the above problems (1) to (5) are not caused to an object to be heated such as a small pan. To provide a container.

[0006]

An electromagnetic cooker provided by the present invention is provided with a plurality of spiral heating coils having different diameters, which are concentrically arranged on a substantially same plane, and a high frequency wave is individually applied to each heating coil. It is characterized by comprising a high-frequency power generation circuit for outputting electric power and an output control means for switching the output to each heating coil of the high-frequency power circuit in a time division manner. In the electromagnetic cooker having the above-mentioned configuration, the plurality of spiral heating coils may be one in which one flat spiral coil is electrically divided for each predetermined number of turns, and the adjacent spiral heating coils are mutually separated. It may be wound in the opposite direction. The high-frequency power generation circuit includes, for example, a plurality of resonance capacitors each forming a resonance circuit with the plurality of heating coils, and a resonance determined by a capacitance value of each resonance capacitor and an inductance value of the heating coil. The electric power of the frequency is output to each heating coil. In this case, in order to prevent electromagnetic interference between the heating coils, the resonance frequency of one resonance circuit may be 1.2 times or more the resonance frequency of the adjacent resonance circuit. preferable. Further, the output control means includes a control circuit for adjusting at least one of the output level, the duty ratio, and the output time interval of the high frequency power output to each heating coil.

An electromagnetic cooker of another structure provided by the present invention is the electromagnetic cooker of the above structure, wherein a sensor for detecting the energization state of each of the plurality of heating coils and the presence or absence of the object to be heated by the sensor output. Or a discriminating means for discriminating its size, and the control circuit controls at least one of the output level of the high frequency power and the output time to each heating coil based on the output result of the discriminating means. It is characterized by

[0008]

In the electromagnetic cooker of the present invention, one flat spiral coil is divided to form a plurality of heating coils, or a plurality of heating coils having different diameters are arranged concentrically and on substantially the same plane. High frequency power is individually output to each heating coil. At that time, the output control means is used to control the output of the high frequency power generation circuit, and the high frequency power output to each heating coil is switched in a time division manner. This makes it possible to realize a mode in which only the heating coil near the center is energized manually or automatically, a mode in which each heating coil is alternately switched at a predetermined time interval, and energized. By adjusting the output level of high frequency power, the duty ratio, the output time interval, or a combination thereof with the control circuit, the heating pattern of the object to be heated can be arbitrarily changed according to the type of cooking. In addition, when the adjacent spiral heating coils are wound in mutually opposite directions, it is possible to reduce the induced current of the other heating coils during the output control of the high frequency power.

By the way, each heating coil has a different energization state depending on whether or not the object to be heated is present in the vicinity thereof. Therefore, if the sensor detects the energization state of each heating coil, the presence or size of the object to be heated can be known from the output of each sensor. In the present invention, the determination means for that purpose is provided, and the output control means controls at least one of the output level of the high frequency power and the output time to each heating coil based on the output result of this determination means. This facilitates automation of each mode selection described above, and enables effective heating according to the size of the object to be heated.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) FIG. 1 is a main part configuration diagram showing a configuration of an electromagnetic cooker according to a first embodiment of the present invention. In FIG.
Reference numeral 1 is a circular or polygonal heating coil formed by winding a litz wire in a flat spiral shape, and has end terminals S1 and S1 at both ends thereof.
S2, intermediate portion terminals S1A and S2A are provided in the intermediate portion of the coil, and the inner coil 11 is formed by the central end portion terminal S1 and the intermediate portion terminal S1A, and the outer edge portion end terminal S2 and the intermediate portion terminal S2A
And constitute the outer coil 12, respectively. The present invention is characterized in that the plurality of heating coils are independently controlled to variously adjust the overall heating pattern, but for convenience, only the case of two heating coils will be described.

Reference numerals 2A and 2B denote inner coil 1 respectively.
1 is a high-frequency power generation circuit that outputs high-frequency power to the outer coil 12, and reference numeral 3 is a control circuit for controlling the output of the high-frequency power generation circuit 2. Also, reference numeral 4
Is an operation display circuit including a heating on / off switch, a heating mode selection switch, a heating level setting volume, an alarm display, and the like, and reference numeral 5 is a top plate made of an insulating material.

The control circuit 3 has a timing control circuit and a level setting circuit (not shown). The timing control circuit turns on / off the outputs of the respective high-frequency power generation circuits 2A and 2B in time division according to an instruction from the operation display circuit 4 to adjust the duty ratio of the output power or the output time interval.
The cutoff signals T1 and T2 are generated, and the level setting circuit generates level setting signals P1 and P2 for adjusting the output levels of the high frequency power generation circuits 2A and 2B (output control means). .

FIG. 2 shows a concrete example of the structure in which the above-mentioned high frequency power generating circuits 2A and 2B are realized by two half bridge circuits. These half bridge circuits 22A, 2
2B is a DC circuit 21 that rectifies commercial power (AC power)
It is a kind of resonance circuit that converts the output power of the above into high frequency power. Referring to FIG. 2, the first half bridge circuit 22
The end terminal S1 of the inner coil 11 is conductively connected to the intermediate point of the transistor arm forming the A through the resonance capacitor C1, and the resonance point is set to the intermediate point of the transistor arm forming the second half bridge circuit 22B. The end terminal S2 of the outer coil 12 is electrically connected through the transistor C2. The intermediate terminals S1A and S2A are conductively connected to the intermediate points of the common bypass capacitors C3 and C4. The resonance frequency f1 of the high frequency power output to the inner coil 11 is substantially determined by the inductance value and the capacitance value of the resonance capacitor C1,
The resonance frequency f of the high frequency power output to the outer coil 12
2 is substantially determined by its inductance value and the resonance capacitor C2. These resonance frequencies f1 and f2 are preferably separated from each other so that the coils 11 and 12 do not electromagnetically interfere with each other. It has been confirmed by the inventors of the present invention that there is no practical problem if one resonance frequency is at least 1.2 times or more as high as the other resonance frequency. The capacitors C1 to C4 can be replaced with variable capacitors. The output time and output level of each half bridge circuit 22A, 22B are controlled by the transistor drive signals D1, D2 input from the control circuit 3. The transistor drive signals D1 and D2 are the on / off signals T1 and T2 shown in FIG.
And the level setting signals P1 and P2. Half bridge circuits 22A, 22 as described above
When B is used, the two high frequency power generation circuits 2A and 2B can be realized with a simple circuit configuration. Although the above is an example of a circuit configuration suitable for achieving cost reduction, the high frequency power generation circuits 2A and 2B necessary for implementing the present invention are
It is needless to say that the structure is not necessarily limited to the case where the half bridge circuits 22A and 22B described above are used, and a configuration including another high frequency oscillation circuit may be used.

FIG. 3 is an explanatory diagram for heating the small pot 6 using the electromagnetic cooker of this embodiment, and FIG. 3 (a) is a configuration diagram of the main part thereof. The hatched portion of each heating coil 11 and 12 shows the state of being energized. In this case, according to an instruction from the operation display circuit 4, the level setting circuit of the control circuit 3 causes the high frequency power generation circuit 2 connected to the inner coil 11
The output level of A is adjusted from zero to the rated value (100%), and the output level of the high frequency power generation circuit 2B connected to the outer coil 12 is set to zero.
Alternatively, the output duty ratio of the high frequency power generation circuit 2A connected to the inner coil 11 by the timing control circuit is set to 10
Adjust to 0%. Each high frequency power generation circuit 2 at this time
The output states of A and 2B are shown in FIG. According to such a control example, the inner coil 1 located at the bottom of the small pot 6
Since the high frequency power is selectively concentrated only on 1 and no no-load region is not generated around it, leakage of the high frequency magnetic field is suppressed,
It is possible to solve various conventional problems that have occurred in the case of the small pot 6.

4A and 4B are explanatory views when the large-sized pan 7 is heated by using the electromagnetic cooker of the present embodiment. FIG. 4A is a configuration diagram of a main part thereof, and FIG. 4B is controlled by the control circuit 3. FIG. 3 is an output state diagram of each of the high frequency power generation circuits 2A and 2B that are generated. In the figure,
t1 and t2 are output times of high frequency power. Further, the hatched portions of the heating coils 11 and 12 show the state of being energized.

In this example, according to an instruction from the operation display circuit 4, the level setting circuit of the control circuit 3 sets the output of the high frequency power from zero to the rated value (100%), and the timing control circuit sets its output duty ratio. It is designed to be variously changed. That is, the outputs of the first high-frequency power generation circuit 2A and the second high-frequency power generation circuit 2B are alternately turned on / off in accordance with a predetermined time ratio, and the former output is changed to the time t.
After turning on only 1 (ON), turning off only at time t2 (OFF)
And the latter output at time t1.
This is repeated after turning off only for a time t2. In such a control example, the heating pattern of the pan bottom can be arbitrarily changed by changing the ratio of each time t1, t2 and each output level, and various heating patterns suitable for the type of cooking can be formed. .

The times t1 and t2 are 0 to 0, respectively.
It can be changed up to about 3 seconds, and when t2 is set to 0, a continuous output state as shown in FIG. 3B is obtained, and a control example suitable for selectively heating only the inner portion of the large pan 7 Become. Further, the level setting circuit and the timing control circuit may independently control the outputs of the high frequency power generation circuits 2A and 2B, or may control both in combination.
In the latter case, the heating pattern can be finely controlled, and the conventional problems can be solved more effectively.

The first embodiment of the present invention is as described above, but the positions of the intermediate portion terminals S1A and S2A are fixed as described above, and this is made variable so that the inductance value and the resonance frequency can be changed. You may change it. Also,
As in the above embodiment, in addition to the configuration in which one flat spiral coil is divided into a plurality of heating coils, a plurality of independent heating coils having different diameters are arranged concentrically and substantially on the same plane. May be.

(Second Embodiment) FIG. 5 is a schematic view of an essential part of an electromagnetic cooker according to a second embodiment of the present invention. In the electromagnetic cooker having the structure shown in the first embodiment, concentric and The inner coil 11 and the outer coil 12 'located on substantially the same plane are wound in opposite directions. Reference numerals 2'A and 2'B are high-frequency generation circuits for outputting high-frequency power to the coils 11 and 12 ', respectively, and S2' and S2'A are terminals of the outer coil 12 '. It is the same as shown.

In this embodiment, a sensor L1 for detecting the coil current in the electric circuit is further provided on the common power line of the intermediate terminals S1A and S2'A of the inner coil 11 and the outer coil 12 ', and the output of this sensor L1 is provided. The signal HF1 is fed back to the control circuit 3 '. The control circuit 3 ′ regenerates the on / off signals T1 and T2 and / or the level setting signals P1 and P2 based on the output signal HF1 and outputs them to the respective high frequency power generation circuits 2′A and 2′B. .

Further, FIG. 6 shows a configuration diagram when the high frequency power generation circuits 2'A and 2'B are realized by two half bridge circuits. In this example, in the configuration shown in FIG. 2, the winding direction of the outer coil 12 'is opposite, and the intermediate terminals S1A and S2' of the inner coil 11 and the outer coil 12 'are further reversed.
The sensor L1 is provided on the common power line of A, and the output signal HF1 of the sensor L1 is fed back to the control circuit 3 ′. The control circuit 3 ′ regenerates the transistor drive signals D1 and D2 based on the output signal HF1 and outputs the transistor drive signals D1 and D2 to the high frequency power generation circuits 2′A and 2′B.

Next, the operation when the inner coil 11 and the outer coil 12 'are wound in opposite directions as described above will be described with reference to FIGS. FIG. 7 is a partial configuration diagram of FIG. 6, in which the common power lines of the coils 11 and 12 ′ are conductively connected to the intermediate points of the common bypass capacitors C3 and C4. Here, the current flowing through the inner coil 11 is I ₁ ,
As a result, when the induced current induced in the outer coil 12 ′ is i ₂ and the fluctuation of the intermediate voltage of the bypass capacitors C3 and C4 is ΔV, this fluctuation ΔV is the fluctuation ΔV.
It works to suppress the induced current i ₂ of 2 ′. FIG. 8A shows
It is a state explanatory view at this time, the solid line is the current I ₁ flowing in the inner coil, the thin line is the induced current i ₂ , and the broken line is the variation ΔV. Further, FIG. 8B is a state explanatory view in the case where all the coils are in the forward direction, and it is shown that the voltage variation ΔV acts in the direction of increasing the induced current i ₂ .
Note that the above is an example of the case where high frequency power is output only to the inner coil 11, but the same relationship applies when high frequency power is output only to the outer coil 12 ′. in this way,
By reversing the winding directions of the coils 11 and 12 'to each other, the induced currents of the other coils are suppressed,
The output signal HF1 of the sensor L1 can be used as a highly accurate feedback signal.

(Third Embodiment) FIG. 9 is a schematic view of the essential parts of an electromagnetic cooker according to a third embodiment of the present invention, in which 51 is an inner coil, 52 is an outer coil, 53 is a DC circuit, 54A, 5
4B is a high frequency electric power generation circuit, 55 is a control circuit. Although the coils 51 and 52 are shown separately for convenience, they may be one flat spiral coil divided into a predetermined number of turns as in the first embodiment. The winding direction of each coil 51, 52 may be either forward or reverse. DC circuit 53 and high frequency power generation circuit 5
4A and 54B are the same as those in the first embodiment.

In this embodiment, sensors L1 and L for detecting the electric current of the electric path are respectively provided on the common power line of the inner coil 51 and the outer coil 52 and the power line of the power input section (AC input section).
2 is provided to detect the current level of each part, and a heated object discrimination circuit (discrimination means) for discriminating the size of the pot based on the output of each sensor is provided in the control circuit 55 to heat the small pot. The high frequency power is automatically output only to the inner coil 51. Although the sensor L1 is the same as that described in the second embodiment, it is not used here for feedback to the control circuit 55, but for determining the presence or absence of a pan and its size as described below. To use. Further, in the illustrated example, one sensor L1 is provided on the common power line, but it may be provided separately around the coils 51 and 52.

In such a structure, the output signal HF1 of the sensor L1 is smaller than the output signal I _AC of the sensor L2 when there is a pan at the location of the inner coil 51 on the top plate, and it is large when there is no pan. . The same applies to the case of the outer coil 52. Therefore, these sensors L1 and L2
By comparing the combination of the output signals HF1 and I _AC of the above, it is possible to specify the existence of the pan and its size.
The processing procedure of the control circuit 55 utilizing this property is shown in FIG.

Referring to FIG. 10, first, at the same time as heating "ON", the lowest level high frequency power is output only to the inner coil 51 (S (processing step, the same applies hereinafter) 101). This minimum level is insufficient for cooking, but its ON
The level is sufficient for the / OFF discrimination and is preset by the level setting circuit in the control circuit 55. Then, the output signal HF1 of the sensor L1 at that time is compared with the output signal I _AC of the sensor L2 of the power input unit to determine whether or not there is a pan on the top plate (S102). At this time, if there is no pot, wait at the lowest level until the pot is placed on the top plate. On the other hand, when there is a pan, the output (power supply) of the high frequency power to the inner coil 51 is temporarily stopped (S
103), the high frequency power of the same level is immediately output to the outer coil 52 (S104), and it is determined whether or not there is a pan (S105). If it is determined that there is no pot here, it means that the inner coil 51 has a pot and the outer coil 52 does not have a pot, so that the top plate is a small pot. In this case, the heating of the small pot is controlled, that is, the high frequency power of the set level is output to the inner coil 51 (S106). On the other hand, if the outer coil 52 also has a pan, it is the large pan that is placed on the top plate, so heating control of the large pan, that is, the inner coil 51.
The timing control circuit and / or the level setting circuit are adjusted so as to obtain the optimum heating pattern for cooking by using both the outer coil 52 and the outer coil 52 (S107).

Although the present invention has been described with reference to a plurality of embodiments, the present invention is not limited to the configurations of the embodiments, and design changes can be made without departing from the spirit of the invention. Of course.

[0028]

As is apparent from the above description, according to the present invention, it is possible to individually control the output of high frequency power to a plurality of heating coils having different diameters, which has been impossible in the past. Various heating patterns can be formed. For example, it is possible to intensively output high-frequency power only to the heating coil located near the portion to be selectively heated, or to stop the high-frequency power output to the heating coil that does not contribute to induction heating for a predetermined time. It is possible to solve many problems in the related art caused by the generation of an impossible biased heating pattern or an unloaded region.

Further, the sensor detects the energized state of the power input section and the energized state of each heating coil, and the presence or absence of the object to be heated or its size is discriminated by the combination of the sensor outputs, and the output result Since at least one of the output level and the output time of the high frequency power to each heating coil is controlled based on the above, there is an effect that automation of selection of various heating patterns for the object to be heated is facilitated.

[Brief description of drawings]

FIG. 1 is a configuration diagram of essential parts of an electromagnetic cooker according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a specific configuration example when the high-frequency power generation circuit of the first embodiment is realized by using a half bridge circuit.

FIG. 3 (a) is a configuration diagram of a main part for heating a small pot in the first embodiment, and FIG. 3 (b) is a high-frequency power generation circuit for intensively heating the center of the bottom of the small pot. Output state explanatory view.

FIG. 4A is a configuration diagram of a main part when the large pan is heated in the first embodiment, and FIG. 4B is an output state of each high-frequency power generation circuit when the pan bottom of the large pan is uniformly heated. Explanatory drawing.

FIG. 5 is a main part configuration diagram of an electromagnetic cooker according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a specific configuration example when the high-frequency power generation circuit of the second embodiment is realized by using a half bridge circuit.

FIG. 7 is a partial configuration diagram for explaining the operation of the second embodiment.

FIG. 8 (a) is a state explanatory view of the state of ΔV for the fluctuation amount of the coil current I1, the induced current i2 and the intermediate voltage of the bypass capacitors C3 and C4 when the winding directions of the inner coil and the outer coil are reversed, FIG. 6B is a state explanatory view when all the coils are in the forward direction.

FIG. 9 is a configuration diagram of a main part of an electromagnetic cooker according to a third embodiment of the present invention, which determines the size of a pan.

FIG. 10 is a flowchart showing a processing procedure until the location of the pot is specified in the control circuit having the configuration of FIG. 9;

[Explanation of symbols]

 1,1 'Heating coil 11,51 Inner coil 12,12', 52 Outer coil 2A, 2B, 2'A, 2'B High frequency power generation circuit 3, 3 ', 55 Control circuit 4 Operation display circuit 5 Top plate 6 Small pan 7 Large pan L1, L2 Sensor to detect coil current in electric circuit

Claims (7)

[Claims] 1. A plurality of spiral heating coils having different diameters, which are arranged concentrically and substantially on the same plane, a high-frequency power generation circuit for individually outputting high-frequency power to each heating coil, and the high-frequency power circuit. And an output control means for switching the output to each heating coil in a time division manner. 2. The electromagnetic cooker according to claim 1, wherein each of the plurality of spiral heating coils is formed by electrically dividing one flat spiral coil into a predetermined number of turns. 3. The electromagnetic cooker according to claim 1, wherein the plurality of spiral heating coils have adjacent spiral heating coils wound in directions opposite to each other. 4. The high-frequency power generation circuit includes a plurality of resonance capacitors each forming a resonance circuit with the plurality of heating coils, and a capacitance value of each resonance capacitor and an inductance value of the heating coil. The electromagnetic cooker according to any one of claims 1 to 3, which is configured to output electric power having a determined resonance frequency to the heating coil. 5. The electromagnetic cooker according to claim 4, wherein the resonance frequency of the one resonance circuit is 1.2 times or more the resonance frequency of the adjacent resonance circuit. 6. The output control means includes a control circuit for adjusting at least one of an output level, a duty ratio and an output time interval of the high frequency power output to each heating coil. The electromagnetic cooker according to any one of 5 above. 7. The electromagnetic cooker according to any one of claims 1 to 6, wherein a sensor for detecting an energized state of each of the plurality of heating coils and the presence or absence of an object to be heated based on the output of the sensor. A determination means for determining the magnitude is provided, and the output control means controls at least one of the output level of the high frequency power and the output time to each heating coil based on the output result of the determination means. Characteristic electromagnetic cooker.