rice cooker

Abstract

To improve the taste of rice. [Solution] The rice cooker according to this disclosure comprises a pot containing the contents to be cooked, including water and rice; a main body provided with a bottomed cylindrical pot storage section; an annular inner coil that induces heating around the central part of the bottom of the pot; an annular outer coil that induces heating around the outer edge of the bottom of the pot; and a control unit that adjusts the first power supplied to the inner coil and the second power supplied to the outer coil, and controls the inner coil and the outer coil. When the control unit supplies power to both the inner coil and the outer coil, it changes the ratio of the first power to the second power according to the amount of the contents to be cooked.

Description

Technical Field

[0001] The present disclosure relates to a rice cooker.

Background Art

[0002] Patent Document 1 discloses a rice cooker including a pot, a rice cooker main body provided with a pot storage section for storing the pot, a heating section for heating the pot, and a control section for controlling the heating section to perform a rice cooking process including a preheating step, a temperature rising step, a boiling maintenance step, and a steaming step. The heating section includes an inner bottom heating coil arranged to face around the central portion of the bottom of the pot, and an outer bottom heating coil arranged to face the corner portion of the bottom of the pot.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The rice cooker of Patent Document 1 still has room for improvement from the viewpoint of improving the taste of the cooked rice.

[0005] The present disclosure aims to improve the taste of the cooked rice.

Means for Solving the Problems

[0006] A rice cooker according to an aspect of the present disclosure includes a pot for containing an object to be cooked rice including water and rice, a main body provided with a bottomed cylindrical pot storage section for storing the pot, an annular inner coil provided on the main body for inductively heating around the central portion of the bottom of the pot, an annular outer coil provided outside the inner coil in a plan view seen from the depth direction of the pot storage section in the main body for inductively heating the outer edge portion of the bottom of the pot A control unit that adjusts the first power supplied to the inner coil and the second power supplied to the outer coil, and controls the inner coil and the outer coil, Equipped with, When the control unit supplies power to both the inner coil and the outer coil, it changes the ratio of the first power to the second power according to the amount of food being cooked. [Effects of the Invention]

[0007] According to the rice cooker of the above embodiment, the taste of the rice can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] This is a perspective view of a rice cooker according to an embodiment of the present disclosure, showing the lid in a closed state. [Figure 2] This is a perspective view of a rice cooker according to an embodiment of the present disclosure, showing the lid in an open state. [Figure 3] Figure 1 is a cross-sectional view of the rice cooker along the line A1-A1. [Figure 4] Figure 1 is a block diagram showing the schematic configuration of the rice cooker. [Figure 5] This is a schematic diagram showing the temperature of the cooked food, the first power, the second power, and the power ratio for different amounts of rice when cooking rice in the rice cooker shown in Figure 1. [Modes for carrying out the invention]

[0009] <Knowledge that forms the basis of this disclosure> The disclosers, through diligent research into improving the taste of rice, discovered that the consistency of the taste of rice decreases depending on the amount of rice cooked.

[0010] For example, during the preheating process, the temperature of the upper part of the rice being cooked, away from the bottom of the pot, rises less easily the larger the amount of rice being cooked. Therefore, when cooking a large amount of rice, the temperature of the upper part of the rice being cooked may not rise to the desired preheating temperature (for example, a temperature below the gelatinization temperature), resulting in insufficient heating of the rice located at the top. As a result, some of the rice becomes hard. On the other hand, when cooking a small amount of rice, the temperature of the upper part of the rice being cooked may rise above the desired preheating temperature. In this case, the upper part of the rice being cooked may gelatinize excessively, resulting in excessively sticky rice.

[0011] Furthermore, during the steaming process, condensation of water vapor inside the pot creates dew that travels down the sides of the pot and accumulates on the outer edge of the bottom. The larger the amount of rice being cooked, the more water vapor is produced inside the pot, and the more dew accumulates on the outer edge. If too much dew accumulates on the outer edge, the rice near the edge will be exposed to the dew and become too soft. On the other hand, if the amount of rice being cooked is small, the rice near the outer edge will be overheated and dry out.

[0012] Such a decline in the taste of rice is caused by excessive or insufficient heating in certain parts of the pot. In conventional rice cookers, the ratio of power supplied to the bottom heating coil to the power supplied to the bottom heating coil is kept constant, for example, in each stage of cooking. That is, in each stage, this power ratio is kept constant regardless of the amount of rice being cooked (hereinafter also referred to as "amount of rice cooked"). Therefore, it is difficult to apply the desired amount of heating to each part of the pot without excessive or insufficient heating, in accordance with the conditions inside the pot that change with the amount of rice cooked.

[0013] Therefore, the Disclosers have found a configuration in which the control unit changes the ratio of the power according to the amount of rice being cooked. With this configuration, the desired heating power can be applied without excess or deficiency to different parts of the pot and the rice being cooked in each cooking stage. As a result, the deterioration of the taste of the rice due to differences in the amount of rice being cooked can be suppressed, and the taste of the rice can be improved. Based on this novel finding, the Disclosers have made the following disclosure.

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, terms indicating a specific direction or position (for example, terms including “up”, “down”, “right”, and “left”) are used as necessary. However, the use of these terms is for facilitating the understanding of the present disclosure with reference to the drawings, and the technical scope of the present disclosure is not limited by the meanings of these terms. Further, the following description is merely illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0015] <Embodiment> An example of a rice cooker according to an embodiment of the present disclosure will be described. In the rice cooker according to this embodiment, it is possible to cook rice in an amount of 1 liter to 3 liters. FIG. 1 is a perspective view of the rice cooker according to the embodiment of the present disclosure, showing a state in which the lid is closed. FIG. 2 is a perspective view of the rice cooker according to the embodiment of the present disclosure, showing a state in which the lid is open.

[0016] As shown in FIG. 1 or FIG. 2, the rice cooker according to this embodiment includes a substantially bottomed cylindrical main body 1 and a lid 2 that opens and closes the upper opening 1A of the main body 1 in a freely openable and closable manner.

[0017] As shown in FIG. 2, the main body 1 is provided with a bottomed cylindrical pot storage portion 1C for detachably storing the pot 3. The pot 3 contains the rice and water and other items to be cooked.

[0018] On the side surface of the main body 1, a selection unit 4 for setting the rice cooking process of the items to be cooked stored in the pot 3 is provided. The selection unit 4 includes, for example, a liquid crystal display for displaying various information such as a rice cooking course and a rice cooking time, and a plurality of buttons for instructing the execution of, in addition to the selection of the rice cooking course, the start, cancellation, reservation, etc. of the rice cooking. The user can select a specific rice cooking course and instruct the start of the rice cooking by operating the plurality of buttons while referring to the various information displayed on the liquid crystal display. Note that the selection unit 4 may include, for example, a touch panel.

[0019] Furthermore, before starting the cooking process, the user can select the amount of food to be cooked (hereinafter also referred to as "cooking amount") via the selection unit 4. For example, the user can select the amount of rice to be cooked in units of 1 sho (approximately 1.8 liters) using the multiple buttons provided on the selection unit 4.

[0020] The lid 2 is attached to the upper part of the main body 1 via a hinge portion 1B. The lid 2 is configured to open and close the upper opening 1A of the main body 1 by rotating around the hinge portion 1B. That is, the lid 2 is configured to rotate between a position that closes the upper opening 1A of the main body 1 (see Figure 1) and a position that opens the upper opening 1A of the main body 1 (see Figure 2).

[0021] As shown in Figure 1, the lid 2 is provided with a steam outlet 2A that discharges steam generated inside the pot 3 to the outside of the rice cooker. The steam outlet 2A is provided to be in fluid communication with the internal space of the pot 3. In this embodiment, the user can confirm that the food being cooked inside the pot 3 is boiling over to the outside of the pot 3 by visually observing the food boiling over from the steam outlet 2A.

[0022] Figure 3 is a cross-sectional view of the rice cooker shown in Figure 1, taken along the line A1-A1.

[0023] As shown in Figure 3, the rice cooker according to this embodiment includes a heating unit 5 provided in the main body 1 for heating the pot 3, a temperature detection unit 6 for detecting the temperature of the pot 3, and a control unit 7 for executing the rice cooking process.

[0024] The heating unit 5 is composed of, for example, an induction heating coil that induction heats the pot 3. The heating unit 5 is positioned opposite the bottom of the pot 3. In this embodiment, the heating unit 5 includes an annular bottom internal heating coil 5a positioned opposite the central part of the bottom of the pot 3, and an annular bottom external heating coil 5b positioned opposite the corners of the bottom of the pot 3. The bottom internal heating coil 5a induction heats the central part of the bottom of the pot 3. The bottom external heating coil 5b is located outside the bottom internal heating coil 5a in a plan view taken from the depth direction of the pot storage unit 1C, and induction heats the outer edge 3A of the bottom of the pot 3. The bottom internal heating coil 5a is an example of an internal coil in this disclosure. The bottom external heating coil 5b is an example of an external coil in this disclosure.

[0025] In this embodiment, at least a portion of the bottom external heating coil 5b is located above the bottom internal heating coil 5a in the depth direction of the pot storage section 1C. In the example shown in Figure 3, the entire portion of the bottom external heating coil 5b is located above the bottom external heating coil 5b.

[0026] The temperature detection unit 6 is, for example, a pot temperature sensor that detects the temperature of the bottom of the pot 3. In this embodiment, the temperature detection unit 6 is positioned so as to be able to contact the center of the bottom of the pot 3 housed in the main body 1. Since the temperature of the pot 3 is approximately the same as the temperature of the food being cooked inside the pot 3, the temperature detection unit 6 can detect the temperature of the pot 3 and estimate the temperature of the food being cooked inside the pot 3.

[0027] The control unit 7 controls the pot heating operation of the heating unit 5 based on the temperature detected by the temperature detection unit 6 and executes the rice cooking process. Specifically, the control unit 7 adjusts the first power supplied to the bottom heating coil 5a and the second power supplied to the bottom heating coil 5b based on the temperature of the bottom of the pot 3 detected by the temperature detection unit 6. In this embodiment, the control unit 7 is located inside the main body 1, below the pot 3.

[0028] Figure 4 is a block diagram showing the schematic configuration of the rice cooker in Figure 1. As shown in Figure 4, in this embodiment, the control unit 7 has an inverter circuit 71 that adjusts the first power supplied to the bottom heating coil 5a and an inverter circuit 72 that adjusts the second power supplied to the bottom heating coil 5b. The inverter circuit 72 is provided independently of the inverter circuit 71 and adjusts the second power independently of the first power. That is, the inverter circuit 72 is not a common inverter circuit with the inverter circuit 71. The inverter circuit 71 is an example of the first power adjustment unit in this disclosure. The inverter circuit 72 is an example of the second power adjustment unit in this disclosure. The control unit 7 may control the first power adjustment unit and the second power adjustment unit to adjust the first power and the second power independently, so that the sum of the first power and the second power does not exceed a predetermined value, or so that the ratio of the first power and the second power is a predetermined value.

[0029] The rice cooker further includes a power connection unit 81 that can be connected to a power source that supplies power to the rice cooker, and a rectifier circuit 82 connected between the power connection unit 81 and the control unit 7.

[0030] The power connection section 81 is the connection point to an external power source, such as a commercial power supply, generator, or energy storage device. A portion of the power connection section 81 is exposed to the outside for connection to the external power source, but this is omitted in Figures 1 and 2. In this embodiment, the power connection section 81 is a plug that connects to an outlet. The power connection section 81 is supplied with alternating current voltage (AC voltage) as power.

[0031] The rectifier circuit 82 is supplied with an AC voltage via the power supply connection section 81. The rectifier circuit 82 rectifies the supplied AC power and supplies it to the control unit 7. In this embodiment, the power output from the rectifier circuit 82 is supplied to the inverter circuits 71 and 72, respectively.

[0032] Each inverter circuit 71, 72 converts the DC or low-frequency current output from the rectifier circuit 82 into a high-frequency current and supplies it to the corresponding heating coils 5a, 5b. At this time, each inverter circuit 71, 72 adjusts the first power or the second power by changing at least one of the energizing rate and frequency of the high-frequency current supplied to the heating coils 5a, 5b.

[0033] The control unit 7 is equipped with a memory unit that stores multiple rice cooking sequences. Here, a "rice cooking sequence" refers to a rice cooking procedure in which the five main steps shown in Figure 5—preheating, heating, power reduction (PD), boil maintenance, and steaming—are performed in sequence, with predetermined parameters such as the energizing time, heating temperature, heating time, and heating output for each step. For example, multiple rice cooking sequences correspond to multiple rice cooking quantities (e.g., 1 sho, 2 sho, and 3 sho) that can be selected by the selection unit 4. The control unit 7 controls the heating unit 5 based on the rice cooking quantity selected by the selection unit 4 and the temperature detected by the temperature detection unit 6, and executes the rice cooking process.

[0034] Figure 5 is a schematic diagram showing the temperature of the cooked food, the first power, the second power, and the power ratio for different amounts of rice when cooking rice in the rice cooker shown in Figure 1.

[0035] When the selection unit 4 selects various cooking information, including the amount of rice to be cooked, and the control unit 7 receives an instruction to start cooking, it executes a preheating process.

[0036] The preheating process involves soaking the rice in water at a temperature lower than the gelatinization start temperature of rice (approximately 60°C) to allow the rice to absorb water in advance. During the preheating process, the control unit 7 heats the pot 3 to a preheating temperature lower than the gelatinization start temperature of rice (for example, 50°C) and controls the heating unit 5 to maintain the rice being cooked at that preheating temperature. After a predetermined time (for example, 20 minutes) has elapsed from the start of the preheating process, the process moves to the heating step.

[0037] The heating process is the process of raising the temperature of the food to be cooked in the pot 3 to just before the boiling point. During the heating process, the control unit 7 controls the heating unit 5 so that the temperature of the food to be cooked in the pot 3 rises to just before the boiling point. When the temperature detected by the temperature detection unit 6 rises to a predetermined temperature (for example, 98°C), the process moves to the power-down process.

[0038] The power-down (hereinafter also referred to as PD) process is a process in which the heating force of the heating unit 5 is reduced in order to prevent the food being cooked from boiling over to the outside of the pot 3. The power-down process ends, for example, after a predetermined time (for example, 1 minute) has elapsed since the start of the power-down process. After the power-down process ends, the process moves on to the boiling maintenance process.

[0039] The boiling maintenance process is a process that maintains the boiling state of the rice being cooked in the pot 3, gelatinizing the starch in the rice and raising the degree of gelatinization to, for example, 50% to 80%. In the boiling maintenance process, the control unit 7 controls the heating unit 5 to heat the pot 3 with a lower heating amount than in the heating rise process. When the water in the pot 3 is gone and the temperature detected by the temperature detection unit 6 is above the boiling point of water (for example, 130°C), the process moves to the steaming process.

[0040] The steaming process uses residual heat to evaporate excess moisture from the rice, steaming it and increasing its gelatinization to nearly 100%. During the steaming process, the control unit 7 controls the heating unit 5 to lower the temperature of the rice to be cooked to a predetermined steaming temperature (e.g., 100°C) and then maintain that steaming temperature. After a predetermined time (e.g., 20 minutes) has elapsed from the start of the steaming process, the rice cooking process is terminated.

[0041] The steaming process may also include a high-temperature maintenance process from the end of the boiling maintenance process until the temperature of the cooked food drops to a predetermined steaming temperature. For example, the control unit 7 may control the heating unit 5 to heat the pot 3 with a stronger heating force during the high-temperature maintenance process than the period for which the cooked food is maintained at the steaming temperature. In this case, the temperature drop of the cooked food from the temperature at the end of the boiling maintenance process to the predetermined steaming temperature will be more gradual.

[0042] Referring to Figure 5, the first power, second power, and power ratio during cooking of the maximum rice cooking capacity (3 sho) and the minimum rice cooking capacity (1 sho) will be explained. When the control unit 7 supplies power to both the bottom internal heating coil 5a and the bottom external heating coil 5b, it changes the ratio of the second power to the first power according to the amount of rice being cooked. In the following explanation, the ratio of the second power to the first power, that is, the value obtained by dividing the second power by the first power, may be referred to as the "power ratio".

[0043] If the maximum rice cooking amount is selected in the selection unit 4, the control unit 7 executes the cooking process while adjusting the first and second power based on the cooking sequence corresponding to the maximum rice cooking amount. On the other hand, if the minimum rice cooking amount is selected in the selection unit 4, the control unit 7 executes the cooking process while adjusting the first and second power based on the cooking sequence corresponding to the minimum rice cooking amount.

[0044] The control unit 7 adjusts the first and second power during the preheating process so that the power ratio when cooking the minimum amount of rice is smaller than the power ratio when cooking the maximum amount of rice. For example, the control unit 7 adjusts the first and second power so that the power ratio decreases as the amount of rice decreases.

[0045] In this embodiment, during the preheating process, the control unit 7 adjusts the first power to 700W and the second power to 2000W when cooking the maximum amount of rice, until the temperature of the rice to be cooked reaches the preheating temperature. In this case, the power ratio is 2.86. On the other hand, when cooking the minimum amount of rice, the control unit 7 adjusts the first power to 1000W and the second power to 700W. In this case, the power ratio is 0.70, which is smaller than the power ratio when cooking the maximum amount of rice.

[0046] When the food to be cooked reaches the preheating temperature, the control unit 7 controls the heating unit 5 to maintain the food at that temperature. For example, the control unit 7 reduces the first and second power to less than the power used until the food reached the preheating temperature, and continues to supply power to the heating coils 5a and 5b. Alternatively, the control unit 7 may stop supplying power to the heating coils 5a and 5b when the temperature of the food reaches or exceeds the preheating temperature, and resume supplying power when the temperature falls below the preheating temperature. In either case, when the control unit 7 supplies power to the heating coils 5a and 5b after the food has reached the preheating temperature, it may maintain the power ratio described above that was in place before the food reached the preheating temperature.

[0047] During the heating process, the control unit 7 adjusts the first and second power so that, for example, the power ratio when cooking the maximum amount of rice is greater than the power ratio when cooking the minimum amount of rice. For example, the control unit 7 adjusts the first and second power so that the power ratio increases as the amount of rice increases. In this embodiment, during the heating process, the control unit 7 adjusts the first power to 1500W and the second power to 1200W when cooking the minimum amount of rice. In this case, the power ratio is 0.80. On the other hand, when cooking the maximum amount of rice, the control unit 7 adjusts the first power to 1400W and the second power to 2000W. In this case, the power ratio is 1.43, which is greater than the power ratio when cooking the minimum amount of rice.

[0048] During the power-down process, the control unit 7 stops supplying power to both heating coils 5a and 5b in the case of the maximum rice cooking capacity in order to more reliably prevent the rice from boiling over outside the pot 3. On the other hand, in the case of the minimum rice cooking capacity, the control unit 7 adjusts the first power to 1400W and the second power to 1100W. In this case, the power ratio is 0.79.

[0049] During the boiling maintenance process, the control unit 7 adjusts the first and second power so that, for example, the power ratio when cooking the maximum amount of rice is greater than the power ratio when cooking the minimum amount of rice. For example, the control unit 7 adjusts the first and second power so that the power ratio increases as the amount of rice increases. In this embodiment, during the boiling maintenance process, the control unit 7 adjusts the first power to 1400W and the second power to 1100W when cooking the minimum amount of rice. In this case, the power ratio is 0.79. On the other hand, when cooking the maximum amount of rice, the control unit 7 adjusts the first power to 1200W and the second power to 2000W. In this case, the power ratio is 1.67, which is greater than the power ratio when cooking the minimum amount of rice.

[0050] During the steaming process, the control unit 7 adjusts the first and second power so that the power ratio when cooking the minimum amount of rice is smaller than the power ratio when cooking the maximum amount of rice. For example, the control unit 7 adjusts the first and second power so that the power ratio decreases as the amount of rice decreases.

[0051] In this embodiment, during the steaming process, the control unit 7 adjusts the first power to 250W and the second power to 1000W when the maximum amount of rice is being cooked. In this case, the power ratio is 4.00. On the other hand, when the minimum amount of rice is being cooked, the control unit 7 adjusts the first power to 600W and the second power to 300W. In this case, the power ratio is 0.50, which is smaller than the power ratio when the maximum amount of rice is being cooked.

[0052] In the preheating, temperature rise, boil maintenance, and steaming processes, the second power level is greater than the first power level when cooking the maximum amount of rice, and less than the first power level when cooking the minimum amount of rice. In other words, the relative magnitudes of the first and second power levels are reversed in each process depending on the amount of rice being cooked between the maximum and minimum cooking amounts.

[0053] When the amount of rice to be cooked is an intermediate amount between the maximum and minimum cooking amounts, the control unit 7 may adjust the first and second power in each cooking process so that the power ratio is between the power ratio at the maximum cooking amount and the power ratio at the minimum cooking amount. In the power-down process, the control unit 7 may adjust the first and second power so that the power ratio is greater than the power ratio at the minimum cooking amount when the amount of rice to be cooked is an intermediate amount.

[0054] According to the embodiment of this disclosure, the control unit 7 changes the power ratio between the first power and the second power according to the amount of rice to be cooked, so that the heating by the bottom heating coil 5a and the bottom heating coil 5b can be adjusted independently of each other according to the desired heating timing and intensity in the rice cooking process. Therefore, the deterioration of the taste of the rice due to differences in the amount of rice to be cooked can be suppressed, and the taste of the rice can be improved.

[0055] During the preheating process, if the power ratio of the second power to the first power is increased when the amount of rice to be cooked is small, the temperature of the top of the rice being cooked may rise above the desired temperature (for example, a temperature below the gelatinization temperature). In this case, gelatinization may proceed excessively at the top of the rice being cooked, potentially causing the rice at the top to become excessively sticky.

[0056] According to the embodiments of this disclosure, the control unit 7, in the preheating process, makes the power ratio during cooking with the minimum amount of rice smaller than the power ratio during cooking with the maximum amount of rice. This suppresses overheating in the upper part of the rice being cooked, thereby suppressing the progression of gelatinization in that upper part. Consequently, excessive stickiness of the rice can be suppressed, and the taste of the rice can be further improved.

[0057] According to the embodiments of this disclosure, the control unit 7 controls the two heating coils 5a and 5b in the preheating process so that the second power becomes less than or equal to the first power when cooking the minimum amount of rice. This further suppresses overheating of the top of the rice being cooked when the amount of rice is small.

[0058] In the upper part of the rice being cooked, which is farther from the bottom of pot 3, the heat from the bottom of pot 3 does not reach as easily as the amount of rice being cooked, making it difficult for the temperature to rise. In particular, during the preheating process when a lot of water remains in pot 3, insufficient heating of the upper part of the rice being cooked may cause some of the rice to harden.

[0059] According to the embodiments of this disclosure, the control unit 7 controls the two heating coils 5a and 5b in the preheating process so that the second power is greater than the first power when cooking the maximum amount of rice. This promotes a temperature rise at the top of the rice being cooked when cooking a large amount of rice, and reduces the possibility of insufficient heating of the top of the rice being cooked. Therefore, the top of the rice being cooked can be heated without excess or deficiency according to the amount of rice being cooked, further improving the taste of the rice.

[0060] When cooking small amounts of rice, increasing the power ratio of the second power to the first power during the steaming process may cause the temperature of the outer edge 3A, heated by the bottom heating coil 5b, to rise above the desired temperature. In this case, the rice located near the outer edge 3A may dry out, potentially degrading the taste of the rice.

[0061] According to the embodiments of this disclosure, the control unit 7 makes the power ratio during cooking with the minimum amount of rice smaller than the power ratio during cooking with the maximum amount of rice during the steaming process. As a result, the heating force of the bottom outer heating coil 5b is adjusted according to the amount of rice being cooked, so that the temperature of the outer edge 3A does not rise above the desired temperature. Therefore, drying of the rice located near the outer edge 3A can be suppressed, and the taste of the rice can be further improved.

[0062] According to the embodiments of this disclosure, the control unit 7 controls the two heating coils 5a and 5b in the steaming process so that the second power becomes less than or equal to the first power when cooking the minimum amount of rice. As a result, when the amount of rice is small, overheating of the outer edge 3A is further suppressed, and the rice located near the outer edge 3A becomes less likely to dry out.

[0063] During the steaming process, condensation formed on the inner wall of the pot 3 descends along that inner wall and accumulates on the outer edge 3A at the bottom of the pot 3. The larger the amount of rice being cooked, the more condensation tends to form on the wall of the pot 3, and the more condensation accumulates on the outer edge 3A. Therefore, when cooking a large amount of rice, the rice located near the outer edge 3A may be exposed to the condensation accumulated there, potentially causing it to become too soft.

[0064] According to the embodiment of this disclosure, the control unit 7 controls the two heating coils 5a and 5b in the steaming process so that the second power is greater than the first power when cooking the maximum amount of rice. As a result, when the amount of rice to be cooked is large, the outer edge 3A is heated more strongly, and the evaporation of condensation accumulated on the outer edge 3A is promoted. Therefore, excessive accumulation of condensation on the outer edge 3A is suppressed, and the rice located near the outer edge 3A does not become too soft. Consequently, the outer edge 3A and the rice located near the outer edge 3A can be heated without excess or deficiency according to the amount of rice to be cooked, thereby further improving the taste of the rice.

[0065] In conventional rice cookers, the first and second power supplies are controlled by duty cycle control. In duty cycle control, power is repeatedly supplied to and stopped from the heating coil, and the average power is adjusted by changing the ratio of the supply time to the stop time (duty cycle ratio).

[0066] During the boiling process in which rice is cooked in water, the temperature of the pot and the amount of bubbles change when the power supply is switched on and off. This change can cause the rice to move. At this time, the rice may break apart as it rubs against adjacent grains of rice and the pot. If a lot of rice breaks apart, the cooked rice will become stickier.

[0067] During the steaming process, while power is being supplied to the heating coil, the object being heated by the heating coil (for example, a part of the pot) may be heated to a temperature higher than the desired temperature. In this case, there is a risk that the rice located near the object being heated may burn.

[0068] According to the embodiments of this disclosure, since each power adjustment unit is an inverter, the adjustment of the first power and the second power can be performed by changing the current rate or frequency, rather than by duty cycle control. In other words, each adjustment unit can adjust the first power and the second power without stopping the power supply to the heating coils 5a and 5b. As a result, during the boiling maintenance process, the rice is less likely to move, and the crumbling of the rice is suppressed. During the steaming process, the temperature of the heating target is less likely to rise above the desired temperature, so scorching of the rice located near the heating target is suppressed. Therefore, the taste of the rice can be further improved.

[0069] This disclosure is not limited to the embodiments described above, and can be implemented in various other forms. For example, instead of changing the energization rate and frequency of the high-frequency current supplied to the heating coils 5a and 5b by inverter circuits 71 and 72, the control unit 7 may adjust the average power per unit time of the high-frequency current by duty cycle control. In this case, if a switching element such as a relay is added to switch the current path to the two heating coils 5a and 5b, it is not necessary to provide two inverter circuits 71 and 72 for independently adjusting the first power and the second power, in a one-to-one relationship with the two heating coils 5a and 5b, thus simplifying the configuration of the rice cooker. If duty cycle control is performed without adding a switching element such as a relay, two inverter circuits 71 and 72 for independently adjusting the first power and the second power are necessary, but the configuration of the inverter circuits 71 and 72 can be simplified.

[0070] Furthermore, in the above embodiment, the relative magnitudes of the first power and the second power were reversed in the rice cooking amounts between the maximum and minimum cooking amounts during the preheating, temperature rise, boiling maintenance, and steaming processes, but this disclosure is not limited to this. For example, the second power may be greater than or less than the first power for all rice cooking amounts that the rice cooker can handle. Also, in each process, the second power may be the same as the first power when cooking a specific amount of rice.

[0071] In particular, heating with the bottom external heating coil 5b is less likely to cause scorching of the rice compared to heating with the bottom internal heating coil 5a. Therefore, regardless of the amount of rice being cooked, by making the second power (power supplied to the bottom external heating coil 5b) greater than the first power (power supplied to the bottom internal heating coil 5a), sufficient heating can be achieved while suppressing scorching, thereby improving the taste. For this reason, it is desirable to control the heating unit 5 so that the second power is greater than the first power, especially during the boiling maintenance process and the steaming process when the temperature of the pot 3 becomes high.

[0072] Instead of the user selecting the amount of rice to be cooked using the selection unit 4, the control unit 7 may estimate the amount based on the weight of the pot 3 containing the food to be cooked. For example, this weight may be measured by a weight sensor provided on the main unit 1. Alternatively, the amount of rice to be cooked may be determined based on the time it takes for the food to reach a predetermined temperature and the temperature changes over time.

[0073] In the above embodiment, the power-down process is initiated after the temperature detected by the temperature detection unit 6 rises to a predetermined temperature (for example, 98°C), but this disclosure is not limited thereto. For example, the temperature detection unit 6 may be placed on the lid 2 to detect the temperature of the steam generated in the pot 3, and the power-down process may be initiated after the temperature detected by the temperature detection unit 6 rises to a predetermined temperature (for example, 70°C).

[0074] <Example 1> An example of a modified embodiment of the present disclosure will be described below. Note that parts that can be configured similarly to the above embodiment will not be explained here.

[0075] In Modification 1, the temperature sensing unit 6 includes a plurality of different temperature sensors. For example, it may include a bottom temperature sensor that detects the temperature of the bottom of the pot 3 and a lid temperature sensor that detects the temperature of the top of the pot 3.

[0076] In Modification 1, some of the steps in the rice cooking process transition to the next step based on relative temperature rather than absolute temperature.

[0077] In other words, for example, in the heating step, the control unit 7 controls the heating unit 5 so that the temperature of the food to be cooked in the pot 3 rises to just before the boiling point, and when the temperature detected by the lid temperature sensor rises to a predetermined temperature (for example, 98°C), it proceeds to the next step (control based on absolute temperature). Subsequently, in the boiling maintenance step, for example, the control unit 7 controls the heating unit 5 to heat the pot 3 with a lower heating amount than in the heating step, and when the temperature detected by the bottom temperature sensor rises by a predetermined temperature (for example, 30°C) or more above the temperature detected by the bottom temperature sensor at the end of the heating step described above, it proceeds to the next step (control based on relative temperature).

[0078] When controlling heating using multiple temperature sensors, performing relative temperature-based control in at least some of the processes can reduce temperature variations between cooking cycles compared to conventional methods that rely entirely on absolute temperature control, thus stabilizing the taste of the cooked rice.

[0079] <Modification 2> An example of a modified embodiment of the present disclosure will be described below. Note that parts that can be configured similarly to the above embodiment will not be explained here.

[0080] In the modified example 2, the control unit 7 controls the heating unit 5 such that, at least in part of the rice cooking process, the amount of heating per unit time decreases as the temperature detected by the temperature detection unit 6 rises.

[0081] In the boiling maintenance step of the above embodiment, the control unit 7 controls the heating unit 5 to heat the pot 3 and continues the process until all the water in the pot 3 is gone and the temperature detected by the temperature detection unit 6 is above the boiling point of water (for example, 130°C). On the other hand, in the modified example 2, for example, in the boiling maintenance step, heating is performed such that the amount of heating per unit time by the heating unit 5 decreases as the temperature of the pot 3 rises.

[0082] At this time, the control unit 7 may change the amount of heating per unit time by the heating unit 5 based on the difference between the target temperature (for example, 130°C), which is the target value for the temperature rise of the process, and the temperature detected by the temperature detection unit 6.

[0083] For example, the control unit 7 controls the heating unit 5 so that the amount of heating per unit time by the heating unit 5 changes in proportion to the difference between the temperature detected by the temperature detection unit 6 at that time and the target temperature (proportional control). Here, the control unit 7 does not need to continuously change the amount of heating per unit time by the heating unit 5, but may perform the above control at predetermined intervals to change the amount of heating per unit time in steps.

[0084] The amount of heating per unit time may be changed by altering the ratio (duty cycle) between the power supply time to the heating coil and the stop time. Alternatively, it may be changed by altering the power supplied to the heating unit 5.

[0085] Furthermore, the control by the control unit 7 to change the amount of heating per unit time of the heating unit 5 is not limited to the proportional control (P control) described above, but may also be proportional-integral control (PI control) or proportional-integral-derivative control (PID control), etc.

[0086] Furthermore, the control to change the amount of heat per unit time of the heating unit 5 described above does not need to be performed throughout the entire process of the rice cooking process, but may be performed in part of at least one process. In other words, in the case of the boiling maintenance process described above, it is not necessary to perform the control to change the amount of heat per unit time of the heating unit 5 throughout the entire boiling maintenance process, but the control to change the amount of heat per unit time of the heating unit 5 may be started when certain conditions are met (for example, when a predetermined temperature is reached or when a predetermined time has elapsed since the start of the process).

[0087] By controlling the amount of heat per unit time of the heating unit 5 as described above, it is possible to prevent overheating in each step of the rice cooking process and reduce the risk of the rice burning.

[0088] By appropriately combining any embodiment or modification from the various embodiments or modifications described above, the effects of each can be achieved. Furthermore, combinations of embodiments with each other, combinations of examples with each other, and combinations of embodiments with examples are possible, as well as combinations of features from different embodiments or examples.

[0089] While this disclosure is adequately described in relation to preferred embodiments with reference to the accompanying drawings, various variations and modifications will be obvious to those skilled in the art. Such variations and modifications should be understood to be included within the scope of this disclosure as defined by the attached claims.

[0090] <Overview of Embodiments> [Item 1] A pot containing water and rice, The main body is provided with a bottomed cylindrical pot storage section in which the aforementioned pot is stored, The main body is provided with an annular inner coil that induces heating around the central part of the bottom of the pot, In the main body, an annular outer coil is provided outside the inner coil in a plan view as seen from the depth direction of the pot storage section, and induces heating of the outer edge of the bottom of the pot, A control unit that adjusts the first power supplied to the inner coil and the second power supplied to the outer coil, and controls the inner coil and the outer coil, Equipped with, The control unit, when supplying power to both the inner coil and the outer coil, changes the ratio of the first power to the second power according to the amount of rice being cooked. Rice cooker.

[0091] [Item 2] At least a portion of the outer coil is located above the inner coil in the depth direction. The control unit is configured to perform a preheating process that heats the food to be cooked and maintains it at the preheating temperature. The control unit controls the inner coil and the outer coil in the preheating step such that the ratio of the second power to the first power is smaller when cooking the minimum amount of rice than when cooking the maximum amount of rice. The rice cooker listed in item 1.

[0092] [Item 3] The rice cooker according to item 2, wherein the control unit controls the inner coil and the outer coil in the preheating step such that the second power becomes less than or equal to the first power when cooking the minimum amount of rice, and the second power becomes greater than the first power when cooking the maximum amount of rice.

[0093] [Item 4] The control unit is configured to perform a steaming process for steaming rice, The control unit controls the inner coil and the outer coil in the steaming process such that the ratio of the second power to the first power is smaller when cooking the minimum amount of rice than when cooking the maximum amount of rice. A rice cooker listed in one of items 1-3.

[0094] [Item 5] The rice cooker according to item 4, wherein the control unit controls the inner coil and the outer coil such that, in the steaming process, the second power becomes less than or equal to the first power when cooking the minimum amount of rice, and the second power becomes greater than the first power when cooking the maximum amount of rice.

[0095] [Item 6] The control unit, A first power adjustment unit for adjusting the first power, A second power adjustment unit, which is different from the first power adjustment unit, adjusts the second power independently of the first power, It has, The first power adjustment unit and the second power adjustment unit are inverters, A rice cooker listed in one of items 1-5.

[0096] [Item 7] The rice cooker according to item 6, wherein the control unit controls the first power adjustment unit and the second power adjustment unit so that the sum of the first power and the second power is less than or equal to a predetermined value.

[0097] <Summary of Variation 1> [Item 1] A pot and A heating unit for heating the aforementioned pot, A temperature detection unit for detecting the temperature of the pot, Control unit and Equipped with, The temperature detection unit includes a first temperature detection unit and a second temperature detection unit, which are provided at different locations from each other. The control unit controls the heating unit to execute a rice cooking process including the first and second steps. The control unit controls the heating unit to terminate the first step or start the second step when the first temperature detection unit detects a predetermined temperature, and to terminate the second step when the temperature detected by the second temperature detection unit rises to a predetermined temperature from the time of termination of the first step. Rice cooker.

[0098] [Item 2] The rice cooker according to item 1, wherein at least one of the above-described first temperature detection unit and the above-described second temperature detection unit is a bottom temperature sensor for detecting the bottom temperature of the pot.

[0099] [Item 3] The rice cooker according to item 1, wherein at least one of the first temperature detection unit and the second temperature detection unit is a lid temperature sensor that detects the temperature above the pot.

[0100] [Item 4] The first step mentioned above is a heating step, The second step is a boiling maintenance step, The above-described temperature detection unit is a lid temperature sensor, The above-described temperature detection unit is a bottom temperature sensor, The control unit controls the heating unit so as to terminate the heating step when the lid temperature sensor detects a predetermined temperature, and terminate the boiling maintenance step when the temperature detected by the bottom temperature sensor rises above a predetermined temperature above the temperature at the end of the heating step. The rice cooker listed in item 1.

[0101] <Summary of Variation 2> [Item 1] A pot and A heating unit for heating the aforementioned pot, A temperature detection unit for detecting the temperature of the pot, Control unit and Equipped with, The control unit controls the heating unit to perform a rice cooking process that includes at least a preheating step, a temperature-raising step, a boiling maintenance step, and a steaming step. The control unit controls the heating unit in at least one step of the rice cooking process such that the amount of heating per unit time decreases as the temperature detected by the temperature detection unit rises. Rice cooker.

[0102] [Item 2] The rice cooker according to item 1, wherein in at least one of the steps, the control unit changes the amount of heating per unit time according to the temperature detected by the temperature detection unit at predetermined intervals, thereby controlling the heating unit so that the amount of heating per unit time decreases as the temperature detected by the temperature detection unit rises.

[0103] [Item 3] In at least one of the steps, a target temperature is set. The control unit controls the heating unit to change the amount of heating per unit time according to the difference between the temperature detected by the temperature detection unit and the target temperature. The rice cooker listed in item 1.

[0104] [Item 4] The rice cooker according to item 1, wherein the control unit changes the amount of heating per unit time by changing the power supplied to the heating unit.

[0105] [Item 5] The rice cooker according to item 1, wherein the control unit changes the amount of heating per unit time by changing the duty cycle. [Industrial applicability]

[0106] The rice cooker described herein is useful as a rice cooker for both consumer and commercial use because it can improve the taste of rice. [Explanation of symbols]

[0107] 1 Main unit 1A Top opening 1B Hinge section 1C Pot storage section 2 Lid 2A Steam outlet 3 Pot 3A Outer edge 4. Selection Section 5 Heating section 5a Bottom heating coil 5b Bottom external heating coil 6. Temperature detection unit 7 Control Unit 71 Inverter Circuit 72 Inverter Circuit 81 Power connection section 82 Rectifier circuit

Claims

1. A pot containing water and rice, The main body is provided with a bottomed cylindrical pot storage section in which the aforementioned pot is stored, The main body is provided with an annular inner coil that induces heating around the central part of the bottom of the pot, In the main body, an annular outer coil is provided outside the inner coil in a plan view as seen from the depth direction of the pot storage section, and induces heating of the outer edge of the bottom of the pot, A control unit that adjusts the first power supplied to the inner coil and the second power supplied to the outer coil, and controls the inner coil and the outer coil, Equipped with, The control unit, when supplying power to both the inner coil and the outer coil, changes the ratio of the first power to the second power according to the amount of rice being cooked. Rice cooker.

2. At least a portion of the outer coil is located above the inner coil in the depth direction. The control unit is configured to perform a preheating process that heats the food to be cooked and maintains it at the preheating temperature. The control unit controls the inner coil and the outer coil in the preheating step such that the ratio of the second power to the first power is smaller when cooking the minimum amount of rice than when cooking the maximum amount of rice. The rice cooker according to claim 1.

3. The rice cooker according to claim 2, wherein the control unit controls the inner coil and the outer coil in the preheating step such that the second power becomes less than or equal to the first power when cooking the minimum amount of rice, and the second power becomes greater than the first power when cooking the maximum amount of rice.

4. The control unit is configured to perform a steaming process for steaming rice, The control unit controls the inner coil and the outer coil in the steaming process such that the ratio of the second power to the first power is smaller when cooking the minimum amount of rice than when cooking the maximum amount of rice. The rice cooker according to claim 1.

5. The rice cooker according to claim 4, wherein the control unit controls the inner coil and the outer coil such that, in the steaming process, the second power becomes less than or equal to the first power when cooking the minimum amount of rice, and the second power becomes greater than the first power when cooking the maximum amount of rice.

6. The control unit, A first power adjustment unit for adjusting the first power, A second power adjustment unit, which is different from the first power adjustment unit, adjusts the second power independently of the first power, It has, The first power adjustment unit and the second power adjustment unit are inverters, A rice cooker according to any one of claims 1 to 5.

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