JP2018108311A - rice cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rice cooker in which materials to be cooked inside an inner pot are subjected to complicated convective flows and uneven cooking of rice inside a pot is reduced, while it has a simple structure having only single heating means.SOLUTION: A rice cooker includes: a heating coil heating an inner pot; and an invertor supplying the heating coil with power. The inner pot is constituted of a magnetic material part and a non-magnetic material part. The invertor supplies the heating coil with power by performing switching between a low-frequency drive mode for supplying a currency of a low-frequency and a high-frequency drive mode for supplying a current of a high-frequency.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electromagnetic induction heating rice cooker mainly used at home.

  In recent years, the electromagnetic induction heating method has become mainstream as a heating method for rice cookers, and as an inner pot used for the rice cooker, a magnetic material induction-heated by an induction heating coil is used on the outside, and the heat generation of the magnetic material Some of them use a non-magnetic material such as aluminum with good thermal conductivity that uniformly conveys to the rice in the inner pot. In general, the inner pot is heated by electromagnetic induction with an induction heating coil provided facing the bottom of the inner pot to obtain strong convection inside the inner pot and cook rice.

  For example, in FIG. 1 and claim 1 of Patent Document 1, “a pot for putting an object to be cooked, a first heating means for heating the bottom side surface of the pot, and a second for heating the bottom surface of the pot. A heating means; and a control means for controlling the first heating means and the second heating means. The control means alternately switches both the heating means and energizes the first heating means. A rice cooker is disclosed in which a predetermined pause time is provided in which the convection caused by inertia of the convection caused by the heating means is subsided and convection in the opposite direction can be caused by the second heating means.

  In other words, Patent Document 1 includes a first heating means for heating the bottom side surface portion of the inner hook and a second heating means for heating the bottom surface portion of the inner hook, and the plurality of heating means are alternately arranged. There has been disclosed a rice cooker that obtains intense convection by changing the convection direction of the cooking object in the inner pot by energizing.

  Further, in FIG. 5 and paragraphs 0043 to 0045 of Patent Document 2, “the lines of magnetic force generated by the induction heating coils 10a, 10b, and 10c tend to gather at locations protruding close to the induction heating coils 10a, 10b, and 10c. More eddy current flows in the part and the heat is strongly generated. ”,“ For that reason, the part where the magnetic member 20 is joined at the time of rice cooking quickly generates heat and is joined to the part where the magnetic member 20 is joined. A temperature difference occurs in a part that does not exist, and bubbles are generated from the part where the inner surface of the inner pot heats up quickly. As the bubbles rise or burst, convection occurs in the cooked rice and water. "," Further, the location where the magnetic member 20 is joined is the sum of the thickness of the inner hook 6 and the thickness of the magnetic member 20, and the volume of the metal is increased, so that the location where the magnetic member 20 is not joined is compared. Heat capacity When the temperature difference is maintained, the difference in the generation of bubbles due to the temperature difference is also maintained, and the convection is further promoted, whereby the whole is heated uniformly and cooking with less uneven cooking is possible. Is possible. "

  That is, in Patent Document 2, a separate magnetic member is joined to the bottom of the outer surface of the inner hook, the magnetic member is heated strongly by approaching the electromagnetic induction heating coil, and the magnetic member is joined to the place where the magnetic member is joined. There is disclosed a rice cooker that promotes convection due to a temperature difference from a portion that is not.

Japanese Patent No. 3695122 Japanese Patent Laying-Open No. 2015-188491

  In Patent Document 1 and Patent Document 2 described above, rice can be cooked while forming an appropriate convection in the inner pot, but there are the following problems.

  The rice cooker disclosed in Patent Document 1 has a problem that since it has a plurality of heating coils, the components and circuit wiring of the rice cooker become complicated, and the manufacturing cost associated therewith increases.

  Moreover, in the rice cooker disclosed in Patent Document 2, since the heat generating part of the inner pot cannot be changed dynamically and the direction of convection cannot be switched, a large convection cannot be obtained, and the cooking unevenness still remains. There is a problem that will occur.

  An object of the present invention is to provide a rice cooker that has a simple configuration having only a single heating coil as a heating means, and that convections the food in the inner pot in a complex manner, thereby reducing rice cooking unevenness. It is to be.

  In order to solve the above problems, a rice cooker of the present invention includes a heating coil that heats an inner pot, and an inverter that supplies electric power to the heating coil, and the inner pot includes a magnetic material portion and a nonmagnetic material. The inverter is configured to supply power to the heating coil by switching between a low frequency driving mode for supplying a low frequency current and a high frequency driving mode for supplying a high frequency current.

  According to the present invention, there is provided a rice cooker that has a simple structure having only a single heating coil as a heating means, and convections the food in the inner pot in a complicated manner to reduce rice cooking unevenness in the pot. can do.

Basic configuration diagram of rice cooker of Example 1 (A) Sectional view of inner pot and heating coil of rice cooker of Example 1, (b) Bottom view of inner pot Graph showing the relationship between the input power to the inverter and the coil current frequency Graph showing the frequency of current flowing in the heating coil (A) Convection direction during low frequency drive mode, (b) Convection direction during high frequency drive mode during rice cooking in Example 1 (A) Convection direction in low-frequency drive mode, (b) Convection direction in high-frequency drive mode, (c) Bottom view of inner pot during rice cooking in Example 2 (A) Convection direction in low frequency drive mode, (b) Convection direction in high frequency drive mode, (c) Top view of inner pot during rice cooking of Example 3 Example 4 (a) Convection direction in low frequency drive mode, (b) Convection direction in high frequency drive mode, (c) Bottom view of inner pot during rice cooking of Example 4 The graph which shows the frequency of the electric current which flows into the heating coil of Example 5. The graph which shows the frequency of the electric current which flows into the heating coil of Example 6. Relationship between coil current frequency and pot temperature in Example 7

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a basic configuration diagram of a rice cooker according to a first embodiment of the present invention. The rice cooker 100 includes an inner pot 1, an annular heating coil 2 that heats the inner pot 1, and an inverter 3 that supplies power input from the AC power supply 4 to the heating coil 2. The inner hook 1 generates an eddy current when an alternating magnetic flux generated from a heating coil 2 provided facing the bottom of the inner hook 1 is applied, and generates heat by the electric resistance of the inner hook itself.

  FIG. 2A shows a cross-sectional structure of the inner hook 1 in this embodiment, and FIG. 2B shows a bottom view of the inner hook 1 in this embodiment. In the present embodiment, the inner pot 1 is composed of a magnetic material 11 such as iron on the side surface and a nonmagnetic material 12 such as aluminum or copper on the bottom. The main magnetic flux 21 generated from the heating coil 2 forms a magnetic path so as to be linked to both the side magnetic material and the bottom nonmagnetic material.

  Here, the electric power P applied to the inner hook 1 is expressed by Equation 1 using the resistance R of the inner hook and the current I flowing through the inner hook.

  From Equation 1, when the resistance of the inner hook is 0Ω (short circuit), the power applied to the inner hook is zero. On the other hand, when the resistance of the inner hook is ∞ (open), no current flows through the inner hook, so the power applied to the inner hook is zero. That is, the resistance value of the inner hook needs to be set to an appropriate value between 0 and ∞.

  Table 1 shows the magnetic permeability and electrical resistivity of aluminum as a typical example of a nonmagnetic material, and the magnetic permeability and electrical resistivity of a magnetic material, the skin depth when a current of 20 kHz flows in each material, and the frequency of 80 kHz in each material. Each skin depth when current flows is shown.

  Here, the skin depth d is expressed by Equation 2 using the frequency f, the magnetic permeability μ, and the electrical resistivity ρ.

  As shown in Table 1, since aluminum has a permeability of 1/1000 or less compared to iron, the skin depth becomes deeper than iron when an alternating magnetic flux having the same frequency is applied. As a result, since the cross-sectional area of the current flowing through the hook is wide due to the magnetic flux applied from the heating coil, the effective resistance value is reduced and the heat generation is also reduced. That is, in order to heat aluminum like iron, it is necessary to apply an AC magnetic flux having a frequency higher than that of iron.

  In products such as IH cooking heaters, a system that can heat both an aluminum pan and an iron pan with a single inverter is known. FIG. 3 shows the relationship between the frequency of the current flowing in the hook and the electric power applied to the hook when the current resonance type inverter is applied to the inverter and the aluminum pot and the iron pot are heated. As shown here, when heating an aluminum pot, which is a non-magnetic material, aluminum has a lower resistance than iron, so the frequency of the current flowing through the hook is increased and the effective resistance of the pot is increased by the skin effect. It is necessary to apply sufficient power to the hook. On the other hand, when heating an iron pan that is a magnetic material, iron has a higher resistance than aluminum, so even if the frequency of the current flowing through the kettle is lower than that of the aluminum pan, sufficient power can be applied to the pan. . In general, in an electromagnetic induction heating device, in order to obtain an effect of increasing resistance due to the skin effect, an aluminum kettle is heated at a frequency of 60 kHz or higher (for example, 80 kHz) and an iron kettle is heated at a frequency of 60 kHz or lower (for example, 20 kHz). It has been known.

  FIG. 4 shows the frequency of the current flowing through the heating coil 2 in this embodiment. As shown in FIG. 4, in this embodiment, the inverter outputs a current having a frequency lower than a threshold frequency fth (for example, 60 kHz) to the heating coil, and a current having a frequency higher than the threshold frequency fth. The high-frequency drive mode output to is alternately repeated. Thereby, in the low frequency drive mode, the magnetic material 11 is heated, and in the high frequency drive mode, the nonmagnetic material 12 is heated. Here, in the low-frequency drive mode, the nonmagnetic material 12 has a small resistance value and no power is applied because the resistance increase due to the skin effect is small. On the other hand, in the high frequency drive mode, the magnetic material 11 is greatly affected by the increase in resistance due to the skin effect, and therefore the resistance value is large and no current flows and no power is applied. That is, the inverter alternately repeats the low-frequency drive mode and the high-frequency drive mode, whereby the heating part is alternately changed between the side surface and the bottom portion, and the direction of convection in the inner pot 1 can be switched.

  Here, FIG. 5A shows the convection direction of the object to be heated in the low frequency driving mode, and FIG. 5B shows the convection direction of the object to be heated in the high frequency driving mode. As shown in FIG. 5A, since the magnetic material 11 on the side surface of the inner hook 1 is heated in the low-frequency driving mode, the convection that floats along the side surface and descends through the center in the inner hook. Will occur. On the other hand, as shown in FIG. 5B, in the high-frequency driving mode, the nonmagnetic material 12 on the bottom surface of the inner pot 1 is heated, so that it floats through the center and descends along the side surface. Convection occurs.

  As described above, in the present embodiment, it is possible to alternately generate convection of the food to be cooked inside the inner pot while using only a single heating coil 2, and cooking while having a simple structure. Cooked rice with reduced unevenness can be realized. In this embodiment, the magnetic material 11 is disposed on the side surface of the inner hook 1 and the non-magnetic material 12 is disposed on the bottom surface of the inner hook 1 as an example. However, these positional relationships are reversed. Even in such a case, it goes without saying that the same effect can be obtained only by reversing the combination of the driving mode and the convection direction shown in FIG.

  Next, Example 2 will be described. In this embodiment, the structure of the inner hook 1 is different from that of the first embodiment. However, since other points such as the operation mode of the inverter are the same as those of the first embodiment, the redundant description is omitted.

  FIG. 6A and FIG. 6B are views showing a cross-sectional structure of the inner hook 1 in the present embodiment. Moreover, FIG.6 (c) is a bottom view of the inner hook 1 in a present Example. The inner hook 1 of the present embodiment has a configuration in which a base plate made of a nonmagnetic material 12 is provided on the bottom and side surfaces, and the magnetic material 11 is disposed on the outer side surface of the base plate. The main magnetic flux 22 generated from the heating coil 2 forms a magnetic path so as to be linked to both the side magnetic material and the bottom nonmagnetic material. The inner hook 1 of this embodiment shown in FIG. 6 only needs to form a substantially plate-like magnetic material 11 on the outside of the base plate of the non-magnetic material 12 that has been pressed. It is superior in workability compared to the inner pot 1 shown.

  Here, FIG. 6A shows the convection direction of the object to be heated in the low frequency driving mode in this embodiment, and FIG. 6B shows the convection direction of the object to be heated in the high frequency driving mode in this embodiment. Each is shown. As shown in FIG. 6A, since the magnetic material 11 on the side surface of the inner hook 1 is heated in the low frequency driving mode, the path that floats along the side surface and descends through the center in the inner hook. Convection occurs at On the other hand, as shown in FIG. 6B, in the high-frequency driving mode, the nonmagnetic material 12 on the bottom surface of the inner pot 1 is heated, so that it floats in the inner pot through the center and descends along the side surface. Convection occurs in the path that goes through.

  As described above, by using the inner hook of this embodiment, in addition to realizing the convection control equivalent to that of the first embodiment, the hook configuration having superior processability such as thermal spraying and cold spraying compared to the first embodiment, Become. As in the case of Example 1, it goes without saying that the same effect can be obtained in this example even when the positional relationship between the magnetic material 11 and the nonmagnetic material 12 is reversed.

  Next, Example 3 will be described. In the present embodiment, the structure of the inner hook 1 is different from those in the first and second embodiments. However, since other points such as the operation mode of the inverter are the same as those in the first embodiment, the redundant description is omitted.

  FIGS. 7A and 7B are views showing a cross-sectional structure of the inner hook 1 in the present embodiment. Moreover, FIG.7 (c) is a top view of the inner hook 1 in a present Example. In this embodiment, the inner hook 1 has a base plate made of a nonmagnetic material 12 on the bottom surface and side surfaces, and a plurality of annular magnetic materials 11 are concentrically arranged on the inner bottom surface of the base plate. The main magnetic flux 23 generated from the heating coil 2 forms a magnetic path so as to interlink with the base plate of the nonmagnetic material and the magnetic material in the inner pot. In this way, by configuring the plurality of annular magnetic materials 11 on the inner side, the inner hook 1 of this embodiment shown in FIG. 7 generates more complicated convection than the hook shown in FIGS.

  Here, FIG. 7A shows the convection direction of the object to be heated in the low frequency driving mode in this embodiment, and FIG. 7B shows the convection direction of the object to be heated in the high frequency driving mode in this embodiment. Respectively. As shown in FIG. 7 (a), in the low frequency drive mode, the plurality of annular magnetic materials 11 are heated, so that the portion where the magnetic material 11 is disposed rises in the vertical direction in the inner pot, and the magnetic material Convection occurs in a path descending through a portion where 11 is not arranged. On the other hand, as shown in FIG. 7B, in the high frequency drive mode, the non-magnetic material 12 is heated, so that a portion where the magnetic material 11 is not disposed in the inner pot rises in the vertical direction. Convection occurs in a path descending through a portion where 11 is disposed.

  As described above, in this embodiment, a complicated convection can be achieved by arranging the magnetic material on either the outer surface or the inner surface of the inner hook, and further, the magnetic material can be selectively disposed in the first embodiment. A more complex convection than in Example 2 is obtained. Needless to say, the same effect can be obtained even when the positional relationship between the magnetic material 11 and the nonmagnetic material 12 is reversed in this embodiment.

  Next, Example 4 will be described. In this embodiment, the structure of the inner hook 1 is different from those of the first to third embodiments. However, since the other points such as the operation mode of the inverter are the same as those of the first embodiment, the duplicated explanation is omitted.

  FIGS. 8A and 8B are views showing a cross-sectional structure of the inner hook 1 in the present embodiment. Moreover, FIG.8 (c) is a bottom view of the inner hook 1 in a present Example in a present Example. In this embodiment, the inner hook 1 includes a base plate made of a nonmagnetic material 12 on the bottom surface and side surfaces, the magnetic material 11 is disposed on the outer side surface of the base plate, and a plurality of annular shapes are disposed on the outer bottom surface of the base plate. The magnetic material 11 is concentrically arranged. The main magnetic flux 24 generated from the heating coil 2 forms a magnetic path so as to interlink with both the base plate of the nonmagnetic material and the magnetic material disposed on the outer side surface and the outer bottom surface. In this way, by selectively placing the magnetic material on the outer bottom surface of the hook shown in FIG. 6, the inner hook 1 of this embodiment shown in FIG. 8 is more complicated than the hook shown in FIGS. Produce.

  Here, FIG. 8A shows the convection direction of the object to be heated in the low frequency driving mode in this embodiment, and FIG. 8B shows the convection direction of the object to be heated in the high frequency driving mode in this embodiment. Respectively. As shown in FIG. 8A, in the low frequency driving mode, the magnetic material 11 disposed on the side surface and the plurality of annular magnetic materials 11 disposed on the bottom surface are heated. After levitation along the line, both the convection descending through the center and the convection rising in the vertical direction at the portion where the magnetic material 11 is disposed and descending through the portion where the magnetic material 11 is not disposed are combined. Convection occurs. On the other hand, as shown in FIG. 8B, in the high frequency driving mode, since the nonmagnetic material 12 is heated, the convection that floats through the center and then descends along the side surface in the inner pot, and magnetic A convection is generated in which the portion where the material 11 is not arranged rises in the vertical direction and the convection descends through the portion where the magnetic material 11 is arranged.

  As described above, in this embodiment, a complicated convection is possible by arranging a magnetic material on either the outer surface or the inner surface of the inner hook, and further by selectively arranging the magnetic material on both the side surface and the bottom surface. More complicated convection is obtained than in the first to third embodiments. Needless to say, the same effect can be obtained even when the positional relationship between the magnetic material 11 and the nonmagnetic material 12 is reversed in this embodiment.

  Next, Example 5 will be described. In the present embodiment, the structure of the inner hook 1 may be any of the first to fourth embodiments, but the inverter operation is different from that shown in FIG. 4 of the first embodiment, and the low frequency driving mode and the high frequency driving mode are different. Is provided with a stop period.

  FIG. 9 shows the frequency of the current flowing through the heating coil 2 in this embodiment. As shown in FIG. 9, in this embodiment, the inverter outputs a current having a frequency lower than the threshold frequency fth to the heating coil, and a high frequency drive outputs a current having a frequency higher than the threshold frequency fth to the heating coil. The inverter repeats the mode, and further, between the low frequency drive mode and the high frequency drive mode, the inverter provides a stop period during which no current flows through the heating coil.

  By providing the stop period, convection occurs in the high frequency drive mode after the convection that has occurred in the low frequency drive mode is settled, so the convection efficiency of the cooked material is improved compared to the rice cooker described in the first embodiment. Moreover, power consumption can be suppressed as the whole rice cooker.

  Next, Example 6 will be described. In the present embodiment, the structure of the inner hook 1 may be any of the first to fourth embodiments, but the inverter operation differs from that shown in FIG. 4 of the first embodiment or FIG. Is continuously changed.

  FIG. 10 shows the frequency of the current flowing through the heating coil 2 in this embodiment. As shown in FIG. 10, in this embodiment, the inverter outputs a current having a frequency lower than the threshold frequency fth to the heating coil, and a high frequency drive outputs a current having a frequency higher than the threshold frequency fth to the heating coil. The mode is repeated and the frequency is continuously changed over time.

  By continuously changing the time, the cooked food inside the kettle convects more smoothly. Therefore, compared to the rice cooker described in Example 1, the convection efficiency of the cooked food is improved, and the cooker as a whole is cooked. Also, power consumption can be suppressed.

  Next, Example 7 will be described. In the present embodiment, the operation mode of the inverter will be described through the period from the start of rice cooking to the end of rice cooking in any of the rice cookers shown in Examples 1 to 6.

First, as shown in FIG. 1, the rice and water are placed in any of the pots shown in the first to fourth embodiments. When rice cooking is started, as shown in FIG. 11, the temperature inside the kettle is raised to an appropriate temperature (for example, 55 ° C.), and a soaking process is performed in which the rice sucks water. In the dipping process, the low frequency driving period t ₁₁ , the high frequency driving period t ₁₂ , and the stop period t ₁₃ are sequentially repeated, so that the water can be uniformly immersed. It is also possible to adjust the length of _{t 11, t 12, t 13} according to the amount of the food.

After the soaking process is completed, a cooking process is performed to boil the interior. In the cooking process, since it is necessary to increase the temperature in the pot vigorously, the low frequency driving mode t ₂₁ and the high frequency driving mode t ₂₂ described in the first embodiment are alternately repeated without providing a stop period. It should be noted that the lengths of t ₂₁ and t ₂₂ may be adjusted in order to adjust the cooking finish of the food to be cooked, and the case where the convection of the food to be cooked and further cooking unevenness reduction is aimed at is described in Example 5. The inverter drive mode may be applied.

After the cooking process is completed, a boiling process is performed in which the boiling state is maintained and gelatinization of the rice is promoted. In the boiling process, the inside of the kettle is heated to 100 ° C. or higher (eg, 105 ° C.) because the kettle is boiled with pressure applied. In the boiling process, it is necessary to maintain the temperature in the kettle at a high temperature, and no low period is provided, and the low frequency drive mode t ₃₁ and the high frequency drive mode t ₃₂ described in the first embodiment are alternately repeated. It should be noted that the lengths of t ₃₁ and t ₃₂ may be adjusted in order to adjust the cooking finish of the food to be cooked. The inverter drive mode may be applied.

After the boiling process is completed, a steaming process is performed to promote gelatinization of the rice inside the kettle. In the steaming process, the low-frequency drive mode t ₄₁ , the high-frequency drive mode t ₄₂ , and the stop period t ₄₃ are alternated so that the temperature inside the kettle that has risen in the boiling process is maintained at a constant level due to residual heat. Repeat. It is also possible to adjust the length of _{t 41, t 42, t 43} according to the amount of the food.

  According to the rice cooking control of the present embodiment described above, the convection direction in each step can be appropriately controlled, so that rice cooking with less unevenness can be realized.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is possible to add, delete, and replace other configurations with respect to the configuration of each embodiment.

100 rice cooker,
DESCRIPTION OF SYMBOLS 1 Inner hook 2 Heating coil 3 Inverter 4 AC power supply 11 Magnetic material 12 Nonmagnetic material 21, 22, 23, 24 Main magnetic flux

Claims (7)

A heating coil for heating the inner pot;
An inverter for supplying electric power to the heating coil,
The inner hook is composed of a magnetic material part and a non-magnetic material part,
The inverter is configured to supply power to the heating coil by switching between a low frequency driving mode for supplying a low frequency current and a high frequency driving mode for supplying a high frequency current. In the rice cooker according to claim 1,
In the low frequency drive mode, the magnetic material part is heated,
A non-magnetic material portion is heated in the high-frequency driving mode. In the rice cooker according to claim 1 or 2,
The inverter is
In the high frequency driving mode, a current of 60 kHz or more is supplied,
In the low frequency drive mode, a current of less than 60 kHz is supplied. In the rice cooker as described in any one of Claims 1-3,
The said inverter has a stop period which stops this inverter between a high frequency drive mode and a low frequency drive mode, The rice cooker characterized by the above-mentioned. In the rice cooker according to any one of claims 1 to 4,
The inner pot is
Configuration with a magnetic material part on the side and a non-magnetic material part on the bottom, or
A rice cooker having a configuration in which a nonmagnetic material portion is disposed on a side surface and a magnetic material portion is disposed on a bottom portion. In the rice cooker according to any one of claims 1 to 4,
The inner pot is
A configuration in which a magnetic material portion is arranged on the outer surface of a non-magnetic material base plate, or
A rice cooker having a configuration in which a nonmagnetic material portion is disposed on an outer surface of a base plate made of a magnetic material. In the rice cooker according to any one of claims 1 to 4,
The inner pot is
A configuration in which a plurality of annular magnetic material portions are arranged on the bottom surface of a non-magnetic material base plate, or
A rice cooker having a configuration in which a plurality of annular nonmagnetic material portions are arranged on the bottom surface of a base plate of a magnetic material.

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