JP5058296B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker, and particularly to control of a plurality of coils arranged concentrically.

  In a conventional induction heating cooker, for example, “a full bridge type inverter having three or more arms composed of at least two switching elements and composed of two arms, at least one of each of the inverters. A plurality of full-bridge inverter circuits in which one arm is shared with the arm of another inverter, a heating coil and a resonance connected to each full-bridge inverter circuit as a unit A set of a capacitor, a plurality of drive circuits provided for each arm and controlling the driving of the switching element of each arm, and two drive circuits corresponding to the arms constituting the full-bridge inverter circuit A control circuit that controls the drive circuit in a time-sharing manner for each set; and An electromagnetic induction heating device comprising a heating coil current detector shared by each of the full-bridge inverter circuits for detecting a current flowing in a coil is proposed (see, for example, Patent Document 1). ).

Japanese Patent No. 3687028 (Claim 1, pages 4-6, FIG. 1)

In the induction heating cooker described in Patent Document 1, a method is employed in which a plurality of coils arranged concentrically are controlled independently by a plurality of high-frequency power sources that share a rectifier circuit. However, since the rectifier circuit of the high-frequency power supply is shared, the method of detecting power consumption from the input current value to the commonly used rectifier circuit is the total power consumption of all coils connected to one rectifier circuit. Therefore, the power consumption of each coil cannot be detected. Therefore, power feedback control cannot be performed for each coil, and the power balance of each coil is shifted due to differences in driving conditions such as the type of pan and the driving frequency, causing heating unevenness.
Moreover, when the position of the placed pan is shifted from the center portion toward the outer periphery due to pan-shaking cooking or the like, there is a problem that the thermal power is reduced.
Moreover, there existed a problem that it cannot heat about the pot skin surface of the to-be-heated material with a wide opening like a frying pan.

  The present invention has been made to solve the above-described problems, and a first object is to provide an induction heating cooker that can prevent uneven heating. The second purpose is to prevent a reduction in the thermal power that occurs when the position of the pan is shifted, and the third purpose is induction heating that enables the pan skin surface of the object to be heated to be heated. To provide a cooker.

An induction heating cooker according to the present invention includes a top plate on which a pan is placed, a DC power source unit that converts AC power into DC power, and a plurality of high frequency power source units that convert DC power of the DC power source unit into high frequency power. And a plurality of coils arranged concentrically so as not to overlap under the top plate, and the outermost coil has a distance between the outermost coil and the top plate, A heating coil that is arranged so as to be shorter than the distance between the coil located on the inner side of the coil on the side and the top plate, and each of the heating coils to which high-frequency power is supplied from the plurality of high-frequency power supply units, A power calculation circuit for calculating an effective power of the outermost coil on the basis of a current flowing in the outermost coil and a voltage at both ends thereof, an input current detection unit for detecting an input current, and the input current detection unit Output and power Based on the output of the arithmetic circuit, the effective power of the coil located on the inner side of the coil on the outermost peripheral side is obtained, and the effective power of the coil on the outermost peripheral side and the coil located on the inner side of the coil on the outermost peripheral side And a control unit that controls the plurality of high-frequency power supply units based on the determination result .

  According to the induction heating cooker of the present invention, the effective power of the outermost coil is calculated based on the current flowing in the outermost coil and the voltage at both ends thereof, the diameter of the pan to be placed, the opening Efficient heating can be performed by optimally controlling the energization of the outermost coil according to the shape and mounting position. In addition, by adjusting the power of each coil independently, fine control without heating unevenness is possible.

It is a top view of the induction heating cooking appliance which concerns on Embodiment 1 of this invention. It is a top view of the heating coil of the induction heating cooking appliance of FIG. It is sectional drawing of the heating coil of the induction heating cooking appliance of FIG. It is a circuit block diagram of the drive circuit of the induction heating cooking appliance of FIG. It is a figure which shows each part operation | movement waveform of the electric power calculation circuit of the induction heating cooking appliance of FIG. It is a figure which shows the relationship between each part detection value of the induction heating cooking appliance of FIG. It is sectional drawing of the heating coil at the time of small diameter pan mounting of the induction heating cooking appliance of FIG. It is a figure which shows the relationship between the electricity supply state of the heating coil of the induction heating cooking appliance of FIG. 1, and a mounting pan. It is sectional drawing of the heating coil at the time of frying pan mounting of the induction heating cooking appliance of FIG. It is a figure which shows the drive state of the kind of mounting pan of the induction heating cooking appliance of FIG. 1, and a heating coil. It is a figure which shows the pan deviation state of the induction heating cooking appliance which concerns on Embodiment 2 of this invention. It is a figure which shows each part operation | movement waveform of the induction heating cooking appliance which concerns on Embodiment 2 of this invention. It is sectional drawing of the heating coil of the induction heating cooking appliance which concerns on Embodiment 3 of this invention. It is a figure which shows the installation state of the small pan in the induction heating cooking appliance which concerns on Embodiment 3 of this invention.

Embodiment 1 FIG.
1 is a top view of an induction heating cooker according to Embodiment 1 of the present invention.
The induction heating cooker in FIG. 1 includes a heat-resistant top plate (top plate) 1 on which a pan is placed. The top plate 1 includes a total of three heating ports, a right heating port 2, a left heating port 3, and a central heating port 4. Heating coils 5, 52, and 51 are respectively installed below the heating ports 2, 3, and 4 (note that the heating coils 5, 52, and 51 are shown by solid lines for convenience). When the pan is placed on the tops of 3 and 4, the pan is induction-heated by the high-frequency magnetic field generated from the heating coils 5, 52 and 51. The top plate 1 includes an operation / display unit 9. The operation / display unit 9 adjusts the heating power, selects a heating port, and the like by operating a switch by the user, and displays the heating state on a display device such as a liquid crystal panel.

FIG. 2 is a top view of the heating coil 5 of the induction cooking device of FIG.
The heating coil 5 is composed of, for example, two types of circular coils having different diameters, and is composed of a main coil 6 having a small diameter and an auxiliary coil 7 having a large diameter, which are arranged concentrically. That is, the auxiliary coil 7 is arranged on the outer peripheral side so as not to overlap the main coil 6 in plan view. The auxiliary coil 7 corresponds to the outermost coil of the present invention, and the main coil 6 corresponds to the coil positioned on the inner side of the outermost coil of the present invention. Although the main coil 6 may be composed of a plurality of coils, only one example will be described here.

FIG. 3 is a cross-sectional view of the heating coil 5 of the induction heating cooker of FIG.
The main coil 6 and the auxiliary coil 7 are arranged on the coil base 8. The coil base 8 is formed so that its outer peripheral side protrudes. The auxiliary coil 7 is disposed on the protruding portion, and is installed so that the upper surface of the coil is closer to the top plate 1 than the top plate 1 by a distance h.

FIG. 4 is a circuit configuration diagram of a drive circuit of the right heating port 2 of the induction heating cooker of FIG.
In FIG. 4, the drive circuit includes a rectifier circuit 10. The rectifier circuit 10 includes a diode bridge 12, a choke coil 13, and a smoothing capacitor 14, and is connected to a commercial power supply 11. An input current detection circuit 15 is provided between the commercial power supply 11 and the rectifier circuit 10 (diode bridge 12). The input current detection circuit 15 detects an input current flowing from the commercial power supply 11 to the rectifier circuit 10 and outputs an analog voltage value corresponding to the detection value to the control circuit 22. The control circuit 22 performs A / D conversion on the analog voltage value of the input current detection circuit 15 and reads it at regular intervals, and calculates and detects the input power to the drive circuit by integrating the input current and the commercial power supply voltage.

The rectifier circuit 10 performs full-wave rectification on the AC power input from the commercial power supply 11 to convert it into DC power, and outputs the DC power to the high-frequency power supply circuits 37 and 38. The high frequency power supply circuits 37 and 38 are connected in parallel to the DC bus at the output end of the rectifier circuit 10 and the ground line, and are configured by IGBTs 31 to 34 and IGBTs 35 and 36, respectively. IGBT is an abbreviation for insulated gate bipolar transistor. The high frequency power supply circuit 37 is composed of a so-called full-bridge type inverter in which two switching arms connected in series with two IGBTs are connected in parallel with a DC bus and a ground line. Alternatively, power control is performed by phase difference control. Similarly, the high frequency power supply circuit 38 includes a so-called half-bridge type inverter in which two switching arms, each having two IGBTs connected in series, are connected to a DC bus and a ground line. Power control is performed by duty control or frequency control.
Further, the high frequency power supply circuits 37 and 38 are driven at the same frequency so that the difference between the drive frequencies is not generated as interference sound. The switching operation of these switching arms converts direct current power into high frequency power of about 20 to 30 kHz.

  The main coil 6 and the resonance capacitor 16 are connected in series to the output terminal of the high frequency power supply circuit 37, and a high frequency voltage is applied by the operation of the high frequency power supply circuit 37 so that a resonance current flows. A coil current detection circuit 28 is provided in the series circuit of the main coil 6 and the resonance capacitor 16, and the coil current detection circuit 28 detects an analog voltage corresponding to the high-frequency current flowing through the main coil 6, and sends it to the control circuit 22. Output. Similarly, the auxiliary coil 7 and the resonance capacitor 17 are connected in series to the output terminal of the high frequency power supply circuit 38, and a resonance current flows by applying a high frequency voltage from the high frequency power supply circuit 38. A coil current detection circuit 18 is provided in the series circuit of the auxiliary coil 7 and the resonance capacitor 17, and the coil current detection circuit 18 detects an analog voltage corresponding to the high-frequency current flowing through the auxiliary coil 7 and outputs it to the control circuit 22. To do. 4 includes a coil voltage detection circuit 19, a multiplication circuit 20, and an integration circuit 21, which together with the coil current detection circuit 18 constitute a power calculation circuit 30. The power calculation circuit 30 outputs an analog voltage signal corresponding to the active power consumed by the auxiliary coil 7 to the control circuit 22. Details of the power calculation circuit 30 will be described with reference to FIG.

FIG. 5 is an operation waveform diagram of each part of the power calculation circuit of the induction heating cooker of FIG.
The coil voltage detection circuit 19 detects a differential voltage of a high frequency voltage of several tens of kHz applied to the auxiliary coil 7 and outputs an AC voltage signal corresponding to the differential voltage (FIG. 5A).
The coil current detection circuit 18 detects a high frequency current of several tens of kHz flowing through the auxiliary coil 7 and outputs an AC voltage signal corresponding to the current (FIG. 5B).
The multiplication circuit 20 multiplies the AC voltage signal output from the coil current detection circuit 18 and the AC voltage signal output from the coil voltage detection circuit 19 and outputs the result (FIG. 5C).
The integration circuit 21 integrates the alternating multiplication waveform output from the multiplication circuit 20, converts it to an analog DC voltage value, and outputs it to the control circuit 22 (FIG. 5 (d)).
As described above, the coil current detection circuit 18, the coil voltage detection circuit 19, the multiplication circuit 20, and the integration circuit 21 obtain and output an analog voltage value corresponding to the integrated average of the current flowing through the auxiliary coil 7 and the differential voltage. . For this reason, the power calculation circuit 30 outputs an analog voltage corresponding to the active power consumed by the auxiliary coil 7 to the control circuit 22.
Further, as described above, the control circuit 22 detects the input power of the entire drive circuit by integrating the input current from the input current detection circuit 15 and the commercial power supply voltage, and the power is calculated from the input power of the entire drive circuit. By subtracting the power consumption of the auxiliary coil 7 detected by the arithmetic circuit 30, the power consumption in the main coil 6 is detected.

Next, operation | movement of the induction heating cooking appliance of this Embodiment 1 is demonstrated.
FIG. 6 is a diagram showing the relationship between each part detection value of the induction heating cooker and the pan type according to the first embodiment. When the user places a pan on the right heating port 2 of the top plate 1 and cooking is started by operating the operation / display unit 9, the control circuit 22 immediately determines the high-frequency power supply circuits 37 and 38 for the pan type. Control with the drive signal. Since the equivalent impedance seen from the high-frequency power supply circuit differs depending on the type of pan placed, when the high-frequency power supply circuit is driven with a specific drive signal, the power consumption and the current flowing through the heating coil are different. The type of the loading pan is determined for each of the main coil 6 and the auxiliary coil 7 using a table of power consumption and coil current for pan determination that are generally used as shown in FIG. According to the result of determination of the pot type, for example, in the case of no load, aluminum / copper pot detection, the user is informed and the energization control is not performed. The energization of the high frequency power supply circuits 37 and 38 is controlled by the signal.

  FIG. 7 is a cross-sectional view of the heating coil when the large-diameter pan is placed in the induction heating cooker according to the first embodiment. In FIG. 7, the pan 23 is a pan having a diameter comparable to that of the auxiliary coil 7 (hereinafter referred to as a large-diameter pan). The large-diameter pan 23 is placed on the top plate 1. At that time, the large-diameter pan 23 is disposed so as to cover the main coil 6 and the auxiliary coil 7.

  FIG. 8 is a cross-sectional view of the heating coil when the small-diameter pan is placed in the induction heating cooker according to the first embodiment. In FIG. 8, the pan 25 is a pan (hereinafter referred to as a small-diameter pan) having a diameter that is the same as or smaller than that of the main coil 6.

  FIG. 9 is a cross-sectional view of the heating coil when the frying pan of the induction heating cooker according to the first embodiment is placed. In FIG. 9, the pan 26 is an object to be heated (hereinafter referred to as a frying pan) whose opening is wider than the bottom of the pan like a frying pan, and the bottom of the pan has an intermediate diameter between the main coil 6 and the auxiliary coil 7. It is assumed that the diameter of the opening has a diameter equivalent to that of the auxiliary coil 7.

When a pan is placed on the top plate 1 of the heating port 2 and an operation for starting cooking is performed by the user, the control circuit 22 immediately drives the high-frequency power supply circuits 37 and 38 by a drive signal for pan type determination. Then, the material and diameter of the placed pan are determined. When the large-diameter pan 23 is placed, both the main coil 6 and the auxiliary coil 7 detect the magnetic pan or the non-magnetic pan, so that the energization is controlled by the control circuit 22 using the driving signal for cooking. A heating operation is performed.
On the other hand, when the small-diameter pan 25 is placed, the control circuit 22 places no pan on the auxiliary coil 7 (no load), and places a magnetic pan or a non-magnetic pan on the main coil 6. This is detected, and only the main coil 6 is energized and controlled with a driving signal for cooking.
Further, when the frying pan 26 is placed, it is detected that a magnetic pan or a non-magnetic pan is placed on the main coil 6, and there is an opening portion of the placing pan on the auxiliary coil 7. And the energization control of the main coil 6 and the auxiliary coil 7 is performed.
FIG. 10 is a diagram summarizing the relationship between the type of the placing pan of the induction heating cooker and the driving state of the heating coil.

  After the pan determination described above, the control circuit 22 performs power feedback control of the main coil 6 and the auxiliary coil 7 based on the output signals of the input current detection circuit 15 and the power calculation circuit 30 so that the heating power set by the user is obtained. (However, in the case of the small-diameter pan 25, the auxiliary coil 7 is not energized), and the high-frequency power supply circuits 37 and 38 are driven. When the user performs a heating stop operation, the control circuit 22 stops energization of the high-frequency power supply circuits 37 and 38.

As described above, in the first embodiment, the auxiliary coil 7 (the outermost coil) is based on the current flowing through the auxiliary coil 7 (the outermost heating coil) and the detected value of the applied differential voltage. ), The auxiliary coil 7 (coil on the outermost periphery side) is energized in accordance with the diameter of the placing pan, and for example, the diameter of the placed pan is equal to or less than a predetermined value. In that case, efficient heating according to the pot diameter can be performed by stopping the energization of the high-frequency power supply circuit 38.
In addition, by adjusting the power of each of the main coil 6 and the auxiliary coil 7 independently, fine control without heating unevenness is possible.
Further, by driving the high frequency power supply circuits 37 and 38 at the same drive frequency, the generation of interference sound can be suppressed.
Further, the distance between the auxiliary coil 7 (coil on the outermost circumference) and the top plate 1 constituting the heating coil 5 is larger than that of the main coil 6 (coil located on the inner side of the coil on the outermost circumference: coil on the center side). Since the opening of the pot is above the auxiliary coil 7 (the outermost coil), the pot skin surface can be efficiently heated.

Embodiment 2. FIG.
Next, an induction heating cooker according to Embodiment 2 of the present invention will be described. Explanations and drawings are omitted for the same points as in the first embodiment.

FIG. 11 is a diagram showing a pan shift state of the induction heating cooker according to the second embodiment. FIG. 12 is a diagram illustrating a driving state of the high-frequency power supply circuit 38 and an output state of the power calculation circuit 30 when the induction heating cooker according to the second embodiment is placed on the small-diameter pan.
As in the first embodiment, when the small-diameter pan 25 sufficiently smaller than the diameter of the auxiliary coil 7 is placed at the position shown in FIG. 8 and cooking is started, the control circuit 22 is used for pan determination. The high frequency power supply circuit 38 is driven by the control signal, and it is detected that there is no pan on the auxiliary coil 7, and the energization control for cooking is not performed on the auxiliary coil 7 as in the first embodiment.

  After detecting the no-load state of the auxiliary coil 7, the control circuit 22 repeatedly performs the pan determination drive for the IGBTs 35 and 36 at a constant interval Tb, as shown in FIG. As shown in FIG. 8, when the small-diameter pan 25 is placed at the center of the heating port 2, there is a certain distance between the auxiliary coil 7 and the pan, so the power consumption of the auxiliary coil 7 is weak. Therefore, the output voltage of the power calculation circuit 30 becomes small. When the user puts the pan on the pan or cooks the pan and the pan position shifts in the outer peripheral direction of the heating port as shown in FIG. 11, the power consumption in the determination control period Ta of the auxiliary coil 7 increases. The output voltage value of the power calculation circuit 30 increases. When the output voltage value of the power calculation circuit 30 reaches the threshold value Pa, the control circuit 22 drives the auxiliary coil 7 with a driving signal for cooking. When it is detected that the position of the pan is corrected to the center and the power consumption in the auxiliary coil 7 is reduced, the control circuit 22 returns the high frequency power supply circuit to the drive for pan determination control at a constant interval Ta.

  As described above, in the second embodiment, the auxiliary coil 7 (coil on the outermost peripheral side) repeats the control for determining the pan (energized and de-energized) at regular intervals, so Since the mounting state can be detected instantaneously and auxiliary heating can be performed, the convenience of the user can be improved especially when the pan is tilted or the pan is displaced.

Embodiment 3 FIG.
Next, an induction heating cooker according to Embodiment 3 of the present invention will be described. Explanations and drawings that are the same as in Embodiments 1 and 2 are omitted.

FIG. 13 is a cross-sectional view of the heating coil of the induction heating cooker according to the third embodiment.
The coil base 8 is formed such that the surface on the outer peripheral side thereof is smoothly raised, and the auxiliary coil 7 disposed at that portion is installed to be inclined with respect to the center of the heating coil 5 by an angle α. The distance from the top plate 1 is shorter than that of the main coil 6.

  FIG. 14 is a diagram illustrating an installation state of the short pan of the induction heating cooker according to the third embodiment. In FIG. 14, the pan 27 is a short pan whose bottom surface has an intermediate diameter between the main coil 6 and the auxiliary coil 7.

  When the small pan 27 is placed on the top plate 1, the control circuit 22 detects that a magnetic pan or a non-magnetic pan is placed on the main coil 6, and the auxiliary coil 7 is positioned vertically. It detects that there is a pan skin surface of the small-size pan 27 in the direction, and controls energization of both the main coil 6 and the auxiliary coil 7.

  As described above, according to the third embodiment, the auxiliary coil 7 (outermost peripheral coil) is arranged by inclining the auxiliary coil 7 (outermost peripheral coil) with respect to the center of the heating coil 5. Therefore, the user's convenience can be improved because the pot skin surface of the small-size pan 27 in the vertical direction can be heated.

  1 top plate, 2 right heating port, 3 left heating port, 4 central heating port, 5, 51, 52 heating coil, 6 main coil, 7 auxiliary coil, 8 coil base, 9 operation / display unit, 10 rectifier circuit, 11 Commercial power supply, 12 Diode bridge, 13 Choke coil, 14 Smoothing capacitor, 15 Input current detection circuit, 16, 17 Resonance capacitor, 18, 28 Coil current detection circuit, 19 Coil voltage detection circuit, 20 Multiplication circuit, 21 Integration circuit, 22 Control circuit, 23 large-diameter pan, 25 small-diameter pan, 26 frying pan, 27 inch pan, 30 power calculation circuit, 31-36 IGBT 37, 38 high-frequency power supply circuit.

Claims (5)

A top plate on which the pan is placed;
A DC power supply unit that converts AC power into DC power;
A plurality of high frequency power supply units for converting DC power of the DC power supply unit to high frequency power;
A plurality of coils arranged concentrically so as not to overlap are provided under the top plate, and the outermost coil is such that the distance between the outermost coil and the top plate is the outermost coil. A heating coil that is arranged to be shorter than the distance between the coil located on the inner side of the coil and the top plate, and is supplied with high-frequency power from each of the plurality of high-frequency power supply units,
Among the heating coils, a power calculation circuit that calculates the effective power of the outermost coil based on the current flowing in the outermost coil and the voltage at both ends thereof,
An input current detecting means for detecting an input current ;
Based on the output of the input current detection means and the output of the power calculation circuit, the effective power of the coil located on the inner side of the outermost periphery side coil is obtained, and the effective power of the outermost periphery side coil and the outermost periphery are determined. And a control unit for determining the placement state and type of the pan on the basis of the active power of the coil located on the inner side of the coil on the side, and for controlling the plurality of high frequency power supply units based on the determination result. Induction heating cooker featuring. When the diameter of the placed pan is less than a predetermined value determined in advance, according to claim 1, characterized in that stopping the energization of the outermost peripheral side of the high-frequency power supply for supplying high frequency power to the coil Induction heating cooker. The high-frequency power supply for supplying high-frequency power to the outermost coil is alternately energized and de-energized at regular intervals,
2. The induction heating cooking according to claim 1 , wherein the control unit determines a mounting state of the pan on the outermost coil on the basis of the effective power of the outermost coil at that time. vessel. The induction heating cooker according to any one of claims 1 to 3 , wherein the plurality of high-frequency power supply units are energized and controlled at the same frequency. The outermost peripheral side of the coil, at an angle to the top plate, to any one of claim 1 to 4, characterized in that it is disposed inclined toward the center of the heating coil The induction heating cooker described.

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