JP2003310429A - Rice cooker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a lighter weight and a less cost of a rice cooker by realizing a lighter and inexpensive heating coil for induction-heating a pot where cooking materials are placed. <P>SOLUTION: A high frequence power is supplied to the heating coils 4 and 5 with an inverter circuit 8 to cause an induction heating for the pot 3 where the cooking materials are placed and the operation of the inverter circuit 8 is controlled by a control part 13. The heating coils 4 and 5 are produced by intertwisting sheathed/insulated aluminum wires to be wound. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rice cooker that induction-heats a pan containing a food.

[0002]

2. Description of the Related Art Conventionally, this type of rice cooker has been constructed as shown in FIG. The configuration will be described below.

As shown in FIG. 2, the rice cooker main body 21 is provided with an accommodating portion 22 for accommodating a pan 23 into which food is to be cooked, and an upper portion of the rice cooker main body 21 is openably and closably covered. The pan 23 can be taken out by opening and closing the lid 24. The heating coil 25 is arranged at a position facing the center of the bottom of the pot 23, and induction heats the center of the bottom of the pot 23. The heating coil 26 is arranged at a position facing the outer peripheral portion of the bottom surface and the lower portion of the side surface of the pot 23, and induction heats the outer peripheral portion of the bottom surface and the lower portion of the side surface of the pot 23.

The operation of the inverter circuit 28 is controlled by the control unit 27 composed of a microcomputer,
A high frequency current is supplied to the heating coils 25 and 26. The cooling fan 29 cools components of the inverter circuit 28 and the like.

The coil wires of the heating coils 25 and 26 are formed by twisting about 30 strands having a diameter of about 0.3 mm (Litz wire structure). The twist pitch is about several cm, and each of the strands has a configuration in which the vertical positional relationship is repeated several times with respect to the lower surface of the pot 23 in one turn. The material of the wires is copper, and the surface thereof is insulation-coated with polyester or the like so that the wires are not electrically connected.

The reason why the coil wires of the heating coils 25 and 26 are constructed by twisting such strands is that the high frequency current of about 20 to 30 kHz flowing in the heating coils 25 and 26 is caused by the skin effect on the surface of the coil wires. Since the current concentrates on the wire, it is necessary to make it sufficiently small with respect to the skin depth of the high frequency current flowing through the diameter of the coil wire, and due to the proximity effect that acts on the heating coils 25 and 26 and the pan 23, the specific wire This is to prevent current from concentrating on.

The heat resistance temperature of the insulation constituting the insulation coating is generally about 150 ° C. to 180 ° C. When the temperature of the coil wire exceeds this heat resistance temperature, it is difficult to insulate the wires and coil wires. In this case, the function as the coil cannot be achieved.

Therefore, in order to suppress the temperature rise of the coil wire, the heating coils 25 and 26 of the rice cooker which consumes power of about 1200 W usually have a diameter of 0.3 mm to 0.5 m.
About 30 polyester-coated copper wires of about m are twisted together.

[0009]

However, in such a conventional rice cooker, the heating coils 25 and 26, which are constructed by twisting and winding copper wires having a plurality of insulating coatings as described above, increase in temperature. Since the number of the heating coils 25 and 26 is about 30 in order to suppress the heating, there is a problem that the weight of the heating coils 25 and 26 itself becomes heavy.
Adhesive to secure the protective frame to a fixing member such as a protective frame (not shown), or a large amount of flame-resistant and heat-resistant resin is required to maintain the strength of the protective frame, resulting in a heavy rice cooker product. However, there is a problem that the material cost becomes high.

Further, the performance of the cooling fan 29 can be improved so as to cool the coil wire better, and the number of coil wires can be reduced and lightened, but the cost of parts such as the cooling fan 29 is increased, It had a problem of reducing the commercial value.

The present invention solves the above conventional problems, and an object thereof is to realize a lightweight and inexpensive heating coil, and as a result, to reduce the weight and cost of a rice cooker.

[0012]

In order to achieve the above object, the present invention supplies high frequency power to a heating coil by an inverter circuit to induction-heat a pot for containing food, and controls the operation of the inverter circuit by a control unit. The heating coil is constructed by twisting and winding an aluminum wire having an insulating coating.

As a result, a lightweight and inexpensive heating coil can be realized, and as a result, the rice cooker can be reduced in weight and cost.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a pan in which a food is put, at least one heating coil for inductively heating the pan, and an inverter circuit for supplying high-frequency power to the heating coil. And a control unit for controlling the operation of this inverter circuit, wherein the heating coil is formed by twisting and winding an aluminum wire having an insulating coating, and the skin resistance of aluminum at 20 kHz is 0.45. (10-4Ω), 0.36 of copper (10-
4Ω), but by increasing the number of strands (aluminum wire with insulating coating) to be twisted together, the current flowing between layers will not be biased toward the pan side, and a heating coil with the same level of loss as copper will be used. Can be realized, in addition,
Since the coil wire made by twisting the wires is made of aluminum, the weight of the coil can be made lighter than the conventional heating coil made by twisting the copper wires and the heating efficiency can be improved even if the number of twisted wires is increased. A good, light and excellent rice cooker can be provided.

According to a second aspect of the present invention, in the first aspect of the present invention, an aluminum wire having an insulating coating is twisted and wound only in a part of the plurality of heating coils. Therefore, it is possible to provide an excellent rice cooker that can suppress the cost increase and reduce the weight.

According to a third aspect of the present invention, in the invention according to the first aspect, at least one of the plurality of heating coils is mixed and twisted with an aluminum wire and a copper wire having an insulating coating. Since it is configured to rotate, it is possible to provide an excellent rice cooker that can suppress cost increase and reduce weight.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) As shown in FIG. 1, a rice cooker main body 1 has an accommodating portion 2 for accommodating a pan 3 for accommodating food to be cooked therein.
Is provided, and the upper portion of the rice cooker body 1 is configured to be openably and closably covered by the lid 9, and the pan 3 can be taken out by opening and closing the lid 9. The heating coil 4 is arranged at a position facing the center of the bottom surface of the pot 3, and induction heats the center of the bottom surface of the pot 3. The heating coil 5 is arranged at a position facing the outer peripheral portion of the bottom surface and the lower portion of the side surface of the pan 3, and induction-heats the outer peripheral portion of the bottom surface and the lower portion of the side surface of the pan 3.

The heating coils 4 and 5 are provided along the outer peripheral portion of the pot 3, and the heating coils 4 and 5 are fixed to the protective frame 6 made of a high heat resistant resin with an adhesive or integrally formed with a gap therebetween. A plurality of ferrite cores 7 that absorb the leakage magnetic flux are radially provided below the protective frame 6.

The temperature detecting device 10 detects the temperature of the pot 3, and is provided so as to contact the center of the bottom surface of the pot 3. The signal of the temperature detecting device 10 is input to the control unit 13. The control unit 13 controls the oscillation of the inverter circuit 8 provided at the bottom of the rice cooker body 1 that supplies high-frequency power to the heating coils 4 and 5 independently, and at the same time, the rice cooker body 1
It is configured to control the operation display unit 11 provided on the upper part of the.

The cooling fan 12 is for cooling the components of the inverter circuit 8 and the like, and the heaters 14 and 15 are for heating the pot 3 from the side surface and the top surface, respectively. The heaters 14 and 15 perform induction heating. It may be a heating coil.

The operation of the above configuration will be described. When the pan 3 is stored in the storage part 2, the pan 3 is provided at the center of the bottom of the storage part 2.
Corresponding to the temperature detected by the temperature detection device 10 of the control unit 13
Sends a heating start signal to the inverter circuit 8 to start the rice cooking. When the rice cooking mode is selected with the rice cooking key of the operation display unit 11, the control unit 13 causes the inverter circuit 8 to supply a high frequency current to the heating coils 4 and 5. As a result, the heating coils 4 and 5 induction-heat the pot 3 to start cooking rice.

The heating coils 4 and 5 are composed of about 40 aluminum wires having a diameter of 0.3 mm and having an insulating coating such as polyester twisted together (Litz wire structure). As a reason for twisting about 40 strands, when comparing the skin resistance at 20 kHz between copper and aluminum, copper is 0.36 (10-4 Ω), aluminum is 0.45 (10-4 Ω), and aluminum is about the same as copper. 1.
3 times. Therefore, if the number of stranded wires is 40 times, which is about 1.3 times the number of copper wires, that is, 30 times,
The copper stranded wire and the 40 aluminum stranded wires can have almost the same resistance.

At this time, comparing the weights of the wire rods, the density of copper is 8.9 (10-3 kg / m3), whereas that of aluminum is 2.7 (10-3 kg / m3), which is about 1 of copper.
/ 3. As a result, the number of wires is about 1.3 times, but the total weight of aluminum wires can be reduced by about 60%.

The heating coils 4 and 5 have a twisting pitch of about several centimeters, and each of the strands has a structure in which the upper and lower positions of the lower surface of the pot 3 are repeated several times during one turn.
Further, it is composed of a heating coil 4 for inductively heating the bottom surface of the pan 3, and a heating coil 5 for inductively heating the lower side surface of the pan 3 and the outer periphery of the bottom surface. The heating coils 4, 5 are elevated along the outer peripheral portion of the pan 3. It is fixed to the protective frame 6 made of heat-resistant resin by an adhesive or by integral molding.

The inverter circuit 8 individually and independently controls the amount of high frequency power supplied to the heating coils 4 and 5. That is, the amount of high-frequency power supplied to the heating coils 4 and 5 is adjusted according to the specifications of the heating coils 4 and 5. For example, according to the number of turns of the heating coils 4, 5, the heating area, the outer diameter size, or the connection state of the heating coils 4, 5 and the pot 3, the power density distribution in each part of the pot 3 becomes uniform. In addition, the control unit 13 controls the amount of high-frequency power supplied to the heating coils 4 and 5 of the inverter circuit 8 and the energization time.

When a high-frequency current of 20 kHz or more flows through the heating coils 4 and 5, the electric current is concentrated on the surface portion of each wire due to the skin effect. In the case of this embodiment, the diameter of each wire is equal to the skin depth. On the other hand, it is thin enough (eg 20 kHz
However, non-uniformity of current distribution due to the skin effect does not occur.

As described above, in this embodiment, the heating coils 4 and 5 have a diameter of 0 ..
By constructing about 40 strands of about 3 mm aluminum strands, the resistance can be almost the same as the conventional twisted strand with copper, and the weight of the coil wire is about the same as copper. Since the weight can be reduced by 60%, the amount of adhesive for fixing the heating coils 4, 5 can be reduced, or the amount of resin material used for the protective frame 6 can be reduced, thereby realizing an inexpensive and lightweight rice cooker. be able to.

In this embodiment, 40 aluminum wires having a diameter of about 0.3 mm are twisted together, but the present invention is not limited to this, and the diameter of the aluminum wires is 0.1 mm to 0.5 mm. Even in the interval, the weight of the heating coil can be reduced by forming the number of wires that has about 1.3 times the cross-sectional area of the stranded wire made of the conventional copper wire.

(Embodiment 2) The heating coils 4 and 5 shown in FIG.
One of these, for example, the heating coil 5 is formed by winding a coil wire formed by twisting aluminum wires having an insulation coating, and the other heating coil 4 is formed by twisting a copper wire having an insulation coating. It is constructed by winding a coil wire. The other structure is the same as that of the first embodiment. Further, the operation in the above configuration is the same as that of the above-mentioned first embodiment, and therefore its explanation is omitted.

The aluminum wire has a higher unit price than the copper wire, and the weight of the heating coils 4 and 5 can be reduced by simply replacing the copper wire with the aluminum wire, but the material cost is increased and the number of the wires is also increased. The cost will increase as the number increases.

By constructing one of the heating coils 4 and 5 by winding a coil wire formed by twisting aluminum wires having an insulating coating, it is possible to suppress the cost increase and reduce the weight of the rice cooker. it can.

(Embodiment 3) The heating coils 4 and 5 shown in FIG.
Either or both of these, for example,
20 aluminum wires having an insulating coating and 15 copper wires are mixed and twisted to form a coil wire. The other structure is the same as that of the first embodiment. Further, the operation in the above configuration is the same as that of the above-mentioned first embodiment, and therefore its explanation is omitted.

Here, the number of aluminum wires and copper wires to be mixed is not limited to this, as long as it has a cross-sectional area equivalent to that of 30 conventional copper wires.

[0035]

As described above, according to the invention described in claim 1 of the present invention, a pot for putting a cooking product, at least one heating coil for inductively heating the pot, and high frequency power to the heating coil. The heating coil includes an inverter circuit for supplying and a control unit for controlling the operation of the inverter circuit, and the heating coil is formed by twisting and winding an aluminum wire having an insulating coating. By increasing the number of aluminum wires), the current flowing between each layer is not biased to the pan side, and it is possible to realize a heating coil with the same level of loss as copper.
Since the coil wire made by twisting the wires is made of aluminum, the weight of the coil can be made lighter than the conventional heating coil made by twisting the copper wires and the heating efficiency can be improved even if the number of twisted wires is increased. Also, since the weight of the coil is light, the amount of the adhesive for fixing the heating coil or the resin material for holding the heating coil can be reduced, and a light and inexpensive rice cooker can be provided.

Further, according to the second aspect of the invention, the aluminum wire having the insulating coating is twisted and wound only in a part of the heating coils among the plurality of heating coils. An excellent rice cooker that can be reduced in weight can be provided.

Further, according to the invention described in claim 3, since at least one of the plurality of heating coils is formed by mixing and twisting an aluminum wire and a copper wire having an insulating coating and twisting them, It is possible to provide an excellent rice cooker that suppresses up and is lightweight.

[Brief description of drawings]

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

[Figure 2] Side view of a conventional rice cooker with a part cut away

[Explanation of symbols]

3 pots 4 heating coil 5 heating coils 8 Inverter circuit 13 Control unit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kono             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Seiichi Takagura             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 3K051 AA08 AC39 AD35 CD43 CD44                 3K059 AA08 AB04 AD32 AD35 CD63                 4B055 AA03 BA28 CA02 CA04 DA02                       DB14 FA16 FB02 FB06 FC20                       FD10 FE10

Claims (3)

[Claims] 1. A pan for containing food, at least one heating coil for inductively heating the pan, an inverter circuit for supplying high-frequency power to the heating coil, and a controller for controlling the operation of the inverter circuit. The heating coil is a rice cooker in which an aluminum wire having an insulating coating is twisted and wound. 2. The rice cooker according to claim 1, wherein an aluminum wire having an insulating coating is twisted and wound only on a part of the plurality of heating coils. 3. The rice cooker according to claim 1, wherein at least one of the plurality of heating coils is formed by mixing an aluminum wire and a copper wire having an insulating coating, twisting them, and winding the mixture.