JP2011044422A - Induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an induction heating cooker equipped with a plurality of heating ports which suppresses interference noises when two of the heating ports are simultaneously driven. <P>SOLUTION: The induction heating cooker includes a central resonance circuit 28 comprising resonance capacitors 24, 26 serially connected with a central heating coil 21 and a central heating coil 21, a right resonance circuit 34 comprising a resonance capacitor 33 serially connected with a right heating coil 31 and a right heating coil 31, a capacity switching means ( relays 25, 27, a controlling circuit 11) for switching a capacity of the central resonance circuit 28 in accordance with a driving frequency of the right resonance circuit 34, and a controlling circuit 11 for controlling the driving frequency of the central resonance circuit 28 so that a difference between the driving frequency of the central resonance circuit 28 and that of the right resonance frequency 34 may become a value either in a predetermined low-frequency region or a high-frequency region. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heating cooker provided with a plurality of heating ports.

  In recent years, induction cooking devices having a plurality of heating ports have become widespread. In such an induction heating cooker, each heating port has a heating coil, and a heating output set by driving the heating coil at a predetermined oscillation frequency is obtained. However, when a plurality of heating ports are used at the same time, an interference sound having a frequency corresponding to the difference between the oscillation frequencies of the heating coils is generated.

  In order to reduce this interference noise, “the inverter of at least two induction heating units supplies power of a frequency of 50 kHz or more to the heating coil at least at the maximum heating output, and the load is made of a magnetic material or a low conductivity material. Have been proposed (see, for example, Patent Document 1).

JP 2007-234278 (2nd page, 3rd page, FIG. 1)

  However, in the induction heating cooker of the above-mentioned patent document 1, since power having a frequency of 50 kHz or more is supplied to the heating coil, the switching loss of the inverter increases and the heat generation also increases, so that the cooling means for cooling the circuit components. Also increased.

  The present invention has been made to solve the above-described problems, and suppresses the interference sound when two heating ports are driven simultaneously in an induction heating cooker having a plurality of heating ports. An induction heating cooker that can be used is obtained.

  An induction heating cooker according to the present invention includes a first resonance circuit including a first heating coil and a resonance capacitor connected in series to the first heating coil, and a second heating coil and the second heating coil in series. A second resonance circuit including a connected resonance capacitor; capacity switching means for switching a capacity of the first resonance circuit according to a driving frequency of the second resonance circuit; A first high-frequency power supply unit that supplies the first resonance circuit; a second high-frequency power supply unit that converts a direct current into a high-frequency current and supplies the second resonance circuit; and a driving frequency of the first resonance circuit and the second resonance And a control unit that controls the drive frequency of the first resonance circuit so that the difference from the drive frequency of the circuit becomes a value in a predetermined low frequency region or high frequency region.

  According to the induction heating cooker according to the present invention, the drive frequency of the first resonance circuit is controlled so that the difference between the drive frequencies of the two resonance circuits becomes a value in a predetermined low frequency region or high frequency region. To do. For this reason, an irritating interference sound can be reduced, and the drive frequency does not become too high.

3 is a top view of the induction heating cooker according to Embodiment 1. FIG. It is a circuit block diagram of the induction heating cooking appliance which concerns on Embodiment 1. FIG. It is a figure which shows the capacity | capacitance of the resonant capacitor circuit which concerns on Embodiment 1, and the ON / OFF state of a relay. It is a figure which shows the relationship between the frequency of an interference sound, and a user's audibility. It is a discrimination | determination characteristic view of the pan load based on the relationship between the input electric power of a heating coil, and an electric current value. FIG. 3 is a diagram illustrating a relationship between a driving frequency and power of the central driving circuit according to the first embodiment. 4 is a flowchart showing a control operation of a drive frequency of the central drive circuit according to the first embodiment. It is a circuit block diagram of the induction heating cooking appliance which concerns on Embodiment 2. FIG. FIG. 6 is a diagram illustrating a relationship between a driving frequency and power of a central driving circuit according to a third embodiment. It is a figure which shows the relationship between the target electric power of the center heating port which concerns on Embodiment 3, and the synthetic capacity of a resonance capacitor circuit. 10 is a flowchart showing a control operation of a drive frequency of a central drive circuit according to the third embodiment. It is a top view of the induction heating cooking appliance which concerns on Embodiment 4. It is a block diagram of the heating coil of the induction heating cooking appliance which concerns on Embodiment 4. FIG. It is a circuit block diagram of the induction heating cooking appliance which concerns on Embodiment 4. It is a figure which shows the small diameter pan mounting state of the induction heating cooking appliance which concerns on Embodiment 4. FIG. It is a figure which shows the large diameter pan mounting state of the induction heating cooking appliance which concerns on Embodiment 4. FIG.

Embodiment 1 FIG.
FIG. 1 is a top view of induction heating cooker 100 according to Embodiment 1 of the present invention. The induction heating cooker 100 has a heat-resistant top plate 1 on which a pan is placed, and has a total of three heating ports, a central heating port 2, a right heating port 3, and a left heating port 4. A central heating coil 21, a right heating coil 31, and a left heating coil 41 are installed at the lower part of each heating port, and vortices are placed in the pans placed on the heating ports by the high-frequency magnetic field generated from each heating coil. An electric current is generated to inductively heat the pan.

  The induction heating cooker 100 includes an operation display unit 5. The operation display unit 5 includes a power switch, an input switch for adjusting heating power, selecting a heating port, and the like, and a display device configured to display a heating state. When the user turns on the power switch and operates the input switch, the heating state is displayed on the display device.

FIG. 2 is a circuit configuration diagram of the induction heating cooker 100 and shows a circuit of the central heating port 2 and the right heating port 3. The circuit of the left heating port 4 is not shown, but has the same configuration as the right heating port 3.
In FIG. 2, the induction heating cooker 100 includes a commercial power source 12, rectifier circuits 13, 14, a central drive circuit 20 corresponding to the central heating port 2, a right drive circuit 30 corresponding to the right heating port 3, a control circuit 11, and an operation. A display unit 5 is provided.

(Control part)
The control circuit 11 is a control unit that performs heating control and the like of the three heating ports of the induction heating cooker 100 based on an input from the user to the operation display unit 5. The control operation of the control circuit 11 will be described later.

(Rectifier circuit)
The rectifier circuits 13 and 14 are connected to the commercial power supply 12, and the AC power input from the commercial power supply 12 is full-wave rectified to be converted into DC power and supplied to the central drive circuit 20 and the right drive circuit 30, respectively. The rectifier circuit 13 includes a diode bridge 131, a choke coil 132, and a smoothing capacitor 133. Similarly, the rectifier circuit 14 includes a diode bridge 141, a choke coil 142, and a smoothing capacitor 143.

(Central drive circuit 20)
The central drive circuit 20 includes a central resonance circuit 28 including a central heating coil 21 that is a first heating coil and a resonant capacitor circuit 23 whose capacity can be switched, and an inverter circuit 22. The first resonance circuit of the present invention corresponds to the central resonance circuit 28 in the first embodiment.
The inverter circuit 22 is composed of a switching element such as an IGBT, and the switching operation of the switching element converts the direct current output from the rectifier circuit 13 into a high-frequency current of about several tens of kHz to resonate with the central heating coil 21. This is supplied to the capacitor circuit 23. The inverter circuit 22 is a general frequency control type inverter that controls the output by changing the driving frequency, and the control circuit 11 energizes the inverter circuit 22 so that the thermal power set in the operation display unit 5 is obtained. Take control.

(First resonance circuit, capacitance switching means)
In the resonance capacitor circuit 23, a resonance capacitor 24 and a resonance capacitor 26 are provided in parallel. The resonance capacitor 24 and the resonance capacitor 26 are connected in series with a relay 25 and a relay 27 as switching means, respectively. That is, the series connection circuit of the resonance capacitor 24 and the relay 25 and the series connection circuit of the resonance capacitor 26 and the relay 27 are connected in parallel to constitute the resonance capacitor circuit 23. The ON / OFF states of the relay 25 and the relay 27 are controlled by the control circuit 11 corresponding to the capacity switching control unit of the present invention.

  FIG. 3 is a diagram showing the relationship between the combined capacitance of the resonant capacitor circuit 23 and the ON / OFF states of the relays 25 and 27. In the present invention, “switching the capacitance of the first resonance circuit” means switching the combined capacitance of the resonance capacitor circuit 23.

When both the relays 25 and 27 are ON, the resonance capacitor circuit 23 becomes the combined capacity A, and the resonance capacitor 24 and the resonance capacitor 26 are connected in parallel to the central heating coil 21.
When the relay 25 is ON and the relay 27 is OFF, the resonance capacitor circuit 23 has a combined capacity B, and the resonance capacitor 24 is connected to the central heating coil 21 alone.
When the relay 25 is OFF and the relay 27 is ON, the resonance capacitor circuit 23 has a combined capacity C, and the resonance capacitor 26 is connected to the central heating coil 21 alone.

  Thus, the resonance capacitor circuit 23 can take three types of combined capacitance values A, B, and C by ON / OFF control of the relays 25 and 27 by the control circuit 11. Here, the capacity switching means of the present invention corresponds to the control circuit 11 and the relays 25 and 27 in the first embodiment.

(Right drive circuit 30)
The right drive circuit 30 includes a right heating circuit 31 that is a second heating coil, a right resonance circuit 34 that includes a resonance capacitor 33, and an inverter circuit 32. The inverter circuit 32 is a frequency control type inverter having a configuration similar to that of the inverter circuit 22 described above, and is energized and controlled by the control circuit 11. The second resonance circuit of the present invention corresponds to the right resonance circuit 34 in the first embodiment.

(Load pan judgment means)
As a pan that can be placed on each heating port as a heating target, a magnetic pan that can be heated by the induction heating cooker 100, a high-resistance non-magnetic pan (hereinafter simply referred to as a non-magnetic pan), and a low resistivity. Therefore, there is a pan made of aluminum or copper which cannot be heated by the induction heating cooker 100. Moreover, heating may be instruct | indicated by the operation display part 5 in a no-load state without mounting a pan. When induction heating is performed in the same way as a magnetic pan or non-magnetic pan with an unloaded state or a pan made of aluminum, copper, etc., excessive current flows to the heating coil, etc. May cause damage. For this reason, even if the user operates the operation display unit 5, the induction heating operation is not started immediately, and the pan type of the pan placed on each heating port is determined.

  Taking the case where a pan is placed on the central heating port 2 as an example, the operation for determining the pan type will be described. When a pan is placed on the central heating port 2, the control circuit 11 as the load pan determination means of the present invention controls the inverter circuit 22 to apply a voltage to the central resonance circuit 28. A resonance current flows through the central resonance circuit 28 to which a voltage is applied, and the type of pan is determined by detecting this resonance current. The current value of the current flowing through the central heating coil 21 is detected by a known method using current detection means such as a current transformer provided in the rectifier circuit 13 and the central drive circuit 20, respectively.

  FIG. 5 is a discrimination characteristic diagram of the pan load based on the relationship between the input power to the heating coil and the current value of the heating coil. Since the impedance on the output side seen from the inverter differs depending on the pan type placed on the heating port, if input power and heating coil current are used as parameters, magnetic pan, non-magnetic pan, aluminum / copper pan, no load Four types can be discriminated.

  Therefore, when heating is instructed by the user, the control circuit 11 determines the pot type based on the input power value detected as described above and the current of the heating coil. When no load is detected or when an aluminum / copper pan is detected, the operation display unit 5 and a buzzer (not shown) notify the user, and the inverter circuit 22 is not energized. Further, when a magnetic pan or a non-magnetic pan is detected, energization control of the inverter circuit 22 is performed based on the heating power setting in the operation display unit 5.

  The basic operation of the induction heating cooker 100 configured as described above will be described. Here, a case where heating is performed at the right heating port 3 will be described as an example. When the pan is placed on the right heating port 3 of the top plate 1 and the heating power is set in the operation display unit 5, the control circuit 11 determines the pan type as described above. And if it is a pan which can be heated, the energization control to the inverter circuit 32 will be performed according to the heating power set in the operation display part 5, and a voltage will be applied to the right heating coil 31 and the resonance capacitor 33. By applying a voltage from the inverter circuit 32, a high-frequency resonance current flows through the right heating coil 31 and the resonance capacitor 33 constituting the series resonance circuit. This electric current generates a high frequency magnetic field in the right heating coil 31, and this high frequency magnetic field generates an eddy current at the bottom of the pan placed on the right heating port 3, whereby the pan is induction heated.

  Next, the operation when the central heating port 2 is operated during the operation of the right heating port 3 will be described. When the pan is placed on the central heating port 2 of the top plate 1 and the heating power is set in the operation display unit 5, the control circuit 11 starts energizing the central drive circuit 20.

At this time, an interference sound having a frequency corresponding to the difference between the driving frequencies of the central heating port 2 and the right heating port 3 is generated.
FIG. 4 is a diagram showing the relationship between the frequency of the interference sound and the user's audibility. When the generated interference sound is 18 kHz or higher, the frequency is higher than the audible range of the user, so that the user hardly hears it. In addition, when the frequency corresponding to the difference between the driving frequencies is 0 to 3 kHz, the interference sound is audible to the user and can be heard a little, but since it is a frequency band equivalent to normal speech, it is not harsh. Become.
On the other hand, an interference sound in a frequency band of 4 kHz or more and less than 18 kHz is a general high sound (a keen sound), which gives an unpleasant feeling to the user and becomes annoying. Note that the audibility classification shown in FIG. 4 is a rough one and does not limit the numerical values.

  As described above, when the two heating ports are operated simultaneously, an irritating interference sound can be generated due to the difference in the driving frequency of each driving circuit. For this reason, the induction heating cooker 100 controls the frequency range of the interference sound to be 3 kHz or less, or 18 kHz or more.

  FIG. 6 is a diagram showing the relationship between the drive frequency and power of the central drive circuit 20. In FIG. 6, the inverter circuit 22 is a frequency control type inverter, and the input power decreases as the drive frequency is increased. Three types shown in A, B, and C according to the combined capacity of the resonant capacitor circuit 23. With a power curve. In FIG. 6, power curves A, B, and C show power curves when the resonant capacitor circuit 23 has the combined capacitors A, B, and C, respectively. Further, P1 (1500 W) and P2 (500 W) are illustrated as examples of the input power of the central drive circuit 20.

Here, as shown in FIG. 6, for example, the right drive circuit 30 is driven at a drive frequency of f _R (24 kHz). In this case, the range of the driving frequency of the central driving circuit 20 is set to a range f _lo where the frequency difference with the right driving circuit 30 is within 3 kHz, or a range f _hi where the frequency difference is 18 kHz or more. In the example of FIG. 6, the range f _lo is 21KHz～27kHz range f _hi becomes 42kHz~ upper limit value (e.g., 70 kHz). Hereinafter, the control operation of the drive frequency of the central drive circuit 20 will be specifically described.

FIG. 7 is a flowchart showing the control operation of the drive frequency of the central drive circuit 20. The control of the drive frequency of the central drive circuit 20 is performed by continuously executing the flow shown in FIG. 7, for example, every second. The control operation shown in FIG. 7 is performed when the right driving circuit 30 drives the central driving circuit 20 simultaneously while driving. Therefore, in the initial state of the flowchart of FIG. 7, it is assumed that the right drive circuit 30 is driven at the drive frequency f _R (for example, 24 kHz).

(S101)
The control circuit 11 reads the target power P _Cref of the central heating port 2 and the drive frequency f _R of the right drive circuit 30. The target power P _Cref of the central heating port 2 is read from the setting on the operation display unit 5.
(S102)
_{Subsequently,} it is determined whether or not there is a change in the target power P _Cref of the central heating port 2 and the drive frequency f _R of the right drive circuit 30 compared with the previous read value (for example, the value read one second ago). If there is a change, the process proceeds to step S103, and if there is no change, the process ends.

(S103)
The control circuit 11 turns on the relay 25 and the relay 27 so that the combined capacity of the resonant capacitor circuit 23 becomes the combined capacity A. Then, the drive frequency f _C of the central heating port 2 is swept from the lower limit (for example, 20 kHz) to the upper limit (for example, 70 kHz) in the range f _lo and the range f _hi .
(S104)
_Subsequently , it is determined whether or not there is a frequency at which the power P _C of the central heating port 2 becomes the target power P _Cref of the central heating port 2. If there is a frequency, the process proceeds to step S109, and if not, the process proceeds to step S105.
That is, in steps S103 and S104, in the power curve A of FIG. 6, it is determined whether or not the target power P _Cref can be obtained by gradually _{changing the} drive frequency f _C within the range f _lo and the range f _hi . is there.

(S105)
The control circuit 11 turns on the relay 25 and turns off the relay 27 so that the combined capacity of the resonant capacitor circuit 23 becomes the combined capacity B. Then, the drive frequency f _C of the central heating port 2 is swept from the lower limit (for example, 20 kHz) to the upper limit (for example, 70 kHz) in the range f _lo and the range f _hi .
(S106)
Subsequently, similarly to step S104, it is determined whether or not there is a frequency at which the power P _C of the central heating port 2 becomes the target power P _Cref of the central heating port 2, and if there is, the process proceeds to step S109. Proceed to step S107.

(S107)
The control circuit 11 turns off the relay 25 and turns on the relay 27 so that the combined capacity of the resonant capacitor circuit 23 becomes the combined capacity C. Then, the drive frequency f _C of the central heating port 2 is swept from the upper limit (for example, 20 kHz) to the lower limit (for example, 70 kHz) in the range f _lo and the range f _hi .
(S108)
Subsequently, similarly to step S104, the frequency at which the power P _C of the central heating port 2 becomes the target power P _Cref of the central heating port 2 is specified.

(S109)
The control circuit 11 drives the central drive circuit 20 at the drive frequency f _C specified in any one of steps S104, S106, and S108 so that the power P _C of the central heating port 2 becomes the target power P _Cref of the central heating port 2. Let

Thus, a series of flow shown in FIG. 7, the frequency of the difference between the drive frequency f _C of the drive frequency f _R and the center drive circuit 20 of the right drive circuit 30, a 3kHz or less or 18kHz or more.

The series of flows described in FIG. 7 will be further described with reference to FIG.
When the target power P _Cref central heating port 2 is P1 (1500 W), when the combined capacitance A, when the swept central driving frequency f _C until 21kHz~27kHz in a range f _lo, central heating when f _C is 22kHz The power P _{c of the} mouth 2 becomes P1 (1500 W) (steps S103 and S104 in FIG. 6). Therefore, the central heating port 2 is driven at the frequency f _C1 (22 kHz) (S109). Thereafter, the user operates the operation display unit 5 to change the set heating power until the target power P _Cref of the central heating port 2 is changed or the drive frequency f _R of the right heating port 3 is changed. _Are driven at the same drive frequency f _{C1 as} they are.

When the target power P _Cref of the central heating port 2 is P2 (500 W), when the combined capacity is A, the frequency at which the power P _c of the central heating port 2 becomes P2 (500 W) in the range f _lo and the range f _hi is Does not exist (S103, S104).
If combined capacitance B, and is swept by the scope of the driving frequency fc of the central heating inlet 2 f _lo (21kHz~27kHz), and a range f _hi (42kHz~70kHz), central heating when f _c is the 46kHz The power P _{c of the} mouth 2 becomes P2 (500 W) (S105, S106). Therefore, the central heating port 2 is driven at the frequency f _C2 (46 kHz) (S109).

When the target power P _Cref of the central heating port 2 is P2 (500 W), the frequency at which the power P _c is P2 (500 W) exists in the range f _{hi even} in the combined capacity C. It is also possible to drive. However, when the target power P _Cref is P2 (500 W), since the driving frequency is lower when the composite capacitor B is used than when the composite capacitor C is used, the composite capacitor B suppresses the switching loss of the inverter circuit 22. be able to. In the first embodiment, the drive frequency is swept in the order of the combined capacitors A, B, and C as shown in FIG. 7, so that a lower drive frequency can be obtained and switching loss can be reduced. .

  In the above description, the case where the central heating port 2 is driven while the right heating port 3 is driven has been described as an example, but the same processing is performed even when the central heating port 2 is driven while the left heating port 4 is driven. I do.

  Further, when only the central heating port 2 is driven, no interference sound is generated. Therefore, the resonance capacitor circuit 23 is driven in the state of the combined capacitance A so that the drive frequency is minimized. In this way, the switching loss of the inverter circuit 22 can be suppressed, the control operation of the control circuit 11 can be simplified, and the rise time can be shortened.

  As described above, according to induction heating cooker 100 according to the first embodiment, when driving central heating port 2 while other heating ports are driven, the capacitance of resonant capacitor circuit 23 is switched. At the same time, the frequency of the difference from the driving frequency of the other heating ports is driven at a frequency that does not become an annoying frequency band. For this reason, generation | occurrence | production of the annoying interference sound when driving two heating openings simultaneously can be suppressed.

  Further, in a region where the power is relatively high, the driving is suppressed so as to drive in a region where the driving frequency band is low. For example, in the induction heating cooker described in Patent Document 1, the drive frequency range is always 50 kHz or higher. However, according to the heating cooker according to the first embodiment, the induction cooking device is driven by switching the capacity of the resonant capacitor circuit 23. The frequency can be lowered. For this reason, an increase in switching loss of the inverter circuit 22 can be suppressed. Moreover, since the heat generation of the circuit can also be suppressed, it is possible to suppress an increase in the cooling means.

  In addition, a plurality of series connection circuits of a resonance capacitor and a relay are connected in parallel, and the capacitance of the resonance capacitor circuit 23 is switched by performing ON / OFF control of the relay. For this reason, when n resonance capacitors are provided, the capacitance of the resonance capacitor circuit 23 can be switched in (n! +1) ways. Therefore, it is possible to switch to a larger number of types of capacitors than the number of resonant capacitors provided in the resonant circuit.

  The capacity of the resonant capacitor circuit 23 of the central drive circuit 20 is controlled when the central heating port 2 is operated while the left heating port 4 or the right heating port 3 is being driven, and only the central heating port 2 is operated. When this is done, the capacitance control of the resonant capacitor circuit 23 is not performed. That is, when the right resonance circuit 34 is in a stopped state, the capacitance control of the resonance capacitor circuit 23 is not performed. For this reason, the control by the control circuit 11 can be easily performed, and the rise time can be shortened.

Embodiment 2. FIG.
In the second embodiment, an induction heating cooker having a circuit configuration in which a drive circuit for two heating ports shares one rectifier circuit will be described as an example.

  FIG. 8 is a circuit configuration diagram of the induction heating cooker 100A according to the second embodiment, showing a circuit of the central heating port 2 and the right heating port 3, and the first embodiment described with reference to FIG. The same or equivalent parts are denoted by the same reference numerals. In addition, although the circuit of the left heating port 4 is not shown in FIG. 8, it is assumed that the configuration is the same as that of the first embodiment.

(Rectifier circuit)
In FIG. 8, the difference from the above-described first embodiment is that the central drive circuit 20A and the right drive circuit 30A are connected to share the rectifier circuit 13A. The rectifier circuit 13A performs full-wave rectification on the AC power input from the commercial power supply 12 to convert it into DC power, and supplies the DC power to the central drive circuit 20A and the right drive circuit 30A connected in parallel to the rectifier circuit 13A. .

(Power module)
An inverter circuit 22 </ b> A that supplies high-frequency current to the central heating coil 21 and an inverter circuit 32 </ b> A that supplies high-frequency current to the right heating coil 31 are built in the power module 50. The power module 50 is a high-frequency power supply unit incorporating the inverter circuit 22A and the inverter circuit 32A. The power module 50 includes IGBTs 51, 52, 53, 54, 55, and 56, and a series connection circuit of two IGBTs constitutes an arm and is connected in parallel to the DC high potential line and the DC low potential line. It is configured. The IGBTs 51 to 54 constitute an inverter circuit 32A, and the inverter circuit 32A is a so-called full-bridge type inverter using two arms. The IGBTs 55 and 56 constitute an inverter circuit 22A, and the inverter circuit 22A is a so-called half-bridge type inverter using one arm and a DC low potential line. The first high frequency power supply unit of the present invention corresponds to the inverter circuit 22A, and the second high frequency power supply unit corresponds to the inverter circuit 32A.

  100 A of induction heating cookers comprised in this way perform the operation | movement similar to above-mentioned Embodiment 1. FIG. That is, when the heating power is set on the operation display unit 5, the pot type is first determined, and the central heating coil 21 or the right heating coil 31 is induction-heated based on the determination result and the heating power setting on the operation display unit 5. Further, when the central heating port 2 is operated while the right heating port 3 is operating, the capacity of the resonance capacitor circuit 23 is switched, and the frequency difference between the driving frequency of the other heating ports is not an annoying frequency band. Drive with frequency.

  As described above, according to induction heating cooker 100A according to the second embodiment, even in the configuration in which central drive circuit 20A and right drive circuit 30A share rectifier circuit 13A, the same as in the first embodiment described above. An effect can be obtained. That is, it is possible to suppress the generation of annoying interference sound and to suppress an increase in switching loss of the inverter circuit 22.

  Further, the central drive circuit 20A and the right drive circuit 30A share the rectifier circuit 13A. Moreover, the power module 50 which modularized the inverter circuit 22A and the inverter circuit 32A into one was provided. For this reason, the circuit scale of the induction heating cooker 100A can be reduced.

In addition, in the case of a configuration in which a plurality of drive circuits share a DC bus line and a ground line and share the rectifier circuit 13A as in the induction heating cooker 100A according to the second embodiment, each heating coil has an independent frequency. Because it is controlled, interference also occurs electrically. That is, the driving frequency component of each heating port and the frequency component of the difference between them are superimposed on the DC bus. For this reason, the frequency component of the difference directly vibrates the pan through the heating coil, thereby generating an interference sound.
However, according to the induction heating cooker 100A according to the second embodiment, by switching the capacity of the resonant capacitor circuit 23, the difference frequency from the driving frequency of the other heating ports is a frequency that does not become an annoying frequency band. Since it is driven, the interference sound due to electrical interference can be outside the user's audible range.

  In the second embodiment, the case where the central heating port 2 and the right heating port 3 share the rectifier circuit 13A has been described as an example. However, the central heating port 2 and the left heating port 4 share the rectifier circuit. The same effect can be obtained.

Embodiment 3 FIG.
In the above-described first and second embodiments, the case where the inverter circuit 32 that performs energization control of the right heating coil 31 of the right heating port 3 is of the frequency control type has been described as an example. In the third embodiment, an inverter circuit that controls energization of the right heating coil 31 of the right heating port 3 by duty control will be described as an example. In addition, although the induction heating cooking appliance in this Embodiment 3 is applicable to any of the circuit structure demonstrated in FIG. 2, FIG. 8, it demonstrates taking the structure of FIG. 2 as an example.

The inverter circuit 32 of the right drive circuit 30 is assumed to be a duty control type inverter that performs power control only by changing the on-duty ratio of the inverter circuit with the drive frequency fixed. For example, when a magnetic pan (iron or SUS430 pan) is placed, the drive frequency f _Rm of the right heating port 3 is fixed at 23 kHz, while a high-resistance nonmagnetic pan (SUS304 pan) is placed. fixing the driving frequency f _Rn when it is location to 29 kHz, power control only change the duty in this state. Other configurations and operations of the right drive circuit 30 are the same as those in the first embodiment.

Next, the operation when the central heating port 2 is driven while the right heating port 3 configured as described above is being driven will be described.
FIG. 9 is a diagram showing the relationship between the driving frequency of the right heating port 3 and the driving frequency of the central heating port 2. 9A shows a case where a magnetic pan is placed on the right heating port 3, and FIG. 9B shows a case where a non-magnetic pan is placed on the right heating port 3.

In FIG. 9A, the drive frequency f _Rm of the right drive circuit 30 when the magnetic pan is placed is fixedly controlled at 23 kHz. Therefore, the drive frequency range of the central drive circuit 20 is set to a range f _lo where the frequency difference from the right heating port 3 is within 3 kHz, or a range f _hi where the frequency difference is 18 kHz or more. In this case, the range f _lo is 20KHz～26kHz range f _hi becomes 41kHz~ upper limit value (e.g., 70 kHz).

Similarly, in FIG. 9B, the drive frequency f _Rn of the right drive circuit 30 when the non-magnetic pan is placed is fixedly controlled at 29 kHz. Therefore, the drive frequency range of the central drive circuit 20 is set to a range f _lo where the frequency difference from the right heating port 3 is within 3 kHz, or a range f _hi where the frequency difference is 18 kHz or more. In this case, the range f _lo is 26KHz～32kHz range f _hi becomes 47kHz~ upper limit value (e.g., 70 kHz).

The drive frequency of the right heating port 3 is fixedly controlled as long as the placed pan is not changed. For this reason, the frequency range f _lo and the range f _{hi of} the central heating port 2 are also fixed depending on whether the pan placed on the right heating port 3 is a magnetic pan or a non-magnetic pan.

FIG. 10 is a diagram showing the relationship between the target power of the central heating port 2 and the combined capacity of the resonant capacitor circuit 23. As described above, the frequency range f _lo and the range f _hi of the central heating port 2 are fixed by the pan type of the right heating port 3, so that the target power P _Cref of the central heating port 2, the combined capacity of the resonant capacitor circuit 23, And the range of drive frequency can be tabulated based on FIG.

In FIG. 10, when the placing pan of the right heating port 3 is a magnetic pan, if the target power P _Cref of the central heating port 2 is 0 W or more and less than 900 W, the combined capacity is C, and the target power P _Cref is 900 W or more. In this case, the combined capacity is A. Further, when the placing pan of the right heating port 3 is a non-magnetic pan, if the target power P _Cref of the central heating port 2 is 0 W or more and less than 400 W, the combined capacity C is set, and the target power P _Cref is 400 W or more and less than 800 W. If so, the combined capacity A is set, and if the target power P _Cref is 800 W or more, the combined capacity B is set.

FIG. 11 is a flowchart showing the control operation of the drive frequency of the central drive circuit 20. The control of the drive frequency of the central drive circuit 20 is performed by continuously executing the flow shown in FIG. 11 every second, for example. The control operation shown in FIG. 11 is performed when the right drive circuit 30 drives the central drive circuit 20 simultaneously while the right drive circuit 30 is driving. Therefore, in the initial state of the flowchart of FIG. 11, it is assumed that the right drive circuit 30 is driven at the drive frequency f _R.

(S111)
The control circuit 11 reads the material of the pan placed on the right heating port 3 and the target power P _Cref of the central heating port 2. The target power P _Cref of the central heating port 2 is read from the setting on the operation display unit 5.
(S112)
_Subsequently , whether or not there is a change in the material of the pan placed on the right heating port 3 and the target power P _Cref of the central heating port 2 compared to the previous reading value (for example, the value read one second ago) If there is a change, the process proceeds to step S113. If there is no change, the process ends.

(S113)
The control circuit 11 determines the combined capacity of the resonance capacitor circuit 23 of the central heating port 2 according to the table shown in FIG. 10 according to the material of the pan placed on the right heating port 3 and the target power P _Cref of the central heating port 2. The range of the driving frequency f _C is selected.

(S114)
Subsequently, after setting the ON / OFF state of the relay 25 and the relay 27 so that the combined capacity of the resonant capacitor circuit 23 becomes the combined capacity selected in step S113, the drive frequency f _C is set to the drive frequency selected in step S113. Sweep from the upper limit to the lower limit within the range of. Then, the driving frequency f _{C at} which the power P _C of the central heating port 2 becomes the target power P _Cref of the central heating port 2 is specified, and the central driving circuit 20 is driven at the driving frequency f _C.
If the target power P _Cref of the central heating port 2 and the material of the pan placed on the right heating port 3 are specified, the driving frequency f _C of the central driving circuit 20 is also specified by the table of FIG. A frequency sweep is performed to fine-tune the power.

Such a series of processes is performed at a predetermined cycle (for example, 1 second), and the same drive frequency f _C is used until the target power P _Cref of the pan placed on the right heating port 3 or the central heating port 2 is changed. Drive with.

  As mentioned above, according to the induction heating cooking appliance which concerns on this Embodiment 3, the effect similar to above-mentioned Embodiment 1 can be acquired. That is, it is possible to suppress the generation of annoying interference sound and to suppress an increase in switching loss of the inverter circuit 22.

  Further, since the frequency of the central drive circuit 20 is performed based on predetermined information (table) according to the type of pan placed on the right drive circuit 30 to be duty controlled, the central drive of the central heating port 2 is driven. The drive processing speed of the circuit 20 can be improved. For this reason, the rise time of the central drive circuit 20 can be shortened.

  In the above description, the case where the first drive circuit of the present invention is the central drive circuit 20 of the central heating port 2 has been described as an example. However, for example, in the case of three induction heating cookers, the left heating port, The drive circuit for the right heating port can be the first drive circuit of the present invention. However, in the case of a three-piece induction heating cooker arranged as shown in FIG. 1, the left heating port and the right heating port are physically separated from each other. On the other hand, since the central heating port is close to the other heating ports, interference noise tends to be a problem. Accordingly, in the case of a three-mouth induction heating cooker arranged as shown in FIG. 1, the first drive circuit of the present invention is used as the central heating port drive circuit, so that both the left heating port and the right heating port can be used. Can respond.

Embodiment 4 FIG.
In the fourth embodiment, an induction heating cooker that constitutes one heating coil by arranging two circular coils having different diameters in a concentric manner with the same center point will be described as an example.

  FIG. 12 is a top view of the induction heating cooker according to the fourth embodiment, and a heating coil 61 is disposed in the right heating port 3. FIG. 13 is a configuration diagram of the heating coil 61 of the right heating port 3 of the induction heating cooker according to the fourth embodiment. The heating coil 61 is formed by concentrically arranging two circular coils having different diameters. One heating coil is configured. Of the two circular coils, the smaller one is the main coil 65 and the larger one is the auxiliary coil 66, which are connected to different inverter circuits and driven independently. In the fourth embodiment, the first heating coil of the present invention corresponds to the auxiliary coil 66, and the second heating coil of the present invention corresponds to the main coil 65.

FIG. 14 is a circuit configuration diagram of the right heating port 3 of the induction heating cooker according to the fourth embodiment, which is characterized by the right drive circuit 30B. In addition, in FIG. 14, the circuit of the left heating port 4 and the center heating port 2 is not described. Also, the same reference numerals are given to the same or corresponding parts as those in the first and second embodiments described in FIG. 2 and FIG.
14 differs from the second embodiment in that the main coil 65 and the auxiliary coil 66 are independently controlled by the inverter circuit 32A and the inverter circuit 32B, respectively. The inverter circuit 32B has the same configuration as the inverter circuit 22A of FIG. A resonance capacitor circuit 23B is connected to the auxiliary coil 66. The resonant capacitor circuit 23B has the same configuration as the resonant capacitor circuit 23 of FIG.

  FIG. 15 is a schematic cross-sectional view of the vicinity of the heating coil 61 when the induction heating cooker showing the fourth embodiment is placed on the small-diameter pan. In FIG. 15, a main coil 65 and an auxiliary coil 66 are supported by a coil base 67 below the top plate 1. A pan (hereinafter referred to as a small-diameter pan) 69 having a diameter similar to that of the main coil 65 is placed on the top surface of the top plate 1.

  FIG. 16 is a schematic cross-sectional view of the vicinity of the heating coil 61 when the large-diameter pan is placed in the induction cooking device showing the fourth embodiment. In FIG. 16, a pan 68 (hereinafter referred to as a large-diameter pan) having a diameter similar to that of the auxiliary coil 66 is placed on the top surface of the top plate 1.

  When the user places the small-diameter pan 69 on the right heating port 3 on the top plate 1, the inverter circuit 32 </ b> A and the inverter circuit 32 </ b> B are driven with a load determination signal as in the second embodiment, and the main coil 65 And the type of the pan placed on the auxiliary coil 66 is determined. When the small-diameter pan 69 shown in FIG. 15 is placed, the control circuit 11 detects a state where a heatable pan is placed on the main coil 65 (magnetic pan and non-magnetic pan in FIG. 5). On the other hand, it is detected that the heatable pan is not placed on the auxiliary coil 66 (no load in FIG. 5). Thus, it can be determined that the small-diameter pan 69 is placed by detecting that the pan is placed only on the main coil 65 located on the center side. When detecting the small-diameter pan 69, the control circuit 11 drives only the main coil 65 to perform cooking.

  When the large-diameter pan 68 is placed on the right heating port 3 on the top plate 1 by the user, the inverter circuit 32A and the inverter circuit 32B are driven by a load discrimination signal as in the second embodiment, and the main coil 65 and the type of pan placed on the auxiliary coil 66 are determined. When the large-diameter pan 69 shown in FIG. 16 is placed, the control circuit 11 is in a state where a heatable pan is placed on the main coil 65 (a magnetic pan or a non-magnetic pan in FIG. 5). , And it is detected that a heatable pan is also placed on the auxiliary coil 66 (a magnetic pan or a non-magnetic pan in FIG. 5). By detecting that a pan is placed on both the main coil 65 and the auxiliary coil 66, it can be determined that the large-diameter pan 68 is placed. When the control circuit 11 detects the large-diameter pan 68, the main coil 65 and the auxiliary coil 66 are driven to perform cooking.

  When the small-diameter pan 69 is placed, only the main coil 65 is driven, so that no interference sound of a difference in driving frequency is generated between the main coil 65 and the auxiliary coil 66. However, when the large-diameter pan 68 is placed, cooking using both the main coil 65 and the auxiliary coil 66 can be performed, so that a difference in driving frequency between the coils is generated as an interference sound by the right heating port 3 alone. To do. Hereinafter, the operation of the induction heating cooker showing the fourth embodiment will be described for the case where the large-diameter pan 68 is placed.

The large-diameter pan 68 is placed by the user, and cooking is started by operating the operation display unit 5. When the large-diameter pan 68 is detected by discriminating the pan type of the control circuit 11, the main coil 65 and the auxiliary coil 66 are driven. The main coil 65 heats the center of the pan bottom of the mounting pan, and the auxiliary coil 66 heats the pan bottom helicopter of the mounting pan and the side of the pan. The user operates the operation display unit 5 to arbitrarily set the heating power of the main coil 65 and the auxiliary coil 66 according to the cooking contents.
The control circuit 11 controls the drive frequency of the inverter circuit 32A and the inverter circuit 32B according to the thermal power set by the user. In the above-described second embodiment, an example in which different heating ports are operated simultaneously has been described. However, the present embodiment also includes a case where the heating coil 61 configured by two coils as in the fourth embodiment is driven. Power control similar to 2 is performed. That is, the control circuit 11 switches the capacitance of the resonance capacitor circuit 23B so that the difference frequency between the drive frequencies of the main coil 65 and the auxiliary coil 66 does not become an annoying frequency band.

  As described above, according to the induction heating cooker according to the fourth embodiment, the drive circuit 32A of the main coil 65 and the drive circuit 32B of the auxiliary coil 66 constituting one heating coil are connected to the rectifier circuit 13A with the same heating port. Even in the configuration sharing the same, the same effect as in the second embodiment can be obtained. That is, it is possible to suppress generation of annoying interference sound and to suppress an increase in switching loss of the inverter circuit 32A.

  The main coil drive circuit 32A and the auxiliary coil drive circuit 32B share the rectifier circuit 13A. Moreover, the power module 50 which modularized the inverter circuit 32B and the inverter circuit 32A was provided. For this reason, the circuit scale of an induction heating cooking appliance can be reduced in size.

In the case of a configuration in which a plurality of inverter circuits 32A and 32B share the DC bus and the ground line and share the rectifier circuit 13A as in the induction heating cooker according to the second embodiment, the main coil 65 and the auxiliary coil 66 are used. Since each is frequency-controlled independently, interference also occurs electrically. That is, the driving frequency component of the main coil 65 and the auxiliary coil 66 and the frequency component of the difference between them are superimposed on the DC bus. For this reason, the frequency component of the difference directly vibrates the pan through the main coil 65 and the auxiliary coil 66, thereby generating an interference sound.
However, according to the induction heating cooker according to the fourth embodiment, the frequency of the difference between the drive frequencies of the main coil 65 and the auxiliary coil 66 does not become an annoying frequency band by switching the capacity of the resonant capacitor circuit 23B. Therefore, the interference sound caused by electrical interference can be outside the user's audible range.

Moreover, according to the induction heating cooking appliance which concerns on this Embodiment 4, since the diameter of the auxiliary coil 66 is set larger than the diameter of the main coil 65, each site | part of a mounting pan is heated with arbitrary thermal power. be able to. Furthermore, since the resonance capacitor circuit 23B is provided on the auxiliary coil 66 side, it is not necessary to perform the switching operation of the resonance capacitor circuit 23B when the small-diameter pan 69 is placed, so that the control flow can be simplified.
When a pan having a diameter smaller than the diameter of the auxiliary coil 66 is placed and it is detected that the auxiliary coil 66 is in an unloaded state, the auxiliary coil 66 is not energized. Efficient heating can be performed.

In the fourth embodiment, the inverter circuits 32A and 32B are energized and controlled by frequency control. However, similar to the third embodiment, the configuration may be such that the energization control is performed by duty control and the same effect is obtained. Obtainable.
In addition, although the example about the right heating port 3 was shown in this Embodiment 4, the left heating port 4 or the center heating port 2 may be made into the same structure, and the same effect can be acquired.

  DESCRIPTION OF SYMBOLS 1 Top plate, 2 Central heating port, 3 Right heating port, 4 Left heating port, 5 Operation display part, 11 Control circuit, 12 Commercial power supply, 13, 13A Rectification circuit, 14 Rectification circuit, 20, 20A Central drive circuit, 21 Central heating coil, 22, 22A Inverter circuit, 23, 23B Resonance capacitor circuit, 24, 24B Resonance capacitor, 25, 25B Relay, 26, 26B Resonance capacitor, 27, 27B Relay, 28 Central resonance circuit, 30, 30A, 30B Right Drive circuit, 31 right heating coil, 32, 32A, 32B inverter circuit, 33 resonance capacitor, 34 right resonance circuit, 41 left heating coil, 50 power module, 61 heating coil, 65 main coil, 66 auxiliary coil, 67 coil base, 68 Large-diameter pan, 69 Small-diameter pan, 100 Induction cooking , 100A induction heating cooker, 131 diode bridge, 132 choke coil, 133 a smoothing capacitor, 141 a diode bridge, 142 choke coil, 143 a smoothing capacitor.

Claims (10)

A first resonant circuit comprising a first heating coil and a resonant capacitor connected in series to the first heating coil;
A second resonant circuit comprising a second heating coil and a resonant capacitor connected in series to the second heating coil;
Capacitance switching means for switching the capacitance of the first resonance circuit according to the drive frequency of the second resonance circuit;
A first high-frequency power supply unit that converts a direct current into a high-frequency current and supplies the converted high-frequency current to the first resonance circuit;
A second high-frequency power supply unit that converts a direct current into a high-frequency current and supplies the converted high-frequency current to the second resonance circuit;
The drive frequency of the first resonance circuit is controlled so that the difference between the drive frequency of the first resonance circuit and the drive frequency of the second resonance circuit becomes a value in a predetermined low frequency region or high frequency region. And an induction heating cooker characterized by comprising: A rectifier circuit for supplying a direct current to the first high frequency power supply unit and the second high frequency power supply unit;
The induction heating cooker according to claim 1, wherein the first high-frequency power supply unit and the second high-frequency power supply unit share the rectifier circuit and are connected in parallel to the rectifier circuit. The induction heating cooker according to claim 1 or 2, wherein the first high-frequency power supply unit and the second high-frequency power supply unit are modularized into one. The first resonant circuit has a configuration in which a plurality of resonant capacitors connected in parallel are connected in series to the first heating coil,
The capacity switching means is
Switching means each connected in series to the plurality of resonant capacitors;
It has a capacity | capacitance switching control part which controls the ON / OFF state of the said switching means. The induction heating cooking appliance in any one of Claims 1-3 characterized by the above-mentioned. A load pan determining means for determining the material of the load pan placed on the top plate arranged on the upper surface side of the second heating coil;
The second resonance circuit is duty-controlled at a predetermined drive frequency according to the material of the load pan,
The said capacity switching means switches the capacity | capacitance of a said 1st resonance circuit according to the drive frequency of the said 2nd resonance circuit specified based on the determination result of the said load pan determination means. Item 5. The induction heating cooker according to any one of Items 4 to 6. A first resonant circuit comprising a first heating coil and a resonant capacitor connected in series to the first heating coil;
A second resonance circuit including a second heating coil and a resonance capacitor connected in series to the second heating coil, and duty-controlled at a predetermined drive frequency;
A first high-frequency power supply unit that converts a direct current into a high-frequency current and supplies the converted high-frequency current to the first resonance circuit;
A second high-frequency power supply unit that converts a direct current into a high-frequency current and supplies the converted high-frequency current to the second resonance circuit;
Depending on the target power of the first resonance circuit, the difference between the drive frequency of the first resonance circuit and the drive frequency of the second resonance circuit becomes a value in either a predetermined low frequency region or high frequency region. An induction cooking device comprising: capacity switching means for switching the capacity of the first resonance circuit so that the first resonance circuit can be driven at such a drive frequency. When the second resonance circuit is in a stopped state,
The induction heating cooker according to any one of claims 1 to 6, wherein the capacity switching means does not perform capacity switching of the first resonance circuit. The induction heating cooker according to any one of claims 1 to 7, wherein the first heating coil and the second heating coil are arranged substantially concentrically. The induction heating cooker according to claim 8, wherein a diameter of the first heating coil is larger than a diameter of the second heating coil. When the load pan determining means detects that the load pan is not placed on the top plate arranged on the upper surface side of the second coil, only the first resonance circuit is driven. The induction heating cooker according to claim 8 or 9, which is dependent on claim 5.

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