CN116508396A

CN116508396A - Thawing and heating cooking device

Info

Publication number: CN116508396A
Application number: CN202180077010.3A
Authority: CN
Inventors: 堀内敬介; 大前彩
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2020-12-09
Filing date: 2021-10-04
Publication date: 2023-07-28
Also published as: WO2022123875A1; JP2022091333A

Abstract

The invention aims to provide a defrosting heating cooker capable of inhibiting the enlargement of the device. The defrosting heating cooker of the invention comprises: a pair of electrodes (positive electrode 1a, negative electrode 1 b) for thawing the food material (6) in the heating chamber (3) by dielectric heating; a heating coil (2) for induction heating of the food material (6) thawed by dielectric heating of the pair of electrodes; and a change-over switch semiconductor (50) for switching the power supplied to the pair of electrodes or the heating coil (2). The heating coil (2) is arranged below the electrode arranged below the pair of electrodes. A defrosting heating cooker (100) is provided with: a converter circuit (60) that converts alternating current to direct current; and an inverter circuit (30) connected to the converter circuit (60) and having an upper arm semiconductor (31) and a lower arm semiconductor (32) for performing switching operation. An inverter circuit (30) is connected in parallel with the pair of electrodes and the heating coil (2) via the switching semiconductor (50).

Description

Thawing and heating cooking device

Technical Field

The present invention relates to a defrosting heating cooker.

Background

In a household microwave oven, when cooking food in a frozen state, microwaves (frequency 2.45 GHz) are used from thawing to heating. Since the wavelength of the microwaves is short, when the food is large, the microwaves do not penetrate into the center of the food, and time is required for thawing. Further, since the dielectric loss coefficient of water contained in the food material after thawing is larger than that of ice before thawing, thawing unevenness may occur in which a portion from ice to water is overheated first.

On the other hand, if dielectric heating (dielectric heating) with a high frequency of 1 to 100MHz is used, the dielectric loss ratio of ice to water before and after thawing is small, and therefore, it is considered that the thawing is suitable for thawing with little unevenness, and a high frequency is used in a thawing machine for business use or the like. However, high frequency requires time for heating compared to microwaves. From such a background, it is generally known to switch between high-frequency heating and microwave heating, and to use high-frequency heating (13 to 40 MHz) for thawing and microwave (2.45 GHz) for heating.

On the other hand, the dielectric heating system such as high-frequency heating and microwave heating is a cooking method for heating from inside of the food material, and is therefore not suitable for use in grill cooking with scorching or the like on the surface of the food material. Heating from outside the food material is required in grill cooking. As a method of heating from the outside of the food, there is, for example, induction heating (induction heating). Patent documents 1 to 3 are examples of cooking devices using the induction heating and the microwave heating.

Patent document 1 discloses a microwave oven in which an oven frame is housed in a box-shaped oven body, and a heating coil for electromagnetic cooking is laid on the oven frame. A waveguide is connected to the oven frame, and a magnetron is connected to the waveguide.

Patent document 2 discloses a high-frequency heating cooker with electromagnetic induction heating, in which a magnetron, an electromagnetic induction heating coil, and a relay for switching power supply to the magnetron and the electromagnetic induction heating coil are provided at a lower portion of a heating cooker body.

Patent document 3 discloses a heating cooker in which an induction heating device is provided at a lower portion of the heating cooker and a magnetron is provided at a side portion.

In patent documents 1 to 3, in addition to heating by microwaves, a heating mechanism by electromagnetic induction is provided, whereby grill cooking can be performed.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 1-107016

Patent document 2: japanese patent laid-open No. 4-65097

Patent document 3: japanese patent laid-open No. 2013-122933

Disclosure of Invention

Problems to be solved by the invention

However, in patent documents 1 to 3, since the circuit for generating microwaves and the circuit for causing current to flow through the coil for electromagnetic induction heating are separately designed, respectively, 2 or more switches are required, and the structure becomes complicated.

Further, since the current penetration depth of electromagnetic induction is small as the frequency becomes higher, the same frequency band as that of microwaves cannot be used, and as a result, since 2 kinds of oscillators for electromagnetic induction and microwaves are prepared, respectively, the economy is poor and miniaturization is difficult.

The invention provides a defrosting heating cooker which can simplify the structure and restrain the enlargement of the device.

Means for solving the problems

In order to achieve the above object, the present invention is characterized by comprising: a pair of electrodes for thawing the object to be heated in the heating chamber by dielectric heating; a heating coil for induction-heating the object to be heated thawed by dielectric heating of the pair of electrodes; and a changeover switch that changes over electric power supplied to the pair of electrodes or the heating coil.

Effects of the invention

According to the present invention, it is possible to provide a defrosting heating cooker that uses dielectric heating and induction heating in the same frequency band, and therefore can share a circuit, simplify the structure, and suppress the enlargement of the device.

Drawings

Fig. 1 is a general configuration diagram of a defrosting heating cooker according to embodiment 1 of the present invention.

Fig. 2 is a diagram showing time series data of each part voltage and each part temperature shown in fig. 1.

Fig. 3 is a sectional view (partially extracted) of a cooking container according to embodiment 1 of the present invention.

Fig. 4 is a diagram showing the direction (electric lines of force) of an electric field generated between a pair of electrodes.

Fig. 5 is a general configuration diagram of a defrosting heating cooker according to embodiment 2 of the present invention.

Fig. 6 is a diagram showing the direction (electric lines of force) of an electric field generated between the electrode and the heating coil of fig. 5.

Fig. 7 is a general configuration diagram of a defrosting heating cooker according to embodiment 3 of the present invention.

Fig. 8 is a direction (electric lines of force) of an electric field generated between the electrode and the coil of fig. 7.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the same components, and the same description will not be repeated.

The various components of the present invention need not necessarily exist independently, and it is permissible that one component is constituted by a plurality of members, a plurality of components are constituted by one member, a certain component is a part of other components, a part of certain component is overlapped with a part of other components, and the like.

Example 1

Fig. 1 is a general configuration diagram of a defrosting heating cooker according to embodiment 1 of the present invention. The defrosting heating cooker 100 is formed by a housing 4. The housing 4 is provided with a heating chamber 3 for accommodating a food material 6 (an object to be heated). The food material 6 in the heating chamber 3 is heated by induction heating or induction heating described later. The housing 4 is provided with an AC power outlet 70 that is led out to the outside. The AC power outlet 70 uses 100V-20A if it is for home use and 200V-15A if it is for commercial use. The AC power outlet 70 is connected to the converter circuit 60 via a power cord. The AC power supplied from the AC power outlet 70 is converted into dc by the converter circuit 60, and the converted dc is supplied to the inverter circuit 30 at the subsequent stage. The converter circuit 60 is controlled by a converter circuit driving signal 21 from the control circuit 20.

The inverter circuit is mainly composed of a smoothing capacitor 33 for smoothing a waveform deformed by direct current, an upper arm semiconductor 31, and a lower arm semiconductor 32. The upper arm semiconductor 31 and the lower arm semiconductor 32 are connected in parallel with the transistor by reverse conduction of the diode. The transistor is shown here as an example of a MOS (Metal Oxide Semiconductor: metal oxide semiconductor), but may be, for example, an IGBT (Insulated Gate Bipolar Transistor: insulated gate bipolar transistor).

The upper arm semiconductor 31 and the lower arm semiconductor 32 perform switching operation so as to be alternately turned ON (ON)/OFF (OFF) and turned OFF/ON, and the timing thereof is controlled by a gate signal transmitted from the driving circuit 10. The drive circuit 10 is controlled by a drive control signal 23 from the control circuit 20.

The latter stage branch of the inverter circuit 30 is an impedance matching circuit 40 and a change-over switch semiconductor 50 (change-over switch). A pair of electrodes (positive electrode 1a and negative electrode 1 b) are connected to the impedance matching circuit 40, and the heating coil 2 is connected to the switching semiconductor 50. That is, the inverter circuit 30 is connected in parallel with the pair of electrodes (positive electrode 1a, negative electrode 1 b) and the heating coil 2 via the switching semiconductor 50 (switching).

Here, the switching semiconductor 50 may be a transistor similar to the transistors of the upper and lower arm semiconductors 31 and 32 in the inverter circuit 30.

When the switching semiconductor 50 is turned on, a current flows in the resonant capacitor 51 and the heating coil 2 in the heating chamber 3, and when turned off, an electric field E is applied between the positive electrode 1a and the negative electrode 1b in the heating chamber 3. The electric field E is obtained from the voltage difference V between the electrodes and the inter-electrode distance X, and from e=v/X. The state of the power line at this time is shown in fig. 4.

Fig. 4 is a diagram showing the direction (electric lines of force) of an electric field generated between a pair of electrodes. As shown in fig. 4, the electric field lines 1c are generated from the positive electrode toward the negative electrode. The food material 6 is dielectrically heated by being placed in the electric field. However, when the food 6 enters the heating chamber 3, the impedance in the heating chamber 3 varies depending on the height and dielectric constant of the food 6, and thus the control circuit 20 controls the output to the food to be maximum by adjusting the values of the variable choke 41 and the variable capacitor 42 in the impedance matching circuit 40. This can realize dielectric heating and uniformly defrost the food.

The heating chamber 3 is provided with sensors for measuring the states of the respective parts (in particular, the electrodes, the surface of the food), such as the temperature and the voltage, and the measurement data 22 of the state in the heating chamber measured by the sensors is sent to the control circuit 20. When the value measured by the sensor exceeds a preset threshold value, the control circuit 20 determines that the switching semiconductor 50 is to be changed from off to on.

When the switching semiconductor 50 is turned on, a current flows on the heating coil 2 side where the impedance is small. When a current flows through the heating coil 2, a magnetic field 9 is generated. Since this magnetic field 9 also penetrates the cooking container 7, eddy current is generated in the cooking container 7 and the negative electrode 1b in a direction to cancel the magnetic field 9. If eddy current is induced, joule heat is generated, and as a result electromagnetic induction heating can be achieved. Then, the food 6 is grill-cooked by electromagnetic induction heating.

Fig. 2 is a diagram showing time series data of each part voltage and each part temperature shown in fig. 1. The upper arm semiconductor 31a and the lower arm semiconductor 31b in the inverter circuit are always switched in a phase-inverted state. In FIG. 2, the temperature at the negative electrode exceeds T _th Time t of (2) ₀ The switching semiconductor 50 is changed from off to on. In order to prevent the allowable temperature of the electrode itself and excessive heating of the food, when the monitored negative electrode temperature indicates an abnormal value, control is performed to stop the switching operation of the semiconductor in the inverter circuit so as to stop all the operations.

Embodiment 1 is characterized in that a defrosting heating cooker is provided with a pair of electrodes (positive electrode 1a and negative electrode 1 b) for dielectric heating and a heating coil 2 for electromagnetic induction heating. The power supply to the pair of electrodes for dielectric heating and the heating coil 2 for electromagnetic induction heating is performed by the common inverter circuit 30, and the power supply destination is switched by on/off of the 1-switch semiconductor 50.

The dielectric heating and induction heating in example 1 used high frequencies of 1 to 100 MHz. Preferably, ISM bands (SAW: industrial Sciencic and Medical Band industrial scientific and medical bands) such as 13.56MHz, 27.12MHz, 40, 68MHz, etc. are used as the common high frequency band.

According to embodiment 1, the power supply for dielectric heating and electromagnetic induction heating is performed by the common inverter circuit 30, and the power supply destination is switched by on/off of the 1-switch semiconductor 50, so that the device can be suppressed from being enlarged. In addition, since the apparatus is simplified, an increase in product cost can be suppressed.

Here, in order to defrost and heat a series of operations safely and stably without generating spark discharge or the like, the positive electrode 1a, the negative electrode 1b, and the metal portions of the heating coil 2 are coated or molded with the insulating material 8 in the heating chamber 3 so as not to be exposed. The insulating material 8 is, for example, ceramic or resin.

In addition, in example 1, since thawing is performed by dielectric heating and grill cooking is performed by electromagnetic induction heating, countermeasures for suppressing spark discharge are also required for the cooking container 7. Fig. 3 is a sectional view (partially extracted) of a cooking container according to embodiment 1 of the present invention.

In fig. 3, a cooking container 7 is formed of a metal material 5a as a base material of the cooking container 7, and a surface of the metal material 5a is coated with a non-metal material 5 b. The material of the metal material 5a is preferably a magnetic material, and for example, iron, ferritic stainless steel, or the like is used. The nonmetallic material 5b is preferably an insulating material such as resin or ceramic.

In the cooking container 7 of example 1, since spark discharge can be suppressed, in a state where food is placed, grill cooking from thawing by dielectric heating to electric induction heating can be performed, and operability can be improved.

Example 2

Next, example 2 of the present invention will be described. Fig. 5 is a general configuration diagram of a defrosting heating cooker according to embodiment 2 of the present invention. In example 1 (fig. 1), the heating coil 2 is provided below the negative electrode 1b, but in example 2, the heating coil 2b is disposed on the negative electrode 1b, and further 1 selector switch is added on the lower arm side.

The switch semiconductor 50 (switch) of example 1 (fig. 1) corresponds to the switch semiconductor (upper arm side) 50a in the present figure, and further, the switch semiconductor (lower arm side) 50b is added downstream of the coil in example 2.

As shown in fig. 5, by bringing the heating coil 2 close to the food 6 and the cooking container 7, the coupling with the magnetic field 9 can be further enhanced, and therefore, the grill heating time by electromagnetic induction can be shortened.

Fig. 6 is a diagram showing the direction (electric lines of force) of an electric field generated between the electrode and the heating coil of fig. 5. Here, the switch semiconductor (upper arm side) 50a and the switch semiconductor (lower arm side) 50b are schematically shown as switches.

The switch semiconductor (upper arm side) 50a is turned off at the time of dielectric heating in the defrosting process, and is turned on at the time of induction heating in the grill heating process, and thus operates in the same manner as the switch semiconductor 50 shown in embodiment 1.

On the other hand, the change-over switch semiconductor (lower arm side) 50b is turned on at the time of induction heating in the grill heating step, but is operated both on and off at the time of dielectric heating in the defrosting step. That is, the heating coil 2b functions as a negative electrode. When the switching semiconductor (lower arm side) 50b is turned on during dielectric heating in the defrosting step, the distribution of the power line 1c concentrated toward the center of the coil is shown in fig. 6. This is because the heating coil 2b (also referred to as a negative electrode) itself has a shape like a monopole antenna, and is therefore effective when it is desired to defrost only the center of the food (for example, when the area of the electrode is small and thawing is desired in a short time) with respect to the food.

In addition, although not shown, when the switching semiconductor (lower arm side) 50b is turned off during dielectric heating in the defrosting step, the heating coil 2b becomes substantially electrically floating, and thus an electric field having electric lines of force substantially parallel to each other is formed between the positive electrode 1a and the negative electrode 1b shown in fig. 4. In the case of the same distribution of electric lines of force as in example 1, it is effective when it is desired to uniformly defrost the entire electrode.

According to embodiment 2, the common inverter circuit 30 supplies electric power for dielectric heating and electromagnetic induction heating, and the on/off of the switching semiconductors 50a and 50b is switched to switch the electric power supply destination, so that the device can be prevented from being enlarged.

Example 3

Next, example 3 of the present invention will be described. Fig. 7 is a general configuration diagram of a defrosting heating cooker according to embodiment 3 of the present invention. In example 3, the change-over switch semiconductor (upper arm side) 50a and the positive electrode 1a in example 2 (fig. 5) were removed, and the heating coil 2a was integrated with the function of the positive electrode. That is, embodiment 3 is characterized in that any one of the pair of electrodes is used as a heating coil.

As a result, in example 3, the number of components was minimized as compared with example 1 and example 2, and as a result, the assembly performance was improved, and the failure rate of each component (=the product life was improved) was reduced. Further, since the distribution cable to be introduced into and withdrawn from the heating chamber can be minimized, the mutual wiring inductance between the positive electrode and the negative electrode can be reduced by effectively using coaxial cables, twisted wires, bus bars (bus bars), and the like, and electromagnetic field leakage can be suppressed.

Fig. 8 is a direction (electric lines of force) of an electric field generated between the electrode and the coil of fig. 7. Since the heating coil 2a (also referred to as a positive electrode) itself has a shape like a monopole antenna, it is effective when the center of the food is to be thawed only in a concentrated manner (for example, when the area of the electrode is small and the food is to be thawed in a short time).

According to embodiment 3, in addition to the effect of embodiment 1, the heating coil 2a also serves as a positive electrode, so that the number of components can be reduced, and the assembling property can be improved. Furthermore, according to embodiment 3, the failure rate can be reduced by reducing the number of components.

The present invention is not limited to the above-described embodiments, but includes various modifications. The embodiments described above are described in detail for the purpose of easily understanding the present invention, and are not limited to the embodiments having all the configurations described.

Description of the reference numerals

1 … electrode, 1a … positive electrode, 1b … negative electrode, 1c … power line, 2 … heating coil, 2a … heating coil (double positive electrode), 2b … heating coil (double negative electrode), 3 … heating chamber, 4 … housing, 5a … metallic material, 5b … nonmetallic material, 6 … food material, 7 … cooking vessel, 8 … insulating material, 9 … magnetic field, 10 … drive circuit, 20 … control circuit, 21 … converter circuit drive signal, 22 … heating chamber internal state measurement data, 23 … drive control signal, 30 … inverter circuit, 31 … upper arm semiconductor, 32 … lower arm semiconductor, 33 … smoothing capacitor, 40 … impedance matching circuit, 41 … variable choke, 42 … variable capacitor, 50 … switch semiconductor, 51 … resonant capacitor, 60 … converter circuit, 70 … AC power socket, 100 … defrost cooking vessel.

Claims

1. A defrosting heating cooker is characterized in that,

the defrosting heating cooker comprises:

a pair of electrodes for thawing the object to be heated in the heating chamber by dielectric heating;

a heating coil for induction-heating the object to be heated thawed by dielectric heating of the pair of electrodes; and

and a change-over switch for switching the electric power supplied to the pair of electrodes or the heating coil.

2. The defrosting heating cooker as claimed in claim 1, wherein,

the heating coil is disposed below an electrode disposed below the pair of electrodes.

3. The defrosting heating cooker as claimed in claim 1, wherein,

the heating coil is disposed between the pair of electrodes.

4. The defrosting heating cooker as claimed in claim 2 or 3, wherein,

the defrosting heating cooker comprises:

a converter circuit that converts alternating current into direct current; and

an inverter circuit connected to the converter circuit and having an upper arm semiconductor and a lower arm semiconductor for performing switching operation,

the inverter circuit is connected in parallel with the pair of electrodes and the heating coil via the change-over switch.

5. The defrosting heating cooker as claimed in claim 1, wherein,

the defrosting heating cooker uses either one of the pair of electrodes as the heating coil.

6. The defrosting heating cooker as claimed in any one of claims 1 to 5, wherein,

the thawing and heating cooker comprises a cooking container for placing the heated object,

the cooking container is composed of a metal material of a magnetic body and a nonmetallic material coated on the surface of the metal material.