JPH11276342A - Electromagnetic induction heating rice cooker - Google Patents

Abstract

(57) [Problem] To eliminate a step at a boundary portion between a magnetic metal material formed by thermal spraying from an outer bottom surface portion to a corner portion and a side surface of an inner pan and the inner pan main body, and to impair the aesthetic appearance. So that dirt does not adhere to the boundary. Also, the temperature inside the inner pan can be accurately detected by a temperature sensor contacting the center of the outer bottom surface of the inner pan. An inner pot (1) is provided in an inner pot (1) and an electromagnetic induction heating coil (5) for heating the inner pot (1). The inner pot body (1a) constituting the inner pot (1) is formed of a nonmagnetic metal material such as aluminum. In a rice cooker obtained by spraying a magnetic metal material 1b such as iron on the outer surface of the inner pot main body 1a, the thickness of the sprayed magnetic metal material 1b is increased at the bottom portion facing the electromagnetic induction heating coil 5. The thickness of the sprayed magnetic metal material at the center of the outer bottom surface of the inner pot 1 is made thinner than the bottom portion facing the electromagnetic induction heating coil 5 while gradually decreasing the thickness from the corner portion to the side surface. The temperature sensor 6 was contacted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rice cooker for cooking rice by generating heat in an inner pot by electromagnetic induction heating, and more particularly, to spraying a magnetic metal material onto the outer surface of an inner pot body made of a non-magnetic metal material. The present invention relates to an electromagnetic induction heating type rice cooker.

[0002]

2. Description of the Related Art Conventional electromagnetic induction heating type rice cookers are known in which an inner pot is formed by pressing a clad material in which an aluminum plate as a non-magnetic metal material and a stainless steel plate as a magnetic metal material are pressed. A stainless steel plate, which is a magnetic metal material, is spread on the bottom of a pan-shaped receiving mold, and molten aluminum, which is a non-magnetic metal material, is poured on top of it. In addition, there has been a method in which a magnetic metal material such as iron is thermally sprayed on an outer surface of an aluminum inner pan formed by pressing or melt forging.

[0003] Among these methods, the first one has a drawback that the magnetic metal material is limited to a stainless steel plate, iron which is a strong magnetic material cannot be used, and thus the heat generation efficiency is poor. Since the whole is composed of an aluminum plate and a stainless steel plate having a uniform thickness, there is a disadvantage that the aluminum plate and the stainless steel plate are apt to be peeled off when they are heavy and are processed into a complicated pot shape.
In addition, the following high-pressure melt forging has the disadvantage that the production cost is so large that it cannot be provided to consumers inexpensively, and the stainless steel plate, which is the heating element, has a uniform thickness, so the electromagnetic induction heating coil has In addition, the thickness of the heating element cannot be varied to adjust the heat generation balance. Further, since the inner pan is formed by pressing the molten aluminum at a high pressure with a pressing die, the pot itself cannot be manufactured unless it has a certain thickness, and there is a disadvantage that the inner pan becomes inevitably heavy.

[0004] On the other hand, in the case of spraying a magnetic metal material on the inner pan of a non-magnetic metal material shown last, a ferromagnetic material such as iron can be used as a heating element for induction heating. Since the magnetic material can be sprayed only on the part necessary for induction heating, the inner pan does not become unnecessarily heavy, and the thickness of the spray is variable according to the magnetic field generation condition (shape of the electromagnetic induction heating coil). This has the advantage that the heat generation balance can be adjusted.

Japanese Patent No. 2705083 is known as an electromagnetic induction heating type rice cooker using an inner pot of this thermal spraying system. JP-A-60-35491, JP-A-61-176089, JP-A-62-69481 and the like are already known.

[0006] However, those described above still cannot sufficiently exhibit the above-mentioned advantages, and have the following problems.

[0007]

That is, in the above-mentioned prior art, the thickness of the magnetic metal material is uniform except for those disclosed in JP-A-62-69481. For this reason, it is good to form the magnetic metal material layer on the entire outer surface of the inner pan, but when forming the magnetic metal material layer only on the portion facing the electromagnetic induction heating coil, the magnetic metal material layer is formed on the outer surface of the inner pan. There is a problem that a boundary portion is generated due to the presence or absence of the gap, and a step is generated at the boundary portion. Since the magnetic metal material needs a certain thickness (about 1.5 mm in Japanese Patent No. 2705083) to perform the electromagnetic induction heating, the step at the boundary is large, the appearance is unsightly, and the cleaning property is poor. Things.

Japanese Unexamined Patent Application Publication No. 62-69481 discloses a method in which the thickness of a magnetic metal material is partially changed. The purpose of the method is to eliminate uneven heating caused by electromagnetic induction heating. The thickness on the surface facing the heating coil is variable, and there is no intention to solve the problem of eliminating the step and maintaining the rust prevention performance.

Further, in the electromagnetic induction heating type rice cooker, the power supply to the electromagnetic induction heating coil is controlled so that an appropriate heating amount is obtained according to the rice cooking capacity in the inner pot and the water temperature. It is common to provide a rice cooker sensor on the main body, and to abut this on the center of the outer bottom surface of the inner pot.
Since the magnetic metal material having the same thickness as the other portions is sprayed on the contacting portion of the rice cooking sensor, there is also a problem that the temperature in the inner pot cannot be measured accurately.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to further improve the above-mentioned thermal spraying method, and a magnetic metal material formed by thermal spraying has a bottom portion opposed to an electromagnetic induction heating coil having the thickest corner. By gradually reducing the thickness from the part to the side, it is possible to prevent a step from occurring, thereby not impairing the aesthetic appearance of the appearance, and not to deteriorate the cleaning property such as the adhesion of dirt on the step. It was made. In addition, the thickness of the sprayed magnetic metal material at the center of the outer bottom surface of the inner pan is made thinner than the bottom part facing the electromagnetic induction heating coil, and by contacting the temperature sensor with this part, the temperature sensor inside the inner pan The temperature can be detected accurately.

There is a method in which the magnetic metal material is not sprayed at the center of the outer bottom surface of the inner pot. However, it is necessary to mask the center of the outer bottom surface of the inner pot so that the magnetic metal material does not adhere at the time of spraying. After removing, a step occurs at the boundary. Since the step is inferior in cleaning property as described above, in the present invention, the amount of thermal spraying at the portion in contact with the temperature sensor is gradually reduced from the surrounding portion, and the thickness at the bottom central portion is reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has an inner pot and an electromagnetic induction heating coil for generating heat in the inner pot. The inner pot body is formed of a non-magnetic metal material. In a rice cooker obtained by spraying a magnetic metal material, the thickness of the magnetic metal material sprayed is increased at the bottom portion facing the electromagnetic induction heating coil and gradually reduced from the corner portion to the side surface.

Further, the thickness of the sprayed magnetic metal material at the center of the outer bottom surface of the inner pot is formed thinner than the bottom portion facing the electromagnetic induction heating coil, and a temperature sensor is brought into contact with this portion.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a rice cooker according to the present invention in a front-rear direction, FIG. 2 is a cross-sectional view of the rice cooker in a left-right direction, and FIG. 3 is an enlarged bottom view of an inner pot of the rice cooker. FIG.

In the figure, 1 is an inner pot, 2 is a main body, 3 is a lid,
Is a protective frame, 5 is an electromagnetic induction heating coil, 6 is a temperature sensor, 7 is a control unit, 8 is a magnetic shield, 1a is an inner pot body, 1b is a magnetic metal material, 1c boundary, 1d is a rust prevention layer, and 1e is The fluororesin layer, 1f is a thick portion at the upper portion of the inner pot, 1g is a flange portion, and 1h is a handle of the inner pot 1.

More specifically, the inner pan 1 is housed in the main body 2 so as to be detachable, and a lid 3 is attached to the main body 2 so as to be openable and closable, and the upper openings of the inner pan 1 and the main body 2 are closed. doing. A protective frame 4 is provided inside the main body 2,
An electromagnetic induction heating coil 5 is provided at the bottom of the protection frame 4. The electromagnetic induction heating coil 5 is formed by winding an electric wire a plurality of times in the circumferential direction, and does not exist at or near the center of the bottom of the inner pan 1, but from near the middle of the bottom radius of the inner pan 1 to the bottom corner. The inner pan 1 is integrally provided in a flat plate shape up to a point farther from the electromagnetic induction heating coil 5, that is, in the vicinity of the diameter of the upper end of the inner pan 1. A temperature sensor 6 is provided at the center of the bottom of the protective frame 4 and is in contact with the bottom of the inner pot 1.

A control unit 7 for generating a high-frequency magnetic field in the electromagnetic induction heating coil 5 is provided in the main body 2, and a temperature sensor 6 is also connected to the control unit 7, and uses a power determined based on temperature information. The energization of the electromagnetic induction heating coil 5 is controlled. A magnetic shield 8 is provided on the lower surface of the electromagnetic induction heating coil 5.
Is provided to absorb the lower magnetic field of the high-frequency magnetic field generated vertically from the electromagnetic induction heating coil 5 and generate the magnetic field only on the upper side where the inner pot 1 is located.

The inner pan 1 is made of aluminum, which is a high heat conductive material, is formed into a pan shape by a press or a molten metal forging method, and is subjected to a process of roughening the surface of the outer side surface in order to increase the adhesion of thermal spraying. And a magnetic metal material 1b such as iron formed on the bottom by thermal spraying.
b indicates that the bottom surface facing the electromagnetic induction heating coil 5 has a thickness of 0.
The inner pot 1 is formed to have a thickness of about 7 mm, and is gradually thinned from the corner to the side of the inner pot 1 so that the thickness becomes zero at the boundary 1c. Also, the thickness of the bottom portion facing the electromagnetic induction heating coil 5 is gradually reduced from the thickness of 0.7 mm to the center, and the thickness at the contact portion of the temperature sensor 6 at the center is about 0.4 mm. It is formed so that it becomes. Thermal spraying is a manufacturing method in which the magnetic metal material 1b is melted and sprayed as fine particles into the inner pot main body 1a at a high pressure so as to be adhered.
The magnetic metal material layer is formed to a desired thickness by stacking fine particles in multiple layers. Therefore, the thickness can be easily varied as described above by adjusting the range to be sprayed and the time for spraying (generally, adjusting the program of the movement of the robot arm).

Since the magnetic metal material 1b has a filed surface formed by laminating fine particles, the magnetic metal material 1b is polished to smooth the surface, and then the magnetic metal material 1b is polished.
A rust prevention layer 1d is formed on the surface by thermal spraying.

The rust prevention layer 1d is formed of a material such as zinc or aluminum for the purpose of preventing rust of the magnetic metal material 1b.
The thickness is approximately 0.05 mm approximately uniformly. The range is provided above the boundary 1c, and the boundary 1c
Has been applied to completely cover. Further, the entire outer surface of the inner pot 1 is covered with a fluororesin layer 1e from above.

At the upper end of the inner pot 1, there is formed a thick portion 1f and a flange portion 1g formed by folding an aluminum material or forming a thicker portion than other portions by a molten metal forging method.

The thick portion 1f is made thicker than the other portions so as to have a heat storage effect, and to store heat during cooking and expose the protection frame 4 so that the upper end of the inner pot 1 which is easy to cool is heated to a high temperature even when steaming. I try to keep it.

Further, the handle 1 of the inner pot 1 is provided on the flange portion 1g.
h are provided at two opposing positions in the left-right direction. The handle 1 h is installed on the main body 2, the inner pot 1 is fixed, and is held in a state where the inner pan 1 is not in contact with the protective frame 4.

Next, the operation will be described along the flow of rice cooking.

When the user puts the washed rice and an appropriate amount of water into the inner pot 1 and operates a rice cooker switch (not shown), the controller 7 starts cooking rice. A high-frequency current flows from the control unit 7 to the electromagnetic induction heating coil 5, thereby generating a high-frequency magnetic field from the electromagnetic induction heating coil 5. Since the downward magnetic field is absorbed by the magnetic shielding material 8, a magnetic field is generated only on the upper side of the inner pot 1 side. The generated high-frequency magnetic field permeates through the fluororesin layer 1e and the rust-preventive layer 1d of the inner pot 1 where no magnetism acts, and acts on the magnetic metal material 1b. In the magnetic metal material 1b, the bottom portion of the inner pot 1 facing the electromagnetic induction heating coil 5 is the thickest and has a thickness of about 0.7 mm, and a magnetic field acts most on this portion and is converted into heat. From the corner to the side of the inner pot 1, the distance from the electromagnetic induction heating coil 5 gradually increases, so that the magnetic field hardly acts and the magnetic metal material 1
Since the thickness of the magnetic metal material 1b becomes zero at the boundary 1c where the magnetic field hardly acts, the heat generation becomes lower as going upward from the corner.

Accordingly, the inner pot 1 is heated most strongly from the bottom to the corner of the magnetic metal material 1b facing the electromagnetic induction heating coil 5, and this heat is transmitted from the magnetic metal material 1b to the inner pot main body 1a, Due to the high thermal conductivity of the main body 1a, the rice is transmitted to the entire bottom surface and side surfaces of the inner pot, and is also transmitted to the rice and water in the inner pot 1 to cook rice. In particular, since the inner pot 1 is strongly heated from the bottom to the approximate center of the corner, the heated water rises along the side from the inner corner of the inner pot 1, and strong convection occurs. In the present embodiment, since iron is used for the magnetic metal material 1b, the magnetic metal material 1b is a ferromagnetic material as compared with stainless steel or the like, has a high efficiency of converting a magnetic field into heat, and can be heated with a strong thermal power. Even if iron is used, it is not rusted because it is protected by the rust prevention layer 1d provided above the boundary 1c and the fluororesin layer 1e provided on the entire outer surface of the inner pot 1.

On the other hand, a magnetic field also acts on the central portion of the inner pan 1, but in the present invention, since the thickness of the magnetic metal material 1b is made thinner at the central portion, the magnetic field of the electromagnetic induction heating coil 5 causes heat. It is difficult to convert, and the calorific value does not become as high as its peripheral part. Therefore, the central portion of the inner pan 1 is the thick portion 1 of the inner pan body 1a.
It is strongly affected by the heat conducted inside f and the temperature of water and rice in the inner pot 1. For this reason, the temperature sensor 6 in contact with the center can detect the temperature of the inner pot 1 without being greatly affected by the electromagnetic induction heating, and can cook the rice deliciously by accurate heat control. it can.

By this accurate temperature detection, the control of the control unit 7 executes the control of the so-called "starting choro-choro, middle papper ...", and the power supply to the electromagnetic induction heating coil 5 is controlled so that the rice cooking proceeds.

When the inside of the inner pot 1 boils over time, the lid 3
Thick part 1 of inner pan 1 due to excess heat of steam discharged from
The heat is stored in f and reaches approximately 100 ° C. When the rice sucks the water in the inner pot 1 and the water runs out, the temperature at the bottom of the inner pot 1 rises sharply, the temperature sensor 6 catches this, ends the rice cooking, and shifts to steaming.

During the steaming, the cooked rice in the inner pot 1 is kept at a high temperature and steamed by the heat stored in the inner pot body 1a and the heat stored in the thick portion 1f. In particular, the temperature of the upper end of the inner pot 1 exposed from the protection frame 4 tends to decrease, but in the present embodiment, since the heat is stored in the thick portion 1f, the temperature decrease is small and a sufficient steaming effect can be obtained. After the steaming for a certain period of time, rice is ready and ready to be eaten.

After the rice is eaten, the inner pot 1 is washed. In the present invention, the thickness is smoothly changed from the corner so that the thickness of the magnetic metal material 1b becomes zero at the boundary 1c. As a result, there is no step at the boundary 1c, so that dirt is not clogged and the cleaning property is high. At the same time, the aesthetic appearance has been improved.

[0033]

As described above, according to the present invention, an inner pot is formed from a non-magnetic metal material, and the outer surface of the inner pot is sprayed with a magnetic metal material. The opposite bottom surface is made thicker and formed gradually thinner from the corners to the side surfaces, so that no step is formed at the boundary between the two, so that the appearance is not impaired and dirt adheres to the step. The cleaning performance is not inferior.

Further, since the thickness of the sprayed magnetic metal material at the center of the outer bottom surface of the inner pot, which is in contact with the temperature sensor provided on the main body, is formed to be thinner than the peripheral portion of the bottom, the center of the bottom surface is electromagnetic. Induction heating is not easily performed, and the temperature sensor in contact with it is less affected by electromagnetic induction heating, it can detect the temperature in the inner pot more accurately, and it can finish delicious rice with accurate heat control .

[Brief description of the drawings]

FIG. 1 is a sectional view of a rice cooker according to the present invention in a front-rear direction.

FIG. 2 is a cross-sectional view in the left-right direction of the rice cooker.

FIG. 3 is an enlarged sectional view of a bottom portion of an inner pot of the rice cooker.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inner pot 1a Inner pot main body 1b Magnetic metal material 1c Boundary part 2 Main body 3 Lid 4 Protective frame 5 Electromagnetic induction heating coil 6 Temperature sensor 7 Control part

Claims (2)

[Claims] 1. An inner pot (1) in a main body (2) and an electromagnetic induction heating coil (5) for generating heat in the inner pot (1).
A rice cooker in which an inner pot body (1a) constituting the inner pot (1) is formed of a non-magnetic metal material and a magnetic metal material (1b) is thermally sprayed on an outer surface of the inner pot body (1a), An electromagnetic induction heating type rice cooker characterized in that the thickness of the magnetic metal material (1b) sprayed is increased at a bottom portion facing the electromagnetic induction heating coil (5) and gradually reduced from a corner portion to a side surface. . The thickness of the sprayed magnetic metal material at the center of the outer bottom surface of the inner pot (1) is determined by an electromagnetic induction heating coil (5).
2. The electromagnetic induction heating type rice cooker according to claim 1, wherein a temperature sensor (6) is formed to be thinner than an outer bottom surface portion facing the heat sink.