JP4909980B2 - Electromagnetic induction heating device - Google Patents

Description

  The present invention relates to an inverter type electromagnetic induction heating apparatus that performs induction heating by supplying desired power to an object to be heated of different materials.

  In recent years, an inverter type electromagnetic induction heating apparatus that heats an object to be heated such as a pot without using a fire has been widely used. The electromagnetic induction heating device applies a high-frequency current to the heating coil, generates eddy currents in the heated object made of a material such as iron or stainless steel arranged in the vicinity of the heating coil, and the electric resistance of the heated object itself To generate heat. It is recognized as a new heat source because it can control the temperature of the object to be heated and is highly safe.

  Conventionally, electromagnetic induction heating devices represented by electric cookers and the like incorporated in system kitchens and the like have been used with a resistor such as a sheathed heater, a plate heater, or a halogen heater as a heat source. A part of the heat source is replaced with induction heating, or the whole is replaced with induction heating.

  As a conventional example of such an electromagnetic induction heating apparatus, there is an induction heating cooker as disclosed in Patent Document 1. In this known example, a commercial AC power supply is rectified and smoothed and converted into a DC voltage, a high-frequency current is supplied to the heating coil by a half-bridge inverter, and an object to be heated arranged in the vicinity of the heating coil is induction-heated. To do.

JP 2001-126853 A

  In the example disclosed in Patent Document 1, it is necessary to flow a large current through the heating coil in order to supply sufficient power to the low-resistance object to be heated, which causes heating of the heating coil and an increase in loss of the switching element, Heating efficiency decreases.

  This pattern will be described with reference to the drawings.

  FIG. 24 is a diagram showing the equivalent impedance of the heating coil and the object to be magnetically coupled as seen from the heating coil side, where the horizontal axis represents the equivalent inductance and the vertical axis represents the equivalent resistance. The equivalent impedance varies greatly depending on the material of the object to be heated, such as A in the figure for an object made of iron, B for the object to be heated in nonmagnetic stainless steel, and C in the object to be heated made of copper or aluminum. Indicates. Generally, a high-resistance object to be heated such as A is suitable for induction heating.

  FIG. 25 is a diagram showing the relationship between the input power and the resonance current of the object to be heated having the characteristic of the equivalent impedance shown in FIG. 24, where the horizontal axis represents the input power and the vertical axis represents the resonance current.

  When the target input power is 2 kW, for example, the object to be heated A can obtain an output by flowing a resonance current of about 40 A through the heating coil. However, the object to be heated B needs to pass a current of about 55 A because the resistance is small, and the object to be heated C needs to pass a current of about 140 A because the resistance is even smaller.

  The present invention solves the above-described problems, and an object thereof is to provide an inverter type electromagnetic induction heating apparatus that can efficiently supply desired power to an object to be heated of different materials.

In order to solve the above problems, an electromagnetic induction heating device according to the present invention includes a heating coil that induction-heats an object to be heated, a power supply circuit that generates a DC voltage, and the heating coil that converts the DC voltage into an AC voltage. In the electromagnetic induction heating apparatus including an inverter for supplying power to the power source, the power circuit includes a rectifier circuit that rectifies a commercial AC power source, an inductance connected between the commercial AC power source and an input terminal of the rectifier circuit, and a series circuit. A smoothing circuit formed by a connected capacitor, and a switch means, connecting both ends of the capacitor connected in series and the output terminal of the rectifier circuit, one end of the commercial AC power supply, and a connection point of each capacitor The switch means is connected between them, and the DC voltage based on the output after double voltage rectification of the output voltage of the power supply circuit by the switch means, or full wave rectification Switching to any one of the DC voltages based on the output of the rectifier circuit, comprising a short circuit between the input terminals of the rectifier circuit using the inductance as a load with respect to the commercial AC power supply, the short circuit being a voltage zero cross of the commercial AC power supply The delay time and the energization time are controlled according to the output power by controlling the delay time and the energization time, and when the object to be heated is made of iron, the switch means is turned on to perform the double voltage rectification and the DC voltage When the object to be heated is made of copper or aluminum, the switch means is turned off and full-wave rectification is performed to reduce the DC voltage .

An electromagnetic induction heating apparatus comprising a heating coil that induction-heats an object to be heated, a power supply circuit that generates a DC voltage, and an inverter that converts the DC voltage into an AC voltage and supplies power to the heating coil. The power supply circuit is a rectifier circuit for rectifying a commercial AC power supply, an inductance connected between the commercial AC power supply and an input terminal of the rectifier circuit, and a smoothing circuit formed from a capacitor connected in series, and switch means. Connected to both ends of the capacitors connected in series and the output terminal of the rectifier circuit, the switch means is connected between one end of the commercial AC power supply and the connection point of the capacitors, and the switch means Switch the output voltage of the power supply circuit to either DC voltage based on output after voltage doubler rectification or DC voltage based on output after full-wave rectification The inverter includes a resonant load circuit including the heating coil and a resonant capacitor, and one end of the resonant capacitor is connected to one end of the input terminal of the rectifier circuit, and a voltage generated in the resonant capacitor of the resonant load circuit When the object to be heated is made of iron, the switch means is turned on to perform double voltage rectification to increase the DC voltage, and when the object to be heated is made of copper or aluminum, the switch means Was turned off to perform full-wave rectification to reduce the DC voltage .

  ADVANTAGE OF THE INVENTION According to this invention, the electromagnetic induction heating apparatus of the inverter system which can supply desired electric power efficiently with respect to the to-be-heated material of a different material can be provided.

Embodiments and reference examples of the present invention will be described below with reference to the drawings.

In FIG. 2 and subsequent figures, a part of the configuration common to the reference example of FIG. 1 or FIG. 6 is omitted, and a redundant description is omitted. The same reference numerals in the drawings of each example and reference example indicate the same or equivalent. In addition, when there are two or more of the same objects and it is easier to understand by explaining them, suffixes such as a and b are added to the numerals of the numbers, and in other cases, the suffixes are not added.

[ Reference Example 1 ]
FIG. 1 is a main circuit configuration diagram of an electromagnetic induction heating apparatus as Reference Example 1 .

In FIG. 1, reference numeral 1 denotes a power supply circuit, which is composed of a first power supply 1a and a second power supply 1b in this reference example , and the first power supply 1a and the second power supply 1b generate different DC voltages. The negative electrode sides of both the first and second power supplies 1a and 1b are commonly connected at point o. The positive electrode sides of the first and second power supplies 1a and 1b are defined as p1 point and p2 point, respectively.

  Reference numeral 2 denotes an upper and lower arm, 2a and 2b, which are composed of parts 3 to 5 below, and converts the DC voltage generated by the power supply circuit 1 into an AC voltage to supply power to the resonant load circuit 10 described later. To form an inverter.

  Reference numeral 3 denotes a switching element, which is a component of the upper and lower arms 2, and a power semiconductor switching element such as an IGBT is used. Two elements are connected in series to form the basic structure of the upper and lower arms 2, and the upper potential side is the upper arm. The lower potential side is the lower arm (hereinafter the same).

  The upper and lower arms 2a are connected between the points p1 and o, and the upper and lower arms 2b are connected between the points p2 and o.

The upper and lower arms 2 are not limited to the two examples shown in the present reference example , but there are one example and an example in which two upper arms are also used as a lower arm, which will be described later.

  Reference numeral 4 denotes a diode, which is a component of the upper and lower arms 2 (2a, 2b), and is connected in parallel to each of the four switching elements 3 constituting the upper and lower arms 2 (2a, 2b) in the opposite direction.

  A snubber capacitor 5 is a component of the upper and lower arms 2 (2a, 2b), and is connected in parallel to each of the four switching elements 3 constituting the upper and lower arms 2 (2a, 2b). It is charged or discharged by the interruption current at the time. Since the capacity of the snubber capacitor 5 is sufficiently larger than the output capacity between the collector and the emitter of the switching element 3, the change in the voltage applied to the switching element 3 at the time of turn-off is reduced, and the turn-off loss is suppressed.

Reference numeral 6 denotes a heating coil, which is formed of first and second heating coils 6a and 6b which are divided into two in this reference example , and the object to be heated is inductively heated by the flow of a high-frequency current. Details of the structure of the heating coil 6 will be described later. Further, the configuration of the heating coil 6 is not limited to the example divided into two shown in the present reference example , but includes one example and an example divided into three, which will be described later.

  Reference numerals 7a and 7b denote first and second resonance capacitors. 8a and 8b are switching elements and are connected in anti-series. A diode 9 is connected in parallel to each of the switching elements 8a and 8b in the opposite direction.

A resonant load circuit 10 includes first and second heating coils 6a and 6b, first and second resonant capacitors 7a and 7b, switching elements 8a and 8b in which diodes 9 are connected in reverse parallel, and a not-shown device. It consists of heated objects. Note that the configuration of the resonant load circuit 10 includes not only the configuration of the present reference example but also a configuration in which some components are omitted or added, which will be described later.

  The connection point between the upper arm switching element 3 and the lower arm switching element 3 of the upper and lower arms 2a, that is, the output terminal of the upper and lower arms 2a is defined as d point, and the upper arm switching element 3 and the lower arm switching are operated at the upper and lower arms 2b. A connection point of the element 3, that is, an output terminal of the upper and lower arms 2b is a point.

  Between the point d and the point o, the first heating coil 6a, the first resonance capacitor 7a, and switching elements 8a and 8b connected in reverse series are connected. A diode 9 is connected in parallel in the reverse direction to each of the switching elements 8a and 8b. A connection point between the first heating coil 6a and the first resonance capacitor 7a is a point c, and a second resonance capacitor 7b and a second heating coil 6b are connected in series between the points a and c. .

  Thus, the resonant load circuit 10 including the first and second heating coils 6a and 6b and the first and second resonant capacitors 7a and 7b is sandwiched between the output terminals d and a of the upper and lower arms 2a and 2b. It becomes the composition.

A specific structure of the heating coil 6 will be described with reference to FIG. FIG. 2 is a plan view of a heating coil of the electromagnetic induction heating apparatus which is Reference Example 1. FIG.

  As shown in FIG. 2, the heating coil 6 is formed of a spirally wound conducting wire, and is divided into an inner winding and an outer winding, and the first heating coil 6a is an inner winding and a second heating coil. The coil 6b is formed by an outer winding.

  The first heating coil 6a disposed on the inner side is connected between the points c and d in FIG. 1, and the outer second heating coil 6b is connected between the points b and c in FIG. Yes.

In the above configuration, the overall operation is described, and in this reference example , the output voltage of the power supply circuit 1 is switched by selecting the upper and lower arms 2 (2a, 2b) to be driven according to the material of the object to be heated. Further, it will be described that the number of turns of the driven heating coil and the capacity of the resonant capacitor can be switched.

  Prior to this description, the correspondence between the material of the object to be heated and the number of turns of the heating coil will be described.

  FIG. 3 is a diagram showing the relationship between the number of turns of the heating coil and the equivalent resistance depending on the material of the object to be heated. The horizontal axis is the number of turns of the heating coil, and the vertical axis is the equivalent resistance.

  If the number of turns is increased with the same current flowing through the heating coil, the magnetic flux increases, so the equivalent resistance of the object to be heated as viewed from the heating coil side increases. As described above, the equivalent resistance varies greatly depending on the material of the object to be heated. The object to be heated made of iron is A in the figure, the object to be heated made of nonmagnetic stainless steel is B, and the object to be heated made of copper or aluminum is C-like characteristics are shown.

  Here, in order to set the equivalent resistance value to 1Ω, when the object to be heated has a high resistance such as A, the number of turns of the heating coil is 20 turns, but when the object to be heated has a low resistance such as C, The number of turns will be increased to 50 turns.

In this reference example , for example, the number of turns of the first heating coil 6a is set to 20 turns, the number of turns of the second heating coil 6b is set to 30 turns, and the first and second heating coils 6a and 6b are connected in series. If it can be driven, the total number of turns can be increased to 50 turns.

  That is, the iron heated object is heated by the first heating coil 6a having 20 turns, and the copper or aluminum heated object drives the first and second heating coils 6a and 6b in a serial connection state. Thus, the number of turns can be heated at 50 turns.

  Next, an operation mode in the case of heating an iron object to be heated will be described with reference to FIG.

FIG. 4 is an operation explanatory diagram in Reference Example 1 , and is a timing chart showing the operation of main elements and the voltage and current of main parts.

  The upper half of FIG. 4 shows the operation of each switching element 3, 8 a, 8 b, and for the switching element 3 of the upper and lower arms 2 a, 2 b, the upper and lower arms 2 a, 2 b indicate “for the upper arm” ”Or“ lower ”indicating the lower arm, and the switching elements 8a and 8b are indicated by the reference numerals.

  The lower half of FIG. 4 is the current or voltage that flows through the main element. On Ic2a, the current that flows through the upper arm switching element 3 of the upper and lower arms 2a and the diode 4 connected in reverse parallel thereto, Vd is d in FIG. The voltage at the point, Ic2a, the current flowing in the switching element 3 for the lower arm of the upper and lower arms 2a and the diode 4 connected in reverse parallel thereto, IL6a is the resonance current flowing in the first heating coil 6a.

  The direction from point d to point c in FIG. 1 is defined as positive.

  In FIG. 1, the switching elements 3 for the upper and lower arms of the upper and lower arms 2a are alternately turned on and off, so that the switching elements 8a and 8b are always turned on. The other upper and lower arm 2b always turns off the upper arm switching element 3 and keeps the lower arm switching element 3 on.

(Mode 1)
When the upper arm switching element 3 of the upper and lower arms 2a is turned on and the stored energy of the first heating coil 6a becomes zero, the resonance current IL6a changes its polarity from negative to positive, and the first power source 1a turns on the upper and lower arms 2a. It flows through the path of the diode 9 connected in reverse parallel to the switching element 3 for the upper arm, the first heating coil 6a, the first resonance capacitor 7a, the switching element 8a, and the switching element 8b.

(Mode 2)
Next, when the upper arm switching element 3 of the upper and lower arms 2a is turned off, the resonance current IL6a has a positive polarity, and this current is a snubber capacitor connected in parallel to the upper arm switching element 3 of the upper and lower arms 2a. 5 is discharged, and the snubber capacitor 5 connected in parallel to the lower arm switching element 3 of the upper and lower arms 2a is discharged, and the voltage Vd at the point d gradually decreases.

  After that, when a forward voltage is applied to the diode 4 connected in reverse parallel to the lower arm switching element 3 of the upper and lower arms 2a, the resonance current IL6a is converted into the first heating coil 6a, the first resonance capacitor as a reflux current. 7a, the switching element 8a, the diode 9 connected in antiparallel to the switching element 8b, and the diode 4 connected in antiparallel to the lower arm switching element 3 of the upper and lower arms 2a.

(Mode 3)
Next, when the switching element 3 for the lower arm of the upper and lower arms 2a is turned on and the stored energy of the first heating coil 6a becomes zero, the resonance current IL6a changes in polarity from positive to negative, and the first resonance capacitor 7a, The first heating coil 6a, the lower arm switching element 3 for the upper and lower arms 2a, the switching element 8b, and the diode 9 connected in reverse parallel to the switching element 8a.

(Mode 4)
Next, when the lower arm switching element 3 of the upper and lower arms 2a is turned off, the resonance current IL6a has a negative polarity, and this current is a snubber capacitor connected in parallel to the lower arm switching element 3 of the upper and lower arms 2a. 5 is discharged, the snubber capacitor 5 connected in parallel to the upper arm switching element 3 of the upper and lower arms 2a is discharged, and the voltage Vd at the point d gradually increases.

  Thereafter, when a forward voltage is applied to the diode 4 connected in reverse parallel to the upper arm switching element 3 of the upper and lower arms 2a, the resonance current IL6a is converted into a reflux current as the first heating coil 6a and the upper and lower arms 2a. It continues to flow through the path of the diode 4 connected in antiparallel to the arm switching element 3, the first power source 1a, the switching element 8b, and the diode 9 connected in antiparallel to the switching element 8a.

  By repeating the operation in the above four modes, the first power source 1a can be used as a power source to supply a high-frequency current to the first heating coil 6a and the first resonance capacitor 7a. Induction heating is performed by the magnetic flux generated from the heating coil 6a. The electric power supplied to the object to be heated can be adjusted by controlling the driving frequency of the upper and lower arms 2a.

As in this reference example , the current flowing through the resonant load circuit 10, that is, the resonant current IL6a, becomes a sine wave shape due to the inductance of the first heating coil 6a and the first resonant capacitor 7a, and the phase of the resonant current IL6a is a point d. The phase is delayed from the voltage Vd, that is, the output voltage of the inverter.

  Therefore, when the switching element 3 is turned on, switching (hereinafter referred to as ZVS) is performed in a state where the voltage between the collector and the emitter is zero volts, so that no turn-on loss occurs.

  However, when the power supplied to the object to be heated is reduced, the cut-off current of the upper and lower arms 2a is reduced, and the switching element 3 is turned on before the charging / discharging of the snubber capacitor 5 is completed. appear.

  In such a case, since a turn-on loss occurs in the switching element 3, as shown in FIG. 5, for example, the switch means 11 formed of the switching element in series with the snubber capacitor 5 connected in parallel to the switching element 3 is provided. It is desirable that the snubber capacitor 5 be disconnected from the upper and lower arms 2a by connecting, connecting a diode 12 in reverse parallel to the switch means 11, and turning off the switch means 11. Thereby, in switching of the switching element 3, ZVS can always be realized, and even when the cutoff current is small, the turn-on loss can be eliminated.

  As shown in FIG. 2, since the first and second heating coils 6a and 6b are arranged close to each other, they are magnetically coupled, and when a current flows through the first heating coil 6a, the second heating coil An induced voltage is generated in the coil 6b. Due to this induced voltage, an induced current flows to the second power source 1b via the second heating coil 6b, the second resonant capacitor 7b, and the diode 4 connected in reverse parallel to the upper arm switching element 3 of the upper and lower arms 2b. A route is created.

  Accordingly, by turning on the lower arm switching element 3 of the upper and lower arms 2b, it is possible to prevent the induced current from flowing into the second power source 1b through the path.

  Next, the operation for heating an object to be heated made of copper or aluminum will be described.

  In FIG. 1, the switching elements 3 for the upper and lower arms of the upper and lower arms 2b are alternately turned on and off, and the switching elements 8a and 8b are always turned on. The other upper and lower arm 2a always turns the upper arm switching element 3 off and the lower arm switching element 3 always on.

  Thus, when the upper arm switching element 3 of the upper and lower arms 2b is in the ON state, the second resonance capacitor 7b, the second and first heating coils 6b and 6a, and the lower arm 2a When a current flows through the path of the arm switching element 3 and the lower arm switching element 3 of the upper and lower arms 2b is in the on state, the lower arm switching element 3 and the upper and lower arms 2a of the upper and lower arms 2a from the second resonance capacitor 7b. Current flows through the path of the diode 4, the first and second heating coils 6a and 6b connected in reverse parallel to the lower arm switching element 3.

  Accordingly, the object to be heated is induction-heated by the magnetic flux generated from both the first and second heating coils 6a and 6b.

  As in the case of the upper and lower arms 2a, the ZVS is realized when the upper and lower arms 2b are turned on. Therefore, the turn-on loss of the switching element 3 does not occur. However, as described above, ZVS is satisfied when the output is low. In some cases, it is desirable to disconnect the snubber capacitor 5 by using the switch means 11 and the diode 12 as shown in FIG. 5 as described above, similarly to the upper and lower arms 2a.

  As described above, by selecting the upper and lower arms 2 (2a, 2b) to be driven according to the material of the object to be heated, the output voltage of the power supply circuit 1, the number of turns of the heating coil to be driven, and the capacity of the resonance capacitor are switched. be able to.

  In particular, for copper or aluminum objects to be heated, the number of turns of the heating coil to be driven can be increased, and the current can be reduced by utilizing the increase in equivalent resistance, so the first and second heating coils The loss of 6a, 6b and the switching element 3 can be suppressed, and highly efficient induction heating can be realized.

  Further, the skin resistance of the object to be heated is proportional to the square root of the frequency, and it is effective to increase the frequency when heating the object to be heated such as copper or aluminum. Therefore, it is desirable to set the capacity of the second resonance capacitor 7b so that the upper and lower arms 2b can be driven at a frequency of about 60 kHz, for example.

  On the other hand, in the case of an object to be heated such as iron, if the frequency is high, the equivalent resistance becomes too large, so that no current flows and no power is input. Therefore, it is desirable to set the capacity of the first resonance capacitor 7a so that the upper and lower arms 2a can be driven at about 20 kHz.

[ Reference Example 2 ]
FIG. 6 is a power circuit configuration diagram of an electromagnetic induction heating apparatus as Reference Example 2 , and mainly shows details of the power circuit 1 of FIG. 1 and details of the upper and lower arms 2 (2a, 2b) and the resonant load circuit 10 are omitted. is doing.

  In FIG. 6, 13 is a commercial AC power source. Reference numeral 14 denotes a rectifier circuit, which is composed of a diode bridge, and full-wave rectifies the commercial AC power supply 13. Reference numeral 15 denotes an inductance, and reference numeral 16 denotes a capacitor. These components constitute a smoothing circuit, and the voltage rectified by the rectifier circuit 14 is converted into a smoothed DC voltage.

  The rectifier circuit 14, the inductance 15, and the capacitor 16 constitute a first power source 1a. The first power source 1a reduces the capacity of the capacitor 16 and does not completely smooth the commercial AC power source 13. The input current can be approximated to a sine wave, and harmonics can be reduced.

  For example, as shown in FIG. 7, the unsmoothed DC voltage immediately after rectification varies from 0 to the voltage peak value of the commercial AC power supply 13, and when heating an object to be heated, the upper and lower arms 2a Is driven, a resonance current that fluctuates from 0 to the peak flows through the first heating coil 6a.

  On the other hand, when heating an object to be heated made of copper or aluminum, if induction heating is performed with a high-frequency current that fluctuates from 0 to the peak value as described above, a beat sound caused by the commercial frequency is generated from the object to be heated. To do. Therefore, in order to prevent this, as shown in FIG. 8, it is necessary to smooth the DC voltage and suppress the fluctuation of the resonance current.

  In a generally used capacitor input type smoothing circuit, since many harmonics are included in the input current, a circuit that satisfies both voltage smoothing and harmonic suppression is required.

In the present reference example , the above-described problem can be solved by the boost chopper circuit 17 shown in FIG.

  The step-up chopper circuit 17 includes an inductance 18, a switching element 19, a diode 20, and a capacitor 21. During the ON period of the switching element 19, the voltage of the commercial AC power supply 13 is applied to the inductance 18 to accumulate energy, and the OFF period Energy is released to the capacitor 21 via the diode 20.

  Therefore, by controlling the ON period of the switching element 19 so that the input current of the commercial AC power supply 13 becomes a sine wave, harmonics can be reduced and the DC voltage can be smoothed by the capacitor 21.

  Here, when heating an object to be heated such as copper or aluminum having a low resistance, the equivalent resistance is small as described above, so the number of turns of the heating coil is increased or the equivalent resistance is increased by increasing the frequency. However, there are limitations due to restrictions on the shape of the device and the frequency band that can be used. In a series resonance circuit composed of a heating coil and a resonance capacitor, the Q of the circuit showing the sharpness of resonance changes due to the equivalent resistance, and when the equivalent resistance is small, Q is large and the current flowing through the resonance circuit is also large.

As in this reference example , in a current resonance type inverter in which the current flowing through the resonance circuit is sinusoidal, the resonance current can be limited by making the drive frequency higher than the resonance frequency. However, if the difference between the resonance frequency and the drive frequency is large, the phase difference between the output voltage of the inverter and the resonance current increases, and the cutoff currents of the upper and lower arms 2a and 2b increase, so that the switching loss of the switching element 3 increases.

Therefore, it is desirable to drive the inverter at a frequency close to the resonance frequency to reduce the cut-off current, and the resonance current should be limited by lowering the DC voltage. In this reference example , the step-up chopper circuit 17 as described above is provided to reduce the harmonics of the input current, and the voltage lower limit value of the capacitor 21 is higher than the voltage peak value of the commercial AC power supply 13.

  Therefore, by providing the step-down chopper circuit 22 shown in FIG. 6, the DC voltage can be lowered and the resonance current can be limited.

  The step-down chopper circuit 22 includes a switching element 19, a diode 20, an inductance 18, and a capacitor 21.

  Further, since the step-down chopper circuit 22 can change the voltage of the capacitor 21 of the output unit by controlling the on-time duty of the switching element 19 to be configured, it is possible to perform power control by this voltage change. .

The second power source 1b is composed of the step-up chopper circuit 17 and the step-down chopper circuit 22 in this reference example .

[ Reference Example 3 ]
In the structure in which the heating coil 6 is divided into two as shown in FIG. 2 described above, when heating an object to be heated made of iron, induction heating is performed using only the first heating coil 6a disposed inside. Therefore, when the outer diameter of the object to be heated is large, there is a problem that the heated portion is concentrated on the inner side and uneven heating occurs.

Therefore, an example for solving this problem is this reference example .

FIG. 9 is a plan view of a heating coil of the electromagnetic induction heating apparatus according to Reference Example 3 .

  In FIG. 9, the heating coil 6 has a three-part structure, and is composed of an inner winding 6a1, an intermediate winding 6b, and an outer winding 6a2. The first heating coil 6a is an inner winding. 6a1 and an outer winding 6a2, and the second heating coil 6b is formed of an intermediate winding 6b.

  In the case of heating an object to be heated made of iron, heating unevenness as described above is performed by applying high-frequency current to the inner winding 6a1 and the outer winding 6a2, that is, the first heating coil 6a to perform induction heating. Can be prevented.

In the reference example of FIG. 1, when the heating coil 6 shown in FIG. 9 is applied, as shown in FIG. 10, the inner winding 6a1 and the outer winding 6a2 of the heating coil 6 between the points d and c. Will be connected.

  In FIG. 9, the heating coil 6 has the outer end of the inner winding 6a1 and the outer end of the outer winding 6a2 connected, and the inner end of the outer winding 6a2 and the outer end of the intermediate winding 6b connected. ing. By adopting such a connection method, a high voltage is applied only to the gap between the inner winding 6a1 and the intermediate winding 6b, and the arrangement of the heating coil 6 and the coil base (not shown) for supporting the heating coil 6 are arranged. This structure is designed in consideration of the withstand voltage during this period.

[ Reference Example 4 ]
In the first reference example shown in FIG. 1, when heating an object to be heated, other than the upper and lower arms 2a, switching elements 8a and 8b connected in reverse series and diodes 9 connected in reverse parallel to these are included. A loss occurs because the resonance current flows. In addition, since the induced current due to the coupling between the first and second heating coils 6a and 6b flows to the lower arm switching element 3 of the upper and lower arms 2b and the diode 4 connected in reverse parallel thereto, a loss is also generated here. .

Therefore, an example for solving this problem is this reference example .

FIG. 11 is a main circuit configuration diagram of an electromagnetic induction heating device according to Reference Example 4 .

In FIG. 11, the difference from the reference example 1 (FIG. 1) is that the switching elements 8a and 8b and the diode 4 connected in antiparallel thereto are changed to switch means 27 formed by a relay or the like, and a The switch means 28 formed by a relay or the like is inserted between the point and the second resonance capacitor 7b.

Next, the operation will be described. The same parts as those of the reference example 1 (FIG. 1) are omitted, and different parts will be described.

  When the upper and lower arms 2a are driven to heat the object to be heated, the switch means 27 is turned on and the switch means 28 is turned off. Thereby, the resonance current flows through the first heating coil 6a, the first resonance capacitor 7a, and the switch means 27, and the induced current generated by the induced voltage generated in the second heating coil 6b is completely cut off by the switch means 28. The

Therefore, the loss generated in the switching elements 8a and 8b of the reference example 1 and the diode 4 connected in antiparallel thereto, and the loss generated in the switching element 3 for the lower arm of the upper and lower arms 2b and the diode 4 connected in antiparallel thereto. Loss can be eliminated, and the conversion efficiency of the inverter can be increased.

  On the other hand, when the upper and lower arms 2b are driven to heat an object to be heated made of copper or aluminum, the switch means 27 is turned off and the switch means 28 is turned on.

  Thus, when the upper arm switching element 3 of the upper and lower arms 2b is in the ON state, the switch means 28, the second resonance capacitor 7b, the second and first heating coils 6b and 6a, the upper and lower A current flows through the path of the switching element 3 for the lower arm of the arm 2a.

  When the lower arm switching element 3 of the upper and lower arms 2b is in the ON state, the switch means 28, the lower arm switching element 3 of the upper and lower arms 2b, and the lower arm switching element 3 of the upper and lower arms 2a are switched from the second resonance capacitor 7b. A current flows through the path of the diode 4 and the first and second heating coils 6a and 6b connected in reverse parallel.

[ Reference Example 5 ]
This reference example is an example in which the circuit configuration of the reference example 2 shown in FIG. 6 is simplified.

Figure 12 is a power supply circuit configuration of an electromagnetic induction heating device is a reference example 5, FIG. 13 is a main circuit configuration of an electromagnetic induction heating device is a reference example 5. The same parts as those in FIG. 6 or FIG.

12 differs from the reference example 2 (FIG. 6) in that the step-up chopper circuit 17 and the step-down chopper circuit 22 constituting the second power source 1b in the reference example 2 are replaced by a switching element 19, an inductance 18, a diode 20, and a capacitor. The step-up / step-down chopper circuit 29 is composed of 21.

  In the second power source 1b, that is, the step-up / step-down chopper circuit 29, the voltage of the commercial AC power source 13 is applied to the inductance 18 during the ON period of the switching element 19, and energy is stored. In the OFF period, the energy is accumulated in the capacitor 21. Energy is released.

  Therefore, by controlling the ON period of the switching element 19 so that the input current of the commercial AC power supply 13 becomes a sine wave, harmonics can be reduced and the DC voltage of the capacitor 21 can be changed. Thus, power control can be performed.

  In this way, harmonic reduction and voltage control can be realized with a single chopper circuit (buck-boost chopper circuit 29), which is effective for miniaturization of the circuit.

  However, as shown in FIG. 12, the voltage of the capacitor 21 has a negative potential at the point p2 with respect to the point o. Therefore, the circuit configuration of the main circuit, that is, the inverter is positive with respect to the point o as shown in FIG. The upper and lower arms 2a and 2b are connected to the first power source 1a on the side and the second power source 1b on the negative side, respectively.

In FIG. 13, when heating an object to be heated made of iron, the operation is the same as in Reference Example 4 (FIG. 11) described above, and a description thereof is omitted.

  When the upper and lower arms 2b are driven to heat an object to be heated made of copper or aluminum, the switch means 27 is turned off and the switch means 28 is turned on.

  Thus, when the lower arm switching element 3 of the upper and lower arms 2b is in the ON state, the diode 4 connected in reverse parallel from the second power source 1b to the lower arm switching element 3 of the upper and lower arms 2a, the first and second Current flows through the path of the heating coils 6a and 6b, the second resonance capacitor 7b, the switch means 28, and the lower arm switching element 3 of the upper and lower arms 2b.

  When the upper arm switching element 3 of the upper and lower arms 2b is in the ON state, the second and first heating coils 6b and 6a, the lower arm switching element 3 and the upper and lower arms 2b from the second resonance capacitor 7b. Current flows through the upper arm switching element 3 and the switch means 28.

[ Reference Example 6 ]
In the above-described Reference Example 1 (FIG. 1), Reference Example 4 (FIG. 11), and Reference Example 5 (FIG. 13), when heating an object to be heated made of copper or aluminum, in addition to the upper and lower arms 2b, Since a resonance current flows through the lower arm switching element 3 and the diode 4 connected in antiparallel thereto, a loss occurs.

Therefore, an example for solving this problem is this reference example .

FIG. 14 is a main circuit configuration diagram of an electromagnetic induction heating device according to Reference Example 6 . The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 14, the difference from the reference example 1 (FIG. 1), reference example 4 (FIG. 11), and reference example 5 (FIG. 13) is that the output terminals of the upper and lower arms 2a are the first heating coil 6a and the second heating coil 6a. This is a point connected to a point c which is a connection point of the heating coil 6b. A switching element 3b is connected in anti-series to the upper arm switching element 3 and the lower arm switching element 3 of the upper and lower arms 2a, and a diode 4b is connected to each of the two switching elements 3b in anti-parallel. The point is different.

  When heating an iron object to be heated, the switch means 28 is turned off, the two switching elements 3b of the upper and lower arms 2a are always turned on, and the two upper and lower arm switching elements 3 of the upper and lower arms 2a are turned on and off.

  Thus, when the upper arm switching element 3 of the upper and lower arms 2a is in the ON state, the upper arm diode 4b, the upper arm switching element 3, the first heating coil 6a, from the first power source 1a, A current flows through the path of the first resonant capacitor 7a.

  When the upper arm switching element 3 of the upper and lower arms 2a is in the ON state, the path from the first resonance capacitor 7a to the first heating coil 6a, the lower arm diode 4b of the upper and lower arms 2a, and the lower arm switching element 3 Current flows. The circulating current flows through the upper arm diode 4 of the upper and lower arm 2a and the path of the switching element 3b of the upper arm, or the path of the lower arm diode 4 and the lower arm switching element 3b of the upper and lower arm 2a.

  On the other hand, when heating an object to be heated made of copper or aluminum, the upper and lower arms 2a are turned off and the switch means 28 is turned on to drive the upper and lower arms 2b.

  Thereby, when the upper arm switching element 3 of the upper and lower arms 2b is in the ON state, the upper arm switching element 3, the switch means 28, the second resonance capacitor 7b, the second power source 1b, the second resonance capacitor 7b, the second A current flows through the path of the first heating coils 6b and 6a and the first resonance capacitor 7a.

  When the lower arm switching element 3 of the upper and lower arms 2b is in the ON state, the switching means 28 from the second resonance capacitor 7b, the lower arm switching element 3 of the upper and lower arms 2b, the first resonance capacitor 7a, the first and first A current flows through the path of the second heating coils 6a and 6b.

Therefore, in the reference example 1 , the reference example 4 and the reference example 5 , when heating an object to be heated made of copper or aluminum, the lower arm switching element 3 for the upper and lower arms 2a and the diode connected in reverse parallel thereto. The loss generated in 4 does not occur in this reference example .

However, in this reference example , when the upper and lower arms 2b are driven by moving the upper and lower arms 2a between the first and second heating coils 6a and 6b, a high voltage is applied to each element of the upper and lower arms 2a. Is applied. Therefore, a high breakdown voltage element is required for the upper and lower arms 2a.

  Further, when heating an iron object to be heated, loss occurs in the switching element 3b and the diode 4b added to the upper and lower arms 2a. Therefore, although not shown here, it is effective to reduce the loss by changing the switching element 3b and the diode 4b to high withstand voltage relays and reducing the voltage applied to the upper and lower arm switching elements 3 of the upper and lower arms 2a.

[ Reference Example 7]
In the above-described Reference Example 6 (FIG. 14), the loss when heating the copper or aluminum object to be heated is reduced, but when the iron object to be heated is heated, the switching element 3b as described above. In addition, a semiconductor element such as the diode 4b or a high voltage relay is required.

Therefore, an example for solving this problem is this reference example .

FIG. 15 is a main circuit configuration diagram of an electromagnetic induction heating device according to Reference Example 7 . The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. Further, the first and second power supplies 1a and 1b show only a part of the configuration shown in FIG.

In FIG. 15, the difference from the reference example is that the lower arm of the upper and lower arms 2b is also used as the lower arm of the upper and lower arms 2a.

  Therefore, the output terminal point d of the upper and lower arms 2a and the output terminal point a of the upper and lower arms 2b are connected at a common point, and the resonant load circuit 10 is connected between the points d and o. The resonant load circuit 10 includes a first heating coil 6a, a first resonant capacitor 7a, and a switch means 27 connected in series between a point d and a point o, and the first heating coil 6a and the first resonant capacitor. Assuming that the connection point of 7a is a point c, the second heating coil 6b, the second resonance capacitor 7b, and the switch means 28 are connected in series between the points c and o.

In this reference example , when heating an object to be heated, the switching means 27 is turned on, the switching means 28 and the upper arm switching element 3 of the upper and lower arms 2b are turned off, and the upper arm switching is performed for the upper and lower arms 2a. The lower arm switching element 3 of the element 3 and the upper and lower arms 2b is turned on / off.

  Thus, when the upper arm switching element 3 of the upper and lower arms 2a is in the ON state, the upper arm switching element 3, the first heating coil 6a, and the first resonant capacitor 7a from the first power source 1a. A current flows through the path of the switch means 27.

  When the lower arm switching element 3 of the upper and lower arms 2b is in the ON state, current flows from the first resonance capacitor 7a to the first heating coil 6a, the lower arm switching element 3 of the upper and lower arms 2b, and the switch means 27. Flowing.

  On the other hand, when heating an object to be heated made of copper or aluminum, the switch means 27 and the upper arm switching element 3 of the upper and lower arms 2a are turned off, the switch means 28 is turned on, and the upper and lower arm switching elements 3 of the upper and lower arms 2b are turned on. Turn on and off.

  Thus, when the upper arm switching element 3 of the upper and lower arms 2b is in the ON state, the upper arm switching element 3 of the upper and lower arms 2b, the first and second heating coils 6a and 6b, A current flows through the path of the second resonance capacitor 7 b and the switch means 28.

  When the lower arm switching element 3 of the upper and lower arms 2b is in the ON state, the second and first heating coils 6b and 6a from the second resonance capacitor 7b, the lower arm switching element 3 of the upper and lower arms 2b, and the switch means 28 Current flows through the path.

  Here, in the upper and lower arms 2a and 2b, currents are supplied from different first and second power sources 1a and 1b, respectively. For example, the voltage of the first power source 1a is higher than the voltage of the second power source 1b. In this case, when the upper and lower arms 2a are driven, the diode 4 connected in reverse parallel from the first power source 1a to the upper arm switching element 3 of the upper and lower arms 2a and the upper arm switching element 3 of the upper and lower arms 2b, Current flows in the path of the capacitor 21 of the power source 1b, and a path for charging the capacitor 21 is generated.

  Similarly, when the voltage of the second power source 1b is higher than the voltage of the first power source 1a, when the upper and lower arms 2b are driven, the lower arm switching element 3 from the second power source 1b to the upper and lower arms 2b, A current flows through the path of the diode 4 connected in reverse parallel to the upper arm switching element 3 of the upper and lower arms 2a and the capacitor 16 of the first power supply 1a, and a path for charging the capacitor 16 is generated.

  Therefore, when driving the upper and lower arms 2a, the voltage of the second power source 1b is set higher than the voltage of the first power source 1a in advance, and conversely, when driving the upper and lower arms 2b, The voltage of the power source 1a is set higher than the voltage of the second power source 1b.

  Thereby, the mode which charges each capacitor | condenser 16 and 21 of 1st, 2nd power supply 1a, 1b can be prevented.

[ Reference Example 8 ]
FIG. 16 is a main circuit configuration diagram of an electromagnetic induction heating device according to Reference Example 8 . The same parts as those in FIG. 15 are denoted by the same reference numerals, and description thereof is omitted.

In the above-described Reference Example 7 (FIG. 15), the lower arm of the upper and lower arms 2b is also used as the lower arm of the upper and lower arms 2a. In this reference example , both the upper arm and the lower arm are also used as the upper and lower arms 2b. Switch means 34 is provided between the first power supply 1a and the second power supply 1b and the upper and lower arms 2b, respectively, to switch the output voltage of the power supply circuit 1.

In this reference example , when heating an object to be heated made of iron, the switch means 27 connected to the first resonance capacitor 7a and the switch means 34 connected to the first power supply 1a are turned on, and the second resonance capacitor The switch means 28 connected to 7b and the switch means 34 connected to the second power source 1b are turned off, and the upper and lower arm switching elements 3 of the upper and lower arms 2b are turned on and off.

  Thus, when the upper arm switching element 3 of the upper and lower arms 2b is in the ON state, the switch means 34 connected from the first power source 1a to the first power source 1a, the upper arm switching element 3 of the upper and lower arms 2b, A current flows through the path of the first heating coil 6 a, the first resonance capacitor 7 a, and the switch means 27.

  When the lower arm switching element 3 of the upper and lower arms 2b is in the ON state, current flows from the first resonance capacitor 7a to the first heating coil 6a, the lower arm switching element 3 of the upper and lower arms 2b, and the switch means 27. Flowing.

  On the other hand, when heating an object to be heated made of copper or aluminum, the switch means 27 and the switch means 34 connected to the first power supply 1a are in the OFF state, and the switch means connected to the switch means 28 and the second power supply 1b. 34 is turned on, and the upper and lower arm switching elements 3 of the upper and lower arms 2b are turned on and off.

  Thus, when the upper arm switching element 3 of the upper and lower arms 2b is in the ON state, the switch means 34 connected from the second power source 1b to the second power source 1b, the upper arm switching element 3 of the upper and lower arms 2b, A current flows through the path of the first and second heating coils 6 a and 6 b, the second resonance capacitor 7 b, and the switch means 28.

  When the lower arm switching element 3 of the upper and lower arms 2b is in the ON state, the second and first heating coils 6b and 6a from the second resonance capacitor 7b, the lower arm switching element 3 of the upper and lower arms 2b, and the switch means 28 Current flows through the path.

[ Reference Example 9 ]
FIG. 17 is a main circuit configuration diagram of an electromagnetic induction heating device according to Reference Example 9 . The same parts as those in FIG. 16 are denoted by the same reference numerals, and description thereof is omitted.

In the above-described Reference Example 8 (FIG. 16), the switch means 34 is provided between the first and second power supplies 1a and 1b and the upper and lower arms 2b, respectively, and these are switched to switch the output voltage of the power supply circuit 1. However, this reference example differs from the reference example in that a diode 35 is connected between the second power source 1b and the upper and lower arms 2b and that capacitors 36 are provided at both ends of the upper and lower arms 2b. .

  Therefore, when heating an object to be heated made of copper or aluminum, the switch means 27 and the switch means 34 connected to the first power source 1a are turned off and the switch means 28 is turned on.

  As a result, current is supplied from the second power source 1b to the upper and lower arms 2b via the diode 35. Capacitors 36 provided at both ends of the upper and lower arms 2b regenerate the circulating current flowing through the diodes 4 connected in reverse parallel to the upper arm switching element 3 of the upper and lower arms 2b.

  When the upper arm switching element 3 of the upper and lower arms 2b is turned on, the current is first supplied from the capacitor 36. When the voltage of the capacitor 36 falls below the voltage of the second power source 1b, the second power source 1b passes through the diode 35. Current is supplied.

On the other hand, when heating an object to be heated made of iron, a current is supplied from the first power source 1a to the upper and lower arms 2b via the switch means 34, as in Reference Example 8 (FIG. 16). The details of this operation are almost the same as those in Reference Example 8, and the details are omitted.

FIG. 18 is a circuit configuration diagram of the electromagnetic induction heating device according to the first embodiment . In the above-described reference example, the number of turns of the heating coil and the capacity of the resonant capacitor are switched according to the material of the object to be heated. However, in this embodiment, the number of turns of the heating coil is fixed and only the capacity of the resonant capacitor is switched. Inductively heat the heated object.

  In FIG. 18, the heating coil 6 and the second resonance capacitor 7b are connected between points a and o of the upper and lower arms 2b, and the first resonance capacitor 7a connected in series to the second resonance capacitor 7b. And the switch means 27 are connected in parallel.

  The heating coil 6 increases the number of turns in consideration of a low-resistance object to be heated such as copper or aluminum. However, in the case of an object to be heated such as iron, if the number of turns is large, the equivalent resistance becomes too large, so that no current flows and no power is input.

  Therefore, in this embodiment, as shown in FIG. 18, a power supply circuit 1 including an inductance 15, a rectifier circuit 14, capacitors 16a and 16b connected in series, and a switch means 34 is provided to switch between voltage doubler rectification and full wave rectification. To control the DC voltage.

  That is, when heating an object to be heated made of iron, the switch means 34 is turned on to perform voltage doubler rectification to increase the DC voltage, and when heating an object to be heated made of copper or aluminum, the switch means 34 is turned off. In this state, full-wave rectification is performed to reduce the DC voltage.

  The switch means 27 of the resonant load circuit 10 is turned on when heating an object to be heated made of iron, and turned off when heating an object to be heated made of copper or aluminum.

  About electric power control, the electric current sent through the heating coil 6 is adjusted by adjusting the drive frequency of the upper and lower arms 2b regardless of the material of the object to be heated.

  Here, at the time of voltage doubler rectification, that is, when the switch means 34 is in the ON state, the capacitors 16a and 16b of the power supply circuit 1 are charged only for a half cycle of the commercial frequency, so that the capacity needs to be increased. Accordingly, since the input current includes many harmonics, it is necessary to suppress the harmonics.

  In the present embodiment, a short circuit 37 having an inductance 15 as a load is provided for the commercial AC power supply 13, and the short circuit 37 is operated every half cycle of the commercial frequency to reduce the harmonics of the input current.

  The short circuit 37 includes a rectifier circuit 38 formed of a diode and a switching element 39 formed of a power semiconductor switching element.

Next, the operation of the short circuit 37 will be described with reference to the timing chart shown in FIG. FIG. 19 is a diagram for explaining the operation of the short circuit of the electromagnetic induction heating apparatus according to the first embodiment, showing the operation of the switching element 39, the voltage of the commercial AC power supply 13, and the input current.

  As shown in FIG. 19, the switching element 39 is turned on with a desired delay time from the zero cross of the voltage of the commercial AC power supply 13, starts short-circuit energization, and sucks current from the commercial AC power supply 13. By controlling the delay time and the ON period of the switching element 39 according to the size of the load, that is, the desired output power, harmonics can be reduced.

FIG. 20 is a configuration diagram of a power supply circuit of the electromagnetic induction heating device according to the second embodiment . The same parts as those in FIG. 18 are denoted by the same reference numerals, and description thereof is omitted.

20 is different from the above-described first embodiment (FIG. 18) in that a third power source 40 formed of a step-down chopper circuit 22 is provided at the subsequent stage of the power source circuit 1, and upper and lower arms are connected via a diode 35 and a capacitor 36. The switch means 34 is connected between the point where the current is supplied to 2b to inductively heat the object to be heated made of copper or aluminum, and the output point p1 of the power supply circuit 1 and the positive electrode side of the upper and lower arms 2b. .

  The step-down chopper circuit 22 includes a switching element 19, a diode 20, an inductance 18, and a capacitor 21.

As described in the reference example 2 (FIG. 6), the switching loss of the upper and lower arm switching elements 3 of the upper and lower arms 2b is reduced by driving the upper and lower arms 2b at a frequency close to the resonance frequency and reducing the cutoff current. Therefore, in this embodiment, power control is performed by changing the voltage of the capacitor 21 by the third power source 40, that is, the step-down chopper circuit 22.

  That is, the object to be heated made of copper or aluminum is connected between the rectifier circuit 14 and the switch means 34 connected between the connection points of the capacitors 16a and 16b, and between the point p1 and the positive electrode side of the upper and lower arms 2b. The connected switch means 34 is turned off to perform induction heating.

  On the other hand, the iron object to be heated was connected between the rectifier circuit 14 and the switch means 34 connected between the connection points of the capacitors 16a and 16b, and between the point p1 and the positive electrode side of the upper and lower arms 2b. The switch means 34 is turned on, and current is supplied from the power supply circuit 1 to the upper and lower arms 2b through the switch means 34 connected between the point p1 and the positive electrode side of the upper and lower arms 2b to perform induction heating.

In this embodiment, the current is supplied to the resonant load circuit 10 by driving the upper and lower arms 2b. However, as in the first reference example (FIG. 1), a configuration in which two upper and lower arms 2a and 2b are provided may be used. . In this case, it is possible to delete the switch means 34, the diode 35, and the capacitor 36 that are connected between the point p1 and the positive electrode side of the upper and lower arms 2b.

In the first embodiment (FIG. 18) described above, the short circuit 37 is provided to reduce the harmonics of the input current, but additional components such as a rectifier circuit 38 and a switching element 39 constituting the short circuit 37 are required.

  Therefore, this embodiment is an example for solving this problem.

FIG. 21 is a circuit configuration diagram of an electromagnetic induction heating device according to the third embodiment . The same parts as those in FIG. 18 are denoted by the same reference numerals, and description thereof is omitted.

This embodiment is different from the first embodiment (FIG. 18) in that a path for sucking current from the commercial AC power supply 13 is provided by using the voltage change of the resonant load circuit 10.

  In FIG. 21, an auxiliary resonance capacitor 7c is connected in series with the heating coil 6 and the second resonance capacitor 7b between the points a and o, and the first resonance capacitor 7b is connected in series. The resonance capacitor 7a and the switch means 27 are connected in parallel, and the resonance load circuit 10 is constituted by these.

  Assuming that the connection point between the second resonance capacitor 7b and the auxiliary resonance capacitor 7c is h point, the h point is connected to one end on the input side of the rectifier circuit 14, and an inductance 15 is connected between the commercial AC power supply 13 and the h point. Is connected. That is, since the voltage of the auxiliary resonant capacitor 7c is fed back to one end of the input terminal of the rectifier circuit 14, the inductance 15 and the resonant load circuit 10 appear to the commercial AC power supply 13 as a load circuit.

Further, the short circuit 37 in the first embodiment (FIG. 18) is omitted.

This is the difference from the first embodiment (FIG. 18) described above.

  In the operation of the present embodiment, when the upper and lower arms 2b are driven at a high frequency, the voltage of the auxiliary resonant capacitor 7c, that is, the voltage at the point h changes depending on the resonant current flowing through the resonant load circuit 10, so that the commercial AC Even in a region where the voltage of the power supply 13 is low, the rectifier circuit 14 repeats a conductive state and a non-conductive state.

  As a result, since the input current flows almost over the entire commercial frequency, harmonics can be reduced.

FIG. 22 is a circuit configuration diagram of an electromagnetic induction heating device according to the fourth embodiment . The same parts as those in FIG. 21 are denoted by the same reference numerals, and description thereof is omitted. Although the internal configuration of the upper and lower arms 2b is omitted, it is the same as in the case of FIG.

In this embodiment, the power supply circuit section has the same configuration as that of the second embodiment (FIG. 20), and the resonant load circuit 10 section has the same configuration as that of the third embodiment (FIG. 21).

  As described above, when heating an object to be heated made of copper or aluminum, the upper and lower arms 2b are driven at a frequency close to the resonance frequency in order to reduce the cutoff current and reduce the switching loss, and the third power supply 40 That is, power control is performed using the voltage change of the capacitor 21 due to the operation of the step-down chopper circuit 22.

  On the other hand, when heating an object to be heated made of iron, current is supplied to the upper and lower arms 2b via the switch means 34 connected between the point p1 of the power supply circuit 1 and the positive electrode side of the upper and lower arms 2b to induce induction. Heat.

[ Reference Example 10 ]
In the above-described second embodiment (FIG. 20) and fourth embodiment (FIG. 22), it is possible to lower the lower limit value of the DC voltage by providing the step-down chopper circuit 22 at the subsequent stage of the power supply circuit 1. Additional components such as 18 and switching element 19 are required.

Therefore, an example for solving this problem is this reference example .

FIG. 23 is a circuit configuration diagram of an electromagnetic induction heating device according to Reference Example 10 , and mainly shows a power supply circuit portion.

  In Japan, a 200V commercial AC power supply for consumer electronics is often used as a single-phase three-wire system, and a 100V commercial AC power supply system is connected in series, and 200V is obtained from the voltage at both ends.

  In FIG. 23, reference numeral 13 denotes a commercial AC power supply, which is a single-phase three-wire voltage source, and is configured by connecting two 100 V commercial AC power supplies in series.

  The power supply circuit 1 includes a rectifier circuit 14 formed of a diode bridge for rectifying the commercial AC power supply 13, a smoothing circuit formed of an inductance 15 and capacitors 16a and 16b connected in series, and a switch means 34. .

  Both ends of the capacitors 16a and 16b connected in series are connected to the output terminal of the rectifier circuit 14, one end of the input terminal of the rectifier circuit 14 is connected to the neutral point of the commercial AC power supply 13, and one end of the commercial AC power supply 13 is connected to the capacitor. The switch means 34 is connected between the connection points 16a and 16b.

  In the connection between one end of the input terminal of the rectifier circuit 14 and the commercial AC power supply 13, the connection point of the commercial AC power supply 13 is not the neutral point, but may be configured as one end thereof.

  In the above configuration, by switching the switch means 34, it is possible to switch between 200V voltage doubler rectification and 100V full wave rectification.

  That is, when heating an object to be heated made of iron, the switch means 34 is turned on to perform 200V voltage rectification, the output voltage of the power supply circuit 1 is set to a DC voltage based on the output after voltage rectification, and the DC voltage is increase.

  On the other hand, when heating an object to be heated made of copper or aluminum, the switch means 34 is turned off to perform 100 V full-wave rectification, and the output voltage of the power supply circuit 1 is set to a DC voltage based on the output after full-wave rectification. Reduce the DC voltage.

  Thereby, the upper and lower difference of the DC voltage which the power supply circuit 1 produces | generates can be enlarged, and the response | compatibility with respect to the to-be-heated object of a different material becomes easy.

  Although not shown here, 200 V full-wave rectification can be selected by switching the voltage applied to the rectifier circuit 14 to either a 100 V commercial AC power supply or a 200 V commercial AC power supply.

  In the circuit shown in FIG. 23, since the harmonics of the input current are large, the voltage change of the short circuit 37 as shown in FIGS. 18 and 20 or the resonant load circuit 10 as shown in FIGS. It will be combined with measures against harmonics using.

It is a main circuit block diagram of the electromagnetic induction heating apparatus of Reference Example 1 . It is a top view of the heating coil of the electromagnetic induction heating device of Reference Example 1 . It is a figure which shows the relationship between the number of turns of a heating coil by the difference in the material of to-be-heated material, and an equivalent resistance. 6 is an operation explanatory diagram of Reference Example 1. FIG. It is a figure which shows a part of circuit of the electromagnetic induction heating apparatus of the reference example 1. FIG. It is a power supply circuit block diagram of the electromagnetic induction heating apparatus of the reference example 2 . 10 is a first explanatory diagram of Reference Example 2. FIG. 10 is a second explanatory diagram of Reference Example 2. FIG. It is a top view of the heating coil of the electromagnetic induction heating apparatus of Reference Example 3 . It is explanatory drawing of the reference example 3. FIG. It is a main circuit block diagram of the electromagnetic induction heating apparatus of the reference example 4 . It is a power supply circuit block diagram of the electromagnetic induction heating apparatus of the reference example 5 . It is a main circuit block diagram of the electromagnetic induction heating apparatus of the reference example 5 . It is a main circuit block diagram of the electromagnetic induction heating apparatus of the reference example 6 . It is a main circuit block diagram of the electromagnetic induction heating apparatus of the reference example 7 . It is a main circuit block diagram of the electromagnetic induction heating apparatus of the reference example 8 . It is a main circuit block diagram of the electromagnetic induction heating apparatus of the reference example 9 . It is a circuit block diagram of the electromagnetic induction heating apparatus of Example 1 . It is a figure explaining operation | movement of the short circuit of the electromagnetic induction heating apparatus of Example 1. FIG. It is a power circuit block diagram of the electromagnetic induction heating apparatus of Example 2 . It is a circuit block diagram of the electromagnetic induction heating apparatus of Example 3 . It is a circuit block diagram of the electromagnetic induction heating apparatus of Example 4 . It is a circuit block diagram of the electromagnetic induction heating apparatus of the reference 10 . It is the figure which showed the equivalent impedance of a heating coil and a to-be-heated material. It is a figure showing the relationship between the input electric power and resonance current of the to-be-heated object which has the characteristic of the equivalent impedance shown in FIG.

DESCRIPTION OF SYMBOLS 1 Power supply circuit 1a 1st power supply 1b 2nd power supply 2, 2a, 2b Upper / lower arm 3, 3b Switching element 5 Snubber capacitor 6 Heating coil 6a 1st heating coil 6b 2nd heating coil 7a 1st resonance capacitor 7b Second resonant capacitor 7c Auxiliary resonant capacitor 10 Resonant load circuit 11 Switch means 13 Commercial AC power supply 14 Rectifier circuit 15 Inductance 16 Capacitor 18 Inductance 19 Switching element 20 Diode 21 Capacitor 27, 28, 34 Switch means 35 Diode 36 Capacitor 37 Short circuit Circuit 38 Rectifier circuit 39 Switching element 40 Third power source

Claims (3)

In an electromagnetic induction heating apparatus including a heating coil that induction-heats an object to be heated, a power supply circuit that generates a DC voltage, and an inverter that converts the DC voltage into an AC voltage and supplies power to the heating coil.
The power supply circuit includes a rectifier circuit for rectifying a commercial AC power supply, a smoothing circuit formed from an inductance connected between the commercial AC power supply and an input terminal of the rectifier circuit, and a capacitor connected in series, and a switch unit. And
Connecting both ends of the capacitors connected in series and the output terminal of the rectifier circuit, connecting the switch means between one end of the commercial AC power supply and a connection point of the capacitors, and the switch means of the power supply circuit The output voltage is switched to either a DC voltage based on the output after voltage doubler rectification or a DC voltage based on the output after full-wave rectification ,
Between the input terminals of the rectifier circuit, comprising a short circuit with the inductance as a load for a commercial AC power supply,
The short circuit is short-circuited with a delay time from the voltage zero cross of the commercial AC power supply, and the delay time and energization time are controlled according to the output power,
When the object to be heated is made of iron, the switch means is turned on and voltage rectification is performed to increase the DC voltage. When the object to be heated is made of copper or aluminum, the switch means is turned off. Electromagnetic induction heating device characterized by full-wave rectification and lowering DC voltage . In an electromagnetic induction heating apparatus including a heating coil that induction-heats an object to be heated, a power supply circuit that generates a DC voltage, and an inverter that converts the DC voltage into an AC voltage and supplies power to the heating coil.
The power supply circuit includes a rectifier circuit for rectifying a commercial AC power supply, an inductance connected between the commercial AC power supply and an input terminal of the rectifier circuit, a smoothing circuit formed from a capacitor connected in series, and a switch means. Configured,
Connecting both ends of the capacitors connected in series and the output terminal of the rectifier circuit, connecting the switch means between one end of the commercial AC power supply and a connection point of the capacitors, and the switch means of the power supply circuit The output voltage is switched to either a DC voltage based on the output after voltage doubler rectification or a DC voltage based on the output after full-wave rectification,
Before Symbol inverter comprises a resonant load circuit including a resonance capacitor and the heating coil,
One end of the resonant capacitor is connected to one end of the input terminal of the rectifier circuit, and the voltage generated in the resonant capacitor of the resonant load circuit is fed back .
When the object to be heated is made of iron, the switch means is turned on and voltage rectification is performed to increase the DC voltage. When the object to be heated is made of copper or aluminum, the switch means is turned off. Electromagnetic induction heating device characterized by full-wave rectification and lowering DC voltage . In the electromagnetic induction heating device according to claim 1 or 2,
A step-down chopper circuit is provided between the power supply circuit and the inverter,
The step-down chopper circuit includes an inductance, a switching element, a diode, and a capacitor, and energy is accumulated in the inductance during the ON period of the switching element, and the energy is released to the capacitor via the diode during the OFF period. And
An electromagnetic induction heating apparatus that operates the step-down chopper circuit when the object to be heated is made of copper or aluminum.

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