Rice cooker

Abstract

To provide a rice cooker capable of cooking chewy rice porridge by providing a difference in hardness between a central part and an outer peripheral part of rice grains.SOLUTION: A rice cooker 10 includes a pot 15, a heating unit 24 for heating the pot 15, a temperature detection unit 50 for detecting a temperature Tda in the pot 15, and a control unit 57 for controlling the heating unit 24 on the basis of a detection result of the temperature detection part 50. The control unit 57 is capable of executing a first rice porridge cooking process including a first preheating step, a first boiling step and a first cooking step, and controls the heating unit 24 in the first preheating step such that the hardness of the central part 1b of cooked rice 1 becomes harder than the hardness of the outer peripheral part 1a.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a rice cooker. [Background technology]

[0002] Patent Document 1 discloses a rice cooker that can cook porridge with different textures (hardness) depending on the cooking state selected by the user. In this rice cooker, the hardness of each grain of cooked porridge is varied by varying the execution time of the preheating process, which allows the rice to absorb water.

[0003] Specifically, when cooking porridge with a hard texture, the preheating process is performed for a shorter time, thereby reducing the amount of water absorbed by the rice. On the other hand, when cooking porridge with a soft texture, the preheating process is performed for a longer time, thereby increasing the amount of water absorbed by the rice. In other words, the texture of the cooked porridge is changed by changing the moisture content of the rice grains. The moisture content (hardness) of the rice grains is roughly uniform from the center to the periphery. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2018-149069 Summary of the Invention [Problem to be solved by the invention]

[0005] Important factors in determining texture include not only the hardness of the rice grains but also their chewiness. The chewiness of rice grains can be achieved by leaving a core in the center, similar to the al dente texture of spaghetti. However, the rice cooker in Patent Document 1 simply varies the duration of the preheating process depending on the selected cooking state, making it difficult to create a difference in hardness between the center and outer periphery of the rice grains. In other words, Patent Document 1 does not take into consideration creating a difference in hardness between the center and outer periphery of the rice grains to cook porridge with a chewy texture.

[0006] To provide a rice cooker capable of providing a difference in hardness between the center and outer periphery of rice grains and cooking porridge with a chewy texture. [Means for solving the problem]

[0007] When cooked, the rice absorbs the water in the pot and gelatinizes. Gelatinization means that the starch contained in the rice becomes pasty, and this starch contributes to the taste (sweetness). Gelatinization requires moisture and temperature (for example, 60°C or higher). In a typical rice cooker, the control unit controls the heating unit based on the detection results of the temperature detection unit so that the rice absorbs water during the preheating process and gelatinizes during the boiling process.

[0008] When cooked rice with insufficient water absorption is heated to the gelatinization temperature, water absorption and gelatinization proceed simultaneously. At this time, water absorption and gelatinization proceed from the outer periphery of the cooked rice to the center, and not only the water in the pot but also the moisture contained in the center of the cooked rice is used for gelatinization of the outer periphery. As a result, the center of the cooked rice has insufficient moisture, making gelatinization difficult, and the cooked rice may end up with a core remaining. The present invention is based on this finding.

[0009] One aspect of the present invention provides a rice cooker comprising a pot for containing rice and water, a heating unit for heating the pot, a temperature detection unit for detecting the temperature inside the pot, and a control unit for controlling the heating unit based on the detection result of the temperature detection unit and capable of performing a first porridge cooking process including a first preheating step for causing the rice to absorb the water, a first boiling step for boiling the water, and a first cooking step for cooking the porridge, wherein in the first preheating step the control unit controls the heating unit so that the center of the rice is harder than the outer periphery.

[0010] In the first preheating step, when the rice has not yet fully absorbed water, the control unit heats the pot using the heating unit so that the center of the rice is harder than the outer periphery. This leaves the center of the cooked rice grains hard, creating a difference in hardness between the center and the outer periphery. This allows the rice to be cooked into porridge with a grainy texture that is chewy and different from liquid food.

[0011] In the first preheating step, the control unit preferably adjusts the temperature to maintain a predetermined temperature equivalent to or higher than the temperature at which gelatinization of the cooked rice begins. As a result, the outer periphery of the cooked rice becomes soft due to water absorption and gelatinization, but the center of the cooked rice becomes less moist and gelatinized, making it difficult to gelatinize. In other words, the control unit ensures that the core of the cooked rice remains, like al dente spaghetti. As a result, porridge with a chewy texture and a remaining graininess can be reliably cooked.

[0012] The temperature is preferably adjusted to a temperature lower than the boiling point of the water, which prevents convection from occurring in the pot, thereby promoting water absorption and gelatinization while preventing the outer periphery of the cooked rice from losing its shape.

[0013] The control unit can execute a second porridge cooking process including a second preheating process for absorbing the water into the cooked rice, a second boiling process for boiling the water, and a second cooking process for cooking the porridge, and the temperature control temperature for the second preheating process is preferably below the temperature at which gelatinization of the cooked rice begins. This allows the first porridge cooking process to create a difference in hardness between the inside and outside of the cooked rice grains, ensuring that the porridge still retains a grainy texture. On the other hand, the second porridge cooking process allows the porridge, like a liquid food, to be cooked with almost no grainy texture, without creating a difference in hardness between the inside and outside of the cooked rice grains.

[0014] The input power in the first boiling process is preferably higher than the input power in the second boiling process. The execution time of the first boiling process is preferably shorter than the execution time of the second boiling process. The temperature at which the rice transitions from the first boiling process to the first cooking process is higher than the temperature at which the rice transitions from the second boiling process to the second cooking process. In other words, because the transition temperature in the first boiling process is higher than the transition temperature in the second boiling process, the execution time of the first boiling process is longer than the execution time of the second boiling process when the input power is the same. However, because the input power in the first boiling process is higher than the input power in the second boiling process, the execution time of the first boiling process is shorter than the execution time of the second boiling process. This promotes convection within the pot more than in the second porridge cooking process, thereby reducing overall temperature unevenness. The first porridge cooking process also suppresses gelatinization of the rice to the center, ensuring that porridge with a grainy texture is cooked. On the other hand, in the second porridge cooking process, gelatinization can be promoted all the way to the center of the rice, so porridge with almost no graininess can be reliably cooked.

[0015] The execution time of the first cooking step is preferably shorter than the execution time of the second cooking step. As a result, in the first porridge cooking process, gelatinization up to the center of the rice is suppressed, and porridge with a grainy texture can be reliably cooked. On the other hand, in the second porridge cooking process, gelatinization up to the center of the rice can be promoted, and porridge with almost no grainy texture can be reliably cooked. [Effects of the Invention]

[0016] In the present invention, a difference in hardness is provided between the center and outer periphery of the rice grains, making it possible to cook porridge that is chewy. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a rice cooker according to an embodiment of the present invention. [Figure 2] Figure 1 shows a block diagram of the rice cooker. [Figure 3] Conceptual diagram of a grain of rice. [Figure 4] Time chart for normal porridge cooking process. [Figure 5] Time chart for cooking porridge with distinct grains. [Figure 6] A diagram showing the state of rice grains at the end of the preheating process of normal porridge cooking. [Figure 7] A diagram showing the state of rice grains at the end of the preheating process of the rice porridge cooking process. [Figure 8] 10 is a flowchart of a normal porridge cooking process. [Figure 9] Continuing from Figure 8, this flowchart is a continuation of Figure 8. [Figure 10] 10 is a flowchart of the process for cooking porridge with distinct grains. [Figure 11] Continuing from Figure 10, this flowchart is a continuation of the flowchart shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] 1, a rice cooker 10 according to an embodiment of the present invention includes a rice cooker pot (pot) 15, a rice cooker main body 20, and a lid 30. The rice cooker 10 further includes an IH coil (heating unit) 24, a pot temperature sensor (temperature detection unit) 50, a lid temperature sensor (temperature detection unit) 51, and a control unit 57 (see FIG. 2).

[0020] 2, control unit 57 controls IH coil 24 based on temperatures Tda and Tdb detected by temperature sensors 50 and 51 in accordance with a predetermined program, and cooks rice contained in rice cooker pot 15 (rice cooking process). This rice cooking process includes not only a normal rice cooking process in which rice is cooked until all the water set in rice cooker pot 15 is gone (dry-up), but also a porridge cooking process in which porridge with remaining moisture is cooked.

[0021] In this embodiment, it is possible to cook regular porridge (whole porridge), which is so soft that the cooked rice grains lose their shape, and chewy porridge, which leaves the rice grains hard in the center, using the same amount of water.

[0022] Hereinafter, the configurations of the rice cooker pot 15, rice cooker body 20, and lid 30 will be specifically described with reference to FIG.

[0023] The rice cooker pot 15 is cylindrical with a bottom and has a circular shape when viewed in the direction of the axis A. The rice cooker pot 15 is made of a magnetic material and is formed by pressing or casting. The inner surface of the rice cooker pot 15 is provided with a water level line 16 for regular rice cooking and a water level line 17 for porridge. The maximum capacity for regular rice cooking using the rice cooker pot 15 of this embodiment is 5.5 cups, and the water level line 16 has marks corresponding to 0.5 cup to 5.5 cups. The maximum capacity for porridge using this rice cooker pot 15 is 1.5 cups, and the water level line 17 has marks corresponding to 0.5 cup to 1.5 cups. For the same capacity, the amount of water required to cook porridge is greater than the amount of water required to cook regular rice. However, the maximum capacity for regular rice cooking using the rice cooker pot 15 may be 10 cups.

[0024] The rice cooker main body 20 has an exterior body 21 with a hinge connection shaft 22 on the back, which is located on the right side in Figure 1. The exterior body 21 has a cylindrical storage section 23 with a bottom that detachably stores the rice cooker pot 15. By placing the rice cooker pot 15 inside the storage section 23, the axis of the storage section 23 and the axis A of the rice cooker pot 15 coincide with each other.

[0025] An IH coil 24 is disposed on the outer surface of the housing 23, i.e., between the exterior body 21 and the housing 23. The IH coil 24 is configured with multiple windings wound in an annular shape, and when a high-frequency current is passed through it, an eddy current is generated, which inductively heats the rice cooker pot 15. A holder 25 holding a ferrite core 26 is disposed on the outside of the IH coil 24. The holder 25 holds the IH coil 24 between the housing 23 and the IH coil 24.

[0026] The lid body 30 is rotatably attached to the hinge connection shaft 22 of the exterior body 21 and opensably covers the opening of the rice cooker pot 15. The lid body 30 comprises a lid main body 31 and a lid cover 32, each made of resin. A heat sink 33 that covers the opening of the rice cooker pot 15 is attached to the inner surface of the lid main body 31 facing the rice cooker pot 15 (the lower side in Figure 1). A metal inner lid 34 that closes the opening of the rice cooker pot 15 is attached to the heat sink 33. The inner lid 34 is equipped with a sealing member 35 that seals against the inner surface of the rice cooker pot 15. A lid heater 36 is disposed on the upper surface of the heat sink 33. The lid heater 36 heats the inner lid 34 via the heat sink 33, evaporating dew that has adhered to the inner lid 34.

[0027] An exhaust passage 40 is formed in the lid body 30. The exhaust passage 40 exhausts steam generated inside the rice cooker pot 15 due to the pressure inside the rice cooker pot 15 increased by heating. An inlet section 41 of the exhaust passage 40 is defined by the heat sink 33, the inner lid 34, and an endless sealing member 42. A vent hole 43 that forms the entrance to the exhaust passage 40 is provided on the inside of the sealing member 42 of the inner lid 34. A steam port set 44, which is the outlet section of the exhaust passage 40, has an exhaust port 45 that is open to the outside and is connected to the inlet section 41 by being attached to the lid cover 32.

[0028] The rice cooker 10 configured in this manner is equipped with a pot temperature sensor 50 and a lid temperature sensor 51 to detect the temperature inside the rice cooker pot 15. In addition, a liquid crystal panel (display unit) 52 and a plurality of switches (input unit) 53 are attached to the front side located on the left side in FIG.

[0029] Both the pot temperature sensor 50 and the lid temperature sensor 51 are composed of thermistors. The pot temperature sensor 50 is positioned to penetrate the container 23 so as to contact the outer surface of the rice cooker pot 15 and detects the temperature of the rice cooker pot 15. The temperature of the rice cooker pot 15 correlates with the temperatures of the rice and water inside. Therefore, by detecting the temperature of the rice cooker pot 15 with the pot temperature sensor 50, the temperatures of the rice and water inside the rice cooker pot 15 can be determined. The lid temperature sensor 51 is positioned to penetrate the lid body 31 so as to contact the outer surface of the heat sink 33 and detects the temperature of the heat sink 33. The temperature of the heat sink 33 correlates with the temperature of the inlet section 41, which corresponds to the temperature inside the rice cooker pot 15. Therefore, by detecting the temperature of the heat sink 33 with the lid temperature sensor 51, the temperatures of the rice and water inside the rice cooker pot 15 can be determined. However, the lid temperature sensor 51 may also be a steam sensor that penetrates the inner lid 33 and detects the steam temperature inside the inlet section 41. In addition to the lid temperature sensor 51 that detects the temperature of the inner lid 33, a steam sensor may also be used.

[0030] The LCD panel 52 is located at the top front of the rice cooker body 20 and displays the selected rice cooking menu and the current operating status. However, the LCD panel 52 may also be formed on the top surface of the lid 30, and its location can be changed as needed.

[0031] The rice cooking menus include "white rice," "quick white rice," "mixed rice," "porridge," "brown rice," and "multigrain rice." The white rice menu also includes regular rice cooking menus with different textures, such as "soft," "normal," and "hard." The porridge menu includes porridge menus with different textures, such as "regular porridge" and "grainy porridge."

[0032] The multiple switches 53 are each configured, for example, by tactile switches, and are arranged around the liquid crystal panel 52. The multiple switches 53 include a menu switch for selecting a rice cooking menu, a rice cooking switch for executing the rice cooking process, a keep-warm switch for executing the keep-warm process, a timer switch for cooking rice at a desired time, and a cancel switch for canceling (ending) the rice cooking process, the keep-warm process, and the selected state.

[0033] A control board 55 is disposed on the front side of the rice cooker main body 20, which is located on the left side in Fig. 1. As shown in Fig. 2, the control board 55 is provided with an inverter circuit 56 and a control unit 57. The lid heater 36, temperature sensors 50 and 51, the LCD panel 52, multiple switches 53, and the inverter circuit 56 are connected to the control unit 57. The IH coil 24 is also connected to the control unit 57 via the inverter circuit 56.

[0034] The control unit 57 is composed of one or more microcomputers and other electronic devices. The control unit 57 is equipped with a memory 58 and a timer 59. The memory 58 stores programs for executing the rice cooking process and the keep-warm process, as well as set values ​​(temperature, time, etc.) used in the programs. The timer 59 measures the execution time of each step of the rice cooking process and the keep-warm process.

[0035] The control unit 57 controls the IH coil 24 and the lid heater 36 based on the detection results Tda and Tdb of the temperature sensors 50 and 51 in response to the user's operation of the switch 53, and performs the rice cooking process. As described above, the rice cooking process includes not only the normal rice cooking process in which rice is cooked until the water set in the rice cooker pot 15 is used up, but also a porridge cooking process in which porridge with remaining moisture is cooked.

[0036] (Normal rice cooking process) In the normal rice cooking process, the control unit 57 heats the rice cooker pot 15 using the IH coil 24 based on the detected temperatures Tda and Tdb obtained from the detection results of the temperature sensors 50 and 51, and performs a preheating process, a medium-heating process, a boiling maintenance process, and a steaming process in this order to cook the rice in the rice cooker pot 15.

[0037] During the preheating process, the control unit 57 operates the IH coil 24 to regulate the temperature so that the temperature Tda detected by the pot temperature sensor 50 remains at a predetermined preheating temperature, promoting the absorption of water into the rice placed in the rice cooker pot 15. When a predetermined preheating time has elapsed, the control unit 57 ends the preheating process. Here, the preheating temperature is, for example, 40°C. When the temperature of the rice cooker pot 15 is 40°C, the temperature of the rice and water in the rice cooker pot 15 is approximately 50°C. This temperature of 50°C is lower than the temperature Ta (for example, 60°C) at which rice begins to gelatinize.

[0038] In the intermediate boiling step, the control unit 57 heats the rice cooker pot 15 with higher power (for example, 100% of the rated power) than in the preheating step using the IH coil 24 so that the water in the rice cooker pot 15 boils. The control unit 57 also determines the rice cooking capacity set in the rice cooker pot 15 based on the rate of increase in the temperature Tda detected by the pot temperature sensor 50. When the temperature Tdb detected by the lid temperature sensor 51 reaches a predetermined transition temperature (for example, 60°C), the control unit 57 ends the intermediate boiling step.

[0039] In the boiling maintenance step, the control unit 57 controls the temperature of the rice cooker 15 using the IH coil 24 at a lower output than in the medium boiling step so as to maintain the boiling temperature, and removes the water from the rice cooker 15. When the temperature Tda detected by the pot temperature sensor 50 indicates a predetermined dry-up temperature (for example, 110°C), the control unit 57 ends the boiling maintenance step.

[0040] In the soaking process, the control unit 57 controls the temperature of the rice cooker 15 using the IH coil 24 at a lower output than in the preheating process, and steams the cooked rice. Also, in the soaking process, the control unit 57 heats the inner lid 34 using the lid heater 36, and evaporates dew that has adhered to the inner lid 34. When the soaking time determined according to the rice cooking volume determined in the middle-heating process has elapsed, the control unit 57 ends the soaking process.

[0041] (Porridge cooking process) The porridge cooking process by the control unit 57 includes a normal porridge cooking process (second porridge cooking process) and a grain-standing porridge cooking process (first porridge cooking process).

[0042] In the normal porridge cooking process, the control unit 57 executes the preheating process (second preheating process), the medium boiling process (second boiling process), the cooking process (second cooking process), and the soaking process (second soaking process) in this order, gelatinizing the entire rice grain from the center to the outer periphery, and cooking porridge (whole porridge) with almost no graininess.

[0043] In the grain-standing porridge cooking process, the control unit 57 executes the preheating process (first preheating process), the medium boiling process (first boiling process), the cooking process (first cooking process), and the soaking process (first soaking process) in this order, and by gelatinizing the outer periphery of the rice grain while not gelatinizing the center of the rice grain, the porridge is cooked with a grainy texture (core). The center of the rice grain means the area within approximately 1 mm of the rice grain's dimension in the minor axis direction, which is approximately 2 mm. In other words, it means the area that is 50% or less of the rice grain's dimension in the minor axis direction.

[0044] Here, the principles of water absorption and gelatinization of cooked rice 1 will be described with reference to FIG.

[0045] During the porridge cooking process, the rice 1 absorbs the water in the rice cooker pot 15 and undergoes gelatinization. Gelatinization means that the starch contained in the rice 1 becomes pasty, and this starch contributes to the taste (sweetness). Gelatinization requires moisture and a temperature Ta (60°C or higher).

[0046] In the preheating step of the normal porridge cooking process, the temperature of the cooked rice 1 is controlled at a temperature Tpa that is lower than the gelatinization temperature Ta. As a result, as shown by the thick solid line in Figure 3, water absorption Waa into the cooked rice 1 progresses gradually from the outer periphery 1a to the center 1b. Then, in the middle-steaming step of the normal porridge cooking process, the cooked rice 1 is heated to a temperature higher than the gelatinization temperature Ta. As a result, the cooked rice 1 is gelatinized from the outer periphery 1a to the center 1b.

[0047] On the other hand, in the rice porridge cooking process, the temperature of the cooked rice 1 is controlled to a temperature Tpb, which is higher than the gelatinization temperature Ta, during the preheating process. In other words, in the rice porridge cooking process, cooked rice 1 with insufficient water absorption is heated to a temperature higher than the gelatinization temperature ta. As a result, in the rice porridge cooking process, water absorption and gelatinization proceed simultaneously during the preheating process. At this time, water absorption and gelatinization proceed from the outer periphery 1a of the cooked rice 1 to the center 1b. However, gelatinization of the outer periphery 1a requires not only the absorption of water (water absorption Wab) in the rice cooker 15, as shown by the thin solid line in Figure 3, but also the moisture Wc contained in the center 1b of the cooked rice 1 itself, as shown by the dashed line in Figure 3. As a result, the moisture Wc in the center 1b of the cooked rice 1 becomes insufficient, making gelatinization difficult. Therefore, the cooked rice grains may have a core remaining in the center 1b.

[0048] Next, the normal rice porridge cooking process and the grainy rice porridge cooking process will be specifically described with reference to Figures 4 and 5. Note that Figures 4 and 5 are both time charts for cooking 1 cup of rice porridge using rice cooker 10 with a maximum capacity of 5.5 cups for the normal rice cooking process.

[0049] (Preheating process) In the preheating process, the control unit 57 operates the IH coil 24 to regulate the temperature inside the rice cooker pot 15 so that the temperature Tda detected by the pot temperature sensor 50 is maintained at the set temperature control temperatures Tpa and Tpb, whether cooking normal porridge or grainy porridge. This causes the rice placed inside the rice cooker pot 15 to absorb water. When the set execution times tpa and tpb have elapsed, the control unit 57 ends the preheating process. More specifically, this is as follows.

[0050] The controlled temperatures Tpa and Tpb in the preheating process differ between the normal porridge cooking process and the loose-grained porridge cooking process. The controlled temperature Tpb in the loose-grained porridge cooking process is set higher than the controlled temperature Tpa in the normal porridge cooking process. Here, the temperature Ta at which cooked rice gelats is 60°C or higher, as described above. A cooked rice temperature of 60°C corresponds to 45°C at the temperature Tda detected by the pot temperature sensor 50, which corresponds to the temperature of the heated rice cooker pot 15. In contrast, the controlled temperature Tpa in the normal porridge cooking process is set to 40°C at the temperature Tda detected by the pot temperature sensor 50. In other words, the controlled temperature Tpa in the normal porridge cooking process is set below the temperature Ta at which cooked rice gelats. On the other hand, the controlled temperature Tpb in the loose-grained porridge cooking process is set to a temperature range of 60°C or higher and 70°C or lower at the temperature Tda detected by the pot temperature sensor 50. In other words, the temperature control temperature Tpb for the grainy porridge cooking process is set to a temperature range above the temperature Ta at which rice gelats and below the temperature at which water boils (100°C), and in this embodiment is set to 60°C.

[0051] The input power Ppa and Ppb in the preheating process are set to the same for both the normal porridge cooking process and the stand-up porridge cooking process, and in this embodiment are set to 900 W. During the preheating process, the power supply rates Rpa and Rpb after the temperature has been raised to the controlled temperatures Tpa and Tpb are set to the same for both the normal porridge cooking process and the stand-up porridge cooking process, and in this embodiment are on / off controlled with an on-off cycle of 8 seconds out of 15 seconds. However, the input power Ppa for the normal porridge cooking process and the input power Ppb for the stand-up porridge cooking process, and the power supply rates Rpa and Rpb for the normal porridge cooking process may be different.

[0052] The execution times tpa and tpb of the preheating process are set to the same for both the normal porridge cooking process and the grain-stiffening porridge cooking process, and are set to 13 minutes for 1 cup of cooked rice. More specifically, in the preheating process, the times tpa2 and tpb2 for maintaining the temperature control temperatures Tpa and Tpb after reaching the temperature control temperatures Tpa and Tpb differ between the normal porridge cooking process and the grain-stiffening porridge cooking process. Because the temperature control temperature Tpb for the grain-stiffening porridge cooking process is higher than the temperature control temperature Tpa for the normal porridge cooking process, the time tpb1 for reaching the temperature control temperature Tpb for the grain-stiffening porridge cooking process is slower than the time tpa1 for reaching the temperature control temperature Tpa in the normal porridge cooking process. Therefore, the time tpb2 during which the temperature is maintained at the controlled temperature Tpb in the grainy porridge cooking process is made shorter than the time tpa2 during which the temperature is maintained at the controlled temperature Tpa in the normal porridge cooking process, and the overall preheating execution times tpa and tpb are made the same.

[0053] On the other hand, in the preheating process, the times tpa1 and tpb1 for reaching the controlled temperatures Tpa and Tpb become faster as the rice cooking capacity decreases and slower as the rice cooking capacity increases, in both the normal porridge cooking process and the grainy porridge cooking process. However, the times tpa2 and tpb2 after reaching the controlled temperatures Tpa and Tpb are set constant regardless of the rice cooking capacity. Therefore, the overall preheating execution times tpa and tpb become faster as the rice cooking capacity decreases and slower as the rice cooking capacity increases, in both the normal porridge cooking process and the grainy porridge cooking process.

[0054] (Middle packing process) In the intermediate-heating step, the control unit 57 heats the rice cooker pot 15 with input powers Pba and Pbb, which are greater than those used in the preheating step, using the IH coil 24 so that the water in the rice cooker pot 15 boils, whether cooking regular porridge or chunky porridge. The control unit 57 also determines the rice cooking capacity set in the rice cooker pot 15 based on the rate of increase in the temperature Tda detected by the pot temperature sensor 50. When the temperature Tdb detected by the lid temperature sensor 51 reaches the predetermined transition temperatures Tba and Tbb through heating, the control unit 57 ends the intermediate-heating step. More specifically, this is as follows:

[0055] The input power Pba, Pbb, power conduction rates Rba, Rbb, and transition temperatures Tba, Tbb for the intermediate cooking process are all different between the normal porridge cooking process and the standing grain porridge cooking process. The input power Pbb for the standing grain porridge cooking process is set higher than the input power Pba for the normal porridge cooking process. The power conduction rate Rbb for the standing grain porridge cooking process is set higher than the power conduction rate Rba for the normal porridge cooking process. The transition temperature Tbb for the standing grain porridge cooking process is set higher than the transition temperature Tba for the normal porridge cooking process.

[0056] Here, in the intermediate-pumping step, the transition temperature Tbb of the standing grain porridge cooking process is higher than the transition temperature Tba of the normal porridge cooking process. Therefore, when the input power is the same, the execution time tbb of the standing grain porridge cooking process is longer than the execution time tba of the normal porridge cooking process. However, in this embodiment, the input power Pbb of the standing grain porridge cooking process is set higher than the input power Pba of the normal porridge cooking process, and the power supply rate Rbb of the standing grain porridge cooking process is set higher than the power supply rate Rba of the normal porridge cooking process. Therefore, the time required to raise the temperature to the transition temperature Tbb in the standing grain porridge cooking process (execution time tbb) is shorter than the time required to raise the temperature to the transition temperature Tba in the normal porridge cooking process (execution time tba). In other words, the intermediate-pumping step of the standing grain porridge cooking process is set to input higher power for a shorter period of time than the intermediate-pumping step of the normal porridge cooking process.

[0057] In the middle-pumping step, for the normal porridge cooking process, the initial input power Pba is set to 1100 W, and when the temperature Tdb detected by the lid temperature sensor 51 indicates a threshold value Tx (for example, 50°C), the input power Pba is set to be reduced to 1000 W. On the other hand, for the grainy porridge cooking process, the input power Pbb is set in a range higher than 1100 W and equal to or lower than 100% of the rated power (1200 W in this embodiment), and is set to 1200 W in this embodiment.

[0058] In the intermediate cooking step, the power supply rate Rba for the normal porridge cooking process is controlled to repeat a cycle of 12 seconds on for 15 seconds. On the other hand, the power supply rate Rbb for the grainy porridge cooking process is set to a cycle of 15 seconds or less but longer than 12 seconds, and in this embodiment, it is controlled to repeat a cycle of 13 seconds on for 15 seconds.

[0059] In the intermediate-puffing process, the temperature (transition temperature) Tba at which the process transitions from the intermediate-puffing process to the final cooking process in the normal porridge cooking process is set to 60°C, which is the temperature Tdb detected by the lid temperature sensor 51. On the other hand, the temperature (transition temperature) Tbb at which the process transitions from the intermediate-puffing process to the final cooking process in the grain-stiffening porridge cooking process is set to a range of 60°C to 75°C. If the transition temperature Tbb for the grain-stiffening porridge cooking process is set too low, the volume determination process being performed in parallel may not be completed, and the cooked porridge may have an excessively chewy texture due to insufficient gelatinization of the rice. If the transition temperature Tbb for the grain-stiffening porridge cooking process is set too high, overflow may occur, and the cooked porridge may have an excessively chewy texture due to excessive gelatinization of the rice. Therefore, the transition temperature Tbb for the grain-stiffening porridge cooking process is preferably set within the above-specified range, and in this embodiment, it is set to 70°C.

[0060] On the other hand, as mentioned above, the total execution time tba and tbb of the intermediate porridge cooking process is shorter for the porridge with standing grains cooking process because the input power Pbb for the porridge with standing grains cooking process is higher than the input power Pba for the normal porridge cooking process, and the power supply rate Rbb for the porridge with standing grains cooking process is higher than the power supply rate Rba for the normal porridge cooking process.In other words, the input power Pbb, power supply rate Rbb, and transition temperature Tba for the porridge with standing grains cooking process are set so that the execution time tbb for the porridge with standing grains cooking process is shorter than the execution time tba for the normal porridge cooking process.Note that, as with the preheating process, the execution times tba and tbb of the intermediate porridge cooking process become shorter as the rice cooking capacity decreases and longer as the rice cooking capacity increases.

[0061] (Cooking process) In the cooking process, the control unit 57 controls the temperature of the rice cooker 15 using the IH coil 24 at input powers Pca and Pcb that are lower than those in the medium-heating process so that the water in the rice cooker 15 maintains boiling temperature, whether cooking regular porridge or grainy porridge. When the execution times tca and tcb determined according to the capacity determined in the medium-heating process have elapsed, the control unit 57 ends the cooking process. More specifically, this is as follows.

[0062] The execution times tca and tcb of the cooking process differ between the normal porridge cooking process and the grain-loose porridge cooking process. The execution time tcb of the grain-loose porridge cooking process is set shorter than the execution time tca of the normal porridge cooking process. The execution time tca of the normal porridge cooking process is set to 30 minutes when the amount of cooked rice is 1 cup. On the other hand, the execution time tcb of the grain-loose porridge cooking process is set to between 7 and 12 minutes. If the execution time tcb of the grain-loose porridge cooking process is set too short, the center of the rice will undergo too little gelatinization, and hard portions may remain on the outer periphery of the rice grains. If the execution time tcb of the grain-loose porridge cooking process is set too long, the center of the rice will undergo too much gelatinization, and the rice grains in the cooked porridge will have an insufficient texture. Therefore, it is preferable to set the execution time tcb of the rice porridge cooking process within the range specified above, and it is set to 8 minutes when cooking 1 cup of rice.

[0063] The input powers Pca and Pcb for the cooking process are set to the same for both the normal porridge cooking process and the porridge with standing grains cooking process, but the power supply rates Rca and Rcb are partially different between the normal porridge cooking process and the porridge with standing grains cooking process. Specifically, the power supply rate Rcb for the porridge with standing grains cooking process is always set to be constant during the execution time tcb, but the power supply rate Rca for the normal porridge cooking process is set to be high only during part of the execution time tca.

[0064] In the cooking process, the input power Pca for the normal porridge cooking process and the input power Pbb for the grain-stabilized porridge cooking process are both set to 800 W. However, the input power Pca for the normal porridge cooking process and the input power Pbb for the grain-stabilized porridge cooking process may be different.

[0065] In the cooking process, for the normal porridge cooking process, the initial current rate Rca during the execution time tca (2 minutes from the start) is on / off controlled with a cycle of 4 seconds on for 15 seconds, and the remaining current rate Rca during the execution time tca is on / off controlled with a cycle of 2 seconds on for 15 seconds. On the other hand, the current rate RRcb for the grainy porridge cooking process is set to be on / off controlled with a cycle of 2 seconds on for all of 15 seconds during the execution time tcb.

[0066] (Steaming process) In the soaking process, the control unit 57 stops heating the rice cooker pot 15 by the IH coil 24 and steams the cooked porridge. Also, in the soaking process, the control unit 57 heats the inner lid 34 by the lid heater 36 and evaporates dew that has adhered to the inner lid 34. When the execution times tsa and tsb determined according to the rice cooking capacity determined in the middle-steaming process have elapsed, the control unit 57 ends the soaking process.

[0067] The execution times tsa and tsb of the soaking process are set to the same for both the regular porridge cooking process and the grainy porridge cooking process. When the rice volume is 1 cup, the execution times tsa and tsb are both 5 minutes. The execution times tsa and tsb are constant regardless of the volume determined in the middle-steaming process.

[0068] Here, the water absorption state of the rice after the preheating step of the normal porridge cooking process shown in Figure 4 is shown in Figure 6, and the water absorption state and gelatinized state of the rice after the preheating step of the grainy porridge cooking process shown in Figure 5 are shown in Figure 7. The rice shown in Figure 6 after the normal porridge cooking process cannot stand on its own, so it is supported by a support member.

[0069] Since it is difficult to check the water absorption and gelatinization state of cooked rice using colorless, transparent water, water colored with food coloring was used for both the regular porridge cooking process and the grainy porridge cooking process. Because the cooked rice is white and the water is colored red, the parts of the cooked rice with low water content appear lighter, while the parts with high water content appear darker. Furthermore, the gelatinized parts of the cooked rice appear even darker than the parts that have absorbed water.

[0070] Referring to Figures 6 and 7, the degree of shade becomes gradually darker in the following order: the center of the rice shown in Figure 7 after the grain-standing porridge cooking process, the center of the rice shown in Figure 6 after the normal porridge cooking process, the outer periphery of the rice shown in Figure 6 after the normal porridge cooking process, and the outer periphery of the rice shown in Figure 7 after the grain-standing porridge cooking process.

[0071] Referring to Figure 6, it can be seen that the cooked rice after the preheating process of the normal porridge cooking process does not have any parts that are darker than the outer periphery of the cooked rice shown in Figure 7, and there is no gelatinized part. Also, it can be seen that although there is a center part that has not absorbed enough water, most of the rice from the outer periphery to the center has absorbed enough water. Therefore, if the middle-pumping process is subsequently performed and the water is boiled, it can be seen that the rice will absorb enough water from the outer periphery to the center, and the entire cooked rice can be gelatinized. It can be seen that by then performing the cooking process, it is possible to cook porridge with no difference in hardness from the outer periphery to the center.

[0072] In contrast, referring to Figure 7, it can be seen that the outer periphery of the cooked rice after the preheating step of the grain-forming porridge cooking process is the darkest, including the cooked rice shown in Figure 6, and has undergone gelatinization. On the other hand, among the cooked rice shown in Figure 7, most of the rice from the vicinity of the outer periphery to the center is the lightest, including the cooked rice shown in Figure 6, and it can be seen that not only has it not absorbed water, but also that it has too little moisture. Therefore, even if the middle-steaming step is subsequently performed and the water is boiled, it can be seen that the center, which has little moisture, is in a state where gelatinization is difficult. Therefore, it can be seen that even if the cooking step is subsequently performed, a hard part (core) may remain in the center of the cooked rice.

[0073] As described above, in the grain-retaining porridge cooking process, in the preheating step, the cooked rice 1 is heated to a gelatinization temperature Ta or higher so that the hardness of the center 1b becomes harder than the hardness of the outer periphery 1a. In addition, in the middle-steaming step, high power is applied to promote convection, and the cooked rice 1 is heated so as not to lose too much of its graininess. In the cooking step, the cooked rice 1 is heated for only a short time so that the graininess of the cooked rice 1 is not lost too much. Therefore, the center of each rice grain in the cooked porridge remains firm, and it is possible to cook porridge with a graininess and chewiness that is different from liquid food.

[0074] Next, the normal porridge cooking process by the control unit 57 will be described in detail with reference to Figures 8 and 9. In Figures 8 and 9, steps S1 to S4 are the preheating process, steps S5 to S7 are the semi-heating process, steps S8 to S11 are the cooking process, and steps S12 to S13 are the steaming process. In this normal porridge cooking process, the lid heater 36 is turned on immediately after the process starts and turned off immediately before the process ends.

[0075] In the normal porridge cooking process, in step S1, control unit 57 turns on IH coil 24 and operates it at input power Ppa and conduction rate Rpa. Next, in step S2, it waits until temperature Tda detected by pan temperature sensor 50 rises above controlled temperature Tpa. If detected temperature Tda rises above controlled temperature Tpa, in step S3 it controls the on / off of IH coil 24 so that controlled temperature Tpa is maintained based on temperature Tda detected by pan temperature sensor 50. Next, in step S4, it determines whether preheating execution time tpa has elapsed. If preheating execution time tpa has not elapsed, it returns to step S3 and continues to control the on / off of IH coil 24. On the other hand, if preheating execution time tpa has elapsed, it proceeds to step S5.

[0076] In step S5, IH coil 24 is operated at input power Pba and current conduction rate Rba. Subsequently, in step S6, it is determined whether temperature Tdb detected by lid temperature sensor 51 has reached transition temperature Tba. If detected temperature Tdb has not reached transition temperature Tba, the process proceeds to step S7, where it is determined whether detected temperature Tdb has risen to or above threshold value Tx. If detected temperature Tdb has risen to or above threshold value Tx, the process returns to step S5, where input power Pba and current conduction rate Rba of IH coil 24 are changed. If detected temperature Tdb is less than threshold value Tx, the process returns to step S6. On the other hand, if detected temperature Tdb reaches transition temperature Tba in step S6, the process proceeds to step S8.

[0077] In step S8, the IH coil 24 is operated at input power Pca and current conduction rate Rca. Next, in step S9, the IH coil 24 is controlled to be on / off so that the boiling temperature is maintained based on the temperature Tda detected by the pot temperature sensor 50. Next, in step S10, it is determined whether the cooking execution time tca has elapsed. If the cooking execution time tca has not elapsed, the process proceeds to step S11, where it is determined whether two minutes have elapsed since the start of the cooking process. If two minutes have elapsed, the process returns to step S8, where the input power Pba and current conduction rate Rba of the IH coil 24 are changed. If two minutes have not elapsed, the process returns to step S9, where the on / off control of the IH coil 24 continues. On the other hand, if the cooking execution time tca has elapsed in step S10, the process proceeds to step S12.

[0078] In step S12, the IH coil 24 is turned off, and then in step S13, the process waits until the soaking execution time tsa has elapsed, and when the soaking execution time tsa has elapsed, the normal porridge cooking process is terminated.

[0079] Next, the process of cooking porridge with standing grains performed by the control unit 57 will be described in detail with reference to Figures 10 and 11. In Figures 10 and 11, steps S20 to S23 are the preheating process, steps S24 and S25 are the intermediate cooking process, steps S26 to S28 are the cooking process, and steps S29 to S30 are the steaming process. In this porridge with standing grains cooking process, the lid heater 36 is also turned on immediately after the start and turned off immediately before the end.

[0080] In the grainy porridge cooking process, in step S20, control unit 57 turns on IH coil 24 and operates it at input power Ppb and conduction rate Rpb. Next, in step S21, the process waits until temperature Tda detected by pan temperature sensor 50 rises above controlled temperature Tpb. Next, when temperature Tda detected by pan temperature sensor 50 rises above controlled temperature Tpb, in step S22, the process controls IH coil 24 to be turned on and off so that controlled temperature Tpb is maintained based on temperature Tda detected by pan temperature sensor 50. Next, in step S23, the process determines whether preheating execution time tpb has elapsed. If preheating execution time tpb has not elapsed, the process returns to step S22 and continues to control IH coil 24 on and off. On the other hand, if preheating execution time tpb has elapsed, the process proceeds to step S24.

[0081] In step S24, IH coil 24 is operated at input power Pbb and conduction rate Rbb. Next, in step S25, the process waits until temperature Tdb detected by lid temperature sensor 51 reaches transition temperature Tbb, and when detected temperature Tdb reaches transition temperature Tbb, the process proceeds to step S26.

[0082] In step S26, IH coil 24 is operated at input power Pcb and conduction rate Rcb. Next, in step S27, IH coil 24 is controlled to be turned on and off so that the boiling temperature is maintained based on the temperature Tda detected by pot temperature sensor 50. Next, in step S28, it is determined whether cooking execution time tcb has elapsed. If cooking execution time tcb has not elapsed, the process returns to step S27 and the on / off control of IH coil 24 continues. On the other hand, if cooking execution time tcb has elapsed in step S28, the process proceeds to step S29.

[0083] In step S29, the IH coil 24 is turned off, and then in step S30, the process waits until the soaking execution time tsb has elapsed, and when the soaking execution time tsb has elapsed, the rice porridge cooking process with distinct grains is terminated.

[0084] The rice cooker 10 configured as above has the following features.

[0085] In the rice porridge cooking process with firm grains, during the preheating step when the rice 1 has not yet absorbed enough water, the control unit 57 heats the rice cooker 15 with the IH coil 24 so that the center 1b of the rice 1 is harder than the outer periphery 1a. This leaves the center of the cooked rice grains hard, creating a difference in hardness between the center and the outer periphery. This allows the rice porridge to be cooked with a grainy texture that is chewy and different from liquid food.

[0086] In the preheating step of the grain-stiffening porridge cooking process, the control unit 57 adjusts the temperature to a predetermined temperature Tpb, which is equal to or higher than the temperature Ta at which gelatinization of the cooked rice 1 begins. As a result, the outer periphery 1a of the cooked rice 1 becomes soft through water absorption and gelatinization, but the center 1b of the cooked rice 1 becomes too dry and is therefore less likely to gelatinize. In other words, the control unit 57 makes the cooked rice grains retain their cores, like spaghetti al dente. As a result, porridge with a chewy texture and a remaining graininess can be reliably cooked.

[0087] The controlled temperature Tpb is lower than the boiling point of water, which prevents convection from occurring within the rice cooker 15. This prevents the outer periphery 1a of the cooked rice 1 from losing its shape and promotes water absorption and gelatinization.

[0088] The temperature control temperature Tpa in the preheating process in the normal porridge cooking process is below the temperature at which gelatinization of cooked rice begins. As a result, in the grain-standing porridge cooking process, a difference in hardness is created between the inside and outside of the cooked rice grains, and porridge with a grainy texture can be reliably cooked. On the other hand, in the normal porridge cooking process, a difference in hardness is not created between the inside and outside of the cooked rice grains, and porridge with almost no grainy texture, like a liquid food, can be reliably cooked.

[0089] The input power Pbb during the intermediate-pumping step in the grain-standing porridge cooking process is higher than the input power Pba during the intermediate-pumping step in the normal porridge cooking process. Therefore, in the grain-standing porridge cooking process, convection within the rice cooker pot 15 is promoted more than in the normal porridge cooking process, thereby reducing overall temperature unevenness. Furthermore, the execution time tbb of the intermediate-pumping step in the grain-standing porridge cooking process is shorter than the execution time tba of the intermediate-pumping step in the normal porridge cooking process. Moreover, the temperature Tbb at which the rice transitions from the intermediate-pumping step to the final cooking step in the grain-standing porridge cooking process is higher than the temperature Tba at which the rice transitions from the intermediate-pumping step to the final cooking step in the normal porridge cooking process. Therefore, in the grain-standing porridge cooking process, gelatinization up to the center 1b of the rice 1 is suppressed, ensuring that porridge with a grainy texture is cooked. On the other hand, in the normal porridge cooking process, gelatinization can be promoted up to the center 1b of the cooked rice 1, so that porridge with almost no graininess can be reliably cooked.

[0090] The execution time tcb of the cooking process in the grain-standing porridge cooking process is shorter than the execution time tca of the cooking process in the normal porridge cooking process. As a result, the grain-standing porridge cooking process can suppress gelatinization up to the center 1b of the cooked rice 1, and can reliably cook porridge with a grainy texture. On the other hand, the normal porridge cooking process can promote gelatinization up to the center 1b of the cooked rice 1, and can reliably cook porridge with almost no grainy texture.

[0091] The present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

[0092] For example, the temperature control temperature Tpb of the preheating process in the grain-stabilized porridge cooking process is not limited to being equal to or higher than the temperature Ta at which gelatinization of rice begins, and it is sufficient that the rice cooker pot 15 is heated by the IH coil 24 so that the hardness of the center 1b of the rice 1 shown in Figure 3 becomes harder than the hardness of the outer periphery 1a.

[0093] The grainy porridge cooking process may not include the soaking step. Of course, the normal porridge cooking process may also not include the soaking step.

[0094] Rice cooker 10 may be a dedicated machine capable of cooking both regular rice porridge and grainy rice porridge, or may be a dedicated machine capable of cooking only grainy rice porridge. In other words, rice cooker 10 may be configured without a regular rice cooking process, or without a regular rice cooking process or regular rice porridge cooking process.

[0095] The basic configuration of the rice cooker pot 15, including the rice cooker pot 15, a heating unit that heats the rice cooker pot 15, and a temperature detection unit that detects the temperature of the rice cooker pot 15, can be modified as needed. In particular, the heating unit may be a heater that directly heats the rice cooker pot 15 instead of the IH coil 24. [Explanation of symbols]

[0096] 1. Rice 1a Outer periphery 1b Center 10. Rice cooker 15 Rice cooker (pot) 16,17 water line 20 Rice cooker body 21 Exterior body 22 Hinge connection axis 23 Storage unit 24 IH coil (heating part) 25 Holder 26 Ferrite core 30 Lid 31 Lid body 32 Lid cover 33 Heat sink 34 Inner lid 35 Sealing material 36 Lid heater 40 Exhaust passage 41 Inlet 42 Sealing material 43 Ventilation 44 Steam Vent Set 45 exhaust port 50 Pot temperature sensor (temperature detection part) 51 Lid temperature sensor 52 LCD panel 53 Switch 55 Control board 56 Inverter circuit 57 Control Unit 58 memory 59 Timer Tda pot detection temperature Tdb Lid detection temperature tpa Normal porridge preheating run time Tpa Normal porridge temperature control temperature Ppa Normal porridge input power Rpa Normal porridge conduction rate tpb Grain-Standing Porridge Preheating Run Time Tpb Grain-Standing Porridge Temperature Control Ppb Grain-forming porridge input power Rpb Grain-standing porridge current rate tba Normal porridge medium pappa running time Tx Normal porridge threshold Pba Normal porridge input power Rba Normal porridge conduction rate Tba Normal porridge medium-sized transition temperature tbb Grain-Standing Porridge Medium Pappa Running Time Pbb Grain-Standing Porridge Input Power Rbb Grain-standing porridge current rate Tba Grain-filled porridge medium-sized transition temperature TCA Regular Porridge Cooking Run Time Pca Normal porridge input power Rca normal porridge conduction rate TCB grain porridge cooking time PCB grain standing porridge input power Rcb Grain-standing porridge current rate TSA Normal porridge soaking time TSB Grain-Standing Porridge Steaming Execution Time

Claims

1. A pot for storing rice and water, A heating unit that heats the pot; a temperature detection unit for detecting the temperature inside the pot; a control unit that controls the heating unit based on the detection result of the temperature detection unit and is capable of executing a first porridge cooking process including a first preheating step of making the rice absorb the water, a first boiling step of boiling the water, and a first cooking step of cooking the porridge; Equipped with In the first preheating step, the control unit controls the heating unit so that the hardness of the center of the cooked rice is harder than the hardness of the outer periphery of the cooked rice.

2. The rice cooker according to claim 1 , wherein in the first preheating step, the control unit controls the temperature so as to maintain a predetermined temperature equivalent to a temperature at which gelatinization of the cooked rice begins or higher.

3. The rice cooker according to claim 2 , wherein the temperature to be adjusted is lower than the boiling point of the water.

4. The control unit is capable of executing a second porridge cooking process including a second preheating step of causing the rice to absorb the water, a second boiling step of boiling the water, and a second cooking step of cooking porridge, The rice cooker according to claim 1 , wherein the controlled temperature in the second preheating step is lower than a temperature at which gelatinization of the cooked rice begins.

5. The rice cooker according to claim 4 , wherein the input power in the first boiling step is higher than the input power in the second boiling step.

6. The rice cooker according to claim 5 , wherein the first boiling step is performed for a shorter period of time than the second boiling step.

7. The rice cooker according to claim 5 , wherein a temperature at which the rice transitions from the first boiling step to the first cooking step is higher than a temperature at which the rice transitions from the second boiling step to the second cooking step.

8. The rice cooker according to claim 4 , wherein the first cooking step is performed for a shorter period of time than the second cooking step.

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