JPH09190879A - Induction heating cooker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating cooker equipped with a plate which has a large cooking area and excels in the temp. distribution and high temp. characteristics. SOLUTION: An induction heating cooker includes the first heating coil 10 installed under the central part of a plate 1, the second and the third heating coil 11, 12 installed on both sides of the coil, and the first, second, and third inverter circuits to supply high frequency current to the heating coils, wherein further a drive circuit 13 is installed having a distribution device which makes duty control at certain periods of supplying the high frequency current from the inverter circuts. The duty control of this drive circuit 13 is made with periods within 30sec for each inverter circuit, and the total time of supplying the high frequency current to the second and third heating coils 11, 12 is made longer than the time of supplying the high frequency current to the first heating coil 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating cooker used at home.

[0002]

2. Description of the Related Art In recent years, induction heating cookers have been applied to various cookers due to their excellent characteristics such as safety, cleanliness, and high efficiency, as well as the additional heat generated by the pan or plate itself. And various plates for pottery are on sale. In addition, the thermal power is 1 at 100 volt voltage for general households.
400W high thermal power products are the mainstream. A general configuration of a conventional induction heating cooker will be described with reference to FIG. As shown in the figure, a top plate of a heat-resistant insulating plate 41 is provided on the upper part of the body 40, and the plate 42 is placed on the top plate 41. Most of the main body 40 has a circular shape that is relatively easy to manufacture, and most of them have a built-in 43 heating coil with an outer diameter of about 180 mm, and 44 driving circuit sections are also arranged in the main body 40. In the induction heating cooker configured as described above, the drive circuit unit 44 converts the AC power supply into the DC power, supplies the high frequency current to the heating coil 43, and
2 is induction heated.

Further, in the induction heating cooker described in Japanese Patent Laid-Open No. 5-166579, first and second heating coils for heating a grill plate and first and second heating coils for supplying a high-frequency current to the first and second heating coils are provided. An input power from a power source is provided, which is provided with a first and a second inverter circuit and a distributor for duty-controlling the supply of the high frequency current from the first and the second inverter circuit at a constant cycle and at an arbitrary ratio. The duty control cycle of the first and second inverter circuits is increased or decreased according to the value, or the duty control cycle of the first and second inverter circuits is increased or decreased according to the fluctuation range of the temperature of each plate. , The temperature ripple was reduced.

[0004]

However, in the above-mentioned conventional general induction heating cooker, since the heating coil having a relatively small area having an outer diameter of about 180 mm uses a high power of 1400 W, cooking for baking is performed. However, a plate with a large cooking area is required for cooking such as okonomiyaki, and if a large plate is placed on this induction heating cooker, the area that can be heated to a high temperature is almost directly above the heating coil. Therefore, uneven baking occurred and cooking could not be performed properly.

Further, in the configuration of the induction heating cooker disclosed in Japanese Patent Laid-Open No. 5-166579, the duty control of the two heating coils is performed, and the duty of the first and second inverter circuits is changed according to the input power value from the power source. The control cycle is increased or decreased, or the first range is adjusted according to the fluctuation range of each temperature of the plate.
In addition, since the duty control cycle of the second inverter circuit is increased or decreased, high-performance temperature control with less temperature ripple can be performed. However, the two heating coils generally have the same shape and are arranged symmetrically from the center of the plate to obtain the best temperature distribution. Since each heating is performed on one side by duty control, each heating coil is heated. The temperature at the outer periphery of the cooking surface of the plate and the boundary between the two heating coils was lower than that immediately above the coil, and uneven baking was likely to occur, and pancakes and okonomiyaki could not be used for successful cooking.

Here, when the two heating coils are brought close to each other,
Although the temperature at the boundary between the two heating coils increases, the temperature at the outer peripheral portion of the plate decreases. Also, the temperature distribution can be improved by enlarging the area of the heating coil, but the power density per unit area of the heating coil decreases, the loss in energizing the heating coil increases, the heating power decreases, and cooking is successful. I can no longer.

Further, if one heating coil is included in the other heating coil, the heat loss in the outer peripheral portion of the plate is larger than that in the central portion, so that the entire surface of the plate is uniformly heated. It was difficult.

Further, since heat loss is small in induction heating, when the set temperature of the plate is low, the same thermal power as in high temperature is too strong and the temperature range becomes large. Therefore, the electric power is varied to reduce the thermal power. However, the heat loss at the outer peripheral portion was larger than that at the central portion, and the ratio of the heat loss at the central portion was different from that at the outer peripheral portion at low temperatures, so the temperature distribution of the plate became worse at high temperatures.

The present invention is intended to solve the above problems, and an object thereof is to provide an induction heating cooker having a good temperature distribution even if a plate having a large cooking area is used.

[0010]

In order to solve the above-mentioned problems, the present invention provides a plate for cooking, a first heating coil arranged below the central portion of the plate, and a first heating coil. It has second and third heating coils provided on both sides, and first, second and third inverter circuits for supplying high frequency currents to the respective heating coils, and supplies high frequency currents from the respective inverter circuits. A drive circuit unit having a distribution device for duty control of presence / absence in a constant cycle,
The duty control of the drive circuit unit is performed in each inverter circuit in a cycle of about 30 seconds or less, and the high frequency is applied to the second and third heating coils as compared with the time of supplying the high frequency current to the first heating coil. The total time for supplying the electric current is lengthened.

[0011]

According to the first aspect of the present invention, since the central portion can be heated by the first heating coil arranged below the central portion of the plate, the boundary between the second heating coil and the third heating coil is limited. It is possible to prevent a temperature drop in the central portion corresponding to the portion. Further, in the duty control, since only one heating coil is constantly supplied with the high frequency current, if the high frequency current is supplied to one heating coil for a long time, the temperature rise of the plate becomes high, and other heating coils not supplied with the high frequency current are heated. Since the temperature drop in the heating range of the coil also increases, the temperature range of the plate increases and cooking cannot be performed well. Therefore, the temperature difference between the heating range and the heating stop range can be reduced by keeping the constant period within 30 seconds. Furthermore, the heat loss from the first heating coil is mostly due to heat radiation, but the heat loss from the second and third heating coils is due to heat conduction to the outer surface of the plate in addition to heat radiation. By controlling the total time of supplying the high-frequency current to the second and third heating coils to a longer period than the time of supplying the high-frequency current to the first heating coil, the heating to the outer peripheral portion of the plate is strengthened, The temperature distribution can be improved. Further, since the heat loss in the outer peripheral portion of the cooking surface is larger than the heat loss in the central portion of the plate, the ratio of the time for supplying the high frequency current to the first heating coil and the second heating coil is from 1: 1. By controlling the cycle in the range of 1: 2, the heat power to the outer peripheral portion of the plate is increased and the temperature of the outer peripheral portion is increased. Further, by setting the constant cycle within 30 seconds, the temperature difference between the heating range and the heating stop range can be reduced, and the temperature distribution can be improved.

According to the second aspect of the invention, when the set temperature of the plate is high, when the temperature is low, the decreasing temperature difference of the outer peripheral portion with respect to the central portion becomes large, but for the first heating coil that heats the central portion of the plate. The duty control in which the ratio of the time for supplying the high-frequency current to the other heating coil for heating the outer peripheral portion of the plate is increased can increase the temperature of the outer peripheral portion of the plate and improve the temperature distribution even at low temperatures.

According to the third aspect of the present invention, when the temperature of the plate is low, the ratio of the time for supplying the high-frequency current to the heating coil for heating the central portion of the cooking surface of the plate is made longer, so that the central portion is higher than that of the outer peripheral portion. Since the heat loss of the part is small, it can be raised in a short time. Then, after the plate temperature reaches a high temperature, by increasing the ratio of the time to provide the high-frequency current to the heating coil that heats the outer peripheral portion of the cooking surface of the plate, the temperature distribution that was bad at half-way heating can be improved. Therefore, it is possible to heat to the set temperature in a shorter time than the method of heating by controlling the temperature distribution from the beginning.

According to a fourth aspect of the present invention, when the set temperature of the plate is set to a high temperature, and once the set temperature is reached, food is put into the plate and the temperature of the plate is lowered, the entire surface of the plate is lowered. By switching from the control means for heating to the control means for heating a specific portion, the portion heated by one heating coil is constantly heated, so that heating can be performed with high thermal power.

According to the fifth aspect of the present invention, since the function of switching from the entire surface heating to the partial heating is limited to the low plate temperature when the high temperature is set, the heating of the high frequency current is performed without stopping by the partial heating. The temperature rise speed is fast,
The ripple of the temperature range becomes large and the temperature peak becomes high at the high temperature setting, so that the destruction of the fluororesin applied to the plate can be protected.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) In FIGS. 1 and 2, reference numeral 1 denotes a rectangular plate for cooking, which has two cooking surfaces and three outer surfaces. Reference numeral 4 denotes a top plate made of a ceramic flat plate, 5 denotes a main body case made of a highly heat-resistant resin such as PET resin having a temperature higher than 200 ° C., and the top plate 4 is provided on the flat peripheral portion of the main body case 5. It is fixed with 7 heat-resistant adhesives such as silicon resin. Reference numeral 8 is a main body bottom plate for molding the lower portion of the main body case 5, the heating coil support base 9 is attached to the main body bottom plate 8, and the first heating coil 11 and 11 arranged below the central portion of the plate 10 A second heating coil and a third heating coil provided on both sides of the twelve first heating coils 10 are attached. In addition, the main body bottom plate 8 is provided with 13 drive circuit portions, and the first and second heating coils 10, 12, 11 are provided with high-frequency currents.
Further, a third inverter circuit and a distributor for duty-controlling the supply of the high-frequency current from the inverter circuit at a constant cycle are provided, and the plate is heated by the duty control. Next, the operation will be described with reference to FIGS. 3 and 4. In the induction heating cooker, since the plate 1 itself directly generates heat, the range of the plate 1 heated by providing a high frequency current to one heating coil is Since it is limited to just above the heating coils, the temperature distribution measured at the center in the longitudinal direction of the plate 1 as shown in FIG. ing. This is because the heat is conducted to the outer side surface 3 of the outer peripheral portion of the cooking surface 2 of the plate 1, so that the temperature is lowered. Therefore, by separating the second heating coil 11 and the third heating coil 12 from the center, the amount of heat supplied to the outer peripheral portion of the cooking surface 2 of the plate 1 is increased, and the cycle for providing high-frequency current to each heating coil is increased. As shown in FIG. 4, the first heating coil 1
In a cycle in which the total time of supplying the high-frequency current to the second heating coil 11 and the third heating coil 12 is made longer than the time of supplying the high-frequency current to 0, for example, 7 seconds for the first heating coil 10, By setting the second heating coil 11 and the third heating coil 12 to 15 seconds, heating of the central portion of the plate 1 can be slightly weakened and heating of the outer peripheral portion can be strengthened.
The temperature distribution on the cooking surface 2 of the plate 1 as shown in (b) can be realized.

(Second Embodiment) 2 in FIG. 5 and FIG.
1 is a round plate for cooking, which has 22 cooking surfaces and 23
Has an outer surface. Reference numeral 24 denotes a top plate made of a ceramic flat plate, which is fixed to the main body case 25. Reference numeral 26 denotes a main body bottom plate that forms the lower part of the main body case 25, and the heating coil support base 27 is attached to the main body bottom plate 26, and the first heating coil arranged below the central portion of the plate 28 and 29 First heating coil 28
A ring-shaped second heating coil that covers the outer circumference of is attached. Further, the main body bottom plate 26 is provided with 30 drive circuit portions, and first and second inverter circuits for supplying a high frequency current to the first heating coil 28 and the second heating coil 29, and a high frequency wave from the inverter circuit. A distribution device for duty-controlling the supply of electric current at a constant cycle is provided, and the plate is heated by duty control.

The operation will be described below. The duty control is performed for 14 seconds for the first heating coil 28 and for the second heating coil 2
When a high-frequency current is supplied to 9 at a period of 18 seconds, the outer peripheral portion of the cooking surface 22 of the plate 21 becomes larger than the heat amount heated in the central portion, and the outer peripheral portion supplements the heat amount lost to the outer surface 23 by heat conduction. The temperature distribution of the plate 21 is improved, and even if cooking is performed, uneven baking does not occur and cooking can be performed well.

(Embodiment 3) The induction heating cooker has the same parts construction as that shown in the second embodiment.
The operation will be described by using the first heating coil 28 so that the temperature of the plate 21 reaches the maximum set temperature of 300 ° C.
When the maximum power of 1400 W is input to the second heating coil 29, the duty control is performed to the first heating coil 28 as shown in FIG. 7A in order to improve the temperature distribution of the plate 21 cooking surface 22. When the high frequency current is supplied to the second heating coil 29 for 16 seconds, the temperature distribution on the cooking surface 22 becomes the best. Here, in order to lower the temperature of the plate 21 to a low temperature of 160 ° C., the electric power was weakened.
The optimum heating power is 0 W, and the duty control is 14 seconds for the optimum first heating coil 28 and the second heating coil 29 at high temperature.
In the method of supplying the high-frequency current at a cycle of 16 seconds, the temperature of the cooking surface 22 is lower in the outer peripheral portion than in the central portion when the temperature is low, and the temperature distribution becomes poor. Therefore, it is necessary to increase the heat power to the outer peripheral portion, and when the input power is further reduced, the performance of the temperature control is inferior, so it is necessary to shorten the cycle time. Therefore, in order to improve the above, duty control is performed by supplying high frequency current to the first heating coil 28 shown in FIG. The temperature distribution of the performance can be secured.

(Embodiment 4) The parts configuration of the induction heating cooker is the same as the configuration shown in Embodiment 2, and FIG.
The operation will be described by using the set temperature of the plate 21 as X, and it takes the longest time to start preheating when the set temperature is the maximum temperature of 300 ° C. When the preheating time at this time is measured, In the normal heating method, the first heating coil 28 of the control method in which the temperature distribution is improved after preheating is completed
This is a method of starting preheating for 4 seconds by controlling the duty of the second heating coil 29 for 16 seconds. At this time, the temperature rises as shown in (a) of the graph of FIG. However, since it takes time, as shown in FIG.
Temperature of Y between 0 ° C, here first up to 200 ° C
26 seconds for the heating coil 28 and 1 for the second heating coil 29
By performing the duty control for 0 second and heating the plate 21 by increasing the input power for heating the central portion with respect to the outer peripheral portion of the cooking surface 22, the central temperature of the plate 21 can be quickly raised. This is because the central portion has less heat loss than the outer peripheral portion. Then, after reaching 200 ° C., duty control of the first heating coil 28 for 8 seconds and the second heating coil 29 for 25 seconds can be performed to raise the temperature of the outer peripheral portion of the cooking surface 22, and the temperature of the plate 21 can be increased. When reaching 300 ° C., the temperature distribution is improved and the preheating time can be shortened.

(Embodiment 5) The induction heating cooker has the same parts construction as that shown in the second embodiment.
The operation will be described with reference to the first heating coil 28.
The preheating of the plate 21 is started by the duty control of 4 seconds and the second heating coil 29 for 16 seconds, and the maximum set temperature of 300 is reached.
When the yakisoba which requires high thermal power is started at the time of X in the saturated state after the completion of preheating to 0 ° C., the temperature of the plate 21 decreases, and at the time of Y, the temperature becomes the lowest. After that, the temperature of the plate 21 gradually increases during cooking.
Although it starts to rise as shown in (a), cooking was not successful because the temperature of the plate 21 was low during cooking. At the time of Y when the temperature of the plate 21 has dropped, the first heating coil 28 and the second heating coil 29 are switched by duty control to provide a high frequency current to heat the entire cooking surface of the plate. The heating coil 28 is constantly supplied with a high-frequency current to switch to a control means for heating only the central portion of the cooking surface 22 of the plate 21, so that the temperature of the central portion of the cooking surface 22 is changed as shown in FIG. 9 (b). Can quickly rise to high temperatures. And the temperature of the plate 21 is high only in the central part and low in the outer peripheral part,
In yakisoba cooking, the food can be cooked while stirring, so it is better to cook while stirring only the central part of the food than when cooking the entire surface at low temperature. In addition to cooking yakisoba, when you want to grill a steak with high heat, you can change the arrangement of the cooked meat, so it is convenient when baking and keeping the baked food warm. .

[0022]

As described above, according to the first aspect of the invention, the induction heating cooker has the first heating coil for heating the central portion of the plate and the outer peripheral portions of the plate arranged on both sides of the first heating coil. The second and third heating coils for heating are provided, and the duty control is performed according to the set time cycle, so that the temperature distribution can be improved and the temperature can be set to a high temperature even for a plate having a large cooking area.

According to the invention of claim 2, the first
Even in the induction heating cooker in which the ring-shaped second heating coil is provided on the outer circumference of the heating coil, the control is performed with the optimum cycle for supplying the high-frequency current to the first heating coil and the second heating coil. By providing it, the characteristics with improved temperature distribution can be realized.

According to the third aspect of the invention, in the induction heating cooker, although the temperature distribution is good when the set temperature of the plate is high, the temperature distribution is often deteriorated when the temperature is low. Although the temperature difference in which the temperature of the plate decreases becomes large, the temperature distribution can be improved even if the temperature of the plate is any by providing the duty control means separately for the high temperature and the low temperature of the plate.

According to the fourth aspect of the invention, by using a plurality of heating control means as the heating means at the time of preheating the plate, it is possible to heat to the set temperature in a short time by control with improved temperature distribution. It was realized.

Further, according to the invention of claim 5, when the set temperature of the plate is set to a high temperature, and once the set temperature is reached, food is put into the plate to lower the temperature of the plate, By switching from the control means for heating the entire surface of the plate to the control means for heating a specific portion, it was possible to provide high heat power for cooking during cooking, and it was possible to perform cooking successfully.

[Brief description of the drawings]

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

FIG. 2 is a perspective view of the induction heating cooker.

FIG. 3 (a) is an operation explanatory diagram of the same induction heating cooker, and FIG. 3 (b) is another operation explanatory diagram of the same induction heating cooker.

FIG. 4 is an operation explanatory diagram of the induction heating cooker with respect to time.

FIG. 5 is a sectional view of an induction heating cooker according to a second embodiment of the present invention.

FIG. 6 is a perspective view of the induction heating cooker.

FIG. 7 (a) is an operation explanatory view of the induction heating cooker according to the third embodiment of the present invention, and FIG. 7 (b) is another operation explanatory view of the induction heating cooker.

FIG. 8 is an operation explanatory view of the induction heating cooker according to the fourth embodiment of the present invention.

FIG. 9 is an operation explanatory view of the induction heating cooker according to the fifth embodiment of the present invention.

FIG. 10 is a cross-sectional view of a conventional induction heating cooker.

[Explanation of symbols]

 1 Plate 2 Cooking Surface of Plate 3 Outside Surface of Plate 5 Main Body Case 10 First Heating Coil 11 Second Heating Coil 12 Third Heating Coil 13 Drive Circuit Section

Claims (5)

[Claims] 1. A plate for cooking, a first heating coil arranged below a central portion of the plate, second and third heating coils provided on both sides of the first heating coil, and A drive circuit unit having first, second, and third inverter circuits for supplying a high-frequency current to the heating coil, and a distribution device for duty-controlling whether or not the high-frequency current is supplied from each of the inverter circuits at a constant cycle. With and
The duty control of the drive circuit unit is performed in each inverter circuit in a cycle of about 30 seconds or less, and the high frequency is applied to the second and third heating coils as compared with the time of supplying the high frequency current to the first heating coil. An induction heating cooker that extends the total time to supply electric current. 2. A plate for cooking, a first heating coil arranged below a central portion of the plate, and an outer periphery of the first heating coil which covers an outer periphery of the plate and is disposed below an outer peripheral portion of a cooking surface of the plate. It has a ring-shaped second heating coil and first and second inverter circuits for supplying a high-frequency current to each of the heating coils, and determines whether or not the high-frequency current is supplied from each of the inverter circuits at a constant cycle. A drive circuit section having a distribution device for duty control, wherein the duty control of the drive circuit section is performed in a cycle of approximately 30 seconds or less for each inverter circuit, and a high-frequency current is supplied to the first heating coil. The induction heating cooker in which the time for supplying the high-frequency current to the second heating coil is extended within about twice as compared with 3. The duty control of the drive circuit unit is such that, as the set temperature of the plate becomes lower, the time for supplying the high-frequency current to the first heating coil is set longer than the time for supplying the high-frequency current to the other heating coils. Claim 1 or 2 which consists of
The induction heating cooker described. 4. The duty control of the drive circuit unit is such that, at the time of plate preheating, when the temperature of the plate is equal to or lower than a predetermined temperature, the ratio of the time for which the high-frequency current is supplied to the first heating coil is lengthened, and the plate temperature is set to the predetermined value. The induction heating cooker according to claim 1 or 2, wherein when the temperature is equal to or higher than the temperature, the ratio of the time for which the high frequency current is supplied to the other heating coil is lengthened. 5. The duty control of the drive circuit section is such that a high frequency current is supplied only to a specific heating coil when the temperature of the plate is equal to or lower than a predetermined temperature after the temperature of the plate once reaches a set temperature. The induction heating cooker according to claim 1 or 2.