JPH09313338A - Induction heating type cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize the cooling means of a heat generation element for constituting an inverter circuit for controlling an induction coil which is a heating means and to improve cooling performance. SOLUTION: A cooling tank 30 filled with a coolant 34 such as water and polyethylene glycol or the like is provided and a heater elements such as the semiconductor switching element 40 and diode bridge 42, etc., of the inverter circuit for generating an alternating magnetic field in the induction coil 13 for heating a pot 11 are attached to the surface of the cooling tank 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooker that uses induction heating for heating, and more specifically, a heating element of an inverter circuit that generates an alternating magnetic field in an induction coil is cooled by a refrigerant. The present invention relates to an induction heating cooker.

[0002]

2. Description of the Related Art FIG. 10 is a vertical cross-sectional view showing the structure of a conventional rice cooker disclosed in, for example, Japanese Utility Model Laid-Open No. 3-58219. In the figure, reference numeral 1 is a main body case, and 2 is a lid body mounted on the main body case 1 via a hinge so as to be openable and closable. A bottomed cylindrical pan 11 made of an iron-based material (magnetic material) is housed inside the main body case 1, and an upper end flange portion of the pan 11 is supported by an upper ring 6 a provided at an upper portion of the main body case 1. There is. Reference numeral 12 denotes a coil base made of a synthetic resin having heat resistance, which is fixed to the upper ring 6a by screws via an inner frame 14a.

An induction coil 13 serving as a heating means is adhered and fixed to a bottom surface and a lower part of a side surface of an outer periphery of the coil base 12, and a plurality of ferrites 17 are fixed outside the induction coil 13 via an insulator. Have been. The ferrite 17 functions as a magnetic shield that absorbs magnetic lines of force from the induction coil 13 and prevents the magnetic flux from leaking out of the main body case 1. Further, a reflection plate 17a made of an aluminum material is provided around the induction coil 13 and the ferrite 17 so as to surround the induction coil 13 and the ferrite 17, thereby strengthening prevention of leakage of lines of magnetic force and radiant heat to the outside of the main body case 1. .

Reference numeral 1b is a lower case constituting a lower part of the main body case 1, and a control board 20 on which a cord reel (not shown) and each element of an inverter circuit for generating an alternating magnetic field in the induction coil 13 are mounted inside. Are arranged.
Reference numeral 40 denotes a semiconductor switching element which is a heat generating element in the inverter circuit, that is, a transistor, and a space 25 partitioned by the partition plate 24a on one side in the main body case 1.
The electrodes are arranged in a, and their electrodes are connected to the control board 20 by lead wires (not shown). 50 is a transistor 4
It is a heat sink for air cooling having a surface area required for heat dissipation of 0, and is arranged vertically in a space 25a inside the main body case 1 and occupies most of this space. 1
Reference numeral 8 is a temperature sensor installed on the lower surface of the pot 2 so as to be contactable therewith.

In such a conventional rice cooker, power is supplied to the induction coil 13 via an inverter circuit to induce an eddy current in the pot 11 to heat the pot 11 to cook rice. The temperature control at this time is performed based on the signal from the temperature sensor 18 which is in contact with the lower surface of the pan 11. The radiant heat from the pan 11 and the induction coil 13 is blocked by the reflection plate 17a and the partition plate 24a to prevent leakage to the outside or the installation part of the heat sink 50. Further, heat generated by the transistor 40, which is a switching element in the inverter circuit, is radiated and cooled by the heat sink 50, so that the transistor 40 is kept within the operating temperature limit.

[0006]

In conventional cookers such as induction heating type rice cookers, the transistors which are the heat generating elements of the inverter circuit are air-cooled as described above, and therefore are required for heat dissipation (cooling). A large heat sink 50 having a large surface area is required, which is a factor that hinders downsizing of the cooking device.

In view of the above points, the present invention provides a cooker capable of downsizing the cooling means of the heating element forming the inverter circuit for controlling the induction coil which is the heating means and improving the cooling performance. To aim.

[0008]

The rice cooker according to the present invention comprises:
It is configured as follows. (1) In an induction heating type cooker having an induction coil for heating a pan stored in a pan storage portion of a main body case and an inverter circuit for generating an alternating magnetic field in the induction coil, a refrigerant is sealed and an inverter circuit is provided on the surface. Is provided with a cooling tank to which at least one of the heating elements constituting the above is attached.

(2) A cooling chamber is formed between the pot accommodating portion of the above (1) and the main body case, and a cooling tank is installed in this cooling chamber. (3) A temperature sensor was attached near the heating element of the cooling tank of (1) or (2) above.

(4) A blower is installed below the cooling tank of (1), (2) or (3) above, and when the temperature of the cooling tank rises, a temperature sensor detects it and operates the blower. I did it. (5) The blower according to (2), (3) or (4) above is installed below the cooling tank in the cooling chamber and near the intake port provided in the lower part of the main body case. (6) The cooling chamber of (2), (3), (4) or (5) described above is formed so as to widen from the top to the bottom. (7) Above (1), (2), (3), (4), (5)
Alternatively, the refrigerant enclosed in the cooling tank of (6) is a substance having a melting point within the operating temperature range of the heating element and not rising in temperature beyond the operating temperature range of the heating element within the cooking time.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. 1 is a longitudinal sectional view of an induction heating type rice cooker to which the present invention is applied, FIG. 2 is a rear view of FIG. 1, FIG. 3 is a rear view of FIG. 1 partially showing a cross section, and FIG. FIG. 5 is a bottom view and FIG. 5 is an enlarged view of a main part of FIG. In the figure, reference numeral 1 denotes a main body case which is made of a non-magnetic material such as synthetic resin and has an open top, and which is composed of a side case 1a and a lower case 1b. Reference numeral 2 is a non-magnetic material and is a lid that opens and closes the opening of the main body case 1, and includes an outer lid, an inner lid, a lid heater, a lid packing, etc., and is attached to the main body case 1 via the hinge 3 so as to be openable and closable. ing. 4 is provided on the front side of the main body case 1,
A latch mechanism 5 that locks the lid 2 when the lid 2 is closed is a steam port provided at substantially the center of the lid 2 and through which steam flows out when cooking rice.

Reference numeral 11 denotes a bottomed cylindrical pot having an inner surface made of a non-magnetic material such as aluminum and an outer surface made of a magnetic material such as stainless steel, and an inner surface coated with a fluororesin. It is placed on the support ring 6 provided on the main body case 1 and is housed in the pan housing portion described later. 1
2 is a coil base made of heat-resistant synthetic resin, and pan 1
It is formed in a shape corresponding to the bottom portion of No. 1, and an induction coil 13 as a heating means of the pot 11 is adhesively fixed to the bottom portion and the lower portion of the side surface. The upper portion abuts against a ring-shaped inner shield plate 14 attached to the support ring 6, and the two form a pot housing 15. Reference numeral 16 denotes a body heater attached to the outer peripheral surface of the inner shielding plate 14, which is energized during rice cooking and heat retention to generate heat.

Reference numeral 17 denotes a plurality of ferrites arranged below the coil base 12 at substantially equal intervals, and has a function of reducing noise emitted from the induction coil 13. Reference numeral 18 denotes a temperature sensor attached to a support frame 19 provided at the center of the coil base 12 so as to be slidable in the vertical direction.
The bottom is touched and the temperature is detected. Reference numeral 20 denotes a control board that is installed in a lower space of the main body case 1 and that controls an output of the induction coil 13, that is, heating power by mounting electronic components that form an inverter circuit, and an operation board that controls rice cooking. A menu selection button 22 and a rice cooking button 22 are provided, and the operation unit 2 is connected to the operation board 21.
Reference numeral 3 is a cord reel housed in a recess provided on the lower surface of the main body case 1.

Reference numeral 24 is a partition wall which separates the pan storage portion 15 from the rear wall of the main body case 1 (opposite side of the operation portion 22) and the rear portions of both side walls of the main body case 1. A cooling chamber 25 is provided between the partition wall and the rear wall. Form. The cooling chamber 25 is formed so as to widen from the upper part to the lower part. An intake port 26 opening to the cooling chamber 25 is provided in the lower part of the main body case 1, and an opening to the cooling chamber 25 is provided in the upper part. An exhaust port 27 is provided. 27a is a projecting piece formed in an eaves shape on the upper side of the exhaust port 27. A blower 28 is installed in the lower part of the cooling chamber 25, and its power supply cord is connected to the control board 20.

Reference numeral 30 is made of a material having a good thermal conductivity such as aluminum, and has a control board 20 and an operation board 21.
Away from, for example, as shown in FIG. 1 or FIG.
The cooling tank is mounted on the partition wall 24 or the rib 29 (FIG. 3) provided on the main body case 1 in the cooling chamber 25. If the cooling tank is installed at a position apart from the control board 20 and the operation board 21 as described above, the temperature rise of the electronic components mounted on the control board and the operation board can be prevented. As shown in FIGS. 6 to 8, this cooling tank 30 is composed of a shallow bottomed cylindrical main body 31 and a lid plate 32 that seals the opening thereof in a watertight manner. A bottomed cylindrical screw hole 33 having a female screw is provided. The lid plate 32 may be formed in a wavy shape in order to increase its surface area. The cooling tank 30 is filled with water having a high specific heat or a refrigerant 34 such as silicon oil or antifreeze.

Reference numeral 40 is a semiconductor switching element which is a heating element forming an inverter circuit, and 42 is a diode bridge (rectifying circuit) which is a heating element for generating a DC voltage supplied to the inverter circuit. As shown in FIGS. 6 and 9, the diode bridge 42 is fixed to the bottom surface of the cooling tank 30 with a screw 45 screwed into the screw hole 33 through an insulator 44 having a high thermal conductivity such as polyester. There is.
Reference numeral 46 denotes a cooling tank temperature sensor that detects the temperature of the cooling tank 30, and is pressed against the bottom surface of the cooling tank 30 by a leaf spring 48 that is fastened together with the semiconductor switching element 40 by a screw 45 that is screwed into the screw hole 33. There is. In addition,
Semiconductor switching element 40, diode bridge 42
The lead wires 41, 43, and 47 connected to the electrodes of the cooling tank temperature sensor 46 are connected to the control board 20, respectively.

Next, the operation of the present embodiment configured as described above will be described with reference to FIGS. 1, 5 and 6. First, put rice and water in the pot 11 and store them in the pot storage part 15 to cover the lid 2
Is closed, and the rice cooking switch of the operation unit 22 is turned on. As a result, the inverter circuit operates and an alternating magnetic field is generated in the induction coil 13, so that the pan 11 is heated and rice is cooked. At this time, the semiconductor switching element 40 and the diode bridge 42 generate heat, and the heat generated thereby is directly transmitted to the cooling tank 30 and is directed to the refrigerant (here, an example using water) 34 enclosed in the cooling tank 30. The heat is dissipated.

In the cooling tank 30, the enclosed water 34 is heated by the heat from the semiconductor switching element 40 and the diode bridge 42, and the heated water 34 has a low specific gravity and rises, so that the water 34 below Due to the temperature difference between them, convection 35 occurs. Due to the convection 35 of the water 34, heat is exchanged between the semiconductor switching element 40 and the diode bridge 42 via the wall surface of the cooling tank 30, the semiconductor switching element 40 and the diode bridge 42 are cooled, and these heating elements are generated. Is kept within operating temperature limits.

On the other hand, when the cooling tank 30 is heated, a temperature difference is generated between the upper part and the lower part of the cooling chamber 25, so that the outside air is sucked from the intake port 26 provided in the lower part of the main body case 1 to cool it. Heat exchange is performed by touching the outer surface of the tank 30, and the heated air rises and is exhausted to the outside from the exhaust port 27 provided in the upper portion of the main body case 1.
In this way, the cooling tank 30 is cooled by the air convection (chimney effect) in the cooling chamber 25.

Dew and the like may drop from the lid 2 and the main body case 1 during rice cooking.
It is blocked by the eave-shaped protrusions 27a provided on the upper part of the above, and does not enter the cooling chamber 25. When the rice cooking is completed, the rice cooking switch is automatically turned off, and the heat retention switch is turned on instead.

When the temperature of the cooling tank 30 rises abnormally (eg, exceeds 95 ° C.) due to continuous rice cooking, the cooling tank temperature sensor 46 detects this and the control board 20.
Send a signal to As a result, the blower 28 is energized and driven to forcibly cool the cooling chamber 25 and lower the temperature of the cooling tank 30. The temperature of the cooling tank 30 is a predetermined temperature (for example,
(85 ° C. or less), the cooling tank temperature sensor 46 detects this and sends a signal to the control board 20 to blow the air.
To stop.

In the above description, the case where water is used as the refrigerant 34 sealed in the cooling tank 30 has been described.
When silicone oil is used for the low temperature (eg -30
It can be used at temperatures ranging from (° C.) to high temperatures (for example, 200 ° C.) and has a wide range of applications. Further, in the case of a product for a cold region where there is a risk of freezing, an antifreeze liquid may be used as a refrigerant and the like may be appropriately selected.

In the above description, the cooling tank 30 has two heating elements, that is, the semiconductor switching elements 4.
Although the case where both 0 and the diode bridge 42 are attached is shown, one of the heating elements may be attached to the cooling tank 30 and the other heating element may be air-cooled by a heat sink. Even in this case, the number of heat radiation fins and the surface area of the heat sink can be reduced, so that the heat sink can be downsized.

Further, although the case where the present invention is applied to the illustrated rice cooker is shown in the above description, the present invention is not limited to this and can be applied to rice cookers having other structures. Further, although the case where the cooling tank is configured by the bottomed cylindrical main body and the lid plate is shown, the shape of the cooling tank can be appropriately changed.

In the above description, the rice cooker needs to be cooled because the heating element becomes considerably hot during rice cooking, especially when it is cooked continuously, and the cooking (rice cooking) time is almost constant. Since it is easy to specify the type of the refrigerant because the temperature rise is almost constant, the case where the present invention is applied to the rice cooker is shown, but the present invention is applied to the electromagnetic cooker,
It is also possible to cool the heating element that constitutes the inverter circuit of the electromagnetic cooker.

Embodiment 2 FIG. In the above-described first embodiment, an example in which water is used as the refrigerant to be sealed in the cooling tank 30 is shown, but next, an example in which polyethylene glycol is used as the refrigerant is shown. The polyethylene glycol used in this Embodiment 2 is solid at room temperature, melts at 55 ° C., has a heat of fusion of 43 cal / g, and a specific heat in the solid phase of 0.49 cal / g.
It is a substance with a specific heat of 0.55 cal / g. ° C in the liquid phase.
In the second embodiment as well, the rice cooker will be described as an example similar to the first embodiment. However, the configuration of the rice cooker other than the refrigerant is the same as that of the first embodiment, and the description thereof will be omitted.

When rice cooking is started, the semiconductor switching element 40 and the diode bridge 42 generate heat, and the generated heat is directly transmitted to the cooling tank 30 and radiated to the polyethylene glycol sealed in the cooling tank 30. Polyethylene glycol absorbs the heat and rises in temperature,
When it reaches 5 ° C, it melts and becomes a liquid, and the temperature rises further. In this way, heat is exchanged between the cooling tank 30 and the semiconductor switching element 40 and the diode bridge 42, and the semiconductor switching element 40 and the diode bridge 42 are cooled. Further, the cooling of the cooling tank 30 by the air convection in the cooling chamber 25 is the same as that in the first embodiment, and thus the description thereof is omitted.

FIG. 10 is a diagram showing changes in temperature of the refrigerant when rice is cooked for 60 minutes using 652 g of polyethylene glycol as the refrigerant. In this case, the total heat generation amount of the semiconductor switching element 40 and the diode bridge 42 is 45 kcal. The temperature at the start of rice cooking is 30 ° C. When rice cooking is started, heat from the semiconductor switching element 40 and the diode bridge 42 is absorbed, and the temperature of the polyethylene glycol sealed in the cooling tank 30 rises. When the temperature reaches 55 ° C., polyethylene glycol begins to melt, and the temperature does not change during the melting because all the absorbed heat is used for phase change. When the polyethylene glycol completely changes from a solid to a liquid, it continues to absorb heat, and the temperature rises, reaching about 80 ° C. at the end of cooking rice. In other words, when rice is cooked at a temperature of about 30 ° C. for 60 minutes, 652 g of polyethylene glycol is required to suppress the temperature rise to about 80 degrees which is the upper limit of the operating temperature of the heating element. It will be.

The reason why the temperature at the start of rice cooking is set to 30 ° C. is for an environment such as summer when the heating elements such as the semiconductor switching element 40 are likely to reach a high temperature. Similarly, the reason why the rice cooking time is set to 60 minutes is that, for example, two consecutive rices are cooked.
It is assumed that a heating element such as the semiconductor switching element 40 is likely to reach a high temperature, such as when rice is cooked. That is, by using 652 g of polyethylene glycol having the heat of fusion and the specific heat as described above, it is possible to meet various usage conditions of the rice cooker, and the cooling effect can be reliably obtained.

On the other hand, FIG. 11 shows the temperature change of water when rice is cooked using water as a refrigerant under the same conditions. As shown in the figure, when the same amount of water as in the case of the polyethylene glycol is used as the refrigerant, the water rises to near 100 ° C. at the end of rice cooking. That is, in order to suppress the temperatures of the semiconductor switching element 40 and the diode bridge 42 to 80 ° C., the amount of water that is a refrigerant must be increased. Thus, as can be seen by comparing the case where polyethylene glycol is used as the refrigerant and the case where water is used, the use of polyethylene glycol has a cooling effect even if the amount of the refrigerant is small. Can be miniaturized.

In the above description, the case where polyethylene glycol is used as the refrigerant has been described, but the melting point is within the operating temperature range of the heating element such as the semiconductor switching element 40, and the operating temperature range is exceeded within the cooking time. The same effect can be obtained as long as the substance has a specific heat so that the temperature does not rise. Here, the larger the heat of fusion,
Also, the larger the specific heat, the smaller the amount of refrigerant used. In addition to the above polyethylene glycol, paraffin and sodium acetate (sodium acetate) may be used as substances having a melting point within the operating temperature range of the heating element and having a specific heat so that the temperature does not rise beyond the operating temperature range within the cooking time. ) Etc. For example, usable paraffins have a melting point of about 45 ° C. to 65 ° C. and a heat of fusion of about 35.1 cal / g, and usable sodium acetate has a melting point of about 40 ° C. to 60 ° C. Some have about 30-60 cal / g.

If the melting point of the refrigerant is in the range of 30 ° C. or higher and 80 ° C. or lower (the upper limit of the operating temperature of the heat generating element such as the semiconductor switching element 40), the same effect can be obtained even in a high temperature operating environment. Obtainable.

[0033]

According to the rice cooker of the present invention, the following effects can be obtained. (1) Cooling of the heat generating element because at least one of the heat generating elements constituting the inverter circuit is mounted on the surface of which the refrigerant is sealed and has a cooling tank, and the cooling tank is installed at a position apart from the control board and the operation board. The effect can be enhanced and the cooling means can be miniaturized.

(2) Since the cooling chamber is formed between the pot accommodating portion of the above (1) and the rear wall of the main body case, and the cooling tank is installed in this cooling chamber, the heat generation of the heat generating element and the temperature of the cooling tank. As a result of the rise, an ascending air current is generated in the cooling chamber, whereby the outside air is sucked from the intake port provided in the lower portion of the main body case to cool the heating element and the cooling tank, so that the cooling performance can be improved.

(3) Since the temperature sensor is attached in the vicinity of the heating element of the cooling tank of (1) or (2) above, the temperature of the cooling tank, and thus the heating state of the heating element, can be constantly monitored.

(4) A blower is installed below the cooling tank of the above (1), (2) or (3), and when the temperature of the cooling tank rises abnormally, the temperature sensor detects it and operates the blower. Since it is forced to ventilate, the cooling tank can be effectively cooled and continuous rice cooking becomes possible.

(5) Since the blower of (2), (3) or (4) above is installed below the cooling tank in the cooling chamber and near the intake port provided in the lower part of the main body case, the temperature of the cooling tank When the temperature rises abnormally, the cooling tank can be cooled more effectively.

(6) Since the cooling chamber of (2), (3), (4) or (5) is formed so as to widen from the upper part to the lower part, convection of air is further promoted by the stack effect. be able to.

(7) The above (1), (2), (3),
(4), (5) or (6) has a melting point within the operating temperature range of the heating element as a refrigerant to be sealed, and the temperature does not rise beyond the operating temperature range of the heating element within the cooking time. Since the substance is used, the cooling performance is improved, and the cooling effect can be achieved with a small amount, so that the cooling tank can be made smaller.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is a rear view of FIG.

FIG. 3 is a rear view of FIG. 1 with a part shown in cross section.

FIG. 4 is a bottom view of FIG. 1.

FIG. 5 is an enlarged view of a main part of FIG. 1;

6 is a partially enlarged view of FIG.

FIG. 7 is a plan view of an example of a cooling pattern.

FIG. 8 is a vertical cross-sectional view of FIG.

9 is a bottom view of FIG. 7. FIG.

FIG. 10 is a diagram showing a change in temperature of a refrigerant (polyethylene glycol) with respect to a rice cooking time.

FIG. 11 is a diagram showing a change in temperature of a refrigerant (water) with respect to a rice cooking time.

FIG. 12 is a vertical cross-sectional view of an example of a conventional rice cooker.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 main body case, 2 lid body, 11 pan, 12 coil base, 13 induction coil, 15 pan housing part, 17 ferrite, 18 temperature sensor, 20 control board, 21 operation board, 22 operation part, 24 partition wall, 25 cooling room ,
26 intake port, 27 exhaust port, 28 blower, 30 cooling tank, 40, 42 heating element, 46 temperature sensor for cooling tank, 48 leaf spring.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Wataru Fujimoto Wataru Fujimoto 1728 Omaeda, Hanazono Town, Saitama Prefecture 1728 Mitsubishi Electric Home Appliances Co., Ltd. (72) Hiroaki Tsukahara 1728 Koeda, Haneda Town, Osato County, Saitama Prefecture Mitsubishi Electric Home Equipment Co., Ltd. (72) Inventor Takao Oshima 1728 Omaeda, Omaeda, Hanazono-cho, Saitama Prefecture Saitama Prefecture Home Equipment Co., Ltd.

Claims (7)

[Claims] 1. An induction heating cooker having an induction coil for heating a pan stored in a pan storage portion of a main body case, and an inverter circuit for generating an alternating magnetic field in the induction coil, wherein a refrigerant is sealed on the surface. An induction heating cooker comprising a cooling tank to which at least one of the heating elements constituting the inverter circuit is attached. 2. The induction heating cooker according to claim 1, wherein a cooling chamber is formed between the pan containing portion and the main body case, and a cooling tank is installed in the cooling chamber. 3. The induction heating cooker according to claim 1 or 2, wherein a temperature sensor is mounted in the vicinity of the heating element mounted on the cooling tank. 4. A blower is installed below the cooling tank, and when the temperature of the cooling tank rises, a temperature sensor detects it and operates the blower. The induction heating cooker described. 5. The induction heating cooker according to claim 2, wherein the blower is installed below the cooling tank of the cooling chamber and in the vicinity of the intake port provided in the lower portion of the main body case. 6. The cooling chamber is formed so as to widen from the top to the bottom.
The induction heating cooker according to 4 or 5. 7. The cooling medium sealed in the cooling tank is a substance having a melting point within the operating temperature range of the heating element and not rising in temperature over the operating temperature range of the heating element within the cooking time. The induction heating cooker according to claim 1, 2, 3, 4, 5 or 6.