JPH07250756A - Induction heating type rice cooker - Google Patents

Abstract

PURPOSE:To change the convection of the heat within an inner pan to deliciously cook rice with little boiling unevenness. CONSTITUTION:In an induction heating type rice cooker for heating an inner pan 5 containing rice and water by the high frequency magnetic field generated from an induction heating coil 3 connected to an inverter circuit device 4 to boil rice, this device has a power regulating means 8 for changing the output of the inverter circuit device 4 to regulate the power for heating the inner pan 5; and an input power determining means 9 for determining the optimum power to be inputted according to conditions such as rice cooking capacity in boiling process for keeping the boiled state. It also has an increasing and decreasing means 10 for increasing and decreasing the electric heating power of the inner pan 5 by the power regulating means 8 on the basis of the input power determined by the input power determining means 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating type rice cooker for changing the electric power in accordance with the rice cooking process to change the convection of heat inside the inner pot to cook delicious rice.

[0002]

2. Description of the Related Art Conventional induction heating type rice cookers of this type are disclosed in, for example, JP-A-4-319312 and JP-A-3-261.
No. 420 publication is known. These are for cooking rice by induction heating an inner pot containing rice and water by a high-frequency magnetic field generated from an induction heating coil connected to an inverter circuit device.
The control unit decided the electric power to be input and adjusted the electric power to heat the inner pot with the electric power. Then, as the rice cooking process progresses, the electric power supplied is appropriately changed in accordance with the rice cooking capacity at that time, and the heating control of "first choro choro medium papa ..." is performed. This fire control is based on the same idea as the invention that is often found in conventional electric rice cookers, which include a resistance heater and a contact portion that opens and closes the energizing circuit.

[0003]

In such a conventional configuration, the electric power supplied changes according to the rice cooking process, but the change is in the unit of several minutes. An induction heating type rice cooker cooks rice by induction heating an inner pot containing rice and water by the high-frequency magnetic field generated from the induction heating coil, but in principle, the magnetic field concentrates on the portion close to the induction heating coil of the inner pot and heats strongly. To be done. For this reason, the water temperature of the strongly heated portion rises quickly, and convection occurs above the inner pot. Since the amount of heat supplied is constant during the above-mentioned few minutes when the supplied electric power is constant, the manner and strength of heat convection in the inner pot are stable and constant.

For this reason, when the electric power is low, heat is transferred laterally, the entire lower rice is softly collapsed, and the upper rice is hardened. On the other hand, when the power is high, the heat is transmitted well upward, and the upper part cooks fluffy and deliciously, but the upper part (heat spot) of the induction heating coil softly collapses in the lower part, and the other parts become hard. In addition, although the rice in the places where high temperature water passes by convection contains a lot of water, the rice in other places has low temperature and cannot absorb water sufficiently. Therefore, there is a problem that cooked rice has a hard portion and a softly crumbled portion, and in particular, the larger the rice cooking capacity, the greater the unevenness in cooking. This phenomenon is particularly remarkable immediately before boiling when the convection inside the inner pot is activated and after boiling.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an inner pot containing rice and water by a high frequency magnetic field generated from an induction heating coil connected to an inverter circuit device. In an induction heating type rice cooker that heats and cooks rice, the power adjustment means that adjusts the power to heat the inner pot by changing the output of the inverter circuit device and the cooking process that keeps the boiling state Provided is an input power determining means for determining the optimum power to be input, and an increasing / decreasing means for increasing / decreasing the heating power of the inner pot by the power adjusting means on the basis of the input power determined by this input power determining part. The convection of heat inside was changed.

[0006]

According to the structure of the present invention, when the input power determining means determines the optimum power to be input according to the conditions such as the rice cooking capacity in the cooking process, the increasing / decreasing means determines the power based on the determined input power. The heating power of the inner pot is increased or decreased by the adjusting means. As a result, the convection condition of heat inside the inner pot is not always constant and becomes unstable. For this reason, the path through which hot water passes is changed by convection, so that only a part of the rice does not have hard portions or softly collapsed portions, and rice can be cooked with little unevenness in cooking.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of an induction heating type rice cooker according to an embodiment of the present invention, FIG. 2 is a configuration diagram of main parts of the induction heating type rice cooker, and FIG. 3 is a power change and temperature of the induction heating type rice cooker. It is a characteristic diagram.

In FIG. 1, a protective frame 2 forming an inner wall of the main body 1 is attached to the main body 1, and an induction heating coil 3 is attached to the bottom surface of the protective frame 2. An inverter circuit device 4 is attached inside the main body 1, and the inverter circuit device 4 is electrically connected to the induction heating coil 3.

An inner hook 5 is detachably inserted into the protective frame 2 and held therein. A temperature sensor 6 for obtaining temperature information is attached to the bottom of the protective frame 2, and is in contact with and thermally coupled to the bottom of the inner pot 5. A control unit 7 is provided inside the main body 1, and the control unit 7 is connected to the inverter circuit device 4 and a temperature sensor 6 for obtaining temperature information.

In FIG. 2, the control unit 7 includes a power adjusting unit 8 and a power input determining unit 9 for determining an optimum power input according to conditions such as a rice cooking process and a rice cooking capacity, and the input power in the cooking process. An increase / decrease unit 10 for increasing / decreasing the heating power of the inner pot by the power adjusting unit 8 is provided based on the input power determined by the determining unit 9. The operation of the inverter circuit device 4 is changed by the output of the power adjusting means 8 instructed by the increasing / decreasing means 10, the strength of the magnetic field from the induction heating coil 3 acting on the inner pot 5 is changed, and the inner pot 5 is heated. The power changes.

The operation of this embodiment having the above structure will be described below.

The user puts washed rice and an appropriate amount of water in the inner pot 5 and inserts it into the protective frame 2. Next, when a rice cooking switch (not shown) is operated, the rice cooking operation is started by the operation of the control unit 7. A high-frequency magnetic field is generated by the inverter circuit device 4 and the induction heating coil 3, and when this magnetic field passes through the inner pot 5, an eddy current is generated in the inner pot 5 and converted into Joule heat by the electric resistance of the inner pot 5. Fever. This heats rice and water to cook rice.

[0013] For cooking rice, "the beginning chopped chopsticks ..."
As it is said, it is indispensable to change the temperature of the fire as it progresses, raising the water temperature to about 40 ° C and performing a small amount of heating to maintain it, making it a “first chorochoro” that makes the rice suck water efficiently. Corresponding "preheating process". Then 10
"Heating process" that corresponds to "medium papper", which heats to boiling in about a minute. A "cooking process" that corresponds to "cooking a fire when you boil it" while boiling while boiling so that it will not spill over after boiling. Furthermore, it consists of a series of steps such as the "double-cooking step", which is equivalent to "straw a bunch of straws" in which rice absorbs water and is steamed after the water runs out, and excess heat is removed by a slight heating. ing.

Now, when the rice cooking is started by the operation of the user as described above, the "preheating step" is started. In the present embodiment, if the temperature of the temperature sensor 6 is lower than 40 ° C., the input power determination means 9 determines to heat at 200 W, and if it is 40 ° C. or higher, the input power determination means 9 determines to 0 W, that is, turns off. In the preheating step, the increasing / decreasing unit does not operate, and 200 W-0 W ON-OFF control is performed so as to maintain 40 ° C.

In the "preheating step", the temperature of the temperature sensor 6 is controlled to 40 ° C. as described above, so that the rice and water in the inner pot 5 are also kept at this temperature. This time,
As the amount of rice increases, the temperature of the temperature sensor 6 becomes lower than 40 ° C., and it takes a longer time to heat. Therefore, the rice cooking capacity is determined based on the required time. The "preheating step" ends after a lapse of a fixed time, for example, 15 minutes, and the "heating step" is started.

In the "heating step", the input power determining means 9 determines the power according to the rice cooking capacity determined in the "preheating step". For example, if it is determined to be 700 W, heating is performed at a constant 700 W, and when the temperature of the temperature sensor 6 reaches approximately 100 ° C., the “heating step” is ended and the “cooking step” is performed.

In the "cooking process" as well, the input power determining means 9 determines the power in accordance with the rice cooking capacity. Eg 7
If it is determined to be 00 W, the increasing / decreasing means 1 in this embodiment.
0 to 700W-1000W-0W-400W ... 5
The power changes every second, and the average value is increased or decreased so that the average value becomes 700 W determined by the input power determination means 9 with 30 seconds as one cycle. Further, the electric power adjusting means 8 operates in accordance with the electric power instructed by the increasing / decreasing means 10, the operation of the inverter circuit device 4 changes, and the electric power for heating the inner pot 5 changes. When rice absorbs water and the water inside the inner pot 5 runs out, the inner pot 5
When the temperature at the bottom suddenly rises and the temperature sensor 6 catches it, the process moves to the "double cooking step".

In the "double cooking step", when the temperature of the temperature sensor 6 falls below a certain level, the input power determining means 9 sets the temperature to 200.
Although it is decided to heat at W, the power adjusting means 8 is operated at 200 W as it is without interposing the increasing / decreasing means 10. When the temperature sensor 6 reaches a certain temperature or higher, heating is stopped. The "double-cooking process" ends after 15 minutes, and the rice is cooked.

Now, the effect of power increase / decrease by the increase / decrease means 10 in the above series of rice cooking process operations will be described below. The high-frequency magnetic field generated from the induction heating coil 3 passes through the protective frame 2 and acts on the inner pot 5 made of a magnetic material and installed on the protective frame 2. However, since the magnetic field right above the induction heating coil 3 is the strongest, the inner pot 5 has the highest heat just above the induction heating coil 3 (hereinafter referred to as a heat spot), and the rice and water around this are heated most. Although a large amount of water and rice exist inside the inner pot 5, the heated water rises and convection occurs.

Since the positional relationship between the induction heating coil 3 and the inner pot 5 does not change, the heat spot is substantially constant regardless of the heating power. However, the method of convection and the strength of convection change depending on the electric power. For example, when the electric power is low, the water in the heat spot portion is heated and tries to convect upward, but since rice is present, the resistance is large, and the heat convects only in the lower portion of the inner pot 5 and spreads laterally. On the contrary, when a high power is applied, the heat spot is heated strongly, overwhelming the resistance of the rice and violently convection upwards. As a result, the heat is transferred upward, but it is difficult to transfer the heat to the parts other than the heat spot on the bottom of the inner pot 5, which is in contact therewith. This phenomenon is prominent immediately before boiling when the inside of the inner pot 2 is violently retained and when the boiling state is maintained, that is, in the "cooking process".

Since the induction heating type rice cooker of the conventional structure is uniformly heated by the electric power determined as described above, the change in convection is small and cooking unevenness is likely to occur, but in the structure of the present invention, as described above, Since the power is finely changed by the increasing / decreasing means 10 every 5 seconds, the method and strength of convection are not stable and constantly change. For this reason, heat is evenly transmitted both upward and downward in the horizontal direction, and the temperature inside the inner pot 5 always rises at a substantially uniform temperature, so that there is little unevenness in cooking and the whole can be finished plumply and deliciously.

In the present embodiment, the unit time for changing the electric power by the increasing / decreasing means 10 is set to 5 seconds, but the object of the present invention is to increase / decrease the electric power in a relatively short time, and the present invention is not limited to this. Not, for example, 300W-3 seconds, 600W-
The power and time may be changed such as 10 seconds.

Further, in the present embodiment, the average value of the increase and decrease is set to coincide with the power determined by the input power determining means 9 with 30 seconds as one cycle, but this may be 10 seconds or 3 minutes. Further, in this embodiment, the constant power increase / decrease pattern is repeated as one cycle, but the average value may be indefinite as long as it follows the determination of the input power determining means 9. The point is that the condition that convection destabilization, which is the effect of the present invention, can be obtained, and is determined by the shape and the positional relationship between the induction heating coil 3 and the inner pot 5.

Here, if the operation of the input power determination means 9 is made very fine, such as every 5 seconds, and the input power is changed at any time, the effect of destabilizing the convection is produced as in this embodiment. The effect in this case is exactly the same as that of the present embodiment in which the increasing / decreasing means 10 is provided, and the increasing / decreasing means 1 is added to the input power determining means 9.
The function of 0 is included in the configuration of the present invention.

[0025]

As described above, in the present invention, the increasing / decreasing means for increasing / decreasing the heating power of the inner pot by the power adjusting means is provided on the basis of the input power determined by the input power determining means. As a result, the way of convection inside the inner kettle constantly changes, and the passage of hot water changes due to convection, so there is no hard part or soft crumbled part of the rice. It has the effect of providing an induction heating rice cooker that cooks delicious rice with little unevenness in cooking regardless of the amount.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an induction heating type rice cooker according to an embodiment of the present invention.

FIG. 2 is a main part configuration diagram of the induction heating rice cooker.

FIG. 3 is a power characteristic and temperature characteristic diagram of the induction heating type rice cooker.

[Explanation of symbols]

 3 induction heating coil 4 inverter circuit device 5 inner pot 8 electric power adjusting means 9 input electric power determining means 10 increasing / decreasing means

Claims (1)

[Claims] 1. An induction heating type rice cooker for induction-heating and cooking rice in an inner pot (5) containing rice and water by a high-frequency magnetic field generated from an induction heating coil (3) connected to an inverter circuit device (4). In the above, the power adjusting means (8) for adjusting the electric power for heating the inner pot (5) by changing the output of the inverter circuit device (4) and the charging process according to the conditions such as the rice cooking capacity in the boiling process for keeping the boiling state The input power determining means (9) for determining the optimum power to be used, and the power adjusting means (8) based on the input power determined by the input power determining means (9), sets the heating power for the inner pot (5). An induction heating type rice cooker characterized by comprising an increasing / decreasing means (10) for changing the convection of heat inside the inner pot (5) during rice cooking.