JP7760766B2 - rice cooker - Google Patents

Description

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

When cooking rice over a firewood flame in a hearth, the flame fluctuates, subtly changing the heat intensity and heating the bottom and sides of the pot containing the food.

Technologies aimed at approximating this traditional stove-top cooking include, for example, Patent Documents 1 and 2, which arrange three independent induction heating (IH) coils from the bottom to the sides of the pot, and heat by turning electricity on and off in a rotating sequence; Patent Documents 3, 4, and 5, which arrange independent coils at different heights on the bottom and sides of the pot, and heat by alternately turning electricity on and off; Patent Documents 6 and 7, which arrange induction heating coils from the bottom to the sides of the pot, and heat by gradually changing the amount of heat from the coils over time; and Patent Documents 8 and 9, which arrange induction heating coils from the bottom to the sides of the pot, and heat by continuously changing the amount of heat from the coils over time.

Japanese Patent Application Laid-Open No. 2019-162250 Japanese Patent Application Laid-Open No. 2019-180533 Japanese Patent Application Publication No. 9-248242 JP 2011-206142 A Japanese Patent Application Publication No. 5-337042 JP 2013-247972 A Japanese Patent Application Laid-Open No. 2008-220470 Japanese Patent Application Publication No. 11-214139 Japanese Patent Application Laid-Open No. 2020-4540

The above-mentioned conventional technology promotes water convection within the pot during cooking, allowing the rice to be heated with an even distribution of water, resulting in uniform gelatinization of the rice throughout the pot. This is thought to be based on the key points for beautifully cooking rice seen in traditional kamado (traditional Japanese hearth) cooking. However, with kamado rice cooking, the wood fire that serves as the heat source is located away from the pot, and indirect heating occurs with an air layer in between, causing the amount of heat reaching the pot to fluctuate. In contrast, with the above-mentioned induction rice cooker, the pot generates heat, so there is no space between the heat source and the pot, and the heating method itself is different.

Aside from induction rice cookers, there are also hot plate heaters that heat a hot plate that comes into contact with the bottom of the pot, radiant heaters that heat the pot with a heater spaced apart, and indirect rice cookers that cook rice by placing water between the pot and the outer pot, but none of these have been able to produce a fluctuating amount of heat in the pot like a kamado rice cooker.

The present invention aims to provide a rice cooker that can cook rice with heating similar to that of a traditional Japanese stove.

To achieve the above-mentioned objectives, the rice cooker of the present invention comprises a pot for containing food to be cooked, a heating means for heating the pot, a rice cooking control means for changing the amount of heat from the heating means as the process progresses to cook the food, and a heat amount variable means for changing the amount of heat from the heating means over time. The processes include a soaking process, a heating process until boiling, a heating process while boiling continues, and a steaming process. The heat amount variable means changes the amount of heat from the heating means so as to periodically repeat an upper limit of the amount of heat, a lower limit of the amount of heat, and one or more heat amount values between the upper limit and the lower limit during at least two of the soaking process, the heating process until boiling, the heating process while boiling continues, and the steaming process. The upper limit and the lower limit, and the length of the cycle, are different, and the duration for which one heat amount is maintained during each cycle varies depending on the length of the cycle.

The rice cooker of the present invention allows rice to be cooked using heat similar to that of a traditional Japanese stove.

1 is a schematic explanatory diagram of a rice cooker showing one embodiment of the present invention. FIG. 2 is a block diagram showing the electrical configuration of the rice cooker. 10 is a graph showing the change over time in the temperature of the bottom of the pot, the temperature of the underside of the lid, and the amount of heat from the bottom heater. 10A and 10B are graphs showing the change over time in the amount of heat supplied to the pot by the rice cooking control means and the change over time in the amount of heat supplied to the pot by the heat amount fluctuation means, respectively. 10 is a graph showing the change over time in the amount of heat applied to the pot by the heat amount fluctuation means. 10 is a graph showing the change in temperature of each part over time during the boiling heating process. 10 is a graph showing the change in temperature of each part over time during the boiling heating process. 10 is a graph showing the change in temperature of each part over time during the boiling heating process. 10 is a graph showing the relationship between the amount of heat and time when heated over high heat. 10 is a graph showing the relationship between the amount of heat and time at medium heat. 10 is a graph showing the relationship between the amount of heat and time on low heat.

A preferred embodiment of a rice cooker according to the present invention will be described below with reference to the accompanying drawings. Note that common parts will be designated by common reference numerals throughout these drawings.

First, referring to Figure 1, the overall structure of the rice cooker of this embodiment will be described. 1 denotes a main body with an open top, and 2 denotes an openable lid that covers the open top of the main body 1. The main body 1 and lid 2 together form the exterior of the rice cooker. On the front of the main body 1 is a display/operation unit 5 that combines a display unit 3 such as an LED or LCD (display) described below, and an operation unit 4 such as operation keys or a touch panel. The display/operation unit 5 may also be disposed on the lid 2 instead of the main body 1.

Inside the main body 1, a detachable, cylindrical pot 7 with a bottom is provided, containing rice and water as the food to be cooked A. When the lid 2 is opened, the pot 7 can be inserted and removed through the top opening of the main body 1. When the pot 7 is placed in the main body 1 and the lid 2 is closed, the inner lid 8 attached to the underside of the lid 2 closes the top of the opening of the pot 7, forming an internal pot space 9 within the main body 1 and the pot 7, surrounded by the inner surface of the pot 7, the top surface of the food to be cooked A, and the underside of the inner lid 8. Although not shown, the pot 7 is primarily made of aluminum, which has good thermal conductivity, and a heating element made of a magnetic material such as ferritic stainless steel is joined to the outer surface of the main material, from the lower side to the bottom.

Inside the main body 1 and outside the pot 7, a bottom heating element 11 using a heating coil and a side heating element 12 using a cord heater are arranged as heating means for heating the pot 7 to cook the food A to be cooked. The bottom heating element 11, which serves as the main heating means for the pot 7, is positioned facing the bottom of the pot 7 from the lower side where the heating element is located. As a result, when the bottom heating element 11 is energized, the alternating magnetic field from the bottom heating element 11 generates heat in the heating element of the pot 7, raising the temperature of the pot 7 and heating the food A to be cooked. The side heating element 12, which serves as auxiliary heating means for the pot 7, is positioned facing the upper side of the pot 7. When the side heating element 12 is energized, radiant heat from the side heating element 12 heats mainly the upper side of the pot 7. The side heater 12 may be configured with a heating coil, similar to the bottom heater 11, and the upper side of the pot 7 may be heated by electromagnetic induction in addition to the lower side and bottom portions of the pot 7. The pot 7 may also be heated by a heating method other than electromagnetic induction.

Also located inside the main body 1 is a thermistor-type pot temperature sensor 15 that abuts against the outer surface of the bottom of the pot 7. The pot temperature sensor 15, which serves as a pot temperature detection means, detects the temperature of the bottom of the pot 7 and primarily controls the heating temperature of the bottom of the pot 7 by the bottom heater 11.

When cooking rice or keeping it warm, the pot 7 is heated by a heating means. When keeping it warm, the bottom heater 11 is heated and adjusted according to the temperature detected by the pot temperature sensor 15 in contact with the outer bottom surface of the pot 7, maintaining the pot 7 at a constant temperature. After cooking, the side heater 12, which serves as the heat generating means, generates heat until the temperature of the rice in the pot 7 drops to the keeping-warm temperature (from approximately 100°C to approximately 73°C) and when keeping the rice warm is stable (approximately 73°C). This prevents cooling caused by outside air entering through the gap between the main body 1 and the lid 2 and heats mainly the upper side of the pot 7. Furthermore, when keeping the rice warm, the pot 7 is heated even during the hot reheating process, which reheats the rice in the pot 7, preventing moisture generated by heating from condensing on the upper inner surface of the pot 7.

The lid 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 and, by extension, the pot interior space 9; 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 lid heater 18 primarily control the temperature of the inner lid 8 using the lid heating means 23. When the inner lid 8 is attached to the lid 2, the lid temperature sensor 16 comes into contact with the top surface of the inner lid 8, and the lid heater 18 is positioned opposite the top surface of the inner lid 8. The lid heater 18 may be constructed of a heating coil and the inner lid 8 may be constructed of a magnetic material, allowing the inner lid 8 to be heated by electromagnetic induction.

A pressure adjustment valve 20 including a ball-shaped valve element 19 is located approximately in the center of the inner lid 8, which forms the underside of the lid 2. The pressure adjustment valve 20 is located midway through the steam passage space that connects the pot interior space 9 with the lid 2 and ultimately the outside of the rice cooker (outside the machine). A movable mechanism (not shown), such as a solenoid, is provided inside the lid 2 to move the valve element 19 forward or backward toward or away from the pressure adjustment valve 20. When the valve element 19 advances into the pressure adjustment valve 20 and blocks the steam passage space, the pot interior space 9 can be pressurized above atmospheric pressure until the pressure in the pot interior space 9 increases as the pot 7 is heated, pushing up the valve element. When the valve element 19 retracts from the pressure adjustment valve 20 and opens the steam passage space, the pot interior space 9 can be maintained at atmospheric pressure regardless of how much the pot 7 is heated. The pressure sensor 17 is located inside the lid 2 facing the pressure adjustment valve 20, but it can be located elsewhere as long as it can detect the pressure in the pot interior space 9.

Figure 2 shows the electrical configuration of the rice cooker in this embodiment. In the figure, reference numeral 31 denotes a control unit incorporated inside the main body 1 or lid 2, and comprising a microcomputer and drive elements for each component. The input port of the control unit 31 is electrically connected to the operation unit 4, pot temperature sensor 15, lid temperature sensor 16, and pressure sensor 17. The output port of the control unit 31 is electrically connected to the display unit 3, a first heating drive unit 32 connected to the bottom heater 11, a second heating drive unit 33 connected to the side heater 12, and a third heating drive unit 34 connected to the lid heater 18. The control unit 31 incorporates storage means 35, such as a readable and writable memory, for storing various information and data.

The control unit 31 receives operation signals from the operation unit 4 and detection signals from the pot temperature sensor 15, lid temperature sensor 16, and pressure sensor 17, and outputs display control signals to the display unit 3 at predetermined timing based on the timing of the built-in timing means (not shown). It also outputs heating control signals to the first heating drive unit 32, second heating drive unit 33, and third heating drive unit 34. These functions are realized by the control unit 31 reading programs pre-recorded in the storage means 35, which serves as a storage medium. In this embodiment, the control unit 31 is equipped with programs that primarily function as rice cooking control means 41, which heats the rice and water (food A) in the pot 7 to cook rice during cooking, and as warming control means 42, which maintains the rice in the pot 7 at a predetermined warm temperature during keeping warm.

The first heating drive unit 32 mainly comprises a power supply circuit 36, an inverter 37, and an IH drive circuit 38. The power supply circuit 36 corresponds to a rectifying and smoothing circuit that converts the commercial power supply voltage, for example, 100V AC, supplied to the main body 1 into DC voltage, and the DC voltage from the power supply circuit 36 is applied as input voltage to the inverter 37. Although neither is shown, the inverter 37 is a well-known voltage-type resonant inverter that includes a resonant capacitor connected in parallel with the heating coil that serves as the bottom heater 11 to form a resonant circuit, and a switching element such as an IGBT connected in series with the resonant circuit. The IH drive circuit 38 receives a first heating control signal from the control unit 31 and sends a pulse drive signal to the gate of the switching element of the inverter 37 that is sufficient to turn the switching element on and off. As a result, when a pulse drive signal is sent from the IH drive circuit 38 to the gate of the switch element, the emitter-collector of the switch element is repeatedly switched on and off, the power supply voltage from the power supply circuit 36 is intermittently applied to the resonant circuit of the inverter 37, and high-frequency current is supplied to the bottom surface heater 11. By changing the period of the pulse drive signal and the ratio of on time to one period (on time ratio), the output power (output) from the inverter 37, and therefore the amount of heat from the bottom surface heater 11 to the pot 7, can be increased or decreased.

The second heating drive unit 33 receives a second heating control signal from the control unit 31 and supplies the commercial power supply voltage to the power supply circuit 36 to the cord heater that serves as the side heater 12. Similarly, the third heating drive unit 34 receives a third heating control signal from the control unit 31 and supplies the commercial power supply voltage to the power supply circuit 36 to the cord heater that serves as the lid heater 18. The control unit 31 also has the function of sending a separate control signal to the drive unit of the solenoid that operates the valve body 19, for example, to turn the solenoid on and off. However, since this is not particularly relevant to this embodiment, further explanation and illustration will be omitted.

Upon receiving an instruction to start cooking rice via the operating unit 4, the rice cooking control means 41 sequentially carries out the following steps: soaking, which promotes the absorption of water by the rice in the food item A placed in the pot 7; boiling, which quickly raises the temperature of the food item A to a boil and then continues the boiling state of the food item A until it is in a water-free, dried-up state; and steaming, which maintains the dried-up food item A at a high temperature that does not burn it, until it is cooked into rice, thereby cooking the food item A placed in the pot 7 at the desired pressure. In this embodiment, for all cooking modes available for rice cooking using the rice cooker, a first pattern is stored in advance in the memory means 35, which indicates how the display unit 3, bottom heating element 11, side heating element 12, and lid heating element 18 are operated as the rice cooker progresses through each cooking step, from the aforementioned soaking cooking to steaming, thereby changing the amount of heat applied to the food A in the pot 7 from the bottom heating element 11, side heating element 12, and lid heating element 18. After the user operates the operation unit 4 to select a desired cooking mode from multiple cooking modes and then issues a command to start cooking, the rice cooking control means 41 reads the first pattern corresponding to the selected cooking mode from the memory means 35, and appropriately controls the display unit 3, bottom heating element 11, side heating element 12, and lid heating element 18 to cook the food A placed in the pot 7 while displaying the information on the display unit 3.

In this embodiment, it is noteworthy that the control unit 31 is equipped with a heat amount fluctuation means 44, which serves as a heat amount variation means. When the rice cooking control means 41 operates the bottom heating element 11, side heating element 12, and 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 varies the amount of heat provided to the food A in the pot 7 from the bottom heating element 11, side heating element 12, and lid heating element 18 over time based on this second pattern. The heat amount fluctuation means 44 will be explained in more detail later.

The keep-warm control means 42 controls the rice in the pot 7 to maintain a predetermined keep-warm temperature according to the first pattern corresponding to the selected cooking course. Regardless of the selected cooking course, once the cooking and heating of the food item A by the rice cooking control means 41 is completed, the keep-warm control means 42 automatically starts keeping the rice warm. The keep-warm control means 42 also has a keep-warm reheating function that controls the operation of the bottom heater 11 so that the temperature of the rice in the pot 7 temporarily rises above the keep-warm temperature when a reheating command is issued via the operation unit 4 during keep-warm operation. Furthermore, even if the main unit 1 is in the off state immediately after commercial power is applied and a command to start keep-warm is issued via the operation unit 4, the keep-warm control means 42 can keep the food item A placed in the pot 7 warm.

Next, we will explain in detail the operational features of the rice cooker configured as described above, particularly those related to the heat amount fluctuation means 44. For the sake of convenience, from here on, we will use the bottom heating element 11, which is a heating coil, as the representative heating element, and only discuss the heat amount of the bottom heating element 11.

The rice cooker of this embodiment comprises a pot 7 that contains the food item A to be cooked, a bottom heating element 11 as a heating means for heating the pot 7, a rice cooking control element 41 that cooks the food item A by varying the amount of heat from the bottom heating element 11 based on a first pattern read from the memory element 35 as each cooking step progresses, and a heat amount fluctuation element 44 that varies the amount of heat from the bottom heating element 11 over time using a second pattern different from the first pattern when the rice cooking control element 41 is controlling the operation of the bottom heating element 11 to heat the pot 7.

Figure 3 shows graphs of the pot bottom temperature Tn, which corresponds to the temperature of the bottom of the pot 7 detected by the pot temperature sensor 15, the lid temperature Tf, which corresponds to the temperature of the underside of the lid 2 detected by the lid temperature sensor 16, and the change over time in the heat output S of the bottom heater 11 in the rice cooker of this embodiment.

In the diagram, when rice cooking control means 41 receives an operation signal from operation unit 4 and starts cooking, it sequentially performs the following processes: "soaking," which promotes the absorption of water by the rice placed in pot 7; "boiling heating," which boils the water in pot 7 and continues boiling; and "soaking," which detects the rice is cooked when the rice in pot 7 absorbs water, the water is gone, and the pot bottom temperature Tn exceeds the boiling temperature (100°C), and then maintains the temperature in pot 7 at a high temperature for a predetermined period of time, such as 15 minutes. In addition, heat retention control means 42 varies the amount of heat S from bottom heater 11 to pot 7 over time based on the first pattern, which serves as the reference control pattern read from memory means 35, so that after the predetermined period of "soaking" is completed, it executes the "keep warm" process, which maintains the cooked rice in pot 7 at a predetermined temperature, such as 73°C.

During this series of rice cooking processes, from "soaking" to "keeping warm," the rice cooking control means 41 and the keep-warm control means 42 adjust the amount of heat S of the bottom heater 11 and the timing of power on/off, which determines the intermittent heating, to cook the food A in the pot 7. This control configuration is the same as that of conventional rice cookers and is well known.

Meanwhile, the heat amount fluctuation means 44, which is the focus of the invention in this embodiment, responds to changes in the amount of heat supplied to the pot 7 over time by the rice cooking control means 41, which follows the traditional cooking technique of "start by trickling, then by fizzing, turn off the heat when it starts to sizzle, burn a handful of straw, and don't take the lid off even if the baby cries" by increasing or decreasing the amount of heat supplied to the pot 7 by induction heating every 100 ms (0.1 seconds) to 1 second (1 second) over a 1- to 10-second cycle, thereby generating a second pattern in which the output of the inverter 37, which corresponds to the amount of heat supplied to the bottom heater 11, varies by, for example, approximately 200 W overall. A heating configuration that anticipates the fluctuations of a wood-fired flame is then added, so that the amount of heat supplied to the pot 7 from the bottom heater 11 based on this second pattern is provided.

That is, "First trickle" produces a gentle flame over low heat during heating in the "soaking" process; "Chu pappa" produces a strong flame over high heat during heating until boiling in the "heating to a boil" process; "Turn off the heat when it starts to sizzle" produces a gentle flame over medium heat while boiling continues in the "heating to a boil" process until the rice is cooked to perfection; and "Burn a handful of straw, don't take the lid off even if the baby cries" produces a gentle flame over low heat during double cooking during the "soaking" process. The fluctuations in the amount of heat S2 supplied to the pot 7 by the heat amount fluctuation means 44 as shown in Figure 4(B) are added to the changes in the amount of heat S1 supplied to the pot 7 as the process progresses by the conventional rice cooking control means 41 as shown in Figure 4(A). The heat amount fluctuation means 44 sets the output maintenance time D, during which the output of the inverter 37 is kept constant, to a range of 0.1 to 1 second within a cycle (period) C of 1 to 10 seconds, and gradually increases or decreases the output of the inverter 37 for each output maintenance time D, generating a second pattern in which the output change amount E, which is the difference between the upper and lower limit values of the inverter 37 output, changes by approximately 200 W. This second pattern imparts a fluctuating change in heat amount S2 from the bottom heating element 11 to the pot 7. As a result, the final heat amount S to the pot 7 shown in Figure 3 is the sum of the heat amount S1 changed by the rice cooking control means 41 and the heat amount S2 fluctuating as changed by the heat amount fluctuation means 44.

To achieve a gentle flame over low heat during the "soaking" process, the heat amount fluctuation means 44 changes the inverter 37 output from 500W (lower limit) → 540W → 580W → 620W → 660W → 700W (upper limit) → 660W → 620W → 580W → 540W → back to 500W (lower limit), with one cycle C. For a gentle flame, one cycle C is set to 7 seconds, and the output maintenance time D during which each output is kept constant is set to 0.7 seconds. This allows the bottom heater 11 to repeatedly apply a cycle of varying heat amount S2 to the pot 7, varying the inverter 37 output every 0.7 seconds.

In addition, to achieve a high heat and intense flame when heating to boiling in the "heating to boil" process, the heat amount fluctuation means 44 is configured so that for high heat, the inverter 37 output is changed from 1200W (lower limit) → 1240W → 1280W → 1320W → 1360W → 1400W (upper limit) → 1360W → 1320W → 1280W → 1240W → back to 1200W (lower limit), with one cycle C being used. For intense flames, one cycle C is set to a minimum of 1 second, and the output maintenance time D during which each output is kept constant is set to a minimum of 0.1 seconds. This allows the bottom heater 11 to repeatedly apply to the pot 7 a cycle of varying heat amount S2 such that the inverter 37 output varies in steps every 0.1 seconds.

In addition, to achieve a gentle flame at medium heat while boiling continues in the "boiling heating" process until the rice is cooked, the heat amount fluctuation means 44 changes the inverter 37 output from 800W (lower limit) → 840W → 880W → 920W → 960W → 1000W (upper limit) → 960W → 920W → 880W → 840W → back to 800W (lower limit) in one cycle C for medium heat, and for a gentle flame, one cycle C is set to 4 seconds, and the output maintenance time D during which each output is kept constant is set to 0.4 seconds, so that the bottom heater 11 repeatedly applies to the pot 7 a cycle of varying the heat amount S2 such that the inverter 37 output varies in stages every 0.4 seconds.

Furthermore, to achieve a quiet flame at low heat during the soaking process and the double cooking during soaking, the heat amount fluctuation means 44 is configured so that for low heat, one cycle C is the inverter 37 output, changing from 500W (lower limit) → 540W → 580W → 620W → 660W → 700W (upper limit) → 660W → 620W → 580W → 540W → back to 500W (lower limit). For a quiet flame, one cycle C is set to a maximum of 10 seconds, and the output maintenance time D during which each output is kept constant is set to a maximum of 1 second. This allows the bottom heating element 11 to repeatedly apply a cycle of change in heat amount S2 to the pot 7, varying the inverter 37 output in stages every second.

Note that Figure 4(B) shows the fluctuations of three heat amounts S2 applied to the pot 7 as a representative example, but the heat amount S2 and its fluctuation pattern produced by the heat amount fluctuation means 44 are not limited to those shown in this embodiment.

In this embodiment, while the rice cooking control means 41 heats the pot 7 using the first pattern, the heat amount fluctuation means 44 varies the heat amount S2 to the pot 7 over time using a second pattern different from the first pattern. This makes it possible to cook the food A in the pot 7 using heating similar to that of a stove, where the flames flicker over a wood fire.

As shown in Figure 5, 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 element 11, which serves as a heating means, in a second pattern in which the heating amount S1 according to the first pattern executed by the rice cooking control means 41 is set as a reference value S1ave, and the heating amount S of the bottom heating element 11, which serves as a heating means, is varied in a second pattern in which an upper limit value S2max of the heating amount S2 that is greater than the reference value S1ave and a lower limit value S2min of the heating amount S2 that is smaller than the reference value S1ave are periodically repeated.

For example, at the high heat setting described above, the heating amount fluctuation means 44 changes the output of the inverter 37 from 1200W → 1240W → 1280W → 1320W → 1360W → 1400W → 1360W → 1320W → 1280W → 1240W → back to 1200W, during one cycle C, the upper limit value S2max of the heating amount S2 is set to 1400W and the lower limit value S2min of the heating amount S2 is set to 1200W, and the upper limit value S2max and lower limit value S2min of the heating amount S2 are changed periodically and repeatedly. In this case, the average heating amount S2 is 1300 W, but by making this 1300 W heating amount S2 correspond to the heating amount S1 by the conventional rice cooking control means 41 as the reference value S1ave, it is possible to prevent the food A in the pot 7 from being overcooked or undercooked, even when taking into account fluctuations in the heating amount S2 by the heating amount fluctuation means 44.

In this case, the heating amount fluctuation means 44 may be configured so that the output of the inverter 37 does not include the intermediate heating amount between the upper limit value S2max and the lower limit value S2min, but instead changes in one cycle C, for example, from 1200W to 1400W and back to 1200W on high heat. In this case, the heating amount fluctuation means 44 matches the average heating amount S2 of 1300W with the heating amount S1 by the conventional rice cooking control means 41, thereby achieving the same effect of eliminating overheating and underheating.

In this embodiment, the rice cooking amount fluctuation means 44 varies the amount of heat S2 supplied to the pot 7 so that the amount of heat S1 supplied by the first pattern executed by the rice cooking control means 41 is set as an average reference value S1ave, and periodically alternates between an upper limit value S2max higher than the reference value S1ave and an upper limit value S2max lower than the reference value S1ave. This makes it possible to cook the food A in the pot 7 with heating similar to that of a stove, where the flames flicker over a wood fire, while maintaining the average amount of heat S1 of a conventional rice cooker.

The heat amount fluctuation means 44, which serves as a heat amount varying means, is configured to vary the heat amount S of the bottom surface heater 11, which serves as the heating means, so as to periodically repeat the aforementioned upper limit value S2max, lower limit value S2min, and one or more intermediate values therebetween.

For example, in the medium heat setting described above, during one cycle C in which the heating amount fluctuation means 44 changes the inverter 37 output from 800W → 840W → 880W → 920W → 960W → 1000W → 960W → 920W → 880W → 840W → back to 800W, the upper limit S2max of the heating amount S2 is set to 1000W, the lower limit S2min of the heating amount S2 is set to 800W, and intermediate values of the heating amount S2 between these are set to 840W, 880W, 920W, and 960W, respectively. In addition to the upper limit S2max and lower limit S2min, multiple intermediate values are also periodically and repeatedly changed. In this case, there may be any number of intermediate values for the heating amount S2 of the bottom surface heater 11, and it may be set to just one, for example, 900W.

In the above example, the cycle of change in the heating amount S2 by the heating amount fluctuation means 44 is set as follows: for an intense flame, one cycle C is 1 second; for a gentle flame, one cycle C is 4 seconds; for a soft flame, one cycle C is 7 seconds; and for a quiet flame, one cycle C is 10 seconds. For example, in order to achieve a medium heat and gentle flame during the "boiling heating" process while boiling continues until the rice is cooked, one cycle C is set to 4 seconds, and the output maintenance time D for each cycle is set to 0.4 seconds. However, when the output is 1000 W, which is the upper limit value S2max of the heating amount S2, one cycle C corresponding to an intense flame is set to 1 second, and the output maintenance time D can be set to 0.1 seconds. When the output is 920 W, which is the intermediate value of the heating amount S2, one cycle C corresponding to a soft flame is set to 10 seconds, and the output maintenance time D can be set to 1 second. The output maintenance time D does not have to be constant for all outputs during a cycle, but can be changed arbitrarily for each output.

As another example, in the low heat setting described above, during one cycle C in which the heating amount fluctuation means 44 changes the output of the inverter 37 from 500W → 540W → 580W → 620W → 660W → 700W → 660W → 620W → 580W → 540W → back to 500W, the upper limit value S2max of the heating amount S2 is set to 700W, the lower limit value S2min of the heating amount S2 is set to 500W, and intermediate values of the heating amount S2 between these values are set to 540W, 580W, 620W, and 660W, respectively, and in addition to the upper limit value S2max and the lower limit value S2min, multiple intermediate values are changed periodically and repeatedly. In this case, too, there may be any number of intermediate values for the heat amount S2 of the bottom heater 11, and the heat amount S2 may be increased or decreased in increments of 20 W or 50 W between 500 W and 700 W rather than in increments of 40 W, allowing the value of each output to be set arbitrarily. Furthermore, here, the output change amount E, which is the difference between the upper limit S2max (= 700 W) and the lower limit S2min (= 500 W) of the heat amount S2, is set to 200 W, but it may also be 100 W or 300 W, and the value of the output change amount E may be set arbitrarily.

In this embodiment, when the heat amount fluctuation means 44 varies the heat amount S2 to the pot 7 over time in the second pattern, one or more intermediate heat amount S2 values are added in addition to the upper limit S2max and lower limit S2min of the heat amount S2, making it possible to cook the food A in the pot 7 using heating that is closer to the flickering flames of a wood fire.

In this embodiment, the heat amount fluctuation means 44 is configured to vary the heat amount S2 of the bottom heater 11 over time by varying the upper limit value S2max, the lower limit value S2min, and one or more intermediate values of the heat amount S2 in an irregular pattern, or by mixing irregular patterns with regular patterns.

"Fluctuation" refers to unpredictable spatial or temporal changes or movements, and "unpredictable" means that there is no regularity. In other words, "fluctuation" refers to irregular spatial or temporal changes or movements. For example, not only the movement of the wind or the flow of a river, but also the flames of a wood fire are included in the category of "fluctuation," which is an irregular pattern. It is well known that even things that appear constant are not stable and cannot be predicted.

It is also well known that fluctuations in which irregular patterns are mixed within regular patterns are called "1/f fluctuations," and the degree of fluctuation is expressed by the frequency "f," and the type of fluctuation is expressed as "1/√f,""1/f,""1/f ² ,""1/f ³ ," etc.

In the above example, the heat amount fluctuation means 44 was described as periodically repeating the time-dependent change in the heat amount S2 corresponding to a preset fluctuation for each cycle C. However, it may also be configured to irregularly change the fluctuation pattern by changing the fluctuation pattern corresponding to the second pattern consisting of the values of the heat amount S2 (upper limit value S2max, upper limit value S2max, intermediate value) and time elements (cycle C, output maintenance time D) from a predetermined setting, triggered by, for example, a change in the cooking state that changes as the pot 7 is heated in response to the temperature detected by the pot temperature sensor 15, the temperature detected by the lid temperature sensor 16, or the pressure detected by the pressure sensor 17.

Specific examples will be described below with reference to Figures 6 to 8. Figure 6 is a graph showing the temperature changes over time in various parts of the pot 7 during the boiling heating process in the rice cooker of this embodiment. In the figure, Tn indicates the change in the pot bottom temperature, which is the temperature detected by the pot temperature sensor 15; Ts indicates the temperature change inside the pot 7; Tf(A) indicates the change in the lid temperature, which is the temperature detected by the lid temperature sensor 16 under normal conditions; Tf(B) indicates the change in the lid temperature when the temperature rise in the upper part of the pot 7 is faster than that in the lower part; Tf(C) indicates the change in the lid temperature when the temperature rise in the upper part of the pot 7 is slower than that in the lower part; (d) indicates boiling detection due to changes in the rate of temperature rise of the lid temperature Tf; (e) indicates boiling detection due to changes in the rate of temperature rise of the pot bottom temperature Tn; and (H) indicates heating adjustment until boiling.

When the rice cooking control means 41 controls the process to boil and heat the pot 7 at high heat with the heat amount S of the bottom heater 11, which produces the intense flame described above, the pot bottom temperature Tn measured by the pot temperature sensor 15 and the lid temperature Tf measured by the lid temperature sensor 16 gradually rise. If the rate of temperature rise (g) of the lid temperature Tf from immediately after the start of the boil and heat process, relative to the rate of temperature rise (f) from when the pot bottom temperature Tn reaches the predetermined temperature of 80°C, is smaller than the predetermined rate of temperature rise, it can be determined that the temperature rise in the upper part of the pot 7 is slow. This could be due to a weak heating amount, a large amount of water for the food item A to be cooked, or cold water. In such cases, traditional stove cooking methods would empirically increase the firewood fire to adjust the heat.

In this embodiment, therefore, to achieve the same heat control as cooking in a traditional Japanese stove, if the temperature rise rate (g) of the lid temperature Tf is smaller than a predetermined value relative to the temperature rise rate (f) when the pot bottom temperature Tn reaches a predetermined temperature immediately after the start of the boiling heating process, the heat amount fluctuation means 44 is configured to temporarily change the fluctuation pattern of the heat amount S2 to the pot 7, set as the second pattern, by increasing the heat amount S2 during the subsequent heating adjustment (H) period until boiling.

In other words, in the example described above, the heat amount fluctuation means 44 periodically and repeatedly changed the heat amount S2 in a 1-second cycle C with a lower limit S2min of 1200W and an upper limit S2max of 1400W to achieve a high heat and intense flame when heating to a boil in the "heat to boil" process. However, the lower limit S2min is increased from 1200W to 1300W, and the output maintenance time D during which the heat amount S2 is maintained at the upper limit S2max of 1400W is extended from 100ms (0.1 seconds) to 500ms (0.5 seconds), thereby temporarily increasing the heat amount S2 of the pot 7.

Next, an example of adjusting the heat amount S2 during the "heating to boil" process when boiling continues after boiling will be described with reference to Figures 7 and 8. In each of these figures, the heat amount fluctuation means 44 monitors the temperature state of the upper layer of the pot 7 based on the change in the lid temperature Tf measured by the lid temperature sensor 16, using the point (X) when the temperature rise rate (e) of the pot bottom temperature Tn measured by the pot temperature sensor 15 falls below a predetermined value and boiling is detected, and adjusts the heat amount S2 according to the fluctuation pattern after boiling is detected based on the monitoring results.

As shown in Figure 7, the lid temperature Tf, which is the temperature detected by the lid temperature sensor 16, rises rapidly when the upper layers of the pot 7 begin to boil. The heat fluctuation means 44 monitors the phenomenon in which the lid temperature Tf rises above a predetermined value within a predetermined period of time by measuring the temperature rise rate (i) of the lid temperature Tf.

Here, the heat amount fluctuation means 44 determines the time difference between the point (X) when the pot bottom temperature Tn measured by the pot temperature sensor 15 falls below a predetermined value for a predetermined period of time, i.e., the point (X) when boiling is detected and the point (i) when the temperature rise rate (i) of the lid temperature Tf rises to a predetermined value. If the point (i) when the temperature rise rate (i) of the lid temperature Tf exceeds the predetermined value occurs earlier than the point (X) when boiling is detected at the pot bottom temperature Tn, this may indicate that the amount of heat is too strong, the amount of water for the food item A to be cooked is too small, or the water temperature is too high, and so the heat amount fluctuation means 44 reduces the heat amount S2 of the pot 7 while boiling continues. Conversely, if the point at which the temperature rise rate (i) of the lid temperature Tf reaches or exceeds the predetermined value occurs later than the point at which boiling is detected at the pot bottom temperature Tn (X), it is possible that the amount of heating was too weak, the amount of water was too much, or the water temperature was low, and so the heating amount fluctuation means 44 increases the heating amount S2 of the pot 7 while boiling continues.

As shown in Figure 8, the heat amount fluctuation means 44 uses the point (X) when boiling is detected at the aforementioned pot bottom temperature Tn as a reference point and determines the time difference between the point when the lid temperature Tf falls below a predetermined value within a predetermined time, i.e., the temperature rise rate (d) of the lid temperature Tf falls below a predetermined value, and the point when boiling is detected by the lid temperature sensor 16. If the point when the temperature rise rate (d) of the lid temperature Tf falls below the predetermined value is delayed within the predetermined time from the point (X) when boiling is detected at the pot bottom temperature Tn, this may be because the amount of heat was too strong, the amount of water was too small, or the water temperature was too high, and so the heat amount fluctuation means 44 reduces the heat amount S2 of the pot 7 while boiling continues. Conversely, if the point at which the temperature rise rate (d) of the lid temperature Tf falls below the predetermined value is delayed by more than the predetermined time from the point at which boiling is detected at the pot bottom temperature Tn (X), this may indicate that the amount of heating was too weak, the amount of water was too large, or the water temperature was low, and the heating amount fluctuation means 44 increases the heating amount S2 of the pot 7 while boiling continues.

In other words, in the above example, the heating amount fluctuation means 44 periodically and repeatedly changed the heating amount S2 in a 4-second cycle C with the lower limit S2min set to 800 W and the upper limit S2max set to 1000 W to achieve a medium, gentle flame during the "boiling heating" process until the rice reached the boiling point. However, to increase the heating amount S2 according to the fluctuation pattern after boiling is detected, the lower limit S2min can be increased from 800 W to 900 W, or the output maintenance time D during which the heating amount S2 is maintained at the upper limit S2max of 1000 W can be made longer than the predetermined time of 400 ms (0.4 seconds). Conversely, to decrease the heating amount S2 according to the fluctuation pattern after boiling is detected, the upper limit S2max can be decreased from 100 W to 900 W, or the output maintenance time D during which the heating amount S2 is maintained at 900 W can be made shorter than the predetermined time of 400 ms (0.4 seconds).

In this embodiment, the heat amount fluctuation means 44 is configured to temporarily generate an irregular pattern or a regular pattern mixed with an irregular pattern for the amount of heat S2 from the bottom heating element 11 to the pot 7, based on the relationship between the temperature changes detected by the pot temperature sensor 15 and the lid temperature sensor 16, particularly when heating up to boiling or while boiling continues. However, it is also possible to temporarily generate an irregular pattern or a regular pattern mixed with an irregular pattern for fluctuations in the amount of heat S2 during other rice cooking processes, such as when cooking or soaking. Furthermore, the trigger for generating such an irregular pattern is not limited to the relationship between the temperature changes detected by the pot temperature sensor 15 and the lid temperature sensor 16, and it is also possible to consider the relationship between the pressure changes detected by the pressure sensor 17, etc.

In other words, in traditional cooking using a hearth, the heat of the firewood is adjusted using the five human senses as sensors, such as the state of the firewood, the amount of steam and vapor, the time when the boiling sound occurs, the strength and duration of steam generation, and the aroma. However, the heat is not the same every time, but is flexibly adjusted depending on the state of steam generation and other factors. In this way, the rice cooker of this embodiment also aims to adjust the next heating amount S2 depending on the cooking progress, such as the temperature and pressure during cooking and the generation of steam.

Therefore, when the pot 7 is pressurized during boiling, the subsequent fluctuations in the heating amount S2 may be temporarily changed to a pattern that includes irregularities when the pot 7 reaches a boiling state, based on the rate of pressure increase in the pot 7 detected by the pressure sensor 17 and the rate of pressure reduction (rate of pressure decrease) in the pot 7 when the pressure is released.

In this embodiment, the heat amount fluctuation means 44 can be used to set the heat amount S2 of the bottom heater 11 in an irregular pattern, or to set a pattern that combines a regular pattern with an irregular pattern, making it possible to cook the food A in the pot 7 with heating that is closer to the flickering flames of a wood fire.

In addition, the control unit 31, which is equipped with AI (artificial intelligence) functions, can learn how to adjust the next heating step based on the cooking progress, such as the temperature and pressure during cooking and the generation of steam, from actual data on the temperature and pressure of cooking in a stove, allowing the AI to give irregular instructions.

The heat amount fluctuation means 44 of this embodiment is configured to periodically repeat the upper limit S2max and lower limit S2min of the heat amount S2, and vary the heat amount S2 of the bottom heater 11 in accordance with the progress of the rice cooking process so that the upper limit S2max and lower limit S2min associated with the time element of the heat amount S2, i.e., the upper limit S2max, the lower limit S2min, and/or the cycle C, which is the period, change.

This means that in response to the changes in heating of the pot 7 over time caused by the rice cooking control means 41, which follows the traditional cooking stove control method described above: "Start with a trickle, then a pop, and when it starts to sizzle, turn the heat down, burn a handful of straw, and don't take the lid off even if the baby cries," the amount of heat S2 applied to the pot 7 by induction heating is increased or decreased every 0.1 to 1 second within a 1 to 10 second cycle as each cooking step progresses, and a second pattern is generated in which the output of the inverter 37, which corresponds to the amount of heat from the bottom heater 11, varies to approximately 200 W overall. The heat amount S2 based on this second pattern is then applied to the pot 7 by the heat amount fluctuation means 44, which adds a heating configuration that takes into account the fluctuations of a wood-fired flame.

In the above example, the upper limit S2max and lower limit S2min of the intensity waveform of the heat amount S2 according to the time element are changed in accordance with the change over time in the rice cooking process. That is, in the heating of the soaking process corresponding to "First trickle," the inverter 37 output is set to low heat of 500W to 700W, and a gentle flame heat amount S2 of 7 seconds per cycle C is applied to the pot 7. In the boiling heating process corresponding to "Medium pappa," the inverter 37 output is set to high heat of 1200W to 1400W, and an intense flame heat amount S2 of 1 second per cycle C is applied to the pot 7. During heating while boiling continues in the boiling heating process, which corresponds to "burning a handful of straw, don't take the lid off even if the baby cries," the inverter 37 output is set to medium heat of 800W to 1000W, and a gentle flame heat amount S2 of 4 seconds per cycle C is applied to the pot 7. During double boiling heating during steaming in the steaming process, which corresponds to "burning a handful of straw, don't take the lid off even if the baby cries," the inverter 37 output is set to low heat of 500W to 700W, and a gentle flame heat amount S2 of 10 seconds per cycle C is applied to the pot 7.

In this embodiment, the heat amount fluctuation means 44 changes the upper limit S2max and lower limit S2min associated with the time element of the heat amount S2 in response to changes over time in the rice cooking process. This makes it possible to cook the food A in the pot 7 with heating that varies for each stage of the cooking process and is similar to cooking in a stove with flickering flames from a wood fire.

The heating amount fluctuation means 44 of this embodiment is configured to set an upper limit value S2max of the heating amount S2, a lower limit value S2min of the heating amount S2, and one or more intermediate values of the heating amount S2 using multiple stepwise heating amounts S2.

Figure 9 shows the relationship between the heating amount S2 and time at high heat when the inverter 37 output is in the range of 1200W to 1400W in the example described above. As shown in Figure 9 (B), the heating amount fluctuation means 44 sets the heating amount S2 corresponding to high heat from six levels of heating amount S2: 1200W, 1240W, 1280W, 1320W, 1360W, and 1400W, and configures the fluctuation of the heating amount S2 by the length of the heating amount S2 at each level, i.e., the length of the output maintenance time D. For comparison, Figure 9 (A) shows an example in which the heating amount S2 is continuously and steplessly varied by the heating amount fluctuation means 44.

Figure 10 shows the relationship between the heating amount S2 and time at medium heat when the inverter 37 output is in the range of 800W to 1000W in the example described above. As shown in Figure 10 (B), the heating amount fluctuation means 44 sets the heating amount S2 corresponding to medium heat from six levels of heating amount S2: 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, Figure 10 (A) shows an example in which the heating amount S2 is continuously and steplessly varied by the heating amount fluctuation means 44.

Figure 11 shows the relationship between the heating amount S2 and time at low heat when the inverter 37 output is in the range of 500W to 700W in the example described above. As shown in Figure 11 (B), the heating amount fluctuation means 44 sets the heating amount S2 corresponding to low heat from six levels of heating amount S2: 500W, 540W, 580W, 620W, 660W, and 700W, and configures the fluctuation of the heating amount S2 by the length of the output maintenance time D at each level. For comparison, Figure 11 (A) shows an example in which the heating amount S2 is continuously and steplessly varied by the heating amount fluctuation means 44.

In this embodiment, the heat amount fluctuation means 44 is configured to set the heat amount band (heat amount S2 range) constituting the essential parts of high, medium, and low heat, for example, using multiple levels of heat amount including an upper limit value S2max, a lower limit value S2min, and an intermediate value. This eliminates the need to continuously vary the high-frequency pulse drive signal to the inverter 37, simplifying the circuit configuration of the first heating drive unit 32, including the inverter 37, and enabling the inverter 37 to be made more compact.

The heating amount fluctuation means 44 of this embodiment is configured to set the upper limit value S2max of the heating amount S2 so that it does not exceed the rated power consumption of the rice cooker.

The rated power consumption of rice cookers is specified by the Electrical Appliance and Material Safety Act. In the example described above, even if the inverter 37 is set to output 1200W to 1400W on high heat, power consumption fluctuates over time, making it difficult to inspect power consumption on a manufacturing assembly line, for example. Therefore, in this embodiment, the control unit 31, which includes the rice cooking control means 41 and the heating amount fluctuation means 44, controls and limits the inverter 37 output, corresponding to the upper limit S2max of the heating amount S2, so that it does not exceed the rice cooker's rated power consumption, or, if it does exceed it, it does so by no more than 5%. Specifically, if the rice cooker's rated power consumption is 1400W, the inverter 37 output is limited to 1470W or less. The rice cooker's control unit 31 may also be equipped with an inspection means (not shown) that operates the inverter 37 at an output of 1400W for, for example, 60 seconds as a test mode for inspection, or that outputs power continuously for a predetermined period of time.

However, the rated power consumption of a rice cooker may include not only heating from the bottom heating element 11 to the pot 7 via the heating coil, but also heating of the lid 2 via the lid heating element 18 and heating of the sides of the pot 7 via the side heating element 12. Therefore, if the lid heating element 18 consumes 50 W of power and heats simultaneously with the bottom heating element 11, it is preferable to set the inverter 37 output, which corresponds to the upper limit S2max of the heating amount S2, to 1,350 W, which is the total power consumption of the bottom heating element 11 and the lid heating element 18 and does not exceed the rated power consumption of the rice cooker.

In addition, in the above example, the inverter 37 output is set to a high flame in the range of 1200W to 1400W, and the lower limit S2min of the heating amount S2 is set to 1200W. However, in the case of an actual wood fire, the heating power equivalent to the heating amount S2 to the pot 7 will not drop significantly instantaneously even if there is fluctuation. Therefore, it is preferable for the heating amount fluctuation means 44 to set a limit on the lower limit S2min of the heating amount S2 so that it does not fall below 50% of the upper limit S2max. In other words, if the upper limit S2max of the heating amount S2 is set to 1400W, the lower limit S2min of the heating amount S2 is limited to not fall below 700W.

In this way, in this embodiment, when fluctuation control is added to the heat amount S2 of the bottom heater 11 using the heat amount fluctuation means 44, there is no problem with power consumption inspections during manufacturing, and in compliance with laws and regulations, problems such as current exceeding the rated power consumption of the rice cooker and exceeding the limited current of indoor wiring can be prevented.

In this embodiment, the heat amount fluctuation means 44 is configured with multiple second patterns depending on the type of rice cooking performed by the rice cooking control means 41.

Rice cooking methods such as the rice cooking control means 41 detecting the amount of food A (cooked rice amount) placed in the pot 7 and changing the heating pattern (first pattern) depending on the amount of rice to be cooked, selecting brown rice, polished rice, local variety brand rice, etc. via the operation unit 4 and cooking rice using a heating pattern appropriate to the rice quality, or varying the cooked texture (hard, soft, sticky, sweet, etc.) via the operation unit 4 and cooking rice using a heating pattern appropriate to that texture are well known in the art. In this embodiment, for the various conventional rice cooking methods performed by the rice cooking control means 41, a specific second pattern that enables the heating amount fluctuation means 44 to control the fluctuation of the heating amount S2 can be selected from multiple second patterns pre-stored in the storage means 35 and applied.

In this way, in this embodiment, the second pattern can be selected, which enables appropriate fluctuation control of the heating amount S depending on the amount of rice cooked, the cooking menu, the cooking method, and the rice growing region, variety, and brand.

The present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the "predetermined value," "predetermined temperature," and "predetermined rate of temperature rise," which appear frequently in this embodiment, do not need to be the same value each time, and may be set to a different value.

7 Pot 11 Bottom heating element (heating means)
41 rice cooking control means 44 heating amount fluctuation means (heat amount variable means)
C Cycle (length of period)
D. Output maintenance time (maintenance time of heating amount 1)

Claims (2)

a pot for containing food to be cooked;
a heating means for heating the pot;
A rice cooking control means for changing the amount of heat of the heating means as the process progresses to cook the food to be cooked;
a heating amount varying means for varying the heating amount of the heating means over time;
Equipped with
The steps include a soaking step, a heating step until boiling, a heating step while boiling continues, and a steaming step,
The heating amount varying means varies the heating amount of the heating means so as to periodically repeat an upper limit value of the heating amount, a lower limit value of the heating amount, and one or more heating amount values between the upper limit value and the lower limit value in at least two or more steps of the soaking cooking step, the heating step until boiling, the heating step while boiling continues, and the steaming step, and the upper limit value, the lower limit value, and the length of the cycle are different,
A rice cooker characterized in that the maintenance time of one heating amount in the cycle varies depending on the length of the cycle. The rice cooker according to claim 1, wherein the upper limit value and the lower limit value are, respectively, the heating step until boiling > the heating step while boiling continues > the soaking cooking step, and the heating step until boiling > the heating step while boiling continues > the soaking cooking step.