JP7149722B2 - induction cooker - Google Patents

Description

The present invention relates to an induction heating cooker with multiple heating coils.

Conventionally, there has been proposed a heating cooker provided with a plurality of heating coils for induction heating of a cooking container. For example, in Patent Document 1, a work coil drive control circuit unit (inverter circuit) is provided for each of the first work coil and the second work coil, and the first work coil and the second work coil are individually controlled. It is disclosed to energize the Further, for example, in Patent Document 2, a first heating coil and a second heating coil are connected to one inverter circuit via a switching relay having a mechanical contact, and depending on the state of the switching relay, the first heating coil It is disclosed to connect either the first heating coil or the second heating coil to an inverter circuit.

JP 2004-236859 A (page 7) JP 2015-5491 A (pages 8 and 9)

By exclusively and alternately energizing the first heating coil and the second heating coil that are individually energized, convection in the cooking vessel is promoted, thereby improving uneven heating. Also, depending on the amount of heating required, the first heating coil and the second heating coil may be energized simultaneously.

Here, when the first heating coil and the second heating coil are energized at the same time, if the frequency of the high frequency current flowing in the first heating coil is different from the frequency of the high frequency current flowing in the second heating coil , an interference sound is generated according to the frequency difference. As a method for suppressing such interference sound, it is conceivable to make the frequency of the high frequency current flowing through the first heating coil equal to the frequency of the high frequency current flowing through the second heating coil. However, in the case of the single-switch voltage resonance inverter described in Patent Document 1, for example, there are manufacturing variations in the inductance of the first heating coil and the second heating coil and the capacitance of the resonance capacitor. Therefore, it has been difficult to make the drive frequencies of the two inverter circuits the same.

Moreover, as described in Patent Document 2, by alternately energizing the first heating coil and the second heating coil, the above-described problem of interference noise due to the frequency difference does not occur. However, a switching relay that selectively connects a first heating coil and a second heating coil to an inverter circuit, for example, described in Patent Document 2, generates sound from the mechanical contacts when the mechanical contacts are switched. In particular, when the mechanical contacts of the switching relay are frequently switched in order to promote convection in the cooking vessel, the noise generated by the mechanical contacts gives discomfort to the user. In addition, frequent switching of the mechanical contacts of the switching relay shortens the life of the mechanical contacts, and the shortened life of the mechanical contacts can impair the durability of the heating cooker.

The present invention has been made against the background of the above problems, and is an induction heating cooker equipped with a plurality of heating coils that can be energized simultaneously and exclusively. It makes it difficult.

An induction heating cooker according to the present invention includes a first heating coil for heating an object to be heated, a second heating coil for heating the object to be heated, a first inverter, a second inverter, and the first inverter. A first state in which high-frequency current supply to the first heating coil and high-frequency current supply from the second inverter to the second heating coil are executed separately; switch means for electrically switching between a second state in which high-frequency current is supplied to the first heating coil and the second heating coil by operating the inverter as one inverter , wherein the first inverter is , a single-switch voltage resonance inverter having a first switching element, the second inverter being a single-switch voltage resonance inverter having a second switching element, one end of the first heating coil and one end of the second heating coil. is electrically connected, the other end of the first heating coil is connected to the first switching element, the other end of the second heating coil is connected to the second switching element, and the switch means is provided at a position for electrically connecting a connection point between the first heating coil and the first switching element and a connection point between the second heating coil and the second switching element. be.

According to the present invention, the first heating coil and the second heating coil can be exclusively energized in the first state. When switching the energization of the first heating coil and the second heating coil in the first state, the mechanical contact as shown in Cited Document 2 is not used. No loss of durability. Further, in the second state, the first inverter and the second inverter are operated as one inverter, so that the first heating coil and the second heating coil can be energized at the same time without generating an interference sound.

1 is a schematic configuration diagram of an induction heating cooker according to Embodiment 1. FIG. 1 is a circuit block diagram of induction heating cooker 1 according to Embodiment 1. FIG. FIG. 4 is a diagram showing a simplified energization waveform when simultaneously energizing the first heating coil 21 and the second heating coil 22 according to Embodiment 1; FIG. 4 is a diagram showing a simplified energization waveform when energizing the first heating coil 21 and the second heating coil 22 exclusively and alternately according to Embodiment 1; 2 is a circuit block diagram of induction heating cooker 1 according to Embodiment 2. FIG. FIG. 10 is a diagram showing a simplified energization waveform when simultaneously energizing the first heating coil 21 and the second heating coil 22 according to Embodiment 2; FIG. 10 is a diagram showing a simplified energization waveform when energizing the first heating coil 21 and the second heating coil 22 exclusively and alternately according to Embodiment 2; FIG. 10 is a diagram showing a simplified modification of an energization waveform when alternately energizing the first heating coil 21 and the second heating coil 22 according to Embodiment 2;

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which an induction heating cooker according to the present invention is applied to a heating cooker capable of cooking rice will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention. In addition, the present invention includes all possible combinations of the configurations shown in the following embodiments. In addition, the induction heating cooker shown in the drawings is an example of equipment to which the induction heating cooker of the present invention is applied, and the applicable equipment of the present invention is limited by the induction heating cooker shown in the drawings. not a thing Also, in the following description, terms representing directions (for example, "up", "down", "right", "left", "front", "back", etc.) are used as appropriate for ease of understanding. They are for illustrative purposes and are not intended to limit the invention. Also, in each figure, the same reference numerals denote the same or corresponding parts, which are common throughout the specification. In each drawing, the relative dimensional relationship, shape, etc. of each component may differ from the actual one.

Embodiment 1.
(Configuration of induction heating cooker)
FIG. 1 is a schematic configuration diagram of an induction heating cooker according to Embodiment 1. FIG. The induction heating cooker 1 includes a housing 2, an inner pot 3, an inner pot housing portion 4, a first heating coil 21, a second heating coil 22, an inverter circuit board 6, a control portion 7, a lid 8, and a lid open/close button 9. have. An inner pot 3 containing food is placed in an inner pot storage part 4 formed in a housing 2, and the food is cooked with the lid 8 closed.

The housing 2 has, for example, a rectangular parallelepiped outer shape. The inner pot 3 has a bottomed tubular shape with an open top, and is detachably stored in the inner pot storage portion 4 of the housing 2 . The inner pot 3 is an object to be heated, and is made of a base material such as aluminum having high thermal conductivity. A ferromagnetic material such as stainless steel is provided on the outer surface of the inner pot 3 by joining or the like. The inner pot housing portion 4 is formed inside the housing 2 and has a surface shaped roughly along the outer shape of the inner pot 3 .

Each of the first heating coil 21 and the second heating coil 22 is configured by winding a conductive wire. The first heating coil 21 and the second heating coil 22 are, for example, circular in plan view. In order to induction-heat the inner pot 3 stored in the inner pot storage portion 4, a first heating coil 21 is provided at a position facing the inner peripheral portion of the bottom of the inner pot 3, and the outer periphery of the bottom of the inner pot 3 A second heating coil 22 is provided at a position facing the part. The first heating coil 21 and the second heating coil 22 are arranged concentrically with respect to the center of the inner pot 3 .

The inverter circuit board 6 converts the voltage supplied from the commercial power source into a high frequency current and supplies the high frequency current to the first heating coil 21 and the second heating coil 22 .

The controller 7 is provided on the lid 8, for example. The control unit 7 controls the inverter circuit board 6 according to the instructed control contents. The control unit 7 includes, for example, a microcomputer 7a (see FIG. 2), a readable/writable memory (RAM), a read-only memory (ROM), and a timer (timekeeping means). The control unit 7 performs calculations according to the input signal and the stored program, controls the inverter circuit board 6 , and adjusts the outputs of the first heating coil 21 and the second heating coil 22 . Components such as a microcomputer of the control unit 7 are provided inside the lid 8, for example. Further, the control unit 7 of the present embodiment includes an operation unit for receiving cooking instructions from the user or changes in cooking contents and a display unit for displaying the state of the induction heating cooker 1 on the upper surface of the lid 8. there is

The lid 8 is attached to the upper portion of the housing 2, and is configured so that the upper portion of the housing 2 can be opened and closed via a hinge portion. The lid 8 is opened when the inner pot 3 is attached and detached and when food is put into the inner pot 3, and the lid 8 is closed when cooking. In this embodiment, as a preferred mode, a lid open/close button 9 for opening and closing the lid 8 is provided.

Each of the first heating coil 21 and the second heating coil 22 and the inverter circuit board 6 are connected by cables. Also, the inverter circuit board 6 and the control unit 7 are connected by a cable. A temperature sensor that directly or indirectly measures the temperature of the inner pot 3 may be provided, and the controller 7 may control the inverter circuit board 6 according to the temperature of the inner pot 3 detected by this temperature sensor. . Such a temperature sensor can be arranged in the inner pot housing 4, for example.

(circuit configuration)
FIG. 2 is a circuit block diagram of the induction heating cooker 1 according to Embodiment 1. As shown in FIG. The inverter circuit board 6 includes a rectifier circuit 11 that converts AC voltage to DC voltage, a filter circuit 12 that removes pulsating components due to switching, a first inverter 31 , and a second inverter 32 . The inverter circuit board 6 further includes a relay circuit 19 .

The first inverter 31 has a first switching element 13 , a first freewheeling diode 14 and a first resonant capacitor 15 . The first resonance capacitor 15 is connected between one end 21a and the other end 21b of the first heating coil 21 and forms a resonance circuit together with the first heating coil 21 . One end 21 a of the first heating coil 21 is connected to the high potential side output line of the rectifier circuit 11 , and the other end 21 b of the first heating coil 21 is connected to one end of the first switching element 13 . The other end of the first switching element 13 is connected to the output line on the low potential side of the rectifier circuit 11 . The first freewheeling diode 14 is connected in parallel with the first switching element 13 .

The second inverter 32 has a second switching element 16 , a second freewheeling diode 17 and a second resonance capacitor 18 . The second resonance capacitor 18 is connected between one end 22a and the other end 22b of the second heating coil 22 and forms a resonance circuit together with the second heating coil 22 . One end 22 a of the second heating coil 22 is connected to the high potential side output line of the rectifier circuit 11 , and the other end 22 b of the second heating coil 22 is connected to one end of the second switching element 16 . The other end of the second switching element 16 is connected to the output line on the low potential side of the rectifier circuit 11 . The second freewheeling diode 17 is connected in parallel with the second switching element 16 .

One end 21a of the first heating coil 21 and one end 22a of the second heating coil 22 are electrically connected.

The relay circuit 19 has a first connection point 25, which is a connection point between the first heating coil 21 and the first switching element 13, and a second connection point, which is a connection point between the second heating coil 22 and the second switching element 16. 26. For convenience of illustration, in FIG. 2, the other end 21b of the first heating coil 21 and the first connection point 25 indicate the same location. When the relay circuit 19 is turned on, the first connection point 25 and the second connection point 26 are electrically connected. That is, when the relay circuit 19 is turned on, the other end 21b of the first heating coil 21 and the other end 22b of the second heating coil 22 are electrically connected. When the relay circuit 19 is turned on, the first switching element 13 and the second switching element 16 connected in parallel are connected to the first heating coil 21 and the second heating coil 22 .

The gate terminals of the first switching element 13 and the second switching element 16 and the control terminal of the relay circuit 19 are each connected to the control section 7 and the operation thereof is controlled by the control section 7 .

The control unit 7 includes a microcomputer 7 a , a first drive circuit 7 b that drives the first switching element 13 , and a second drive circuit 7 c that drives the second switching element 16 . The microcomputer 7a outputs drive signals for driving the first switching element 13 and the second switching element 16, such as PWM (Pulse Width Modulation) signals. The microcomputer 7a functions as a drive signal generator that generates and outputs drive signals. A drive signal output from the microcomputer 7a is input to the first drive circuit 7b and the second drive circuit 7c. Each of the first drive circuit 7b and the second drive circuit 7c amplifies the drive signal input from the microcomputer 7a to a voltage suitable for driving the first switching element 13 and the second switching element 16, respectively.

(Overview of heating cooker operation)
Next, the outline of the operation of the induction heating cooker 1 will be described by taking the case of cooking rice as an example. When cooking rice, the user puts the inner pot 3 filled with rice and water into the inner pot housing portion 4 of the induction heating cooker 1 and closes the lid 8 . Next, the user inputs an instruction to start heating to the control section 7 having a display section and an operation section. When an instruction to start heating is input, the control unit 7 starts controlling the inverter circuit board 6 according to the programmed control sequence of the rice cooking process. The inverter circuit board 6 receives a signal from the control unit 7 and starts operating to supply high-frequency current to either or both of the first heating coil 21 and the second heating coil 22 . When a high-frequency current flows through the first heating coil 21 or the second heating coil 22, an alternating magnetic field is generated from the first heating coil 21 or the second heating coil 22, and the alternating magnetic field heats the inner pot 3, which is the object to be heated. A magnetic flux is given. Then, an eddy current is generated in the inner pot 3, Joule heat is generated by the eddy current and the electric resistance of the inner pot 3, and the inner pot 3 generates heat. The first inverter 31 and the second inverter 32 of the inverter circuit board 6 shown in this embodiment are single-switch voltage resonance inverters. The circuit configuration of the single-switch voltage resonance inverter is known, and detailed description of the circuit operation is omitted here.

Next, along the rice cooking process, the operation when the first heating coil 21 and the second heating coil 22 are simultaneously energized, and the first heating coil 21 and the second heating coil 22 are alternately energized exclusively. A specific description will be given of the operation in this case.

(Operation during simultaneous energization)
FIG. 3 is a diagram schematically showing an energization waveform when simultaneously energizing the first heating coil 21 and the second heating coil 22 according to the first embodiment. In FIG. 3 , the state in which the high-frequency alternating current is flowing in the first heating coil 21 and the second heating coil 22 is indicated by HIGH, and the state in which the high-frequency alternating current is not flowing is indicated by LOW.

Simultaneous energization is performed in the preheating process in the rice cooking process. The preheating step is a step before the water in the inner pot 3 boils, which promotes the water absorption of the rice and produces sugar as a sweet component and amino acids as a umami component. In the preheating step, the control unit 7 repeats energization and interruption of the first heating coil 21 and the second heating coil 22, or controls the energized current so that the temperature of the inner pot 3 reaches a predetermined temperature, thereby adjusting the temperature. . The predetermined temperature in the preheating step is a temperature (for example, less than about 60° C.) at which the temperature of the water in the inner pot 3 can be maintained at a temperature at which gelatinization of the rice does not start.

In the preheating process, the inner pot 3 is heated at a temperature lower than the boiling temperature, so no large convection occurs in the inner pot 3 . Therefore, the first heating coil 21 and the second heating coil 22 are energized at the same timing to heat the entire bottom surface of the inner pot 3 as uniformly as possible so that the water in the inner pot 3 does not have uneven temperature. . As shown in FIG. 3, the first heating coil 21 and the second heating coil 22 are simultaneously and intermittently energized at times t1 to t2, t3 to t4, and t5 to t6. When simultaneously energizing the first heating coil 21 and the second heating coil 22, the controller 7 outputs an ON signal to the relay circuit 19 (see FIG. 2) so that the relay circuit 19 is turned ON.

As shown in FIG. 2, when the relay circuit 19 is turned on, the first heating coil 21 and the second heating coil 22 are connected in parallel, and the first resonance capacitor 15 and the second resonance capacitor 18 are also connected in parallel. Therefore, a parallel combined inductance of the first heating coil 21 and the second heating coil 22 is formed, and a parallel combined capacitance of the first resonance capacitor 15 and the second resonance capacitor 18 is formed. Also, by turning on the relay circuit 19, the first switching element 13 and the second switching element 16 are also connected in parallel. Therefore, the two first inverters 31 and the second inverters 32 can simultaneously energize the first heating coil 21 and the second heating coil 22 as one inverter circuit.

When operating the first inverter 31 and the second inverter 32 as one inverter circuit, only one of the first switching element 13 and the second switching element 16 can be operated.

Alternatively, when the first inverter 31 and the second inverter 32 are operated as one inverter circuit, the first switching element 13 and the second switching element 16 may be driven in parallel with the same drive signal at the same timing. can. That is, the first switching element 13 and the second switching element 16 are turned on at the same timing and turned off at the same timing. Then, since the current of the inverter circuit is divided into two switching elements, the switching loss can be dispersed, and heat generation can be prevented from concentrating on one switching element.

Alternatively, when the first inverter 31 and the second inverter 32 are operated as one inverter circuit, the first switching element 13 and the second switching element 16 are alternately turned on at a predetermined cycle. may be energized. Then, since the energization time is divided between the first switching element 13 and the second switching element 16, the heat generation of the first switching element 13 and the second switching element 16 can be suppressed.

Thus, by operating the first inverter 31 and the second inverter 32 as one inverter circuit and energizing the first heating coil 21 and the second heating coil 22, the first heating coil 21 and the second heating coil The total power can also be doubled compared to when either one of 22 is energized. In addition, since high-frequency currents of the same frequency flow through the first heating coil 21 and the second heating coil 22, it is possible to suppress interference noise caused by the frequency difference.

When the time set in advance by the program elapses and the preheating process ends, the control unit 7 shifts to the temperature raising process, which is the next rice cooking process. The temperature raising process is a process from the end of the preheating process until the water in the inner pot 3 boils. When the water in the inner pot 3 boils in the temperature raising process, the boiling maintaining process is started and the boiling is maintained for a predetermined time. The boiling maintenance step promotes the gelatinization of rice starch.

(Operation during exclusive energization)
FIG. 4 is a diagram schematically showing an energization waveform when energizing the first heating coil 21 and the second heating coil 22 exclusively and alternately according to the first embodiment. Exclusive energization is performed in the temperature raising process and the boiling process. In the temperature raising process and the boiling process, since the water in the inner pot 3 is in a boiling state or in a state close to boiling, air bubbles are generated from the bottom of the pot and convection is generated in the inner pot 3 . In order to promote this convection and suppress the occurrence of uneven heating, a high-frequency current is alternately supplied to the first heating coil 21 and the second heating coil 22 .

Specifically, at the time of exclusive energization, the control unit 7 turns off the relay circuit 19 so that the first inverter 31 and the second inverter 32 can be individually driven. As shown in FIG. 4, during the period from time t1 to t2, the first heating coil 21 is energized by driving the first switching element 13 and turning off the second switching element 16 . Next, during the period from time t2 to t3, the second heating coil 22 is energized by driving the second switching element 16 and turning off the first switching element 13 .

By repeating the above operation, the inner peripheral portion and the outer peripheral portion of the bottom of the inner pot 3 are alternately heated to promote convection. At this time, the relay circuit 19 remains in the OFF state, and the switching of the energization of the first heating coil 21 and the second heating coil 22 does not involve the operation of the relay circuit, so the switching sound of the relay circuit 19 is not generated. and does not cause discomfort to the user. Also, the relay circuit 19 operates only once when switching from simultaneous energization of the first heating coil 21 and the second heating coil 22 to exclusive energization, or vice versa. For this reason, for example, compared to a method of alternately switching heating coils to be energized using a relay having a mechanical contact, the number of operations of the relay circuit 19 is greatly reduced, and the life of the relay circuit 19 can be extended. In addition, when the first heating coil 21 and the second heating coil 22 are alternately energized, the energization periods do not overlap each other, so the interference sound due to the frequency difference between the first heating coil 21 and the second heating coil 22 is does not occur.

By alternately energizing the first heating coil 21 and the second heating coil 22, the inner peripheral portion of the bottom of the inner pot 3 facing the first heating coil 21 and the second heating coil 22 are arranged facing each other. The outer peripheral portion of the bottom of the inner pot 3 is alternately heated. Then, convection due to air bubbles generated from the inner circumference of the bottom of the inner pot 3 and rising, and convection due to air bubbles generated from the outer circumference of the bottom of the inner pot 3 and rising alternately. This produces an action of stirring the inside of the inner pot 3 . Thereby, the occurrence of uneven heating in the inner pot 3 can be suppressed, and the taste of cooked rice can be improved.

In addition, when the first heating coil 21 and the second heating coil 22 are energized simultaneously and when one of the first heating coil 21 and the second heating coil 22 is energized, the power supplied to the inner pot 3 are the same. In this case, the heating area of the inner pot 3 is smaller when either one of the first heating coil 21 and the second heating coil 22 is energized, so the input power per unit area of the heat generating portion in the inner pot 3 increases, and the boiling of the heat-generating portion of the inner pot 3 becomes more intense. Therefore, by alternately switching the energization between the first heating coil 21 and the second heating coil 22, local heating can be strengthened, and a stronger convection effect can be obtained.

When the time set in advance by the program has passed and the boiling maintenance process is completed, the control unit 7 shifts to the next rice cooking process, which is the dry-up process. The dry-up process is a process for removing excess moisture. In the dry-up process, excess water is removed from the inner pot 3 and the inner pot 3 is in a dry-up state, so the temperature of the inner pot 3 becomes higher than that in the boiling maintaining step. In this drying process, there is almost no liquid water remaining in the inner pot 3, so no convection occurs. Therefore, it is not necessary to alternately energize the first heating coil 21 and the second heating coil 22 . In the present embodiment, in the dry-up process, the control unit 7 turns on the relay circuit 19 again to simultaneously energize the first heating coil 21 and the second heating coil 22 as shown in FIG. By doing so, the entire bottom surface of the inner pot 3 is uniformly heated, and temperature unevenness of the rice in the inner pot 3 is reduced. Also, the electric power supplied per unit area of the heating surface at the bottom of the inner pot 3 is reduced to suppress scorching.

When the drying process is completed, the control unit 7 shifts to the next process, which is the steaming process. When a predetermined time has passed in the steaming process, the rice cooking is finished. In the steaming process, the control unit 7 stops driving the first switching element 13 and the second switching element 16 and stops supplying the high-frequency current to the first heating coil 21 and the second heating coil 22 .

As described above, according to the present embodiment, the first heating coil 21, the second heating coil 22, the first inverter 31, and the second inverter 32 are provided. A first state in which high-frequency current supply from the first inverter 31 to the first heating coil 21 and high-frequency current supply from the second inverter 32 to the second heating coil 22 are individually executed; 1 inverter 31 and second inverter 32 are operated as one inverter, and a relay is used as switch means for electrically switching between a second state in which high-frequency current is supplied to first heating coil 21 and second heating coil 22 at the same time. A circuit 19 is provided.

By turning off the relay circuit 19, the first heating coil 21 and the second heating coil 22 can be alternately energized. Thereby, convection in the inner pot 3 can be promoted. When the first heating coil 21 and the second heating coil 22 are alternately energized, the relay circuit 19 is maintained in the OFF state, and switching of the relay circuit 19 does not occur. Therefore, since switching of the relay circuit 19 is not required for exclusive energization, deterioration of the relay circuit 19 can be suppressed.

By turning on the relay circuit 19, the first heating coil 21 and the second heating coil 22 are connected in parallel to the first inverter 31 and the second inverter 32 functioning as one inverter circuit. be. By turning on the relay circuit 19 and driving either one of the first switching element 13 and the second switching element 16, or switching the driving on and off at the same timing, the first heating coil 21 and the second heating coil 21 are switched. The coil 22 can be energized at the same frequency at the same time. By energizing the first heating coil 21 and the second heating coil 22 at the same frequency at the same time, the generation of interference noise is suppressed, and the wide bottom surface of the inner pot 3 can be heated.

Also, when the relay circuit 19 is in the ON state, the first heating coil 21 and the second heating coil 22 are connected in parallel, so the combined inductance is reduced, and the parallel connection of the first resonance capacitor 15 and the second resonance capacitor 18 is achieved. increases the combined capacitance. Therefore, depending on whether the relay circuit 19 is on or off, the resonance frequency formed by the heating coil and the resonance capacitor does not change greatly, and the driving conditions of the circuit do not change greatly, and the desired power can be supplied in either state. There is an advantage.

Embodiment 2.
This embodiment has a control section 70 and a drive signal selection circuit 80 instead of the control section 7 in the first embodiment. In this embodiment, differences from the first embodiment will be mainly described, and the same reference numerals will be given to the same or corresponding configurations as in the first embodiment, and the description will be simplified or omitted.

(circuit configuration)
FIG. 5 is a circuit block diagram of the induction heating cooker 1 according to Embodiment 2. As shown in FIG. The control unit 7 of Embodiment 1 generates driving signals for the first switching element 13 and the second switching element 16 by the microcomputer 7a, and transmits the generated driving signals to the first driving circuit 7b or the second driving circuit 7b. It was amplified by the circuit 7c. In this embodiment, as shown in FIG. 5, the inverter circuit board 6 has a control section 70 and a drive signal selection circuit 80 .

The control unit 70 has a microcomputer 70a and a drive circuit 70b. The basic configuration of the microcomputer 70a is the same as that of the microcomputer 7a of the first embodiment. The basic configuration of the drive circuit 70b is the same as the first drive circuit 7b and the second drive circuit 7c of the first embodiment.

The drive signal selection circuit 80 has a first switch 81 and a second switch 82 . The first switch 81 and the second switch 82 are semiconductor switches such as transistors and MOSFETs. The first switch 81 is connected to the gate terminal of the first switching element 13 and the second switch 82 is connected to the gate terminal of the second switching element 16 .

The microcomputer 70a outputs a driving signal from one output terminal both when driving the first switching element 13 and when driving the second switching element 16, and the output driving signal is input to the driving circuit 70b. Also, the microcomputer 70a is connected to the first switch 81 and the second switch 82, and outputs a signal for switching between the ON state and the OFF state of these switch elements.

Next, the operation of the induction heating cooker 1 will be described. Here, the operation of the induction heating cooker 1 during simultaneous energization and exclusive energization will be described, taking as an example the case of cooking rice in the same manner as in the first embodiment.

(Operation during simultaneous energization)
FIG. 6 is a diagram showing a simplified energization waveform when simultaneously energizing the first heating coil 21 and the second heating coil 22 according to the second embodiment. In FIG. 6, the conductive state of the first switch 81 and the second switch 82 is simply shown as ON, and the cut-off state is OFF. When simultaneously energizing the first heating coil 21 and the second heating coil 22, the controller 70 outputs an ON signal to the relay circuit 19 (see FIG. 5) so that the relay circuit 19 is turned ON.

First, the microcomputer 70a brings the first switch 81 and the second switch 82 into conduction in advance (time t1). Next, the microcomputer 70a outputs drive signals for driving the first switching element 13 and the second switching element 16. FIG. The output drive signal is input to the drive circuit 70b shown in FIG. The driving circuit 70 b amplifies the input driving signal to a voltage suitable for driving the first switching element 13 and the second switching element 16 and outputs the amplified driving signal to the driving signal selection circuit 80 .

In the drive signal selection circuit 80, since the first switch 81 and the second switch 82 are in a conductive state, the switching drive signal is input to the gate terminals of both the first switching element 13 and the second switching element 16. be. As a result, the first switching element 13 and the second switching element 16 start driving at the same time (time t2).

When a predetermined time has passed since the first heating coil 21 and the second heating coil 22 were simultaneously energized, the microcomputer 7a stops outputting the switching drive signal (time t3 to time t4), and restarts the switching drive signal. is output (time t4). By repeating such operations, simultaneous energization of the first heating coil 21 and the second heating coil 22 is intermittently performed.

By simultaneously driving the first switching element 13 and the second switching element 16, the first heating coil 21 and the second heating coil 22 are simultaneously energized. As described in the first embodiment, both the first switching element 13 and the second switching element 16 may be turned on or off at the same timing, or may be turned on alternately. Alternatively, only one of the first switching element 13 and the second switching element 16 may be driven, and even in this case, both the first heating coil 21 and the second heating coil 22 can be energized at the same time. In that case, only the first switch 81 or the second switch 82 connected to the driven one of the first switching element 13 and the second switching element 16 should be made conductive.

(Operation during exclusive energization)
FIG. 7 is a diagram showing a simplified energization waveform when energizing the first heating coil 21 and the second heating coil 22 exclusively and alternately according to the second embodiment. When alternately energizing the first heating coil 21 and the second heating coil 22, the controller 70 outputs an off signal to the relay circuit 19 (see FIG. 5) so that the relay circuit 19 is turned off.

First, when the first heating coil 21 is energized, the microcomputer 70a turns on the first switch 81 of the drive signal selection circuit 80, turns off the second switch 82, and maintains the state (time t1). In this state, when an element drive signal is output from the microcomputer 7a, the drive signal is input to the gate terminal of the first switching element 13 via the drive circuit 70b. When the drive signal is input, the first switching element 13 performs a switching operation to energize the first heating coil 21 (time t1 to time t2). By energizing the first heating coil 21, the inner periphery of the bottom of the inner pot 3 is heated.

After a predetermined time has passed, the microcomputer 70a turns off the first switch 81 of the drive signal selection circuit 80 and turns on the second switch 82 to energize the second heating coil 22. (time t2). In this state, when a drive signal is output from the microcomputer 70a, the drive signal is input to the gate terminal of the second switching element 16 via the drive circuit 70b. When the drive signal is input, the second switching element 16 performs a switching operation to energize the second heating coil 22 (time t2 to time t3). By energizing the second heating coil 22, the outer peripheral portion of the bottom of the inner pot 3 is heated.

By alternately energizing the first heating coil 21 and energizing the second heating coil 22, the inner peripheral portion and the outer peripheral portion of the bottom of the inner pot 3 are alternately heated, and the convection in the inner pot 3 is promoted.

According to the present embodiment, a circuit for outputting drive signals for driving the two first switching elements 13 and the second switching elements 16 is shared. Therefore, both when driving the first switching element 13 and when driving the second switching element 16, the microcomputer 70a should output a 1ch (channel) PWM signal. Therefore, low-capacity, low-cost components can be employed in the microcomputer 70a. Further, the drive signal selection circuit 80 is connected to the rear stage of the drive circuit 70b. The drive signal selection circuit 80 selectively inputs the drive signal output from the drive circuit 70 b to either or both of the first switching element 13 and the second switching element 16 . Therefore, one drive circuit 70b can be shared by the two first switching elements 13 and the second switching elements 16. FIG. Therefore, single driving and simultaneous driving of the two first switching elements 13 and the second switching elements 16 can be realized by one driving circuit 70b. Therefore, the size and cost of the inverter circuit board 6 can be reduced.

(Modified example of operation during exclusive energization)
When the ON/OFF states of the first switch 81 and the second switch 82 of the drive signal selection circuit 80 are switched while the switching drive signal is continuously output from the microcomputer 7a, the first switching element 13 or the second switching element 13 is switched at the moment of switching. An excessive rush current may flow through the switching element 16 and destroy it. A modified example of the operation at the time of exclusive energization, which has been studied based on such a background, will be described.

FIG. 8 is a diagram showing a simplified modification of the energization waveform when the first heating coil 21 and the second heating coil 22 are alternately energized according to the second embodiment. In this modification, the microcomputer 70a temporarily stops outputting the drive signal to the first switching element 13 or the second switching element 16 when switching the ON/OFF states of the first switch 81 and the second switch 82. .

Specifically, a case of switching from energization of the first heating coil 21 to energization of the second heating coil 22 from time t3 to time t5 will be described as an example. At time t3, the microcomputer 70a stops outputting the drive signal for energizing the first heating coil 21, and stops the switching operation of the first switching element 13. FIG. When it does so, the electricity supply to the 1st heating coil 21 will stop. Next, at time t4, the microcomputer 70a turns off the first switch 81 and turns on the second switch 82. As shown in FIG. Next, at time t5, the microcomputer 70a starts outputting a drive signal for energizing the second heating coil 22, causing the second switching element 16 to start switching operation. When played, energization to the second heating coil 22 starts. By doing so, it is possible to suppress excessive inrush current from flowing through the second switching element 16 that has switched from the stopped state to the switching operation state, and to suppress damage to the second switching element 16 . Also when the first switching element 13 is switched from the stopped state to the switching operation state, the same control is performed and the same action can be produced.

Further, when the first switching element 13 and the second switching element 16 start switching operations, the microcomputer 70a may gradually lengthen the ON time of the switching operations from a short time. In this way, the current supplied to the first heating coil 21 and the second heating coil 22 gradually increases from the start of supply and approaches the target current. By executing such a soft start, an excessive rush current is generated in the first switching element 13 and the second switching element 16 immediately after the first switch 81 and the second switch 82 are switched between the conductive state and the cut-off state. It can be suppressed to flow and be damaged.

In the first and second embodiments, the operation of the induction heating cooker 1 has been described by taking the rice cooking process as an example. In addition, in the first and second embodiments, the heating cooker including the housing 2 and the lid 8 that accommodates the inner pot 3 containing the ingredients has been described as an example, but the specific configuration of the induction heating cooker. are not limited to those exemplified in the first and second embodiments. For example, the present invention can be applied to a heating cooker having a housing containing a heating coil and a top plate provided thereon, in which an object to be heated such as a pot placed on the top plate is induction-heated by the heating coil. The invention can be applied and the same effects can be obtained.

Moreover, although the case where two heating coils, ie, the 1st heating coil 21 and the 2nd heating coil 22, were provided was illustrated in the said Embodiment 1, 2, the number of heating coils is not limited to this. Three or more heating coils and the same number of inverters for heating one object to be heated may be provided. In this case, when simultaneously energizing a plurality of heating coils, the plurality of inverters of the target heating coils are operated as one inverter by the relay circuit 19 exemplified in the first and second embodiments. The same effects as those of the first and second forms are obtained.

REFERENCE SIGNS LIST 1 induction heating cooker 2 housing 3 inner pot 4 inner pot storage unit 6 inverter circuit board 7 control unit 7a microcomputer 7b first drive circuit 7c second drive circuit 8 lid 9 lid Open/Close Button 11 Rectifier Circuit 12 Filter Circuit 13 First Switching Element 14 First Freewheeling Diode 15 First Resonant Capacitor 16 Second Switching Element 17 Second Freewheeling Diode 18 Second Resonant Capacitor 19 Relay Circuit , 21 first heating coil, 21a one end, 21b other end, 22 second heating coil, 22a one end, 22b other end, 25 first connection point, 26 second connection point, 31 first inverter, 32 second inverter, 70 Control section 70a Microcomputer 70b Drive circuit 80 Drive signal selection circuit 81 First switch 82 Second switch.

Claims (7)

a first heating coil that heats the object to be heated;
a second heating coil that heats the object to be heated;
a first inverter;
a second inverter;
a first state in which high-frequency current supply from the first inverter to the first heating coil and high-frequency current supply from the second inverter to the second heating coil are performed separately; Switching means for electrically switching between a second state in which the inverter and the second inverter are operated as one inverter and a high-frequency current is supplied to the first heating coil and the second heating coil at the same time ,
the first inverter is composed of a single-switch voltage resonance inverter having a first switching element,
the second inverter is composed of a single-switch voltage resonance inverter having a second switching element,
one end of the first heating coil and one end of the second heating coil are electrically connected,
The other end of the first heating coil is connected to the first switching element,
The other end of the second heating coil is connected to the second switching element,
The switch means is provided at a position for electrically connecting a connection point between the first heating coil and the first switching element and a connection point between the second heating coil and the second switching element. there is
induction cooker. a first heating coil that heats the object to be heated;
a second heating coil that heats the object to be heated;
a first inverter;
a second inverter;
a first state in which high-frequency current supply from the first inverter to the first heating coil and high-frequency current supply from the second inverter to the second heating coil are performed separately; Switching means for electrically switching between a second state in which the inverter and the second inverter are operated as one inverter and a high-frequency current is supplied to the first heating coil and the second heating coil at the same time,
the first inverter is composed of a single-switch voltage resonance inverter having a first switching element,
the second inverter is composed of a single-switch voltage resonance inverter having a second switching element,
one end of the first heating coil and one end of the second heating coil are electrically connected,
The other end of the first heating coil is connected to the first switching element,
The other end of the second heating coil is connected to the second switching element,
The switch means is provided at a position for electrically connecting a connection point between the first heating coil and the first switching element and a connection point between the second heating coil and the second switching element. cage,
In the second state, the first switching element and the second switching element have a period in which they are in the ON state at the same timing and a period in which they are in the OFF state at the same timing.
induction cooker. a first heating coil that heats the object to be heated;
a second heating coil that heats the object to be heated;
a first inverter;
a second inverter;
a first state in which high-frequency current supply from the first inverter to the first heating coil and high-frequency current supply from the second inverter to the second heating coil are performed separately; Switching means for electrically switching between a second state in which the inverter and the second inverter are operated as one inverter and a high-frequency current is supplied to the first heating coil and the second heating coil at the same time,
the first inverter is composed of a single-switch voltage resonance inverter having a first switching element,
the second inverter is composed of a single-switch voltage resonance inverter having a second switching element,
one end of the first heating coil and one end of the second heating coil are electrically connected,
The other end of the first heating coil is connected to the first switching element,
The other end of the second heating coil is connected to the second switching element,
The switch means is provided at a position for electrically connecting a connection point between the first heating coil and the first switching element and a connection point between the second heating coil and the second switching element. cage,
In the second state, only one of the first switching element and the second switching element operates.
induction cooker. a first heating coil that heats the object to be heated;
a second heating coil that heats the object to be heated;
a first inverter;
a second inverter;
a first state in which high-frequency current supply from the first inverter to the first heating coil and high-frequency current supply from the second inverter to the second heating coil are performed separately; Switching means for electrically switching between a second state in which the inverter and the second inverter are operated as one inverter and a high-frequency current is supplied to the first heating coil and the second heating coil at the same time,
the first inverter is composed of a single-switch voltage resonance inverter having a first switching element,
the second inverter is composed of a single-switch voltage resonance inverter having a second switching element,
one end of the first heating coil and one end of the second heating coil are electrically connected,
The other end of the first heating coil is connected to the first switching element,
The other end of the second heating coil is connected to the second switching element,
The switch means is provided at a position for electrically connecting a connection point between the first heating coil and the first switching element and a connection point between the second heating coil and the second switching element. cage,
In the second state, the first switching element and the second switching element are alternately turned on.
induction cooker. a drive signal generator that generates a drive signal for the first switching element and a drive signal for the second switching element;
a first drive circuit that amplifies the voltage of the drive signal for the first switching element generated by the drive signal generator;
The induction heating cooker according to any one of claims 1 to 4, further comprising a second drive circuit that amplifies the voltage of the drive signal for the second switching element generated from the drive signal generator. . a drive signal generator that generates a drive signal for the first switching element and a drive signal for the second switching element;
a drive circuit that amplifies the voltage of the drive signal generated from the drive signal generator;
and a drive signal selection circuit that selectively inputs the signal output from the drive circuit to either or both of the first switching element and the second switching element. or the induction heating cooker according to claim 1. The first state includes a state in which high-frequency current is supplied only to the first heating coil and a state in which high - frequency current is supplied only to the second heating coil. The induction heating cooker according to the item.

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