JP3928587B2 - Induction heating device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating device used in general homes, offices, restaurants, factories, and the like. More specifically, an electromagnetic induction material to be heated is made of a material having low magnetic permeability and high electrical conductivity such as aluminum and copper. The present invention relates to an induction heating device such as a cooking device or a heating device that heats using the principle.
[0002]
[Prior art]
Hereinafter, as an example of a conventional induction heating apparatus, an induction heating apparatus that generates a high-frequency magnetic field from an induction heating coil and heats an object to be heated such as aluminum or a pan by eddy current due to electromagnetic induction will be described.
[0003]
In FIG. 6, a power source 101 is a 200V commercial power source that is a low-frequency AC power source, and is connected to an input terminal of a rectifier circuit 102 that is a bridge diode. A first smoothing capacitor 103 is connected between the output terminals of the rectifier circuit 102. A series connection body of the choke coil 105 and the second switching element 107 is further connected between the output terminals of the rectifier circuit 102. The heating coil 112 is disposed so as to face the aluminum pan 113 which is an object to be heated.
[0004]
Reference numeral 104 denotes an inverter, the low potential side terminal of the second smoothing capacitor 111 is connected to the negative terminal of the rectifier circuit 102, and the high potential side terminal of the second smoothing capacitor 111 is the first switching element (IGBT) 106. The low potential side terminal of the first switching element (IGBT) 106 is connected to the high potential side terminal (collector) of the choke coil 105 and the second switching element (IGBT) 107. Connected to a point. A series connection body of the heating coil 112 and the first resonance capacitor 110 a is connected in parallel to the second switching element 107. Reference numeral 100b denotes a second resonance capacitor, which is connected in parallel to the first resonance capacitor 110a by switching means (relay) 118.
[0005]
The first diode 108 (first reverse conducting element) is connected in antiparallel to the first switching element 106 (the cathode of the first diode 108 and the collector of the first switching element 106 are connected), and the second The diode 109 (second reverse conducting element) is connected to the second switching element 107 in antiparallel.
[0006]
Reference numeral 114 denotes current detection means for detecting an input current flowing from the power supply 101, and the output control means 115 outputs signals to the gates of the first switching element 106 and the second switching element 107 in accordance with the output of the current detection means 114. Is output.
[0007]
Reference numeral 116 denotes voltage detection means for detecting the voltage of the resonant capacitor 110a. The pot type determination means 117 determines the iron load and the aluminum load based on the output of the current detection means 114 and the output of the voltage detection means 116. Do.
[0008]
Reference numeral 119 denotes setting means for setting the start or stop operation of the inverter 104 and the output power, and is configured by a plurality of key switches.
[0009]
In the induction heating apparatus configured as described above, the first switching element 106 and the second switching element 107 are set to have a resonance current frequency at least twice as high as the drive frequency of the first switching element 106 and the second switching element 107, thereby Since the second smoothing capacitor is boosted by the choke coil 105 without increasing the loss of the element 106 and the second switching element 107, a low resistance, low permeability load such as aluminum can be output at a high output. Induction heating is possible.
[0010]
Further, when the pot type determination means 117 determines that the load is iron-based, the second resonance capacitor 110b is connected to the first resonance capacitor 110a, the capacitance of the resonance capacitor is switched, the first switching element 106, By setting the driving frequency of the second switching element 107 to about 23 KHz and controlling the driving time ratio, the iron-based pan can be induction-heated.
[0011]
FIG. 7 shows conditions when the inverter 104 is activated and the pot type determination is performed. The horizontal axis is the output of the current detection means 114, the vertical axis is the output of the voltage detection means 116, and the hatched portion is an area for determining an aluminum pan.
[0012]
FIG. 8 is an operation flowchart of the inverter when the iron pan is heated. When the inverter 104 is activated at step 131 and the pot type determining means 117 determines that the pot is an iron pot at step 132, the inverter 104 is stopped at step 133. Further, it waits for 2.0 seconds in step 134 until the voltage of the resonant capacitor decreases and stabilizes, and in step 135, the switching means 118 turns on the switching relay, thereby switching by adding the resonant capacitor 110b. After waiting for 0.5 seconds in step 136, the inverter 104 is started in step 137. In Step 137 and Step 138, the driving frequency of the first switching element 106 and the second switching element 107 is about 23 KHz, and the driving time ratio is gradually increased until a predetermined power is obtained. In step 139, the inverter 104 stops heating in response to an input from the setting means 119. In step 140, the inverter 104 waits for 2.0 seconds. In step 141, the resonance capacitor is switched to a state in which the aluminum load is heated.
[0013]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-75620
[Problems to be solved by the invention]
In the conventional induction heating cooker, when the inverter is started, the resonance capacitor is switched to a capacity for heating an aluminum load pan, as a load having low resistance and low magnetic permeability such as aluminum. However, when the user often uses an iron load pan rather than an aluminum load pan, the relay ON / OFF frequency for switching the capacity of the resonant capacitor increases extremely, and the relay is A failure may occur. In addition, when switching the relay, the frequency of the resonance capacitor is lowered and stabilized to increase the number of times the inverter is stopped, the time until the predetermined power is reached is slow, and the usability becomes worse during cooking. There was a problem.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention generates a high-frequency magnetic field from a heating coil connected in series with the resonant capacitor by an inverter having a series circuit of a first switching element and a second switching element and a resonant capacitor, and a load in the induction heating apparatus for induction heating, you induction heating iron or stainless steel and the load of the material of low magnetic permeability of the aluminum-based low resistance, such as load and aluminum ferrous material by switching the capacitance of the resonant capacitor and heating means, and switching means for switching the capacity before Symbol co-vibration condenser, a pot type determination means for determining whether the load to be heated by the heating coil is a load of the aluminum-based or a load of the iron-based, depending on whether it is determined load which is a load of the aluminum-based and load of the iron-based by the pan type determination unit, the resonance capacitor by the switching means Switching capacity, which inputs and output control means for performing output control of the driving frequency and the driving time ratio of the first switching element and the second switching element variable to start and stop the heating, and the power for heating Setting means and pot type storage means for storing in the nonvolatile memory data determined by the pot type determination means whether the load is the iron load or the aluminum load even when the power is turned off. and, wherein the output control means, an input of the setting means without switching to hold the selection state before Symbol switching means the resonant capacitor when the user stops heating by the input of the setting means so as to start the inverter In addition, when the power is turned off, the determination result of the pot type determination unit at the previous use is read from the pot type storage unit when the power is turned on next time, and the power is turned off. The inverter is activated by the setting means by selecting and switching the capacity of the resonant capacitor according to whether the last heated load up to that time is the iron load or the aluminum load. Waiting for
[0016]
As a result, failures such as relay contact welding are reduced and durability is improved. In addition, when heating an iron-based load, it is possible to provide an induction heating device that shortens the time required to reach the set power and is easy to use during cooking.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The object of the present invention can be achieved by adopting the configuration described in each claim as an embodiment. Therefore, the following is the significance of the embodiment by describing the operation in the characteristic configuration of each claim. Will be explained in an easy-to-understand manner.
[0018]
According to the first aspect of the present invention, a high-frequency magnetic field is generated from a heating coil connected in series with the resonance capacitor by an inverter including a series circuit of the first switching element and the second switching element and the resonance capacitor. a heating means for stainless induces heating the load of aluminum-based material of low magnetic permeability with a low resistance, such as load and aluminum ferrous material by switching the capacitance of the resonant capacitor, the capacity before Symbol co oscillating capacitor and switching means for switching the load to be heated and the pan type determination means for determining whether the load of the aluminum-based or a load of the ferrous in the heating coil, is determined load by the pan type determination means the switching the capacity of the resonance capacitor by the switching means depending on whether the load of the load or the aluminum-based ferrous, the first of said switching element and the second And output control means for performing output control of the heating means by varying the driving frequency and the driving time ratio of the switching element, a setting means for inputting a start power to stop and heating of the heating, the load by the pan type determination means And a pot type storage means for storing in a non-volatile memory data that determines whether the load is an iron-based load or the aluminum-based load, and the output control means includes the setting means together so as to activate the inverter with the input of said setting means switching unit without switching to hold the selection state of the resonant capacitor when stopping the heating of the heating means by an input, and turns off the power supply When the power is turned on next time, the determination result of the pot type determination means at the time of the previous use is read from the pot type storage means, and the heating is finally performed until the power is turned off. Wherein the load has to wait for the inverter is started by the setting unit switches to select the capacitance of the resonant capacitor depending on whether the load of the aluminum-based or a load of the iron-based was, Even when iron load pans are often used, failures such as relay contact welding are reduced and durability is improved. In addition, when heating an iron-based load, it is possible to provide an induction heating device that shortens the time required to reach the set power and is easy to use during cooking.
[0019]
In addition , since the pot type storage means is stored by a non-volatile memory that retains data even when the power is turned off, after switching on the power, the capacity of the resonant capacitor is switched according to the pot type heated last, Even when the iron-type load pan is used for the first time after the power is turned on, the time required to reach the set power is shortened and the usability is further improved.
[0020]
The invention according to claim 2 particularly has a counting means for counting the number of times the capacity of the resonant capacitor is switched by the switching means, and the heating is stopped when the number of switching times exceeds a predetermined value by the counting means. The inverter is stopped even if it cannot be judged correctly. For example, it is judged as an iron pan during heating of an aluminum pan due to variations in the components that make up the inverter. Since the means switches the capacity of the resonant capacitor, the relay is not repeatedly driven, and the durability is improved.
[0021]
The invention according to claim 3 is a pan that has an abnormality notification means, and cannot be used by stopping the heating and reporting the abnormality when the number of times of switching exceeds a predetermined value by the counting means. I can let you know.
[0022]
The invention according to claim 4 , in particular, the pot type storage means stores the conditions for determining the pot type, the pot type determination means is compared with the previous pot type determination conditions, and is within a predetermined range, Since the heating is stopped, when switching the resonant capacitor by the switching means, even if the load pan is replaced, it can be detected that the load pan has been replaced. .
[0023]
【Example】
Embodiments and reference examples of the present invention will be described below with reference to the drawings.
[0024]
( Reference Example 1)
FIG. 1 is a diagram showing a circuit configuration of an induction heating apparatus of this reference example. The power source 1 is a 200V commercial power source that is a low-frequency AC power source, and is connected to an input terminal of a rectifier circuit 2 that is a bridge diode. A first smoothing capacitor 3 is connected between the output terminals of the rectifier circuit 2. A series connection body of the choke coil 5 and the second switching element 7 is further connected between the output terminals of the rectifier circuit 2. The heating coil 12 is disposed so as to face the aluminum pan 12 which is an object to be heated.
[0025]
Reference numeral 4 denotes an inverter, the low potential side terminal (emitter) of the second smoothing capacitor 11 is connected to the negative terminal of the rectifier circuit 2, and the high potential side terminal of the second smoothing capacitor 11 is the first switching element (IGBT). ) 6 is connected to the high potential side terminal (collector), and the low potential side terminal of the first switching element (IGBT) 6 is the high potential side terminal (collector) of the choke coil 5 and the second switching element (IGBT) 7. Connected to the connection point. A series connection body of the heating coil 12 and the first resonance capacitor 10 a is connected in parallel to the second switching element 7. Reference numeral 10b denotes a second resonance capacitor, which is connected in parallel to the first resonance capacitor 10a by a switching means (relay) 18.
[0026]
The first diode 8 (first reverse conducting element) is connected in antiparallel to the first switching element 6 (the cathode of the first diode 8 and the collector of the first switching element 6 are connected), and the second The diode 9 (second reverse conducting element) is connected to the second switching element 7 in antiparallel.
[0027]
Reference numeral 14 denotes current detection means for detecting an input current flowing from the power source 1, and the output control means 15 sends signals to the gates of the first switching element 6 and the second switching element 7 in accordance with the output of the current detection means 14. Is output.
[0028]
Reference numeral 16 denotes voltage detection means for detecting the voltage of the first resonance capacitor 10a, and the pan type determination means 17 is configured to use an iron load and an aluminum load depending on the output of the current detection means 14 and the output of the voltage detection means 16. Judgment is made.
[0029]
Reference numeral 19 denotes a setting means for setting the start or stop operation of the inverter 4 and the output power, and is constituted by a plurality of key switches.
[0030]
The operation of the induction heating apparatus configured as described above will be described below. The power source 1 is full-wave rectified by a rectifier circuit 2 and supplied to a first smoothing capacitor 3 connected to the output terminal of the rectifier circuit 2. The first smoothing capacitor 3 serves as a supply source for supplying a high-frequency current to the inverter.
[0031]
While the second switching element 7 is being driven, the first switching element 7 resonates in a closed circuit formed by the second switching element 7, the second diode 8, the heating coil 12, and the resonant capacitor 10. The first switching element 7, the first diode 8, the heating coil 12, and the resonant capacitor 10 resonate with each other during the driving. When the second switching element 7 is turned off, the choke coil 5 boosts the second smoothing capacitor, so that a low-resistance, low-permeability load such as aluminum can be induction-heated with high output.
[0032]
In this reference example, the driving time of the heating coil 12, the resonant capacitor 10, and the first switching element 6 and the driving time of the second switching element 7 are set so that the resonance period is 2/3 of the driving time. Therefore, if the drive frequency is about 20 kHz, the frequency of the resonance current is about 60 kHz.
[0033]
When heating an iron-based load, the switching means 18 connects the second resonant capacitor 10b in parallel to the first resonant capacitor 10a, makes the drive frequency constant (23 KHz), and changes the drive time ratio. Thus, predetermined power is supplied.
[0034]
In this reference example, the driving frequency of the first switching element 6 and the second switching element 7 uses the PWM function built in the microcomputer, and the driving frequency is set by setting the driving cycle inside the microcomputer. Realized. The output of the current detection means 14 and the output of the voltage detection means 16 are input to the microcomputer using an AD conversion function built in the microcomputer.
[0035]
FIG. 2 is an operation flowchart of the inverter when the iron pan is heated. When the inverter 4 is activated at step 31 and the pot type determining means 17 determines that the pot is an iron pot at step 32, the inverter 4 is stopped at step 33. Further, it waits for 2.0 seconds in step 4 until the voltage of the resonant capacitor decreases and stabilizes, and in step 35, the switching means 18 turns on the switching relay, thereby switching by connecting the resonant capacitor 10b. After waiting for 0.5 seconds in step 36, the inverter 54 is started in step 37. In step 37 and step 38, the driving frequency of the first switching element 56 and the second switching element 57 is about 23 KHz, and the driving time ratio is gradually increased until a predetermined power is obtained. In step 39, the inverter 4 stops heating by the input of the setting means 19. At this time, by the switching means 18, depending on pot type stored the output of the switching relay in a pan type storage means 20, since no switching, the input of the setting means 19, to start the inverter 4, the load of iron-based The inverter 4 is started from a state where the heater is heated.
[0036]
As described above, according to this reference example, in an inverter that heats a low resistance, low magnetic permeability load such as aluminum and a load such as iron or stainless steel, a user often uses an iron load pan. In this case, since the number of times of switching the resonance capacitor is reduced, the failure of the relay due to contact welding or the like is less likely to occur, and the stop time of the inverter accompanying the switching of the relay is reduced, so that an easy-to-use induction heating device can be provided. Is.
[0037]
(Example 1 )
The second embodiment of the present invention has the same configuration as that of the first reference example. In FIG. 1, a non-volatile storage element that retains data even when the power is turned off is used as the pot type storage means 20. It is a difference.
[0038]
FIG. 3 is an operation flowchart of the inverter after the power is turned on. After the power is turned on in step 41, the result of the pot type determination means 17 at the previous use is read from the non-volatile memory which is the pot type storage means 20, and if an iron load is used, the resonance capacitor is switched in step 43 And waits for 0.5 seconds in step 44, and waits for the inverter 4 to be activated by the setting means 19 in a state where the iron-based load can be immediately heated. If the load pan used last time in step 42 is an aluminum pan, the setting means 19 waits for the inverter 4 to be activated in a state where the aluminum load can be heated immediately.
[0039]
The external storage means may be a storage element that retains data even when the power is turned off.
[0040]
As described above, according to the present embodiment, even after the power is turned on, the inverter can be heated immediately in advance according to the previously used load pan, so the start-up of the inverter is accelerated and the usability is improved.
[0041]
(Example 2 )
In the second embodiment of the present invention, the counting means 21 is added to the first reference example.
[0042]
In Figure 1, 21, by the output control unit 15, a count hand stage switching unit 18 counts the number of times of driving the relay to switch the resonant capacitor.
[0043]
FIG. 4 is a flowchart when the resonance capacitor is continuously switched by the switching unit 18 in accordance with the determination result of the pot type determination unit 17. After starting heating from the state of heating the aluminum load pan, in step 51, the counter means 21 initializes (sets to 0) the counter. When the inverter 4 is activated at step 52 and the pot type determination means 17 determines that the pot is an iron pot at step 53, a resonance capacitor switching operation is performed at step 54. (Resonance capacitor switching operation stops inverter 4 and waits for 2.0 seconds, then switches the resonance capacitor, and further performs standby operation for 0.5 seconds.) In step 55, counting means 21 sets the count value to 1. If the count value is 5 times or more in step 56, the heating is stopped. If the count value is less than 5 times in step 56, the inverter 4 is started in step 57. If the pot type determining means 17 determines that the pot is an aluminum pot in step 53, a resonance capacitor switching operation is performed in step 59. In step 60, the counting means 21 increases the count value by one, and if the count value is 5 times or more in step 61, heating is stopped. If the count value is less than 5 times in step 56, the inverter 4 is activated in step 62 and the process proceeds to step 53.
[0044]
As described above, according to the present embodiment, heating is stopped when it is determined that the load pan is neither aluminum-based nor iron-based due to variations in each part constituting the inverter 4, so that the relay as a switching means is There is no longer continuous driving, and an induction heating device with few failures can be realized.
[0045]
(Example 3 )
The third embodiment of the present invention is obtained by adding the abnormality notifying means 22 to the second embodiment of the present invention.
[0046]
FIG. 5 is a display example of the abnormality notifying means 22 when the heating is stopped because the count value reaches the predetermined number of times by the counting means 21, and by displaying “H43” in the time display area of the LCD, Inform the user of the cause of the heating stop.
[0047]
In this embodiment, it is displayed on the LCD, but it may be displayed by an LED element, and it is even better to notify by a buzzer.
[0048]
As described above, the user can know the cause of the heating stop, and the pan that cannot be used can be identified.
[0049]
(Example 4 )
The fourth embodiment of the present invention has the same configuration as that of the second embodiment of the present invention, and the pot type storage means 20 has a current detection means 14 and voltage detection at the time when the pot type determination means 17 detects the pot type. The difference is that the output value of the means 16 is stored.
[0050]
In FIG. 4, the output values of the current detection means 14 and the voltage detection means 16 at the time when the pot type determination means 17 detects the pot type in step 53 and step 58 are stored. Next, at step 53 and step 58, when the pot type determination means 17 detects the pot type, the output values of the current detection means 14 and the voltage detection means 16 and the previously stored output values of the current detection means 14 and the voltage detection means 16 are as follows. If both the differences are at a predetermined value (in this embodiment, the microcomputer 8-bit AD conversion value is ± 5 or more), it is determined that the pan has changed from the previous time, and the counting means 21 counts. Initialize the value.
[0051]
As described above, even when the load pan is changed when the inverter is stopped during the resonance capacitor switching operation, the counting means 21 initializes the counter, and therefore can more accurately determine that the pan cannot be heated.
[0052]
【The invention's effect】
As is apparent from the above description, according to the present invention, when the heating is stopped, the switching means does not switch the capacity of the resonant capacitor, so that failure such as contact welding of the relay as the switching means is reduced and durability is improved. Improves. In addition, when heating an iron-based load, it is possible to provide an induction heating device that shortens the time required to reach the set power and is easy to use during cooking.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing a configuration of an induction heating apparatus according to a first reference example of the present invention. FIG. 2 is a flowchart showing a capacity switching operation of a resonance capacitor of the induction heating apparatus according to the first reference example. FIG. 4 is a flowchart showing the capacity switching operation of the resonance capacitor when the induction heating apparatus of the first embodiment of the present invention is turned on. FIG. 4 shows the capacity switching operation of the resonance capacitor of the induction heating apparatus of the second embodiment of the present invention. FIG. 5 is a schematic diagram of an abnormal display example of the induction heating apparatus according to the third embodiment of the present invention. FIG. 6 is a circuit block diagram showing the configuration of the induction heating cooker of the conventional example. FIG. FIG. 8 is a flowchart showing the pot type determination threshold value of the heating device. FIG. 8 is a flowchart showing the capacity switching operation of the resonance capacitor of the induction heating device of the conventional example.
4 Inverter 6 First switching element 7 Second switching element 10 Resonant capacitor 12 Heating means 14 Current detection means 15 Output control means 16 Voltage detection means 17 Pot type determination means 18 Switching means 19 Setting means 20 Pot type storage means 21 Count Means 22 Abnormality notification means

Claims (4)

A high frequency magnetic field is generated from a heating coil connected in series with the resonance capacitor by an inverter having a series circuit of the first switching element and the second switching element and an inverter, and an iron-based load made of iron or stainless steel. and switching means for switching a heating means for induction heating and the load of the material of the aluminum-based low-permeability with a low resistance such as aluminum by switching the capacitance of the resonant capacitor, the capacity before Symbol co oscillation capacitor, with the heating coil A pot type determining means for determining whether the load to be heated is the iron-based load or the aluminum-based load , and the load determined by the pot type determining means is the iron-based load or the aluminum-based load. switching the capacity of the resonance capacitor by the switching means in accordance with a either a load, the driving of the first switching element and the second switching element And output control means for performing output control of the variable to the heating means to the wave number and the driving time ratio, setting means for inputting a start power to stop and heating of the heating, the load is the iron-based by the pan type determination means A pot type storage means for storing in a non-volatile memory even if the power is turned off, and determining whether the load is an aluminum load or the aluminum load, and the output control means is configured to input the setting means by the input of the setting means when the switching means when stopping the heating of the heating means which is turned off with, the power supply so as to start the inverter the input of the setting means without switching to hold the selection state of the resonant capacitor, the following When the power is turned on, the determination result of the pot type determination means at the time of previous use is read from the pot type storage means, and the last heated load until the power is turned off is the iron-based Induction heating apparatus that wait for the inverter is started by the setting unit switches to select the capacitance of the resonant capacitor depending on whether the load of either a load the aluminum-based. It has a counting means for counting the number of times of switching the capacitance of the resonance capacitor by the switching means, control means, according to claim 1 in which the count number of said counting means stops heating the heating means exceeds a predetermined value Induction heating device. The induction heating according to claim 2 , further comprising an abnormality notification unit, wherein the control unit stops heating of the heating unit when the count number of the counting unit exceeds a predetermined value, and notifies the abnormality by the abnormality notification unit. apparatus. The pot type storage means stores the conditions for determining the pot type, and when the pot type determination means is within a predetermined range compared with the previous pot type determination condition, the control means stops heating the heating means. Item 4. The induction heating device according to any one of Items 1 to 3 .

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