JP2013206542A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating cooker capable of reducing noise and power loss at low power supply, and suppressing generation of rasping sounds from a heated object, in the case that one heated object is heated by a plurality of heating coils.SOLUTION: By stopping supply of a high-frequency current to some of heating coils among a plurality of heating coils (a first heating coil 81, a second heating coil 82, a third heating coil 83, and a fourth heating coil 84) provided immediately under a heated object, the number of heating coils to which the high-frequency current is supplied is reduced, and thereby, a value of a power to be supplied to the heated object can be reduced. An inverter circuit 43 supplying the high-frequency current to the heating coils maintains a constant value of the high-frequency current to perform a switching operation so as not to generate large noise or power loss. In addition, because the value of the power to be supplied to the heated object always constant even over time, generation of rasping sounds from the heated object can be suppressed.

Description

  The present invention relates to an induction heating cooker that heats an object to be heated such as a pan using a plurality of heating coils.

  Conventionally, in this type of induction heating cooker, there is a type in which one heating region is configured by a plurality of heating coils arranged in a plane, and each heating coil is sequentially energized with a time difference (for example, Patent Document 1). reference). In this induction heating cooker, since a specific place is not heated by sequentially changing the coil to be energized, the temperature distribution of the object to be heated can be averaged and a donut-shaped heating unit can be prevented from being generated. Patent Document 1 discloses only a technique for uniformly heating an object to be heated, and does not disclose any technical contents related to a power control method.

  Further, in the conventional induction heating cooker, when the value of the input setting is equal to or less than a predetermined value, a heating period in which the switching means repeats the on / off operation while controlling the on time of the switching means of the inverter circuit to a predetermined constant value; In some cases, a pause period for pausing the on / off operation of the switching means after the heating period has elapsed is set, and the ratio between the length of the heating period and the pause period is controlled in accordance with the value of the input setting (for example, Patent Documents). 2).

  Even when the value of the input setting is a low value, the induction heating cooker can set the oscillation frequency of the switching means at this time to a constant value, so that noise can be reduced. Moreover, the power loss of the switching means can be reduced.

JP-A-63-291387 Japanese Patent Laid-Open No. 2-148685

  However, like the power control in the conventional induction heating cooker in Patent Document 2, the heating period in which the switching element of the inverter circuit repeats the on / off operation, and the pause in which the on / off operation of the switching element is paused after the heating period has elapsed. When the period is set and the ratio of the length of the heating period and the rest period is controlled according to the value of the input setting, the current flowing through the inverter circuit and the magnetic field generated from the heating coil during the on / off operation change abruptly. As a result, the components constituting the inverter circuit and the pan that is the object to be heated are vibrated and an unpleasant sound is generated.

  The present invention solves the above-described conventional problems, and reduces the noise and the power loss of the switching means even when the power value supplied to the object to be heated is equal to or less than a predetermined value. It is an object of the present invention to provide an induction heating cooker that does not generate harsh sounds.

In order to solve the above-mentioned conventional problems, an induction heating cooker according to the present invention includes a top plate on which an object to be heated is placed, and a plurality of parts that are disposed below the top plate and induction-heat a single object to be heated. A heating coil, an inverter circuit that supplies a high-frequency current to the plurality of heating coils, and a control unit that outputs a drive signal to the inverter circuit to control the operation of the inverter circuit, and the control unit includes a plurality of heating coils. Inverters are used to jointly control the value of the high-frequency current supplied to each and the presence / absence of supply of the high-frequency current, and simultaneously supply a high-frequency current to a plurality of heating coils to heat one object to be heated together When the electric power supplied from the power supply to the object to be heated is greater than or equal to a predetermined value, the circuit operation is controlled and supplied to each of the heating coils that are heating the object to be heated together The power value is controlled by increasing / decreasing the value of the high-frequency current, and when the power value supplied from the power source to the object to be heated is less than a predetermined value, from among a plurality of heating coils existing directly under the object to be heated A drive signal is output from the control means to the inverter circuit so as to control the power value by increasing or decreasing the number of heating coils that supply high-frequency current.

  According to the induction heating cooker of the present invention, when the power value supplied from the induction heating cooker to the object to be heated is less than a predetermined value, among the plurality of heating coils existing immediately below the object to be heated to be heated, In order not to supply a high-frequency current to any of the heating coils, the number of heating coils that supply power to the object to be heated is reduced so that all the heating coils that are directly under the object to be heated can be heated. The power value supplied to can be lowered.

  In addition, the heating coil that supplies high-frequency current can pass a high-frequency current above a certain value required for switching the switching element in the inverter circuit on and off in normal operation. The power loss at can be reduced.

  Furthermore, since the power value supplied to the object to be heated can be controlled without providing a pause period during which the on / off operation of the switching element is suspended, the current flowing in the inverter circuit and the magnetic field generated from the heating coil do not change abruptly. Therefore, generation of harsh sounds due to vibrations of circuit components and heated objects can be prevented.

The block diagram ((a) top view, (b) sectional drawing) of the induction heating cooking appliance in Embodiment 1 of this invention Inverter circuit diagram of induction heating cooker in Embodiment 1 of the present invention The figure which shows the relationship between the control system of the induction heating cooking appliance and supply electric power in Embodiment 1 of this invention. The figure which shows the number of the heating coils which energize with each electric power of the induction heating cooking appliance in Embodiment 1 of this invention. The figure which shows the place of the heating coil which supplies with electricity in each mode of the induction heating cooking appliance in Embodiment 2 of this invention The figure which shows the sequence of the heating coil which supplies with electricity the induction heating cooking appliance in Embodiment 2 of this invention. The figure which shows the number of the heating coils which the energization of the induction heating cooking appliance in Embodiment 3 of this invention energizes. The figure which shows the sequence of the heating coil which supplies with electricity the induction heating cooking appliance in Embodiment 3 of this invention. The other block diagram of the induction heating cooking appliance in this invention ((a) top view, (b) sectional drawing) Other configuration diagrams of a plurality of heating coils in the present invention

The first invention includes a top plate for placing an object to be heated, a plurality of heating coils disposed below the top plate for induction heating a single object to be heated, and a high frequency current applied to the plurality of heating coils. An inverter circuit to be supplied, and a control means for controlling the operation of the inverter circuit by outputting a drive signal to the inverter circuit, and the control means is configured to supply a value of a high-frequency current to be supplied to each of the plurality of heating coils and a supply of the high-frequency current. In addition to controlling the presence or absence in a coordinated manner, by simultaneously supplying a high-frequency current to a plurality of heating coils, the operation of the inverter circuit is controlled so that one object to be heated is jointly supplied and supplied from the power source to the object to be heated If the power value to be applied is greater than or equal to a predetermined value, the power value is controlled by increasing or decreasing the value of the high-frequency current supplied to each of the plurality of heating coils that jointly heat one object to be heated. When the power value supplied from the power source to the object to be heated is less than a predetermined value, by increasing or decreasing the number of heating coils that supply the high-frequency current from among the plurality of heating coils that exist directly under one object to be heated A drive signal is output from the control means to the inverter circuit so as to control the power value.

  Thus, when the power value supplied to the object to be heated from the induction heating cooker is less than a predetermined value, among the plurality of heating coils existing immediately under the object to be heated, some of the heating coils have a high-frequency current. In order not to supply power, the number of heating coils that supply power to the object to be heated is reduced, thereby reducing the power value supplied to the object to be heated from all the heating coils that are directly under the object to be heated. be able to.

  In addition, the heating coil that supplies high-frequency current can pass a high-frequency current above a certain value required for switching the switching element in the inverter circuit on and off in normal operation. The power loss at can be reduced.

  Furthermore, since the power value supplied to the object to be heated can be controlled without providing a pause period during which the on / off operation of the switching element is suspended, the current flowing in the inverter circuit and the magnetic field generated from the heating coil do not change abruptly. Therefore, generation of harsh sounds due to vibrations of circuit components and heated objects can be prevented.

  Furthermore, in order to coordinately control the presence or absence of the high-frequency current supplied to each of the plurality of heating coils, when the power value supplied to the object to be heated is equal to or greater than a predetermined value, all the heating coils existing directly under the object to be heated are simultaneously Further, by continuously supplying the high-frequency current, the power value supplied to the object to be heated can be increased.

  Furthermore, since a high-frequency current is simultaneously supplied to a plurality of heating coils to heat one object to be heated together, the power value to be supplied to the object to be heated per heating coil is supplied to the object to be heated. Since the power is distributed with respect to the total power value, the power value supplied from each heating coil to the object to be heated can be lowered. Therefore, by using a circuit component with a low rating of the circuit component or a heating coil with a small number of wires, the component size can be reduced or the cost can be reduced.

  In a second aspect of the invention, in particular, in the induction heating cooker of the first aspect of the invention, the control means includes a heating coil for supplying a high-frequency current and a high-frequency current when the power value supplied from the power source to the object to be heated is less than a predetermined value. A drive signal is output from the control means to the inverter circuit so that the heating coil that does not supply the power is switched over in a certain period.

  As a result, the average value of the power value supplied to the heated object from any heating coil immediately below the heated object is the same, so that the heated object does not have temperature unevenness and is heated uniformly. Can do.

  According to a third aspect of the present invention, in particular, in the induction heating cooker of the first or second aspect, the control means is a heating coil that does not supply a high-frequency current when the power value supplied from the power source to the object to be heated is less than a predetermined value. A drive signal is output from the control means to the inverter circuit so as to change the number of.

  Accordingly, by changing the ratio of the period in which the number of heating coils supplying high-frequency current in a certain period is large and the period in which the number of heating coils is small, even when a low power value is supplied, it is supplied to the object to be heated. The power can be continuously changed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a configuration diagram of an induction heating cooker according to a first embodiment of the present invention, FIG. 1 (a) is a top view of the induction heating cooker, and FIG. 1 (b) is a diagram of FIG. 1 (a). It is sectional drawing in line segment LL '.

  Moreover, FIG. 2 shows the inverter circuit diagram of the induction heating cooking appliance in the 1st Embodiment of this invention.

  First, the structure of the induction heating cooker in Embodiment 1 of this invention is demonstrated using FIG. Below the top plate 13 on which an object to be heated such as a pan is placed, there are four heating coils having the same shape (first heating coil 81, second heating coil 82, third heating coil 83, and fourth heating coil. A heating coil 84) is arranged in alignment with the inside of the first heating region 11 indicating a region for heating the object to be heated.

  In addition, an inverter circuit for supplying a high-frequency current to the four heating coils (first heating coil 81, second heating coil 82, third heating coil 83, and fourth heating coil 84). 43 is connected, and the operation of the inverter circuit 43 is controlled based on the drive signal output from the control means 59, so that four heating coils (first heating coil 81, second heating coil 82, third The value of the high-frequency current supplied to each of the heating coil 83 and the fourth heating coil 84) is controlled.

  A circular object to be heated placed on the top plate 13 so as to cover all four heating coils (the first heating coil 81, the second heating coil 82, the third heating coil 83, and the fourth heating coil 84). The electric power value supplied to 21 is determined by the user of the induction heating cooker setting from the operation means 14, and the control means 59 is based on the control signal output from the operation means 14 to the control means 59. The value of the drive signal to be output is changed.

  In the induction heating cooker shown in FIG. 1, there are two heating regions, and four heating coils are also arranged inside the second heating region 12. The elliptical object to be heated 22 placed in the second heating area 12 covers only the two heating coils in front of the four heating coils disposed inside the second heating area 12. As with the first heating region 11, heating is possible by setting the power value from the operating means 14.

  FIG. 2 is an inverter circuit diagram of the induction heating cooker according to the first embodiment of the present invention. In FIG. 2, in addition to the first switching element 51 and the second switching element 53 which are switching means constituting the inverter circuit 43 of the power supply means 15, four heating coils (first heating coil 81, second Since the heating coil 82, the third heating coil 83, the fourth heating coil 84), the power source, and the like are also illustrated, the electric flow from when the power source is supplied to the heating coil can be understood.

In FIG. 2, a power source supplied from an outlet or the like is an AC power source 41, and a rectifying means 42 such as a diode bridge is connected to convert the AC power source 41 into a DC power source.

  On the output side of the rectifying means 42, a first switching element 51 connected in parallel with a first reverse conducting diode 52 and a second switching element 53 connected in parallel with a second reverse conducting diode 54 are electrically connected. Those connected in series are connected to form an inverter circuit 43.

  A resonance circuit including a first heating coil 81 and a first resonance capacitor 56 is connected to the inverter circuit 43.

  Further, the snubber capacitor 60 is electrically connected in parallel with the second switching element 53 in order to reduce the switching loss caused by the switching operation of the first switching element 51 and the second switching element 53.

Further, it has a control means 59 for driving and controlling the first switching element 51 and the second switching element 53.
The circuit of the induction heating cooker of this Embodiment is formed by providing the inverter circuit comprised in this way in each of four heating coils.

  About the induction heating cooking appliance comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  In the induction heating cooker in the present embodiment, since four heating coils are disposed in the same heating region, usually four heating coils are used to heat one object to be heated.

  However, when the object to be heated is small with respect to the second heating region 12 as in the elliptical object to be heated 22, the high frequency current is supplied only to the two heating coils on which the elliptical object to be heated 22 is placed. By stopping the energization of the remaining two heating coils that do not contribute to the heating of the object to be heated, the conduction loss of the heating coil caused by the high-frequency current flowing in those heating coils, or the high-frequency current in the heating coil The conduction loss and switching loss of the switching element of the inverter circuit for supplying the heat can be eliminated, and an induction heating cooker with high heating efficiency can be provided.

  In addition, by stopping the supply of high-frequency current to the heating coil that does not contribute to heating, the generation of electromagnetic waves can be suppressed even if the object to be heated is small, so that adverse effects such as malfunctions to peripheral devices should not be adversely affected. Can do.

  On the other hand, if the object to be heated is a circular object to be heated 21 having a size so as to cover all four heating coils, and the electric power supplied to the circular object to be heated 21 is greater than or equal to a predetermined value, By supplying a high-frequency current to all the coils, the circular object 21 is heated at a high power value.

  This is for enlarging the heating area as much as possible by energizing all the heating coils that contribute to heating so that the heating coil can be heated uniformly.

  Further, in a general induction heating cooker, the maximum power supplied to the object to be heated from one heating region, that is, four heating coils is determined, so the maximum power of the heating coil existing in one heating region is determined. By setting the power supply so that the power divided by the number can be supplied, the responsibility for loss is evenly distributed, and the cooling design of the heating coil and inverter circuit is facilitated and the component rating is reduced and realized at a low price. But there is.

  In the induction heating cooker of the present embodiment, when the power supplied to the object to be heated is equal to or greater than a predetermined value, the adjustment of the power supplied to the object to be heated is within one cycle of the switching element of the inverter circuit that is driven at high frequency. This is done by changing the current flowing in the heating coil by changing the ratio between the on time and the off time or the operating frequency.

  As a result, power can be continuously controlled within a power supply range of a predetermined value or more. The power setting of the induction heating cooker is generally set in a discrete manner, but the heating coil terminal depends on factors such as the material and deformation of the object to be heated, the temperature characteristics, and the deviation of the placement position of the object to be heated. Since the electrical characteristics of the object to be heated appearing in various ways, it is indispensable to continuously control the current flowing in the heating coil in order to adjust the target power set value.

  When reducing the value of the power supplied to the object to be heated from the value of the maximum power, the current flowing through all the heating coils supplying power to the object to be heated is made substantially uniform from the uniformity of the object to be heated. Although it is desirable to reduce the temperature distribution, if temperature distribution does not appear significantly or uniformity is not required, select one of the heating coils that supply power to the object to be heated and flow to the heating coil. The high frequency current may be decreased.

  In the case of a resonance type inverter circuit configuration, even if the supplied power value is smaller than the maximum power value, it is generated from the switching element when the resonance frequency determined from the heating coil and the resonance capacitor is close to the operating frequency of the inverter circuit. In such a case, the total current from the switching elements of the inverter circuit connected to the four heating coils is reduced by not reducing the current flowing through all the heating coils. Thus, a decrease in heating efficiency can be suppressed.

  On the other hand, when the electric power supplied to the object to be heated is less than a predetermined value, the electric power supplied to the object to be heated is adjusted to a high frequency in some heating coils among the heating coils on which the object to be heated is mounted. This is done by controlling so that no current is supplied.

  FIG. 3 shows the relationship between the control method of the induction heating cooker and the total power value supplied to the non-heated material in the first embodiment of the present invention. When the total power value supplied to the object to be heated is equal to or greater than the predetermined value P1, the electric power supplied to the object to be heated is controlled by reducing the current flowing through the four heating coils, so power control is supplied to the object to be heated. It can be performed continuously in the range up to the maximum power Pmax that can be achieved.

  Further, when the total power value is set to be less than the predetermined value P1, the total power value supplied to the object to be heated is changed by changing the number of heating coils that supply the high-frequency current. The power value becomes discrete.

  FIG. 4 is a diagram showing the number of heating coils to be energized with each power of the induction heating cooker according to the first embodiment of the present invention. In FIG. 4, a high frequency current is supplied to the heating coil indicated by hatching.

  Table 1 is a table showing the heating coil to be energized and the power supplied to the object to be heated in the first embodiment.

  As shown in Table 1, when the power value supplied to the object to be heated is equal to or greater than a predetermined value, the high frequency current is supplied to all four heating coils as indicated by power A.

  On the other hand, when the power value supplied to the object to be heated is less than the predetermined value, the power is first supplied to the object to be heated rather than the electric power A by not supplying the electric power to the fourth heating coil 84 like the electric power B. Electric power can be lowered. At this time, unless the value of the high-frequency current supplied to the first heating coil 81, the second heating coil 82, and the third heating coil 83 is changed, the power supplied to the object to be heated in the state of power B is It becomes 3/4 of the electric power A.

  When it is desired to further reduce the power supplied to the object to be heated, the power can be controlled by stopping the high-frequency current supplied to the third heating coil 83 like the power C this time.

  As in the case where the power supplied to the object to be heated is a predetermined value or more, the power is adjusted by changing the ratio of the on time and the off time in one cycle of the switching element of the inverter circuit that is driven at high frequency. If the current flowing through the coil is changed, the electric current supplied to the object to be heated is low, so the value of the current flowing through the heating coil is small. Therefore, there are two timings at which the two switching elements are switched on and off. During the dead time period when both switching elements are turned off, the snubber capacitor is not fully charged / discharged.

  Therefore, the snubber capacitor is short-circuited at the timing when the switching element transitions from OFF to ON, and a remarkably large noise is generated, and the loss in the switching element is enormous.

  Therefore, by providing a heating coil that does not supply high-frequency current, the power supplied to the object to be heated is reduced without increasing the loss of the switching element by supplying high-frequency current to other heating coils above a certain value. be able to.

  A heating period in which the switching element of the inverter circuit repeats the on / off operation, a pause period in which the on / off operation of the switching means is paused after the heating period has elapsed, and a ratio between the length of the heating period and the pause period is set as an input setting value. If the control is performed according to the above, the current flowing through the inverter circuit and the magnetic field generated from the heating coil at the time of switching on and off are abruptly changed, and sound is generated from the circuit components and the pan, which is annoying.

  However, in the power control in the present invention, low power can be supplied without providing a pause period. Of course, this is a state in which large noise is not generated and an increase in loss in the switching element can be suppressed.

  Here, it is desirable to set the above predetermined value to the value of power at the start of the short-circuit mode of the snubber capacitor where significant noise starts to occur. However, the accuracy error of the induction heating cooker and various types of heated objects In view of this correspondence, it is desirable to set a value slightly larger than the minimum supply power immediately before noise occurs.

  However, the present invention is not limited to this, and even if it is slightly smaller than the minimum supply power at which large noise starts to occur, the same effect can be exhibited at a power setting value lower than that.

  In the control according to the second embodiment, the number of heating coils to be energized is determined when the set low power cannot be supplied even if the power is reduced to the value of the minimum supply power at which no large noise is generated. Since the electric power is controlled by changing, the electric power value that can be supplied to the object to be heated can only be discretely set in a low electric power setting state.

  However, if fine adjustment is necessary for the set power, the total power supplied to the object to be heated may be adjusted by increasing or decreasing the value of the high-frequency current supplied to the heating coil that is continuously supplied.

(Embodiment 2)
FIG. 5 is a diagram showing the location of the heating coil to be energized in each mode that changes with time in the induction heating cooker according to the second embodiment of the present invention.

  FIG. 6 is a sequence diagram of the induction heating cooker according to the second embodiment of the present invention, and shows an example of the change over time of the heating coil that supplies the high-frequency current.

  Here, in the second embodiment, only the parts different from the first embodiment will be described, and the description of the same parts as the first embodiment will be omitted.

  FIG. 5 differs from FIG. 4 in that the heating coil that supplies the high-frequency current among the heating coils on which the object to be heated is placed immediately above is changed over time.

  About the induction heating cooking appliance comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The induction heating cooker according to the second embodiment has a heating coil that does not supply power when there is a heating coil that has a low set power and is not energized with a high-frequency current even when an object to be heated is placed immediately above it. Switch over time.

  For example, in the first heating coil 81, the second heating coil 82, the third heating coil 83, and the fourth heating coil 84, the set power is the minimum in continuous heating in an operation that does not cause a significant increase in noise. When the power supply is set to a predetermined value P1, when a set value that is less than the predetermined value P1 is set by the user, first, as the heating period 1, the first heating coil 81, the second heating coil 82, the first The high frequency current is supplied to the third heating coil 83, and the high frequency current is not supplied to the fourth heating coil 84. In this heating period 1, assuming that the electrical characteristics of the objects to be heated appearing in the four heating coils are the same, the power to be heated is supplied to three-fourths of the predetermined value P1.

When the transition to the heating period 2 is made after the elapse of the heating period 1, the high-frequency current is supplied to the first heating coil 81, the second heating coil 82, and the fourth heating coil 84, and the third heating coil. In 83, the high frequency current is not supplied. In the heating period 2, as in the heating period 1, power to be heated is supplied to the object to be heated by three quarters of the predetermined value.

  By making this operation round, the amount of electric power supplied to the object to be heated from each of the four heating coils is the same in the cycle that is the period of the circuit, so the amount of heat generated from the object to be heated is evenly distributed, The heated product can be heated uniformly.

  In addition, since the duty to supply the high-frequency current by controlling the on / off control of the inverter circuit connected to each heating coil is dispersed, the temperature rise of the switching element is suppressed as compared with the case where the heating coil to be energized is not switched, It is possible to provide a quiet induction heating cooker that suppresses the number of rotations of the cooling fan 16 or the like that cools the switching element and quiets the sound generated from the cooling fan 16. Depending on conditions such as the material of the object to be heated and the set power, it is possible to stop the cooling fan 16 due to the dispersion of heat generation.

  A heating period in which the switching element of the inverter circuit repeats the on / off operation, a pause period in which the on / off operation of the switching means is paused after the heating period has elapsed, and a ratio between the length of the heating period and the pause period is set as an input setting value. When the on / off switching is performed, the magnetic field generated from the heating coil changes abruptly, and the power supplied to the object to be heated changes abruptly. When the pan vibrates, sound is generated between the contact members such as the top plate, which is annoying.

  However, in the operation according to the second embodiment, the power supplied to the heated object is always constant in the heating periods 1 to 4 even when the heating coil to be energized is switched. Is constant and the pan is less likely to vibrate.

  Therefore, it is possible to suppress the generation of harsh sounds.

  In FIG. 5, the heating coil that does not supply the high-frequency current is set as the fourth heating coil 84 → the third heating coil 83 → the second heating coil 82 → the first heating coil 81. Good.

  For example, when the supply power is set to be half of a predetermined value, control is performed so as to stop the supply of the high-frequency current to the two heating coils. The combination and order of the heating coils that are not supplied may be set in any way, and the effects of the present invention can be achieved.

(Embodiment 3)
FIG. 7 is a diagram showing the number of heating coils to be energized in the induction heating cooker according to the third embodiment of the present invention.

  FIG. 8 is a sequence diagram of the induction heating cooker according to the third embodiment of the present invention, and shows an example of the change over time of the heating coil that supplies the high-frequency current.

  Here, in the third embodiment, only the parts different from the first or second embodiment will be described, and the description of the same parts as the first or second embodiment will be omitted.

  FIG. 8 differs from FIG. 6 in that the power value supplied to the object to be heated changes over time by switching the number of heating coils that do not supply high-frequency current.

  About the induction heating cooking appliance comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  The induction heating cooker according to the third embodiment is a heating coil that does not supply power when there is a heating coil that has a low set power and is not energized with a high-frequency current even if an object to be heated is placed immediately above it. Try to switch the number over time.

  In the four heating coils (first heating coil 81, second heating coil 82, third heating coil 83, fourth heating coil 84), in the continuous heating operation in which the set power does not cause a significant increase in noise. When the minimum supply power is set to a predetermined value P1, when a set value that is less than the predetermined value P1 is set by the user, the first heating coil 81 and the second heating coil 82 are first set as the heating period 1. The high frequency current is supplied to the third heating coil 83 and the high frequency current is not supplied to the fourth heating coil 84. In this heating period 1, assuming that the electrical characteristics of the objects to be heated appearing in the four heating coils are the same, the power to be heated is supplied to three-fourths of the predetermined value P1.

  When the transition to the heating period 2 is made after the heating period 1 has elapsed, a high-frequency current is supplied to the first heating coil 81 and the second heating coil 82, and the third heating coil 83 and the fourth heating coil are supplied. No high frequency current is supplied to 84.

  In this heating period 2, the power to be heated is supplied to the quarter of the predetermined value P1.

  For example, by dividing the ratio of the heating period 1 and the heating period 2 in a certain period by half, the power to be heated is 5/8 of a predetermined value that could not be realized if the number of heating coils not supplying high-frequency current was fixed. Can be supplied to things.

  That is, by changing the number of heating coils that do not supply high-frequency current over time, arbitrarily set low power can be supplied to the object to be heated.

  In addition, since the difference in power supplied to the object to be heated from each heating coil is smaller than when the value of power is arbitrarily set by increasing the value of the high-frequency current flowing through the heating coil that is continuously energized, The object to be heated can be heated uniformly.

  As described above, in the description of the first to third embodiments of the present invention, the inverter circuit using the two switching elements is shown as being configured independently for each heating coil, but the number and the configuration of the switching elements are different. The configuration of the inverter circuit is not limited, such as a circuit configuration in which the rectifier circuit unit and the inverter unit are shared by a plurality of heating coils.

  In the first to third embodiments, the arrangement and connection method of the four heating coils and the method of supplying power are described. However, nine heating coils are arranged in 3 rows × 3 columns, or FIG. As shown in the drawing, any number of heating coils may be used as long as there are a plurality of heating coils, for example, several tens of heating coils are aligned and arranged below the top plate of the induction heating cooker. FIG. 9 is another configuration diagram of the induction heating cooker according to the present invention. FIG. 9A is a top view, and FIG. 9B is a cross-sectional view taken along line LL ′ in FIG. It is.

  Furthermore, the heating coils do not have to have the same shape, and even if different heating coils are arranged concentrically as shown in FIG. 10, the noise in the low power supply and the power loss of the switching element can be reduced. Generation | occurrence | production suppression can be implement | achieved.

Since the present invention can reduce the generation of noise and the loss of switching elements even in a low power supply area by using the induction heating method, it is not limited to home cooking appliances such as induction heating cookers, but also induction. It is effective for use in equipment that performs induction heating, such as for business use using a heating device.

DESCRIPTION OF SYMBOLS 11 1st heating area | region 12 2nd heating area | region 13 Top plate 14 Operation means 15 Power supply means 16 Cooling fan 41 AC power supply 42 Rectification means 43 Inverter circuit 56 1st resonance capacitor 59 Control means 60 Snubber capacitor 81 1st Heating coil 82 Second heating coil 83 Third heating coil 84 Fourth heating coil

Claims (3)

A top plate for placing an object to be heated, a plurality of heating coils disposed under the top plate for induction heating a single object to be heated, and an inverter circuit for supplying a high-frequency current to the plurality of heating coils And a control means for controlling the operation of the inverter circuit by outputting a drive signal to the inverter circuit, wherein the control means is configured to supply a high-frequency current value or a high-frequency current to be supplied to each of the plurality of heating coils. In addition to controlling the presence or absence in a coordinated manner, by simultaneously supplying a high-frequency current to the plurality of heating coils, the operation of the inverter circuit is controlled so as to heat one object to be heated together. When the power value supplied to the heater is greater than or equal to the predetermined value, the value of the high-frequency current supplied to each of the plurality of heating coils that are heating one object to be heated is increased or decreased. When the power value supplied from the power source to the object to be heated is less than a predetermined value, the number of heating coils that supply a high-frequency current from among the plurality of heating coils that exist directly under the object to be heated An induction heating cooker that outputs a drive signal from the control means to the inverter circuit so as to control the power value by increasing or decreasing the value. When the power value supplied from the power source to the object to be heated is less than a predetermined value, the control means switches the heating coil that supplies high-frequency current and the heating coil that does not supply high-frequency current from the control means so as to switch over a certain period. The induction heating cooker according to claim 1, wherein a drive signal is output to the inverter circuit. When the power supplied from the power source to the object to be heated is less than a predetermined value, the control means drives the inverter circuit from the control means to change the number of heating coils that do not supply high-frequency current over a certain period. The induction heating cooker according to claim 1 or 2, wherein: