JPH09164056A - Electric rice cooker and pot for electric rice cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve heat efficiency by forming a heat conducting layer on the inside of an inner pot, and setting the heating layer on the outside to the thickness specific times the current infiltration depth of a magnetic material or above. SOLUTION: An inner pot 36 is provided with a heat conducting layer 36A on the inside and a heating layer 36B on the outside, the heating layer 36B made of a magnetic material is set to about 2.5 times the peculiar current infiltration thickness of a magnetic material or above in machining, and the heating layer 36B can be sufficiently secured. It is known that the heat efficiency is improved as the thickness (t) is increased and energy saving can be realized based on the current quantity It to the depth (t) from the surface obtained from equations I, II and the effective current ratio S at the thickness (t) obtained from equations III, IV. The heating layer 36B is made of 430 stainless steel with the thickness of 0.8mm, and the current infiltration depth δ of the 430 stainless steel is δ=0.28mm at the frequency of 20kHz. When efficiency is calculated, S=94.26% is obtained from the equations I-IV. In comparison with the inner pot 36 having the thickness of 0.55mm, the efficiency for the thickness of 0.55mm is S=85.97%, and efficiency is improved by 8.29%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric rice cooker that heats a pan for an electric rice cooker by an electromagnetic induction action, and a pan for the electric rice cooker.

[0002]

2. Description of the Related Art In recent years, electric rice cookers utilizing electromagnetic induction heating have been proposed. In FIG. 5, reference numeral 1 denotes a cylindrical main body having an open upper surface, and inside the main body 1, a protective frame 3 which is an inner pot storage portion is arranged via a heat insulating material 2, and the protective frame 3 is made of a non-metallic material. The material is formed into a bottomed cylindrical shape, and the upper end of the protective frame 3 is fitted around the inside of the upper end of the main body 1.

Reference numeral 4 denotes an inner pot which is a pot for an electric rice cooker having an outwardly projecting flange 5 formed therein. The inner pot has a heat-conducting layer 4A made of aluminum having high thermal conductivity, and a heat-conducting layer 4A. A heat-generating layer 4B made of a ferritic stainless steel, which is a magnetic metal material, located on the outer surface of the heat-conducting layer 4A is clad with a thickness about twice the current penetration thickness, and is used on the inner surface of the heat-conducting layer 4A. Has a fluorine coating 4C.

The inner pan 4 is detachably disposed in the protective frame 3 by mounting the flange 5 on the upper surface of the protective frame 3 in a suspended state. An induction coil 6 is provided outside the protection frame 3, and the induction coil 6 has a close innermost and outermost winding.

[0005] Further, the induction coil 6 is supported by a coil cover 7 formed of a heat-resistant resin material on the lower part of the outer periphery of the protective frame 3 so that the distance to the outer peripheral surface of the inner pot 4 is constant. . Below the induction coil 6, a ferrite rod 8 made of iron oxide as a main raw material and sintered with a material having a high magnetic permeability is located.
To prevent the magnetic flux generated from the induction coil 6 from leaking downward.

Reference numeral 9 denotes a thermo case formed of a heat-resistant resin. The thermo case 9 is supported by a guide tube 10 integrally formed on the outer bottom of the protective frame 3 so as to be able to move up and down. Compression coil spring 1 disposed between
1 is always biased upward. Reference numeral 12 denotes a contact made of aluminum. The contact 12 is fitted on the upper portion of the thermo case 9 via a temperature detecting element 13 composed of a negative temperature coefficient thermistor and a heat sensitive case 14. Crimping on the bottom.

[0007]

However, the clad material used for the inner pot 4 is inefficient because it cannot be efficiently converted into heat because the heat generating layer is not thick enough.

Further, it is generally known that by improving the heat conduction of the inner pot 4, it is possible to cook a delicious rice picture with uniform heat diffusion and less cooking unevenness. During the molding process, the heat-conducting layer and the heat-generating layer are easily separated from each other, and when the bottom of the pan is separated, the heat generated in the heat-generating layer is not sufficiently transferred to the heat-conducting layer. And the stability of rice cooking performance was insufficient.

Further, when deep drawing of ferritic stainless steel is performed, the surface of the stainless steel becomes rough like a shark skin, so a large-scale polishing process is required.

In view of the above problems, it is an object of the present invention to provide an electric rice cooker pot having improved thermal efficiency and improved rice cooking performance, and an electric rice cooker including the pot.

[0011]

In order to solve the above-mentioned problems, the present invention provides a main body, an inner pot removably housed in the main body, and a coil base made of a non-metal which surrounds the outer side of the inner pot. , An induction coil attached to the outer side of the coil base to heat the inner pot by electromagnetic induction, and a temperature detection device for contacting the inner pot to detect the temperature. Is formed of a heat generating layer that is a magnetic material, and the heat generating layer has a current penetration depth of approximately 2.
The thickness is five times or more.

[0012]

According to the first aspect of the present invention, a heat generating layer made of a magnetic material is processed to have a thickness of about 2.5 times or more of a current permeation thickness peculiar to the magnetic material. Can be secured. That is, the current amount of the surface obtained from equations 1 and 2 to the depth t I _t, and the active current ratio S in the sheet thickness t obtained from equation 3 and number 4,
As the thickness t becomes thicker, the thermal efficiency is improved, and energy saving can be realized.

[0013]

[Equation 1]

[0014]

(Equation 2)

[0015]

(Equation 3)

[0016]

(Equation 4)

According to a second aspect of the present invention, two heat generating layers are formed outside the heat conducting layer, and a magnetic material having a high magnetic coefficient is formed inside the two heat generating layers to improve workability. The heat conduction layer and the heat generation layer are not separated from each other, and the heat conduction can be improved.

According to the third aspect of the present invention, a heat generating layer is provided outside the heat conducting layer of the inner pot, and nickel is provided outside the heat conducting layer, whereby a large-scale polishing process for the outer surface of the inner pot can be eliminated and the manufacturing cost can be reduced. Can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. In the figure, reference numeral 30 denotes a substantially cylindrical main body having an open upper surface, and an upper frame 31 is fitted into an opening of the main body 30. Inside the main body 30, a protective frame body 32 made of a metal material and a coil base 33 are arranged to form a pot storage portion. The coil base 33 is formed of a non-metal material into a bottomed cylindrical shape.
The upper end portion of is fixed to the upper frame 31 via the protective frame body 32. A heat insulating wall 31 </ b> A is formed from the upper frame 31, and a heat insulating space 34 is formed between the upper frame 31 and the protective frame body 32. 3
Reference numeral 5 is a heat-retaining heater, which is fixed to the protective frame body 32 with aluminum tape.

Reference numeral 36 denotes an inner pot in which a flange 37 protruding outward is formed at the upper end opening. Here, the inner pot 36 is provided with a heat conducting layer 36A of aluminum t2.5 mm on the inner side and a heat generating layer 36B on the outer side, and further, a fluorine coating 36C is applied to the inner surface of the heat conducting layer 36A. This inner pot 36
The heat generating layer 36B is made of 430 stainless steel having a thickness of 0.8 mm, and the current penetration depth δ of this 430 stainless steel is δ = 0.28 mm at a frequency of 20 KHz. Calculating the efficiency here, from equations 1 to 4, S = 94.26%
become. In addition, it is less than the inner pan with a thickness of 0.55 mm.
The efficiency of 55mm is S = 85.97%, 8.29%
The efficiency of is improved.

The inner pot 36 has a flange 37 and an upper frame 31.
Is mounted in a suspended state via an upper frame cap 31A made of a heat-resistant resin, thereby being removably disposed. The induction coil 3 is provided outside the coil base 33.
8, the induction coil 38 has a close innermost and outermost winding. Further, the induction coil 38
The coil base 33 is supported by a coil cover 39 formed of a heat-resistant resin material on the lower part of the outer periphery of the coil base 33 so that the distance to the outer peripheral surface of the inner pot 36 is constant. Below the induction coil 38, a ferrite rod 40 made of iron oxide as a main raw material and sintered with a material having a high magnetic permeability is located. The ferrite rod 40 is adhered to the lower surface of the coil cover 39, The magnetic flux generated from the coil 38 is prevented from leaking downward.

Reference numeral 41 is a temperature detecting device having the following structure. 41A is a thermo case formed of a heat-resistant resin. The thermo case 41A is provided with a sensor base 43 in a guide cylinder 42 integrally formed on the outer bottom of the coil base 33.
And a compression coil spring 44 disposed between the sensor base 43 and the thermo case 41A.
Is always biased upward. Reference numeral 45 denotes a contact made of aluminum. The contact 45 is fitted on the upper part of the thermo case 41A via a temperature detecting element 46 composed of a negative temperature coefficient thermistor and a heat sensitive case 47. Crimping on the bottom.

The operation of the present embodiment configured as above will be described. The object to be cooked is stored in the inner pot 36 and placed on the upper surface of the upper frame 31 in a suspended state. Then, a current for generating an alternating magnetic field is passed through the induction coil 38, and the induction coil 3
An alternating magnetic field is generated at 8. As a result, an eddy current flows in the heat generating layer 36B of the inner pot 36, and the inner pot 36 is induction-heated by the Joule heat due to this eddy current, and the food to be cooked is cooked via the heat conducting layer 36A.

(Second Embodiment) The inner pot of the second embodiment will be described with reference to FIG. The configuration other than the inner pot 55 is the same as that of the first embodiment, and the description thereof is omitted. In the figure, an inner pot 55 is a heat conducting layer 55A of aluminum with a thickness of t2.5 mm, and two heat generating layers 5 on the outside.
5B and 55C, and two heating layers 55B,
Among the 55C, a heat generating layer 55B made of a magnetic material having a high magnetic coefficient is formed inside, and a fluorine coating 55D is applied to the inner surface of the heat conducting layer 55A. Here, the magnetic materials of the two heat generating layers 55B and 55C are 430 stainless steel and nickel, respectively. The current penetration depth and thickness of 430 stainless steel are δ ₁ and t ₁ , the current penetration depth of nickel and the thickness thereof are respectively. Is δ ₂ and t ₂ , then δ ₁ = 0.2
8 mm, δ ₂ = 0.12 mm, t ₁ = 0.6 mm, t ₂ = 0.
Inner pan 5 composed of 2 mm (at a frequency of 20 KHz)
When the efficiency of 5 is calculated by Equations 5 and 6, S = 97.6
It becomes 6 (%). The efficiency of the pot having a single heating layer (t = 0.8) of 430 stainless steel is improved by 3.4 (%), compared with 94.26 (%). Further, by providing nickel between aluminum and 430 stainless steel, the heat conduction layer 55A and the heat generation layer 55C are not separated from each other, heat conduction can be improved, and rice cooking performance can be stabilized.

[0025]

(Equation 5)

[0026]

(Equation 6)

(Third Embodiment) The inner pot of the third embodiment will be described with reference to FIG. The configuration other than the inner pot 65 is the same as that of the first embodiment, and the description thereof is omitted. In the figure, the inner pot 65 has an aluminum t2.
5mm heat conductive layer 65A, 430 stainless steel on the outside
The heat generating layer 65B has a thickness of 0.6 mm, the heat generating layer 65C made of nickel t2.0 is provided on the outside of 430 stainless steel, and the fluorine coating 65D is provided on the inside of the heat conducting layer 65A. With this configuration, a large-scale polishing process for the outer surface of the inner pot 65 can be eliminated, and the manufacturing cost can be reduced.

[0028]

As described above, according to the first aspect of the invention, the heat generating layer made of the magnetic material is processed to have a current penetration thickness of about 2.5 times or more, which is peculiar to the magnetic material. Can be sufficiently secured, thermal efficiency can be improved, and energy saving can be realized.

According to the second aspect of the present invention, two heat generating layers are formed outside the heat conducting layer, and a magnetic material having a high magnetic coefficient is formed inside the two heat generating layers. By this, workability is excellent, peeling between the heat conduction layer and the heat generation layer is eliminated, and heat conduction can be improved.

Further, according to the third aspect of the invention, a heat generating layer is provided on the outer side of the heat conducting layer of the inner pot, and nickel is provided on the outer side of the heat conducting layer, so that a large-scale polishing process of the outer surface of the inner pot can be performed. It can be abolished and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electric rice cooker according to a first embodiment of the present invention.

FIG. 2 is a sectional view of the inner pot of the electric rice cooker.

FIG. 3 is a sectional view of an inner pot of the electric rice cooker according to the second embodiment of the present invention.

FIG. 4 is a sectional view of an inner pot of an electric rice cooker according to a third embodiment of the present invention.

FIG. 5 is a sectional view of a conventional rice cooker.

[Explanation of symbols]

 30 main body 33 coil base 36 inner pot 36A heat conduction layer 36B heat generation layer 38 induction coil 41 temperature detection device

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsuru Yashima 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masafumi Kubo, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 72) Inventor Shoji Shimono, 1006 Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. (72) Seiichi Uemoto, 1006, Kadoma, Kadoma City, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. Osaka Prefecture Kadoma City 1006 Kadoma Matsushita Electric Industrial Co., Ltd. (72) Inventor Atsushi Tanaka Osaka Kadoma City Kadoma 1006 Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An electric rice cooker in which the inside is formed of a heat conducting layer and the outside is formed of a heat generating layer made of a magnetic material, and the thickness of the heat generating layer is about 2.5 times or more the current penetration depth peculiar to the magnetic material. pot. 2. The pan for an electric rice cooker according to claim 1, wherein the heating layer is formed of two layers of magnetic material having a high magnetic rate and a low magnetic rate, and the magnetic material having a high magnetic rate is disposed inside. 3. The pot for an electric rice cooker according to claim 1, wherein the heat generating layer is plated with an alloy of nickel and chromium. 4. A body, a pot for an electric rice cooker according to any one of claims 1 to 3, which is detachably housed in the body, and a non-metallic enclosure surrounding the outside of the pot for an electric rice cooker. An electric rice cooker comprising a coil base and an induction coil attached to the outside of the coil base to heat the electric rice cooker pot by electromagnetic induction.