rice cooker

Abstract

To provide a rice cooker capable of suppressing an occurrence of noise at the time of heat retention.SOLUTION: A rice cooker includes a pot 4 for storing a material to be cooked containing water, a side coil 11-1 and a bottom coil 11-2 for heating the pot 4, and heat retention control means 52 for controlling the side coil 11-1 and the bottom coil 11-2. In a heat-retention process, which is a process for retaining heat of the material to be cooked, the heat retention control means 52 executes control to heat the pot 4 using only one of the side coil 11-1 and the bottom coil 11-2.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This invention relates to a rice cooker capable of keeping cooked food warm using electromagnetic induction heating. [Background technology]

[0002] As an example of this type of rice cooker, Patent Document 1 discloses one comprising an inner pot for containing the food to be cooked, a plurality of induction heating coils for induction heating the inner pot, a microcomputer for controlling the induction heating coils, and a pot temperature sensor for detecting the temperature of the inner pot. The microcomputer controls the induction heating coils based on the value detected by the pot temperature sensor, and keeps the rice in the inner pot warm at either the high or low end of the edible temperature range. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-14546 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the rice cooker described in Patent Document 1, when heating the cooked rice using multiple induction heating coils during the warming period, all of the multiple induction heating coils are used for heating, and the heating is controlled to either energize all of the multiple induction heating coils simultaneously or to sequentially switch the energization of the multiple heating coils. However, when the energization of the multiple induction heating coils is switched using a mechanical switch such as a relay, a mechanical noise is frequently generated when the energization of the induction heating coils is switched by this mechanical switch, resulting in a problem of high noise during the warming period.

[0005] Therefore, the present invention aims to provide a rice cooker that suppresses noise generation during the warming process. [Means for solving the problem]

[0006] The rice cooker of the present invention comprises a pot for containing the food to be cooked, a plurality of heating coils for heating the pot, and control means for controlling the plurality of heating coils, wherein the control means controls all of the plurality of heating coils during the cooking process, which is the process of cooking the food to be cooked. alternately In the heat-keeping process, which is the process of keeping the cooked food warm, only one of the plurality of heating coils is used, and the heat-keeping process does not change the temperature of the cooked food. The period and Maintain the temperature of the cooked rice period Includes multiple periods In addition, multiple periods of alternating periods of changing the temperature of the cooked food and maintaining the temperature of the cooked food are performed. The control means, in the heat retention process, when the period transitions Ru Ta timing , messenger The method is characterized by controlling the heating of the pot by switching the energizing pattern by changing at least one of the energizing time, output, or non-energizing time of the one coil used. [Effects of the Invention]

[0007] According to the rice cooker of the present invention, the generation of mechanical noise caused by mechanical switches such as relays when switching between multiple heating coils can be suppressed, thereby suppressing noise generation during the warming process. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of a rice cooker showing one embodiment of the present invention. [Figure 2] The same as above, this is a vertical cross-section of the rice cooker. [Figure 3] The same as above, a cross-sectional view of the inner frame and heating coil, and a plan view from the bottom side. [Figure 4] The same as above, this is a block diagram showing the electrical configuration of a rice cooker. [Figure 5] The graph above shows the changes over time in the temperature detected by the pot temperature sensor, the temperature detected by the lid temperature sensor, the output of the bottom coil, and the output of the side coil during the rice cooking process. [Figure 6]It is a graph showing the change over time of the pot temperature in the capacity determination step according to the amount of the object to be cooked rice in a conventional rice cooker and the rice cooker of the present embodiment. [Figure 7] It is a graph showing the change over time of the detected temperature of the pot temperature sensor, the output of the bottom coil, and the output of the side coil in the heat preservation step of the rice cooker showing one embodiment of the present invention. [Figure 8] It is a graph showing the change over time of the detected temperature of the pot temperature sensor, the output of the bottom coil, and the output of the side coil in the heat preservation step of the rice cooker showing a modified example of the present embodiment.

Mode for Carrying Out the Invention

[0009] Hereinafter, preferred embodiments of the rice cooker according to the present invention will be described with reference to the accompanying drawings. In all these drawings, common parts will be given common reference numerals.

[0010] FIGS. 1 to 7 show an embodiment of the rice cooker according to the present invention. First, the configuration of the entire rice cooker will be described based on FIGS. 1 and 2. 1 is the main body, which has a substantially rectangular shape with the front and rear surfaces, the left and right side surfaces facing each other when viewed from above, and the upper surface is open. 2 is a lid that opens and closes the upper surface opening of the main body 1. Similar to the main body 1, it has a substantially rectangular shape with the front and rear surfaces, the left and right side surfaces facing each other when viewed from above, and the upper surface is configured to be substantially flat. The main body 1 has a pot accommodating portion 3 with an open upper surface. When the lid 2 is opened, a bottomed pot 4 as a container for accommodating water and rice, which are the objects to be cooked rice, is detachably accommodated in the pot accommodating portion 3. The pot accommodating portion 3 is configured by combining an inner frame 5 made of resin in a bowl shape, and is formed in an overall bottomed cylindrical shape.

[0011] The pot 4 is made primarily of aluminum 7, which has good thermal conductivity, and a heating element 8 made of a magnetic metal plate such as ferritic stainless steel is joined to the lower side and bottom of the outer surface of the main material 7. In addition, a heating coil 11 is provided on the outer surface of the inner frame 5, which faces the bottom surface of the pot 4 from the lower side surface, as a heating means for electromagnetic induction heating of the heating element 8 of the pot 4. When a high-frequency current is supplied to the heating coil 11, the heating element 8 of the pot 4 heats up due to the alternating magnetic field generated from the heating coil 11, and the contents of the pot 4 are heated during cooking and warming. The heating coil 11 will be explained in detail later. A pot sensor 12, which serves as a means for detecting the pot temperature, is positioned in the center of the bottom of the inner frame 5 so as to make elastic contact with the bottom surface of the outer surface of the pot 4.

[0012] A hinge 13 is provided at the rear of the lid 2, which serves as the connection point with the main body 1. A lid operating body 14 is also exposed on the front upper surface of the lid 2. When this lid operating body 14 is pressed, the engagement between the main body 1 and the lid 2 is released, and the lid 2 opens around the hinge axis of the hinge 13 by a hinge spring (not shown) provided at the upper rear of the main body 1.

[0013] A steam vent 15 is provided on the rear upper surface of the lid 2 to release steam generated from the food being cooked in the pot 4 to the outside of the rice cooker. In addition to the steam vent 15 and the lid operating unit 14, the top surface of the lid 2 is also provided with a display means 18 consisting of an LCD (Liquid Crystal Display) 16 as a screen display unit and an LED (Light Emitting Diode) display unit 17 as a status display unit for displaying various information related to rice cooking, as well as an operating means 19 consisting of a touch sensor and positioned above the LCD 16 for starting rice cooking, selecting the time and cooking course, etc. A control PC (Printed Circuit) board 21 is positioned on the lower surface of the display means 18 and the operating means 19.

[0014] The LED display unit 17 displays the actual status of the rice cooker. In this embodiment, the "Reservation" LED display unit lights up when a reservation setting is made, the "Keep Warm" LED display unit lights up when the keep-warm state is activated, the "Vacuum" LED display unit lights up when the inside of the pot 4 is reduced to a pressure lower than atmospheric pressure by the depressurization means 38 (described later), and the "Pressure" LED display unit lights up when the inside of the pot 4 is pressurized from the time pressure starts to build up inside the pot 4 during cooking until the rice is cooked. Therefore, even when the backlight of the LCD 16 is dimmed, the user can understand the current status of the rice cooker at a glance by checking the LED display unit 17. The color of the light when each LED display unit of the LED display unit 17 lights up may be different, allowing the user to understand the current status of the rice cooker at a glance. In this embodiment, the LED display unit 17 is located directly in front of the LCD 16, but it may be located at a distance from the LCD 16. Alternatively, the LED display unit 17 may be omitted, and the content of the LED display unit 17 may be displayed on the LCD 16.

[0015] The operating means 19, which consists of touch sensors, is configured such that, for example, multiple touch keys are arranged, each consisting of a transparent electrode portion made of conductive polymer and a contact portion connected to the control PC board 21, connected by pattern wiring. By touching one of the multiple button display portions shown on the LCD 16, the touch key located above that button display portion and corresponding to that button display portion is touched, and that button display portion is selected.

[0016] In this way, considering user operability and safety, the lid operating element 14 is positioned on the upper front side of the rice cooker, which is closer to the user, and the steam vent 15 is positioned on the upper rear side of the rice cooker, which is further away from the user. This allows for ample space on the upper surface of the lid 2 between the lid operating element 14 and the steam vent 15 to accommodate the display means 18, and thus allows for a larger display means 18 and the operating means 19 positioned above it, thereby improving the visibility of the display means 18 and the operability of the operating means 19. Furthermore, on the upper surface of the lid 2, apart from the operating means 19 above the LCD 16, there are no physical keys or buttons such as a cooking key or off key that were present in conventional rice cookers. Since the rice cooker is operated solely by the operating means 19, the effort of searching for buttons during operation is eliminated, improving operability. In addition, a very sleek appearance can be achieved, and the space occupied by precision components such as the display means 18 and operating means 19 can be made compact. Furthermore, by excluding physical keys and buttons, the top surface of the lid 2 can be made almost flat, making it easier to wipe clean and improving ease of maintenance.

[0017] An inner lid assembly 23, which serves as the lower component of the lid 2, is provided on the underside of the lid 2. The inner lid assembly 23 is made of a metal material and has a disc shape with approximately the same diameter as the upper opening of the pot 4. It comprises an inner lid 24 that covers the upper opening of the pot 4, a lid packing 25 which is an elastic member provided around the entire outer circumference of the inner lid 24 to seal the space between the inner lid 24 and the pot 4, and a pressure regulating unit 26 that adjusts the internal pressure of the pot 4. The annularly formed lid packing 25, as shown in Figure 2, contacts the upper surface of the pot 4, which is the opening, when the lid 2 is closed, sealing the gap between the pot 4 and the inner lid 24 and sealing in the steam generated from the pot 4.

[0018] Inside the lid 2, a lid opening / closing detection means 27 is provided near the hinge 13 to detect the opening and closing of the lid 2. The lid opening / closing detection means 27 can be of any detection type, such as optical, mechanical, or magnetic, as long as it can output a detection signal corresponding to the opening and closing of the lid 2. Inside the lid 2, a lid heater 31 is provided as a lid heating means for heating the inner lid 24, and a thermistor-type lid temperature sensor 32 is provided for controlling the temperature of the inner lid 24 using the lid heater 31. Inside the lid 2, a steam discharge path 33 is formed, connecting the steam vent 15 and the pressure regulating unit 26, as a passage for releasing steam generated in the pot 4 to the outside.

[0019] The pressure regulating unit 26 is equipped with a pressure regulating valve 34 that opens and closes the steam discharge path 33 between the inside of the pot 4 and the steam vent 15. The pressure regulating valve 34 is ball-shaped and works in conjunction with a solenoid 35 installed inside the lid 2. The solenoid 35 rotates the pressure regulating valve 34 so as to open the steam discharge path 33 when releasing steam from inside the pot 4 to the outside, and close the steam discharge path 33 when pressurizing or depressurizing the inside of the pot 4. When pressurizing, the food being cooked inside the pot 4 is heated by high-frequency current applied to the heating coil 11, causing the food to boil and generate steam. When this steam fills the inside of the pot 4 and the internal pressure of the pot 4 reaches a predetermined value, the pressure regulating valve 34 opens the steam discharge path 33 against its own weight, thereby maintaining the pressure inside the pot 4 at or above atmospheric pressure. A pressure sensor 36 (see Figure 3) is also installed inside the lid 2, facing the pressure regulating unit 26, to detect the pressure inside the pot 4.

[0020] 38 is a pressure reducing means for lowering the pressure inside the pot 4 to below normal atmospheric pressure when the lid 2 is closed on the main body 1. The pressure reducing means 38 reduces the internal pressure of the sealed pot 4 by energizing the solenoid 35 after the pot 4 is placed in the pot housing 3 and the lid 2 is closed, causing the pressure regulating valve 34 to block the steam discharge path 33. Furthermore, when the pressure inside the pot 4 falls below a certain value below atmospheric pressure, the operation of the pressure reducing pump 39, which is the operating source of the pressure reducing means 38, is stopped, and the inside of the pot 4 is kept in a reduced pressure state. In addition, when returning the inside of the pot 4 from a reduced pressure state to the same pressure as the outside air, the operation of the pressure reducing pump 39 is stopped, and a path (not shown) connecting the pressure reducing pump 39 and the inside of the pot 4 is opened. In other words, the pressure reducing means 38 also serves as a pressure return means for returning the inside of the pot 4 from a reduced pressure state to the same pressure as the outside air.

[0021] In addition, a unitized heating board assembly 42, including a control means 41, is arranged inside the main body 1. The control means 41 is configured to electrically control each part of the rice cooker and includes a control IC 43 that constitutes a microcomputer, a storage means 44 (see Figure 4) such as a memory that can read and write various information and data, and a timing means 45 (see Figure 4) such as a timer that can measure the time related to rice cooking. In particular, the control means 41 is configured to mainly control the heating coil 11 based on the temperature detected by the pot sensor 12 to manage the temperature of the bottom of the pot 4, and to mainly control the lid heater 31 based on the temperature detected by the lid temperature sensor 32 to manage the temperature of the inner lid 24 that faces the rice being cooked.

[0022] Figure 3 shows a cross-sectional view and a plan view of the inner frame 5 and heating coil 11 as seen from the bottom side. Referring to this figure, the heating coil 11 in this embodiment is composed of a side coil 11-1 as the first coil and a bottom coil 11-2 as the second coil. The side coil 11-1 and the bottom coil 11-2 are each provided on the outer surface of the inner frame 5, that is, the outer surface of the pot storage section 3, so as to face the pot 4. Specifically, when the pot 4 is placed in the pot storage section 3, the bottom coil 11-2 is positioned as a bottom heater facing the outer surface of the bottom of the pot 4, and the side coil 11-1 is positioned as a side-bottom heater outside and above the bottom coil 11-2, facing the outer surface of the lower side of the pot 4. In this embodiment, the maximum output of the heating coil 11 is, for example, 1400W for both the side coil 11-1 and the bottom coil 11-2. However, these values ​​are merely examples, and the output balance of the side coil 11-1 and the bottom coil 11-2 can be arbitrarily set according to the heating characteristics of the rice cooker. In this embodiment, the heating coil 11 is composed of two heating coils, but the present invention is not limited thereto, and may be composed of many more heating coils. In that case as well, each heating coil is arranged concentrically facing the lower side of the pot 4 from the bottom, and multiple heating coils are arranged in a vertical direction. Furthermore, the side coil 11-1 and the bottom coil 11-2 may each be individually formed in a helical shape, or they may be formed in a concentric circular shape, and there are no particular restrictions on the shape of each heating coil.

[0023] To explain the heat transfer when the heating coil 11 is driven, when the side coil 11-1 is energized, the outer surface of the lower side of the pot 4, which is opposite the side coil 11-1, becomes hot first, and this heat is transferred via the main material 7 to the water in the cooked food that is in contact with the lower side. Heat transfer in the cooked food mainly occurs together with the movement of water, but where rice is present, the movement of water is restricted to only the narrow gaps between the rice grains, and the movement of water and heat slows down. On the other hand, where there is no rice, the movement of water and heat becomes more active due to convection, so after the water in the cooked food that is in contact with the lower side, the water in the upper part of the cooked food, where there is no rice because it sinks downwards, becomes hot. Subsequently, in the central part of the cooked food, the water and heat from the upper part of the cooked food, which has become hot, move to the middle part of the cooked food, which is a low-temperature part, and then move to the lower part of the cooked food. This phenomenon is what is called thermal convection, and in this embodiment it will be explained as external convection.

[0024] When the bottom coil 11-2 is energized, the outer surface of the bottom of the pot 4, which is opposite the bottom coil 11-2, becomes hot first, and this heat is transferred via the main material 7 to the water in the cooked food that is in contact with the bottom. In the lower part of the cooked food, the rice has settled downwards, so the upper part of the lower part is covered with the rice and water, and the temperature and pressure of this water rise. Subsequently, the water in the lower part, which has become hotter and more pressured, moves upward through the gaps between the rice grains, and is blown upward. As a result, the water in the lower part that has become hotter, i.e., the hot water, moves along with the heat to the middle part of the cooked food, and then to the upper part. This phenomenon is called blowing up, and in this embodiment, it is described as internal convection.

[0025] Therefore, by alternately energizing the side coil 11-1 and the bottom coil 11-2, alternating external and internal heat convection occurs in the food being cooked in the pot 4. This promotes the stirring of the water in the food being cooked in the pot 4, thereby reducing uneven heating.

[0026] Figure 4 shows the electrical configuration of the rice cooker in this embodiment. In the figure, the input port of the control means 41 is electrically connected to the pot sensor 12, the lid temperature sensor 32, the pressure sensor 36, the lid opening / closing detection means 27, and the operating means 19. In addition to the solenoid 35, the pressure reducing pump 39, and the display means 18 mentioned above, the output port of the control means 41 is electrically connected to the side coil driving means 46 connected to the side coil 11-1, the bottom coil driving means 47 connected to the bottom coil 11-2, and the lid heater driving means 48 connected to the lid heater 31.

[0027] The side coil driving means 46 receives a heating control signal from the control means 41 and supplies a high-frequency current to energize the side coil 11-1, while the bottom coil driving means 47 receives a heating control signal from the control means 41 and supplies a high-frequency current to energize the bottom coil 11-2. These side coil driving means 46 and bottom coil driving means 47 are configured with, for example, a power supply circuit, an inverter, an IH drive circuit, and a switch element, and the output from the side coil 11-1 and bottom coil 11-2 to the pot 4 can be increased or decreased by changing the period of the high-frequency current supplied to the side coil 11-1 and bottom coil 11-2, and the ratio of the ON time to one period (ON ratio). The lid heater driving means 48 receives a heating control signal from the control means 41 and drives the lid heater 31 by supplying a DC current or AC current. In this embodiment, the current supply to the side coil 11-1 and the bottom coil 11-2 is described as being selectively switched by a switch element, but the present invention is not limited to this, and may include a period in which the side coil 11-1 and the bottom coil 11-2 are energized simultaneously.

[0028] The control means 41 receives temperature detection signals from the pot sensor 12 and lid temperature sensor 32, a pressure detection signal from the pressure sensor 36, a detection signal from the lid opening / closing detection means 27, and an operation signal from the operation means 19, and outputs a display control signal to the display means 18. It also outputs heating control signals to the side coil drive means 46 and bottom coil drive means 47, which energize the side coil 11-1 and bottom coil 11-2 of the heating coil 11, and to the lid heater drive means 48, which drives the lid heater 31. It also outputs drive control signals to the solenoid 35 that moves the pressure regulating valve 34 and to the pressure reducing pump 39 of the pressure reducing means 38. This control means 41 is equipped with a rice cooking control means 51, a warming control means 52, and a display control means 53 as functions of the control sequence of the program read from the storage means 44, on the control IC 43.

[0029] The rice cooking control means 51, upon receiving an instruction from the operation means 19 to start rice cooking, sequentially executes the following steps to control the rice cooking process inside the pot 4 at a desired pressure: a soaking process to promote water absorption of the rice placed in the pot 4, a boiling heating process to quickly raise the temperature of the rice to be cooked to a boil, a boiling continuation process to maintain the boiling state of the rice, and a steaming process to maintain a high temperature that prevents the rice from burning. The heat retention control means 52 controls the rice inside the pot 4 to maintain a predetermined heat retention temperature. The display control means 49 generates various control signals based on the operation signals from the operation means 19 and also controls the display operation of the display means 18.

[0030] The storage means 44 stores, for example, rice cooking courses corresponding to the settings for each type of rice, cooking method, and hardness. The rice settings, cooking method, and hardness settings of the rice cooking courses stored in the storage means 44 are displayed on the display means 18 for selection, and the user selects and sets these settings using the operation means 19, thereby selecting and setting the rice cooking course. Furthermore, the memory means 44 stores multiple heating patterns, which are the driving patterns of the heating coil 11, lid heater 31, pressure regulating valve 34, and pressure reducing means 38, specifying the timing and output at which the heating coil 11, lid heater 31, pressure regulating valve 34, and pressure reducing means 38 are driven, as well as multiple energizing patterns, which are the energizing patterns of the side coil 11-1 and bottom coil 11-2, specifying the timing and output at which the side coil 11-1 and bottom coil 11-2 are energized when the heating coil 11 is driven. The rice cooking control means 51 and the warming control means 52 control the heating coil 11, lid heater 31, pressure regulating valve 34, and pressure reducing means 38 based on these heating patterns and energizing patterns.

[0031] The energizing pattern of this embodiment is a pattern that includes the energizing time and output of the side coil 11-1 and the bottom coil 11-2. For example, the side coil 11-1 is energized with output W1 and energizing time T1, then the coil is switched to energize the bottom coil 11-2 with output W2 and energizing time T2, and this is repeated for a predetermined period of time. The energizing pattern also includes cases where only the energizing time and output of the coil are varied, while the other remains constant. For example, this includes cases where the energizing time is constant among multiple coils but the output differs for each coil, or where the output is constant among multiple coils but the energizing time differs for each coil.

[0032] Here, "switching the energizing pattern" means switching the energizing pattern itself. To explain using the example above, it means switching from an energizing pattern that repeatedly energizes the side coil 11-1 with output W1 and energizing time T1, and then energizes the bottom coil 11-2 with output W2 and energizing time T2, to an energizing pattern that repeatedly energizes the side coil 11-1 with output W3 and energizing time T3, and then energizes the bottom coil 11-2 with output W4 and energizing time T4, at a predetermined timing.

[0033] The energizing pattern may include a switching time during which the energizing of all coils is turned OFF when the coils are switched. That is, the energizing pattern may consist of energizing one coil for a predetermined time and output → switching time 1 → energizing the other coil for a predetermined time and output → switching time 2, and repeating this as one cycle. Here, switching time 1 and switching time 2 may be the same time or they may be different times.

[0034] The energizing time and output of the side coil 11-1 and bottom coil 11-2 in each energizing pattern may be values ​​determined by the inventors of the present invention through diligent experimentation in each process. For example, the energizing time of the side coil 11-1 and bottom coil 11-2 is preferably several seconds or more, which allows for the alternating generation of external and internal heat convection in the cooked rice in the pot 4 for a predetermined period of time or longer, thereby promoting the stirring of the water in the cooked rice in the pot 4 and reducing uneven heating.

[0035] Furthermore, the inventors of this application have found that it is preferable that the time for generating external and internal convection is not the same in one energizing pattern. That is, it is preferable that the energizing times of the side coil 11-1 and the bottom coil 11-2 in one energizing pattern are not the same, and that the energizing times of the switched coils are different before and after the switching of the coils during repetition.

[0036] Furthermore, in the heat retention process, as will be described later, there is also a power supply pattern in which the energization of one coil is controlled while the other coil is not energized. In this power supply pattern, one coil is energized for a predetermined time and output, and then the same coil is not energized for a predetermined time, and this process is repeated.

[0037] Next, the operation of the rice cooker with the above configuration during the rice cooking process will be explained. Figure 5 shows the pot temperature t1, which is the temperature detected by the pot temperature sensor 12, the lid temperature t2, which is the temperature detected by the lid temperature sensor 31, and the output P of the bottom coil 11-2 during the rice cooking process of the rice cooker of this embodiment. B And the output P of the side coil 11-1 S The changes in and over time are shown in the graphs.

[0038] Referring to Figure 5, the operation of this embodiment during rice cooking is as follows: First, rice and water (as liquid) are placed in the pot 4, and after setting the pot 4 in the pot storage section 3, the lid 2 is closed. Around the same time, when the rice cooker is powered on, the main body 1 and lid 2 enter an initial off (standby) state where cooking and warming are not taking place.

[0039] Then, when the operation means 19 is used to issue an instruction to start cooking after setting the cooking course, the cooking control means 51 performs the following cooking operations for the food to be cooked in the pot 4, in accordance with the heating pattern set for the current cooking course: soaking, boiling, continuing to boil, and steaming.

[0040] During the soaking and cooking process, the rice cooking control means 51 controls the operation of the pressure regulating unit 26 and the pressure reducing means 38 respectively so that the pressure inside the pot 4 is lower than atmospheric pressure. Specifically, when the soaking and cooking process begins, the rice cooking control means 51 controls the solenoid 35 to close the steam discharge path 33 with the pressure regulating valve 34. In this state, based on the pressure detection by the pressure sensor 36, the rice cooking control means 51 opens the path of the pressure reducing means 38 and operates the vacuum pump 39 continuously to perform vacuuming, removing the air from inside the sealed pot 4 with the vacuum pump 39. The display control means 53 also controls the LED display unit 17 to light up the "vacuum" process LED display unit. Subsequently, the rice cooking control means 51 controls the pressure reducing means 38 so that the pressure inside the pot 4 is maintained below a certain value in a reduced pressure state lower than atmospheric pressure. In this way, the inside of the pot 4 is kept in a reduced pressure state for the entire duration of the soaking and cooking process.

[0041] When the soaking and cooking process begins, the rice cooking control means 51 outputs a heating control signal to the side coil driving means 46, controlling the side coil 11-1 to heat the pot 4 at a predetermined output for a predetermined time T1. After time T1 has elapsed, the rice cooking control means 51 controls the side coil 11-1 to stop heating the pot 4 for a predetermined time T2, and performs a capacity determination process to determine the cooking capacity, which is the amount of rice to be cooked, based on the pot temperature t1 after time T2 has elapsed. The predetermined time T2 is set to a time that allows for a temperature drop sufficient to enable capacity determination from the time T1 when heating stops. In this embodiment, in the capacity determination process, the bottom coil 11-2, which is the heating coil 11 closest to the pot sensor 12, is not used, and only the side coil 11-1, which is the heating coil 11 furthest from the pot sensor 12, is used to heat the pot 4. Therefore, the pot sensor 12 is suppressed from being affected by the heating of the heating coils 11, and the deterioration of the accuracy of temperature detection by the pot sensor 12 can be suppressed.

[0042] Here, in the present embodiment, the heating time T1 of the pot 4 in the capacity determination step is set to 30 seconds or more. This "30 seconds" is the time required to distinguish the minimum capacity, which is the minimum capacity for the capacity determination, from other capacities. Also, the time T2 for stopping the heating of the pot 4 in the capacity determination step is set to 1 minute or more. This "1 minute" is the time required to distinguish the minimum capacity from other capacities. Therefore, for example, in the "quick cooking" course, which is a course that prioritizes time in the rice cooking course, the time T1 may be set to 30 seconds and the time T2 may be set to 1 minute.

[0043] Also, in the present embodiment, when the rice cooking control means 51 receives a detection signal that the pot temperature t1 has reached 60°C by the pot sensor at the heating time T1 of the pot 4, the rice cooking control means 51 stops the heating of the pot 4 at the time of receiving the detection signal, and then controls the side coil 11-1 so as to stop the heating of the pot 4 for a predetermined time T2. When the rice and water, which are the objects to be cooked, reach 60°C or higher, the gelatinization of the rice during water absorption of the rice may be promoted, and the cooking of the rice may deteriorate. Therefore, in the capacity determination step, the pot temperature t1 is made less than 60°C to suppress the gelatinization of the rice during water absorption of the rice.

[0044] FIG. 6 graphically shows the change over time of the pot temperature of a conventional rice cooker and the change over time of the pot temperature of the rice cooker of the present embodiment in the capacity determination step of the simmering cooking process, for each amount of the object to be cooked. Here, t shown by the solid line 0O , t 0B , t 0M , t 0S is a graph of the detected temperature of the pot sensor 12 when the amount of the object to be cooked in the conventional rice cooker is extra-large, large, medium, and small, and t shown by the dotted line 1O , t 1B , t 1M , t 1S is a graph of the pot temperature t1, which is the detected temperature of the pot sensor 12 when the amount of the object to be cooked in the rice cooker of the present embodiment is extra-large, large, medium, and small. Conventionally, both the side coil 11-1 and the bottom coil 11-2 are used to heat the pot 4. Especially when the capacity is small, t 0SIn some cases, the temperature of the bottom of pot 4 could rise too high, such as to nearly 60°C, causing the rice to gelatinize prematurely. Therefore, in this embodiment, only the side coil 11-1 is used, and the overall output of the heating coil 11 is suppressed compared to conventional rice cookers to heat pot 4 and prevent the temperature of the bottom of pot 4 from rising.

[0045] In this embodiment, the rice cooking control means 51 determines the cooking capacity based on the pot temperature t1 at the end of time T2. The capacity determination based on the pot temperature t1 at the end of time T2 may be based solely on the pot temperature t1 at the end of time T2, on the difference between the pot temperature t1 at the end of time T2 and the pot temperature at the start of the soaking and cooking process, or on the difference between the pot temperature t1 at the end of time T2 and the pot temperature t1 at time T1 when heating stopped. Furthermore, the pot temperature t1 at the start of the soaking and cooking process may be set to a predetermined fixed value.

[0046] In this embodiment, the cooking capacity is determined solely by the pot temperature t1 at the end of time T2. Here, the cooking capacity can be determined, for example, by setting threshold ranges for the amount of rice to be cooked (extra large, large, medium, and small) relative to the pot temperature at the end of time T2, and determining which range the pot temperature at the end of time T2 falls into. As shown in Figure 6, at the end of time T2, the t of this embodiment 1O , t 1B , t 1M , and t 1S The temperature difference between them is different from conventional t 0O , t 0B , t 0M , and t 0S It can be seen that the temperature difference is greater than that between the two. In other words, the rice cooker of this embodiment can improve grouping accuracy and determine the cooking capacity more precisely due to the larger temperature difference. However, the present invention is not limited to this, and the method for determining the cooking capacity is just one example.

[0047] When the rice cooking control means 51 receives a timing signal from the timing means 45 indicating that time T2 has elapsed, it moves to the soaking process of the soaking cooking process. Based on the temperature detection of the bottom of the pot 4 by the pot temperature sensor 12, the rice cooking control means 51 outputs heating control signals to the side coil driving means 46 and the bottom coil driving means 47, respectively, to control the alternating energization of the side coil 11-1 and the bottom coil 11-2, thereby heating the pot 4 and performing a soaking process to raise the water temperature inside the pot 4 to a predetermined temperature, for example, 35 to 55°C, and a maximum of 60°C, as shown in Figure 5, in order to promote water absorption by the rice. The soaking process is configured to maintain the water temperature inside the pot 4 at a predetermined temperature for a predetermined time, for example, about 15 minutes, but this time can be changed arbitrarily.

[0048] Specifically, the rice cooking control means 51 controls the side coil 11-1 and the bottom coil 11-2 to alternately energize them, with the duty cycle of the bottom coil 11-2 being A% and the duty cycle of the side coil 11-1 being B%. Furthermore, throughout the entire rice cooking process, when there is a switch between energizing the side coil 11-1 and the bottom coil 11-2, the rice cooking control means 51 controls the system to include a switching time in which both the side coil 11-1 and the bottom coil 11-2 are turned OFF during the switching. The length of this switching time may be constant or may be changed according to the rice cooking process. Alternatively, the control may not include a switching time. In this embodiment, the rice cooking control means 51 controls the side coils 11-1 and bottom coils 11-2 with a constant energizing pattern during the soaking process, regardless of the amount of rice to be cooked determined in the capacity determination process. However, the control means may also change the duty cycle of the side coils 11-1 and bottom coils 11-2 and change the energizing pattern according to the amount of rice to be cooked determined in the capacity determination process. Subsequently, when the rice cooking control means 51 receives a timing signal from the timing means 45 indicating that a predetermined time has elapsed since the soaking process, it terminates the soaking process and moves on to the next boiling heating process.

[0049] When shifting to the boiling heating process, the rice cooking control means 51 outputs heating control signals to the side coil driving means 46 and the bottom coil driving means 47 respectively, and controls to alternately energize the side coil 11-1 and the bottom coil 11-2 so as to heat the rice to be cooked in the pan 4 more strongly than in the warming process, and performs a heating process of heating until the boiling of the rice to be cooked is detected.

[0050] Specifically, when shifting to the heating process, at the beginning of the heating process, the rice cooking control means 51 slightly increases the duty ratio C% of the bottom coil 11-2 compared to the duty ratio A% in the warming process (C>A), and makes the duty ratio of the side coil 11-1 and the duty ratio of the bottom coil 11-2 substantially the same, and controls with an energization pattern of alternately energizing the side coil 11-1 and the bottom coil 11-2 with an output slightly stronger than in the warming process. Here, the rice cooking control means 51 changes the energization time of the side coil 11-1 and the bottom coil 11-2 according to the amount of the rice to be cooked determined in the capacity determination process in the boiling heating process. For example, if the duty ratio of the bottom coil 11-2 is D% when the amount of the cooked rice is extra-large, E% when the amount of the cooked rice is large, F% when the amount of the cooked rice is medium, and G% when the amount of the cooked rice is small, the duty ratio is set to be larger in the order of D<E<F<G, and the duty ratio of the side coil 11-1 is set to D>E>F>G.

[0051] Also, when shifting to the boiling heating process, the rice cooking control means 51 controls the solenoid 35 to roll the pressure regulating valve 34 so as to open the steam discharge path 33, puts the inside of the pan 4 in a state of communicating with the outside of the main body 1, and discharges the steam from the rice to be cooked to the outside of the main body 1 from the steam port 15 via the steam discharge path 33. Then, the display control means 53 controls the LED display unit 17 to turn off the "vacuum" process LED display section.

[0052] Subsequently, when the rice cooking control means 51 receives a timing signal from the timing means 45 indicating that a predetermined time has elapsed since the start of the boiling heating process, it energizes the bottom coil 11-2 for J seconds and the side coil 11-1 for K seconds in one cycle, which is the same as or different from the energizing time of the bottom coil 11-2 for H seconds and the energizing time of the side coil 11-1 for I seconds in one cycle at the beginning of the heating process. It then controls the power supply pattern for a predetermined time, in the pattern of energizing the bottom coil 11-2 → switching time → energizing the side coil 11-1 → switching time, with the side coil 11-1 and bottom coil 11-2 being energized alternately at the same or lower output as at the beginning of the heating process, and outputs P B and output P S This outputs the following. Furthermore, in the subsequent boiling heating process, boiling continuation process, and steaming process, the rice cooking control means 51 controls the heating coil 11 with an energizing pattern that alternately energizes the side coil 11-1 and the bottom coil 11-2 in the pattern of energizing the bottom coil 11-2 → switching time → energizing the side coil 11-1 → switching time. At this time, the energizing time of the bottom coil 11-2 is set to be longer in the order of extra-large ≤ large ≤ medium ≤ small amount of rice to be cooked, while the energizing time of the side coil 11-1 is set to be longer in the order of small ≤ medium ≤ large ≤ extra-large amount of rice to be cooked. At this time, the period of the energizing pattern, which is the pattern of energizing the side coil 11-1 and the bottom coil 11-2 when the heating coil 11 is driven, is set to be longer in the order of small ≤ medium ≤ large ≤ extra-large. However, the present invention is not limited to these, and the period and setting of the energizing pattern are just examples.

[0053] Then, when the rice cooking control means 51 receives a timing signal from the timing means 45 indicating that a predetermined amount of time has elapsed, it controls the power supply pattern by maintaining a predetermined output (H+I≧J+K≧L+M) while making the total power supply time L+M seconds (L seconds for the power supply time of the bottom coil 11-2 and M seconds for the power supply time of the side coil 11-1) equal to or less than the total power supply time J+K seconds (J seconds for the power supply time of the bottom coil 11-2 and K seconds for the power supply time of the side coil 11-1) in the previous cycle, thereby alternately powering the side coil 11-1 and the bottom coil 11-2. Here, the power supply time of the bottom coil 11-2 is set to be longer in the order of extra-large ≤ large ≤ medium ≤ small, as before, while the power supply time of the side coil 11-1 is set to be longer in the order of small ≤ medium ≤ large ≤ extra-large. As described above, the side coils 11-1 and bottom coils 11-2 heat the food being cooked inside the pot 4, causing the pot temperature t1 detected by the pot sensor 12 and the lid temperature t2 detected by the lid temperature sensor 32 to gradually rise, as shown in Figure 5.

[0054] Subsequently, when the rice cooking control means 51 receives a temperature detection signal from the pot sensor 12 indicating that the pot temperature t1 has reached a predetermined temperature or higher, for example, 90°C or higher, and / or receives a temperature detection signal from the lid temperature sensor 32 indicating that the lid temperature t2 has reached a predetermined temperature or higher, for example, 90°C or higher, it starts a stabilization #1 step, which is a boiling detection step that detects boiling of the rice being cooked under pressure.

[0055] In the stabilization #1 step, the rice cooking control means 51 controls the solenoid 35 to roll the pressure regulating valve 34 to block the steam discharge path 33, closing the inside of the pot 4. Since the rice to be cooked is strongly heated inside the pot 4 as described above, the inside of the pot 4 is pressurized until the rice to be cooked reaches above atmospheric pressure, for example, 1.2 atmospheres, and the water in the rice to be cooked can be boiled in this pressurized state. Thereby, by boiling the water in the rice to be cooked at 105 °C (in the case of 1.2 atmospheres), which is the optimum temperature for gelatinization of rice in the pressurized state, the balance between the hardness and stickiness of the rice can be ensured. Further, the display control means 53 controls the LED display unit 17 to light the process LED display unit of "pressure". The rice cooking control means 51 may control the solenoid 35 to adjust the pressure inside the pot 4 based on the detected pressure of the pressure sensor 36, for example, according to the setting of the type of rice.

[0056] Also, the rice cooking control means 51 makes the total energization time N + O seconds of the energization time N seconds of the bottom coil 11-2 and the energization time O seconds of the side coil 11-1 in one cycle approximately equal to the total energization time L + M seconds in one cycle of the previous heating step. On the other hand, the energization time N seconds of the bottom coil 11-2 is made slightly shorter than the energization time L seconds of the bottom coil 11-2 in the previous heating step (N < L), and the energization time O seconds of the side coil 11-1 is made slightly longer than the energization time M seconds of the side coil 11-1 in the previous heating step (O > M), and it is controlled with an energization pattern in which the side coil 11-1 and the bottom coil 11-2 are energized alternately. Therefore, the rice cooking control means 51 controls the bottom coil 11-2 and the side coil 11-1 with different energization patterns in the boiling heating step and the stabilization #1 step. On the other hand, the rice cooking control means 51 controls the bottom coil 11-2 and the side coil 11-1 with different energization patterns according to the amount of the rice to be cooked, similar to the heating step.

[0057] The rice cooking control means 51 also calculates the slope of the detected temperatures, which indicates how much the temperature detected by the pot sensor 12 and the temperature detected by the lid temperature sensor 32 will rise in a predetermined time. Specifically, if the rice cooking control means 51 calculates from the temperature detected by the pot sensor 12 that the rise in the pot temperature t1, which is the temperature at the bottom of the pot 4, has fallen below a predetermined temperature rise rate, for example, 3°C or less in 120 seconds, it determines that boiling has been detected due to a change in the temperature rise rate of the pot temperature t1. Similarly, if the rice cooking control means 51 calculates from the temperature detected by the lid temperature sensor 32 that the rise in the lid temperature t2, which is the temperature of the inner lid 24, has fallen below a predetermined temperature rise rate, for example, 1°C or less in 60 seconds, it determines that boiling has been detected due to a change in the temperature rise rate of the lid temperature t2. When the rice cooking control means 51 detects boiling due to a change in the temperature rise rate of both the pot temperature t1 and the lid temperature t2, it proceeds to the next boiling continuation step. The predetermined temperature rise rates of the pot temperature t1 and lid temperature t2 used to detect boiling may be adjusted and set according to the amount of rice to be cooked determined in the capacity determination step. Furthermore, the boiling detection method is just one example, and the cooking control means 51 may be configured to proceed to the next boiling continuation step when it determines that boiling has been detected due to a change in the temperature rise rate of the pot temperature t1.

[0058] In this embodiment, during the boiling heating process, which raises the temperature of the food to be cooked to a boil in a short time, the cooking control means 51 controls the side coil 11-1 and bottom coil 11-2 with three different energizing patterns during the heating process until it detects boiling due to a change in the rate of temperature rise of the pot temperature t1 and boiling due to a change in the rate of temperature rise of the lid temperature t2. It also controls the side coil 11-1 and bottom coil 11-2 with a different energizing pattern during the stabilization #1 process, switching the energizing pattern of the heating coil 11 multiple times. As a result, the appropriate energizing pattern can be finely adjusted until the water in the food to be cooked boils, reducing the risk of uneven cooking of the rice. However, the present invention is not limited to this, and any configuration that controls the cooking control means 51 to switch the energizing pattern of the heating coil 11 at least once before the water in the food to be cooked boils during the boiling heating process is acceptable, such as switching the energizing pattern of the heating coil 11 when transitioning to the stabilization #1 process. Furthermore, the rice cooking control means 51 controls the bottom coil 11-2 and the side coil 11-1 with different energizing patterns depending on the amount of rice to be cooked, and by finely changing the appropriate energizing pattern according to the amount of rice to be cooked, it reduces the risk of uneven cooking of the rice.

[0059] When the process moves to the boiling continuation stage, the rice cooking control means 51 controls the power supply to the heating coil 11 based on the temperature detection signal from the pot sensor 12 until the pot temperature t1 reaches a predetermined temperature, and also controls the lid heater 33 to continuously supply power to maintain the lid temperature t2 at a predetermined temperature, such as 98°C or higher, based on the temperature detected by the lid temperature sensor 32, thereby starting the stabilization #2 stage, which is a stage in which the boiling state of the cooked food is maintained. In the stabilization #2 stage, the power supply pattern of the side coils 11-1 and bottom coils 11-2 when the heating coil 11 is driven has a longer cycle length than that of the stabilization #1 stage, so that the time during which the driving of the heating coil 11 is stopped, i.e., the OFF time of the heating coil 11 is longer.

[0060] Furthermore, once the boiling process begins, the rice cooking control means 51 periodically controls the power supply of the solenoid 35 to repeatedly change the pressure inside the pot 4 between normal pressure and a pressure higher than atmospheric pressure, thereby periodically opening and closing the steam discharge path 33 with the pressure regulating valve 34.

[0061] The rice cooking control means 51, when it determines that the water inside the pot 4 has started to disappear in the stable #2 stroke, and that the temperature at the bottom of the pot 4 has reached a predetermined temperature or has risen to a predetermined temperature increase rate, such as 0.5°C or more in 10 seconds, based on the temperature detected by the pot temperature sensor 15, starts the cooking process to detect that the rice is cooked.

[0062] When the cooking process begins, the rice cooking control means 51 controls the solenoid 35 to close the steam discharge path 33 with the pressure regulating valve 34. The rice cooking control means 51 also increases the energizing time Q seconds of the bottom coil 11-2 in one cycle compared to the energizing time O seconds of the bottom coil 11-2 in one cycle of the stabilization #2 process (Q>O), while setting the energizing time R seconds of the side coil 11-1 in one cycle to be less than or equal to the energizing time P seconds of the side coil 11-1 in one cycle of the stabilization #2 process (R≦P), and controls the cooking process with an energizing pattern that alternately energizes the side coil 11-1 and the bottom coil 11-2. Therefore, in the cooking process, the energizing time Q seconds of the bottom coil 11-2 in one cycle is set to be longer than the energizing time R seconds of the side coil 11-1. In the cooking process, there is almost no water in the pot 4 containing the rice being cooked, and no internal or external convection occurs. Therefore, by making the energizing time of the bottom coil 11-2 longer than that of the side coil 11-1, the water remaining at the bottom of the pot 4 can be heated more efficiently from the bottom side. Here, the energizing time of the bottom coil 11-2 is set to be longer in the order of extra-large ≥ large ≥ medium ≥ small in the amount of rice being cooked, as before. Similarly, the energizing time of the side coil 11-1 is also set to be longer in the order of extra-large ≥ large ≥ medium ≥ small in the amount of rice being cooked.

[0063] The rice cooking control means 51 receives a temperature detection signal from the pot sensor 12 indicating that the pot temperature t1 has reached a predetermined dry-up temperature, for example, 120°C, or calculates from the temperature detection signal from the pot sensor 12 that the rise in the pot temperature t1 has exceeded a predetermined temperature rise rate, for example, 0.5°C or more in 10 seconds. Upon receiving this signal, it determines that the water inside the pot 4 has evaporated and the rice to be cooked is complete, and proceeds to the next steaming step.

[0064] During the steaming process, the rice cooking control means 51 controls the lid heater 33 to continuously energize it based on the temperature detected by the lid temperature sensor 32, so that the lid temperature t2 maintains a predetermined temperature, thereby preventing condensation on the inner lid 24. At the same time, it controls the heating coil 11 by continuously switching the power on and off for a predetermined time to maintain a high temperature so that the rice inside the pot 4 does not burn, thereby managing the temperature at the bottom of the pot 4. In this steaming process as well, the heating coil 11 is driven and stopped to some extent, so the rice cooking control means 51 controls it with a power supply pattern that is almost the same as the power supply pattern of the cooking process, which has a shorter cycle length. The rice cooking control means 51 also controls the solenoid 35 to rotate the pressure regulating valve 34 to open the steam discharge path 33, so that the inside of the pot 4 is in communication with the outside of the main unit 1, and steam from the food being cooked is released to the outside of the main unit 1 through the steam outlet 15 via the steam discharge path 33. Furthermore, the display control means 53 controls the LED display unit 17 to turn off the "pressure" process LED display unit. When the rice cooking control means 51 receives a timing signal from the timing means 45 after a predetermined time has elapsed, the steaming process ends and the rice cooking process is completed, and the process moves to the warming process controlled by the warming control means 52.

[0065] In this embodiment, even after the rice cooking control means 51 detects boiling due to a change in the rate of temperature rise of the pot temperature t1 and boiling due to a change in the rate of temperature rise of the lid temperature t2, it switches the energizing pattern of the heating coil 11 during the cooking process and also switches the energizing pattern of the heating coil 11 during the steaming process. This allows the water to continue boiling to cook the rice, and even when a high temperature is maintained to prevent the rice from burning, the energizing pattern is finely adjusted to reduce the risk of uneven cooking of the rice. However, the present invention is not limited to this, and any configuration in which the rice cooking control means 51 switches the energizing pattern at least once even after the water to be cooked has boiled, such as switching the energizing pattern during the steaming process, is acceptable.

[0066] Next, the operation of the rice cooker with the above configuration during the warming process will be explained. Figure 7 shows the pot temperature t1, which is the temperature detected by the pot temperature sensor 12, and the output P of the bottom coil 11-2 during the warming process of the rice cooker of this embodiment. B And the output P of the side coil 11-1 S The changes in and over time are shown in the graphs.

[0067] In this embodiment, as shown in Figure 7, the heat retention process is subdivided into five periods T1 to T5, and the heat retention control means 52 controls the bottom coil 11-2, which is the coil used, with a different energizing pattern for each of these five periods T1 to T5. That is, each time a period T1 to T5 transitions, the heat retention control means 52 switches from the energizing pattern of the previous period to an energizing pattern that changes at least one of the energizing time, output, or non-energizing time of the bottom coil 11-2. However, the present invention is not limited to this, and the heat retention control means 52 may use one of a plurality of heating coils in the heat retention process, and instead of keeping the energizing pattern the same throughout the heat retention process, it may switch the energizing pattern at least once to control the coil used with two or more energizing patterns.

[0068] The heat retention process of this embodiment is comprised of the following periods: an initial heat retention period T1, which is a predetermined period of, for example, 30 minutes or less from the start of the heat retention process, or a period during which the temperature of the rice is, for example, 90°C or higher; a heat retention decrease period T2, which follows the initial heat retention period T1 and is a predetermined period of, for example, 60 minutes or less from the start of the heat retention process, during which the temperature of the rice is gradually lowered; a low-temperature stabilization period T3, which is more than 60 minutes from the start of the heat retention process, during which the temperature of the rice is maintained at a low-temperature heat retention temperature of, for example, 70°C ± 3°C, which is on the lower end of the heat retention temperature range that can suppress the Maillard reaction in the rice; a high-temperature decrease period T4, which is when the temperature of the rice is raised from the low-temperature heat retention set temperature to the high-temperature heat retention temperature; and a high-temperature stabilization period T5, which is on the higher end of the heat retention temperature range, for example, 73°C ± 3°C.

[0069] In this embodiment, during the heat retention process, the heat retention control means 52 outputs a heating control signal to the bottom coil drive means 47, controlling the bottom coil 11-2 to heat the pot 4 with a predetermined output, and controlling it with an energizing pattern that does not use the side coil 11-1 during the heat retention process. Therefore, the generation of mechanical noise from mechanical switches such as relays when switching between the side coil 11-1 and the bottom coil 11-2 is suppressed, thereby reducing noise during the heat retention process.

[0070] When the process transitions to the keep-warm stage, the keep-warm control means 52 calculates the temperature of the rice to be cooked based on the temperature t1 detected by the pot sensor 12, and controls the power supply of the bottom coil 11-2 to maintain the temperature of the pot 4, for example, by controlling the power supply to maintain the rice temperature at a predetermined temperature of 90°C or higher, thus entering the initial keep-warm period T1. The keep-warm control means 52 also controls the temperature of the inner lid 24 by controlling the power supply of the lid heater 22 based on the temperature detected by the lid temperature sensor 32, so that the temperature of the inner lid 24 on the surface facing the pot 4 is on average higher than the temperature of the rice in the pot 4. As a result, condensation on the surface of the inner lid 24 facing the pot 4 is prevented, preventing broth from dripping onto the rice, and maintaining a freshly cooked state and a taste equivalent to freshly cooked rice. The display control means 53 then controls the LED display unit 17 to light up the "keep warm" process LED display unit. When the heat retention control means 52 receives a timing signal from the timing means 45 indicating that a predetermined time, such as 30 minutes, has elapsed since the start of the initial heat retention phase T1, it transitions to the heat retention descent phase T2.

[0071] During the heat retention descent period T2, the heat retention control means 52 controls the bottom coil 11-2 based on the temperature t1 detected by the pot sensor 12 to manage the temperature of the pot 4, and after a predetermined time, such as 60 minutes from the start of the heat retention process, lowers the temperature of the rice inside the pot 4 to a low-temperature heat retention temperature of, for example, 70°C ± 3°C. At the same time, the heat retention control means 52 controls the lid heater 31 based on the temperature detected by the lid temperature sensor 32 to manage the temperature of the inner lid 24 and prevent condensation on the inner lid 24. In addition, during the heat retention descent period T2, the heat retention control means 52 may also control the solenoid 35 to close the steam discharge path 33 with the pressure regulating valve 34. After degassing in the steaming process of the rice cooking process, with communication between the inside and outside of the pot 4 blocked, the temperature of the rice being cooked is lowered from near the boiling point to the low-temperature heat retention temperature. As a result, the temperature of gases such as steam inside the pot 4 also drops and turns into liquids such as water, creating a reduced-pressure degassing state inside the pot 4. When the heat retention control means 52 determines that a predetermined time has elapsed since the start of the heat retention process and that the temperature of the rice inside the pot 4 has been lowered to the set temperature for low-temperature heat retention based on the temperature t1 detected by the pot sensor 12, it moves to the next low-temperature stabilization phase T3.

[0072] During the low-temperature stabilization period T3, the heat retention control means 52 controls the power supply to the bottom coil 11-2 to maintain the rice temperature at a low-temperature heat retention temperature of, for example, 70°C ± 3°C, based on the temperature t1 detected by the pot sensor 12, thereby managing the temperature of the pot 4 and suppressing deterioration of the heat retention state, such as yellowing of the rice inside the pot 4 or the emission of a distinctive odor. At the same time, the heat retention control means 52 controls the lid heater 31 based on the temperature detected by the lid temperature sensor 32 to manage the temperature of the inner lid 24 and prevent condensation on the inner lid 24. In addition, during the low-temperature stabilization period T3, the heat retention control means 52 may also control the solenoid 35 to close the steam discharge path 33 with the pressure regulating valve 34, thereby blocking communication between the inside and outside of the pot 4, preventing the entry of spoilage bacteria and food poisoning bacteria from the steam vent 17a, and also preventing the entry of cold air from the outside. Furthermore, if the inside of the pot 4 is in a reduced-pressure degassing state during the heat retention decline period T2, this reduced-pressure degassing state inside the pot 4 can be maintained. When the temperature control means 52 receives a timing signal from the timing means 45 indicating that a predetermined time, such as 6 hours, has elapsed since the start of the low-temperature stabilization period T3, it transitions to the next high-temperature descent period T4.

[0073] During the high-temperature descent phase T4, the heat retention control means 52 controls the power supply to the bottom coil 11-2 based on the temperature t1 detected by the pot sensor 12, thereby managing the temperature of the pot 4 by controlling the power supply to the bottom coil 11-2 so that the temperature of the rice is a predetermined temperature higher than the high-temperature retention temperature. At the same time, the heat retention control means 52 controls the lid heater 31 based on the temperature detected by the lid temperature sensor 32 to manage the temperature of the inner lid 24 and prevent condensation from forming on the inner lid 24. Subsequently, when the heat retention control means 52 determines, based on the temperature t1 detected by the pot sensor 12, that the temperature of the rice inside the pot 4 has risen to a predetermined temperature higher than the high-temperature retention temperature, it controls the bottom coil 11-2 and manages the temperature of the pot 4 based on the temperature t1 detected by the pot sensor 12 to lower the temperature of the rice inside the pot 4 to the high-temperature retention temperature. When the heat retention control means 52 determines that the temperature of the rice has dropped to the set temperature for high-temperature retention, it moves to the next high-temperature stabilization phase T5.

[0074] Furthermore, when the inside of the pot 4 is to be subjected to a reduced pressure and degassed state during the heat retention process, the heat retention control means 52 controls the power supply to the bottom coil 11-2 to be switched off during the high temperature descent period T4 so that the temperature of the rice becomes higher than the high temperature retention temperature, and controls the solenoid 35 to rotate the pressure regulating valve 34 to open the steam discharge path 33, thereby releasing the steam and air inside the pot 4 to the outside of the rice cooker and degassing it. Subsequently, when it is determined that the temperature of the rice inside the pot 4 has risen to a predetermined temperature above the high temperature retention temperature based on the temperature t1 detected by the pot sensor 12, the solenoid 35 may be controlled to close the steam discharge path 33 with the pressure regulating valve 34. After that, the inside of the pot 4 can be subjected to a reduced pressure and degassed state again in order to lower the temperature of the rice inside the pot 4 to the high temperature retention temperature.

[0075] During the high-temperature stabilization period T5, the heat retention control means 52 controls the power supply to the bottom coil 11-2 to maintain the rice temperature at a high-temperature heat retention temperature of, for example, 73°C ± 3°C, based on the temperature t1 detected by the pot sensor 12, thereby managing the temperature of the pot 4. At the same time, the heat retention control means 52 controls the lid heater 31 based on the temperature detected by the lid temperature sensor 32 to manage the temperature of the inner lid 24 and prevent condensation from forming on the inner lid 24. This suppresses the Maillard reaction in the rice and prevents condensation on the surface of the inner lid 24 facing the pot 4, thereby preventing broth from dripping onto the rice. During the high-temperature stabilization period T5, the heat retention control means 52 may also control the solenoid 35 to close the steam exhaust path 33 with the pressure regulating valve 34, thereby blocking communication between the inside and outside of the pot 4, preventing the entry of spoilage bacteria and food poisoning bacteria from the steam vent 17a, and also preventing the entry of cold air from the outside. Furthermore, if the inside of the pot 4 is in a depressurized state during the high-temperature descent period T4, this depressurized state inside the pot 4 can be maintained.

[0076] As described above, the rice cooker of this embodiment comprises a pot 4 for containing rice and water as the food to be cooked, a plurality of heating coils, side coils 11-1 and bottom coils 11-2, for heating the pot 4, and a heat retention control means 52 as a control means for controlling the side coils 11-1 and bottom coils 11-2. The heat retention control means 52 is configured to use one of the side coils 11-1 and bottom coils 11-2 and to control the heating of the pot 4 in two or more energizing patterns during the heat retention process, which is the process of keeping the food to be cooked warm.

[0077] By configuring it in this way, the generation of mechanical noise from mechanical switches such as relays when switching between the side coil 11-1 and the bottom coil 11-2 can be suppressed, thereby reducing noise generation during the heat retention process.

[0078] Furthermore, in the rice cooker of this embodiment, at least one of the side coils 11-1 and bottom coils 11-2 is a heating coil that heats the bottom of the pot, and the heat retention control means 52 is configured to control the heating of the pot 4 using the bottom coil 11-2 as a heating coil that heats the bottom of the pot 4 during the heat retention process. Since there is no water in the pot 4 containing the cooked rice during the heat retention process and no internal or external convection occurs, the cooked rice can be heated more efficiently by heating the pot 4 using the bottom coil 11-2.

[0079] Figure 8 shows a modified version of the rice cooker according to this embodiment. The figure shows the pot temperature t1, which is the temperature detected by the pot temperature sensor 12, and the output P of the bottom coil 11-2 during the warming process of this modified version. B And the output P of the side coil 11-1 S The changes in and over time are shown in the graphs.

[0080] In this modified example, during the low-temperature stable period T3 and high-temperature stable period T5, which are stable periods in the heat retention process where the temperature is maintained at the lower or higher end of the heat retention temperature range, the heat retention control means 52 outputs heating control signals to the side coil driving means 46 and the bottom coil driving means 47 to control the side coil 11-1 and the bottom coil 11-2 to heat the pot 4 at a predetermined output. Here, during the low-temperature stable period T3 and the high-temperature stable period T5, the heat retention control means 52 controls the heating coil 11 with an energizing pattern in which the bottom coil 11-2 is energized → switching time → the bottom coil 11-2 is energized → switching time → the side coil 11-1 is energized → switching time, turning the bottom coil 11-2 ON / OFF multiple times (twice in the example of Figure 8) before switching to the side coil 11-1 and turning it ON / OFF once. Therefore, by having the heat retention control means 52 control the side coil 11-1 and the bottom coil 11-2 with such a current supply pattern, the number of times the side coil 11-1 and the bottom coil 11-2 are switched is reduced, and the generation of mechanical noise from mechanical switches such as relays is suppressed, thereby suppressing noise generation during the heat retention process.

[0081] As described above, the rice cooker of this modified version comprises a pot 4 for containing rice and water as the food to be cooked, a plurality of heating coils, namely side coils 11-1 and bottom coil 11-2, for heating the pot 4, and a heat retention control means 52 as a control means for controlling the side coils 11-1 and bottom coil 11-2. The heat retention control means 52 controls the heating of the pot 4 in an energizing pattern that switches the bottom coil 11-2, as one coil, ON / OFF multiple times before switching to the other coil, namely the side coil 11-1, during the low-temperature stable period T3 and high-temperature stable period T5, which are stable periods that maintain the temperature to be kept warm at a temperature on the low-temperature or high-temperature side of a predetermined temperature range. This reduces the switching frequency of the side coils 11-1 and bottom coil 11-2, thereby suppressing the generation of mechanical noise from mechanical switches such as relays when switching between the side coils 11-1 and bottom coil 11-2, and thus suppressing noise generation during the heat retention process.

[0082] Furthermore, in this modified rice cooker, the period during which the pot 4 is heated by an energizing pattern in which the bottom coil 11-2, which is one coil, is turned ON / OFF multiple times before switching to the side coil 11-1, which is another coil, is the low-temperature stable period T3 and the high-temperature stable period T5 in the warming process, which are stable periods in which the temperature is maintained at the low or high temperature side of the predetermined warming temperature range. Therefore, the frequency of switching between the side coil 11-1 and the bottom coil 11-2 is reduced during the period in which the temperature is maintained at the predetermined temperature range, thereby suppressing the generation of mechanical noise from mechanical switches such as relays when switching between the side coil 11-1 and the bottom coil 11-2, and thus suppressing noise generation.

[0083] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. Furthermore, the numerical values ​​and other figures exemplified in the embodiments are merely examples and may be appropriately changed depending on the specifications of the rice cooker, etc. [Explanation of Symbols]

[0084] 4 Pot 11-1 Side coil (heating coil) 11-2 Bottom coil (heating coil) 52 Heat retention control means (control means) T 1 Initial period of insulation (at least for periods other than certain periods) T 2 Thermal depression period (at least the period other than certain periods) T3 low-temperature stable phase (stable phase) T 4 High temperature fall period (at least the period other than certain periods) T5 high temperature stability period (stable period)

Claims

1. A pot for holding the food to be cooked, Multiple heating coils for heating the aforementioned pot, The system includes control means for controlling the plurality of heating coils, The control means is In the rice cooking process, which is the process of cooking the food to be cooked, all of the multiple heating coils are used alternately. In the heat-keeping step, which is the step of keeping the cooked food warm, only one of the plurality of heating coils is used, The heat retention process includes a plurality of periods of changing the temperature of the cooked food and a plurality of periods of maintaining the temperature of the cooked food, and these plurality of periods of changing the temperature of the cooked food and the periods of maintaining the temperature of the cooked food are performed alternately. The control means, in the heat retention process, at the timing when the period transitions, A rice cooker characterized by controlling the heating of the pot by switching the energizing pattern by changing at least one of the energizing time, output, or non-energizing time of one of the coils used.

2. The rice cooker according to claim 1, wherein at least one of the plurality of heating coils is a heating coil for heating the bottom of the pot, and the control means controls the heating of the pot using the heating coil for heating the bottom of the pot during the heat retention process.

3. A pot for holding the food to be cooked, Multiple heating coils for heating the aforementioned pot, The system includes control means for controlling the plurality of heating coils, The control means is In the rice cooking process, which is the process of cooking the food to be cooked, all of the multiple heating coils are used alternately. The heat-keeping process, which is a process of keeping the cooked food warm, includes a plurality of periods of changing the temperature of the cooked food and a plurality of periods of maintaining the temperature of the cooked food, and these plurality of periods of changing the temperature of the cooked food and the period of maintaining the temperature of the cooked food are performed alternately. The control means heats the pot in an energizing pattern that, during at least a portion of the period in the heat retention process, switches one heating coil ON / OFF two or more times before switching to another heating coil. During the period other than the period of at least a portion of the heat retention process, only one of the plurality of heating coils is used, At the timing when the aforementioned period transitions to a period other than at least a portion of the aforementioned period, A rice cooker characterized by controlling the heating of the pot by switching the energizing pattern by changing at least one of the energizing time, output, or non-energizing time of one of the coils used.

4. The rice cooker according to claim 3, characterized in that at least a portion of the aforementioned period is a stable period in which the temperature is maintained at the lower or higher end of a predetermined temperature range during the heat retention process.

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