JP4776733B1 - Induction heating cooker - Google Patents

Abstract

【Task】
An inexpensive induction heating cooker that detects space-saving spillage.
[Solution]
A magnetic shield ring provided around the heating coil, a metal frame of the top plate, and a metal plate that reduces the repulsive force generated between the heating coil and the heating plate and the pan and the heating coil are used as electrodes. And a capacitance measuring means for measuring a capacitance between the electrode and the predetermined potential, and the control circuit may cause a spill if the capacitance between the electrode and the predetermined potential changes while driving the heating coil. It determines with having generate | occur | produced, a drive circuit is stopped, or a drive circuit is controlled so that the high frequency current sent through a heating coil may be decreased.
[Selection] Figure 2

Description

  The present invention relates to an induction heating cooker that detects spillage from a change in capacitance between an electrode installed around a heating coil and a predetermined potential.

  As an example of a conventional induction heating cooker that detects spilling, there is one that determines the occurrence of spilling from the change in capacitance between an electrode installed around a heating coil and a predetermined potential (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2008-159494 (FIG. 1)

  The conventional technique has a problem that it is necessary to newly provide an electrode under the top plate, which increases the cost.

The present invention includes a top plate on which a pan is placed, a heating coil that is provided under the top plate and that heats the pan, and a drive circuit that converts an AC voltage into a high-frequency voltage and causes a high-frequency current to flow through the heating coil. And an electrode provided on the back surface of the top plate so that no air layer exists between the top plate, and a capacitance measuring means for measuring a capacitance between the electrode and a predetermined potential; A control circuit that controls the drive circuit based on a measurement result of the capacitance measuring means; and a capacitance type operation unit that determines whether or not an operation instruction has been given by a change in capacitance. The capacitance measuring unit and the capacitance measuring circuit of the operation unit are the same microcomputers for measuring the capacitance, and one of the capacitance measuring unit and the capacitance measuring circuit of the operation unit is used. part also serves as a, The capacitance measuring means applies an AC voltage between the electrode and a predetermined potential, measures the capacitance based on an attenuation level of the applied voltage, and the control circuit includes the electrode and the predetermined potential. When the capacitance between the two changes, it is determined that a spill has occurred.

  The present invention occurs between a magnetic shield ring provided around a heating coil conventionally provided in an induction heating cooker, a metal frame of a top plate, and a pan and a heating coil provided between the heating coil and the top plate. By using a metal plate that reduces the repulsive force, a space for newly providing an electrode becomes unnecessary, and the cost can be reduced.

The induction heating cooking appliance which shows Embodiment 1 of this invention. The induction heating cooking appliance which shows Embodiment 1 of this invention. The induction heating cooking appliance which shows Embodiment 2 of this invention. The induction heating cooking appliance which shows Embodiment 2 of this invention. The induction heating cooking appliance which shows Embodiment 3 of this invention. The induction heating cooking appliance which shows Embodiment 3 of this invention. The induction heating cooking appliance which shows Embodiment 4 of this invention. An induction heating cooker showing Embodiment 5 of the present invention. An induction heating cooker showing Embodiment 5 of the present invention.

Embodiment 1 FIG.
FIG. 1 is an explanatory diagram showing a schematic configuration of an induction heating apparatus according to Embodiment 1 of the present invention. In the figure, an induction heating apparatus 1 includes a heating coil 2, a magnetic shield 3 that blocks leakage magnetic flux from the heating coil installed on the outer periphery of the heating coil, and an AC voltage from an AC power supply 4 that converts the AC voltage into a high-frequency voltage. 2, a drive circuit 5 for driving the drive circuit 2, a control circuit 6 for controlling the drive circuit 5, and a capacitance measurement circuit 7 for measuring the capacitance between the magnetic shield ring 3 and a predetermined potential.
The “capacitance measuring circuit 7” corresponds to “capacitance measuring means” in the present invention.

FIG. 2 is a side view of the heating coil portion of FIG. In FIG. 2, a pan 9 is placed on the top plate 8 as a cooking utensil, and a magnetic shield ring 3 is installed around a coil base 10 that fixes the heating coil 2 below the top plate 8. In addition, the magnetic-shielding ring 3 should just be the shape which surrounds the circumference | surroundings of the heating coil 2, and width | variety, thickness, etc. can be set arbitrarily. The electrostatic capacitance measuring circuit 7 measures the electrostatic capacitance (parasitic capacitance) between the magnetic shield ring 3 and a predetermined potential using the magnetic shield ring 3 as an electrode.
In the following description, the predetermined potential is the ground potential (hereinafter also referred to as GND), but the top plate mounting object may be the predetermined potential. Other than these, a predetermined potential may be used.

The relative dielectric constant (mainly air) between the magnetic shield ring 3 of area A and GND is K, the distance is d, and the vacuum dielectric constant is ε0. Then, the equation for obtaining the capacitance C is
C = K × ε0 × A / d
It becomes. The capacitance measuring circuit 7 applies an AC voltage between the GND in the measuring circuit 7 and the magnetic shielding ring. Since the applied AC voltage has a small amplitude when the capacitance is large, the capacitance is measured from the attenuation amount of the amplitude.

  When there is no spill, air with a relative permittivity of 1 exists mainly between the magnetic shield ring 3 and GND. However, when a spill occurs, water with a relative permittivity of 80 enters, so the capacitance increases rapidly. To do. Therefore, by checking the change in capacitance, it is possible to determine the overflow.

  When it is determined that the spilling has occurred, the operation of the drive circuit 5 is stopped, or the drive circuit 5 is controlled to reduce the current flowing through the heating coil 2.

As described above, in the present embodiment, the top plate 8 on which the pan 9 is placed, the heating coil 2 that is provided under the top plate 8 and heats the pan 9, and the AC voltage is converted into a high-frequency voltage. A drive circuit 5 for passing a high-frequency current through the heating coil 2, a magnetic shield 3 provided around the heating coil 2, a capacitance measuring circuit 7 for measuring the capacitance between the magnetic shield 3 and a predetermined potential, And a control circuit 6 that controls the drive circuit 5 based on the measurement result of the capacitance measurement circuit 7. The control circuit 6 has a capacitance between the magnetic shield ring 3 and a predetermined potential while driving the heating coil 2. If it has changed, it is determined that a spill has occurred, and the drive circuit 5 is stopped, or the drive circuit 5 is controlled to reduce the high-frequency current flowing through the heating coil 2.
As a result, it is possible to provide an induction heating cooker that does not use wasteful power and can minimize the contamination of the top plate 8 with the spilled contents.
Moreover, since the electrostatic capacitance between the magnetic-shielding ring 3 conventionally provided in the induction heating cooker and a predetermined electric potential is measured, an electrode for newly measuring the electrostatic capacitance is unnecessary, and an electrode is installed. Therefore, it is possible to provide a low-cost, space-use efficiency spill detection means that does not require a new space.

Embodiment 2. FIG.
FIG. 3 is an explanatory diagram showing a schematic configuration of the induction heating apparatus according to Embodiment 2 of the present invention. In the figure, 8 is a top plate, 2 is a heating coil installed under the top plate, and 11 is a metal frame for protecting the top plate installed around the top plate.

  FIG. 4 is a side view of FIG. In FIG. 4, a pan 9 is placed on the top plate 8 as a cooking utensil, and a magnetic shield ring 3 is installed around a coil base 10 that fixes the heating coil 2 below the top plate 8. A metal frame 11 is provided. Next, a second embodiment of the present invention will be described with reference to FIGS. The capacitance measuring circuit 7 uses the metal frame 11 as an electrode, and measures the capacitance (parasitic capacitance) between the metal frame 11 and GND.

  When there is no spillage, air with a relative permittivity of 1 is mainly present between the metal frame 11 and GND. However, when spillage occurs and the spilled pan content reaches the metal frame, the relative permittivity of 80 As water enters, the capacitance increases rapidly. Therefore, by checking the change in capacitance, it is possible to determine the overflow.

  When it is determined that the spilling has occurred, the operation of the drive circuit 5 is stopped, or the drive circuit 5 is controlled to reduce the current flowing through the heating coil 2.

As described above, in the present embodiment, the top plate 8 on which the pan 9 is placed, the metal frame 11 that protects the top plate 8 installed around the top plate 8, and the top plate 8 are provided, A heating coil 2 for heating the pan 9, a drive circuit 5 for converting an alternating voltage into a high-frequency voltage and causing a high-frequency current to flow through the heating coil 2, and an electrostatic for measuring a capacitance between the metal frame 11 and a predetermined potential A capacitance measuring circuit 7 and a control circuit 6 for controlling the drive circuit 5 based on the measurement result of the capacitance measuring circuit 7, and the control circuit 6 generates a predetermined potential and the metal frame 11 while driving the heating coil 2. When the electrostatic capacity changes during the period, it is determined that a spill has occurred, and the drive circuit 5 is stopped or the drive circuit 5 is controlled so as to reduce the high-frequency current flowing through the heating coil 2.
As a result, it is possible to provide an induction heating cooker that does not use wasteful power and can minimize the contamination of the top plate 8 with the spilled contents.
Moreover, since the electrostatic capacitance between the metal frame 11 provided in the induction heating cooker and the predetermined potential is measured conventionally, an electrode for newly measuring the electrostatic capacitance is unnecessary, and an electrode is installed. Therefore, it is possible to provide a low-cost, space-use efficiency spill detection means that does not require a new space.

Embodiment 3 FIG.
FIG. 5 is an explanatory diagram showing a schematic configuration of the induction heating apparatus according to Embodiment 3 of the present invention. In FIG. 5, a pan 9 is placed on the top plate 8 as a cooking utensil. The magnetic flux emitted from the heating coil 2 is suppressed between the top plate 8 and the heating coil 2, and the heating coil 2 and the pan 9 are A buoyancy prevention plate 12 that reduces the repulsive force acting between them and prevents the pan 9 from moving is installed. The buoyancy reduction plate 12 is a ring-shaped aluminum plate that covers the upper surface of the heating coil 2 as shown in FIG. The capacitance measurement circuit 7 measures the capacitance (parasitic capacitance) between the buoyancy reduction plate 12 and GND using the buoyancy reduction plate 12 as an electrode.
The “buoyancy reduction plate 12” corresponds to the “metal plate” in the present invention.

  When there is no spillage, air with a relative dielectric constant of 1 is mainly present between the buoyancy reduction plate 12 and GND, but spillage occurs and the spilled pan contents are on the top plate 8 of the buoyancy reduction plate 12. Since the water having a relative dielectric constant of 80 enters, the capacitance increases rapidly. Therefore, by checking the change in capacitance, it is possible to determine the overflow.

  When it is determined that the spilling has occurred, the operation of the drive circuit 5 is stopped, or the drive circuit 5 is controlled to reduce the current flowing through the heating coil 2.

As described above, in the present embodiment, the top plate 8 on which the pan 9 is placed, the heating coil 2 that is provided under the top plate 8 and heats the pan 9, and the AC voltage is converted into a high-frequency voltage. A drive circuit 5 for passing a high-frequency current through the heating coil, a buoyancy reduction plate 12 provided between the heating coil 2 and the top plate 8, and an electrostatic for measuring an electrostatic capacity between the buoyancy reduction plate 12 and a predetermined potential. And a control circuit 6 that controls the drive circuit 5 based on the measurement result of the capacitance measurement circuit 7. The control circuit 6 and the buoyancy reduction plate 12 while driving the heating coil 2 have a predetermined potential. When the electrostatic capacity between the two and the other changes, it is determined that the overflow has occurred, and the drive circuit 5 is stopped or the drive circuit 5 is controlled so as to reduce the high-frequency current flowing through the heating coil 2.
As a result, it is possible to provide an induction heating cooker that does not use wasteful power and can minimize the contamination of the top plate 8 with the spilled contents. Further, since the capacitance between the buoyancy reduction plate 12 provided in the induction cooking device and the predetermined potential is measured conventionally, an electrode for newly measuring the capacitance is unnecessary, and an electrode is installed. For this reason, it is possible to provide a low-cost, space-use-efficiency spill detector that does not require a new space.

Embodiment 4 FIG.
FIG. 7 is an explanatory diagram showing a schematic configuration of the induction heating apparatus according to Embodiment 4 of the present invention. The same parts as those in the embodiment are denoted by the same reference numerals, and description thereof is omitted. In FIG. 7, the magnetic shield ring 3 is pressed under the top plate by a spring structure 13 installed on the fixed base 14. The electrostatic capacitance measuring circuit 7 measures the electrostatic capacitance (parasitic capacitance) between the magnetic shielding ring 3 and GND using the magnetic shielding ring 3 as an electrode.

  When there is no spillage, air with a relative dielectric constant of 1 exists mainly between the magnetic shield ring 3 and GND, but spillage occurs, and the spilled pan contents reach the top plate 8 of the magnetic shield ring 3. Then, since water having a relative dielectric constant of 80 enters, the capacitance increases rapidly. Therefore, by checking the change in capacitance, it is possible to determine the overflow.

  When it is determined that the spilling has occurred, the operation of the drive circuit 5 is stopped, or the drive circuit 5 is controlled to reduce the current flowing through the heating coil 2.

As described above, in the present embodiment, the magnetic-shielding ring 3 is pressed against the back surface of the top plate 8 by the spring structure provided under the top plate 8, so that useless power can be saved. An induction heating cooker that can minimize contamination of the top plate 8 with the spilled contents can be provided.
In addition, by pressing a magnetic shield ring serving as an electrode against the back surface of the top plate 8 by a spring structure, there is no air layer between the top plate 8 and the magnetic shield ring 3, so that there is no decrease in capacitance between them. This makes it easier to detect spills.

Embodiment 5 FIG.
8 and 9 are explanatory diagrams showing a schematic configuration of the induction heating apparatus according to Embodiment 5 of the present invention. In FIG. 8, 8 is a top plate, 2 is a heating coil installed under the top plate 8, and 15 is a capacitive operation unit. An electrode (not shown) is installed under the top plate 8. When a human finger touches the operation unit, the capacitance between the electrode and GND changes, and it is detected that the switch has been operated.

In FIG. 9, a pan 9 is placed on the top plate 8 as a cooking utensil, and a magnetic shielding ring 3 is installed around a coil base 10 that fixes the heating coil 2 below the top plate 8. The capacitance measurement circuit 7 uses the magnetic shield ring 3 as an electrode, measures the electrostatic capacitance between the magnetic shield ring 3 and a predetermined potential, for example, GND, and the capacitance measurement circuit 7 further operates whether the operation unit 15 is operated. Detection is performed by a change in capacitance between the electrode installed in the unit 15 and GND. An example of a method for this purpose is to use the same IC or microcomputer for measuring capacitance. That is, a part or all of the circuit of the capacitance measuring circuit 7 or the substrate is used for both the overflow determination and the operation determination.
In the present embodiment, the electrostatic capacity is measured using the magnetic shield 3 as an electrode. However, it is also possible to measure the electrostatic capacity using an electrode that is conventionally provided in an induction heating cooker and can be regarded as an electrode. . Or you may provide the electrode for measuring a capacitance newly in an induction heating cooking appliance, and may measure a capacitance.

  As described above, the present embodiment includes the capacitance type operation unit 15 that determines whether or not an operation instruction has been issued due to a change in capacitance, and is operated by the capacitance measurement circuit 7 and the operation unit 15. By also using a part of the circuit for determining whether or not an instruction has been made or a substrate, it is not necessary to newly provide a capacitance measuring circuit for determining whether to spill or to determine operation, thereby saving space. Moreover, it can be made cheap by sharing a circuit and a board | substrate.

  In Embodiments 1 to 5, if it is determined that a spill has occurred, a message to that effect is displayed on the alarm means (not shown) or voiced to alert the user. can do.

  1 induction heating device, 2 heating coil, 3 magnetic shield ring, 4 AC power supply, 5 drive circuit, 6 control circuit, 7 capacitance measurement circuit, 8 top plate, 9 pan, 10 coil base, 11 metal frame, 12 buoyancy reduction Plate, 13 Spring structure, 14 Fixing base, 15 Operation part

Claims (1)

A top plate on which the pan is placed;
A heating coil provided under the top plate for heating the pan;
A drive circuit for converting an alternating voltage into a high frequency voltage and flowing a high frequency current through the heating coil;
An electrode provided on the back surface of the top plate so that no air layer exists between the top plate and the top plate;
A capacitance measuring means for measuring a capacitance between the electrode and a predetermined potential;
A control circuit for controlling the drive circuit based on the measurement result of the capacitance measuring means;
An electrostatic capacity type operation unit that determines whether or not an operation instruction has been made due to a change in electrostatic capacity;
With
Using the same microcomputer for measuring the capacitance of the capacitance measuring means and the capacitance measuring circuit of the operation unit, the capacitance measuring means and the capacitance measuring circuit of the operation unit also serves as a part of,
The capacitance measuring means applies an AC voltage between the electrode and a predetermined potential, measures the capacitance based on the attenuation level of the applied voltage,
The induction heating cooker, wherein the control circuit determines that a spill has occurred when a capacitance between the electrode and the predetermined potential changes.

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