JP2005268147A - Electromagnetic induction heating cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic induction heating cooker which has a prolonged life owing to the decrease in loss of a litz wire forming an induction heating coil and loss of an inverter circuit, and provides a rated heating power even when the inverter circuit is operated at a high frequency. <P>SOLUTION: The electromagnetic induction heating cooker is equipped with a resonance capacitor, a series resonance circuit to generate a resonance frequency by the resonance capacitor and an induction heating coil, an inverter circuit to supply a high frequency current, and a control calculation circuit to compare and calculate an input power and a power set value, and to control an output frequency of the inverter circuit, wherein when the cluster mode is set to be present, the resonance frequency is increased, and the output frequency range of the inverter circuit is set to be in the high output frequency range corresponding to the high resonance frequency by the control calculation circuit, and wherein when the cluster mode is set to be absent, the resonance frequency is decreased, and the output frequency range of the inverter circuit is set to be in the low output frequency range corresponding to the low resonance frequency by the control calculation circuit, whereby the output frequency of the inverter circuit is controlled corresponding to the setting. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electromagnetic induction heating cooker that uses an inverter circuit to supply a high-frequency current to an induction heating coil to heat a cooking pan by electromagnetic induction, and more particularly to a resonance frequency control technique.

  Water does not have many water molecules in it, and in many cases it is in a state called a cluster of several tens of water molecules, but when ultrasonic vibration is applied to this water, It is known that the cluster is subdivided. The water that has been made into small clusters due to the subdivision of the clusters becomes a fine and smooth state. By increasing the penetration power, the water penetrates quickly to the depths of the ingredients, pulls out the flavor, and is cooked firmly from the inside.

  FIG. 5 is an electrical connection diagram of a conventional electromagnetic induction heating cooker. In FIG. 5, a stand PL called a top plate is installed above the spiral induction heating coil HL, and an iron pan PB is placed on the top plate PL. The resonance capacitor is formed by the first capacitor C1 and the second capacitor C2, and a series resonance circuit that performs series resonance at a predetermined resonance frequency by the induction heating coil HL and the resonance capacitor is formed, and the inverter circuit When the operating frequency is controlled and a high frequency current is supplied, an induced current of the opposing pan PB flows and heating is performed by electromagnetic induction.

  On the other hand, since most of the induction heating load is an inductance component, an induction current having a phase that is 90 degrees behind that of the induction heating coil HL flows on the pan PB side. The pole appears. As a result, the magnetic poles of the same polarity are opposed to each other, an electromagnetic repulsive force is generated between them, and the bottom of the pan PB vibrates at the oscillation frequency of the induced current. This vibration is applied to the food as ultrasonic vibration. Thereby, the cluster of the water | moisture content in a foodstuff is subdivided, and a foodstuff increases the water retention power and the flavor becomes mellow. Also, with boiled foods, the sauce is well sagging and the seasoning is better.

  However, in order to promote the subdivision of the water cluster, the conventional technique promotes the subdivision of the water cluster by increasing the operation frequency from the value at which the operation frequency of the inverter circuit is normally used. However, increasing the operating frequency of the inverter circuit increases the loss of the induction heating coil HL and the inverter circuit. As a prior document disclosing the above-described technique, for example, there is Patent Document 1.

JP 2002-184564 A

  In the above-described prior art, the operation frequency of the inverter circuit of the electromagnetic induction heating cooker is increased to promote the subdivision of the water cluster. However, if the operating frequency of the inverter circuit is increased in order to realize the subdivision of the water cluster, the loss of the litz wire forming the induction heating coil and the loss of the inverter circuit are increased to shorten the life. In addition, the heating power is simply reduced to increase the operating frequency of the inverter circuit, and the rated heating power cannot be obtained.

  In order to solve the above-described problem, the first invention performs series resonance at a resonance frequency determined in advance by a resonance capacitor formed by the first capacitor and the second capacitor, and the resonance capacitor and the induction heating coil. A series resonant circuit to be formed; a rectifier circuit that rectifies and converts a commercial AC power supply into a DC voltage; an inverter circuit that supplies a high-frequency current to the induction heating coil using the DC voltage of the rectifier circuit as an input; and An input power calculation circuit for calculating the input power, and a power control difference for comparing and calculating the input power calculation signal of the input power calculation circuit and a power setting signal having a predetermined value and outputting the result as a power amplification differential amplification signal A dynamic amplification circuit; and a control arithmetic circuit that controls an output frequency of the inverter circuit in accordance with the differential amplification signal for power control. In an electromagnetic induction heating cooker in which a pan placed on a plate is heated by electromagnetic induction, a cluster mode changeover switch is provided to set whether or not a cluster mode is set to reduce the aggregation of water molecules, and the first capacitor Comprises a third capacitor and a fourth capacitor having a smaller capacity than the third capacitor, and the second capacitor comprises a fifth capacitor and a sixth capacitor having a smaller capacity than the fifth capacitor. And when the cluster mode selector switch is set to have a cluster mode, the fourth capacitor is selected as the first capacitor, the sixth capacitor is selected as the second capacitor, and the resonance frequency is increased. When the cluster mode selector switch is set to no cluster mode, the first capacitor The third capacitor is selected and the fifth capacitor is selected as the second capacitor to lower the resonance frequency, and the control arithmetic circuit is configured such that the cluster mode change switch is in a cluster mode. When set to Yes, the inverter output frequency range is set to a predetermined high output frequency range corresponding to the high resonance frequency, and when the cluster mode changeover switch is set to no cluster mode, the inverter output frequency range is set to the above range. A control arithmetic circuit that sets a predetermined low output frequency range corresponding to a low resonance frequency and controls the output frequency of the inverter within each output frequency range in accordance with the differential amplification signal for power control. It is the electromagnetic induction heating cooking appliance characterized.

  A second invention is the electromagnetic induction heating cooker according to claim 1, wherein a plurality of the induction heating coils are connected in parallel or in series.

  According to the first invention, since the presence or absence of a cluster mode for reducing the aggregation of water molecules can be selected as necessary, the operating frequency of the inverter circuit without using a cluster mode with a high usage rate in normal cooking Therefore, the loss of the litz wire forming the induction heating coil and the loss of the inverter circuit are reduced and the life is extended. In addition, in order to control the operation frequency of the inverter circuit in a high output frequency range corresponding to a high resonance frequency in the cluster mode, the impedance of the series resonance circuit is reduced even in a high region, so the inverter circuit at a high frequency. The rated thermal power can be obtained even if the is operated.

  According to the said 2nd invention, the bottom of a pan vibrates with the oscillation frequency of an induction current in several places by the some induction heating coil connected in parallel or in series. This vibration is applied to the water at a plurality of locations as an ultrasonic vibration, and since the small clusters of water are performed at a plurality of locations, the fragmentation of water molecules is further promoted.

[Embodiment 1]
FIG. 1 is an electrical connection diagram of the electromagnetic induction heating cooker according to the first embodiment of the present invention. In FIG. 1, a rectifier circuit DR1 rectifies the output of a commercial AC power source and converts it into a DC voltage, and a smoothing capacitor C7 smoothes the voltage converted into DC by the rectifier circuit DR1.

  The input current detection circuit ID detects an input current and outputs an input current detection signal Id, and the input voltage detection circuit IV detects an input voltage and outputs an input voltage detection signal Iv.

  The first switching element TR1 and the second switching element TR2 are switching elements that form a half-bridge type inverter circuit, and for example, MOSFETs or IGBTs are used. The resonant capacitor includes a third capacitor C3 having the same capacity as the first capacitor, a fourth capacitor C4 having a smaller capacity than the third capacitor C3, and a fifth capacitor C5 having the same capacity as the second capacitor. A resonance capacitor is formed by the sixth capacitor C6 having a smaller capacity than the fifth capacitor C5, and the resonance capacitor forms a series resonance circuit with the induction heating coil HL. The series resonance circuit forms a series resonance at a predetermined resonance frequency. The cluster mode selector switch SW selects the second capacitor C2 and the fifth capacitor C5 when set to the absence of the cluster mode, and selects the fourth capacitor C4 and the sixth capacitor C6 having a small capacity when set to the cluster mode. Select.

  The power calculation circuit SA inputs the input current detection signal Id and the input voltage detection signal Iv and calculates the input power of the inverter. The power setting circuit PC sets a predetermined power setting signal Pc.

  The differential amplifier circuit CO differentially amplifies the power setting signal Pc and the power calculation signal Sa, and outputs the value of the differential amplification signal ΔI. The control arithmetic circuit SC starts operation when a heating start signal Ts is input from the heating switch TS, and performs PFM control for modulating the pulse frequency with a constant pulse width ratio according to the value of the differential amplification signal ΔI. Do. Further, when the cluster mode is set by the operation panel OA, the control arithmetic circuit SC sets the output frequency range of the inverter circuit to a high range, and when the cluster mode is not set, the output frequency range of the inverter circuit is set to a low range. Set to.

  The inverter drive circuit SD outputs a switching element drive signal Sd1 and a switching element drive signal Sd2 that alternately drive the switching elements TR1 and TR2 in accordance with the value of the control processing signal Sc from the control arithmetic circuit SC.

  FIG. 2 is a relationship diagram between the operating frequency of the inverter circuit and the impedance of the series resonance circuit. When the cluster mode is not set, the output frequency range of the inverter circuit becomes a low output frequency range as shown in FIG. When the mode is set to be present, the output frequency range of the inverter circuit becomes a high output frequency range.

  Next, the operation will be described with reference to FIGS. First, when the cluster mode is set with the operation panel OA shown in FIG. 1, the control arithmetic circuit SC sets the output frequency range of the inverter circuit shown in FIG. 2 to a high range. Further, the cluster mode switching signal is set to High level and output.

  When the cluster mode switching signal becomes High level, the cluster mode changeover switch SW switches the contact from the a side to the b side to select the fourth capacitor C4 and the sixth capacitor C6 having a small capacity, and selects the selected one. A resonant capacitor is formed by each capacitor.

  The resonance frequency of the resonance capacitor formed as described above is such that the capacitance value of the resonance capacitor C is smaller than the equation f = 1 / (2π√ (L × C). In addition, the control arithmetic circuit SC controls the output frequency of the inverter circuit in a high output frequency range corresponding to the high resonance frequency.

  From the above, even when the output frequency of the inverter circuit is as shown in FIG. 2, for example, 180 KHz, which is a high output frequency, the impedance of the series resonant circuit is small, so that the rated thermal power can be obtained even at a high output frequency.

  When the cluster mode is not set, the cluster mode switching signal becomes low level, and the contact point of the cluster mode switching switch SW is switched from the b side to the a side to select the third capacitor C3 and the fifth capacitor C5 having a large capacity. Thus, a resonance capacitor is formed by each selected capacitor.

  The resonance frequency of the resonance capacitor formed is shown in FIG. 2 because the capacitance value of the resonance capacitor C is larger than the equation f = 1 / (2π√ (L × C). In addition, the control arithmetic circuit SC controls the output frequency of the inverter circuit in a low output frequency range corresponding to the low resonance frequency.

  As described above, when the cluster mode is set to be absent, the impedance of the series resonance circuit increases when the output frequency of the inverter circuit reaches a high output frequency shown in FIG. 2, for example, 180 KHz, and the rated thermal power cannot be obtained at a high output frequency.

[Embodiment 2]
FIG. 3 is an electrical connection diagram of the electromagnetic induction heating cooker according to the second embodiment of the present invention. In FIG. 3, the same reference numerals as those in the electrical connection diagram of the electromagnetic induction heating cooker according to the first embodiment of the present invention shown in FIG.

  The induction heating coil shown in FIG. 3 has a plurality of (for example, four) induction heating coils connected in parallel, and the inductance values of the plurality of induction heating coils connected in parallel are used in the first embodiment of the present invention. It is formed to be the same as the inductance value of one induction heating coil.

  As described above, the bottom of the pan PB is vibrated by the induction current at four locations by the four induction heating coils connected in parallel. This vibration is applied to the water at four locations as ultrasonic vibration. Thereby, since the water in the pan PB is ultrasonically vibrated at four locations and small clusters of water are performed at a plurality of locations, the subdivision of the water molecules is further promoted.

[Embodiment 3]
FIG. 4 is an electrical connection diagram of the electromagnetic induction heating cooker according to the third embodiment of the present invention. In FIG. 4, the same reference numerals as those in the electrical connection diagram of the electromagnetic induction heating cooker according to the first embodiment of the present invention shown in FIG.

  The induction heating coil shown in FIG. 4 has a plurality of (for example, four) induction heating coils connected in series, and the inductance values of the plurality of induction heating coils connected in series are used in the first embodiment of the present invention. It is formed to be the same as the inductance value of one induction heating coil.

  As described above, the bottom of the pan PB is vibrated by the induction current at four locations by the four induction heating coils connected in series. This vibration is applied to the water at four locations as ultrasonic vibration. As a result, the water in the pot PB is ultrasonically vibrated at four locations as in the second embodiment, and the water is further subdivided because the water small clusters are performed at a plurality of locations. .

It is an electrical connection figure of the electromagnetic induction heating cooking appliance of Embodiment 1 of this invention. FIG. 2 is a relationship diagram between the inverter operating frequency and the impedance of the series resonant circuit. It is an electrical connection figure of the electromagnetic induction heating cooking appliance of Embodiment 2 of this invention. It is an electrical connection figure of the electromagnetic induction heating cooking appliance of Embodiment 3 of this invention. It is an electrical connection figure of the electromagnetic induction heating cooking appliance of a prior art.

Explanation of symbols

CO differential amplifier circuit C1 first capacitor C2 second capacitor C3 third capacitor C4 fourth capacitor C5 fifth capacitor C6 sixth capacitor C7 smoothing capacitor DR1 rectifier circuit HL induction heating coil HL1 first induction Heating coil HL2 2nd induction heating coil HL3 3rd induction heating coil HL4 4th induction heating coil ID Input current detection circuit IV Input voltage detection circuit OA Operation panel PB Pan PC Power setting circuit PL Top plate SA Power calculation circuit SC Control arithmetic circuit SD Inverter drive circuit SW Cluster mode changeover switch TS Heating switch TR1 First switching element TR2 Second switching element Id Input current detection signal Iv Input voltage detection signal ΔI Differential amplification signal Oa Operation signal Sa Power calculation signal Sc control operation signal Sw cluster mode switching signal Ts heating start signal Sd1 first switching element driving signal Sd2 second switching element drive signal

Claims (2)

  A resonance capacitor formed by a first capacitor and a second capacitor, a series resonance circuit that forms a series resonance at a predetermined resonance frequency by the resonance capacitor and the induction heating coil, and a direct current by rectifying a commercial AC power source A rectifier circuit for converting the voltage into a voltage; an inverter circuit for supplying a high-frequency current to the induction heating coil using a DC voltage of the rectifier circuit as an input; an input power calculation circuit for calculating input power of the inverter circuit; and the input power calculation A power control differential amplifier circuit that compares and calculates a power input signal of a circuit and a power setting signal of a predetermined value and outputs the power control signal as a power control differential amplifier signal, and according to the power control differential amplifier signal And a control arithmetic circuit for controlling the output frequency of the inverter circuit, and the pan placed on the induction heating coil is heated by electromagnetic induction. In the induction heating cooker, there is provided a cluster mode changeover switch for setting the presence / absence of a cluster mode for reducing the aggregation of water molecules, and the first capacitor has a capacity higher than that of the third capacitor and the third capacitor. A small fourth capacitor, the second capacitor is a fifth capacitor and a sixth capacitor having a smaller capacity than the fifth capacitor, and the cluster mode selector switch is set to have a cluster mode. Then, the fourth capacitor is selected as the first capacitor, the sixth capacitor is selected as the second capacitor, the resonance frequency is increased, and the cluster mode changeover switch is set to no cluster mode. And selecting the third capacitor as the first capacitor and the second capacitor A cluster mode selector switch that selects the fifth capacitor as a capacitor and lowers the resonance frequency; and the control arithmetic circuit increases the output frequency range of the inverter when the cluster mode selector switch is set to cluster mode present. Set to a predetermined high output frequency range corresponding to the resonance frequency, and when the cluster mode changeover switch is set to no cluster mode, the output frequency range of the inverter is set to a predetermined low output frequency range corresponding to the low resonance frequency. An electromagnetic induction heating cooker that is a control arithmetic circuit that sets and controls the output frequency of the inverter within each output frequency range in accordance with the differential amplification signal for power control. 2. The electromagnetic induction heating cooker according to claim 1, wherein a plurality of the induction heating coils are connected in parallel or in series.

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