JP5083418B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker that performs cooking for a long time with power lower than a predetermined power.

In the conventional induction heating cooker, when cooking for a long time with electric power lower than the predetermined electric power W1, the heating output is periodically increased to a predetermined output W2 larger than the predetermined output W1, and the moisture in the pot Can be boiled for a short time to stimulate convection in the pan, and the simmered ingredients can be stirred by the convection (for example, Patent Document 1).
JP-A-5-121153

  Since the conventional induction heating cooker is configured as described above, when the object to be heated is boiled by boiling cooking, bubbles are generated, and when the bubbles bounce, the droplets are generated and scattered. And there was a problem that a part of the splashes splattered outside the pan and soiled the periphery of the pan. The present invention has been made to solve such problems.

  An induction heating cooker according to the present invention includes a DC power supply circuit that rectifies AC power and converts it into DC power, an inverter circuit that converts DC power output from the DC power supply circuit into high-frequency power, and the inverter circuit. Driven by the converted high-frequency power, a heating coil having an inner coil that heats the center of the installed pan, an outer coil that heats the outer periphery of the pan, and arouses convection in the pan, An operation key operated when cooking to stir the material by the convection, and when the operation key is operated, the inverter circuit is controlled, and the high frequency power output to the outer coil is supplied to the outer coil. And a control means for lowering the high-frequency power output from the heating density divided by the area to the inner coil to be lower than the heating density divided by the area of the inner coil.

  In the induction heating cooker according to the present invention, since the heating density obtained by dividing the high frequency power to the outer coil by the area of the outer coil is controlled to be lower than the heating density obtained by dividing the high frequency power to the inner coil by the area of the inner coil. In addition, it is possible to suppress the generation of boiling bubbles at the outer periphery of the pan near the pan wall, and to suppress the splashing of the food to be cooked outside the pan.

Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
1 is a circuit diagram of an induction heating cooker according to Embodiment 1 of the present invention. In the figure, power supplied from a commercial AC power supply 1 is converted into DC power by a DC power supply circuit 2.

  The DC power supply circuit 2 includes a rectifier diode bridge 3 that rectifies AC power, a reactor 4, and a smoothing capacitor 5. The input current input to the DC power supply circuit 2 is detected by the input current detection circuit 6. The electric power converted into DC power by the DC power supply circuit 2 is supplied to an inverter circuit 7 shown as a region surrounded by a broken line in the figure.

  The inverter circuit 7 includes three sets of arms configured by two switching elements (IGBTs) connected in series between the DC buses of the DC power supply circuit 2 and diodes connected to the switching elements in antiparallel. It consists of 8, 9, and 10.

  The arm 8 is an arm common to the inner coil and the outer coil connected to the inner coil load circuit and the outer coil load circuit. In the common arm 8, a switching element 11 (upper switch 11) is disposed on the high potential side, and a switching element 12 (lower switch 12) is disposed on the low potential side. A diode 13 is connected to the upper switch 11 in antiparallel, and a diode 14 is connected to the lower switch 12 in antiparallel. A connection point between the upper switch 11 and the lower switch 12 is an output point of the common arm 8, and a snubber capacitor 15 is connected to the lower switch 12 in parallel.

  The arm 9 is provided for the inner coil, and the inner coil load circuit 29 is connected thereto. In the inner coil arm 9, a switching element 16 (upper switch 16) is disposed on the high potential side, and a switching element 17 (lower switch 17) is disposed on the low potential side. A diode 18 is connected in antiparallel to the switching element 16, and a diode 19 is connected in antiparallel to the switching element 17. A snubber capacitor 20 is connected to the lower switch 17 in parallel.

  The arm 10 is provided for an outer coil, and an outer coil load circuit 30 is connected thereto. The outer coil arm 10 is provided with a switching element 21 on the high potential side and a switching element 22 on the low potential side. A diode 23 is connected to the switching element 21 in antiparallel, and a diode 24 is connected to the switching element 22 in antiparallel. A snubber capacitor 25 is connected to the lower switch 22 in parallel.

  The upper switch 11 and the lower switch 12 of the common arm 8 are turned on / off by a drive signal output from the common arm drive circuit 26, and the upper switch 16 and the lower switch 17 of the inner coil arm 9 are driven by the inner coil arm drive circuit 27. The upper switch 21 and the lower switch 22 of the outer coil arm 10 are turned on and off by the drive signal output from the outer coil arm drive circuit 28.

  The common arm drive circuit 26 turns off the lower switch 12 while the upper switch 11 of the common arm 8 is turned on, turns the lower switch 12 on while the upper switch 11 is turned off, and turns on and off alternately. Similarly, the inner coil arm drive circuit 27 outputs a drive signal for alternately turning on and off the upper switch 16 and the lower switch 17 of the inner coil arm 9, and drives the outer coil arm. Similarly, the circuit 28 outputs a drive signal for alternately turning on and off the upper switch 21 and the lower switch 22 of the outer coil arm 10.

  The snubber capacitors 15, 20, and 25 delay the fluctuations in the output voltage when the switches 11, 12, 16, 17, 21, and 22 are turned off in the common arm 8, the inner coil arm 9, and the outer coil arm 10, respectively. The switching element is provided to reduce the turn-off loss.

  The inner coil load circuit 29 is a series resonance circuit composed of the inner coil 31 and the resonance capacitor 32, and the output point of the common arm 8 (the connection point between the upper switch 11 and the lower switch 12) and the inner coil arm 9. It is connected between the output points (the connection point between the upper switch 16 and the lower switch 17).

  The outer coil load circuit 30 is a series resonance circuit composed of an outer coil 33 and a resonance capacitor 34. The output point of the common arm 8 and the output point of the outer coil arm 10 (connection between the upper switch 21 and the lower switch 22). Point).

  The inner coil 31 is a heating coil having a small outer shape wound in a substantially circular shape, and an annular outer coil 33 is wound around the outer periphery thereof, and the center positions of the inner coil 31 and the outer coil 33 are substantially the same. They are arranged so as to coincide with each other or concentrically. The inner coil 31 and the outer coil 33 are wound and connected in the same circumferential direction as viewed from the common arm 8, and the current flowing through the inner coil 31 and the outer coil 33 is detected by the output current detection circuit 35. Is done.

  The control circuit 36 controls the induction heating cooker according to the first embodiment of the present invention. The control circuit 36 has a control timer 36a therein, and the operation state is displayed on the display unit 38 according to an input instruction from the operation input means 37. While displaying, the arm drive circuits 26 to 28 are controlled while taking in the detection values of the input current detection circuit 6 and the output current detection circuit 35 to adjust the heating output.

  The drive signal output to the arms 8 to 10 has a drive frequency higher than the resonance frequency of the inner coil load circuit 29 and the outer coil load circuit 30 and is out of phase with the voltage applied to the load circuit. Control so that current flows through the load circuit.

  The operation input means 37 has means (for example, a stew key) 37a that instructs the inner coil 31 and the outer coil 33 to alternately output a high-frequency current. Based on the operation of the instruction means 37a, the control circuit 36 controls the arm drive circuits 26 to 28 to alternately output a high-frequency current to the inner coil 31 and the outer coil 33.

  FIG. 2 is a time chart of the set power output to the inner coil load circuit 29 and the outer coil load circuit 30 in the inner / outer coil alternate output state of the induction heating cooker according to the first embodiment of the present invention. As shown in the figure, in the alternating output state of the inner and outer coils, the output state of the high frequency power to the inner coil load circuit and the output state of the high frequency power to the outer coil load circuit are alternately switched.

  Here, compared with the set power in the high-frequency power output state to the inner coil load circuit 29, the set power in the high-frequency power output state to the outer coil load circuit 30 is set to a smaller value. In the example of FIG. 2, the input power when the inner coil is energized is 500 W, and the input power when the outer coil is energized is 300 W.

  FIG. 3 is a timing chart of drive signals output from the arm drive circuits 26 to 28 to the upper switch and the lower switch of the arms 8 to 10 when high frequency power is output to the inner coil load circuit 29. In this way, high-frequency drive signals are output to the upper switch 11 and the lower switch 12 of the common arm 8, and a drive signal whose phase is advanced from the drive signal is transmitted to the upper switch 16 and the lower switch of the inner coil arm 9. Output to the switch 17, the upper switch 21 and the lower switch 22 of the outer coil arm 10 are turned off.

  In this case, a potential that varies at a high frequency is applied to the output points of the common arm 8 and the inner coil arm 9 according to the on / off state of the upper switch and the lower switch, and the potential difference is applied to the inner coil load circuit 29. .

  The output point potential of the outer coil arm 10 is indefinite because the upper switch 21 and the lower switch 22 are in the OFF state (however, since it is clamped by the upper diode 23 and the lower diode 24, it is a negative output that is the output of the DC power supply circuit 2). The potential is in a range between the bus potential and the positive bus potential, and no high frequency voltage is applied to the outer coil load circuit 30.

  Therefore, by increasing or decreasing the phase difference between the drive signal to the common arm 8 and the drive signal to the inner coil arm 9, the high frequency voltage applied to the inner coil load circuit 29 can be adjusted and flows to the inner coil 31. High frequency output current and input current can be controlled.

  On the other hand, FIG. 4 is a timing chart showing an example of drive signals output from the arm drive circuits 26 to 28 to the upper switch and the lower switch of the arms 8 to 10 when high frequency power is output to the outer coil load circuit 30. . In this way, high-frequency drive signals are output to the upper switch 11 and the lower switch 12 of the common arm 8, and the drive signals whose phase is advanced from the drive signals are the upper switch 21 and the lower switch of the outer coil arm 10. 22 and the upper switch 16 and the lower switch 17 of the inner coil arm 9 are turned off.

  In this case, a potential that fluctuates at a high frequency according to the on / off state of the upper switch and the lower switch is output to the output points of the common arm 8 and the outer coil arm 10, and the potential difference is applied to the outer coil load circuit 30. . The output point potential of the inner coil arm 9 is indefinite because the upper switch 16 and the lower switch 17 are in the OFF state (however, since it is clamped by the upper diode 18 and the lower diode 19, it is a negative output that is the output of the DC power supply circuit 2). The range is not less than the bus potential and not more than the positive bus potential), and no high frequency voltage is applied to the inner coil load circuit 29.

  Therefore, by increasing or decreasing the phase difference between the drive signal to the common arm 8 and the drive signal to the outer coil arm 10, the high frequency voltage applied to the outer coil load circuit 30 can be adjusted and flows to the outer coil 33. High frequency output current and input current can be controlled.

  FIG. 5 is a conceptual diagram showing the state of the magnetic flux generated in a state where a high-frequency current is passed through the inner coil 31 or the outer coil 33 and the bubbles or splashes of the cooking object generated in the pan. FIG. 5A shows a state in which a high-frequency current is passed through the inner coil 31, and an arrow that circulates around the inner coil 31 represents a state of magnetic flux generated by the high-frequency current flowing through the inner coil 31. .

  Reference numeral 40 in the figure denotes a plate-like ferrite that magnetically shields the lower surfaces of the inner coil 31 and the outer coil 33. Reference numeral 41 denotes a top plate for placing an object to be heated such as a pan, on which a large-diameter pan 39 is placed. A coil base 42 fixes the inner coil 31, the outer coil 33, the ferrite 40, and the like. Most of the magnetic flux generated by the high-frequency current flowing in the inner coil 31 is linked with the bottom of the large-diameter pan 39 near the center and induces an eddy current near the center of the bottom of the pan to heat and heat the cooked food in the pan. Is boiled to generate bubbles 43. When the bubble 43 is flipped, a part of the cooking object is scattered as the splash 44.

  FIG. 5B shows a state in which a high-frequency current is passed through the outer coil 33, and the arrows that circulate around the outer coil 33 represent the state of magnetic flux generated by the high-frequency current that flows through the outer coil 33. Is. The magnetic flux generated by the high-frequency current flowing in the outer coil 33 is linked with the large-diameter pan 39 and the outer periphery of the pan bottom, induces eddy currents in the outer peripheral portion of the pan bottom, and heats to boil the moisture of the cooking object in the pan. . As a result, when the generated bubbles bounce, a part of the object to be cooked scatters as splashes.

  FIG. 6 is a flowchart of the inner / outer coil alternate output control process by the control means 36. First, when the heating start instruction for the alternate output of the inner and outer coils is input by the stew key 37a of the operation input means 37, the counter of the timer 36a is cleared and started (step S1). The control means 36 controls the common arm drive circuit 26 and the inner coil arm drive circuit 27 to send drive signals as shown in FIG. 3 to the upper and lower switches 11 and 12 of the common arm 8 and the inner coil. Output to the up / down switches 16 and 17 of the arm 9 to start application of the high frequency voltage to the inner coil load circuit 29 (step S2).

  Next, each current is detected using the input current detection circuit 6 and the output current detection circuit 35 (step S3), and it is determined whether the output current is excessive (step S4). When the output current is excessive (step S4: Yes), the process proceeds to step S7 in order to suppress the output current. The process of step S7 will be described later.

  On the other hand, if the output current is not excessive (step S4: No), the input power converted from the detected input current (converted as a constant power supply voltage, for example, 100V) and the set power P1 when the inner coil is energized (see FIG. 2) ) Are compared (step S5). P1 is 500 W in the example of FIG.

  As a result, when the input power is smaller, the phase difference between the drive signal to the common arm 8 and the drive signal to the inner coil arm 9 is increased in order to increase the input power (step S6), and step S8. Proceed to On the other hand, when the input power is larger than the set power P1, the process proceeds to step S7 in order to decrease the input power, similarly to the case where the output current is excessive (step S4: Yes).

  In step S7, the phase difference between the drive signal to the common arm 8 and the drive signal to the inner coil arm 9 is reduced (step S7), and the process proceeds to step S8.

  When the input power and the set power P1 are equal, the process proceeds directly to step S8 without changing the phase difference of the drive signals.

  In step S8, the timer 36a is checked to check whether the counter value has reached a predetermined time T1. If T1 has not been reached (step S8: No), the processing of steps S3 to S7 is executed again. If the predetermined time T1 has been reached (step S8: Yes), the process proceeds to step S9.

  In step S9, the presence or absence of the pan is determined from the values of the input current and the output current. Here, for example, if the input current is equal to or less than a predetermined ratio with respect to the output current, it is determined that there is no pan. Note that other known load detection methods can be applied to determine the presence or absence of a pan. As a result, if it is determined that there is a pan (step S9: Yes), the process proceeds to step S10. If it is determined that there is no pan (step S9: No), the process proceeds to step S21. The processing after step S21 will be described later.

  In step S <b> 10, it is determined whether or not there is a heating stop instruction input from the operation input unit 37. Also when there exists a heating stop instruction | indication input (step S10: Yes), it progresses to step S21.

  When there is no heating stop instruction input (step S10: No), the drive signal output from the common arm drive circuit 26 and the inner coil arm drive circuit 27 is stopped and the high frequency current to the inner coil load circuit 29 is reduced. The output is stopped (step S11), the counter of the timer 36a is cleared and restarted (step S12). 4 is output to the upper and lower switches 11 and 12 of the common arm 8 and the upper and lower switches 21 and 22 of the outer coil arm 10, and the high-frequency voltage to the outer coil load circuit 30 is output. Application is started (step S13).

  Next, each current is detected using the input current detection circuit 6 and the output current detection circuit 35 (step S14), and it is determined whether or not the output current is excessive (step S15). When the output current is excessive (step S15: Yes), the process proceeds to step 18 to reduce the phase difference of the drive signal in order to suppress the output current. The processing after step S18 will be described later.

  When the output current is not excessive (step S15: No), the input power converted from the detected input current is compared with the set power P2 when the outer coil is energized (step S16). In the example shown in FIG. 2, the set power P2 is 300W.

  As a result, when the input power is smaller, the phase difference between the drive signal to the common arm 8 and the drive signal to the outer coil arm 10 is increased in order to increase the input power (step S17). Proceed to S19. Conversely, if the input power is larger than the set power P2, the process proceeds to step S18 to decrease the input power, as in the case where the output power is excessive (step S15: Yes).

  In step S18, the phase difference between the drive signal to the common arm 8 and the drive signal to the outer coil arm 10 is reduced (step S18), and the process proceeds to step S19.

  If the input power and the set power P2 are equal, the process proceeds directly to step S19 without changing the phase difference of the drive signals.

  In step S19, the timer 36a is confirmed. If the counter value has not reached the predetermined time T2 (step S19: No), the processing from step S14 is repeated. On the other hand, when the predetermined time T2 has been reached (step S19: Yes), the drive signal output from the common arm drive circuit 26 and the outer coil arm drive circuit 28 is stopped and the high frequency current to the outer coil load circuit 30 is stopped. (Step S20), the process returns to step S1 and shifts to the output of high-frequency power to the inner coil load circuit 29.

  If it is determined that there is no pan in step S9, or if an instruction to stop heating is input in step S10, the process from step S21 is executed. Here, the common arm drive circuit 26 and the inner coil are used. The drive signal output from the arm drive circuit 27 is stopped, the output of the high frequency current to the inner coil load circuit 29 is stopped (step S21), the count of the timer 36a is stopped (step S22), and the inner and outer coil alternate output control is performed. The process ends.

  As described above, in the induction heating cooker according to the first embodiment of the present invention, the central portion and the outer peripheral portion of the pan are alternately heated by flowing high-frequency current alternately to the inner coil 31 and the outer coil 33 to heat them. The food can be stirred by boiling.

  In addition, by suppressing the heating amount in the outer peripheral heating state in which the high frequency current is supplied to the outer coil 33 from the central heating state in which the high frequency current is supplied to the inner coil 31, the bubbling bubbles generated in the outer peripheral portion near the pan wall can be repelled. Therefore, it is possible to suppress the occurrence of splashing, and to reduce the splashing of the top plate and the like around the pan from the pan wall.

  In the description so far, the case where the heating coil includes two coils of the inner coil and the outer coil is described, but the number of coils is not limited. That is, three or more coils may be arranged concentrically, in which case the application range of the present invention can be expanded by repeating the cycle of energizing each coil in different time zones. You can easily imagine that it is possible.

Embodiment 2. FIG.
When boiling the water of the cooking object in the pan by heating the pot, the higher the heating density, the more intense bubbles are generated, and when the bubbles bounce, there is the property that the splashes of the cooking object will be scattered higher and further away . Then, in addition to the structure of the induction heating cooking appliance which concerns on Embodiment 1 of this invention, it leaves | separates from a pan wall by making the heating density by the high frequency current which flows into an outer coil smaller than the heating density by the high frequency current which flows into an inner coil. Compared with the occurrence of splashes at the center of the pan, the occurrence of splashes at the outer periphery of the pan near the pan wall can be further reduced, and the splashing outside the pan can be suppressed.

  The induction heating cooker of Embodiment 2 of this invention has such a feature. In addition, since the induction heating cooker according to Embodiment 2 of the present invention is the same as the induction heating cooker according to Embodiment 1 except for the heating coil portion, detailed description of the components will be omitted.

  FIG. 7 is a front view of a heating coil of an induction heating cooker according to Embodiment 2 of the present invention. The heating coil of this induction heating cooker is composed of an inner coil 31 and an outer coil 33. The area of the heating coil facing the bottom of the pan to be heated (the area of the heating coil projected perpendicularly to the bottom of the pan) is the inner coil 31. Is S1, and the outer coil 33 is S2.

  FIG. 8 is a time chart showing the relationship between the set power output to the inner coil load circuit 29 and the set power output to the outer coil load circuit 30 in the induction heating cooker according to the second embodiment of the present invention. Also in this induction heating cooker, the output state of the high frequency power to the inner coil load circuit 29 and the output state of the high frequency power to the outer coil load circuit are alternately switched as in the first embodiment.

  At that time, the set power P20 in the high frequency current output state to the outer coil load circuit 30 is smaller in the heating density of the pan bottom than the set power P10 in the high frequency power output state to the inner coil load circuit 29 (P20 / S2 < P10 / S1).

  As a result of setting in this way, this induction heating cooker suppresses the heating density in the outer peripheral portion near the pan wall (the pan side or the pan skin).

  As already described, when the heating density is high, the boiling of water in the object to be heated becomes intense and the generation of bubbles becomes active, and when the bubbles bounce, the splashes are scattered higher and further away. Therefore, in the induction heating cooker according to the second embodiment of the present invention, by suppressing the heating density of the outer peripheral portion near the pan wall, the occurrence of splashes in the vicinity of the pan wall is suppressed, and the splashes of the cooking object are scattered outside the pan wall. The top plate around the pan can be prevented from getting dirty.

  In this case as well, the number of coils is not limited to two, that is, an inner coil and an outer coil, and three or more coils may be arranged concentrically. In that case, the output setting may be selected based on the area.

Embodiment 3 FIG.
FIG. 9 is a circuit diagram of an induction heating cooker according to Embodiment 3 of the present invention. In the figure, the same reference numerals are given to the same or corresponding parts as those in FIG.

  In the figure, power supplied from a commercial AC power supply 1 is converted into DC power by DC power supply circuits 2a and 2b. The DC power converted by the DC power supply circuit 2a is supplied to the inner coil inverter circuit 45, and the DC power converted by the DC power supply circuit 2b is supplied to the outer coil inverter circuit 46.

  The DC power supply circuits 2a and 2b are composed of rectifier diode bridges 3a and 3b for rectifying AC power, reactors 4a and 4b, and smoothing capacitors 5a and 5b, respectively, and the input current is input by input current detection circuits 6a and 6b. The input voltages are individually detected by the input voltage detection circuits 59a and 59b.

  The internal coil inverter circuit 45 includes two switching elements connected in series between the DC buses of the DC power supply circuit 2a (the upper switch 47 on the high potential side switching element and the lower switch 48 on the low potential side switching element). And a diode (an upper diode 49 on the high potential side antiparallel diode and a lower diode 50 on the low potential side antiparallel diode) connected to the switching element in antiparallel, and the upper switch 47 and the lower switch. Forty-eight connection points are output points.

  A snubber capacitor 51 is connected in parallel to the lower switch 48, and the fluctuation of the output voltage when the upper switch 47 and the lower switch 48 are turned off is delayed to reduce the loss of the switching element.

  Similarly to the inner coil inverter circuit 45, the outer coil inverter circuit 46 includes two switching elements (the upper switch 52 of the switching element on the high potential side, the low potential) connected in series between the DC buses of the DC power supply circuit 2b. Lower switching element 53) and diodes connected to the switching element in antiparallel (the upper diode 54 of the high potential side antiparallel diode and the lower diode 55 of the low potential side antiparallel diode). The connection point between the upper switch 52 and the lower switch 53 is an output point.

  A snubber capacitor 56 is connected to the lower switch 53 in parallel to delay the fluctuation of the output voltage when the upper switch 52 and the lower switch 53 are turned off, thereby reducing the loss of the switching element.

  The upper switch 47 and the lower switch 48 of the inner coil inverter circuit 45 are alternately turned on and off by the drive signal output from the inner coil inverter drive circuit 60, and the upper switch 52 and the lower switch 53 of the outer coil inverter circuit 46 are driven. Are alternately turned on and off by the drive signal output from the inverter drive circuit 61 for the outer coil.

  The inner coil load circuit 29 is a series resonance circuit including an inner coil 31 and a resonance capacitor 32, and an output point of the inner coil inverter circuit 45 (a connection point between the upper switch 47 and the lower switch 48) and a DC power supply circuit. 2a is connected to the low potential side bus.

  The outer coil load circuit 30 is also a series resonance circuit composed of the outer coil 33 and the resonance capacitor 34. The output point of the outer coil inverter circuit 46 (the connection point of the upper switch 52 and the lower switch 53) and the DC power supply circuit 2b. Connected to the low potential side bus.

  The current flowing through the inner coil load circuit 29 is detected by the inner coil current detection circuit 57, and the current flowing through the outer coil load circuit 30 is detected by the outer coil current detection circuit 58.

  The control circuit 36 controls the entire induction heating cooker, has a control timer 36a therein, displays an operating state on the display unit 38 in response to an input instruction from the operation input means 37, and an input current detection circuit. 6a, 6b, input voltage detection circuits 59a, 59b, inner coil current detection circuit 57, and outer coil current detection circuit 58, while taking in the detected values, control inner coil inverter drive circuit 60 and outer coil inverter drive circuit 61. Adjust the heating output.

  The drive signals output to the inner coil inverter circuit 45 and the outer coil inverter circuit 46 have a drive frequency higher than the resonance frequency of the inner coil load circuit 29 and the outer coil load circuit 30, and the current flowing through the load circuit is It is controlled so as to flow with a delayed phase compared to the voltage applied to the load circuit.

  Further, when high-frequency power is simultaneously output to the inner coil load circuit 29 and the outer coil load circuit 30, the drive signals output from the inner coil inverter drive circuit 60 and the outer coil inverter drive circuit 61 have the same frequency. At the same time, the heating power is adjusted by controlling the energization ratio of the upper switch and the lower switch while synchronizing so that the high-frequency current flowing in the inner coil 31 and the high-frequency current flowing in the outer coil 33 flow in the same circumferential direction.

  The operation input means 37 has a stew key 37a. When the stew key 37a is operated, the control circuit 36 controls the drive circuits 60 and 61 to output the high-frequency power to the inner coil load circuit 29 and the outer coil load circuit 30 at the same time while periodically fluctuating.

  FIG. 10 is a time chart showing fluctuation states of the set power of the inner coil inverter circuit 45 and the outer coil inverter circuit 46. In this way, the inner coil inverter circuit 45 and the outer coil inverter circuit 46 are driven simultaneously, and the electric power input to the inverter circuits 45 and 46 fluctuates periodically.

  As shown in the figure, in this embodiment, the set power input to the inner coil inverter circuit 45 and the set power input to the outer coil inverter circuit 46 are P11 (= 500 W) and P21 (= 200 W), respectively. The T1 period to be set and the T2 period to set P12 (= 100 W) and P22 (= 300 W) are alternately repeated.

  By doing this, the heating state of the pan bottom center heated by the high frequency current flowing in the inner coil 31 and the pan bottom outer periphery heated by the high frequency current flowing in the outer coil 33 is changed, and the cooking object in the pan is changed. The boiling state is changed and the food is stirred.

  Here, the set power P22 input to the outer coil inverter circuit 46 serving as the heating power for the pan outer peripheral portion is made smaller than the set power P11 input to the inner coil inverter circuit 45 serving as the heating power for the pan bottom center portion. , To suppress the splash of splashing when boiling bubbles generated near the wall of the pot, and to suppress the splashing of the food to be cooked around the pot.

  In the example of FIG. 10, the maximum value of the set power input to the outer coil inverter circuit 46 from the maximum value of the set power input to the inner coil inverter circuit 45 (P11 = 500 W) (P22 = 300W) is a small value.

  FIG. 11 is a timing chart of drive signals output from the inner coil inverter drive circuit 60 and the outer coil inverter drive circuit 61 when the inner coil inverter circuit 45 and the outer coil inverter circuit 46 are driven simultaneously. Since the inner coil 31 and the outer coil 33 are magnetically coupled, the high-frequency current flowing in the inner coil and the high-frequency current flowing in the outer coil are made the same in driving frequency so that the frequencies are equal, and the flowing direction is the same. The drive phase is also adjusted so that

  Further, the conduction time ratio of the upper switch 47 and the lower switch 48 is adjusted in order to control the input power to the inner coil inverter circuit 45, and the upper switch 52 to control the input power to the outer coil inverter circuit 46. And the conduction time ratio of the lower switch 53 is adjusted.

  The conduction time ratio is the ratio of the conduction time of the upper switch to the whole conduction time of the upper switch and the lower switch (inner coil upper switch conduction time ratio = T1a / (T1a + T1b), outer coil upper switch conduction time ratio. = T2a / (T2a + T2b) is adjusted within a range of 0 to 50%.

  12 and 13 are flowcharts of the inner and outer coil fluctuation heating control processing of the induction heating cooker according to the third embodiment. First, in step S101 of FIG. 12, when the inner and outer coil fluctuation heating is instructed by the stew key 37a of the operation input means 37, the inner coil inverter drive circuit 60 and the outer coil inverter drive circuit 61 are controlled, and FIG. 11 is output to the upper and lower switches 47 and 48 of the inverter circuit 45 for the inner coil and the upper and lower switches 52 and 53 of the inverter circuit 46 for the outer coil, and the inner coil load circuit 29 and the outer coil load circuit are output. Application of a high frequency voltage is started at 30.

  After the application of the high frequency voltage is started, the counter of the timer 36a is cleared and started (step S102), and the input current detection circuit 6a, the input voltage detection circuit 59a, and the inner coil current detection circuit 57 of the inverter circuit 45 for the inner coil are activated. Each current and voltage is detected by using (Step S103).

  Next, it is determined whether or not the inner coil current is excessive (step S104). As a result, when the inner coil current is excessive (step S104: Yes), the process proceeds to step S107 in order to suppress the inner coil current. The process of step S107 will be described later.

  When the inner coil current is not excessive (step S104: No), the input power is obtained from the detected input current and input voltage of the inner coil inverter circuit 45 and compared with the set power P11 of the inner coil inverter circuit in the T1 period ( In step S105), when the input power is smaller, the conduction time ratio of the upper switch 47 of the inner coil inverter circuit 45 is increased in order to increase the input power (step S106), and the process proceeds to step S108. Conversely, if the input power is greater than the set input power P11, the process proceeds to step S107 to reduce the input power. If the input power is equal to the set input power P11, the process proceeds to step S108.

  In step S107, the conduction time ratio of the upper switch 47 of the internal coil inverter circuit 45 is reduced (step S107), and the process proceeds to step S108.

  In step S108, the current and voltage are detected using the input current detection circuit 6b, the input voltage detection circuit 59b, and the outer coil current detection circuit 58 of the inverter circuit 46 for the outer coil. Further, in step S109, the outer coil current is detected. Judge whether it is excessive.

  As a result, when the outer coil current is excessive (step S109: Yes), the process proceeds to step S112 in order to suppress the outer coil current. The process of step S112 will be described later.

  If the outer coil current is not excessive (step S109: No), the input power is obtained from the detected input current / input voltage of the outer coil inverter circuit 46 and compared with the set power P21 of the outer coil inverter circuit in the T1 period ( Step S110). As a result, when the input power is smaller, the conduction time ratio of the upper switch 52 of the outer coil inverter circuit 46 is increased in order to increase the input power (step S111). Conversely, if the input power is greater than the set input power P21, the process proceeds to step S112 to reduce the input power. If the input power is equal to the set power P21, the process proceeds to step S113.

  In step S112, the conduction time ratio of the upper switch 52 of the outer coil inverter circuit 46 is reduced (step S112), and the process proceeds to step S113. If the value of the timer counter has not reached the predetermined time T1, the control returns to step S103 to continue control to set the input power to the inner coil inverter circuit to P11 and the input power to the outer coil inverter circuit to P21. To do.

  If the timer counter has reached the predetermined time T1 in step S113, the process proceeds to step S114 in FIG. 13, where the set power input to the inner coil inverter circuit is input to P12 and input to the outer coil inverter circuit. The set power to be changed is changed to P22, and the counter of the timer 36a is cleared and restarted.

  Then, the current and voltage are detected using the input current detection circuit 6a, the input voltage detection circuit 59a, and the inner coil current detection circuit 57 of the inverter circuit 45 for the inner coil (step S115), and the inner coil current is excessive. Is determined (step S116).

  As a result, when the inner coil current is excessive (step S116: Yes), the process proceeds to step S119 in order to suppress the inner coil current. The processing after step S119 will be described later. When the inner coil current is not excessive (step S116: No), the input power is obtained from the detected input current / input voltage of the inner coil inverter circuit 45 and compared with the set power P12 of the inner coil inverter circuit in the period T2. (Step S117).

  As a result, when the input power is smaller, the conduction time ratio of the upper switch 47 of the inner coil inverter circuit 45 is increased in order to increase the input power (step S118), and the process proceeds to step S120. Conversely, if the input power is greater than the set power P12, the process proceeds to step S119 to reduce the input power. If the input power is equal to the set power P12, the process proceeds directly to step S120.

  In step S119, the conduction time ratio of the upper switch 47 of the inner coil inverter circuit 45 is decreased, and the process proceeds to step S120.

  In step S120, the current and voltage are detected using the input current detection circuit 6b, the input voltage detection circuit 59b, and the outer coil current detection circuit 58 of the inverter circuit 46 for the outer coil. In step S121, the outer coil current is excessive. Judge whether there is. As a result, when the outer coil current is excessive (step S121: Yes), the process proceeds to step S124 in order to suppress the outer coil current.

  When the outer coil current is not excessive (step S121: No), the input power is obtained from the detected input current / input voltage of the outer coil inverter circuit 46 and compared with the set power P22 of the outer coil inverter circuit in the period T2. If the input power is smaller (step S122), the conduction time ratio of the upper switch 52 of the outer coil inverter circuit 46 is increased in order to increase the input power (step S123), and the process proceeds to step S125.

  If the input power is equal to the set power P22, the process proceeds directly to step S125. Conversely, if the input power is greater than the set power P22, the process proceeds to step S124 in order to decrease the input power.

  In step S124, the conduction time ratio of the upper switch 52 of the outer coil inverter circuit 46 is decreased, and the process proceeds to step S125. In step S125, the timer 36a is checked, and if the value of the timer counter has not reached the predetermined time T2, the process returns to step S115, and the input power to the inner coil inverter circuit 45 is set to P12, and the outer coil inverter circuit. The control to set the input power to 46 to P22 is continued.

  If the value of the timer counter has reached the predetermined time T2, it is determined whether or not a heating stop instruction is input from the operation input means 37 (step S126). If there is no heating stop instruction (step S126: No), FIG. Returning to step S102 of FIG. 12, the inner and outer coil fluctuation heating control processing is continued.

  When there is a heating stop instruction (S126: Yes), the drive signal output from the inner coil inverter drive circuit 60 and the outer coil inverter drive circuit 61 is stopped, and the high frequency current to the inner coil 31 and the outer coil 33 is stopped. Is stopped (step S127), the count of the timer 36a is stopped (step S128), and the inner and outer coil fluctuation heating control processing is terminated.

  As described above, in the induction heating cooker according to the third embodiment of the present invention, high-frequency current is simultaneously supplied to the inner coil 31 and the outer coil 33, and the input power (P11) to the inner coil inverter circuit 45 is the outer coil. A state (T1 period) larger than the input power (P21) to the inverter circuit 46 for power and a state where the input power (P22) to the inverter circuit 46 for the outer coil is larger than the input power (P12) to the inverter circuit 45 for the inner coil (T2 period) is repeated periodically.

  As a result, the cooking object can be stirred by alternately boiling at the center portion and the outer peripheral portion of the pan, and the maximum input power (P22) to the outer coil inverter circuit 46 is supplied to the inner coil inverter circuit 45. Compared with the case where the maximum input power to the outer coil inverter circuit 46 is controlled to be equal to the maximum input power to the inner coil inverter circuit 45 by making the value smaller than the maximum input power (P11), the pan wall It is possible to suppress the occurrence of splashing by blowing off the boiled bubbles generated at the outer peripheral portion close to, and to prevent the top plate and the like around the pan from becoming dirty due to splashing outside the pan wall.

  In addition, when providing an intermediate coil other than an inner coil and an outer coil, you may combine with the structure which energizes some coils in the different time slot | zone of Embodiment 1. FIG.

Embodiment 4 FIG.
Also in the induction heating cooker according to the third embodiment of the present invention, as described in the second embodiment, the heating density at the outer peripheral portion of the pan near the pan wall is smaller than the heating density at the center portion of the pan far from the pan wall. By doing so, it is possible to further suppress splashing of the splashes outside the pan. The induction heating cooker according to Embodiment 4 of the present invention has such characteristics. Since the induction heating cooker according to the fourth embodiment of the present invention is the same as the induction heating cooker according to the third embodiment except for the heating coil portion, detailed description of the components will be omitted.

  FIG. 14 is a time chart of the set power input to the inner coil inverter circuit 45 and the set power input to the outer coil inverter circuit 46 of the induction heating cooker according to the fourth embodiment of the present invention. Similarly to the second embodiment, the setting power input to the inner coil inverter circuit 45 is larger per coil area than the setting power input to the outer coil inverter circuit 46 (P13 / S1> P23 / S2), and The setting power input to the coil inverter circuit 46 is controlled so as to alternately repeat a state (P24 / S2> P14 / S1) larger than the setting power input to the inner coil inverter circuit 45 for each coil area, Stir the food to be cooked alternately at the center and the outer periphery of the pan.

  At that time, the maximum heating power P24 to the outer coil inverter circuit 46 is set lower than the heating power at the bottom of the pan relative to the input power P13 in the high frequency power output state to the inner coil inverter circuit 45 (P24 / S2 <P13). / S1).

  The heating coil is the same as that shown in FIG. 7 of the second embodiment. The coil area of the inner coil 31 (the area of the heating coil projected perpendicularly to the bottom of the pan) is S1, and the coil area of the outer coil 33 is S2. To do.

  In addition, when providing an intermediate coil other than an inner coil and an outer coil, you may combine with the structure which energizes some coils in the different time slot | zone of Embodiment 1, and outputs according to the area of each coil. Should be set.

Embodiment 5 FIG.
FIG. 15 is a circuit diagram of an induction heating cooker according to the fifth embodiment of the present invention. In the figure, the same or corresponding parts as those in FIG. 1 of the first embodiment or FIG.

  In FIG. 15, the DC power supply circuit 2 converts the power supplied from the commercial AC power supply 1 into DC power and supplies it to the inverter circuit 62. The inverter circuit 62 includes two switching elements (the upper switch 63 on the high potential side switching element and the lower switch 64 on the low potential side switching element) connected in series between the DC buses of the DC power supply circuit 2, Each of the switching elements includes a diode (an upper diode 65 of a high potential side antiparallel diode and a lower diode 66 of a low potential side antiparallel diode) connected in antiparallel, and the connection between the upper switch 63 and the lower switch 64. The point is the output point.

  A snubber capacitor 67 is connected to the lower switch 64 in parallel to delay the fluctuation of the output voltage when the upper switch 63 and the lower switch 64 are turned off, thereby reducing the loss of the switching element. Further, the upper switch 63 and the lower switch 64 of the inverter circuit 62 are alternately turned on and off by a drive signal output from the inverter drive circuit 68. The output of the inverter circuit 62 is connected to the inner coil load circuit 29 or the outer coil load circuit 30 by a load circuit switching relay 69, and the current is detected by the output current detection circuit 35.

  Then, the induction heating cooking appliance by Embodiment 5 of this invention is demonstrated. FIG. 16 is a front view of a heating coil of the induction heating cooker according to the fifth embodiment. FIG. 17 is a timing chart of the set power input to the inverter circuit 62 in an inner / outer coil alternate output state in which a high-frequency current is alternately passed through the inner coil and the outer coil.

  As shown in FIGS. 16 and 17, in the induction heating cooker according to the fifth embodiment of the present invention, when stewed cooking is performed, the inner coil 31a and the outer coil 33a are switched to flow a high-frequency current, and the first A state in which a high-frequency current is passed through the inner coil 31a having a large second coil area (S1a) from a set power P2a in a state in which a high-frequency current is passed through the outer coil 33a having a small coil area (S2a) (T2 period) The set power P1a is increased.

  FIG. 18 is a flowchart of the inner / outer coil alternate output control process of the induction heating cooker according to the fifth embodiment of the present invention. First, when there is an instruction input from the operation input means 37 such as a simmer key 37 a for alternately passing a high-frequency current to the inner and outer coils, the control circuit 36 controls the load circuit switching relay 69 to connect the inner coil load circuit 29 to the inverter circuit 62. Connected to the output (step S201), the counter of the timer 36a is cleared and started (step S202), and output of the drive signal from the inverter drive circuit 62 is started (step S203).

  Next, the current and voltage are detected using the input current detection circuit 6, the input voltage detection circuit 59, and the output current detection circuit 35 of the inverter circuit 62 (step S204), and it is determined whether or not the output current is excessive. (Step S205). When the output current is excessive (step S205: Yes), the process proceeds to step S208 to suppress the output current. The processing after S208 will be described later.

  When the output current is not excessive (step S205: No), the input power is obtained from the detected input current / input voltage of the inverter circuit 62 and compared with the set power P1a of the inverter circuit 62 in the T1 period (step S206). If this is smaller, the conduction time ratio of the upper switch 63 of the inverter circuit 62 is increased to increase the input power (step S207), and the process proceeds to step S209. If the input power and the set power P1a are equal, the process proceeds directly to step S209. Conversely, if the input power is greater than the set power P1a, the process proceeds to step S208 to reduce the input power.

  In step S208, the conduction time ratio of the upper switch 63 of the inverter circuit 62 is decreased, and the process proceeds to step S209.

  In step S209, it is confirmed whether or not the counter value of the timer 36a has reached the predetermined time T1, and if the counter value has not reached the predetermined time T1 (step S209: No), the process returns to step S204. In the state where the output of the inverter circuit 62 is connected to the inner coil load circuit 29, the control for setting the input power to P1a is continued.

  If the value of the timer counter has reached the predetermined time T1 in step S209, the drive signal output from the inverter circuit drive circuit 68 is stopped (step S210), and the load circuit switching relay 69 is controlled to control the inverter circuit 62. Are connected to the outer coil load circuit 30 (step S211).

  Then, the counter of the timer 36a is cleared and restarted (step S212), and output of the drive signal from the inverter drive circuit 62 is started again (step S213). Subsequently, the current and voltage are detected using the input current detection circuit 6, the input voltage detection circuit 59, and the output current detection circuit 35 of the inverter circuit 62 (step S214), and whether or not the output current is excessive is determined. Judgment is made (step S215).

  When the output current is excessive (step S215: Yes), the process proceeds to step S218 to suppress the output current. The processing after step S218 will be described later.

  If the output current is not excessive (step S215: No), the input power is obtained from the detected input current / input voltage of the inverter circuit 62 and compared with the set power P2a of the inverter circuit 62 in the T2 period (step S216).

  As a result, when the input power is smaller, the conduction time ratio of the upper switch 63 of the inverter circuit 62 is increased in order to increase the input power (step S217), and the process proceeds to step S219. If the input power is equal to the set power P2a, the process proceeds to step S219. Conversely, if the input power is greater than the set input power P2a, the process proceeds to step S218 to decrease the input power.

  In step S218, the conduction time ratio of the upper switch 63 of the inverter circuit 62 is decreased, and the process proceeds to step S219. In step S219, it is checked whether the counter value of the timer 36a has reached the predetermined time T2 (step S219). If the counter value has not passed the predetermined time T2 (step S219: No), step S214 is performed. Then, the control for changing the input power to P2a is continued in a state where the output of the inverter circuit 62 is connected to the outer coil load circuit 30.

  If the counter value has reached the predetermined time T2 in step S219, the drive signal output from the inverter circuit drive circuit 68 is stopped (step S220), and whether or not a heating stop instruction is input from the operation input means 37 is determined. If it judges (step S221) and there is no instruction | indication of a heating stop, it will return to step S201 and will continue internal / external coil alternate output control processing. If there is an instruction to stop heating, the timer 36a stops counting (step S222), and the inner / outer coil alternate output control process ends.

  As described above, according to the induction heating cooker of the fifth embodiment of the present invention, when stewed cooking is performed, the convection state of the object to be cooked is changed and stirred by switching the heating coil through which high-frequency current flows. The temperature of the cooking object can be changed by changing the heating amount to the whole pan, and the soup can be simmered so that the soup soaks into the cooking object.

  In addition, the higher the heating density, the more intense the bubbles are generated, and the higher the bubbles are blown, the more the droplets are scattered, but when the heating amount is changed, the coil with a large coil area is applied when a large heating amount is applied. Is controlled so that the difference in heating density is suppressed and the generation of the bubbles of boiling is leveled, so that splashing of the splash around the pan can be suppressed.

  FIG. 16 shows a configuration in which the second coil area of the inner coil is larger than the first coil area of the outer coil. However, as shown in FIG. 19, the first coil area of the outer coil is larger than the inner coil. It is also possible to make it larger than the second coil area. In this case, as shown in the timing chart of FIG. 20, the set power input to the inverter circuit 62 is switched in the inner and outer coil alternate output states.

  By doing so, since the second coil area (S1b) of the inner coil 31b is smaller than the first coil area (S2b) of the outer coil 33b, the set power P1b when the inner coil is energized is set as the set power when the outer coil is energized. By setting it to a state smaller than P2b, the difference in heating density can be suppressed, the generation of boiling bubbles can be leveled, and the splashing of the splash around the pan can be reduced.

Embodiment 6 FIG.
Then, the induction heating cooking appliance of Embodiment 6 of this invention is demonstrated. FIG. 21 is a circuit diagram of an induction heating cooker according to the sixth embodiment of the present invention. In the figure, the same or corresponding parts as those in FIG. 15 of the fifth embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the figure, the heating coil includes an inner coil 31 connected to the output of the inverter circuit 62 and an outer coil 33c connected in series to the outer periphery thereof. The series circuit of the inner coil 31 and the outer coil 33c constitutes a series resonance inner / outer coil load circuit with the resonance capacitor 34c, and the inner coil 31 constitutes the resonance capacitor 32 and the inner coil load circuit.

  Then, the load switching relay 70 connects the internal / external coil load circuit or the internal coil load circuit between the output of the inverter circuit 62 and the DC low potential side bus.

  FIG. 22 is a flowchart of an inner / outer coil low output control process of the induction heating cooker according to the sixth embodiment of the present invention. In step S301, when there is an instruction input from the operation input means 37 such as the stew key 37a, the control circuit 36 controls the load circuit switching relay 70 to connect the internal / external coil load circuit to the DC low potential side bus, and the timer 36a The counter is cleared and started (step S302), and the drive signal output from the inverter drive circuit 62 is started (step S303).

  Next, the current and voltage are detected using the input current detection circuit 6, the input voltage detection circuit 59, and the output current detection circuit 35 of the inverter circuit 62 (step S304), and it is determined whether or not the output current is excessive. (Step S305). When the output current is excessive (step S305: Yes), the process proceeds to step S308 to suppress the output current. The processing after step S308 will be described later.

  When the output current is not excessive (step S305: No), the process proceeds to step S306, the input power is obtained from the detected input current / input voltage of the inverter circuit 62, and is compared with the set power. As a result, when the input power is smaller, the conduction time ratio of the upper switch 63 of the inverter circuit 62 is increased to increase the input power (step S307), and the process proceeds to step S309.

  If the input power is equal to the set power, the process proceeds to step S309. If the input power is greater than the set power, the process proceeds to step S308 to decrease the input power.

  In step S308, the conduction time ratio of the upper switch 63 of the inverter circuit 62 is decreased, and the process proceeds to step S309. In step S309, it is confirmed whether or not the counter value of the timer 36a has passed the predetermined time T1, and if the counter value has not reached the predetermined time T1 (step S309: No), the process returns to step S304 and returns Control of input power is continued in a state where the output of the inverter circuit 62 is applied to the coil load circuit.

  If the timer counter has reached the predetermined time T1 in step S309, output of the drive signal from the inverter circuit drive circuit 68 is stopped (step S310), the load circuit switching relay 70 is controlled, and the inner coil load circuit is connected to the direct current. Connected to the low potential side bus (step S311), the counter of the timer 36a is cleared and restarted (step S312), and output of the drive signal from the inverter drive circuit 62 is started again (step S313).

  Then, the current and voltage are detected using the input current detection circuit 6, the input voltage detection circuit 59, and the output current detection circuit 35 of the inverter circuit 62 (step S314), and it is determined whether or not the output current is excessive. (Step S315). When the output current is excessive (step S315: Yes), the process proceeds to step S318 to suppress the output current.

  If the output current is not excessive (step S315: No), the input power is obtained from the detected input current / input voltage of the inverter circuit 62, and the process proceeds to step S316 to be compared with the set power of the inverter circuit 62 in the period T2. To do.

  As a result, when the input power is smaller, the conduction time ratio of the upper switch 63 of the inverter circuit 62 is increased to increase the input power (step S317), and the process proceeds to step S319. If the input power is equal to the set power, the process proceeds directly to step S319. Conversely, if the input power is greater than the set power, the process proceeds to step S318 to reduce the input power.

  In step S318, the conduction time ratio of the upper switch 63 of the inverter circuit 62 is decreased, and the process proceeds to step S319. In step S319, it is confirmed whether or not the counter value of the timer 36a has passed the predetermined time T2. If the counter value has not reached the predetermined time T2 (step S319: No), the process returns to step S314 and returns to the internal state. Control of input power is continued in a state where the output of the inverter circuit 62 is applied to the coil load circuit.

  When the counter value has reached the predetermined time T2 (step S319: Yes), the drive signal output from the inverter circuit drive circuit 68 is stopped (step S320), and a heating stop instruction is issued from the operation input means 37. It is determined whether or not there is an input (step S321), and if there is no instruction to stop heating, the process returns to step S301 to continue the inner / outer coil low output control process. If there is a heating stop instruction, the timer 36a stops counting (step S322), and the inner / outer coil low output control process is terminated.

  In the induction heating cooker according to the sixth embodiment of the present invention, when cooking is performed at a constant low output in the process (first time zone) until the timer counter reaches T1, the inner coil and the outer coil are used. Simultaneously energize and heat the whole pan bottom to warm the whole cooked food, then (second time zone), energize only the inner coil periodically or intermittently to concentrate the center of the pan Heat and boil or cause convection to stir the food, and the point where the bubbles generated by boiling bounce and splash of the food to be cooked is the center of the pot away from the pot wall. It is possible to reduce the contamination of the top plate of the induction heating cooker by suppressing the splashing of the food to be cooked around.

  Based on the configuration disclosed in the first to fifth embodiments, instead of the process of energizing the inner coil and the outer coil at the same time in the process (first time zone) until the timer counter reaches T1, the inner counter It can be easily understood that a process of repeating a cycle in which the coil and the outer coil are energized at different times is repeated. Even if it is such a structure, an effect is substantially the same, and does not deviate from the meaning of this invention.

  Furthermore, instead of using a timer counter to detect the passage of the first time zone or the second time zone, a thermistor or infrared sensor that measures the temperature near the outer coil or the temperature of the pan bottom against the outer coil Measure the temperature by arranging temperature detection means such as, and energize the inner coil and the outer coil at the same time or in time division until the predetermined upper limit temperature is reached. Only the inner coil may be energized intermittently until the temperature in the vicinity of the coil or the temperature of the bottom of the pan that opposes the outer coil falls to a predetermined lower limit temperature.

  The present invention is particularly useful when applied to an induction heating cooker such as an IH cooking heater.

It is a circuit diagram of the induction heating cooking appliance in Embodiment 1 of this invention. It is a time chart of the setting electric power of the internal / external coil alternate output state of Embodiment 1 of this invention. It is a timing chart in the case of outputting high frequency electric power to the inner coil load circuit of Embodiment 1 of this invention. It is a timing chart in the case of outputting high frequency electric power to the outer coil load circuit of Embodiment 1 of this invention. It is a conceptual diagram which shows the mode of the bubble of the to-be-cooked thing and the state of the splash which generate | occur | produce in the magnetic flux of an inner and outer coil, and a pan. It is a flowchart of the internal / external coil alternate output control process of Embodiment 1 of this invention. It is a front view of the heating coil of the induction heating cooking appliance of Embodiment 2 of this invention. It is a time chart of the setting electric power of both the internal and external coil load circuits of Embodiment 2 of this invention. It is a circuit diagram of the induction heating cooking appliance of Embodiment 3 of this invention. It is a time chart of the setting electric power of each inverter circuit of Embodiment 3 of this invention. It is a timing chart of each inverter drive circuit of the inner coil and outer coil of Embodiment 3 of this invention. It is a flowchart of the inner and outer coil fluctuation | variation heating control processing of this Embodiment 3. It is a flowchart of the inner and outer coil fluctuation | variation heating control processing of this Embodiment 3. It is a time chart of the setting electric power of each inverter circuit of the inner coil of this Embodiment 4, and an outer coil. It is a circuit diagram of the induction heating cooking appliance of Embodiment 5 of this invention. It is a front view of the heating coil of the induction heating cooking appliance of this Embodiment 5. It is a timing chart in the inside-and-outside coil alternate output state of this Embodiment 5. It is a flowchart of the internal / external coil alternate output control process of Embodiment 5 of this invention. It is a front view of the heating coil by another structural example of the induction heating cooking appliance of this Embodiment 5. It is a timing chart by another structural example of the induction heating cooking appliance of this Embodiment 5. It is a circuit diagram of the induction heating cooking appliance of Embodiment 6 of this invention. It is a flowchart of the internal / external coil low output control process of Embodiment 6 of this invention.

1 Commercial AC power supply,
2 DC power circuit,
6 Input current detection circuit,
7 Inverter circuit,
31 inner coil,
33 Outer coil,
35 output current detection circuit,
36 Control circuit.

Claims (6)

A DC power supply circuit that rectifies AC power and converts it into DC power;
An inverter circuit that converts DC power output from the DC power supply circuit into high-frequency power;
Driven by the high frequency power converted by this inverter circuit, a heating coil having an inner coil that heats the center of the installed pan, and an outer coil that heats the outer periphery of the pan,
An operation key that is operated when cooking to arouse convection in the pan and stir the ingredients by the convection, and
When the operation key is operated, the inverter circuit is controlled, and the high frequency power output to the inner coil is the heating density obtained by dividing the high frequency power output to the outer coil by the area of the outer coil. And an induction heating cooker characterized by comprising control means for lowering the heating density divided by the area.   The induction heating cooker according to claim 1, wherein the control means repeats a cycle in which high-frequency power output to the inner coil and high-frequency power output to the outer coil are performed in different time zones.   The induction heating cooker according to claim 1, wherein the control unit superimposes an output period of high-frequency power to the inner coil and an output period of high-frequency power to the outer coil.   The control means outputs high frequency power to the inner coil and the outer coil in a first time zone, and applies high frequency power only to the inner coil in a second time zone after the first time zone has elapsed. The induction heating cooker according to claim 1, wherein the inverter circuit is controlled so as to output and repeat the first time zone and the second time zone.   The said control means repeats the cycle which performs the output of the high frequency electric power to the said inner coil, and the output of the high frequency electric power to the said outer coil in a different time slot | zone in the said 1st time slot | zone. The induction heating cooker described in 1.   5. The induction according to claim 4, wherein the control unit superimposes an output period of high-frequency power to the inner coil and an output period of high-frequency power to the outer coil in the first time zone. Cooking cooker.

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