JP5073019B2 - Induction heating cooker - Google Patents

Description

  The present invention relates to an induction heating cooker having a plurality of heating coils as one heating port.

  In some conventional induction heating cookers, a plurality of small heating coils are arranged close to each other on the same plane and connected in series, and currents flowing in the adjacent portions thereof are directed in the same direction. Therefore, the magnetic fluxes generated by the current flowing through the small heating coil are superimposed on each other without canceling each other out. Therefore, when heating a large-diameter pan, induction heating is performed with high heating efficiency and less uneven heating. (For example, refer to Patent Document 1).

Japanese Utility Model Publication No. 3-33993 (page 4, FIG. 2)

However, when the above-described conventional induction heating cooker heats a small-diameter pan, the coil current flows in the same manner as the heating coil in which the pan is positioned above the heating coil in which the pan to be heated is not positioned above. There is a problem that magnetic flux leaks around the heating port and heating efficiency decreases.
In addition, since a plurality of small heating coils are connected in series, the voltage generated in each heating coil is added, so a high voltage may be generated between the heating coils arranged close to each other. It was necessary to ensure high insulation.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an induction heating cooker having high heating efficiency and high safety even for a small-diameter pan.

The induction heating cooker according to the present invention is arranged in the vicinity of the center plate of the mounting position below the top plate on which the mounting position of the heated object is displayed, and can be heated independently. A central heating coil, a plurality of peripheral heating coils arranged close to the periphery of the central heating coil, an inverter circuit that applies a high-frequency voltage to the central heating coil and the plurality of peripheral heating coils, and an output of the inverter circuit are controlled And a central heating coil having a larger diameter and a smaller number of turns than the plurality of peripheral heating coils, the plurality of peripheral heating coils connecting the individual heating coils in parallel, and each outer peripheral end being connected to the central heating coil The central heating coil is connected in parallel so as to be connected to the outer peripheral end, and a high frequency voltage is applied to the central heating coil and the plurality of peripheral heating coils in the reverse circulation direction.

  Further, the induction heating cooker according to the present invention includes a central current detection unit that detects a high-frequency current flowing through the central heating coil, and a peripheral current detection unit that detects a high-frequency current flowing through the peripheral heating coil, and the control unit includes: When the high frequency current flowing through the peripheral heating coil with respect to the high frequency current flowing through the central heating coil falls below a predetermined range, the application of the high frequency voltage to the peripheral heating coil is stopped by controlling the inverter circuit.

According to the present invention, since a high-frequency voltage is applied to the central heating coil and the plurality of peripheral heating coils in the reverse circulation direction, when a heated object having a large diameter is placed above the top plate, The high-frequency magnetic flux generated by the high-frequency current flowing in the adjacent heating coils is superimposed without canceling each other, and is linked to the object to be heated placed on the top plate. Thereby, heating efficiency is high and heating unevenness can also be reduced.
In addition, when a small-diameter object to be heated is placed above the top plate, the inductance of the central heating coil that is magnetically coupled with the bottom of the object to be heated positioned lower, and a large high-frequency current is generated in the heating coil The inductance of the peripheral heating coil that flows and the bottom of the object to be heated is not positioned upward is increased, and the high-frequency current flowing through the heating coil is suppressed. Thereby, the increase in the leakage magnetic field to this cooker periphery and the fall of heating efficiency can be suppressed.
Furthermore, since the energization to the peripheral heating coil can be stopped and the central heating coil can be heated by itself, it is possible to reduce the leakage magnetic field around the cooker when the small-diameter heated object is heated. .

  In addition, when the high-frequency current flowing through the peripheral heating coil detected by the peripheral current detection unit with respect to the high-frequency current flowing through the central heating coil detected by the central current detection unit falls below a predetermined range, the control unit controls the inverter circuit. Since the application of high-frequency voltage to the peripheral heating coil is stopped, the peripheral heating is performed when a small-diameter heated object that is magnetically coupled to the central heating coil but not magnetically coupled to the peripheral heating coil is placed above the top plate. The energization to the coil can be stopped and the central heating coil alone can be heated. Thereby, the fall of heating efficiency can be suppressed and the leakage magnetic field around this cooker can be reduced.

  In addition, since the individual heating coils of the plurality of peripheral heating coils are connected in parallel, the inductance of the peripheral heating coil that is magnetically coupled with the bottom of the object to be heated positioned upward is reduced, and a large high-frequency current is generated in the heating coil. The inductance of the peripheral heating coil where the bottom of the object to be heated is not positioned upward is increased and the high-frequency current flowing through the heating coil is suppressed, so that the leakage magnetic field around the cooker increases and the heating efficiency decreases. Can be suppressed.

Further, it is possible to so connecting the outer peripheral end of the outer peripheral end and surrounding the heating coil of the central heating coil, high voltage is not generated between the central heating coil and surrounding the heating coil, high safety.

  In addition, since the central heating coil has a larger diameter than a plurality of peripheral heating coils and has a smaller number of turns, the inductance of the central heating coil that heats the bottom of the object to be heated wider than the peripheral heating coil is reduced to reduce the heating power. The increase in uneven heating can be suppressed.

It is a figure which shows the circuit structure of the induction heating cooking appliance in Embodiment 1 of this invention. 3 is a schematic diagram illustrating a positional relationship between a heating coil and a pan in Embodiment 1. FIG. FIG. 6 is a layout diagram of heating coils showing another form of the first embodiment. It is a circuit block diagram of the induction heating cooking appliance which shows the other form of Embodiment 1. FIG. It is a figure which shows the circuit structure of the induction heating cooking appliance in Embodiment 2 of this invention. It is a side view which shows the positional relationship of the heating coil and pan in Embodiment 2. It is a figure which shows the circuit structure of the induction heating cooking appliance in Embodiment 3 of this invention. FIG. 10 is a layout diagram of heating coils showing another form of the third embodiment. It is a figure which shows the circuit structure of the induction heating cooking appliance in Embodiment 4 of this invention. It is a schematic diagram which shows the positional relationship of the heating coil and pan in Embodiment 4.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a circuit configuration of an induction heating cooker according to Embodiment 1 of the present invention.
In FIG. 1, a DC power supply circuit 2 connected to an AC power supply 1 is composed of a rectifier circuit 3, a choke coil 4 and a smoothing capacitor 5, and converts AC power into DC power when the AC power supply 1 is applied. The inverter circuit 6 provided on the output side of the DC power supply circuit 2 includes switching elements 7 and 8 connected in series between the DC buses, and antiparallel diodes 9 connected in antiparallel to the switching elements 7 and 8, respectively. 10 and converts the DC power, which is the output of the DC power supply circuit 2, into high-frequency power based on the operation of each of the switching elements 7 and 8, for example, from four heating coils 12 a to 12 d and the resonance capacitor 13. A high frequency voltage is applied to the configured resonance circuit 11.

  The heating coils 12a to 12d described above are formed with the same diameter and number of turns, and are arranged close to the grid below the placement position of the heated object (for example, a pan) displayed on the top plate of the cooker. ing. These heating coils 12 a to 12 d are wound around the heating coils and conductors adjacent to each other and are wound in opposite directions, and the connection points of the switching elements 7 and 8 whose inner peripheral ends are the output ends of the inverter circuit 6. The outer peripheral ends are connected to each other and connected to the low potential bus of the DC power supply output via the common resonant capacitor 13, and the heating coils 12a and 12c are connected in parallel to each other. Yes. Therefore, the same voltage as the difference between the output voltage of the inverter circuit 6 and the resonance voltage generated in the resonance capacitor 13 is applied to the heating coils 12a to 12d. Moreover, since the high frequency voltage is applied to the heating coils 12a and 12d and the heating coils 12b and 12c in the reverse winding direction from the winding direction and the connection state of the heating coils 12a to 12d, the heating coils 12a and 12d. The high-frequency current in the opposite direction flows through the heating coils 12b and 12c.

  The input current detection circuit 14 is installed on one input side of the DC power supply circuit 2 and detects an input current to the cooker. The output current detection circuit 15 is installed on the low potential side bus and detects the output current flowing through the resonance circuit 11. The drive circuit 16 outputs a pulse signal that alternately drives the switching elements 7 and 8 constituting the inverter circuit 6. The control unit 17 controls the entire cooking device, and controls the drive circuit 16 according to the set heating power.

Next, the effect | action of the heating coil by the positional relationship with a pan is demonstrated using FIG. FIG. 2 is a schematic diagram showing the positional relationship between the heating coil and the pan in the first embodiment. In addition, (a) and (c) show the positional relationship between the heating coil and the pan as seen from the top surface, and (b) and (d) show the positional relationship between the heating coil and the pan as seen from the side surface.
As shown in (a) and (b), when the pan 19 on the top plate 18 is placed at a position where the pan 19 is evenly magnetically coupled to the four heating coils 12a to 12d, each heating coil 12a to 12a. The impedance of 12d is almost the same value. In this case, since the same high-frequency voltage is applied to each of the heating coils 12a to 12d, substantially the same high-frequency current flows through each of the heating coils 12a to 12d along the winding direction of the conductor. The high-frequency magnetic flux generated by the high-frequency current is superimposed without canceling each other, and interlinks with the pot 19 placed on the top plate 18.

  On the other hand, as shown in (c) and (d), when the pan 19 is shifted and placed toward the heating coils 12c and 12d, the heating coils 12a and 12b are compared with the heating coils 12c and 12d. The magnetic coupling with the pan 19 is weakened and the inductance is increased. As a result, the high-frequency current flowing through the heating coils 12a and 12b is suppressed and reduced as compared with the high-frequency current flowing through the heating coils 12c and 12d, so that the high-frequency magnetic field leaks around the cooker without interlinking with the pan 19. Is suppressed.

  As described above, according to the first embodiment, the plurality of heating coils 12a to 12d are arranged so that the winding directions of the heating coil and the conductor adjacent to each other are opposite to each other, and therefore flow to the adjacent side of the heating coil. The direction of the high-frequency current is the same, and therefore, the high-frequency magnetic flux generated by the high-frequency current is superimposed without canceling each other, and there is an effect that the heating efficiency is high and the heating unevenness is small.

  In addition, since the resonance capacitor 13 is shared by the four heating coils 12a to 12d, the cost can be reduced and the circuit can be downsized compared to the case where the resonance capacitor is used for each of the heating coils 12a to 12d. Since the high-frequency voltages applied to the heating coils 12a to 12d can be made the same, the high-frequency currents flowing through the heating coils 12a to 12d have almost the same phase, and stable control is possible.

  Furthermore, since the outer peripheral ends of the heating coils 12a to 12d are connected to each other and kept at the same potential, a high voltage is not applied between the adjacent heating coils 12a to 12d. There is no need to maintain a high level of insulation performance between 12a to 12d.

  In the first embodiment, four heating coils are shown. However, for example, as shown in FIG. 3, heating coils other than four may be used, and these heating coils are arranged in parallel. What is necessary is just to connect and apply a high frequency voltage to an adjacent heating coil in a mutually reverse direction. Moreover, as shown in FIG. 4, you may make it provide the resonant capacitor with respect to each heating coil 12a-12d each independently. Also in this case, the outer peripheral ends of the heating coils 12a to 12d are connected to have the same potential and connected to the output end side of the inverter circuit 6, thereby avoiding the occurrence of a high voltage between the adjacent heating coils 12a to 12d. be able to.

Embodiment 2. FIG.
In the second embodiment, a heating coil is added to the center of four heating coils 21a to 21d arranged in a lattice shape, and will be described below with reference to FIGS. FIG. 5 is a diagram showing a circuit configuration of the induction heating cooker according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the same or equivalent part as Embodiment 1 demonstrated in FIG. 1, 2, and description is abbreviate | omitted.

  In FIG. 5, the central heating coil 20 is formed with the same diameter and number of turns as the heating coils 21 a to 21 d (hereinafter referred to as “peripheral heating coil”), and the central axis of the pan mounting position is located below the top plate. It is arranged as the center. The central heating coil 20 is wound in a direction opposite to the winding direction of the peripheral heating coils 21 a to 21 d arranged close to the periphery, and the switching element whose inner peripheral end is the output end of the inverter circuit 6. 7 and 8 are connected to each other, the outer peripheral ends are connected to each other, are connected to a common resonance capacitor 13, and the central heating coil 20 and the peripheral heating coils 12a to 12d are connected in parallel to each other. Yes. Therefore, no large voltage is generated on the adjacent side of the central heating coil 20 and the peripheral heating coils 21a to 21d, and a high frequency voltage in the reverse winding direction is applied to the central heating coil 20 and the peripheral heating coils 21a to 21d. Therefore, high-frequency currents in opposite directions flow. In addition, the peripheral heating coils 21a to 21d have the same winding direction of the conductor, and therefore high frequency currents in the same direction flow.

Next, the effect | action of the heating coil by the positional relationship with a pan is demonstrated using FIG. FIG. 6 is a side view showing the positional relationship between the heating coil and the pan in the second embodiment. In addition, (a) shows the positional relationship with the heating coil when the large-diameter pan is placed, and (b) shows the positional relationship with the heating coil when the small-diameter pan is placed.
As shown in (a), when the large-diameter pan 19a is placed on the top plate 18, the large-diameter pan 19a is not only magnetically coupled to the central heating coil 20, but is also magnetically coupled to the peripheral heating coils 21a to 21d. The degree of magnetic coupling is slightly stronger in the central heating coil 20 than in the peripheral heating coils 21a to 21d. In this case, the inductance of the central heating coil 20 is slightly smaller than the inductances of the peripheral heating coils 21a to 21d, and a high frequency current slightly larger than the peripheral heating coils 21a to 21d flows through the central heating coil 20.

  On the other hand, as shown in (b), when the small-diameter pan 19b is placed on the top plate 18, the small-diameter pan 19b is magnetically coupled to the central heating coil 20, but is almost mounted on the peripheral heating coils 21a to 21d. In this state, there is almost no magnetic coupling. In this case, the inductances of the peripheral heating coils 21a to 21d are significantly increased as compared with the inductance of the central heating coil 20, and the high-frequency current flowing through the peripheral heating coils 21a to 21d is significantly suppressed and lowered. As a result, the high-frequency magnetic flux generated by the high-frequency current flowing through the peripheral heating coils 21a to 21d is not linked to the small-diameter pan 19b, and the high-frequency magnetic flux leaking around the cooker is also suppressed from flowing to the peripheral heating coils 21a to 21d. The amount is reduced.

  As described above, in the second embodiment, the high-frequency current flowing through the central heating coil 20 and the high-frequency current flowing through the peripheral heating coils 21a to 21d flow in opposite directions, so that the high-frequency current flows in the same direction on the adjacent side, Since the magnetic fields generated by the high-frequency current do not cancel each other, the heating can be efficiently performed while suppressing uneven heating.

  Moreover, since the high frequency current flows through the central heating coil 20 magnetically coupled to the pan and the high frequency current flowing through the peripheral heating coils 21a to 21d that are not magnetically coupled is suppressed, the high frequency magnetic flux leaking around the cooker is suppressed. It is possible to suppress a decrease in heating efficiency with respect to the small-diameter pan 19b.

  Furthermore, since the outer peripheral end of the central heating coil 20 and the outer peripheral ends of the peripheral heating coils 21a to 21d are connected to each other and have the same potential, no high voltage is generated between the central heating coil 20 and the peripheral heating coils 21a to 21d. Therefore, safety is high.

  In the second embodiment, the central heating coil 20 is strongly magnetically coupled to the pan and has a smaller inductance than the peripheral heating coils 21a to 21d, and a larger coil current flows than the peripheral heating coils 21a to 21d. Since there are many cases, the temperature balance of the heating coil portion can be improved and the reliability can be improved by strengthening the cooling of the central heating coil 20 over the cooling of the peripheral heating coils 21a to 21d.

Embodiment 3 FIG.
In the second embodiment described above, the diameter and the number of turns of the central heating coil 20 and the peripheral heating coils 21a to 21d are the same. However, in the third embodiment, as shown in FIG. The diameter of the heating coil 20a is increased and the number of turns thereof is reduced. When the diameter of the central heating coil 20a is larger than the diameter of the peripheral heating coils 21a to 21d, the pan bottom area heated by the high frequency current flowing in the central heating coil 20a is heated by the high frequency current flowing in the peripheral heating coils 21a to 21d. Although it becomes relatively larger than the pan bottom area, the number of turns of the central heating coil 20a is reduced to increase the high-frequency current flowing through the central heating coil 20a, and the heating power of the central heating coil 20a is increased, thereby suppressing the increase in heating unevenness. be able to.

  In the second and third embodiments, as shown in FIG. 8A, a central heating coil 20a is arranged below the top plate 18 around the central axis of the pan mounting position 18a, and the central heating coil Although it has been described that the four peripheral heating coils 21a to 21d are arranged in the vicinity of the periphery of 20a, as shown in FIG. 8B, the six peripheral heating coils 21e to 21j are connected to the central heating coil 20a. You may arrange | position close to a periphery, and as shown in the figure (c), you may arrange | position three peripheral heating coils 21k-21m close to the periphery of the center heating coil 20a.

Embodiment 4 FIG.
FIG. 9 is a diagram showing a circuit configuration of an induction heating cooker according to Embodiment 4 of the present invention. In addition, the same code | symbol is attached | subjected to the same or equivalent part as Embodiment 3 demonstrated in FIG. 7, and description is abbreviate | omitted.
In FIG. 9, the central current detection means 15a is installed between the central heating coil 20a and the resonance capacitor 13, and detects a high-frequency current flowing through the central heating coil 20a. The peripheral current detection means 15b is installed between the connection point of the switching elements 7 and 8 of the inverter circuit 6 and the connection point of the four peripheral heating coils 21a to 21d, and is connected to the four peripheral heating coils 21a to 21d. Detect the flowing high-frequency current. The opening / closing means 22 is a normally closed switch inserted between the connection point of the switching elements 7 and 8 of the inverter circuit 6 and the peripheral current detection means 15b. The control unit 17 according to the fourth embodiment switches the opening / closing means 22 when the high-frequency current detected by the peripheral current detection means 15b falls below a predetermined range with respect to the high-frequency current detected by the central current detection means 15a. Peripheral heating coil disconnecting means for opening is provided.

Next, the effect | action of the heating coil by the positional relationship with a pan is demonstrated using FIG. FIG. 10 is a schematic diagram showing the positional relationship between the heating coil and the pan in the fourth embodiment. In addition, (a) and (c) show the positional relationship between the heating coil and the pan as seen from the top surface, and (b) and (d) show the positional relationship between the heating coil and the pan as seen from the side surface.
As shown in (a) and (b), when the large-diameter pan 19a is placed on the placement position 18a displayed on the top plate 18, the large-diameter pan 19a is not only magnetically coupled to the central heating coil 20, The peripheral heating coils 21a to 21d are also magnetically coupled, and the high-frequency current of the peripheral heating coils 21a to 21d detected by the peripheral current detection means 15b is compared with the high-frequency current of the central heating coil 20 detected by the central current detection means 15a. The magnitude is a value within a predetermined range.

On the other hand, as shown in (c) and (d), when the small-diameter pan 19b is placed on the placement position 18a of the top plate 18, it is magnetically coupled to the central heating coil 20, but on the peripheral heating coils 21a to 21d. Is almost in a state of being not mounted, and thus is almost in a magnetically coupled state. In this case, the magnitude of the high-frequency current of the peripheral heating coils 21a to 21d detected by the peripheral current detection means 15b is greatly suppressed with respect to the high-frequency current of the central heating coil 20 detected by the central current detection means 15a. , Falls below a predetermined range. In this case, the normally closed opening / closing means 22 is opened by the control of the control unit 17, and the peripheral heating coils 21 a to 21 d are disconnected from the output of the inverter circuit 6, and the high-frequency current flowing through the peripheral heating coils 21 a to 21 d is interrupted.
Thereby, the high frequency magnetic flux which leaks to this cooker periphery can be suppressed, and the fall of the heating efficiency with respect to the small diameter pan 19b can be suppressed more.

1 DC power supply circuit, 6 inverter circuit, 11 resonance circuit, 12a to 12d heating coil, 13 resonance capacitor, 14 input current detection circuit, 15 output current detection circuit,
15a central current detection means, 15b peripheral current detection means, 16 drive circuit, 17 control unit, 18 top plate, 18a pan placement position, 19 pan, 19a large diameter pan, 19b small diameter pan, 22 opening / closing means.

Claims (2)

A top plate displaying the position of the object to be heated;
A central heating coil disposed below the top plate in the vicinity of the central axis of the mounting position and capable of heating the heated object alone;
A plurality of peripheral heating coils disposed proximate to the periphery of the central heating coil;
An inverter circuit for applying a high frequency voltage to the central heating coil and the plurality of peripheral heating coils;
A control unit for controlling the output of the inverter circuit,
The central heating coil is configured with a larger diameter and fewer turns than the plurality of peripheral heating coils,
The plurality of peripheral heating coils are connected in parallel to the central heating coil so that the individual heating coils are connected in parallel, and the outer peripheral ends thereof are connected to the outer peripheral ends of the central heating coils.
An induction heating cooker, wherein a high-frequency voltage is applied to the central heating coil and the plurality of peripheral heating coils in a reverse circulation direction. A central current detecting means for detecting a high-frequency current flowing in the central heating coil;
A peripheral current detection means for detecting a high-frequency current flowing in the peripheral heating coil,
The controller controls the inverter circuit to stop the application of the high frequency voltage to the peripheral heating coil when the high frequency current flowing to the peripheral heating coil with respect to the high frequency current flowing to the central heating coil falls below a predetermined range. The induction heating cooker according to claim 1, wherein:

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