rice cooker

Abstract

To provide a rice cooker capable of improving a sterilization effect while suppressing deterioration of cooking objects due to warming.SOLUTION: A rice cooker includes: a pot for storing cooking objects; a heating part for heating the cooking objects in the pot; and a control part for controlling the heating part so as to perform a warming process to warm the cooking objects. The control part controls the heating part to reduce the temperature of the cooking objects to be less than 60°C in the warming process, and to rise the temperature of the cooking objects to be equal to or more than 65°C when a temperature keeping time predetermined in response to the amount of the cooking objects elapses.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a rice cooker with a keep-warm function. [Background technology]

[0002] A conventional rice cooker of this type is known, for example, from the rice cooker described in Patent Document 1. Patent Document 1 describes that when the temperature drops after cooking, the amount of food in the pot (number of servings) is determined based on the time it takes for the temperature to drop from a first set temperature to a second set temperature and the room temperature. Patent Document 1 also describes that by keeping the food warm by alternately switching between a low temperature (60°C) and a high temperature (92°C), it is possible to sterilize the food while preventing deterioration of the food due to keeping it warm. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-164067 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional rice cookers still have room for improvement in terms of suppressing deterioration of cooked food due to keeping it warm while also improving the sterilization effect.

[0005] Therefore, an object of the present invention is to solve the above problems and to provide a rice cooker that can improve the sterilization effect while suppressing deterioration of heat retention. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention is configured as follows. According to the present invention, a cooking pot includes: a pot for containing food; A heating unit that heats the food in the pot; a control unit that controls the heating unit to perform a heat retention step of keeping the food warm; Equipped with The control unit controls the heating unit to lower the temperature of the food to below 60°C during the keeping-warm process, and then raise the temperature of the food to 65°C or higher after a predetermined temperature maintenance time based on the amount of food has elapsed. [Effects of the Invention]

[0007] According to the present invention, a rice cooker can be provided that can suppress deterioration of cooked food due to keeping it warm while further improving the sterilization effect. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view of a rice cooker according to an embodiment of the present invention. [Figure 2] 2 is a graph showing an example of changes in the temperature of the food being cooked and the temperature detected by the pan temperature sensor in the rice cooker of FIG. 1 during a keep-warm process. [Figure 3] 10 is a graph showing the relationship between the temperature drop time it takes for the temperature detected by the pan temperature sensor to drop from a first temperature to a second temperature, the amount of food being cooked, and the ambient temperature. [Figure 4] 10 is a graph showing an example of setting a controlled temperature relative to an environmental temperature. [Figure 5] 10 is a table showing examples of setting the temperature maintenance time and the second temperature maintenance time in relation to the estimated amount of food to be cooked. [Figure 6] 10 is a graph showing a modified example of changes in the temperature of the food being cooked and the temperature detected by the pan temperature sensor during the keep-warm step in the rice cooker of FIG. [Figure 7] FIG. 1 is a schematic diagram showing changes in the state of bacteria of the genus Bacillus. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that form the basis of the present invention) The present inventors have conducted extensive research to improve the sterilization effect while suppressing deterioration of cooked food due to keeping it warm, and have come to the following findings.

[0010] There are multiple Bacillus bacteria that are found in rice (hereinafter simply referred to as Bacillus bacteria), but their growth is inhibited in temperatures above 65°C. However, Bacillus bacteria are highly heat-resistant in the spore state and are not completely killed even when heated to 100°C. On the other hand, among Bacillus bacteria in the spore state, Bacillus bacteria that have a high growth temperature range germinate in temperatures below 60°C. After germination, the germinated Bacillus bacteria grow into vegetative cells and multiply by repeatedly dividing. Therefore, if the food is kept warm at temperatures below 60°C for a long period of time, the Bacillus bacteria will multiply, causing spoilage and resulting in a deterioration in the taste of the cooked food.

[0011] In response to this, the present inventors conducted extensive research and found that once Bacillus bacteria germinate, their heat resistance decreases and they become more susceptible to death in a temperature environment of 65°C or higher. That is, the present inventors found that the sterilizing effect can be further improved by lowering the temperature of the food to below 60°C, promoting germination for a time predetermined depending on the amount of the food, and then raising the temperature of the food to 65°C or higher. Based on this novel finding, the present inventors arrived at the following invention.

[0012] According to one aspect of the present invention, a rice cooker includes: a pot for containing food to be cooked; A heating unit that heats the food in the pot; a control unit that controls the heating unit to perform a heat retention step of keeping the food warm; Equipped with The control unit controls the heating unit to lower the temperature of the food to less than 60°C in the keeping-warm process, and raise the temperature of the food to 65°C or higher after a predetermined temperature maintenance time depending on the amount of the food has elapsed. It is structured as follows.

[0013] According to this configuration, the temperature of the food is lowered to below 60°C in the keeping-warm step, thereby reducing the amount of heat applied to the food and preventing deterioration of the food due to keeping warm. It also promotes germination of Bacillus bacteria. Furthermore, according to the configuration, the temperature of the food is lowered to below 60°C, and after a predetermined temperature maintenance time based on the amount of food has elapsed, the temperature of the food is raised to 65°C or higher, thereby heating and killing Bacillus bacteria that have germinated and become less heat-resistant. This further improves the sterilization effect.

[0014] When the temperature of the food is raised to 65°C or higher, there is a possibility that some Bacillus bacteria may not be killed but may be partially damaged, as shown in Figure 7. The partially damaged Bacillus bacteria may recover and return to spore form. To kill these Bacillus bacteria, it is necessary to consider not only the time it takes for the bacteria to germinate from a spore state but also the time it takes for the bacteria to recover from the partial damage and return to spore form.

[0015] Therefore, in the keeping-warm step, the control unit may control the heating unit to raise the temperature of the food to 65°C or higher, and then control the heating unit to lower the temperature of the food to less than 60°C and raise the temperature of the food to 65°C or higher after a second temperature maintenance time predetermined according to the amount of the food and longer than the temperature maintenance time has elapsed. With this configuration, the second temperature maintenance time is longer than the temperature maintenance time, taking into account the time it takes for the food to repair partial damage and return to spores, thereby more reliably killing the Bacillus bacteria. This further improves the sterilization effect. Furthermore, compared to when the second temperature maintenance time is shorter than the temperature maintenance time, the amount of heat applied to the food can be reduced, further suppressing deterioration of the food due to keeping warm.

[0016] Furthermore, in the keeping-warm step, the control unit may control the heating unit to raise the temperature of the food to 75° C. or higher after lowering the temperature of the food to less than 60° C. According to this configuration, germinated Bacillus bacteria can be placed in a higher temperature environment, thereby accelerating the death of the germinated Bacillus bacteria and further improving the sterilization effect.

[0017] The rice cooker may further include a pan temperature detector that detects the temperature of the pan, and the control unit may estimate the temperature of the food based on the temperature detected by the pan temperature detector, estimate the amount of the food based on the ambient temperature around the rice cooker and the rate of change in the temperature detected by the pan temperature detector when the temperature of the food is reduced to below 60°C, and control the heating unit based on the estimation result. With this configuration, the temperature of the food is estimated based on the temperature detected by the pan temperature detector, eliminating the need for a device that directly detects the temperature of the food. Furthermore, the amount of food is estimated based on the ambient temperature around the rice cooker and the temperature detected by the pan temperature detector, eliminating the need for a device that directly detects the amount of food.

[0018] The cooking device may also include a lid that can open and close the upper opening of the pot, and a lid detection unit that detects whether the lid is open or closed. The control unit may store the temperature detected by the pot temperature detection unit as the ambient temperature before controlling the heating unit to heat the food in the pot. During the warming process, if a predetermined time has passed without the lid detection unit detecting whether the lid is open or closed after estimating the amount of food, the control unit may correct the ambient temperature based on the temperature detected by the pot temperature detection unit after the predetermined time has passed and the estimated amount of food. With this configuration, even if the ambient temperature changes during the warming process, the amount of food in the pot remains unchanged if the lid is not opened or closed. Therefore, the ambient temperature can be calculated (back-calculated) based on the estimated amount of food and the temperature detected by the pot temperature detection unit. This allows the controlled temperature of the pot temperature sensor to be more appropriately set in response to changes in ambient temperature. Furthermore, even if the amount of food in the pot decreases after the lid is opened or closed, the amount of food can be estimated based on a more accurate ambient temperature. Therefore, it is not necessary to provide a device for directly detecting the amount of food being cooked.

[0019] The heating unit may also include a superheated steam supply unit that supplies superheated steam exceeding 100°C into the pot, and the control unit may control the superheated steam supply unit in the warming step to raise the temperature of the food to 65°C or higher after a predetermined temperature maintenance time based on the amount of food has elapsed after lowering the temperature of the food to below 60°C. With this configuration, the temperature of the food is raised by superheated steam, so that the superheated steam penetrates into the food, raising the temperature of the entire food more uniformly and rapidly. This more reliably kills germinated Bacillus bacteria before they revert to spores, thereby improving the sterilization effect.

[0020] The heating unit may further include a pot heating unit that heats the pot, and the superheated steam supply unit may include a water container that stores water, a water container heating unit that heats the water container to generate steam, a steam path that fluidly connects the water container with the pot, and a steam heating unit that heats the steam path to generate the superheated steam, and the control unit may control the pot heating unit to raise the temperature of the food to 75°C or higher when the amount of water in the water container is equal to or less than a predetermined amount. With this configuration, even if the amount of water in the water container is small and a sufficient amount of superheated steam cannot be generated, the temperature of the food can be raised to 75°C or higher by heating the pot with the pot heating unit, thereby killing the Bacillus bacteria.

[0021] Furthermore, after controlling the pan heating unit to raise the temperature of the food to 75° C. or higher, the control unit may control the pan heating unit to maintain the temperature of the food at 65° C. or higher. According to this configuration, when a sufficient amount of superheated steam cannot be generated and the pan heating unit alone cannot sufficiently kill the Bacillus bacteria, the temperature of the food can be maintained at 65° C. or higher to suppress the growth of the Bacillus bacteria.

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiment. In addition, substantially the same components in the drawings are designated by the same reference numerals.

[0023] In addition, for the sake of convenience, the following uses terms indicating directions such as "up" and "down" assuming the state of normal use, but this does not mean to limit the state of use of the rice cooker according to the present invention.

[0024] <<Embodiment>> The overall configuration of a rice cooker according to an embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view of a rice cooker according to an embodiment of the present invention.

[0025] As shown in Figure 1, the rice cooker of this embodiment includes a housing 1, a pot 2 that contains food containing rice and water, a lid 3 that can be opened and closed to cover the upper opening of the pot 2, and a heating unit 4 that heats the food in the pot 2.

[0026] Housing 1 has a cylindrical pot accommodating portion 12 with a bottom that is recessed inward from upper wall 11. Pot 2 is detachably accommodated in pot accommodating portion 12 by suspending a flange portion from the upper end of pot accommodating portion 12. The inner surface of pot accommodating portion 12 is formed so as to leave a predetermined gap between it and the outer surface of pot 2.

[0027] Opening 12a is provided in the center of the bottom of pot housing section 12. Opening 12a is provided with pot temperature sensor 5, an example of a pot temperature detector for detecting the temperature of pot 2. Pot temperature sensor 5 is positioned so that it can abut against the bottom of pot 2 housed in pot housing section 12. In this embodiment, the temperature of the food being cooked in pot 2 is estimated based on the temperature detected by pot temperature sensor 5.

[0028] The lid 3 includes a hollow outer lid 31 and a substantially disk-shaped inner lid 32. The outer lid 31 is held rotatably about a hinge shaft 13 provided on the top wall 11 of the housing 1. In this embodiment, the lid 3 is configured to cover the upper opening of the pot 2 in an openable and closable manner by rotating the outer lid 31 about the hinge shaft 13. Whether the lid 3 is open or closed is detected, for example, by a lid open / close detector 14 provided on the housing 1.

[0029] When the lid body 3 is in the closed state, the outer lid 31 is formed to cover the upper wall 11 of the housing 1. The inner lid 32 is detachably attached to the surface of the outer lid 31 facing the upper opening of the pot 2 housed in the pot housing section 12. When the lid body 3 is in the closed state, the inner lid 32 is formed to cover the upper opening of the pot 2. An annular gasket 33 is attached to the outer surface of the inner lid 32 facing the pot 2. The gasket 33 is arranged to fit tightly against the flange portion of the pot 2 when the lid body 3 is in the closed state.

[0030] Outer lid 31 has through-hole 31a penetrating it in the thickness direction. A steam tube 6 is detachably attached to through-hole 31a for venting steam generated in pot 2 to the outside. Inner lid 32 has through-hole 32a that fluidly connects the interior of pot 2 with through-hole 31a. An annular gasket 34 is attached to the periphery of through-hole 31a on the inner lid 32 side of outer lid 31. Gasket 34 is positioned so that it fits tightly around the periphery of through-hole 32a in inner lid 32 when inner lid 32 is attached to outer lid 31. Steam generated in pot 2 is vented to the outside through through-holes 32a, 31a and steam tube 6.

[0031] The outer lid 31 is also provided with a display unit (not shown) such as an LCD display that displays various information such as the cooking course and cooking time, and an operation unit (not shown) that allows the user to select a specific cooking course from multiple cooking courses such as white rice and brown rice. The operation unit is made up of multiple buttons, including a rice cooking start button, that allow the user to select a cooking course and to start, cancel, or schedule cooking. The user can use the operation unit to select a specific cooking course and start cooking while referring to the content displayed on the display unit.

[0032] Heating section 4 includes a pot heating section 41 that heats pot 2, and a superheated steam supply section 42 that supplies superheated steam exceeding 100°C into pot 2.

[0033] In this embodiment, the pot heating section 41 is composed of an induction heating coil unit that induction heats the pot 2. The induction heating coil unit includes an inner bottom heating coil 41a, an outer bottom heating coil 41b, and a side heating coil 41c. The inner bottom heating coil 41a is positioned to face the periphery of the center of the bottom of the pot 2 across the pot accommodating section 12. The outer bottom heating coil 41b is positioned to face the corner of the bottom of the pot 2 across the pot accommodating section 12. The side heating coil 41c is positioned to face the side of the pot 2 across the pot accommodating section 12.

[0034] In this embodiment, the superheated steam supply unit 42 includes a water container 42a, a water container heating unit 42b, a steam path 42c, and a steam heating unit 42d.

[0035] The water container 42a is a cylindrical container with a bottom that contains water for generating steam. The housing 1 includes a cylindrical water container housing 15 with a bottom, recessed inward from the top wall 11, at a location different from the pot housing 12. The water container 42a is housed in the water container housing 15 by suspending its flange from the upper end of the water container housing 15. The inner surface of the water container housing 15 is formed so as to leave a predetermined gap between it and the outer surface of the water container 42a. The water container housing 15 also includes a water container temperature sensor 7, an example of a water container temperature detector, for detecting the temperature of the water in the water container 42a. The water container temperature sensor 7 is positioned so as to be able to abut against the side surface of the water container 42a housed in the water container housing 15. In this embodiment, the temperature of the water in the water container 42a is estimated based on the temperature detected by the water container temperature sensor 7.

[0036] The water container heating unit 42b heats the water container 42a to generate steam. More specifically, the water container heating unit 42b heats the water container 42a, boiling the water in the water container 42a and generating steam at approximately 100°C. In this embodiment, the water container heating unit 42b is configured with a heating coil that inductively heats the water container 42a. The water container heating unit 42b is positioned so as to face the side of the water container 42a across the water container housing 15.

[0037] Steam path 42c is a cylindrical path that provides fluid communication between the inside of water container 42a and the inside of pot 2. Steam path 42c is provided in outer lid 31. An annular gasket 35 is attached to the end of steam path 42c facing the water container 42a. Gasket 35 is provided so as to fit tightly against the flange of water container 42a when lid 3 is closed. An annular gasket 36 is attached to the end of steam path 42c facing the pot 2. Gasket 36 is provided so as to fit tightly against inner lid 32 when lid 3 is closed. Inner lid 32 has a through-hole 32b that provides fluid communication between the pot 2 and steam path 42c.

[0038] Steam heating unit 42d heats steam path 42c to generate superheated steam (e.g., 200°C or higher). In this embodiment, steam heating unit 42d is configured with a heating coil that induction heats steam path 42c. Steam heating unit 42d is disposed on the outer peripheral surface of steam path 42c. Steam generated by heating with water container heating unit 42b is converted into superheated steam by heating with steam heating unit 42d, and is supplied into pot 2 through steam path 42c and through-hole 42b.

[0039] Furthermore, a control unit 16 is mounted inside the housing 1. Based on the cooking course selected on the operation unit and the temperature detected by the pot temperature sensor 5, the control unit 16 controls the heating unit 4 to perform a rice cooking process in which the food (rice and water) in the pot 2 is cooked. After the rice cooking process is completed, the control unit 16 controls the heating unit 4 to perform a warming process in which the food (rice) in the pot 2 is kept warm based on the temperature detected by the pot temperature sensor 5, the temperature detected by the water container temperature sensor 7, detection information from the lid open / close detection unit 14, and the like.

[0040] Next, the control operation of the control unit 16 in the heat retention step will be described in more detail.

[0041] In this embodiment, the control unit 16 performs the keeping-warm step by changing the temperature of the food to promote the extinction of the Bacillus bacteria derived from rice.

[0042] Figure 2 is a graph showing an example of the change in temperature of the food being cooked and the temperature detected by the pan temperature sensor during the keep-warm process in the rice cooker according to this embodiment. In Figure 2, the thick solid line shows the actual change in temperature of the food being cooked in pan 2. In Figure 2, the thin solid line shows the change in temperature detected by pan temperature sensor 5.

[0043] In the heat retention process, the control unit 16 controls the heating unit 4 to lower the temperature of the food to below 60°C, and when a temperature maintenance time T1 predetermined according to the amount of the food has elapsed, to raise the temperature of the food to 65°C or higher.

[0044] More specifically, control unit 16 reduces or stops heating by heating unit 4 to lower the temperature of the food to below 60°C. At this time, control unit 16 estimates the amount of food to be cooked based on the ambient temperature around the rice cooker and the rate of change of the temperature detected by pan temperature sensor 5. Then, based on the estimation result, control unit 16 controls heating unit 4 so that the temperature detected by the pan temperature sensor is maintained at a predetermined controlled temperature (e.g., 50°C) below 60°C for temperature maintenance time T1. Then, control unit 16 controls heating unit 4 so that the temperature of the food to be cooked to 65°C or higher. Control unit 16 repeatedly performs the above-mentioned control throughout the keep-warm process.

[0045] Here, the "ambient temperature around the rice cooker" can be estimated, for example, based on the temperature detected by the pot temperature sensor 5 before the heating unit 4 is controlled to heat the food in the pot 2 (for example, before the rice cooking process begins). In this case, the control unit 16 stores the temperature detected by the pot temperature sensor 5 before the food in the pot 2 is heated as the ambient temperature. Note that the "ambient temperature around the rice cooker" may be detected, for example, by providing a room temperature sensor in the rice cooker and detecting the temperature detected by the room temperature sensor. Furthermore, the "amount of food" may be detected, for example, by providing a weight sensor to support the pot and detecting the weight detected by the weight sensor.

[0046] FIG. 3 is a graph showing the relationship between the temperature drop time td, which is the time it takes for the temperature detected by pan temperature sensor 5 to drop from a first temperature to a second temperature, the amount of food being cooked Ga, and the ambient temperature. In this embodiment, the first temperature is 65°C, and the second temperature is 60°C. As shown in FIG. 3, the temperature drop time td and the amount of food being cooked Ga are proportional to each other, but the temperature drop time td for a specific amount of food being cooked Ga varies depending on the ambient temperature. In other words, there is a correlation between the temperature drop time td, the amount of food being cooked Ga, and the ambient temperature. Therefore, the amount of food being cooked can be estimated based on the ambient temperature and the rate of change of the temperature detected by pan temperature sensor 5.

[0047] The ambient temperature can also be estimated based on the rate of change in the temperature detected by the pan temperature sensor 5 and the amount of food being cooked. The warming process is expected to be performed over a long period of time (e.g., 12 hours). Therefore, the ambient temperature may change significantly during the warming process. Even in such a case, if the lid 3 is not opened or closed, it is assumed that the amount of food in the pan 2 remains unchanged. Therefore, after estimating the amount of food, when a predetermined time has elapsed without the lid open / close detection unit 14 detecting the opening or closing of the lid 3, the control unit 16 may correct the ambient temperature stored by the control unit 16 based on the temperature detected by the pan temperature sensor 5 and the estimated amount of food after that time has elapsed. This allows the amount of food to be estimated based on a more accurate ambient temperature, even if the amount of food in the pan 2 decreases due to the opening or closing of the lid 3 after the ambient temperature correction. This eliminates the need for a room temperature sensor or weight sensor.

[0048] Furthermore, since the ambient temperature can be estimated more accurately during the warming process, the control unit 16 may correct the controlled temperature, at which the temperature detected by the pan temperature sensor 5 is maintained during the temperature maintenance time T1, based on the estimated ambient temperature. FIG. 4 is a graph showing an example of the controlled temperature setting relative to the ambient temperature. As shown in FIG. 4, for example, when the ambient temperature is 23°C, the controlled temperature may be set to approximately 50°C. Also, for example, when the ambient temperature is 30°C, the controlled temperature may be set to approximately 51°C. This allows appropriate warming to be performed taking the ambient temperature into consideration.

[0049] As described above, the control unit 16 controls the heating unit 4 to lower the temperature of the food to below 60°C and then raise the temperature of the food to 65°C or higher after a predetermined temperature maintenance time T1 corresponding to the amount of food has elapsed. This allows many Bacillus bacteria to germinate and kill the germinated Bacillus bacteria. At this time, as shown in FIG. 7, some Bacillus bacteria may be left unkilled but partially damaged. The partially damaged Bacillus bacteria may recover and return to spore form. To kill these Bacillus bacteria, it is necessary to consider not only the time it takes for the spores to germinate but also the time it takes for the partial damage to be repaired and the food to return to spore form. Therefore, the control unit 16 controls the heating unit 4 to lower the temperature of the food to below 60°C again and then raise the temperature of the food to 65°C or higher after a second temperature maintenance time T2 corresponding to the amount of food and longer than the (first) temperature maintenance time T1 has elapsed. This makes it possible to more reliably kill the Bacillus bacteria by making the second temperature maintenance time longer than the temperature maintenance time T1, taking into account the time it takes for the bacteria to partially repair damage and return to spore form. Furthermore, compared to when the second temperature maintenance time T2 is shorter than the temperature maintenance time T1, the amount of heat applied to the food can be reduced, further preventing deterioration of the food due to keeping it warm.

[0050] Fig. 5 is a table showing examples of setting the temperature maintenance time T1 and the second temperature maintenance time T2 for an estimated amount of food Ga. As shown in Fig. 5, for example, when the amount of food Ga is 2 cups, the temperature maintenance time T1 may be set to 110 minutes and the second temperature maintenance time T2 may be set to 155 minutes. This makes it possible to prevent deterioration of the food due to keeping it warm while further improving the sterilization effect.

[0051] As described above, the rice cooker according to the present invention reduces the temperature of the food to less than 60°C during the warming process, thereby reducing the amount of heat applied to the food and preventing deterioration of the food due to warming. It also promotes germination of Bacillus bacteria.

[0052] Furthermore, with the rice cooker according to the present invention, the temperature of the food to be cooked is lowered to below 60°C, and when a predetermined temperature maintenance time T1 depending on the amount of food has elapsed, the temperature of the food to be cooked is raised to 65°C or higher, thereby killing germinated Bacillus bacteria, thereby further improving the sterilization effect.

[0053] In the keeping-warm step, if the food is heated only by the pan heating unit 41, significant temperature variations tend to occur between the surface and center of the food. If the heating time of the food is extended to avoid this, germinated Bacillus bacteria may revert to spores during heating, potentially resulting in insufficient killing of the Bacillus bacteria. Therefore, in the keeping-warm step, the food is preferably heated by the superheated steam supply unit 42. Specifically, the control unit 16 preferably controls the superheated steam supply unit 42 to raise the temperature of the food to 65°C or higher after a predetermined temperature maintenance time T1 (or T2) determined based on the amount of food has elapsed. This allows the superheated steam to penetrate the interior of the food, raising the temperature of the entire food more uniformly and rapidly (e.g., twice as fast as heating by the pan heating unit 41). As a result, germinated Bacillus bacteria can be more reliably killed before they revert to spores, resulting in improved sterilization effects. Control unit 16 may control both pan heating unit 41 and superheated steam supply unit 42 so as to raise the temperature of the food to 65° C. or higher. In this case, the temperature of the food can be raised even more rapidly.

[0054] As mentioned above, when the food is heated by the pan heating unit 41 during the warming process, significant temperature variations are likely to occur between the surface and center of the food. For example, when the temperature of the surface of the food is 75°C, the temperature of the center of the food may be 65°C. Once germinated, Bacillus bacteria may proliferate in a temperature environment below 65°C. In addition, in this embodiment, the temperature of the food is estimated based on the temperature detected by the pan temperature sensor 5, so the temperature of the surface of the food can be estimated more accurately than the temperature of the center of the food. Therefore, when heating the food with the pan heating unit 41, it is preferable to raise the temperature of the food to 75°C or higher. That is, during the warming process, the control unit 16 preferably controls the pan heating unit 41 to raise the temperature of the food to 75°C or higher after lowering the temperature of the food to below 60°C. This allows the germinated Bacillus bacteria to be exposed to a higher temperature environment, thereby accelerating the death of the germinated Bacillus bacteria and improving the sterilization effect.

[0055] Furthermore, when the food is heated by superheated steam supply unit 42 during the warming step, it may happen that the water in water container 42a runs out during the warming step, making it impossible to generate superheated steam. For this reason, control unit 16 may control pot heating unit 41 to raise the temperature of the food to 75°C or higher when the amount of water in water container 42a is below a predetermined amount, as shown in Fig. 6. This allows the temperature of the food to be raised to 75°C or higher by heating pot 2 with pot heating unit 41, thereby killing the Bacillus bacteria, even when the amount of water in water container 42a is low and a sufficient amount of superheated steam cannot be generated.

[0056] Here, the "amount of water in water container 42a" can be estimated based on, for example, the times th1 and th2 (see FIG. 6) for the temperature of the food to rise from less than 60°C to 75°C or higher. That is, if there is a sufficient amount of water in water container 42a and sufficient superheated steam can be generated, the time th1 for the temperature of the food to rise from less than 60°C to 75°C or higher is set as th1. In contrast, if time th2 is longer than time th1, it is assumed that the amount of water in water container 42a is small and sufficient superheated steam cannot be generated. This allows the "amount of water in water container 42a" to be estimated. Furthermore, the "amount of water in water container 42a" can also be estimated based on the temperature detected by water container temperature sensor 7. For example, if the time it takes for the temperature detected by water container temperature sensor 7 to rise from the third temperature to the fourth temperature is shorter than a predetermined time, it can be assumed that there is no water in water container 42a. Note that the "amount of water in water container 42a" may be detected based on the weight detected by a weight sensor provided to support water container 42a.

[0057] Although the present invention has been fully described in connection with the preferred embodiments with reference to the accompanying drawings, various changes and modifications will be apparent to those skilled in the art, and it is to be understood that such changes and modifications are included within the scope of the present invention as defined by the appended claims unless they depart therefrom. [Industrial Applicability]

[0058] The rice cooker according to the present invention can improve the sterilization effect while suppressing deterioration of cooked food due to keeping it warm, and is therefore useful, for example, as a rice cooker for home and commercial use. [Explanation of symbols]

[0059] 1 chassis 2. Pot 3 Lid 4 Heating section 5 Pot temperature sensor (pot temperature detection part) 6 steam cylinder 7 Water container temperature sensor (water container temperature detection part) 11 Upper wall 12 Pot storage section 12a opening 13 Hinge axis 14 Lid open / close detector 15 Water container storage section 16 Control Unit 31 Outer lid 31a Through hole 32 Inner lid 32a,32b through hole 33, 34, 35, 36 Gasket 41 Pot heating section 41a Bottom heating coil 41b Bottom outer heating coil 41c Side heating coil 42 Superheated steam supply section 42a water container 42b Water container heating section 42c Steam path 42d Steam heating section

Claims

1. a pot for containing food to be cooked; A heating unit that heats the food in the pot; a control unit that controls the heating unit to perform a heat retention step of keeping the food warm; Equipped with the control unit, in the keeping-warm step, controls the heating unit to lower and maintain the temperature of the food to be cooked below 60°C, and when a first temperature maintenance time predetermined according to the amount of the food to be cooked has elapsed, controls the heating unit to raise the temperature of the food to 65°C or higher, and then controls the heating unit to lower and maintain the temperature of the food to be cooked below 60°C, and when a second temperature maintenance time has elapsed, controls the heating unit to raise the temperature of the food to 65°C or higher; The first temperature maintenance time and the second temperature maintenance time are set so that, for a plurality of cases where the amount of the food to be cooked is different, the first temperature maintenance time and the second temperature maintenance time are set so that the first temperature maintenance time and the second temperature maintenance time are longer in each case as the amount of the food to be cooked increases. Rice cooker.

2. 2. The rice cooker according to claim 1, wherein the control unit controls the heating unit so that, in the keeping warm process, after lowering the temperature of the food to less than 60°C, the temperature of the food is raised to 75°C or higher.

3. Further provided is a pot temperature detection unit that detects the temperature of the pot, 3. The rice cooker according to claim 1, wherein the control unit estimates the temperature of the food being cooked based on the temperature detected by the pan temperature detection unit, estimates the amount of the food being cooked based on the ambient temperature around the rice cooker and the rate of change in the temperature detected by the pan temperature detection unit when the temperature of the food being cooked is lowered to below 60°C, and controls the heating unit based on the estimation results.

4. A pot for containing food to be cooked; A heating unit that heats the food in the pot; a control unit that controls the heating unit to perform a heat retention step of keeping the food warm; A lid that can open and close the upper opening of the pot; a lid opening / closing detection unit that detects the opening and closing of the lid body; Equipped with the control unit controls the heating unit to lower the temperature of the food to less than 60°C in the keeping-warm step, and raise the temperature of the food to 65°C or higher after a predetermined temperature maintenance time has elapsed depending on the amount of the food; The temperature maintenance time is longer as the amount of food to be cooked increases, The control unit stores the temperature detected by the pot temperature detection unit before controlling the heating unit to heat the food in the pot as the ambient temperature, and in the keeping-warm process, after estimating the amount of food, when a predetermined time has passed without the lid opening / closing detection unit detecting the opening or closing of the lid, corrects the ambient temperature based on the temperature detected by the pot temperature detection unit after the predetermined time has passed and the estimated amount of food.

5. The heating unit includes a superheated steam supply unit that supplies superheated steam exceeding 100°C into the pot, 5. The rice cooker according to claim 4, wherein the control unit controls the superheated steam supply unit to raise the temperature of the food to 65°C or higher when a predetermined temperature maintenance time based on an amount of the food has elapsed after lowering the temperature of the food to less than 60°C in the keeping-warm process.

6. A pot for containing food to be cooked; A heating unit that heats the food in the pot; a control unit that controls the heating unit to perform a heat retention step of keeping the food warm; Equipped with the control unit controls the heating unit to lower the temperature of the food to less than 60°C in the keeping-warm step, and raise the temperature of the food to 65°C or higher after a predetermined temperature maintenance time has elapsed depending on the amount of the food; The temperature maintenance time is longer as the amount of food to be cooked increases, The heating unit includes a superheated steam supply unit that supplies superheated steam exceeding 100°C into the pot, and a pot heating unit that heats the pot, the control unit controls the superheated steam supply unit to raise the temperature of the food to 65°C or higher when a predetermined temperature maintenance time according to an amount of the food has elapsed after lowering the temperature of the food to less than 60°C in the keeping-warm step; the superheated steam supply unit includes a water container for storing water, a water container heating unit for heating the water container to generate steam, a steam path for fluidly connecting the water container with the pot, and a steam heating unit for heating the steam path to generate the superheated steam; The control unit controls the pot heating unit to raise the temperature of the food to 75°C or higher when the amount of water in the water container is equal to or less than a predetermined amount.

7. 7. The rice cooker of claim 6, wherein the control unit controls the pot heating unit to maintain the temperature of the food at 65°C or higher after controlling the pot heating unit to raise the temperature of the food to 75°C or higher.

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