JP2001068260A - Induction cooking appliance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow aluminum pan and a multi-layered pan to be heated. SOLUTION: The frequency of a resonance current determined by a heating coil 6 and a resonance capacitor 7 coupled to a pan 8 is twice or more as high as the drive frequency of a switching element 4, and induction heating is allowed thereby in a frequency twice or more as high as conventional one.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker for cooking using induction heating by a high frequency magnetic field.

[0002]

2. Description of the Related Art A conventional induction heating cooker will be described below with reference to the drawings. FIG. 13 is a block diagram showing a configuration of an example of an induction heating cooker conventionally used.

The power supply 1 is a DC power supply obtained by rectifying a commercial power supply, and has a pulsating current of twice the commercial frequency or a smoothed voltage. The power supply 1 is connected to the smoothing capacitor 2 and the choke coil 3, and supplies high-frequency power to the heating coil 6 according to the switching operation of the switching element 4. The high-frequency power supplied to the heating coil 6 is supplied to the pan 8 as a high-frequency magnetic field, and the pan itself generates heat due to the eddy current generated by the high-frequency magnetic field. Here, the pan 8 is usually made of a material having a large specific resistance such as magnetic stainless steel or iron, and an aluminum pan or the like is usually excluded because it cannot be heated. Here, the current of the heating coil 6 is a resonance current determined by the heating coil 6 and the resonance capacitor 7 that are magnetically coupled to the pan 8 when the switching element 4 is in the ON state.
The control means 15 is supplied until the resonance current becomes zero again, that is, until the current flows through the diode 5. The control unit 15 turns off the switching element 4 for an off time determined according to the set input power,
The switching element 4 is turned on again.

FIG. 12 shows waveforms during the operation of the switching element 4. When the gate VGE of the switching element 4 enters the ON operation, the resonance current Ic becomes zero again and maintains the ON state until the current flows through the diode 5. When the switching element 4 is turned off, a resonance voltage Vce is generated at both ends of the switching element 4, but the switching element 4 is turned on again after a predetermined off time has elapsed.

[0005]

In such a conventional induction heating cooker, the specific resistance of the pan itself is low in an aluminum pan or a multi-layer pan in which the aluminum material has many components in the thickness of the bottom of the pan. Therefore, heating was difficult.

A first method which is effective as a method of inductively heating an aluminum pan is to increase the ampere-turn of the heating coil, that is, to increase the number of turns of the heating coil. This is a method of further increasing the heating frequency. However, when the number of turns of the heating coil is increased, the size of the cooker becomes larger, and when the frequency is further increased, the loss of the switching element increases, making it difficult to cool the switching element. Is caused.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an induction heating cooker capable of heating an aluminum pan and a multi-layer pan.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a smoothing capacitor connected in parallel to a power supply, a choke coil connected to a positive electrode of the power supply, an opposite end of the choke coil, and the power supply. A high frequency inverter comprising a switching element connected to the negative electrode of the switching element, a diode connected in parallel with the switching element, a heating coil and a resonance capacitor arranged in parallel with the switching element and connected in series with each other, and a high frequency magnetic field from the high frequency inverter. And a control means for controlling the switching element, wherein the resonance current frequency formed by the heating coil and the resonance capacitor is twice or more higher than the driving frequency of the switching element. It is.

Accordingly, high-frequency power can be supplied to the pan without increasing the switching loss of the switching element, and an induction heating cooker capable of heating an aluminum pan or a multi-layer pan can be realized.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 is a smoothing capacitor connected in parallel to a power supply, a choke coil connected to a positive electrode of the power supply, a reverse end of the choke coil and a negative electrode of the power supply. A switching element, a diode connected in parallel to the switching element, a high-frequency inverter including a heating coil and a resonance capacitor arranged in parallel with the switching element and connected in series with each other, and heated by receiving a high-frequency magnetic field from the high-frequency inverter. An induction heating cooker comprising a pan and control means for controlling the switching element, wherein a resonance current frequency formed by the heating coil and the resonance capacitor is twice or more higher than a driving frequency of the switching element.

Thus, high-frequency power can be supplied to the pan without increasing the switching loss of the switching element, and an induction heating cooker capable of heating an aluminum pan or a multi-layer pan can be realized.

According to a second aspect of the present invention, there is provided the induction heating cooker according to the first aspect, wherein the resonance current frequency is 100 kHz or more.

Thus, even when the weight of the aluminum pan or the like is light, the floating of the pan is unlikely to occur, and a highly safe induction heating cooker can be realized.

According to a third aspect of the present invention, there is provided a zero current detecting means for detecting the zero current of the resonance current and a counter for counting the number of times of the zero current passing, and the switching element is turned off at a predetermined number of the zero current. The induction heating cooker according to claim 1 or 2, wherein

As a result, the switching operation can be performed with the required number of resonance currents and with zero current, and a highly reliable induction heating cooker with small switching loss can be realized.

According to a fourth aspect of the present invention, there is provided the induction heating cooker according to any one of the first to second aspects, wherein the control of the input power is performed during the off time of the switching element.

As a result, power can be adjusted while maintaining the number of resonance currents, and an induction heating cooker excellent in controllability can be realized.

According to a fifth aspect of the present invention, there is provided the induction heating cooker according to the third aspect, wherein the input power is controlled by changing the number of times the resonance current passes through zero current.

As a result, the range of power adjustment is widened, and an induction heating cooker with excellent controllability can be realized.

According to a sixth aspect of the present invention, there is provided the induction heating cooker according to the fifth aspect, wherein the driving frequency of the switching element is fixed.

This makes it possible to adjust the power at a constant frequency, to suppress the generation of interference noise due to the difference in the driving frequency of the adjacent induction heating cookers, and to reduce the noise of the induction heating cookers. It is possible to adjust the power at a constant frequency that can be realized, it is possible to suppress the occurrence of interference noise due to the difference in the driving frequency of the adjacent induction heating cooker, and to realize the induction heating cooker with less noise You can do it.

According to a seventh aspect of the present invention, there is provided a pot discriminating means for detecting the type of pot, a plurality of resonance capacitors, and a switching means for switching between the resonance capacitors, and according to the pot determined by the pot discriminating means. The induction heating cooker according to any one of claims 1 to 6, wherein a resonance capacitor is switched to change a frequency of a resonance current.

This makes it possible to effectively heat various pans with one type of heating coil, and to provide a small induction heating cooker as compared with a conventional induction heating cooker that also serves as an aluminum pan. is there.

The present invention according to claim 8 is provided with pan weight discriminating means for detecting the weight of the pan, and when the pan is lighter than the set value, the resonance capacitor is switched by the pan weight discriminating means to increase the resonance current frequency. The induction heating cooker according to any one of claims 1 to 7.

This makes it possible to suppress the phenomenon that the pan is lifted when the pan is light in weight, thereby providing a highly safe induction heating cooker.

[0026]

(Embodiment 1) A first embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 1.

FIG. 1 is a diagram showing a circuit configuration of the induction heating cooker of the present embodiment. This embodiment is different from the conventional example in that the control method of the control means 9 for controlling the switching element 4 is different. The power supply 1 is obtained by rectifying a commercial power supply, and may be used in a non-smooth state or in a form smoothed by an electrolytic capacitor or the like. The smoothing capacitor 2 is connected in parallel with the power supply 1 and functions as a supply source for supplying a high-frequency current. The choke coil 3 is connected to the positive electrode of the power supply 1 and is used for performing zero current switching when the switching element 4 is turned off. A diode 5 is connected to the switching element 4 in parallel, and is used to recirculate the current when the current flows in the opposite direction to the switching element 4. The switching element 4 generates a resonance current that resonates at the resonance frequency of the heating coil 6 and the resonance capacitor 7 when in the ON state, and supplies a high-frequency magnetic field to the pan 8.
The control means 9 causes the switching element 4 to perform control according to the input power using a microcomputer or the like. Here, the driving of the switching element 4 is usually performed at 20 to 30 kHz in consideration of switching loss and the like. On the other hand, the resonance frequency determined by the inductance of the heating coil 6 coupled to the pan 8 and the capacitance of the resonance capacitor is set to be twice or more the operating frequency of the switching element 4, that is, the resonance current having two or more waveforms is obtained by one switching operation. It is a flowing constant. This is intended to generate heat using the characteristic that the skin resistance of the pan is proportional to the square root of the frequency when heating an aluminum pan or the like, and does not increase the skin resistance and increase the switching loss. Things. Also, by using this method, it is possible to increase the magnetic flux that enters the pan by increasing the ampere turn that is usually performed, that is, increasing the diameter of the heating coil, and to suppress the increase in the heating coil diameter, which is a problem in the heating method become.

The operation of the above configuration will be described.
FIG. 2 is a diagram showing waveforms at various points in this embodiment. Waveform (a) shows current waveform Ic flowing through switching element 4 and diode 5, and waveform (b) shows switching element 4
The waveform (c) shows the current IL flowing through the heating coil 6, and the waveform (d) shows the drive waveform VGE applied to the switching element 4 from the control means 9. When a gate signal is given to the switching element 4 by the control means 9, the switching element 4 is turned on. At this time, a resonance current generated by the heating coil 6 and the resonance capacitor 7 flows through the switching element 4. Here, since the frequency of the resonance current is twice or more higher than the driving frequency, the resonance current eventually becomes zero, and the current flows through the diode 5 in the opposite direction. During this time, since the resonance current continues to flow through the heating coil 6, the pan 8 is supplied with a high-frequency magnetic field determined by the resonance frequency. In other words, the same effect as when driving at twice or more the normal frequency can be obtained. Thereafter, after supplying the necessary power, the switching element 4 is turned off at the timing when the current flows through the diode 5, and after a certain period, the switching element 4 is turned on again, and this is repeated.

As described above, according to the present embodiment, it is possible to supply high-frequency power to the pot 8 without increasing the switching loss of the switching element 4, and it is possible to heat the aluminum pan or the multi-layer pan. A heating cooker can be realized.

(Embodiment 2) A second embodiment of the system interconnection inverter device of the present invention will be described with reference to the drawings. This embodiment relates to claim 2.

FIG. 3 is a waveform chart showing the operation of this embodiment. The overall configuration of the present embodiment is the same as that of the first embodiment, and will not be described.

The operation of the above configuration will be described.
In this embodiment, the frequency of the resonance current determined by the heating coil 6 and the resonance capacitor 7 is set to 100 kHz or more.
Here, when heating an aluminum pan or the like, a repulsive force is generated from the magnetic field of the opposite phase generated in the pan and the magnetic field from the heating coil 6, and this is a phenomenon that occurs due to the light element of the pan itself being added thereto.
As shown in FIG. 4, there is a property that the buoyancy decreases as the frequency of the high-frequency magnetic field supplied to the heating coil 6 increases. Here, the problem of pan floating is solved by setting the resonance frequency of the resonance current to 100 kHz or more.

As described above, according to this embodiment, even when the weight of an aluminum pan or the like is light, it is difficult for the pan to float, and a highly safe induction heating cooker can be realized.

(Embodiment 3) A third embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 3.

FIG. 5 is a diagram showing a circuit configuration of this embodiment. The circuit configuration used in the present embodiment is different from that of the first embodiment in that a zero current detecting means 10 for detecting a zero current of the switching element 4 and a counter for counting the number of resonance currents are provided in order to detect a turn-off timing of the switching element 4. 11 means that the control means 9 controls the switching element 4.

The operation of the above configuration will be described.
The zero current detecting means 10 includes a current detecting means such as a current transformer and a flip-flop. The zero current detecting means 10 detects the moment when the current changes from positive to negative, and
It is output to a logic circuit such as a D circuit. The counter 11 counts until a preset number of resonance currents is reached, and outputs when the set value is reached. The control means 9 receives the output from the counter 11 and the output from the zero current detecting means 10, and turns off the switching element 4.

As described above, according to this embodiment, the switching operation can be performed with the required number of resonance currents and zero current reliably, and a highly reliable induction heating cooker with small switching loss can be realized. Things.

(Embodiment 4) A fourth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 1.

FIG. 6 is a waveform chart showing the operation of this embodiment. The overall configuration of the present embodiment is the same as that of the first embodiment, and will not be described.

The operation of the above configuration will be described. In this embodiment, the supply of the high-frequency current to the heating coil 6 is stopped during the off-time, that is, the power is adjusted by the length of the off-time by utilizing the fact that no power is supplied. By using this method, it is possible to control the on-time to be substantially constant, and it is possible to perform power adjustment only by detecting zero current without counting the number of resonance currents. In the method of the present embodiment, the input power increases as the off-time is shorter, that is, as the frequency is higher.

As described above, according to the present embodiment, power can be adjusted while maintaining the number of resonance currents, and an induction heating cooker excellent in controllability can be realized.

(Embodiment 5) A fifth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 5.

FIG. 7 is a waveform chart showing the operation of this embodiment. The overall configuration of the present embodiment is the same as that of the fifth embodiment, and will not be described.

The operation in the above operation will be described. In this embodiment, the input power is controlled by controlling the number of resonance currents. In this method, the smaller the number of resonance currents, that is, the lower the frequency, the larger the input power. Also, in this method, the controllability becomes better as the number of resonance currents at full power increases, so that the resonance current becomes 1
This is an effective control method when the frequency exceeds 00 kHz.

As described above, according to the present embodiment, the range of power adjustment is widened, and an induction heating cooker with excellent controllability can be realized.

(Embodiment 6) A sixth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 6.

FIG. 8 is a waveform chart showing the operation of this embodiment. The overall configuration of the present embodiment is the same as that of the sixth embodiment, and will not be described.

The operation in the above operation will be described. In this embodiment, the drive frequency is made constant by controlling the number of resonance currents and changing the off time. In this method, the off-time is determined by the number of resonance currents, so that the control frequency is constant, though the controllability is poor. However, interference noise between pots, which occurs when there are two burners, is prevented. It becomes possible.

As described above, according to the present embodiment, it is possible to adjust the power at a constant frequency, and it is possible to suppress the generation of interference noise due to the difference in the driving frequency of the adjacent induction heating cookers. Power adjustment at a constant frequency, which can realize an induction heating cooker with low noise, becomes possible,
This makes it possible to suppress the generation of interference noise due to the difference in the driving frequency of the adjacent induction heating cookers, thereby realizing an induction heating cooker with low noise.

(Embodiment 7) A seventh embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 7.

FIG. 9 is a diagram showing a circuit configuration of the present embodiment. The circuit configuration used in the present embodiment is different from that of the first embodiment in that a pan discriminating unit 13 for discriminating the type of pan and a pan discriminating unit 13
In that it has a switching means 12 for switching the capacity of the resonance capacitor 7 in accordance with the type of the pan determined in the above.

The operation in the above configuration will be described.
When the pot 8 is made of magnetic stainless steel or iron, it is desirable that the frequency of the resonance current be lower than the drive frequency as in the conventional example.
This is because when a high-frequency current is applied, the loss generated in the heating coil 6 increases due to the skin effect, so that when the pan 8 is made of iron or the like, the pan can generate enough heat with the specific resistance at the driving frequency. It is. On the other hand, when the pan 8 is an aluminum pan or a multi-layer pan, it is necessary to supply a resonance current several times higher than the driving frequency as described in the first embodiment. Therefore, it is effective to change the frequency of the resonance current depending on the material of the pan and to generate a resonance current corresponding to the pan 8. In addition, in the case of this method, there is no need to switch the heating coil 6 which has been performed by the conventional aluminum pan heating. When the pot 8 is an iron pot or the like, the value of the resonance capacitor 7 increases because the resonance frequency decreases, and when the pot 8 is an aluminum pot, the value of the resonance capacitor 7 decreases. FIG. 10 shows operation waveforms when the pan changes. The most effective resonance current can be selected by selecting the optimum resonance capacitor 7 according to the type of the pot. Here, the pan determining means 13
Various methods are conceivable, such as detection from changes in impedance or frequency of resonance current viewed from the heating coil 6 of the pot.

As described above, according to the present embodiment, it is possible to effectively heat various pots with one type of heating coil, and it is possible to reduce the size of the induction heating cooker compared with the conventional induction heating cooker that also serves as an aluminum pan. A heating cooker is realized.

(Eighth Embodiment) An eighth embodiment of the present invention will be described with reference to the drawings. This embodiment relates to claim 8.

FIG. 11 is a diagram showing a circuit configuration of this embodiment. The difference between the circuit configuration used in the present embodiment and the first embodiment is that the pan weight discriminating means 14 detects the weight of the pan, and the resonance capacitor 7 according to the weight of the pan detected by the pan discriminating means 14.
In that it has switching means 12 for switching the capacity.

The operation of the above configuration will be described.
When the pan 8 is an aluminum pan, a repulsive force is generated from the opposite-phase magnetic field generated in the pan and the magnetic field from the heating coil 6, and a light element of the pan itself is added to the repulsive force to cause a pan floating phenomenon. For this purpose, it is effective to increase the frequency of the high-frequency magnetic field supplied to the heating coil 6 to reduce the buoyancy as shown in FIG. However, increasing the frequency of the resonance current increases the loss of the heating coil 6. Therefore, the weight of the pan is detected by the pan weight discriminating means 14, and only when the weight becomes less than a certain value, the capacity of the resonance capacitor 7 is changed by the switching means 12 to increase the frequency of the resonance current to prevent the floating of the pan. It is effective to do. Here, various methods of the pan weight discriminating means such as a weight sensor and detection of a moment when the pan floats can be considered.

As described above, according to the present embodiment, it is possible to suppress the phenomenon that the pan is lifted when the pan is light in weight, thereby realizing a highly safe induction heating cooker.

[0058]

As is clear from the above embodiment, according to the first aspect of the present invention, high-frequency power can be supplied to the pot 8 without increasing the switching loss of the switching element 4, and An induction heating cooker capable of heating a pan or a multi-layer pan can be realized.

According to the second aspect of the present invention, even when the weight of an aluminum pan or the like is light, pan floating is unlikely to occur,
It is possible to realize a highly safe induction heating cooker.

According to the third aspect of the present invention, the switching operation can be performed with the required number of resonance currents and zero current without fail, and a highly reliable induction heating cooker with small switching loss is realized. You can do it.

Further, according to the present invention, the power can be adjusted while maintaining the number of resonance currents, and an induction heating cooker excellent in controllability can be realized.

According to the fifth aspect of the present invention, the range of power adjustment is widened, and an induction heating cooker excellent in controllability can be realized.

Further, according to the present invention, it is possible to adjust the power at a constant frequency, and it is possible to suppress the generation of interference noise due to the difference in the driving frequency of the adjacent induction heating cookers. It is possible to adjust the power at a constant frequency, which can realize an induction heating cooker with less noise, and it is possible to suppress the generation of interference noise due to the difference in the driving frequency of the adjacent induction heating cooker, An induction heating cooker with low noise can be realized.

According to the seventh aspect of the present invention, it is possible to effectively heat various pans with one kind of heating coil, and it is smaller than a conventional induction heating cooker that also serves as an aluminum pan. This realizes an induction heating cooker.

Further, according to the present invention, it is possible to suppress the phenomenon that the pan is lifted when the pan is light in weight, thereby realizing a highly safe induction heating cooker.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of an induction heating cooker according to a first embodiment of the present invention.

FIG. 2 is a waveform chart showing the operation of each part of the induction heating cooker according to the first embodiment of the present invention.

FIG. 3 is a waveform chart showing the operation of each part of the induction heating cooker according to the second embodiment of the present invention.

FIG. 4 is a diagram showing characteristics of a second embodiment of the present invention.

FIG. 5 is a diagram showing a circuit configuration of an induction heating cooker according to a third embodiment of the present invention.

FIG. 6 (a) is a waveform diagram showing the operation of each unit when the input power of the induction heating cooker according to the fourth embodiment of the present invention is large. (B) The induction heating cooker according to the fourth embodiment of the present invention. Waveform diagram showing the operation of each part when the input power of

FIG. 7A is a waveform diagram showing the operation of each part when the input power of the induction heating cooker according to the fifth embodiment of the present invention is large. FIG. 7B is a waveform diagram showing the operation of the induction heating cooker according to the fifth embodiment of the present invention. Waveform diagram showing the operation of each part when the input power of

FIG. 8 (a) is a waveform diagram showing the operation of each unit when the input power of the induction heating cooker according to the sixth embodiment of the present invention is large. (B) The induction heating cooker according to the sixth embodiment of the present invention. Waveform diagram showing the operation of each part when the input power of

FIG. 9 is a diagram showing a circuit configuration of an induction heating cooker according to a seventh embodiment of the present invention.

FIG. 10A is a waveform diagram showing the operation of each unit when the first pot of the induction heating cooker according to the seventh embodiment of the present invention is used. FIG. 10B is a waveform diagram showing the operation of the seventh embodiment of the present invention. Waveform diagram showing the operation of each part when using the second pan of the cooking device

FIG. 11 is a diagram showing a circuit configuration of an induction heating cooker according to an eighth embodiment of the present invention.

FIG. 12 is a diagram showing waveforms of various parts of a conventional induction heating cooker.

FIG. 13 is a diagram showing an example of a circuit configuration of a conventional induction heating cooker.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply 2 Smoothing capacitor 3 Choke coil 4 Switching element 5 Diode 6 Heating coil 7 Resonant capacitor 8 Pot 9 Control means 10 Zero current detection means 11 Counter 12 Switching means 13 Pot discrimination interruption means 14 Pot weight discrimination means 15 Control means

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Izumi Hirota 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. F term (reference) 3K051 AA07 AB04 AC09 AC12 AC14 AC37 AC39 AD03 AD13 BD07 BD16 CD13 CD14

Claims (8)

[Claims] 1. A smoothing capacitor connected in parallel to a power supply, a choke coil connected to a positive electrode of the power supply, a reverse end of the choke coil, a switching element connected to a negative electrode of the power supply, and a switching element connected in parallel to the switching element. A high-frequency inverter comprising a heating coil and a resonance capacitor arranged in parallel with the connected diode and the switching element and connected in series with each other, a pan heated by receiving a high-frequency magnetic field from the high-frequency inverter, and control means for controlling the switching element An induction heating cooker, wherein a resonance current frequency formed by the heating coil and the resonance capacitor is twice or more higher than a drive frequency of the switching element. 2. The induction heating cooker according to claim 1, wherein the resonance current frequency is 100 kHz or more. 3. The switching device according to claim 1, further comprising a zero current detecting means for detecting a zero current of the resonance current, and a counter for counting the number of times of the zero current passing, wherein the switching element is turned off at a predetermined number of the zero current. Induction heating cooker. 4. The induction heating cooker according to claim 1, wherein the control of the input power is performed during the off time of the switching element. 5. The induction heating cooker according to claim 3, wherein the input power is controlled by changing the number of times the resonance current passes through zero current. 6. The induction heating cooker according to claim 5, wherein the drive frequency of the switching element is constant. 7. A pan discriminating means for detecting the type of pan, a plurality of resonance capacitors, and a switching means for switching between the resonance capacitors, wherein the resonance capacitor is switched according to the pan determined by the pan discriminating means. The induction heating cooker according to any one of claims 1 to 6, wherein the frequency is changed. 8. The apparatus according to claim 1, further comprising pan weight discriminating means for detecting the weight of the pan, wherein said pan weight discriminating means switches a resonance capacitor when the pan is lighter than a set value to increase a resonance current frequency. An induction heating cooker according to any one of the preceding claims.