Rice cooker

Abstract

To provide a rice cooker capable of evenly cooking rice regardless of the amount of rice to be cooked.SOLUTION: A rice cooker according to the present invention includes a pot 7 for storing rice to be cooked, and a bottom heating element 11 for heating the pot 7. The pot 7 includes a substantially cylindrical side upper part 7a, a substantially disk-like bottom part 7b, a side lower part 7c extending from an outer periphery of the bottom part 7b and being connected to the side upper part 7a. The bottom part 7b is provided with a lowermost portion 7d in its outer peripheral portion that touches a flat surface when the pot 7 is placed on the flat surface, and is formed so as to become higher toward the center of the bottom part 7b. The side lower part 7c is formed so as to slope from the side upper part 7a toward the lowermost part 7d. The bottom heating element 11 includes a first IH heater 25 provided opposite the side lower part 7c, a second IH heater 26 provided opposite the lowermost part 7d, and a third IH heater 27 provided opposite the bottom part 7b. The heating amount of the first IH heater 25, the heating amount of the second IH heater 26, and the heating amount of the third IH heater 27 can be adjusted independently.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a rice cooker that cooks rice by varying the amount of heat from a heating means while a pot is being heated. [Background technology]

[0002] When cooking rice using a firewood stove, the flames of the firewood flicker, subtly changing the heat, heating the bottom and sides of the pot containing the food to be cooked.

[0003] In order to approximate this traditional cooking in a stove, techniques are known that change the amount of heat from the heating means while the pot is being heated. For example, Patent Documents 1 and 2 disclose a technique in which the bottom to side of the pot is divided into three blocks at 120° intervals from the bottom, with an independent induction heating (IH) coil placed in each block, and heating is performed by turning on and off electricity to each coil in a rotating sequence; Patent Documents 3 and 4 disclose a technique in which two independent coils at different heights are placed on the bottom and side of the pot, and heating is performed by alternately turning on and off electricity to each coil; Patent Document 5 discloses a technique in which an induction heating coil is placed from the bottom to the side of the pot, and the amount of heat of the coil is changed in stages over time to heat; and Patent Documents 6 and 7 disclose a technique in which an induction heating coil is placed from the bottom to the side of the pot, and the amount of heat of the coil is changed continuously over time to heat. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-162250 A [Patent Document 2] JP 2019-180533 A [Patent Document 3] Japanese Patent Application Publication No. 9-248242 [Patent Document 4] JP 2011-206142 A [Patent Document 5] JP 2008-220470 A [Patent Document 6] Japanese Patent Application Publication No. 11-214139 [Patent Document 7] JP 2020-4540 A Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned conventional technology is a technology for uniformly gelatinizing the rice throughout the pot by promoting water convection in the pot during cooking and heating the rice in the pot with water present evenly, but it is presumed that it is a technology that assumes the amount of cooked rice at the rated maximum cooking amount is an intermediate amount or more. Therefore, especially when the amount of cooked rice is less than an intermediate amount, there was a high risk of excessive gelatinization of the rice near the upper and lower sides of the pot in the cooked food, resulting in uneven cooking.

[0006] Therefore, an object of the present invention is to provide a rice cooker that can cook rice evenly regardless of the amount of rice being cooked. [Means for solving the problem]

[0007] In order to achieve the above object, the rice cooker of the present invention comprises a bottomed, cylindrical pot for containing food to be cooked, and a heating means for heating the pot, the pot having a substantially cylindrical upper side portion, a substantially disk-shaped bottom portion, and a lower side portion extending from the outer periphery of the bottom portion and connecting to the upper side portion, the bottom portion has a lowest portion at its outer periphery that comes into contact with a flat surface when the pot is placed on the flat surface, the lowest portion being formed so as to become higher towards the center of the bottom, the lower side portion having a shape that is inclined from the upper side portion towards the lowest portion, and the heating means is disposed opposite the lower side portion. The cooking rice cooker has a first IH heater arranged to face the lowest part, a second IH heater arranged to face the lowest part, and a third IH heater arranged to face the bottom part, and the heating amount of the first IH heater, the heating amount of the second IH heater, and the heating amount of the third IH heater are each configured to be independently adjustable, and the heating balance of the first IH heater, the second IH heater, and the third IH heater is adjusted according to the amount of the food to be cooked, and when the amount of the food to be cooked is large compared to the rated maximum cooking amount, (i) a heating balance for simultaneously heating the first, second and third IH heaters, then (ii) a heating balance for simultaneously heating the first and second IH heaters, then (iii) a heating balance for simultaneously heating the first and third IH heaters, and so on (i) to (iii) The heating balance is repeated in sequence. Effect of the Invention

[0008] According to the rice cooker of the present invention, the stability of the pot when placed on a stand or the like can be ensured, and the risk of the bottom of the pot deforming due to thermal expansion when the temperature of the pot rises can be prevented. In addition, the external convection generated by the heating of the first IH heater can be promoted, and the blowing up effect from the bottom of the internal convection generated by the heating of the second IH heater and the third IH heater can be promoted. Furthermore, the heating balance and heating amount of the first to third IH heaters are independently adjusted to suit the amount of rice cooked, depending on the amount of rice cooked at the rated maximum cooking amount, which is a large amount, a medium amount, or a small amount, so that rice can be cooked evenly regardless of the amount of rice cooked, and especially rice can be cooked evenly with an amount of rice cooked of less than a medium amount. [Brief description of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic explanatory diagram showing a rice cooker according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view and a schematic plan view showing the main parts around the bottom heater. [Diagram 3] FIG. 2 is a block diagram showing the electrical configuration of the rice cooker. [Figure 4] FIG. [Diagram 5] 13 is a graph showing the change over time in the pot temperature, the lid temperature, the amount of heat from the lid heating means, and the amount of heat from the bottom heater and side heater during the rice cooking process and the keeping warm process of the same. [Figure 6] Graphs showing (A) the change over time in the amount of heat applied to the pot by the rice cooking control means and (B) the change over time in the amount of heat applied to the pot by the heat amount fluctuation means. [Figure 7] 13 is a graph showing the change over time in the amount of heat applied to the pot by the heat amount fluctuation means. [Figure 8] 13 is a graph showing the relationship between the amount of heat and time when heated to high heat. [Figure 9] The graph shows the relationship between the amount of heat and time at medium heat. [Figure 10] 13 is a graph showing the relationship between the amount of heat and time at low heat. [Figure 11] 1A and 1B are a schematic cross-sectional view and a schematic plan view showing a main part around a bottom heating element of a conventional rice cooker. [Figure 12] This is a diagram showing the transfer of heat within the pot when the rice being cooked is a medium or larger amount. [Figure 13] As above, (A) is a diagram showing the transfer of heat within the pot when cooking a medium amount of rice with the heating balance of the bottom heating element set for a large amount, and (B) is a diagram showing the transfer of heat within the pot when cooking a small amount of rice with the heating balance of the bottom heating element set for a large amount. [Figure 14] FIG. 4 is a diagram showing a change in the heating balance of the first to third IH heaters when a large amount of food is being cooked in the rice cooker showing the first embodiment of the present invention. [Figure 15]FIG. 11 shows the transfer of heat within the pot when there is a large amount of food being cooked. [Figure 16] FIG. 11 shows the change in the heating balance of the first to third IH heaters when the amount of food being cooked is medium. [Figure 17] This is a diagram showing the transfer of heat within the pot when the amount of rice being cooked is medium. [Figure 18] FIG. 11 shows a change in the heating balance of the first to third IH heaters when the amount of rice to be cooked is small. [Figure 19] FIG. 11 shows the heat transfer within the pot when there is a small amount of food being cooked. [Figure 20] FIG. 11 is a diagram showing a change in the heating balance of the first to third IH heaters when the amount of rice to be cooked is medium or more in the rice cooker showing a modified example of the first embodiment. [Figure 21] FIG. 11 shows the change in the heating balance of the first to third IH heaters when the amount of food being cooked is less than a medium amount. [Figure 22] FIG. 11 is a top view of a display operation unit of the rice cooker showing a further modified example of the first embodiment. [Figure 23] FIG. 11 is a top view of a display operation unit of the rice cooker showing a further modified example of the first embodiment. [Figure 24] The same as above, this is a table of rice producing areas and rice brands stored in the memory means. [Diagram 25] As above, this is a table in which brands are arranged in the corresponding matrix columns according to the texture of the variety and brand of rice from each producing region, based on cooked texture information of the variety and brand of rice. [Figure 26] FIG. 11 is a top view of a display operation unit of the rice cooker showing a further modified example of the first embodiment. [Figure 27] 5A and 5B are a schematic cross-sectional view and a schematic plan view showing a main part around a bottom heating element of a rice cooker according to a second embodiment of the present invention. [Figure 28] FIG. 11 shows the change in the heating balance of the first to third IH heaters when the amount of food being cooked is medium or more. [Figure 29] This is a diagram showing the transfer of heat within the pot when the amount of rice being cooked is medium or more. [Diagram 30]FIG. 11 shows changes in the heating balance of the first to third IH heaters and changes in heat transfer within the pot when the amount of cooked rice is medium or more. [Diagram 31] FIG. 11 shows a change in the heating balance of the first to third IH heaters when the amount of rice to be cooked is small. [Diagram 32] FIG. 11 shows the heat transfer within the pot when there is a small amount of food being cooked. [Diagram 33] FIG. 11 is a schematic cross-sectional view showing a main part around a bottom heating element of a rice cooker according to a third embodiment of the present invention. [Diagram 34] FIG. 11 shows the transfer of heat within the pot when there is a large amount of food being cooked. [Diagram 35] This is a diagram showing the transfer of heat within the pot when the amount of rice being cooked is medium. [Diagram 36] FIG. 11 shows the heat transfer within the pot when there is a small amount of food being cooked. [Figure 37] FIG. 11 is a schematic cross-sectional view showing a main part around a bottom heating element of a rice cooker showing a modified example of the third embodiment of the present invention. [Figure 38] FIG. 11 is a schematic cross-sectional view showing a main part around a bottom heating element of a rice cooker showing a further modified example of the third embodiment of the present invention. [Figure 39] Same as above, (A) is a diagram showing the transfer of heat within the pot when there is a large amount of food being cooked, and (B) is a diagram showing the transfer of heat within the pot when there is a small amount of food being cooked. [Diagram 40] 13 is a graph showing the changes over time in the pot temperature, the lid temperature, the heating patterns of the first to third IH heaters, and the amount of heat of the bottom heater and side heater during the rice cooking process and the warming process of a rice cooker according to a fourth embodiment of the present invention when the amount of rice being cooked is small. [Diagram 41] This is a graph showing the changes over time in the pot temperature, lid temperature, heating pattern of the first to third IH heaters, and heat amount of the bottom heater and side heater when the amount of rice being cooked is medium during the rice cooking process and the keeping warm process. [Diagram 42]This is a graph showing the changes over time in the pot temperature, lid temperature, heating pattern of the first to third IH heaters, and heat amount of the bottom heater and side heater during the rice cooking process and the keeping warm process when a large amount of rice is being cooked. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments of the rice cooker according to the present invention will be described with reference to the accompanying drawings. In addition, common parts are designated by common reference numerals throughout the drawings. EXAMPLES

[0011] 1 to 10 and 14 to 18 show a first embodiment of the rice cooker of the present invention. First, the overall configuration of the rice cooker in this embodiment will be described with reference to Fig. 1. Reference numeral 1 denotes a main body with an open top, and reference numeral 2 denotes an openable and closable lid that covers the open top of the main body 1, and the appearance of the rice cooker is formed by the main body 1 and the lid 2. On the top surface of the lid 2, a display operation unit 5 is disposed which collectively arranges a display section 3 such as LEDs 64 to 66 and an LCD 63, which will be described later, and an operation section 4 such as operation keys and a touch panel. The display operation unit 5 may be disposed on the main body 1 instead of the lid 2.

[0012] The main body 2 has a pot housing section 6 that is open at the top, and when the lid 3 is opened, a bottomed, cylindrical pot 7 that serves as a container for holding water or rice, which is the food to be cooked S, can be detachably housed therein. When the pot 7 is placed in the main body 1 and the lid 2 is closed, an inner lid 8 attached to the underside of the lid 2 closes the open top of the pot 7, thereby sealing off the steam generated from the pot 7.

[0013] The pot storage section 6 is constructed by combining a bowl-shaped inner frame 9 made of resin such as polyethylene terephthalate resin containing glass fiber, which has excellent insulating properties, heat resistance, and flame retardancy, and a metal inner frame ring 10, and is formed into a cylindrical shape with a bottom so that there is a space between the pot 7 stored in the pot 7 and the inner frame 9. A bottom heating element 11 made of an IH (induction heating) heater is disposed on the outer surface of the inner frame 9, which faces the bottom surface of the pot 7 from the lower side of the pot 7, as a heating means for heating the pot 7 to cook the food S to be cooked, and a side heating element 12 made of a cord heater is disposed on the outer surface of the inner frame ring 10, which faces the outer surface of the pot 7. The side heating element 12, which serves as an auxiliary heating means for the pot 7, is disposed opposite the upper side of the pot 7, and when the side heating element 12 is energized, it is configured to heat mainly the upper side of the pot 7 with radiant heat from the side heating element 12. The pot 7 and the bottom heating element 11 will be described in detail later.

[0014] An insertion hole 9a is provided in the center of the inner frame 9, and a thermistor-type pot temperature sensor 15 is disposed in the main body 1, which passes through this insertion hole 9a and abuts against the inner center 7e (see Figure 2) of the outer bottom surface, which is the outer surface of the bottom of the pot 7. Pot temperature sensor 15, which serves as a pot temperature detection means, detects the temperature of the bottom of pot 7 and mainly controls the heating temperature of the bottom of pot 7 by bottom heating element 11.

[0015] During cooking and keeping warm, pot 7 is heated by the heating means, and during keeping warm, bottom heater 11 is heated and adjusted according to the temperature detected by pot temperature sensor 15 in contact with the outer bottom surface of pot 7, to keep pot 7 at a constant temperature. After cooking, side heater 12 is made to generate heat until the temperature of the freshly cooked rice in pot 7, for example 100°C, drops to a keeping temperature, for example 73°C, and then during stable keeping at the keeping temperature, side heater 12 is made to generate heat, preventing the rice from cooling due to outside air entering through the gap between main body 1 and lid 2, and heating mainly the upper side of pot 7.

[0016] The lid body 2, which opens and closes the upper opening of the pot 7, is equipped with a thermistor-type lid temperature sensor 16 that detects the temperature of the inner lid 8, a pressure sensor 17 that detects the internal pressure of the pot 7, and a lid heater 18 such as a cord heater. The lid temperature sensor 16 and the lid heater 18 mainly control the temperature of the inner lid 8 by the lid heating means 23, and when the inner lid 8 is attached to the lid body 2, the lid temperature sensor 16 comes into contact with the top surface of the inner lid 8, and the lid heater 18 is disposed opposite the top surface of the inner lid 8.

[0017] A pressure regulating valve 20 including a ball-shaped valve body 19 is disposed approximately in the center of the inner lid 8 constituting the underside of the lid body 2. The pressure regulating valve 20 is disposed midway through the steam passage space that communicates between the inside of the pot 7 and the outside of the lid body 2, i.e., the outside of the rice cooker (outside the machine), and a movable mechanism such as a solenoid (see FIG. 3) that moves the valve body 19 forward or backward into or out of the pressure regulating valve 20 is provided inside the lid body 2. With this configuration, when the valve body 19 advances into the pressure regulating valve 20 and blocks the steam passage space, the inside of the pot 7 can be pressurized to above atmospheric pressure until the pressure inside the pot 7 increases as the pot 7 is heated and pushes up the valve body 19, and when the valve body 19 retreats from the pressure regulating valve 20 to open the steam passage space, the inside of the pot 7 can be maintained at atmospheric pressure regardless of how the pot 7 is heated. Pressure sensor 17 is provided inside lid 2 facing pressure regulating valve 20, however, the present invention is not limited to this and may be provided in another location as long as it can detect the pressure inside pot 7.

[0018] FIG. 2 is a schematic diagram showing the main parts around the bottom heater 11. The pot 7 is mainly composed of a substantially cylindrical upper side 7a, a substantially disk-shaped bottom 7b, and a lower side 7c extending from the outer periphery of the bottom 7b and connecting to the upper side 7a. The base material of the pot 7 is an aluminum-based material with excellent thermal conductivity, and is formed by joining a heating element made of a stainless steel material, which is a magnetic metal that is excellent in heat generation by IH heating, from the lower side 7c of the outer surface of the base material to the bottom 7b. The inside of the pot 7 is coated with a pot inner surface fluorine coat (not shown) made of, for example, polytetrafluoroethylene (PTFE) or Teflon (registered trademark). The bottom 7b has a lowermost part 7d, which is a part that abuts against a flat surface when the pot 7 is placed on a flat surface such as a table, on the outer periphery of the outer bottom surface, which is the outer surface of the bottom 7b. The height of the bottom 7b is formed so that it becomes higher toward the center, and is formed so that it becomes higher from the lowermost part 7d toward the inner center 7e of the outer bottom surface. Therefore, the stability of the pot 7 when placed on a stand or the like can be ensured, and the risk of deformation of the bottom of the pot 7 due to thermal expansion can be prevented when the temperature of the pot 7 rises during the rice cooking process, the warming process, etc. The diameter of the bottom 7b is smaller than the diameter of the upper side 7a, so that the lower side 7c is inclined from the upper side 7a toward the lowest part 7d, which is the outer periphery of the bottom 7b, or is composed of an inclined curved surface, or is composed of a combination of inclination and curved surfaces, and the lower outer side surface, which is the outer surface of the lower side 7c, is similarly configured. As a result, the external convection C1 generated by the heating of the first IH heater 25 can be promoted as described later. Furthermore, such a shape of the pot 7 can promote the blowing up effect from the bottom 7b of the pot 7 of the internal convections C2 and C3 generated by the heating of the second IH heater 26 and the third IH heater 27, as described later.

[0019] The bottom heating body 11 of this embodiment is composed of a first IH heater 25 as a first bottom heating means, a second IH heater 26 as a second bottom heating means, and a third IH heater 27 as a third bottom heating means. The first IH heater 25, the second IH heater 26, and the third IH heater 27 are each provided on the outer surface of the inner frame 9, the first IH heater 25 is disposed as a side lower IH heater facing the outer side lower part of the side lower part 7c, the second IH heater 26 is disposed as a bottom outer heater facing the lowest part 7d of the bottom part 7b, and the third IH heater 27 is disposed as a bottom inner heater facing the outer bottom surface from the lowest part 7d of the bottom part 7b to the inner center part 7e.

[0020] The heating amount of the bottom heater 11 is configured such that the first IH heater 25 is 0 to 450 W, the second IH heater 26 is 0 to 550 W, and the third IH heater 27 is 0 to 400 W, totaling 0 to 1400 W. In this embodiment, the heating balance is such that the third IH heater 27 has the smallest heating amount, and in this example, the first IH heater 25 ≦ the second IH heater 26 ≧ the third IH heater 27, but the first IH heater 25 ≧ the second IH heater 26 ≧ the third IH heater 27 may also be satisfied. In addition, these numerical values ​​are only examples, and the heating amounts of the first IH heater 25, the second IH heater 26, and the third IH heater 27 and the magnitude of the heating amount may be set arbitrarily according to the heating characteristics of the rice cooker 1.

[0021] FIG. 3 shows the electrical configuration of the rice cooker in this embodiment. In the figure, 31 is a control unit that is built into the main body 1 and the lid 2 and includes a microcomputer and drive elements for each unit. The input port of the control unit 31 is electrically connected to the operation unit 4, the pan temperature sensor 15, the lid temperature sensor 16, and the pressure sensor 17. The output port of the control unit 31 is electrically connected to the display unit 3, the first IH heating drive unit 32 connected to the first IH heater 25, the second IH heating drive unit 33 connected to the second IH heater 26, the third IH heating drive unit 34 connected to the third IH heater 27, the side heating drive unit 35 connected to the side heating element 12, and the lid heating drive unit 36 ​​connected to the lid heating element 18. The control unit 31 is built with a storage means 37 such as a readable and writable memory that stores various information and data.

[0022] The control unit 31 receives operation signals from the operation unit 4 and each detection signal from the pot temperature sensor 15, the lid temperature sensor 16 and the pressure sensor 17, and outputs a display control signal to the display unit 3 at a predetermined timing based on the timing from a timer (not shown) serving as an internal timing means, and also has the function of outputting heating control signals to the first IH heating drive unit 32, the second IH heating drive unit 33 and the third IH heating drive unit 34 serving as the bottom heating body 11, the side heating drive unit 35 and the lid heating drive unit 36. These functions are realized by the control unit 31 reading a program pre-recorded in the storage means 37 as a storage medium, and the control unit 31 is provided with programs that mainly cause the control unit 31 to function as rice cooking control means 41 that heats the rice and water to be cooked S in the pot 7 to cook the rice, heat keeping control means 42 that maintains the rice in the pot 7 at a predetermined heat keeping temperature when keeping it warm, display control means 43 that receives an operation signal from the operation unit 4 and controls the display operation of the display unit 3, and heat amount fluctuation means 44.

[0023] The first IH heating drive unit 32, the second IH heating drive unit 33, and the third IH heating drive unit 34 are equipped with a power supply circuit 44 common to the units 32 to 34, inverters 32-1, 33-1, and 34-1, and IH drive circuits 32-2, 33-2, and 34-2 as main components. The power supply circuit 44 corresponds to a rectifying and smoothing circuit that converts a commercial power supply voltage of, for example, AC 100V supplied to the main body 1 into a DC voltage, and the DC voltage from the power supply circuit 44 is applied as an input voltage to the inverters 32-1, 33-1, and 34-1, respectively.

[0024] Although inverters 32-1, 33-1, and 34-1 are not shown in the figure, they are well-known voltage-type resonant inverters that are connected in parallel with first IH heater 25, second IH heater 26, and third IH heater 27, which serve as bottom heating body 11, respectively, to form respective resonant circuits, and that include switching elements such as IGBTs that are connected in series with each of these resonant circuits.

[0025] The IH drive circuits 32-2, 33-2, and 34-2 receive the respective heating control signals from the control unit 31 and send to the gates of the switch elements a pulse drive signal sufficient to turn on and off the respective switch elements of the inverters 32-1, 33-1, and 34-1. As a result, when the IH drive circuits 32-2, 33-2, and 34-2 provide the gates of the respective switch elements, the emitter-collector of each switch element is repeatedly turned on and off, and the power supply voltage from the power supply circuit 44 is intermittently applied to the resonant circuits of the respective inverters 32-1, 33-1, and 34-1, and high-frequency currents are supplied to the first to third IH heaters 25-27, respectively. At this time, by changing the period of the pulse drive signal and the ratio of the on time to one period (on time ratio), the output power from the inverters 32-1, 33-1, and 34-1, i.e., the amount of heating from the first to third IH heaters 25-27 to the pot 7, can be increased or decreased.

[0026] The side heating drive unit 35 receives a heating control signal from the control unit 31 and supplies the commercial power supply voltage to be applied to the power supply circuit 44 to the cord heater which constitutes the side heating element 12. Similarly, the lid heating drive unit 36 ​​receives a heating control signal from the control unit 31 and supplies the commercial power supply voltage to be applied to the power supply circuit 44 to the cord heater which constitutes the lid heating element 18. The control unit 31 also has the function of sending a control signal to the movable mechanism 21 which moves the valve element 19 to turn it on and off.

[0027] The rice cooking control means 41, upon receiving an instruction to start cooking rice via operation of the operating unit 4, sequentially carries out each of the steps of soaking cooking, which promotes the absorption of water by the rice in the food A to be cooked placed in the pot 7, boiling heating, which raises the temperature of the food S to boiling in a short period of time, continuing the boiling by keeping the food S boiling and bringing it to a dry-up state where there is no water, and steaming, which maintains the food S in the dry-up state at a high temperature but not so high that it burns, and cooks it into rice, thereby heating and cooking the food S contained in the pot 7 at the desired pressure. In this embodiment, for all cooking courses that can be used by the rice cooker to cook rice, a first pattern is stored in advance in the memory means 37, which indicates how the display unit 3, bottom heating element 11, side heating element 12, and lid heating element 18 should be operated as each cooking process from the aforementioned soaking cooking to steaming progresses, thereby changing the amount of heat applied from the bottom heating element 11, side heating element 12, and lid heating element 18 to the food S in the pot 7.When the user operates the operation unit 4 to select any desired cooking course from a number of cooking courses and then issues a command to start cooking, the rice cooking control means 41 reads out the first pattern corresponding to the selected cooking course from the memory means 37, and appropriately controls the bottom heating element 11, side heating element 12, and lid heating element 18 to cook the food S placed in the pot 7.

[0028] When the rice cooking control means 41 is operating the bottom heating element 11, the side heating element 12, and the lid heating element 18 to heat the pot 7 according to a first pattern corresponding to the selected rice cooking course, the heat amount fluctuation means 44 generates a second pattern different from the first pattern as necessary, and changes the amount of heat from the bottom heating element 11, the side heating element 12, and the lid heating element 18 to the food S in the pot 7 over time based on the second pattern. The heat amount fluctuation means 44 will be described in detail later.

[0029] The warming control means 42 controls the rice in the pot 7 to be kept at a predetermined warming temperature according to the first pattern corresponding to the selected rice cooking course described above, and is configured so that when the rice cooking control means 41 finishes cooking the rice S, the warming control means 42 automatically starts keeping the rice warm, regardless of the selected rice cooking course. The warming control means 42 also has a warming reheating function that controls the operation of the bottom heater 11 so that the temperature of the rice in the pot 7 is temporarily higher than the warming temperature when reheating is instructed by operating the operation unit 4 during warming. Furthermore, even if the main body 1 is in the off state immediately after commercial power is turned on and the operation unit 4 is instructed to start keeping the rice warm, the warming control means 42 can keep the rice S in the pot 7 warm.

[0030] The display control means 43 is configured to select and set conditions that can be selected by the operation unit 4 based on an operation signal from the operation unit 4, for example, to select and set a desired cooking course or rice cooking course from a plurality of cooking courses or rice cooking courses.

[0031] FIG. 4 is a top view of the display operation unit 5. The LED 65 of "cooking rice" on the display section 3 of the display operation unit 5 is lit to indicate that the rice is in the cooking process, and "white rice", "3.0" and "normal" are selected and displayed on the LCD 63 of the display section 3. Explaining with reference to FIG. 3, the operation section 4 is composed of a reservation key 51, a forward key 52, a back key 53, a menu key 54, a texture key 55, and an off key 56 arranged side by side on the right side of the display operation unit 5, as well as a cooked rice amount key 57 arranged side by side on the lower side of the display operation unit 5, a cooked rice key 58, a keep warm key 59, and a touch sensor 60 arranged on the upper surface of the LCD 63. Here, each key 31 to 39 cannot be operated by the user's touch operation, but functions as a push-type operation means such as a tact switch that can be operated by pressing, and the touch sensor 40 functions as a non-push-type operation means such as a touch key that can be operated by the user's touch operation by being connected to a control PC board not shown.

[0032] The rice cooking key 58 is operated when starting rice cooking, and when the rice cooking key 58 is pressed, the operation signal from the rice cooking key 58 is received by the rice cooking control means 41, which controls the start of rice cooking for the food S in the main body 1. The keep warm key 59 is operated when keeping rice warm, and when the keep warm key 59 is pressed, the operation signal from the keep warm key 59 is received by the keep warm control means 42, which controls the start of keeping rice warm and reheating the food S in the main body 1.

[0033] The off key 56 is operated to stop cooking rice or keeping it warm. When the off key 56 is pressed, the operation signal from the off key 68 is received by the rice cooking control means 41 or the keep-warm control means 42, which then stops heating the food S to be cooked in the main body 1 and switches the cooking device to the off state.

[0034] The reservation key 51 is operated when reserving rice cooking. When the reservation key 51 is pressed and the reserved time and cooking course are set, and then the rice cooking key 58 is pressed, the reservation rice cooking means 55 receives an operation signal from the rice cooking key 58 and controls the rice cooking control means 41 to start cooking so that the food S in the main body 1 is cooked at the previously set reserved time, and also controls the keep-warm control means 42 to start keeping the food warm.

[0035] The forward key 52 and the back key 53 are used to set the menu, texture, and amount of cooked rice on the selection screen described below, as well as to adjust the reservation time, current time, and cooking time.

[0036] The menu key 54 is operated when setting the rice menu, such as "white rice" or "brown rice", and when the menu key 52 is pressed, the display control means 43 accepts an operation signal from the menu key 52 and transitions to a selection screen for the rice menu. The texture key 55 is operated when setting the rice cooking method, such as the hardness or stickiness of the cooked rice, such as "crisp" or "fluffy", and when the texture key 55 is pressed, the display control means 43 accepts an operation signal from the texture key 55 and transitions to a selection screen for the rice texture. The cooked rice amount key 57 is operated when setting the amount of cooked rice for the food S, and when the cooked rice amount key 57 is pressed, the display control means 43 accepts an operation signal from the cooked rice amount key 57 and transitions to a selection screen for the amount of cooked rice. In these selection screens, the forward key 64, the back key 65 and the touch sensor 73 are used to select and set the rice menu, texture and amount of rice to be cooked, respectively.

[0037] The touch sensor 60 is configured such that a plurality of components are arranged as touch keys, each of which is formed by connecting a transparent electrode portion made of a conductive polymer with a contact portion connected to a control PC board (not shown) by pattern wiring. When a fingertip is touched with any of a plurality of display elements 67 displayed on the LCD 63 below the touch sensor 60, the touch key arranged above that display element 67, which corresponds to that display element 67, is touched and the display element 67 is selected.

[0038] The display unit 3 consists of an LCD 63 that displays the current time, the scheduled time for completion of cooking, the selected rice menu, texture, and amount of cooked rice, and an LED 64 marked "Reservation," an LED 65 marked "Cook," and an LED 66 marked "Keep Warm," which are arranged side by side on the upper part of the display operation unit 5 and display the cooking process of the rice cooker. Referring to Figure 4, the display elements 67 arranged on the LCD 63 are as follows: a clock display element 67-1 that displays the current time, cooked rice reservation display elements 67-2, 67-3 that display the reserved time for cooking to be completed when reservation cooking is set, a cooked rice amount display element 67-4 that displays the selected amount of cooked rice, a "white rice" display element 67-5 that lights up to display the selected menu, a "burnt white rice" display element 67-6, a "brown rice" display element 67-7 and a "porridge" display element 67-8, a "crisp" display element 67-9 that lights up to display the selected texture, a "normal" display element 67-10 and a "fluffy" display element 67-11.

[0039] Next, the operation of the rice cooker main body 1 in the rice cooking process will be described with reference to Fig. 5. Fig. 5 shows the relationship between the pot temperature t1 detected by the pot temperature sensor 15, the lid temperature t2 detected by the lid temperature sensor 16, and the heat amount P L and the heating amount P of the bottom heater 11 and the side heater 12. H The graphs show the changes over time in and . In the figure, a shows boiling detection by the change in the rate of temperature rise of the pot temperature t1, b shows boiling detection by the change in the rate of temperature rise of the lid temperature t2, and c shows cooking detection that detects the dry-up state by the change in the rate of temperature rise of the pot temperature t1.

[0040] To explain the operation of this embodiment during rice cooking, first rice and water are placed in the pot 7 as the food S to be cooked, and the pot 7 is then placed in the pot housing 6, after which the lid 3 is closed. Around the same time, when electricity is applied to the rice cooker main body 1, the main body 1 goes into the initial off (standby) state in which neither cooking nor keeping rice warm is taking place, and the display control means 43 causes the LCD 63 to display the current rice cooking course setting.

[0041] Here, each time the operation unit 4 is operated, for example, the menu key 54, the texture key 55, the rice cooking amount key 57, the forward key 26, the back key 27, or the touch sensor 34, the operation signal is received by the display control means 43, and the setting of the rice cooking course is changed by this display control means 43. The changed setting is displayed on the LCD 63 by the display control means 43 each time, and the user can visually confirm this. If the rice cooking process is started without selecting the rice cooking amount with the rice cooking amount key 57, the display control means 43 controls the LCD 63 so that "-- (automatic)" is displayed on the rice cooking amount display element 67-4, and the setting of the rice cooking amount is calculated and determined based on the temperature rise rate of the pot temperature t1 and the lid temperature t2 during the rice cooking process, as described later.

[0042] When the operating unit 4, for example, the rice cooking key 58 is operated, the operation signal is received by the control unit 41, and the rice cooking control means 41 of the control unit 41 stores the rice cooking course displayed on the LCD 63 in the storage means 37 as the currently set rice cooking course, and the rice cooking control means 41 performs each of the rice cooking operations, which are the rice cooking process for the food S in the pot 7, including the soaking cooking process, the boiling heating process, the continued boiling process, and the high temperature holding process, according to the heating pattern of the set rice cooking course. In this embodiment, the heating balance indicating the ON / OFF pattern of the bottom heating body 11, i.e., the first to third IH heaters 25-27, is changed depending on the amount of rice cooked in the set rice cooking course. The heating balance of the first to third IH heaters 25-27 in the rice cooking process will be explained in detail later.

[0043] Meanwhile, the heat amount fluctuation means 44 generates a second pattern in which the amount of heat to the pot 7 by induction heating is increased or decreased every 100 ms (0.1 seconds) to 1 s (1 second) in a cycle of 1 to 10 seconds in response to the change in the amount of heat to the pot 7 over time by the rice cooking control means 41, which is based on the traditional fire control for cooking in a stove: "Trickle at first, puff up in the middle, turn off the heat when it starts to sizzle, burn a handful of straw, and don't take off the lid even if the baby cries." The sum of the outputs of the first to third IH heaters 25 to 27, which corresponds to the amount of heat from the bottom heating body 11, changes to, for example, about 200 W in total. Then, a heating configuration that assumes the fluctuation of a firewood flame is added so that the amount of heat based on this second pattern is given from the bottom heating body 11 to the pot 7.

[0044] That is, "Start trickling" is a low heat with a gentle flame due to heating in the "soaking cooking" process, "Chu pappa" is a high heat with an intense flame due to heating until boiling in the "boiling heating" process, "Turn off the heat when it starts to sizzle" is a medium heat with a gentle flame until the rice is cooked while boiling continues in the "boiling heating" process, and "Burn a handful of straw, don't take the lid off even if the baby cries" is a low heat with a quiet flame for double cooking during the "soaking" process. In addition to the change in the amount of heat P1 to pot 7 as the process progresses by rice cooking control means 41 as shown in FIG. 6(A), a fluctuating change in the amount of heat P2 to pot 7 by heat amount fluctuation means 44 as shown in FIG. 6(B) is added.

[0045] Heat amount fluctuation means 44 sets output maintenance time D during which the output of inverter 37 is kept constant in the range of 0.1 to 1 second within cycle (period) C of 1 to 10 seconds, and increases or decreases the total output of first to third IH heaters 25 to 27 stepwise for each output maintenance time D, generating a second pattern in which output change amount E, which is the difference between the upper and lower limits of the total output of first to third IH heaters 25 to 27, changes to about 200 W, and applies a fluctuation change in heat amount P2 from bottom heater 11 to pot 7 in this second pattern. As a result, the final heat amount P His obtained by adding the heating amount P1, which is changed by the rice cooking control means 41, to the heating amount S2, which is changed so as to fluctuate by the heating amount fluctuation means 44.

[0046] Specifically, when the rice cooking key 58 is operated to start the rice cooking process, the rice cooking control means 51 outputs heating control signals to the first to third IH heating drive units 32 to 34 based on the temperature of the bottom of the pot 7 detected by the pot temperature sensor 15, controls the bottom heater 11 to be turned on or off, heats the bottom of the pot 7, and performs a soaking cooking process to raise the water temperature in the pot 5 to a predetermined temperature, for example, 35 to 55°C, or up to 60°C, as shown in Figure 5, to promote water absorption by the rice. The soaking cooking process is configured to maintain the water temperature in the pot 5 at a predetermined temperature for a predetermined time, for example, about 15 minutes, but this time may be changed as desired.

[0047] On the other hand, in order to achieve a gentle flame at low heat during the "soaking cooking" process, the heat amount fluctuation means 44 sets one cycle C of low heat in which the total output of the first to third IH heaters 25-27 is changed from 500W (lower limit) → 540W → 580W → 620W → 660W → 700W (upper limit) → 660W → 620W → 580W → 540W → 500W (lower limit), and sets one cycle C as 7 seconds for a gentle flame. As a result, the output maintenance time D during which each output is kept constant is set to 0.7 seconds, and a cycle of change in heat amount P2 such that the total output of the first to third IH heaters 25-27 varies every 0.7 seconds is repeatedly applied from the bottom heating body 11 to the pot 7.

[0048] After that, when the soaking process is completed for a certain period of time and the process moves to the next boiling and heating process, the power P H and power P LAs shown in Fig. 5, in the heating until boiling of the food S is detected, the rice cooking control means 51 outputs heating control signals to the first to third IH heating drive units 32-34 and the side heating drive unit 35 to control the continuous energization of the bottom heating element 11 and the side heating element 12, and outputs a heating control signal to the lid heating drive unit 35 to control the continuous energization of the lid heating element 18, heating the food S in the pot 7 more strongly than in the soaking cooking process. As a result, as shown in Fig. 5, the pot temperature t1 detected by the pot temperature sensor 15 and the lid temperature t2 detected by the lid temperature sensor 16 gradually rise.

[0049] Here, the rice cooking control means 51 controls the movable mechanism 21 to cause the valve body 19 to roll into the pressure regulating valve 20 to close the steam passage space and seal the inside of the pot 5, and since the food S to be cooked is strongly heated inside the pot 7 as described above, the food S to be cooked is pressurized inside the pot 5 until it reaches a pressure equal to or higher than atmospheric pressure, for example 1.2 atm, and the food S to be cooked can be boiled in this pressurized state. This ensures a balance between the hardness and stickiness of the rice by boiling the food S at 105°C (at 1.2 atm), which is the optimum gelatinization temperature for rice in a pressurized state.

[0050] The rice cooking control means 51 detects the amount of rice cooked in the pot 7 by calculating it based on the temperature rise rate of the pot temperature t1 and the temperature rise rate of the lid temperature t2 during the soaking cooking process and the boiling heating process. The rice cooking control means 51 then judges whether there is a difference between the amount of rice cooked in the currently set cooking course and the amount of rice cooked this time. If there is a difference, the currently detected amount of rice is given priority, and the rice cooking control means 51 is configured to control the bottom heater 11 with a heating pattern according to the amount of rice cooked this time in the cooking process after the judgment. The display control means 43 also controls the LCD 63 to switch the display of the rice cooking amount display element 67-4 to "-- (automatic)", so that the user can know that the rice cooking process will be performed with a heating pattern according to an amount of rice cooked different from the amount of rice cooked in the currently set cooking course. Therefore, for example, when the amount of rice to be cooked is mistakenly selected using the rice cooking key 58 when setting the rice cooking course, it is possible to prevent the rice from being overcooked when the amount of rice to be cooked is small but the heating amount is set to the amount required for a large amount of rice, and conversely, the rice is not being undercooked when the amount of rice to be cooked is large but the heating amount is set to the amount required for a small amount of rice.

[0051] In addition, even if the storage means 37 is operated, for example, when the battery or capacitor is depleted and the data cannot be stored in the storage means 37, or when data is lost from the storage means 37 due to a power outage, the rice cooking control means 51 is configured to give priority to the amount of rice cooked this time, and in the rice cooking process after that judgment, control the bottom heater 11 with the heating pattern according to the amount of rice cooked this time. Therefore, for example, when the setting of the amount of rice cooked cannot be stored, it is possible to prevent the above-mentioned risk of overheating or, conversely, the risk of underheating.

[0052] On the other hand, in order to realize high heat and an intense flame in the heating process of the boiling heating, the heat amount fluctuation means 44 sets one cycle C of high heat from the total output of the first to third IH heaters 25-27 going from 1200W (lower limit) → 1240W → 1280W → 1320W → 1360W → 1400W (upper limit) → 1360W → 1320W → 1280W → 1240W → back to 1200W (lower limit), and sets one cycle C for an intense flame to a minimum of 1 second. As a result, the output maintenance time D during which each output is kept constant is set to a minimum of 0.1 seconds, and a cycle of change in heat amount P2 such that the total output of the first to third IH heaters 25-27 varies stepwise every 0.1 seconds is repeatedly applied from the bottom heating body 11 to the pot 7.

[0053] Thereafter, when the rice cooking control means 41 detects from the temperature detection signal from the pot temperature sensor 15 that the pot temperature t1 has reached a predetermined temperature or higher, for example 90°C or higher, and also detects from the temperature detection signal from the lid temperature sensor 16 that the lid temperature t2 has reached a predetermined temperature or higher, for example 90°C, it starts boiling detection to detect boiling of the food to be cooked S under pressure. The rice cooking control means 41 then controls the continuous energization of the bottom heating element 11 and the side heating element 12, and also controls the continuous energization of the lid heating element 18 to strongly heat the food to be cooked S inside the pot 7, while calculating the slope of the detected temperature, i.e., how much the detected temperatures of the pot temperature sensor 15 and the lid temperature sensor 16 will rise in a predetermined time. Specifically, when the rice cooking control means 51 calculates that the rise in pot temperature t1, which is the temperature of the bottom of pot 7, from the temperature detected by pot temperature sensor 15 has fallen to a predetermined temperature rise rate or less, such as 3°C or less in 120 seconds, it determines that boiling has been detected due to a change in the temperature rise rate of pot temperature t1, as shown in Figure 5A. When the rice cooking control means 51 calculates that the rise in lid temperature t2, which is the temperature of inner lid 8, from the temperature detected by lid temperature sensor 16 has fallen to a predetermined temperature rise rate or less, such as 1°C or less in 60 seconds, it determines that boiling has been detected due to a change in the temperature rise rate of lid temperature t2, as shown in Figure 5B. The predetermined temperature rise rates of pot temperature t1 and lid temperature t2 for detecting boiling a and b are adjusted and set respectively according to the setting of the amount of rice cooked for the food S to be cooked.

[0054] When the rice cooking control means 51 detects boiling a due to a change in the rate of temperature rise of the pan temperature t1 and boiling b due to a change in the rate of temperature rise of the lid temperature t2, the process proceeds to the next boiling continuation process. When the process proceeds to the boiling continuation process, the rice cooking control means 41 outputs a heating control signal to the first to third IH heating drive units 32-34 and the side heating drive unit 35 to control the power supply and cut-off of the bottom heating element 11 and the side heating element 12 so that the pan temperature t1 detected by the pan temperature sensor 15 is maintained at a predetermined temperature, for example, 98°C or higher, and outputs a heating control signal to the third heating drive unit 44 to control the continuous power supply to the lid heating element 18 so that the lid temperature t2 detected by the lid temperature sensor 16 is maintained at a predetermined temperature, for example, 98°C or higher, thereby maintaining the boiling state of the food S to be cooked.

[0055] Here, the rice cooking control means 51 controls the movable mechanism 21 so that the valve body 19 retracts from the pressure regulating valve 20, opening the steam passage space, and connecting the inside of the pot 7 to the outside of the main body 1, and the steam from the food to be cooked S is released to the outside of the main body 1 through a steam vent not shown.

[0056] On the other hand, in order to achieve a medium heat and gentle flame during heating in the boiling continuation process, the heat amount fluctuation means 44 sets one cycle C of medium heat from 800W (lower limit) → 840W → 880W → 920W → 960W → 1000W (upper limit) → 960W → 920W → 880W → 840W → back to 800W (lower limit), and sets one cycle C as 4 seconds for a gentle flame.Therefore, the output maintenance time D during which each output is kept constant is set to 0.4 seconds, and a cycle of change in heat amount P2 such that the total output of the first to third IH heaters 25-27 varies stepwise every 0.4 seconds is repeatedly applied from the bottom heating body 11 to the pot 7.

[0057] When the rice cooking control means 51 calculates that the water inside the pot 5 has run out during the continuing boiling process and that the temperature at the bottom of the pot 7 has risen at a predetermined temperature rise rate, such as 0.5°C or more in 10 seconds, from the temperature detected by the pot temperature sensor 15, it determines that it has detected a change in the temperature rise rate of the pot temperature t1, as shown in Figure 5c, and moves on to the next steaming process.

[0058] During the steaming process, the rice cooking control means 53 controls the temperature by turning on and off the lid heater 22 according to the temperature detected by the lid temperature sensor 34 to prevent condensation on the inner lid 22, and also controls the temperature at the bottom of the pot 5 by turning on and off the bottom heater 11 and side heater 12 according to the temperature detected by the pot temperature sensor 15 to maintain a high temperature that will not burn the rice inside the pot 5. The steaming process continues for a predetermined time, for example 12 minutes.

[0059] On the other hand, in order to realize a quiet flame at low heat during the steaming process and the heating of the second cooking during steaming, the heat amount fluctuation means 44 sets one cycle C of the total output of the first to third IH heaters 25-27 from 500W (lower limit) → 540W → 580W → 620W → 660W → 700W (upper limit) → 660W → 620W → 580W → 540W → 500W (lower limit), and sets one cycle C to a maximum of 10 seconds for a quiet flame, and sets the output maintenance time D during which each output is kept constant to a maximum of 1 second, and repeatedly applies a cycle of change in heat amount P2 from the bottom heater 11 to the pot 7 such that the total output of the first to third IH heaters 25-27 varies stepwise every second. After the steaming process is completed, the process proceeds to a warming process by the warming control means 54.

[0060] As shown in Figure 7, the heating amount fluctuation means 44, which serves as a heating amount varying means, is configured to vary the heating amount S of the bottom heating body 11, which serves as a heating means, in a second pattern in which the heating amount P1 according to the first pattern executed by the rice cooking control means 41 is set as a reference value P1ave, and an upper limit value P2max of the heating amount P2 that is greater than the reference value P1ave and a lower limit value P2min of the heating amount P2 that is smaller than the reference value P1ave are periodically repeated.

[0061] 8 shows the relationship between the heating amount P2 and time at high heat in the above example where the total output of the first to third IH heaters 25-27 is in the range of 1200W to 1400W. As shown in FIG. 8(B), the heating amount fluctuation means 44 sets the heating amount P2 corresponding to high heat from six levels of heating amount P2 consisting of 1200W, 1240W, 1280W, 1320W, 1360W, and 1400W, and configures the fluctuation of the heating amount P2 by the length of the heating amount P2 at each level, i.e., the length of the output maintenance time D. For comparison, FIG. 8(A) shows an example in which the heating amount P2 is continuously and steplessly varied by the heating amount fluctuation means 44.

[0062] 9 shows the relationship between the heating amount P2 and time at medium heat when the total output of the first to third IH heaters 25-27 in the above example is in the range of 800W to 1000W. As shown in FIG. 9(B), the heating amount fluctuation means 44 sets the heating amount P2 corresponding to medium heat from six levels of heating amount P2 consisting of 800W, 840W, 880W, 920W, 960W, and 1000W, and configures the fluctuation of the heating amount S2 by the length of the output maintenance time D at each level. For comparison, FIG. 9(A) shows an example in which the heating amount P2 is continuously and steplessly varied by the heating amount fluctuation means 44.

[0063] Fig. 10 shows the relationship between the heating amount P2 and time at low heat when the total output of the first to third IH heaters 25-27 in the above example is in the range of 500W to 700W. As shown in Fig. 10(B), the heating amount fluctuation means 44 sets the heating amount P2 corresponding to low heat from six heating amount S2 stages consisting of 500W, 540W, 580W, 620W, 660W, and 700W, and configures the fluctuation of the heating amount P2 by the length of the output maintenance time D at each stage. For comparison, Fig. 10(A) shows an example in which the heating amount fluctuation means 44 varies the heating amount P2 continuously and steplessly.

[0064] In this way, the heating amount fluctuation means 44 is configured to set the heating amount band (range of heating amount P2) constituting the main parts of, for example, high heat, medium heat, and low heat, by multiple stages of heating amount including an upper limit value P2max, a lower limit value P2min, and an intermediate value P1ave. Therefore, it is not necessary to continuously vary the high-frequency pulse drive signal to the inverters 32-1, 33-1, and 34-1 that supply high-frequency current to the first to third IH heaters 25-27, respectively, and it is possible to simplify the circuit configuration of the first to third IH heating drive units 32-34 including the inverters 32-1, 33-1, and 34-1 and to reduce the size of the inverters 32-1, 33-1, and 34-1.

[0065] The heating amount fluctuation means 44 of this embodiment has a configuration for setting the upper limit P2max of the heating amount P2 so as not to exceed the rated power consumption of the rice cooker. The indication of the rated power consumption of the rice cooker is stipulated by the Electrical Appliance and Material Safety Law, and in the above example, even if the total output of the first to third IH heaters 25-27 is set to 1200W to 1400W at high heat, the power consumption fluctuates over time, making it difficult to inspect the power consumption on a manufacturing assembly line, etc. Therefore, the control unit 31 including the rice cooking control means 41 and the heating amount fluctuation means 44 controls and limits the total output of the first to third IH heaters 25-27 corresponding to the upper limit P2max of the heating amount P2 so that it does not exceed the rated power consumption of the rice cooker, or if it exceeds it, it is within 5%. Specifically, when the rated power consumption of the rice cooker is 1400W, the total output of the first to third IH heaters 25-27 is 1470W or less.

[0066] However, the rated power consumption of the rice cooker may include not only the heating from the bottom heating element 11 to the pot 7 by the heating coil, but also the heating of the lid 2 by the lid heating element 18 and the heating of the side of the pot 7 by the side heating element 12. Therefore, for example, if the power consumption of the lid heating element 18 is 50 W and heating is performed simultaneously with the bottom heating element 11, it is preferable to set the total power consumption of the bottom heating element 11 and the lid heating element 18 to 1350 W, which does not exceed the rated power consumption of the rice cooker, as the sum of the outputs of the first to third IH heaters 25 to 27, which corresponds to the upper limit value P2max of the heating amount P2.

[0067] In the above example, the total output of the first to third IH heaters 25 to 27 is in the range of 1200W to 1400W, and the lower limit P2min of the heating amount P2 is set to 1200W. However, in the case of an actual firewood fire, the heating power corresponding to the heating amount P2 to the pot 7 does not drop significantly instantaneously even if there is a fluctuation, so it is preferable that the heating amount fluctuation means 44 sets a limit on the lower limit SPmin so that the lower limit P2min of the heating amount P2 does not fall below 50% of the upper limit P2max. That is, if the upper limit P2max of the heating amount P2 is set to 1400W, the lower limit P2min of the heating amount P2 is limited not to fall below 700W. By configuring in this way, when the heating amount fluctuation means 44 adds fluctuation control to the heating amount S2 of the bottom heating body 11, there is no problem with the power consumption inspection at the time of manufacture, and it is possible to prevent problems such as a current exceeding the rated power consumption of the rice cooker and the limited current of the indoor wiring flowing in compliance with laws and regulations.

[0068] Figures 14 to 18 show the heating patterns of the first to third IH heaters 25 to 27 in this embodiment and the transfer of heat within the pot 7. For comparison, Figures 11 to 13 show the arrangement of a first IH heater 25' and a second IH heater 26' as a conventional bottom heating body 11' and the transfer of heat within the pot 7.

[0069] As shown in FIG. 11, the conventional bottom heating element 11' is composed of a first IH heater 25' and a second IH heater 26', and as shown in FIG. 12, the first IH heater 25' heats the lower part 7c of the side of the pot 7 to generate external convection C1 of heat within the pot 7, and the second IH heater 26' heats the bottom 7b of the pot 7 to generate internal convection C2 of heat within the pot 7, and the first IH heater 25' and the second IH heater 26' are alternately heated to alternately generate external convection C1 and internal convection C2 of heat within the pot 7. Alternatively, multiple IH heaters are arranged in multiple blocks, for example, at 120° or 60° intervals on the side lower portion 7c or bottom portion 7b of the pot 7, and the IH heaters of each block, which can be heated independently, are heated in rotation, so that the pot 7 is heated locally in rotation from the side lower portion 7c to the bottom portion 7b, causing complex heat convection in the pot 7. The arrangement and heating pattern of these IH heaters worked effectively when the food S to be cooked contained in the pot 7 was a medium or larger amount of rice cooked in the rated maximum cooking amount. In this specification, a cooking amount of 4 cups or more of rice is described as a large amount of rice cooked in the rated maximum cooking amount, 1.5 cups or more but less than 4 cups is a medium amount of rice cooked, and 1.5 cups or less is a small amount of rice cooked, but the present invention is not limited to this, and the numerical values ​​are merely examples.

[0070] However, with these IH heater arrangements and heating patterns, when the amount of rice cooked is small at the rated maximum cooking capacity, the water level of the food S contained in the pot 7 may be low and, for example, this water level may not reach the heating position of the first IH heater 25' which heats the lower side 7c of the pot 7, or the rice of the food S may sink to the bottom and so even if the water level reaches the heating position of the first IH heater 25' but only the water of the food S is at this heating position, there is a risk that the lower side 7c of the pot 7 may be overheated by the first IH heater 25'.

[0071] With reference to Fig. 12, the heating balance of the lower side and bottom of the pot 7 of a conventional rice cooker will be described. First, the thermal conductivity (k) of the pot 7 and the food S to be cooked will be described. The base material aluminum forming the inner shape of the pot 7 has a thermal conductivity of approximately 236 W / mK, the PTFT inner fluorine coating applied to the inner surface of the pot 7 has a thermal conductivity of approximately 0.25 W / mK, and water has a thermal conductivity of approximately 0.582 W / mK. Therefore, the thermal conductivity of the inner fluorine coating of the pot and water is extremely inferior to that of the base material. Since heat moves from a high temperature area to a low temperature area, when the pot 7 is heated by the first IH heater 25' or the second IH heater 26', the outer lower side of the lower side 7c of the pot 7 and the lowest part 7d of the bottom 7b, which are the parts facing the first IH heater 25' or the second IH heater 26', become hot first, and this heat moves to the upper side 7a of the pot 7 via the base material.

[0072] The heat of the pot 7 then travels through the fluorine coating on the inside of the pot to the water in the food S that is in contact with the fluorine coating on the inside of the pot. Here, since the food S is made up of water and rice, the rice acts as a thermal resistance in areas where rice is present, and the rice that absorbs heat and water becomes gelatinized. Therefore, the heat of the food S is mainly transferred together with the transfer of water, but the transfer of water is limited to the narrow gaps between the rice grains of the food S, and the transfer of water and heat from the water in the food S that is in contact with the fluorine coating on the inside of the pot, which is the high-temperature area described above, to the center of the pot 7, which is away from the fluorine coating on the inside of the pot, which is the low-temperature area described above, slows down. On the other hand, in areas where rice is not present, the transfer of water and heat becomes active due to convection, so that after the water in the food S that is in contact with the fluorine coating on the inside of the pot, the water in the upper part of the food S where rice is not present becomes hotter because rice sinks downward. Then, the water and heat from the upper part of the food S, which has become a high-temperature part, moves to the middle part of the food S, which is a low-temperature part, and then moves to the lower part of the food S. This phenomenon is known as thermal convection, and in this embodiment, it will be described as external convection C1.

[0073] The heat transferred from the lowest part 7d to the bottom part 7b is transferred via the fluorine coating on the inner surface of the pot to the water and rice of the food S that is in contact with the fluorine coating on the inner surface of the pot at the bottom part 7b. Here, in the lower part of the food S, the rice of the food S sinks downward, so the upper part of the lower part is covered with the rice of the food S and the water, and the temperature and pressure of this water rise. After that, the water with higher temperature and pressure in the lower part passes through the gaps between the rice grains of the food S and moves upward, and is blown upward, so that the water with the increased temperature in the lower part, i.e., the hot water, moves together with the heat to the middle part of the food S, and then to the upper part. This phenomenon is called blowing up, and in this embodiment it will be described as internal convection C2, C3.

[0074] Here, when the food item S is a large amount of rice to be cooked at the rated maximum cooking capacity, for example, as shown in Figure 12 (A), if the heating amount of the first IH heater 25' is too high and the heating at the lower part 7c of the side of the pot 7 is too strong, and the heating amount of the second IH heater 26' is too low and the heating at the bottom of the pot 7 is too weak, the temperature of the parts of the food item S near the upper part 7a and lower part 7c of the side of the pot 7 heated by the first IH heater 25' and nearby areas will rise higher than the surrounding area, and a strong external heat convection C1 will be generated inside the pot 7, causing the temperature of the upper part of the food item S to rise higher than the surrounding area, and the rice will gelatinize from the parts of the food item S where the temperature rise of the water is rapid, resulting in excessive gelatinization of the rice in the parts of the food item S near the upper part 7a and lower part 7c of the side of the pot 7 and in the upper part. On the other hand, the temperature of the middle and bottom layers of the food S tends to rise more slowly than the surrounding areas, so the rice in these middle and bottom layers tends to be insufficiently gelatinized. Since the rice in the food S expands due to gelatinization, when the food S is cooked, the rice around the sides of the pot 7, that is, the rice on the pot edge, rises due to excessive gelatinization, while the rice in the center of the food S does not rise as much and is depressed due to insufficient gelatinization in the middle and bottom layers, resulting in a cooked rice with a depressed center as a whole. When the rice is excessively gelatinized, the water content is too high, so the rice becomes watery and less sticky, like overcooked porridge or ochazuke. In this case, the rice on the pot edge and the rice in the upper layer of the food S becomes like this, which causes the overall taste of the rice to deteriorate.

[0075] On the other hand, as shown in Fig. 12(B), if the amount of heat from the first IH heater 25' is small and the heating at the lower part 7c of the side of the pot 7 is too weak, and the amount of heat from the second IH heater 26' is large and the heating at the bottom 7b of the pot 7 is too strong, the opposite of the case of Fig. 12(A) will occur, where the rice in the middle and lower parts of the food S will be over-gelatinized and the rice in the upper part of the food S will be under-gelatinized, resulting in a rise in the center of the food S as a whole. Here, while the rice in the middle and lower parts of the food S will expand, the rice in the upper part of the food S will be under-gelatinized and so the expansion will be suppressed, and the rice in this upper part will have a sticky, dumpling-like texture with no chewiness, which will also be a factor in the overall deterioration of the taste of the rice.

[0076] These also apply when the food S is cooked at a medium or lower amount of the rated maximum cooking amount. On the other hand, when the amount of heating of the first IH heater 25' is small and the heating of the lower side 7c is too weak, and the amount of heating of the second IH heater 26' is large and the heating of the bottom 7b is too strong, the distance between the middle and lower parts where the temperature of the food S rises higher than the surroundings and the upper part where the temperature of the food S rises slower than the surroundings is closer than when the amount of cooking is large, so the degree of cooking unevenness described above in Figure 10(B) is reduced. However, even if the total heating power of the first IH heater 25' and the second IH heater 26' is reduced, for example, from 1400 W or 1200 W to 1000 W or 800 W in response to a decrease in the amount of cooked rice of the food S, if the heating balance of the first IH heater 25' and the second IH heater 26' for a large amount of cooked rice is the same as that described above in Figures 12 (A) and (B), the heating of the lower side 7c of the pot 7 will be strong, and the rice in the food S near the upper side 7a and lower side 7c and in the upper layer will tend to become excessively gelatinized. This is because, while the area of ​​the rice and water in contact with the bottom 7b of the cooked food S is approximately the same for a large amount of cooked rice and a medium or smaller amount of cooked rice, the area of ​​the rice and water in contact with the upper side 7a and lower side 7c is smaller for a medium or smaller amount of cooked rice compared to a large amount of cooked rice. As a result, if the amount of cooked food S heated by the first IH heater 25' is considered to be the heated volume, this heated volume decreases.

[0077] Figures 13(A) and (B) show the transfer of heat within pot 7 when cooking a medium amount of food S at the rated maximum cooking capacity by maintaining a heating balance to the lower side 7c and bottom 7b of pot 7 and reducing the heating amounts of the first IH heater 25' and the second IH heater 26' when the food S is a large amount of rice at the rated maximum cooking capacity.

[0078] For example, if the heating amount of the bottom heating body 11' is 1400W when the food S is a large amount of rice at the rated maximum cooking amount, and the first IH heater 25' heating the lower side 7c of the pot 7 is 45%, and the second IH heater 26' heating the bottom 7b and further the lowest part 7d of the pot 7 is 55%, the heating balance is maintained at 45% for the first IH heater 25' and 55% for the second IH heater 26' even when the heating amount of the bottom heating body 11' is reduced to 1000W and the heating amount is set to a suitable amount when the food S is a medium amount of rice, and does not change. However, as shown in Fig. 13(A), the water level of the food S is lower than when the food S is a large amount of rice, so the area of ​​rice and water in contact with the upper side 7a and lower side 7c is smaller when the amount of rice is a medium amount compared to when the amount of rice is a large amount. As a result, the amount of heat received by the rice and water in contact with the upper side surface 7a and lower side surface 7c due to the heating by the first IH heater 25' becomes relatively large, and just as in Figure 10(A), the temperature of the part of the food item S near the side surface of the pot 7 becomes higher than the surrounding area, and because a strong external heat convection C1 is generated within the pot 7, the temperature of the upper part of the food item S becomes higher than the surrounding area, resulting in excessive gelatinization of the rice in the parts of the food item S near the upper side surface 7a and lower side surface 7c and in the upper part.

[0079] In addition, when the heating amount of the bottom heater 11' is set to an amount appropriate for when the food S is a small amount of rice, as shown in Fig. 13(B), the water level of the food S is lower than when the food S is a large amount of rice, and the water level is even lower than when the food S is a medium amount of rice as shown in Fig. 11(A), so the area of ​​rice and water in contact with the upper side 7a and lower side 7c as described above in Fig. 13(A) is even lower than when the food S is a medium amount of rice, and therefore the gelatinization of the rice in the vicinity of the upper side 7a and lower side 7c of the food S becomes even more excessive. In addition, when the water level is lower than a predetermined height, the heating of the first IH heater 25' no longer contributes to the generation of external convection C1, so even if external convection C1 occurs, it is weak, and the effect of the external convection C1 in raising the temperature of the upper part of the food S is reduced.

[0080] On the other hand, the water level of the food S decreases, and the amount of rice also decreases, so the rice layer becomes thinner, and as a result, the thermal resistance from the bottom 7b to the upward direction decreases. In other words, the rice of the food S absorbs water and heat, but the amount of absorption is reduced, so that, as shown in FIG. 13(B), the internal convection C2 of heat generated by heating the bottom 7b of the pot 7 with the second IH heater 26' tends to flow mainly upward, and the upward blowing becomes active, and the internal convection C2 of heat does not flow to the lower and middle layers of the center of the food S in the pot 7. Therefore, the temperature of the lower and middle layers of the center of the food S rises more slowly than the surrounding areas, and the gelatinization of the rice tends to be insufficient. In addition, when the food S is cooked, holes through which pressure from the bottom of the pot 7 has passed, that is, holes through which hot water has blown up, so-called crab holes, are easily formed.

[0081] Therefore, in the bottom heating element 11 of this embodiment, the heating balance of the first to third IH heaters 25-27 can be adjusted to be optimal depending on the amount of rice to be cooked at the rated maximum cooking amount, and the heating balance and heating amount of the first to third IH heaters 25-27 are independently adjusted to suit the amount of rice to be cooked, not only when the amount of rice to be cooked at the rated maximum cooking amount is medium or more, but also from the minimum to the maximum amount, making it possible to cook rice without uneven cooking, especially when the amount of rice to be cooked is less than a medium amount.

[0082] Fig. 14 is a diagram showing the change in heating balance of the first to third IH heaters 25-27 of this embodiment when a large amount of rice is cooked at the rated maximum cooking amount, and Fig. 15 shows the transfer of heat within the pot 7 when heated by the first to third IH heaters 25-27. The first IH heater 25 heats the lower part 7c of the side of the pot 7, thereby generating an external convection C1 of heat within the pot 7, the second IH heater 26 heats the lowest part 7d, which is the outer bottom part 7b, thereby generating an internal convection C2 of heat within the pot 7, and the third IH heater 27 heats the inner bottom part 7b, thereby generating an internal convection C3 of heat within the pot 7.

[0083] In this embodiment, when a large amount of rice is to be cooked, the heating balance of the first to third IH heaters 25-27 is such that the first IH heater 25 mainly heats the lower side portion 7c by adjusting the heating amount, for example, from a minimum of 0W to a maximum of 450W, the second IH heater 26 heats the lowest portion 7d of the bottom portion 7b, and the third IH heater 27 heats the bottom portion 7b from the lowest portion 7d to the inner center portion 7e simultaneously or alternately, and the first to third IH heaters 25-27 are configured to be able to heat in combination.

[0084] 14 and 15, when the amount of cooked rice is large, first, heating is performed by the first to third IH heaters 25-27 as shown in (i), generating external convection C1 of heat and internal convection C2 of heat. Next, heating is performed by the first and second IH heaters 25, 26 as shown in (ii), generating external convection C1 of heat and internal convection C2 of heat, and then heating is performed by the first and third IH heaters 25, 27 as shown in (iii), generating external convection C1 of heat and internal convection C3 of heat. Next, the heating balance of (i) is performed, and thereafter, the heating balance of (i) to (iii) is repeated. Therefore, in the food S to be cooked in the pot 7, external convection C1 of heat is continuously generated, and internal convection C2 and C3 of heat are generated simultaneously or alternately.

[0085] Fig. 16 is a diagram showing the heating balance of the first to third IH heaters 25-27 of this embodiment when the amount of cooked rice is medium at the rated maximum cooking amount, and Fig. 17 shows the transfer of heat in the pot 7 when heated by the first to third IH heaters 25-27. The heating balance of the first to third IH heaters 25-27 when the amount of cooked rice is medium is such that the second IH heater 26 mainly heats the lowest part 7d of the bottom part 7b by adjusting the heating amount, for example, from a minimum of 0W to a maximum of 550W, the first IH heater 25 heats the lower part 7c of the side surface, and the third IH heater 27 heats the bottom part 7b from the lowest part 7d to the inner center part 7e alternately, so that the first to third IH heaters 25-27 can be combined for heating.

[0086] As described above in the conventional example, heat from pot 7 is transferred via the fluorine coating on the inside of the pot, and the water in the food S that is in contact with the fluorine coating on the inside of the pot and the water in the upper part of the food S become hot, but the distance from these hot parts to the cold parts corresponding to the middle and lower parts of the food S is shorter than when a large amount of rice is cooked. Therefore, the heating balance is such that, compared to when a large amount of rice is cooked, the heating amount of first IH heater 25, for example, from a minimum of 0 W to a maximum of 450 W, is reduced, the heating of the lower part of the outer surface of pot 7 is weakened to weaken external convection C1, and the heating amount of third IH heater 27, for example, from a minimum of 0 W to a maximum of 400 W, is also reduced to weaken the heating of the outer bottom surface of pot 7 from the lowest part 7d to the inner center part 7e, weakening internal convection C3 and reducing the strength of the upward blowing. At this time, in order to reduce the amount of heating of the first IH heater 25 and the third IH heater 27, the power input to the first IH heater 25 and the third IH heater 27 may be reduced, or the intermittent conduction rate of the first IH heater 25 and the third IH heater 27 may be changed by changing the period or on-time ratio of the pulse drive signals of the IH drive circuits 32-2, 34-2 that are sent to the gates of the respective switch elements of the inverters 32-1, 34-1 of the first IH heater 25 and the third IH heater 27.

[0087] In addition, by alternately heating the lower side portion 7c by the first IH heater 25 and heating the bottom portion 7b from the lowest portion 7d to the inner center portion 7e by the third IH heater 27, external convection C1 of heat and internal convection C3 of heat are generated alternately, which promotes stirring of the water for the food S to be cooked in the pot 7 and reduces uneven heating.

[0088] 16 and 17, when the amount of cooked rice is medium, first, heating is performed by the first and second IH heaters 25 and 26 as shown in (iv), generating external convection C1 and internal convection C2 of heat, and then, heating is performed by the second and third IH heaters 26 and 27 as shown in (v), generating internal convection C2 and C3 of heat. Then, the heating balance of (iv) is performed, and then the heating balance of (v) is performed, and thereafter, the heating balance of (iv) and (v) is repeated. Therefore, in the food S to be cooked in the pot 7, internal convection C2 of heat is continuously generated, and external convection C1 of heat and internal convection C3 of heat are generated alternately repeatedly.

[0089] FIG. 18 is a diagram showing the heating balance of the first to third IH heaters 25-27 of this embodiment when the amount of cooked rice is small at the rated maximum amount of cooked rice, and FIG. 19 shows the transfer of heat in the pot 7 when the first to third IH heaters 25-27 are heated. The heating balance of the first to third IH heaters 25-27 when the amount of cooked rice is small is such that the second IH heater 26 heats the lowest part 7d of the bottom part 7b, and the third IH heater 27 heats the bottom part 7b from the lowest part 7d to the inner center part 7e simultaneously or alternately, and the second and third IH heaters 26, 27 can be combined for heating. The heating by the first IH heater 25 is stopped. The heating by the first IH heater 25 may be reduced to a heating amount that contributes to heating when the amount of cooked rice is small, compared to when the amount of cooked rice is large or medium.

[0090] When the amount of cooked rice is small, the distance from the high temperature part corresponding to the water of the food S in contact with the fluorine coating on the inside of the pot 7 or the water in the upper part of the food S to be cooked to the low temperature part corresponding to the middle and lower parts of the food S is shorter than when the amount of cooked rice is medium, so the heating balance is such that the heating by the first IH heater 25 is stopped or reduced to eliminate the external convection C1. On the other hand, as described above, the heat of the bottom part 7d heated by the second IH heater 26 moves to the upper side 7a of the pot 7 via the base material, and then moves to the water of the food S in contact with the fluorine coating on the inside of the pot, and in places where there is no rice, the movement of water and heat becomes active due to convection, so the water in the upper part of the food S becomes hot. Therefore, when the amount of cooked rice is small, the second IH heater 26 generates a sufficiently strong external convection C2 of heat. When the heating by the first IH heater 25 is reduced to weaken the external convection C1, the external convection C1 also occurs in addition to the external convection C2 of heat.

[0091] On the other hand, the amount of heat from the second IH heater 26 is reduced to match the amount of rice cooked, which reduces the amount of heat from the bottom 7d to the inner center 7e of the bottom 7b. Therefore, the third IH heater 27 is used in combination with the heating of the bottom 7b to achieve a heating balance that matches the amount of rice cooked.

[0092] In addition, by alternately heating the lowest part 7d of the pot 7 with the second IH heater 26 and heating the bottom 7b from the lowest part 7d to the inner center 7e with the third IH heater 27, external convection C2 of heat and internal convection C3 of heat are generated alternately, which promotes stirring of the water for the food S to be cooked in the pot 7 and reduces uneven heating.

[0093] 18 and 19, when the amount of cooked rice is small, first, heating is performed by the second and third IH heaters 26 and 27 as shown in (vi), generating external convection C2 of heat and internal convection C3 of heat. Next, heating is performed by the second IH heater 26 as shown in (vii), generating external convection C2 of heat, and then heating is performed by the third IH heater 27 as shown in (viii), generating internal convection C3 of heat. Next, the heating balance of (vi) is performed, and thereafter, the heating balance of (vi) to (viii) is repeated. Therefore, external convection C2 of heat and internal convection C3 of heat are generated simultaneously or alternately in the food S in the pot 7.

[0094] As described above, the main body 1 of the rice cooker of this embodiment comprises a bottomed, cylindrical pot 7 for containing rice and water as the food to be cooked, and a bottom heater 11 as a heating means for heating the pot 7, the pot 7 having a substantially cylindrical upper side portion 7a, a substantially disk-shaped bottom portion 7b, and a lower side portion 7c extending from the outer periphery of the bottom portion 7b and connecting to the upper side portion 7a, the bottom portion 7b having a lowermost portion 7d on its outer periphery that abuts against a flat surface when the pot 7 is placed on the flat surface, and being formed so as to become higher toward the center of the bottom portion 7b, The lower side 7c is slanted from the upper side 7a toward the lowest part 7d, and the bottom heating body 11 has a first IH heater 25 arranged to face the lower side 7c, a second IH heater 26 arranged to face the lowest part 7d, and a third IH heater 27 arranged to face the bottom 7b, and is configured so that the heating amount of the first IH heater 25, the heating amount of the second IH heater 26, and the heating amount of the third IH heater 27 can each be adjusted independently.

[0095] Therefore, the stability of the pot 7 when it is placed on a stand or the like is ensured, and the risk of deformation of the bottom 7b of the pot 7 due to thermal expansion when the temperature of the pot 7 rises during the rice cooking process, the warming process, etc. can be prevented. In addition, the external convection C1 generated by the heating of the first IH heater 25 can be promoted, and the blowing up effect from the bottom 7b of the internal convection C2 and C3 generated by the heating of the second IH heater 26 and the third IH heater 27 can be promoted. Furthermore, the heating balance and heating amount of the first to third IH heaters 25 to 27 are independently adjusted so as to be suitable for the amount of rice cooked, depending on the amount of rice cooked at the rated maximum cooking amount, that is, large, medium, or small, so that rice can be cooked evenly regardless of the amount of rice cooked S, and especially rice can be cooked evenly with an amount of rice cooked of less than a medium amount.

[0096] In addition, the main body 1 of the rice cooker of this embodiment is further equipped with a rice cooking control means 41 which changes the amount of heat of the bottom heating body 11 based on a first pattern as each cooking step progresses, to cook the food S, and a heat amount fluctuation means 44 as a heat amount varying means which changes the amount of heat of the bottom heating body 11 over time in a second pattern different from the first pattern when the rice cooking control means 41 is controlling the operation of the bottom heating body 11 to heat the pot 7, making it possible to cook the food S in the pot 7 with heating that is closer to the type of cooking in a stove where the flames flicker from a wood fire.

[0097] 20 and 21 show a modification of this embodiment. In this modification, a first IH heater 25 and a second IH heater 26 are connected in series to simplify the circuit configuration of the bottom surface heater 11.

[0098] Fig. 20 is a diagram showing the change in heating balance of the first to third IH heaters 25-27 of this modified example when the amount of cooked rice is large or medium, and Fig. 21 is a diagram showing the change in heating balance of the first to third IH heaters 25-27 of this modified example when the amount of cooked rice is small. In this modified example, the first IH heater 25 and the second IH heater 26 are connected in series, so the first IH heating drive unit 32 and the second IH heating drive unit 33 are combined into one IH heating drive unit, and the bottom surface heater 11 is driven by only two units, this IH heating drive unit and the third IH heating drive unit 34, so the circuit configuration of the bottom surface heater 11 is simplified. In addition, by changing the intermittent current conduction rate of the first and second IH heaters 25, 26 and the third IH heater 27, which are connected in series, depending on the amount of rice to be cooked, a more finely balanced heating system than before can be achieved, allowing rice to be cooked evenly.

[0099] In this modified example, when a large amount of rice is to be cooked, the heating balance of the first to third IH heaters 25-27 is achieved by heating the lower side portion 7c and the entire bottom portion 7b by the first to third IH heaters 25-27, and in particular by increasing the amount of heating of the bottom portion 7b from the lowest portion 7d to the inner center portion 7e by the third IH heater, thereby generating internal convection C3 of heat and promoting the upward flow of heat from the bottom portion 7b inside the pot 7, and by supplying hot water to the lower and middle layers of the center of the food S to be cooked in the pot 7, uneven cooking of the food S is reduced. Furthermore, when a medium amount of rice is being cooked, the heating balance of the first to third IH heaters 25-27 is such that the lower side portion 7c and the lowest portion 7d of the bottom portion 7b are heated continuously mainly by the first and second IH heaters 25, 26, and heating by the third IH heater 27 is weakened to reduce the amount of heat applied to the bottom portion 7b from the lowest portion 7d to the inner center portion 7e. This prevents overheating of this portion of the bottom portion 7b, thereby reducing uneven cooking of the food S being cooked.

[0100] To explain this in detail with reference to Fig. 20, when the amount of cooked rice is large or medium, first, as shown in (i), heating is performed by the first to third IH heaters 25-27, generating external convection C1 of heat and internal convection C2, C3 of heat. Next, as shown in (ii), heating is performed by the first and second IH heaters 25, 26, generating external convection C1 of heat and internal convection C2 of heat, after which the heating balance of (i) is performed, and thereafter, the heating balance of (i) to (ii) is repeated. Therefore, in the food S to be cooked in the pot 7, external convection C1 of heat and internal convection C2 of heat are generated continuously, and internal convection C3 of heat is generated intermittently, repeatedly.

[0101] Here, in this modified example, the heating time by the third IH heater 27 is changed according to the amount of cooked rice. For example, when the amount of cooked rice is 2.0 gou, which is a medium amount, the third IH heater 27 is controlled to repeat heating for 100 ms (0.1 seconds) with the heating balance of (i) and not heating for 800 ms (0.8 seconds) with the heating balance of (ii). Also, for example, when the amount of cooked rice is 5.5 gou, which is a large amount, the third IH heater 27 is controlled to repeat heating for 800 ms (0.8 seconds) with the heating balance of (i) and not heating for 100 ms (0.1 seconds) with the heating balance of (ii). That is, in this modified example, the heating time by the third IH heater 27 is increased as the amount of cooked rice increases, and the amount of heating of the bottom 7b from the lowest part 7d to the inner center 7e is increased. At this time, by changing the period of the pulse drive signal and the ratio of the on-time to one period (on-time ratio), the total amount of heat from the first to third IH heaters 25-27 to the pot 7 can be increased or decreased, for example, from a maximum of 1400W to 700W depending on the amount of rice to be cooked.

[0102] In addition, in this modified example, when the amount of cooked rice is small, the heating balance of the first to third IH heaters 25-27 is achieved by alternating between heating the lower part 7c of the side and the lowest part 7d of the bottom 7b by the first and second IH heaters 25, 26 connected in series, and heating the bottom 7b from the lowest part 7d to the inner center 7e by the third IH heater 27. This causes external convection C1 of heat, internal convection C2 of heat, and internal convection C3 of heat to occur alternately, promoting the stirring of the water in the food S to be cooked in the pot 7, thereby suppressing overheating, especially in the part of the food S near the lower part 7c of the side, and reducing uneven heating.

[0103] To explain this in detail with reference to Fig. 21, when the amount of cooked rice is small, first, heating is performed by the third IH heater 27 as shown in (iii) to generate internal convection of heat C3. Next, heating is performed by the first and second IH heaters 25, 26 as shown in (iv) to generate external convection of heat C1 and internal convection of heat C2, after which the heating balance of (i) is performed, and thereafter, the heating balance of (iii) to (iv) is repeated.

[0104] In addition, the heating balance time of (iii) and the heating balance time of (iv) in the first to third IH heaters 25-27 are changed according to the amount of cooked rice. For example, when the amount of cooked rice is small, such as 0.5 gou, heating is performed for 300 ms (0.3 seconds) with the heating balance of (iii) and 100 ms (0.1 seconds) with the heating balance of (iv) is repeated. For example, when the amount of cooked rice is large, such as 1.5 gou, heating is performed for 100 ms (0.1 seconds) with the heating balance of (iii) and 300 ms (0.3 seconds) with the heating balance of (iv) is repeated. In other words, in this modified example, the more the amount of cooked rice is, the longer the heating time by the first and second IH heaters 25, 26 is, while the heating time by the third IH heater 27 is, reduced, so that overheating of the part near the lower side 7c of the cooked rice object S is suppressed, thereby reducing uneven heating.

[0105] As described above, in the main body 1 of the rice cooker of this modified example, the bottom heating body 11 has a first IH heater 25 arranged to face the lower part 7c of the side surface, a second IH heater 26 arranged to face the lowest part 7d, and a third IH heater 27 arranged to face the bottom part 7b, and is configured so that the heating amounts of the first IH heater 25 and the second IH heater 26 and the heating amount of the third IH heater 27 can be adjusted independently.

[0106] Therefore, compared to the first embodiment, the circuit configuration of the bottom heating element 11 can be simplified while achieving a more finely balanced heating. When a large amount of rice is to be cooked, the amount of heat generated by the third IH heater from the lowest part 7d to the inner center 7e is increased, thereby generating internal convection C3 of heat and promoting the upward movement of heat from the bottom 7b inside the pot 7. When a medium amount of rice is to be cooked, the heating by the third IH heater 27 is weakened and the amount of heat generated by the bottom 7b from the lowest part 7d to the inner center 7e is reduced, thereby preventing overheating of this bottom 7b portion and reducing uneven cooking of the food S being cooked. When the amount of rice to be cooked is small, the first and second IH heaters 25, 26 alternately heat the lower part 7c of the side and the lowest part 7d of the bottom 7b, and the third IH heater 27 heats the bottom 7b from the lowest part 7d to the inner center 7e, thereby preventing overheating of the part of the food S near the lower part 7c of the side and reducing uneven heating.

[0107] Fig. 22 shows a further modified example of this embodiment. In this modified example, the user can select a cooking method according to the amount of rice to be cooked from the beginning of the rice cooking process.

[0108] Fig. 22 is a top view of the display operation unit 5 of this modified example. To explain in detail with reference to the figure, a display element 67-13 for "small appropriate amount", a display element 67-14 for "medium amount", a display element 67-15 for "large amount", and a display element 67-16 for "automatic" are arranged side by side on the bottom row of the LCD 63. The rest of the configuration is the same as that of the first embodiment, so the description will be omitted.

[0109] Next, the operation of the rice cooker main body 1 having the above configuration will be described. When, for example, the rice cooking amount key 57 on the operation unit 4 is operated, the screen moves to a selection screen for the amount of rice cooked. Here, each time the forward key 52, the back key 53, or the touch sensor 60 is operated, the operation signal is received by the display control means 43, which controls the LCD 63 to light or turn off the display element 67-13 for "small appropriate amount", the display element 67-14 for "medium amount", the display element 67-15 for "large amount", and the display element 67-16 for "automatic", and the setting of the rice cooking course is changed so that the amount of rice cooked that is lit is selected.

[0110] Here, when the "small / appropriate amount" display element 67-13 is selected, the rice cooking control means controls the first to third IH heating drive units 32-34 so that the rice cooking process is performed with the heating balance of the first to third IH heaters 25-27 when a small amount of rice is being cooked, and similarly, when the "medium amount" display element 67-13 or the "large amount" display element 67-15 is selected, the rice cooking control means controls the first to third IH heating drive units 32-34 so that the rice cooking process is performed with the heating balance of the first to third IH heaters 25-27 when a medium or large amount of rice is being cooked. When the "automatic" display element 67-16 is selected, the rice cooking control means controls the first to third IH heating drive units 32-34 to perform the rice cooking process with a heating balance according to the amount of rice cooked detected by calculating the amount of rice cooked for the food S in the pot 7 based on the temperature rise rate of the pot temperature t1 and the temperature rise rate of the lid temperature t2 during the soaking cooking process and the boiling heating process. With this configuration, the user can directly select the heating balance of the first to third IH heaters 25-27, and by specifically selecting the heating balance according to the amount of rice cooked, rice can be cooked with a heating balance according to the amount of rice cooked from the beginning of the rice cooking process.

[0111] Fig. 23 shows another modified example of this embodiment. In this modified example, in addition to the rice menu, the brand and quality of rice can also be set, and rice can be cooked evenly regardless of the amount of rice to be cooked when cooking various types of food S.

[0112] Fig. 23 is a top view of the display operation unit 5 of this modified example. To explain in detail with reference to the figure, the operation section 4 is composed of only a touch sensor 60, and a display element 67-18 for "cooking rice" instead of the cooking key 58 of the first embodiment, a display element 67-19 for "keep warm" instead of the keep warm key 59, and a display element 67-20 for "off" instead of the off key 56 are arranged side by side in the lower part of the display operation unit 5, i.e., in the lower part of the LCD 63. By touching the touch sensor 60 above these display elements 67-18 to 67-20, the cooking control means 41 or the keep warm control means 42 is configured to act in the same way as the cooking rice key 58, the keep warm key 59, or the off key 56.

[0113] The "forward" display element 67-21 and "back" display element 67-22 for adjusting the time are operated to adjust the reservation time or the current time. For example, when the touch sensor 60 above the clock display element 67-1 or the cooking reservation display elements 67-2 and 67-3 is touched, the display control means 43 receives an operation signal from the touch sensor 60 and transitions to a screen for adjusting the current time or a screen for selecting the reservation time, and the "forward" display element 67-21 and "back" display element 67-22 for adjusting the time are used to adjust the current time or select the reservation time. Here, the display control means 43 of this modified example sets the reservation time, which acts as a timer, according to the cooking course taking into account the settings for various types of cooking and the amount of cooked rice before the start of the cooking process. Therefore, the cooking start time relative to the set specified time is changed according to the heating pattern for the selected type of cooking, improving the accuracy of the cooking time according to the amount of cooked rice for each type of cooking, and reducing the risk, for example, of the steaming process being excessively long or the food S being cooked earlier than its intended time.

[0114] The display element 67-23 of "forward" for adjusting the amount of cooked rice and the display element 67-24 of "back" are operated when setting them on the selection screen of the amount of cooked rice, and for example, when the touch sensor 60 above the display element 67-23 of "forward" for adjusting the amount of cooked rice and the display element 67-24 of "back" is touched, the display control means 43 accepts the operation signal from the touch sensor 60 and moves to the selection screen of the amount of cooked rice, where it is possible to set in 0.5 gou increments from "0.5 gou" to "5.5 gou", or to set it to "automatic". The selection of the amount of cooked rice can also be set by touching the touch sensor 60 above the display elements 67-25, 67-26, and 67-27 of the amount of cooked rice, which are stored and registered in the storage means 37 by the user in advance.

[0115] The "forward" display element 67-28 and the "back" display element 67-29 for texture selection are operated when setting these on the texture selection screen, and for example, when the touch sensor 60 above the "forward" display element 67-28 or the "back" display element 67-29 for texture selection is touched, the display control means 43 receives an operation signal from the touch sensor 60 and transitions to the texture selection screen. Texture selection can also be set by, for example, touching the touch sensor 60 above the texture display elements 67-30, 67-31, 67-32 that have been stored and registered in advance in the storage means 37 by the user.

[0116] The display element 67-33 for "forward" and the display element 67-34 for "back" for menu selection are operated when setting them on the menu selection screen, and for example, when the touch sensor 60 above the display element 67-33 for "forward" and the display element 67-34 for "back" for menu selection is touched, the display control means 43 receives an operation signal from the touch sensor 60 and transitions to the menu selection screen. In addition, the menu selection can also be set by, for example, touching the touch sensor 60 above the menu display elements 67-35, 67-36, and 67-37 that are stored and registered in the storage means 37 by the user in advance.

[0117] In this modification, instead of the menu of rice, the brand of rice or the quality of rice can be set. When the brand of rice is set, the display element 67-38 of "forward" for selecting the brand of rice or the display element 67-39 of "back" are operated on the menu selection screen. For example, when the touch sensor 60 above the display element 67-38 of "forward" for selecting the brand of rice or the display element 67-39 of "back" for selecting the brand of rice is touched, the display control means 43 receives an operation signal from the touch sensor 60 and transitions to a selection screen for the origin and brand of rice, for example, as shown in FIG. 24. The selection of the brand of rice can also be set by touching the touch sensor 60 above the display elements 67-41, 67-42, 67-43 of the brand of rice that are stored and registered in the storage means 37 by the user in advance.

[0118] The storage means 37 of this modified example stores texture data of hardness and stickiness for each rice origin and brand, as shown in Fig. 24, for example, and the rice cooking control means 41 selects a heating pattern for the rice cooking process based on this texture data to cook the rice while taking advantage of the characteristics of the brand. Referring to Fig. 24, the selection of the rice origin and brand will be described. When the selection screen for the rice origin and brand is displayed, the display control means 43 controls the LCD 63 to display the display element for the rice origin as shown in Fig. 24(A). Here, when the display element for the rice origin is selected by operating the "Next" display element 67-38 or the "Back" display element 67-39 for selecting the rice brand, or the touch sensor 60, the display control means 43 controls the LCD 63 to display the display element for the rice brand arranged under the display element for the selected rice origin as shown in Fig. 24(B). For example, when "Tokushima" is selected on the selection screen for the display element of the rice origin, the display control means 43 controls the LCD 63 to display each of the display elements "Koshihikari", "Hinohikari", "Akitakomachi", "Kinuhikari", "Nikomaru", and "Oidemai". When the display element of the rice brand is selected by operating the "Next" display element 67-38 or the "Back" display element 67-39 for selecting the rice brand, or the touch sensor 60, the display control means 43 controls the LCD 63 to display a selection screen for registering the rice brand display element 67-41, 67-42, or 67-43. After the user makes a selection, the display control means 43 controls the LCD 63 to change the display of the display elements 67-41, 67-42, or 67-43 for the selected rice brand to the selected rice origin and brand, and stores the selected rice origin and brand in the storage means 37.

[0119] Also, referring to FIG. 25, the texture data of hardness and stickiness stored in the memory means 37 will be explained. For example, "Koshihikari Minamiuonuma" has a good balance of hardness and stickiness with a hardness of "3" and stickiness of "3", "Akitakomachi" has a hardness of "1" and stickiness of "2", which is a good balance of hardness and stickiness (chewing ability), and "Milky Queen" has a hardness of "5" and stickiness of "5", which results in a chewy and sticky rice when cooked.

[0120] In this modified example, the heating pattern for the rice cooking process is selected based on "Minamiuonuma Koshihikari," which has a good balance of hardness and stickiness. For example, if "Akitakomachi" becomes too firm and sticky, it will become too hard and lose its flavor. Therefore, the rice cooking control means 41 of this modified example boils the water for the food S in the pot 7 early, lengthening the boiling time, and controls the power on / off of the bottom heater 11 and the side heater 12 so that the amount of heat after boiling is less than that of "Minamiuonuma Koshihikari." Specifically, the rice cooking control means 41 controls the bottom heating element 11 to achieve a maximum heating amount of 1400 W, which is the sum of the external convection current C1 generated by the heating of the first IH heater 25 and the internal convection currents C2 and C3 generated by the heating of the second IH heater 26 and the third IH heater 27, and boils the water in the food S in the pot 7 early. After boiling, the rice cooking control means 41 controls the bottom heating element 11 to reduce the heating amount to 700 W with a heating balance in which the heating rate of the second IH heater 26 and the third IH heater 27 is reduced compared to the heating rate of the first IH heater 25. The bottom heating element 11 is further controlled so that the on / off rate is about 60%, so that the boiling duration is extended. This increases the degree of gelatinization of the rice in the food S to promote stickiness, and cooks the rice so that it tends to be softer by increasing the moisture content slightly.

[0121] For example, when the soft stickiness of "Milky Queen" becomes excessive, it becomes hard and sticky without a chewy texture, and the taste deteriorates. Therefore, the rice cooking control means 41 of this modified example controls the bottom heating element 11 so that the heating amount is 1400 W with a heating balance that suppresses the heating of the first IH heater 25 to suppress the generation of external convection C1, while strengthening the heating of the second IH heater 26 and the third IH heater 27 to promote the blowing up of internal convection C2 and C3, more than that of "Koshihikari Minamiuonuma". After boiling, the rice cooking control means 41 controls the heating balance of the first IH heater 25, the second IH heater 26 and the third IH heater 27 to suppress the generation of external convection C1, and promotes the blowing up of internal convection C2 and C3, more than that of "Koshihikari Minamiuonuma". As in the case of "Minamiuonuma," the bottom heating element 11 is controlled to reduce the amount of heat to 1000 W with the heating balance returned to the original level, and the bottom heating element 11 is further controlled so that the on / off rate is about 80%, thereby shortening the boiling duration. The rice is cooked with strong heating to continue boiling so that the boiling time is not excessively long and the rice of the cooked food S does not become excessively gelatinized.

[0122] When setting the rice quality, the display element 67-44 of "Next" or the display element 67-45 of "Back" for selecting rice quality are operated on the menu selection screen. For example, when the touch sensor 60 above the display element 67-44 of "Next" or the display element 67-45 of "Back" for selecting rice quality is touched, the display control means 43 receives the operation signal from the touch sensor 60 and transitions to a selection screen for rice quality such as "white rice", "80% polished", "70% polished", "50% polished", "30% polished", "brown rice", "brown rice mixed rice", "germinated rice", "multiple grain rice", "wheat mixed rice", "low protein rice", "long grain rice", and "high amylose rice". The selection of rice quality can also be set by touching the touch sensor 60 above the display elements 67-46, 67-47, and 67-48 of rice quality that are stored and registered in the storage means 37 in advance by the user.

[0123] For example, if "brown rice" is selected, brown rice has a slow water absorption rate, so in the steaming heating process, the rice cooking control means 41 of this modified example performs the steaming heating process at a high water temperature for a long period of time, for example at a water temperature of about 60°C for about 30 minutes, whereas in the case of the polished rice described above, the water temperature is set to about 45°C for 15 minutes. Also, since brown rice is difficult to gelatinize, after the food to be cooked S has boiled, the rice cooking control means 41 controls the bottom heating element 11 to reduce the amount of heat to a level that can maintain boiling at a moderate level, and the rice is cooked to maintain the boiling time for a long period of time.

[0124] Here, brown rice absorbs less heat and water than polished rice, and the rice of the food S has less thermal resistance and less resistance to heat transfer than polished rice, so the heat from the surface of the pot 7 tends to move to the center of the pot 7, away from the surface. Therefore, the rice cooked with the food S has less uneven cooking compared to polished rice, and "crab holes" caused by the internal convection C2, C3 blowing up from the bottom of the pot 7 are more likely to form compared to polished rice. Therefore, while external convection C1 is not as necessary as when cooking polished rice, if the heating balance is the same as that of polished rice described above, the areas near the upper side 7a and lower side 7c of the food S may be overheated, causing the rice to gelatinize excessively, resulting in a cooked rice that is too moist and falls apart. Therefore, when "brown rice" is selected for cooking, the rice cooking control means 41 of this modified example controls the bottom heating element 11 after boiling so that the heating balance of the first IH heater 25 is less than the heating balance of the second IH heater 26 and the third IH heater 27, compared to the heating balance of polished rice, thereby reducing the heating balance of the lower part of the side of the pot compared to the bottom of the pot, and cooking is performed by preventing the parts of the food S near the upper part 7a of the side and the lower part 7c of the side from being overheated.

[0125] Also, for example, when "low protein white rice" is selected, if the rice absorbs too much water it will lose its texture, so the rice cooking control means 41 of this modified example hardly performs the soaking cooking process, but quickly performs the boiling heating process, and after boiling, moves to the steaming process in about 3 to 5 minutes, and controls the bottom heating body 11 to heat rapidly with a balanced heating by all of the first IH heater 25, the second IH heater 26 and the third IH heater 27 so that the unabsorbed water is absorbed by the rice or evaporated, thereby cooking the rice.

[0126] Fig. 26 shows a further modified example of this embodiment. In this modified example, the modified example shown in Fig. 23 is simplified to make it easier for the user to understand. To explain in detail with reference to the figure, the operation unit 4 is composed of only a touch sensor 60, as in the modified example described in Fig. 23, and instead of the display elements 67-21, 67-22 for time adjustment, the display elements 67-23, 67-24 for rice cooking amount adjustment, the display elements 67-28, 67-29 for texture adjustment, the display elements 67-33, 67-34 for menu selection, and the display elements 67-38, 67-39 for rice brand selection, the display element 67-51 for "forward" and the display element 67-52 for "back" are arranged in the lower part of the LCD 63.

[0127] When making settings, by touching the touch sensor 60 above the clock display element 67-1, the cooked rice reservation display elements 67-2, 67-3, the cooked rice amount display element 67-4, the texture display element 67-30, the rice brand display element 67-41, the rice quality display element 67-46, or the menu display element 67-35, the display control means 43 receives an operation signal from the touch sensor 60 and moves to a selection screen for each setting, where each setting can be selected by touching the selection display element 67-51 for "forward" and the display element 67-52 for "back" or the touch sensor 60. Other operations are the same as those in the above-mentioned embodiment and modified examples, and therefore will not be described.

[0128] As described above, the rice cooker of this modified example further includes the operation unit 4 as a selection means for selecting the heating pattern of the bottom heating body 11, and the rice cooking control means 41 as a control means for controlling the bottom heating body 11 based on the selected heating pattern, and the rice cooking control means 41 is configured to change the heating amount of the first IH heater 25, the heating amount of the second IH heater 26, and the heating amount of the third IH heater 27 based on the selected heating pattern. Therefore, the heating amounts of the first to third IH heaters 25 to 27 can be changed according to not only the "amount of rice cooked" but also the "menu," "texture," "origin and brand of rice," etc., and rice can be cooked with reduced unevenness. EXAMPLES

[0129] 27 to 32 show the second embodiment of the rice cooker of the present invention. In the rice cooker of this embodiment, a plurality of IH heaters are arranged in a plurality of blocks so as to be divided with respect to the bottom surface of the bottom part 7b of the pot 7, and every other block is connected in series, and these are made into the second IH heater 71 and the third IH heater 72 as IH heaters that can be heated independently, and the heating balance of the first to third IH heaters 25, 71, and 72 can be adjusted to be optimal according to the amount of rice cooked at the rated maximum cooking amount, and the heating balance and heating amount of the first to third IH heaters 25, 71, and 72 are independently adjusted so as to be suitable for the amount of rice cooked, not only when the amount of rice cooked at the rated maximum cooking amount is medium or more, but also from the minimum amount to the maximum amount, and the rice can be cooked evenly, especially when the amount of rice cooked is less than a medium amount.

[0130] Fig. 27 is a schematic diagram showing the main parts around the bottom heater 11. The first to third IH heaters 25, 71 and 72 are provided on the outer surface of the inner frame 9 as in the first embodiment, and the second and third IH heaters 71, 72 are arranged facing the bottom 7b as bottom heaters. As shown in Fig. 27, the second and third IH heaters 71, 72 are divided, for example, at 60° intervals with respect to the bottom surface of the bottom 7b of the pot 7 and arranged in a plurality of blocks, for example, six pieces, and half blocks, for example, three pieces, are connected in series every other block, and the heating balance and heating amount of the first to third IH heaters 25, 71 and 72 are independently adjusted so as to be suitable for the amount of rice cooked.

[0131] Fig. 28 is a diagram showing the heating balance of the first to third IH heaters 25, 71, and 72 of this embodiment when the amount of rice cooked at the rated maximum cooking amount is an intermediate amount or more, for example, 3.0 to 5.5 cups, and Fig. 29 shows the transfer of heat within the pot 7 when the first to third IH heaters 25, 71, and 72 are heated. The first IH heater 25 heats the lower side 7c of the pot 7, generating an external convection C1 of heat within the pot 7, and the second and third IH heaters 71, 72 heat the outer bottom 7b in rotation, generating internal convection C4, C5 of heat in a localized rotation over the bottom 7b, generating complex convection of heat within the pot 7.

[0132] 28 and 29, when the amount of cooked rice is medium or more, first, heating is performed by the first IH heater 25 as shown in (i), generating external convection C1 of heat. Next, heating is performed by the second and third IH heaters 71 and 72 as shown in (ii), generating internal convection C4, C5 of heat, and then the heating balance of (i) is performed. After that, the cycle of (i) to (ii) is repeated at a high speed, for example, 50 ms per cycle. Therefore, in the food S to be cooked in the pot 7, external convection C1 of heat and internal convection C4, C5 of heat are repeatedly generated alternately, and the external convection C1 of heat and the internal convection C4, C5 of heat are alternately generated. Note that the period of the pulse drive signal and the ratio of the on time to one period (on time ratio) at this time are not limited to those described above, and are arbitrarily set so that the food S is cooked evenly.

[0133] Furthermore, when a large amount of rice is to be cooked, heating is performed continuously using all of the first to third IH heaters 25, 71 and 72, which have a minimum of 0 W to a maximum of 1400 W, and heating is performed on the lower outer surface and the outer bottom surface of the pot 7, thereby continuously generating external convection C1 of heat and internal convection C4 and C5 of heat.

[0134] Figure 30 also shows the heating balance of the first to third IH heaters 25, 71 and 72 of this embodiment, and the transfer of heat within the pot 7 when heated by the first to third IH heaters 25, 71 and 72, when the amount of rice cooked at the rated maximum cooking amount is less than an intermediate amount, for example, 0.5 to 2.5 cups.

[0135] Specifically, when the amount of cooked rice is less than the medium amount, first, as shown in (iii), heating is performed by the first to third IH heaters 25, 71, and 72, generating external convection C1 and internal convection C4 of heat. Next, as shown in (iv), heating is performed by the first IH heater 25 and the second IH heater 71, generating external convection C1 and internal convection C4 of heat. Then, as shown in (v), heating is performed by the second IH heater 71 and the third IH heater 72, generating internal convection C4 and C5 of heat. Next, as shown in (vi), heating is performed by the first IH heater 25 and the third IH heater 72, generating external convection C1 and internal convection C5 of heat. After that, the heating balance of (iii) is performed, and the cycle of (iii) to (vi) is repeated at high speed, for example, one cycle of 100 ms. As a result, external convection C1 and internal convection C4, C5 of heat occur alternately and repeatedly in the food S inside the pot 7, resulting in complex thermal convection of external convection C1 and internal convection C4, C5 of heat that was not possible with the conventional technology.

[0136] FIG. 31 is a diagram showing the heating balance of the first to third IH heaters 25, 71, and 72 of this embodiment when the amount of cooked rice is small at the rated maximum amount of cooked rice, and FIG. 32 shows the transfer of heat in the pot 7 when the first to third IH heaters 25, 71, and 72 are heated. The heating balance of the first to third IH heaters 25, 71, and 72 when the amount of cooked rice is small is such that the bottom 7b is alternately heated by the second and third IH heaters 71, 72, and the second and third IH heaters 71, 72 can be combined for heating. The first IH heater 25 is configured to stop heating. The heating by the first IH heater 25 may be configured to be reduced to a heating amount that contributes to heating when the amount of cooked rice is small, compared to when the amount of cooked rice is large or medium or more as described above.

[0137] 31 and 32, when the amount of cooked rice is small, first, heating is performed by the third IH heater 72 as shown in (vii) to generate internal heat convection C5, and then heating is performed by the second IH heater 71 as shown in (viii) to generate internal heat convection C4. After that, the heating balance is performed as shown in (vii), and thereafter, the cycle of (vii) to (viii) is repeated at a high speed, for example, 50 ms per cycle. Therefore, the internal heat convection C4 and C5 are repeatedly generated alternately in the food S in the pot 7, and the food S is heated locally in a rotational manner over the bottom 7b of the pot 7, which activates the heat transfer from the upper part to the lower part of the food S, thereby reducing uneven cooking of the rice cooked by the food S.

[0138] As described above, the main body 1 of the rice cooker of this embodiment includes a bottomed, cylindrical pot 7 for containing rice and water as food to be cooked, and a bottom heater 11 as a heating means for heating the pot 7. The pot 7 has a substantially cylindrical upper side portion 7a, a substantially disk-shaped bottom portion 7b, and a lower side portion 7c extending from the outer periphery of the bottom portion 7b and connecting to the upper side portion 7a. The bottom portion 7b has a lowermost portion 7d on its outer periphery that comes into contact with a flat surface when the pot 7 is placed on the flat surface, and is formed so as to become higher toward the center of the bottom portion 7b. The lower side portion 7c is formed so as to have a lower lateral portion 7d that is in contact with the flat surface when the pot 7 is placed on the flat surface. The bottom surface heating body 11 has a shape that slopes from the upper surface 7a toward the lowermost surface 7d, and has a first IH heater 25 arranged to face the lower surface 7c of the side surface, and a second IH heater 71 and a third IH heater 72 arranged to face the bottom 7b and divided into multiple blocks relative to the bottom 7b, and is configured so that the heating amount of the first IH heater 25, the heating amount of the second IH heater 71, and the heating amount of the third IH heater 73 can each be adjusted independently.

[0139] Therefore, depending on the amount of rice to be cooked at the rated maximum cooking capacity, large, medium or small, the heating balance and amount of the first to third IH heaters 25-27 are independently adjusted to suit the amount of rice to be cooked, and in addition to heating the lower part 7c of the side surface of the pot 7, heating is also performed locally in a rotational manner across the bottom part 7b of the pot 7, which repeatedly alternates between external convection C1 and internal convection C4, C5 of heat, allowing complex heat convection of external convection C1 and internal convection C4, C5 that was not possible with the conventional method to occur, making it possible to cook rice that is evenly cooked regardless of the amount of rice being cooked. EXAMPLES

[0140] Figures 33 to 36 show a third embodiment of the rice cooker of the present invention. In the rice cooker of this embodiment, in addition to the first IH heater 25' and the second IH heater 26', which are the first layer IH heaters as shown in Figure 11, a third IH heater 81, which is the second layer IH heater, is provided so as to overlap the outside of the second IH heater 26', and the heating balance and heating amount of the first to third IH heaters 25', 26', and 81 are independently adjusted to suit the amount of rice to be cooked, depending on the amount of rice to be cooked (large, medium, or small) at the rated maximum rice cooking amount, so that rice can be cooked evenly.

[0141] 33(A) and (B) are schematic diagrams showing the main parts around the bottom heater 11. The first IH heater 25' and the second IH heater 26', which are the IH heaters of the first layer, are arranged facing the lower part of the outer side surface of the lower part of the side surface 7c and the bottom part 7b, respectively, while the third IH heater 81, which is the IH heater of the second layer, is arranged facing the bottom part 7b so as to overlap the outside of the second IH heater 26'. This differs from the conventional point in that the second IH heater 26' and the third IH heater 81 are provided in multiple stages. Therefore, the inner frame 9 is formed in a two-layer structure, and the first IH heater 25' and the second IH heater 26' are provided on the outer surface of the inner first layer, and the third IH heater 81 is provided on the outer surface of the outer second layer. The heating amount of the bottom heater 11 is 0 to 400 W for the first IH heater 25', 0 to 500 W for the second IH heater 26', and 0 to 500 W for the third IH heater 27, totaling 0 to 1400 W. In this embodiment, the third IH heater 81, which is the second-layer IH heater, is disposed so as to overlap the outside of the second IH heater 26', but may be disposed so as to overlap the outside of the first IH heater 25'. In addition, the first and second layers of the inner frame 9 may be connected on the outer periphery side of the first IH heater 25' as shown in FIG. 33(A), or may be connected between the first IH heater 25' and the second IH heater 26' as shown in FIG. 33(B).

[0142] Fig. 34 shows the transfer of heat within pot 7 when the first to third IH heaters 25', 26', and 81 are heated when a large amount of rice is to be cooked at the rated maximum cooking amount. By heating the lower part 7c of the side of pot 7 with first IH heater 25', an external convection C1 of heat is generated within pot 7, by heating the bottom part 7b with second IH heater 26', an internal convection C2 of heat is generated within pot 7, and by heating the bottom part 7b with third IH heater 81, an internal convection C6 of heat is generated within pot 7.

[0143] In this embodiment, when a large amount of rice is to be cooked, the heating balance of the first to third IH heaters 25', 26' and 81 is such that the third IH heater 81 mainly heats the bottom 7b by adjusting the heating amount, for example, from a minimum of 0W to a maximum of 500W, the first IH heater 25' heats the lower side 7c by adjusting the heating amount, for example, from a minimum of 0W to a maximum of 400W, and the second IH heater 26' heats the bottom 7b simultaneously or alternately by adjusting the heating amount, for example, from a minimum of 0W to a maximum of 500W, so that the first to third IH heaters 25', 26' and 81 can be used for heating in combination. As a result, in the food S inside the pot 7, internal heat convection C6 occurs continuously, and external heat convection C1 and internal heat convection C2 occur simultaneously or alternately repeatedly, strengthening the upward pressure rise from the bottom 7b inside the pot 7 and suppressing insufficient heating of the center of the food S inside the pot 7, enabling rice to be cooked evenly.

[0144] Fig. 35 shows the transfer of heat within pot 7 when the first to third IH heaters 25', 26' and 81 are heated when the amount of rice cooked is medium at the rated maximum cooking amount. When the amount of rice cooked is medium, heating is not performed by third IH heater 81, and external convection C1 of heat is generated within pot 7 by heating lower part 7c of the side of pot 7 with first IH heater 25', and internal convection C2 of heat is generated within pot 7 by heating bottom part 7b with second IH heater 26'.

[0145] In this embodiment, when the amount of cooked rice is medium, the heating balance of the first to third IH heaters 25', 26' and 81 is such that the first IH heater 25' adjusts the heating amount, for example, from a minimum of 0 W to a maximum of 400 W, to heat the lower part of the side 7c, and the second IH heater 26' adjusts the heating amount, for example, from a minimum of 0 W to a maximum of 500 W, to heat the bottom 7b alternately.By configuring the first and second IH heaters 25', 26' to be able to heat in combination, uneven cooking of the rice when the food S is cooked can be reduced.

[0146] Fig. 35 shows the transfer of heat in the pot 7 when the first to third IH heaters 25', 26' and 81 are heated when the amount of rice cooked is small at the rated maximum cooking amount. When the amount of rice cooked is small, heating is not performed by the first IH heater 25' or the second IH heater 26', and the bottom 7b of the pot 7 is heated by the third IH heater 81, generating internal convection C6 of heat in the pot 7. As described above in the first embodiment, the heat of the bottom 7b heated by the third IH heater 81 transfers to the upper side 7a of the pot 7 via the base material, and then transfers to the water of the food S that is in contact with the fluorine coating on the inner surface of the pot, via the fluorine coating on the inner surface of the pot. In places where rice is not present, the transfer of water and heat becomes active due to convection, and the water in the upper part of the food S becomes hot. Therefore, when the amount of cooked rice is small, the third IH heater 81 generates a sufficiently strong external heat convection C6, which prevents the rice in the vicinity of the upper side surface 7a and the lower side surface 7c, i.e., the rice on the surface of the pot, from becoming excessively gelatinized and becoming overhydrated. Also, since the first IH heater 25' does not heat the lower side surface 7c, which is done when the amount of cooked rice is large or medium, the heating loss can be reduced and the heating efficiency in the rice cooking process can be improved.

[0147] As described above, the main body 1 of the rice cooker of this embodiment includes a bottomed, cylindrical pot for containing rice and water as food to be cooked, and a bottom heater 11 as a heating means for heating the pot 7. The pot 7 has a substantially cylindrical upper side portion 7a, a substantially disk-shaped bottom portion 7b, and a lower side portion 7c extending from the outer periphery of the bottom portion 7b and connecting to the upper side portion 7a. The bottom portion 7b has a lowermost portion 7d on its outer periphery that comes into contact with a flat surface when the pot 7 is placed on the flat surface, and is formed so as to become higher toward the center of the bottom portion 7b. The lower side portion 7c is located closer to the upper side portion 7a than the upper side portion 7a. The bottom heating body 11 has a shape that is inclined from the top to the bottom 7d, and has a first IH heater 25' arranged to face the lower part 7c of the side surface, a second IH heater 26' arranged to face the bottom 7b, and a third IH heater 81 arranged to overlap the first IH heater 25' or the second IH heater 26', and is configured so that the heating amount of the first IH heater 25', the heating amount of the second IH heater 26', and the heating amount of the third IH heater 81 can each be adjusted independently.

[0148] Therefore, when the amount of cooked rice at the rated maximum cooking amount is small, the third IH heater 81 generates a sufficiently strong internal heat convection C6 and external heat convection C6, so that the rice in the vicinity of the upper side 7a and the lower side 7c, i.e., the rice on the surface of the pot, becomes excessively gelatinized and the risk of excessive moisture can be suppressed. In addition, since the first IH heater 25' does not need to heat the lower side 7c, the heating efficiency in the rice cooking process can be improved. When the amount of cooked rice is large, the blowing up, which is the pressure rise from the bottom 7b in the pot 7, can be strengthened, and the insufficient heating of the center of the food S in the pot 7 can be suppressed, and rice can be cooked without uneven cooking. Furthermore, when the amount of cooked rice is medium or large, the external heat convection C1 and the internal heat convection C2 can be generated alternately to suppress uneven cooking. Therefore, depending on whether the amount of rice to be cooked is large, medium or small, the heating balance and amount of the first to third IH heaters 25', 26' and 81 are each independently adjusted to suit the amount of rice to be cooked, thereby making it possible to cook rice that is evenly cooked regardless of the amount of rice being cooked.

[0149] Fig. 37 shows a modified example of this embodiment. In this modified example, the positions of the second IH heater 26' and the third IH heater 81 are exchanged, with the third IH heater 81 disposed on the first layer and the second IH heater 26' disposed on the second layer. With this configuration, the same effects as those of the third embodiment can be achieved.

[0150] 38 and 39 show a further modified example of this embodiment. In this modified example, a first IH heater 25' and a second IH heater 26' are connected in series to simplify the circuit configuration of the bottom surface heating element 11.

[0151] 38 is a schematic diagram showing the main parts around the bottom heater 11. In this modification, the first IH heater 25' and the second IH heater 26' are connected in series, so the first IH heating drive unit 32 and the second IH heating drive unit 33 are combined into one IH heating drive unit, and the bottom heater 11 is driven by two units, this IH heating drive unit and the third IH heating drive unit 34, simplifying the circuit configuration of the bottom heater 11. In addition, by changing the intermittent current conduction rate of the first and second IH heaters 25', 26' connected in series and the third IH heater 81 according to the amount of rice to be cooked, a more finely balanced heating can be achieved, resulting in more evenly cooked rice.

[0152] 39(A)(B), when the amount of rice cooked at the rated maximum cooking amount is large, as shown in FIG. 39(A), the first layer IH heater of the first and second IH heaters 25', 26' connected in series heats the lower side 7c and bottom 7b by adjusting the heating amount, for example, from a minimum of 0 W to a maximum of 900 W, and the third IH heater 81 heats the bottom 7b by adjusting the heating amount, for example, from a minimum of 0 W to a maximum of 500 W. Therefore, as in the third embodiment, external convection C1 and internal convection C2 of heat occur simultaneously in the food S in the pot 7, and internal convection C6 of heat also occurs, so that the blowing up, which is the pressure rise from the bottom 7b in the pot 7, can be strengthened, and insufficient heating of the center of the food S in the pot 7 can be suppressed, making it possible to cook rice without uneven cooking.

[0153] Also, when the amount of cooked rice is small, as shown in Fig. 39(B), heating is not performed by the first and second IH heaters 25', 26' in the first layer, and the bottom 7b of the pot 7 is heated by the third IH heater 81 in the second layer, thereby generating internal convection C6 and external convection C6 of heat in the pot 7. Therefore, as in the third embodiment, it is possible to suppress the risk of excessive gelatinization of the rice on the surface of the pot, which may result in excess moisture. It is also possible to reduce heating loss and improve the heating efficiency in the rice cooking process.

[0154] When the amount of rice to be cooked is medium, heating is not performed using the third IH heater 81, and instead the first IH heater 25' heats the lower part 7c of the side of the pot 7 to generate an external convection C1 of heat within the pot 7, and the second IH heater 26' heats the bottom 7b to generate an internal convection C2 of heat within the pot 7. EXAMPLES

[0155] 40 to 42 show a fourth embodiment of the rice cooker of the present invention. Up to this point, it has been explained that in the boiling heating process and the continuous boiling process, which are the main heating processes, the heating balance and heating amount of the first to third IH heaters 25 to 27 are independently adjusted to suit the amount of rice cooked, whether large, medium, or small, and rice can be cooked evenly regardless of the amount of rice cooked. However, it is preferable that the first pattern stored in advance in the storage means 37 also stores control patterns for the soaking cooking process, steaming process, and warming process, which are other processes other than the boiling heating process and the continuous boiling process shown in FIG. 5. In this case, in each of the soaking cooking process, steaming process, and warming process, it is possible to independently adjust the heating balance and heating amount of the first to third IH heaters 25 to 27 independently adjusted to suit the amount of rice cooked, whether large, medium, or small.

[0156] An example of the heating balance in each process is shown. Fig. 40 shows the case of a small amount, Fig. 41 shows the case of a medium amount, and Fig. 42 shows the case of a large amount. Note that pattern (1) shown in the figures means that all of the first to third IH heaters 25-27 are controlled on and off, pattern (2) means that the first and second IH heaters 25-26 are controlled on and off (the third IH heater 27 is off), and pattern (3) means that the first IH heater 25 is controlled on and off (the second and third IH heaters 26-27 are off).

[0157] As shown in Figures 40 to 42, by controlling the heating balance of the first to third IH heaters 25 to 27 according to the amount of rice to be cooked in the soaking process, if the amount of rice to be cooked is set before cooking, it is possible to control the heating balance according to the amount of rice to be cooked from the beginning of cooking. Specifically, by varying the heating balance in the soaking cooking process according to the water temperature and time in the soaking cooking process, which are set according to various cooking selections, it is possible to promote the desired sweetness and umami and make them uniform in the pot.

[0158] In addition, by controlling the heating balance of the first to third IH heaters 25-27 according to the amount of rice to be cooked in the steaming process, if the amount of rice to be cooked is set before cooking, it is possible to control the heating balance according to the amount of rice to be cooked with greater accuracy.

[0159] Furthermore, by controlling the heating balance of the first to third IH heaters 25-27 according to the amount of rice cooked in the warming process, if the amount of rice cooked is set before cooking, it is possible to control the heating balance according to the amount of rice cooked with a higher degree of accuracy. Note that the warming process is generally performed in the order of "freshly cooked warming", "warming decreasing period", and "stable warming period", but since the purpose of "freshly cooked warming" is to provide rice with the same temperature and texture as freshly cooked rice, taking into account the time lapse between cooking and eating the rice, even when the rice is kept warm, controlling the heating balance in "freshly cooked warming" is particularly effective.

[0160] The present invention is not limited to the above-mentioned embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the configurations characteristic of the first to fourth embodiments may be combined. Furthermore, the numerical values ​​exemplified in the embodiments are merely examples, and may be modified as appropriate according to the specifications of the rice cooker. [Explanation of symbols]

[0161] 4 Operation section (selection means) 7. Hotpot 7a Upper side 7b bottom 7 7c lower side 7d bottom 11 Bottom heating element (heating means) 25,25' First IH heater 26,26',71 Second IH heater 27,72,81 Third IH heater 41 Rice cooking control means (control means) 44 Heat amount fluctuation means (heat amount variable means)

Claims

1. A cylindrical pot with a bottom for accommodating food to be cooked; A heating means for heating the pan; The pot has a generally cylindrical upper side, a generally disk-shaped bottom, and a lower side extending from an outer periphery of the bottom and connecting to the upper side, The bottom portion is formed so that the lowest part that comes into contact with a flat surface when the pot is placed on the flat surface is provided on the outer periphery and the height increases toward the center of the bottom portion. The side lower portion has a shape that is inclined from the side upper portion toward the bottom portion, the heating means includes a first IH heater provided to face the lower side surface, a second IH heater provided to face the lowermost portion, and a third IH heater provided to face the bottom portion; The heating amount of the first IH heater, the heating amount of the second IH heater, and the heating amount of the third IH heater are each independently adjustable, The heating balance of the first IH heater, the second IH heater, and the third IH heater is adjusted according to the amount of the food to be cooked, When the amount of food to be cooked is large compared to the rated maximum cooking amount, (i) a heating balance is performed in which the first, second and third IH heaters are heated simultaneously, then (ii) a heating balance is performed in which the first and second IH heaters are heated simultaneously, and then (iii) a heating balance is performed in which the first and third IH heaters are heated simultaneously, and the heating balances of (i) to (iii) are thereafter repeated in order.

2. A cylindrical pot with a bottom for accommodating food to be cooked; A heating means for heating the pan; The pot has a generally cylindrical upper side, a generally disk-shaped bottom, and a side wall extending from the outer periphery of the bottom. and a side lower portion connected to the side portion, The bottom portion is formed so that the lowest part that comes into contact with a flat surface when the pot is placed on the flat surface is provided on the outer periphery and the height increases toward the center of the bottom portion. The side lower portion has a shape that is inclined from the side upper portion toward the bottom portion, the heating means includes a first IH heater provided to face the lower side surface, a second IH heater provided to face the lowermost portion, and a third IH heater provided to face the bottom portion; The heating amount of the first IH heater, the heating amount of the second IH heater, and the heating amount of the third IH heater are each independently adjustable, The heating balance of the first IH heater, the second IH heater, and the third IH heater is adjusted according to the amount of the food to be cooked, When the amount of food being cooked is medium relative to the rated maximum cooking amount, (iv) a heating balance is performed in which the first and second IH heaters are heated simultaneously, then (v) a heating balance is performed in which the second and third IH heaters are heated simultaneously, and thereafter, the heating balances of (iv) and (v) are repeated in sequence.

3. A cylindrical pot with a bottom for accommodating food to be cooked; A heating means for heating the pan; The pot has a generally cylindrical upper side, a generally disk-shaped bottom, and a lower side extending from an outer periphery of the bottom and connecting to the upper side, The bottom portion is formed so that the lowest part that comes into contact with a flat surface when the pot is placed on the flat surface is provided on the outer periphery and the height increases toward the center of the bottom portion. The side lower portion has a shape that is inclined from the side upper portion toward the bottom portion, the heating means includes a first IH heater provided to face the lower side surface, a second IH heater provided to face the lowermost portion, and a third IH heater provided to face the bottom portion; The heating amount of the first IH heater, the heating amount of the second IH heater, and the heating amount of the third IH heater are each independently adjustable, The heating balance of the first IH heater, the second IH heater, and the third IH heater is adjusted according to the amount of the food to be cooked, When the amount of food to be cooked is small compared to the rated maximum cooking amount, (vi) a heating balance is performed in which the second and third IH heaters are heated simultaneously, then (vii) a heating balance is performed in which the second IH heater is heated, and then (viii) a heating balance is performed in which the third IH heater is heated, and thereafter, the heating balances of (vi) to (viii) are repeated in order.

4. A rice cooking control means for changing the amount of heat of the heating means in a first pattern as the process progresses to cook the food to be cooked; The rice cooker according to any one of claims 1 to 3, further comprising a heat amount varying means for varying the amount of heat of the heating means over time in a second pattern different from the first pattern when the rice cooking control means controls the heating means to heat the pot.

5. A selection means for selecting a heating pattern of the heating means; and a control means for controlling the heating means based on the selected heating pattern, The rice cooker according to any one of claims 1 to 4, characterized in that the control means changes the heating amount of the first IH heater, the heating amount of the second IH heater, and the heating amount of the third IH heater based on the selected heating pattern.

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