Rice cooker

Abstract

To provide a rice cooker that has improved the taste of cooked rice while suppressing increase in the size of the rice cooker.SOLUTION: A rice cooker includes: a pot where rice to be cooked including rice and water is stored; a heating part for heating the pot; a lid body for closing the opening of the pot; a pressure valve for opening and closing a steam discharge hole for communicating the internal space of the pot with the outside of the pot; and a control part for controlling the heating part and the pressure valve. The control part performs a rice cooking process including a temperature raising process for heating the pot until the temperature of the water reaches about 100°C, and a boiling maintaining process for boiling the water after the temperature raising process and maintaining the boiling. The control part closes the pressure valve and pressurizes the internal space to a boiling pressure exceeding an atmospheric pressure in a first half stage of the boiling maintaining process in which moisture in the pot is sufficient, and opens the pressure valve and lowers the pressure in the internal space from the boiling pressure so as to enlarge the gaps between rice grains in a second half stage of the boiling maintaining process in which moisture in the pot is scarce.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Conventionally, as this type of rice cooker, for example, a rice cooker (heating cooker) described in Patent Document 1 is known. The rice cooker described in Patent Document 1 includes a pot that houses an object to be cooked, such as rice and water, a heating unit that heats the pot, and a lid that closes the opening of the pot. A pressure valve that can open and close a steam discharge hole that communicates the internal space of the pot with the outside is attached to the lid. The heating unit and the pressure valve are controlled by a control unit provided in the rice cooker.

[0003] The control unit controls the heating unit and the pressure valve so as to sequentially execute a water absorption step, a temperature rising step, and a boiling maintenance step. Specifically, in the water absorption step, the control unit maintains the temperature of the object to be cooked below the gelatinization temperature (for example, 55°C) and allows the rice to absorb water. In the temperature rising step, the control unit controls the heating unit so as to heat the object to be cooked at full power and bring it to a boil. In the boiling maintenance step, the control unit controls the heating unit so as to maintain the water in a boiling state.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the rice cooker of Patent Document 1, there is still room for improvement from the viewpoint of improving the taste of the cooked rice while suppressing the increase in size of the rice cooker.

[0006] Therefore, an object of the present disclosure is to solve the above problems and provide a rice cooker in which the taste of the cooked rice is improved while suppressing the increase in size of the rice cooker.

Means for Solving the Problem

[0007] The rice cooker according to the present disclosure is a pot for containing the rice to be cooked including rice and water, a heating unit for heating the pot, a lid for closing the opening of the pot, a pressure valve for opening and closing a steam discharge hole communicating the internal space of the pot with the outside of the pot, a control unit for controlling the heating unit and the pressure valve, the control unit performing a rice cooking process including a temperature rising process of heating the pot until the temperature of the water reaches about 100°C, and a boiling maintaining process of boiling and maintaining the water after the temperature rising process, and is provided with In the first half stage of the boiling maintaining process where there is sufficient moisture in the pot, the control unit closes the pressure valve to pressurize the internal space to a boiling pressure exceeding the atmospheric pressure, and in the latter half stage of the boiling maintaining process where the moisture in the pot decreases, the control unit opens the pressure valve to lower the pressure of the internal space from the boiling pressure, thereby expanding the gaps between the grains of rice.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to provide a rice cooker that improves the taste of the cooked rice while suppressing the increase in size of the rice cooker.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

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Figure 5

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Figure 8

Figure 9

MODE FOR CARRYING OUT THE INVENTION

[0010] <Knowledge on which the present disclosure is based> As a result of intensive studies to improve the taste of cooked rice while suppressing the increase in size of the rice cooker, the present inventors have obtained the following knowledge.

[0011] In the rice cooker described in Patent Document 1, the control unit opens the pressure valve at a stage where there is sufficient moisture in the pot during the boiling maintenance process. By opening the pressure valve, the pressurized internal space is rapidly depressurized to atmospheric pressure. At this time, the boiling point of the water in the pot drops rapidly, causing bumping boiling and generating a large number of bubbles. The movement of these bubbles stirs the rice.

[0012] In a rice cooker in which bumping boiling is caused, it is desirable to set the pressure in the internal space before decompression to as high a pressure as possible (for example, 1.5 atmospheres). This is because the greater the difference between the pressure before decompression and atmospheric pressure, the more violent boiling can occur.

[0013] On the one hand, if a large pressure difference is applied for depressurization when there is sufficient moisture in the pot, the water in the pot may be sucked into the steam discharge hole and discharged outside the pot. In particular, if the amount of water discharged is large, the water in the pot will be insufficient during the rice cooking process after depressurization, and the taste of the cooked rice will deteriorate.

[0014] As a method for suppressing water discharge, it is conceivable to provide a space for relaxing the momentum of the sucked water in the steam discharge hole. However, the greater the pressure difference during depressurization, the larger the space needs to be taken, making it difficult to fit the rice cooker into the desired size.

[0015] Therefore, the inventors of the present invention found that in the first half of the boiling maintenance process when there is sufficient moisture in the pot, the pressure valve is closed to pressurize the internal space to the boiling pressure exceeding atmospheric pressure, and in the second half of the boiling maintenance process when the moisture in the pot decreases, the pressure valve is opened to lower the pressure of the internal space from the boiling pressure. According to this configuration, when depressurizing from the boiling pressure, since the water in the pot is already in a state of being less, it is difficult for the water in the pot to be sucked into the steam discharge hole and discharged outside the pot. Therefore, it is possible to perform depressurization with a large pressure difference without providing a large space for relaxing the momentum of water in the steam discharge hole. Based on this new finding, the inventors of the present invention have arrived at the following disclosure.

[0016] According to the first aspect of the present disclosure, a pot containing the object to be cooked rice including rice and water, a heating unit for heating the pot, a lid for closing the opening of the pot, a pressure valve for opening and closing a steam discharge hole communicating the internal space of the pot with the outside of the pot, a control unit for controlling the heating unit and the pressure valve, the control unit performing a rice cooking process including a temperature rising process of heating the pot until the temperature of the water reaches about 100°C and a boiling maintenance process of boiling and maintaining the water after the temperature rising process, is provided, In the first half stage of the boiling maintenance step where there is sufficient moisture in the pot, the control unit closes the pressure valve to pressurize the internal space to a boiling pressure exceeding atmospheric pressure. In the latter half stage of the boiling maintenance step where the moisture in the pot decreases, the control unit opens the pressure valve to lower the pressure of the internal space from the boiling pressure, thereby expanding the gaps between the grains of rice. Provided is a rice cooker.

[0017] According to a second aspect of the present disclosure, there is provided a rice cooker as described in the first aspect, wherein in the boiling maintenance step, when the temperature of the water in the pot rises to near the boiling point corresponding to the pressure of the internal space, the control unit opens the pressure valve to lower the pressure of the internal space from the boiling pressure.

[0018] According to a third aspect of the present disclosure, further comprising a pressure detection unit that detects the pressure of the internal space, wherein when a predetermined time has elapsed since the pressure of the internal space detected by the pressure detection unit has risen to 1.5 atmospheres, the control unit opens the pressure valve to lower the pressure of the internal space from the boiling pressure. There is provided a rice cooker as described in the first or second aspect.

[0019] According to a fourth aspect of the present disclosure, further comprising a selection unit capable of selecting a rice cooking time, wherein in the boiling maintenance step, the shorter the rice cooking time selected by the selection unit, the higher the boiling pressure, and the control unit lowers the pressure of the internal space from the boiling pressure. There is provided a rice cooker as described in any one of the first to third aspects.

[0020] According to a fifth aspect of the present disclosure, the control unit performs a steaming step of steaming the rice after the boiling maintenance step, wherein after opening the pressure valve in the boiling maintenance step, the control unit closes the pressure valve to pressurize the internal space, and in the steaming step, the control unit gradually or gently lowers the pressure of the internal space. Provided is a rice cooker according to any one of the first to fourth aspects.

[0021] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, terms indicating a specific direction or position (for example, terms including "up", "down", "right", and "left") are used as necessary. However, the use of these terms is for facilitating the understanding of the present disclosure with reference to the drawings, and the technical scope of the present disclosure is not limited by the meanings of these terms. Further, the following description is merely illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0022] <Embodiment> A rice cooker according to an embodiment of the present disclosure will be described. FIG. 1 is a schematic cross-sectional view of the rice cooker according to the embodiment of the present disclosure.

[0023] As shown in FIG. 1, the rice cooker according to the present embodiment includes a substantially bottomed cylindrical rice cooker body 1 having a pot storage portion 11 formed therein, and a pot 2 stored in the pot storage portion 11 and containing an object to be cooked rice including rice and water. An outer lid 3 having a hollow structure that can open and close the upper opening of the rice cooker body 1 is attached to the upper portion of the rice cooker body 1. An approximately disk-shaped inner lid 4 that can seal the upper opening of the pot 2 is detachably attached to the inner side of the outer lid 3 (the side covering the upper opening of the pot 2). In the present embodiment, the outer lid 3 and the inner lid 4 constitute a lid body that can open and close the opening of the pot 2 freely.

[0024] The pot storage portion 11 of the rice cooker body 1 is formed in a concave shape that is recessed downward from the upper surface 1a of the rice cooker body 1. The pot storage portion 11 has a cylindrical side wall portion 111 arranged so as to have a predetermined gap with respect to the peripheral wall portion 23 of the stored pot 2, and a bottom portion 112 arranged so as to have a predetermined gap with respect to the pot bottom portion 22 of the pot 2. The upper surface 1a of the rice cooker body 1 supports a flange portion 21 provided around the upper opening of the pot 2 around the pot storage portion 11.

[0025] On the outer surfaces of the side wall portion 111 and the bottom portion 112, a heating unit 5 for heating (induction heating) the pot 2 is attached. The heating unit 5 includes an inner-bottom heating coil 51, an outer-bottom heating coil 52, and a wall heating coil 53. The inner-bottom heating coil 51 is disposed so as to face the periphery of the central portion of the pot bottom portion 22 of the pot 2 through the bottom portion 112 of the pot storage portion 11. The outer-bottom heating coil 52 is disposed so as to face the corner portion of the pot bottom portion 22 of the pot 2 through the bottom portion 112. The wall heating coil 53 is disposed so as to face the peripheral wall portion 23 of the pot 2 through the side wall portion 111.

[0026] An opening is provided in the central portion of the bottom portion 112 of the pot storage portion 11. In the opening, a pot temperature sensor 12 for measuring the temperature of the pot 2 is disposed so as to be able to contact the pot bottom portion 22 of the pot 2 stored in the pot storage portion 11.

[0027] The temperature of the pot 2 detected by the pot temperature sensor 12 is correlated with the temperature of the internal space SP2 of the pot 2. Therefore, based on the detected temperature of the pot temperature sensor 12, the temperature of the internal space SP2 can be estimated. Here, the temperature of the internal space SP2 is substantially the same as the temperature of the object to be cooked. For example, the temperature of the internal space SP2 is calculated by multiplying the detected temperature of the pot temperature sensor 12 by a correlation coefficient obtained experimentally. This calculation process is performed, for example, in the control unit 13 described later.

[0028] The outer lid 3 includes an upper outer member 31 and a lower outer member 32 that constitute the outer contour of the outer lid 3. A hinge (not shown) for connecting the outer lid 3 and the rice cooker body 1 is provided at the rear portion of the outer lid 3. The outer lid 3 opens and closes by rotating about the hinge.

[0029] On the lower outer casing member 32, a recessed portion 321 that is recessed upward is provided at a position facing the inner lid 4 in the vertical direction. An exhaust space SP1 for discharging the steam in the pot 2 is formed between the recessed portion 321 and the inner lid 4. A steam passage 33 that fluidly communicates the exhaust space SP1 with the outside of the rice cooker is connected to the top surface of the recessed portion 321 facing the inner lid 4. The steam passage 33 has a first opening end portion 331 that opens to the top surface of the recessed portion 321 and a second opening end portion 332 that opens to the upper outer casing member 31. The exhaust space SP1 is in fluid communication with the outside of the rice cooker via the steam passage 33. Note that a steam cylinder having a cylindrical portion inserted into the steam passage 33 may be detachably attached from the upper outer casing member 31 side to the steam passage 33.

[0030] On the inner lid 4, steam discharge holes 41 and 42 for discharging the steam in the pot 2 are provided at positions facing the exhaust space SP1. The steam discharge holes 41 and 42 fluidly communicate the internal space SP2 of the pot 2 with the exhaust space SP1. That is, the internal space SP2 of the pot 2 is in fluid communication with the outside of the rice cooker via the steam discharge holes 41 and 42, the exhaust space SP1, and the steam passage 33. A steam temperature sensor (not shown) for detecting the temperature of the steam is provided in the recessed portion 321 or the steam passage 33.

[0031] The inner lid 4 has a pressure regulating valve 61 that can open and close the steam discharge hole 41 and a pressure valve 62 that can open and close the steam discharge hole 42.

[0032] The pressure regulating valve 61 is a valve that suppresses the pressure inside the pot 2 from rising above a predetermined value (for example, 1.5 atm) higher than the atmospheric pressure. In the present embodiment, the pressure regulating valve 61 includes a closing member 611 that closes the steam discharge hole 41, and a spring 612 that biases the closing member 611 downward so as to close the steam discharge hole 41. According to this configuration, when the pressure in the internal space SP2 rises above a predetermined value higher than the atmospheric pressure, the closing member 611 moves upward against the biasing force of the spring 612 due to the pressure, and the steam discharge hole 41 is opened. On the other hand, when the pressure in the internal space SP2 drops below the predetermined value, the closing member 611 is biased by the spring 612 and moves downward to close the steam discharge hole 41 again. By repeating the opening and closing of the steam discharge hole 41, the pressure in the internal space SP2 is maintained at the predetermined value.

[0033] Note that the pressure regulating valve 61 may be constituted by a ball and may close the steam discharge hole 41 by its own weight. In this case, when the pressure in the internal space SP2 becomes greater than its own weight (for example, when it becomes 1.5 atm or more), the pressure regulating valve 61 is pushed only by the pressure in the internal space SP2 and moves away from the steam discharge hole 41, opening the steam discharge hole 41.

[0034] The pressure valve 62 is configured to move between a closed position that closes the steam discharge hole 42 and an open position that opens the steam discharge hole 42. Normally, the pressure valve 62 is maintained in the closed position by a spring attached to the pressure valve 62. When the pressure valve 62 is in the closed position, the pressure in the internal space SP2 can rise to the predetermined value at which the pressure regulating valve 61 is opened.

[0035] The outer lid 3 is provided with a pressure valve moving mechanism 63 that moves the pressure valve 62 to the open position so as to open the steam discharge hole 42. The pressure valve moving mechanism 63 is configured to press the pressure valve 62 downward under the control of a control unit 13 described later, and move it from the closed position to the open position. Thereby, the pressure in the internal space SP2 can be reduced from a pressure exceeding the atmospheric pressure to the atmospheric pressure. Note that, as a specific configuration of the pressure valve moving mechanism 63, a conventionally known configuration can be adopted.

[0036] In addition, on the outer lid 3, a display operation unit 34 is provided that displays various information such as the rice cooking course and the rice cooking time, and can select a specific rice cooking course from a plurality of rice cooking courses such as the white rice course, the brown rice course, the white rice (soft) course, and the quick cooking course. The display operation unit 34 is an example of the selection unit in the present disclosure. In the present embodiment, in the display operation unit 34, the rice cooking time can be selected in units of, for example, 5 minutes. Thereby, rice cooking can be performed according to the convenience of the user.

[0037] The display operation unit 34 includes a liquid crystal display that displays various information such as the rice cooking course and the rice cooking time, and a plurality of buttons that, in addition to selecting the rice cooking course, instruct the execution of starting, canceling, reserving, etc. of the rice cooking. The user can select a specific rice cooking course or rice cooking time by operating the plurality of buttons while referring to the various information displayed on the liquid crystal display, and instruct the start of the rice cooking.

[0038] The rice cooker according to the present embodiment includes a pressure detection unit 35 that directly or indirectly detects the pressure in the internal space SP2. In the present embodiment, the pressure detection unit 35 is a pressure sensor provided on the outer lid 3. The pressure sensor measures the pressure in a pressure detection space SP3 provided between the outer lid 3 and the inner lid 4. The pressure detection space SP3 communicates with the internal space SP2 through a hole 43 provided in the inner lid 4. Therefore, the pressure in the pressure detection space SP3 is substantially the same as the pressure in the internal space SP2. The pressure sensor is, for example, an absolute pressure sensor, a gauge pressure sensor that indicates the pressure based on the atmospheric pressure, or a differential pressure sensor that indicates the differential pressure with respect to an arbitrary pressure (for example, the pressure outside the rice cooker).

[0039] Inside the rice cooker main body 1, a control unit 13 is installed. The control unit 13 includes a storage unit that stores a plurality of rice cooking sequences for cooking rice. Here, the "rice cooking sequence" refers to the rice cooking procedure in which, when sequentially performing mainly four steps of soaking, temperature rising, boiling maintenance, and steaming, the energization time, heating temperature, heating time, heating output, etc. are predetermined in each step. Each rice cooking sequence corresponds to one of a plurality of rice cooking courses. The control unit 13 controls the heating unit 5 and the pressure valve moving mechanism 63 based on the selected rice cooking course at the display operation unit 34, the detected temperature of the pan temperature sensor 12, and the detected pressure of the pressure detection unit 35, and executes the rice cooking process.

[0040] Next, the operation of the pressure type rice cooker according to the present embodiment will be described. FIG. 2 is a graph showing the relationship between the detected temperature of the pan temperature sensor, the water temperature, the pressure in the internal space, and the open / closed state of the pressure valve when rice cooking is performed by the rice cooker according to the embodiment of the present disclosure.

[0041] First, the pan 2 containing the object to be cooked including rice and water is set in the pan storage unit 11 by the user. Thereafter, the user selects a rice cooking course at the display operation unit 34. Here, the rice cooking sequence corresponding to each rice cooking course has information on the rice cooking time from the start to the end of the rice cooking process. This rice cooking time varies according to the brand of rice corresponding to each rice cooking course, the hardness of the cooked rice (for example, firm or soft), etc. Therefore, by selecting the rice cooking course, the user indirectly selects the rice cooking time.

[0042] Also, in the present embodiment, at the display operation unit 34, it is also possible to directly select the length of the rice cooking time. For example, the user can select the rice cooking time in 5 - minute units within the range of the rice cooking time during which normal rice cooking is possible.

[0043] After the selection of the rice cooking course or the rice cooking time, when the start of rice cooking is instructed, the rice cooking process is started under the control of the control unit 13. When the rice cooking process is started, first, the soaking process is started.

[0044] The soaking process is a process of soaking rice in water at a temperature lower than the gelatinization temperature to allow the rice to absorb water in advance so that the center of the rice can be fully gelatinized in subsequent processes. In the soaking process of the present embodiment, as shown in FIG. 2, the control unit 13 controls the heating operation of the heating unit 5 based on the detected temperature of the pot temperature sensor 12 so as to maintain the water temperature in the pot 2 at 40° C. after raising the water temperature in the pot 2 to 40° C. The heating amount of the heating unit 5 is controlled by, for example, duty control. Further, the control unit 13 controls the pressure valve moving mechanism 63 so as to maintain the pressure valve 62 in the open position during the soaking process. Thereby, the steam discharge hole 42 is maintained in the open state during the soaking process.

[0045] Note that the control unit 13 may maintain the heating unit 5 in the stopped state until the end of the soaking process. In this case, the water in the pot 2 is kept at room temperature (for example, 20° C.).

[0046] When a predetermined time elapses from the start of the soaking process according to the selected rice cooking course, the control unit 13 shifts to the temperature raising process. In the example shown in FIG. 2, when 7 minutes have elapsed since the start of rice cooking, the process shifts from the soaking process to the temperature raising process.

[0047] The temperature raising process is a process of heating the pot 2 at high heat until the temperature of the water in the pot 2 (for example, the average water temperature) reaches about 100° C. In the temperature raising process, the control unit 13 controls the heating unit 5 so as to rapidly heat the pot 2 so that the temperature of the water in the pot 2 reaches about 100° C. In the present embodiment, the control unit 13 controls the heating unit 5 so that the temperature of the water in the pot 2 reaches 100° C. Note that the control unit 13 may control the heating unit 5 so that the temperature of the water in the pot 2 reaches a temperature near 100° C. The temperature near 100° C. is, for example, a temperature within the range of 100±5° C. The temperature of the water in the pot 2 is detected by, for example, the pot temperature sensor 12 or the steam temperature sensor. Further, the control unit 13 controls the pressure valve moving mechanism 63 so as to move the pressure valve 62 to the closed position at the start of the temperature raising process. Thereby, the steam discharge hole 42 is closed.

[0048] During the temperature increase process in the pot 2, the temperature of the water in the pot 2 rises above the gelatinization start temperature, and the gelatinization of the rice progresses. As the gelatinization of the rice progresses, an eluate containing starch is generated on the surface of the rice. Since the viscosity of this eluate is greater than that of water, it precipitates and accumulates on the bottom 22 of the pot 2. That is, the eluate tends to be unevenly distributed in the lower part of the object to be cooked.

[0049] In the temperature increase process, a temperature difference occurs between the part of the water in the pot 2 close to the inner surface of the pot 2 and the part far from the inner surface. Specifically, the water located near the inner surface of the pot 2 is likely to receive heat conducted from the pot 2 and becomes hotter than the water located away from the inner surface of the pot 2. Therefore, even when the average temperature of the water in the pot 2 has not reached 100°C, bubbles 9 (see FIG. 3) due to the vaporization of water are generated in the contact area 2a of the inner surface of the pot 2 with the water contained in the object to be cooked. Since the steam discharge holes 41 and 42 are closed, the pressure in the internal space SP2 rises due to the generation of the bubbles 9.

[0050] As shown in FIG. 2, in the temperature increase process, when the pressure in the internal space SP2 is greater than the atmospheric pressure, the internal space SP2 is depressurized by opening the steam discharge hole 42. Here, the "depressurization" in the description of this embodiment means depressurizing the pressure in the internal space SP2 from a pressure exceeding the atmospheric pressure to the atmospheric pressure.

[0051] Specifically, the control unit 13 pressurizes the internal space SP2 to a temperature increase pressure P1 (see FIG. 2) exceeding the atmospheric pressure, and then controls the pressure valve moving mechanism 63 to move the pressure valve 62 to the open position. As a result, the steam discharge hole 42 is opened, the internal space SP2 and the outside of the rice cooker are in fluid communication, and the pressure in the internal space SP2 drops from the temperature increase pressure P1 to the atmospheric pressure.

[0052] The movement of the object to be cooked and the eluate during the depressurization will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic cross-sectional view showing the movement of bubbles and eluate in the object to be cooked before depressurization during the temperature increase process. FIG. 4 is a schematic cross-sectional view showing the movement of bubbles and eluate in the object to be cooked during depressurization during the temperature increase process.

[0053] As shown in Fig. 3, before the pressure reduction in the temperature rising process, bubbles 9 due to the vaporization of water are attached to the contact area 2a on the inner surface of the pot 2. At this point before the pressure reduction, since the temperature of the water in the pot 2 is low, these bubbles 9 are small and tend to stay in the contact area 2a. Also, at the point before the pressure reduction, eluate 8 generated by the gelatinization of rice has started to accumulate on the bottom part 22 of the pot 2.

[0054] As shown in Fig. 4, when the pressure reduction occurs in the temperature rising process, the volume of the air inside the bubbles 9 increases due to the pressure reduction of the internal space SP2. As a result, the bubbles 9 are more likely to separate from the contact area 2a. When the bubbles 9 separate from the contact area 2a, they move upward in the water inside the pot 2. At this time, the eluate 8 on the bottom part 22 of the pot is lifted up by the upward-moving bubbles 9 and diffuses in the water. Thereby, the uneven distribution of the eluate 8 on the bottom part 22 of the pot is reduced.

[0055] Also, the air inside the pot 2 is rapidly discharged to the outside of the rice cooker through the steam discharge hole 42 during the pressure reduction. At this time, the rice to be cooked inside the pot 2 moves upward as if it is pulled upward along with the rapid movement of the air inside the pot 2. In other words, the upper surface 71 (for example, the water surface 72) of the rice to be cooked moves from the position before the pressure reduction shown by the dashed line in Fig. 4 to a position higher than that shown by the solid line. Along with the upward movement of the entire rice to be cooked, the eluate 8 that had settled on the bottom part 22 of the pot 2 is pulled upward and diffused in the rice to be cooked. Therefore, due to the movement of the bubbles inside the rice to be cooked and the upward movement of the entire rice to be cooked, the uneven distribution of the eluate 8 on the bottom part 22 of the pot 2 is reduced.

[0056] For example, when the temperature of the water in the pot 2 is 60°C or higher and the pressure in the internal space SP2 is the temperature-rising pressure P1, the control unit 13 controls the pressure valve moving mechanism 63 to move the pressure valve 62 to the open position. When the temperature of the water is 60°C or higher, that is, when the temperature of the water is equal to or higher than the rice gelatinization start temperature, in the object to be cooked, the gelatinization of the rice proceeds and there is a high possibility that eluate is generated. Therefore, by performing depressurization when the temperature of the water is 60°C or higher, the diffusion effect of the eluate due to the aforementioned depressurization can be obtained more reliably. Further, the higher the temperature of the water in the pot 2 during depressurization, the greater the number of bubbles 9 that leave the contact region 2a of the inner surface of the pot 2 during depressurization, and the larger the size of each bubble 9. Therefore, from the viewpoint of more reliably obtaining the diffusion effect of the eluate 8 due to the movement of the bubbles 9 in the water, in the temperature-rising process, the control unit 13 preferably moves the pressure valve 62 to the open position when the temperature of the water is 60°C or higher, 65°C or higher, 70°C or higher, 75°C or higher, or 80°C or higher.

[0057] In the example shown in FIG. 2, after the pressure in the internal space SP2 is pressurized to 1.3 atmospheres, which is the temperature-rising pressure P1, the control unit 13 moves the pressure valve 62 to the open position when the temperature of the water in the pot 2 is about 80°C.

[0058] The control unit 13 may lower the temperature-rising pressure P1 and lower the pressure in the internal space SP2 from the temperature-rising pressure P1 as the amount of the object to be cooked is larger. By lowering the temperature-rising pressure P1 when the amount of the object to be cooked is large, it is possible to suppress the water contained in the object to be cooked from being discharged to the outside of the pot 2 through the steam discharge hole 42 during depressurization. Further, by increasing the temperature-rising pressure P1 when the amount of the object to be cooked is small, even when the distance D1 (see FIG. 3) between the upper surface 71 of the object to be cooked and the inner lid 4 is large, the object to be cooked can be moved upward more reliably.

[0059] For example, the control unit 13 sets the temperature-rising pressure P1 to 1.4 atmospheres when the amount of rice contained in the object to be cooked is 1 go, 1.3 atmospheres when it is 2 go or 3 go, 1.2 atmospheres when it is 4 go, and 1.1 atmospheres when it is 5 go.

[0060] The amount of the cooked rice is estimated based on, for example, the heating rate of the cooked rice until the pressure valve 62 is opened in the temperature rising step. Also, as the amount of the cooked rice, the amount of the cooked rice detected by a weight sensor provided in the rice cooker, the amount of cooked rice selected via the display operation unit 34 at the start of cooking, etc. can also be adopted.

[0061] As shown in FIG. 2, when a predetermined time has elapsed since the steam discharge hole 42 was opened, the control unit 13 controls the pressure valve moving mechanism 63 to move the pressure valve 62 to the closed position. Thereby, the steam discharge hole 42 is closed, and the decompression of the internal space SP2 in the temperature rising step ends. The decompression time T1 from the opening to the closing of the pressure valve 62 is, for example, 10 seconds. Also, since the heating by the heating unit 5 continues, the internal space SP2 is pressurized again.

[0062] When the temperature of the water in the pot 2 reaches about 100° C., the process proceeds to the boiling maintenance step. In the example shown in FIG. 2, when 19 minutes have elapsed since the start of cooking, the temperature of the water in the pot 2 reaches 100° C., and the process has shifted from the temperature rising step to the boiling maintenance step.

[0063] The boiling maintenance step is a step of boiling and maintaining the water in the pot 2 after the temperature rising step. At the start of the boiling maintenance step, the control unit 13 controls the pressure valve moving mechanism 63 so as to maintain the pressure valve 62 in the closed position. Thereby, since the closing of the steam discharge hole 42 continues, the internal space SP2 is continuously pressurized from the temperature rising step.

[0064] In the first half stage of the boiling maintenance process where there is sufficient moisture in the pot 2, the control unit 13 closes the steam discharge hole 42 and pressurizes the internal space SP2 to a boiling pressure P2 higher than the temperature-raising pressure P1. In the present embodiment, the boiling pressure P2 is 1.5 atmospheres, which is higher than the temperature-raising pressure P1 of 1.3 atmospheres. That is, in the present embodiment, the boiling pressure P2 is the pressure at which the steam discharge hole 41 is opened by the movement of the closing member 611 of the pressure regulating valve 61. In the stage where there is sufficient moisture, the control unit 13 controls the pressure valve moving mechanism 63 so as to maintain the pressure valve 62 at the closed position. As a result, the internal space SP2 is pressurized and the boiling point of the water in the pot 2 rises. Further, the control unit 13 controls the heating unit 5 so that the temperature of the water in the pot 2 approaches the boiling point of the water at the pressure of the internal space SP2.

[0065] Here, when the above-described depressurization is performed in the temperature-raising process, the uneven distribution of the eluate on the bottom portion 22 of the pot 2 of the pot 2 is suppressed. Therefore, it is possible to suppress the unevenly distributed eluate from hindering the convection in the cooked rice and the heat conduction from the pot 2 to the cooked rice. As a result, the rate of temperature rise of the water in the pot 2 becomes faster, so that in the boiling maintenance process, the pressure in the internal space SP2 reaches the boiling pressure P2 earlier. In the example shown in FIG. 2, at the time when 22 minutes have elapsed since the start of rice cooking, the pressure in the internal space SP2 has reached the boiling pressure P2.

[0066] In the present embodiment, when the pressure in the internal space SP2 reaches 1.5 atmospheres, the steam discharge hole 41 is opened by the pressure regulating valve 61. Therefore, even when the steam discharge hole 42 is closed, the pressure in the internal space SP2 is maintained at 1.5 atmospheres.

[0067] When the pressure in the internal space SP2 reaches 1.5 atmospheres, which is the boiling pressure P2, the closing member 611 of the pressure regulating valve 61 moves upward against the biasing force of the spring 612, and the steam discharge hole 41 is opened. On the other hand, when the pressure in the internal space SP2 drops below 1.5 atmospheres, the closing member 611 is biased downward by the spring 612 and moves downward to close the steam discharge hole 41 again. Therefore, the pressure in the internal space SP2 is maintained at 1.5 atmospheres even when the pressure valve 62 controlled by the control unit 13 is in the closed position.

[0068] In the latter half of the boiling maintenance process when the moisture in the pot 2 decreases, the control unit 13 opens the steam discharge hole 42 to reduce the pressure in the internal space SP2 from the boiling pressure P2. For example, when the temperature of the water in the pot 2 rises close to the boiling point corresponding to the pressure in the internal space SP2, the control unit 13 controls the pressure valve moving mechanism 63 to move the pressure valve 62 to the open position. Thereby, the pressure in the internal space SP2 drops from the boiling pressure P2. Here, "close to the boiling point" includes the actual boiling point and the temperature deviated from the boiling point by the measurement error of the temperature of the water in the pot 2.

[0069] Specifically, in the latter half of the stage, the control unit 13 controls the pressure valve 62 so that the steam discharge hole 42 is opened. When the steam discharge hole 42 is opened, the internal space SP2 and the outside of the rice cooker are in fluid communication, and a rapid pressure reduction occurs in the internal space SP2. In the example shown in FIG. 2, the control unit 13 controls the pressure valve 62 to open the steam discharge hole 42 at the time when 22 minutes and 30 seconds have elapsed since the start of rice cooking.

[0070] That is, in the present embodiment, after 30 seconds have elapsed since the pressure in the internal space SP2 reached the boiling pressure P2 (1.5 atm), the control unit 13 controls the pressure valve 62 and the pressure valve moving mechanism 63 to open the steam discharge hole 42. Between the time when the pressure in the internal space SP2 reaches the boiling pressure P2 and the start of decompression, the temperature of the water in the pot 2 rises to near the boiling point of water at the boiling pressure P2 (for example, about 112 °C at 1.5 atm). During this time, the food to be cooked is heated at a temperature exceeding the boiling point of water at atmospheric pressure (about 100 °C) for a longer period of time. As a result, the amount of heat applied to the rice increases and the gelatinization of the rice is promoted, so that the stickiness and taste of the cooked rice can be further enhanced.

[0071] The states of the water and rice in the pot 2 during the decompression will be described with reference to FIGS. 5 and 6. FIG. 5 is a schematic cross-sectional view showing the states of the water and rice in the pot before decompression during the boiling maintenance step. FIG. 6 is a schematic cross-sectional view showing the states of the water and rice in the pot during decompression during the boiling maintenance step.

[0072] Before the decompression, the amount of moisture in the pot 2 is in a low state. For example, when the heating by the heating unit 5 is interrupted before the decompression, the water surface in the pot 2 is lower than the upper surface 73 of the rice. On the other hand, in the pot 2 during rice cooking, the entire rice in the pot 2 is covered with bubbles formed by moisture including the mother liquor. The upper surface 74 of the bubble is shown in FIG. 5.

[0073] During decompression in the boiling maintenance step, the air in the pot 2 is rapidly discharged to the outside of the rice cooker through the steam discharge hole 42. At this time, the rice in the pot 2 moves upward as if it is pulled upward along with the rapid movement of the air in the pot 2. At this time, the rice contained in the food to be cooked is in a state where gelatinization has progressed and has viscosity on the surface, and adheres to adjacent rice or the inner surface of the pot 2. Therefore, when the entire rice is pulled upward, as shown in FIG. 6, the upper surface 73 of the rice moves upward and the gap between the rice grains expands.

[0074] Also, due to a large pressure difference causing decompression, the temperature of the water in the pot 2 will temporarily exceed the boiling point corresponding to the pressure in the internal space SP2 immediately after the start of decompression, and the water will experience bumping boiling. At this time, the water at the bottom of the food to be cooked increases its volume greatly during the process of vaporizing into steam, and quickly flows upward through the gaps between the rice grains. Due to this flow of steam, the gaps between the rice grains are enlarged, and the upper surface 73 of the rice moves upward.

[0075] Also, due to the bumping boiling, most of the water that existed in the pot 2 before decompression evaporates and is discharged to the outside of the pot 2. The amount of water evaporated due to decompression increases as the pressure in the internal space SP2 before decompression is higher and the temperature of the water in the pot 2 is higher, because the difference between the boiling point of the water immediately after decompression becomes larger. Also, the water in the pot 2 is discharged to the outside of the pot 2 by being sucked into the steam discharge hole 42 during decompression. As a result, the amount of water present in the pot 2 after decompression decreases, so the rice in the pot 2 does not sink in the water after decompression in the boiling maintenance process. Therefore, the enlarged gaps between the rice grains are maintained even after the decompression. This enables the realization of fluffy cooked rice.

[0076] Note that the first half stage of the boiling maintenance process is all the time before half of the total boiling process time (it is not necessary to include the time from 19 minutes to 22 minutes and 30 seconds in FIG. 2, and it is sufficient to include a part of the time before that half). Also, the second half stage of the boiling maintenance process is all the time after half of the total boiling process time (it is not necessary to include the time from 22 minutes and 30 seconds to 26 minutes in FIG. 2, and it is sufficient to include a part of the time after that half). Different stages in the boiling maintenance process may intervene before the first half stage, between the first half stage and the second half stage, or after the second half stage. However, in this embodiment, the first half stage corresponds to the time before half of the total time, and the second half stage corresponds to the time after half of the total time.

[0077] In this embodiment, the latter half stage starts after half of the total time of the boiling maintenance process. That is, the control unit 13 maintains the pressure valve 62 in the closed position until at least half of the total time, pressurizes the internal space SP2 to a boiling pressure P2 higher than the heating pressure P1, and maintains the pressurized state of the internal space SP2. Further, the control unit 13 moves the pressure valve 62 to the open position after half of the total time, and reduces the pressure of the internal space SP2 from the boiling pressure P2.

[0078] Further, the control unit 13 may move the pressure valve 62 to the open position and reduce the pressure of the internal space SP2 from the boiling pressure P2 when a predetermined time (for example, 60 seconds) has elapsed since the pressure of the internal space SP2 detected by the pressure detection unit 35 has risen to 1.5 atmospheres.

[0079] Further, in the boiling maintenance process, the control unit 13 may increase the boiling pressure P2 as the cooking time selected by the display operation unit 34 is shorter, and reduce the pressure of the internal space SP2 from the boiling pressure P2. In this case, when the selected cooking time is short, the boiling point of the water in the pot 2 becomes higher compared to when the cooking time is long, and the water can be heated to a higher temperature. Therefore, even when the cooking time is short, sufficient heat can be applied to the rice.

[0080] For example, the control unit 13 sets the boiling pressure P2 to 1.5 atmospheres when the selected cooking time is 30 minutes, 1.4 atmospheres when it is 35 minutes, 1.3 atmospheres when it is 40 minutes, and 1.2 atmospheres when it is 50 minutes.

[0081] As shown in FIG. 2, when a predetermined time (for example, 10 seconds) has elapsed since the pressure valve 62 was opened, the control unit 13 controls the pressure valve moving mechanism 63 to move the pressure valve 62 to the closed position. Thereby, the steam discharge hole 42 is closed, and the decompression of the internal space SP2 in the latter half stage of the boiling maintenance process ends. The decompression time T2 from the opening to the closing of the pressure valve 62 is, for example, 10 seconds. Further, since the heating by the heating unit 5 continues, the internal space SP2 is pressurized again.

[0082] When most of the water in the pot 2 disappears, the temperature of the bottom 22 of the pot 2 rises above the boiling point of water. When it is detected that the detected temperature of the pot temperature sensor 12 has reached a predetermined temperature (for example, 130°C) above the boiling point, or when a predetermined time has elapsed from the start of the boiling maintenance step according to the selected rice cooking course, the steaming step is entered. In the example shown in FIG. 2, when 26 minutes have elapsed since the start of rice cooking, the detected temperature of the pot temperature sensor 12 has reached 130°C, and the process has shifted from the boiling maintenance step to the steaming step.

[0083] The steaming step is a step of evaporating excess moisture using the residual heat and steaming the rice. In the steaming step, the control unit 13 stops the heating operation of the heating unit 5 or adjusts the heating amount of the heating unit 5 so that the temperature of the object to be cooked in the pot 2 decreases. Further, the control unit 13 controls the pressure valve 62 and the pressure valve moving mechanism 63 so that the closed state of the steam discharge hole 42 is maintained.

[0084] At the start of the steaming step, the pressure in the internal space SP2 is higher than the atmospheric pressure. Thereafter, as the temperature in the pot 2 decreases and the steam in the pot 2 condenses, the pressure in the internal space SP2 gradually decreases.

[0085] When a predetermined time has elapsed since the start of the steaming step, or when the pressure in the internal space SP2 has dropped to a predetermined pressure, decompression in the steaming step is performed. In this decompression, the control unit 13 controls the pressure valve moving mechanism 63 to move the pressure valve 62 to the open position. As a result, the steam discharge hole 42 is opened, and the internal space SP2 and the outside of the rice cooker are in fluid communication. This decompression is performed to reduce the pressure in the internal space SP2 to the atmospheric pressure so that the lid can be safely opened after the rice cooking is completed.

[0086] During this pressure reduction, the control unit 13 gradually or gently reduces the pressure in the internal space SP2. As shown in FIG. 2, the pressure P3 in the internal space SP2 at the start of this pressure reduction is lower than the boiling pressure P2 in the aforementioned boiling maintenance step. In the present embodiment, the pressure P3 is 1.4 atmospheres. In the example shown in FIG. 2, at the time when 3 minutes and 30 seconds have elapsed since the start of the steaming step, the pressure in the internal space SP2 has dropped to the pressure P3, and the pressure reduction in the steaming step has started.

[0087] FIG. 7 is a diagram showing an enlarged part of the steaming step in FIG. 2. As shown in FIG. 6, in the present embodiment, the control unit 13 gradually reduces the pressure in the internal space SP2 by 0.1 atmospheres at a time. Specifically, after the steam discharge hole 42 is opened, when the pressure in the internal space SP2 has dropped by 0.1 atmosphere compared to before the opening of the steam discharge hole 42, the control unit 13 controls the pressure valve 62 and the pressure valve moving mechanism 63 to close the steam discharge hole 42. Thereafter, after the control unit 13 maintains the closed state of the steam discharge hole 42 for a predetermined time, it controls the pressure valve 62 and the pressure valve moving mechanism 63 to open the steam discharge hole 42 again. When this operation is repeated three times, the pressure in the internal space SP2 drops to 1.1 atmospheres. Finally, the control unit 13 opens the steam discharge hole 42 and controls the pressure valve 62 and the pressure valve moving mechanism 63 to reduce the pressure in the internal space SP2 to atmospheric pressure. When the pressure in the internal space SP2 drops to atmospheric pressure, the pressure reduction in the steaming step ends. At the same time, when the steaming step ends, all the rice cooking steps end.

[0088] The pressure reduction time T3 in the steaming step is longer than each of the pressure reduction time T1 (see FIG. 2) in the aforementioned temperature increase step and the pressure reduction time T2 (see FIG. 2) in the boiling maintenance step. Here, the pressure reduction time T3 is the time from when the internal space SP2 is reduced to the pressure P3 and the steam discharge hole 42 is opened until the pressure in the internal space SP2 drops to atmospheric pressure. In the present embodiment, the pressure reduction time T3 in the steaming step is 30 seconds.

[0089] Further, in the steaming process, the control unit 13 may gradually reduce the pressure in the internal space SP2. For example, the control unit 13 may control the pressure valve 62 and the pressure valve moving mechanism 63 to open the steam discharge hole 42 and gradually reduce the pressure in the internal space SP2 from 1.4 atmospheres to atmospheric pressure over 240 seconds.

[0090] By gradually or stepwise reducing the pressure in the internal space SP2, the eluate adhering to the surface of the rice moves upward along with the air flow in the pot 2 due to the reduced pressure, and it is possible to suppress the eluate from being concentrated on the upper part of the cooked rice. Therefore, it is possible to suppress the stickiness on the upper part of the cooked rice.

[0091] According to the rice cooker according to the present embodiment, in the latter half of the boiling maintenance process when the moisture in the pot 2 decreases, the control unit 13 opens the pressure valve 62 to reduce the pressure in the internal space SP2 from the boiling pressure P2. When the pressure is reduced from the boiling pressure P2, since the water in the pot 2 is already in a small amount, it is difficult for the water in the pot 2 to be sucked into the steam discharge hole 42 and discharged outside the pot 2. Therefore, even without providing a large space for relaxing the momentum of the water at the steam discharge hole 42, it is possible to perform a pressure reduction with a large pressure difference.

[0092] Further, when the pressure difference of the pressure reduction is large, the boiling point of the water in the pot 2 rapidly decreases, causing bumping boiling. At this time, the water in the gaps between the rice evaporates while increasing in volume, expanding the gaps. Also, since the pressure reduction is performed at a stage when the moisture in the pot 2 has decreased, after the pressure reduction, there is little water remaining in the pot 2 and the rice does not sink in the water. Therefore, the gaps between the rice are maintained in the expanded state due to the bumping boiling. As a result, it is possible to achieve a fluffy cooked rice. Therefore, it is possible to improve the taste of the rice while suppressing the increase in size of the rice cooker.

[0093] Further, according to the rice cooker according to the present embodiment, in the boiling maintenance step, when the temperature of the water in the pot 2 rises to near the boiling point corresponding to the pressure in the internal space SP2, the pressure valve 62 is opened to reduce the pressure in the internal space SP2 from the boiling pressure P2. As a result, the difference between the water temperature during depressurization and the boiling point of water at atmospheric pressure (about 100°C) increases, so the evaporation amount of water due to bumping boiling increases. Thereby, the gap between the grains of rice is further widened.

[0094] Further, according to the rice cooker according to the present embodiment, when a predetermined time has elapsed since the pressure in the internal space SP2 detected by the pressure detection unit 35 has risen to 1.5 atmospheres, the control unit 13 opens the pressure valve 62 to reduce the pressure in the internal space SP2 from the boiling pressure P2. Even between the time when the pressure in the internal space SP2 has risen to the boiling pressure P2 of 1.5 atmospheres and the time when the pressure valve 62 is opened, the water temperature in the pot 2 rises. Therefore, between the time when the pressure in the internal space SP2 reaches 1.5 atmospheres and the start of depressurization, the food to be cooked can be heated for a longer time at a temperature higher than the boiling point of water at atmospheric pressure. As a result, the amount of heat applied to the rice increases and the gelatinization of the rice is promoted, so that the stickiness and taste of the cooked rice can be further enhanced. In addition, the difference between the water temperature during depressurization and the boiling point of water at atmospheric pressure (about 100°C) can be further increased. Thereby, the evaporation amount of water due to bumping boiling increases, so the gap between the grains of rice is further widened.

[0095] Also, since the temperature of the water in the pot 2 approaches the boiling point at the pressure in the internal space SP2, the difference between the temperature of the water and the bubbles generated in the water and the temperature of the rice increases, and heat is more easily conducted to the rice. Thereby, the amount of heat for gelatinization required to cook the rice can be applied to the rice in a short time, and the rice cooking time can be shortened.

[0096] Further, according to the rice cooker according to the present embodiment, in the boiling maintenance step, the control unit 13 maintains the pressure valve 62 in the closed position before half of the total time of the boiling maintenance step, and after half of the total time of the boiling maintenance step, the pressure valve 62 is opened to reduce the pressure in the internal space SP2 from the boiling pressure P2. Thereby, the pressure reduction from the boiling pressure P2 can be more reliably performed at the stage when the water in the pot 2 decreases.

[0097] The higher the pressure in the internal space SP2, the higher the boiling point of the water in the pot 2. Therefore, assuming that heating is performed for the same time, the higher the boiling pressure P2, the more heat can be added to the rice before the pressure reduction in the boiling maintenance step.

[0098] According to the rice cooker according to the present embodiment, in the boiling maintenance step, the control unit 13 increases the boiling pressure P2 as the cooking time is shorter, and reduces the pressure in the internal space SP2 from the boiling pressure P2. That is, when the cooking time is short, the boiling pressure P2 is increased, and when the cooking time is long, the boiling pressure P2 is decreased. Thereby, the same amount of heat can be added to the rice even if the cooking time is different. Therefore, good cooking of rice can be achieved at various cooking times.

[0099] Further, according to the rice cooker according to the present embodiment, in the steaming step, the control unit 13 gradually or gently reduces the pressure in the internal space SP2. Thereby, it is possible to suppress the eluate 8 adhering to the surface of the rice from being sucked upward toward the steam discharge hole 42 during the pressure reduction in the steaming step and being unevenly distributed on the upper part of the object to be cooked.

[0100] Note that the present disclosure is not limited to the above-described embodiment, and can be implemented in various other modes. For example, in the above, it is assumed that pressure reduction is performed in the temperature rising step, but the present disclosure is not limited to this. For example, the pressure reduction from the boiling pressure P2 to the atmospheric pressure in the temperature rising step may not be performed.

[0101] FIG. 8 is a graph showing the operation of the rice cooker when the pressure reduction is not performed in the temperature rising process. In the example shown in FIG. 8, the control unit 13 controls the pressure valve 62 and the pressure valve moving mechanism 63 so as to maintain the steam discharge hole 42 at the open position from the start of the temperature rising process (at the 12-minute mark in FIG. 8) to the time of pressure reduction in the boiling maintenance process (at the 22 minute and 30 second mark in FIG. 8). Note that the control unit 13 may close the steam discharge hole 42 after the start of the temperature rising process in the temperature rising process, or may close the steam discharge hole 42 after entering the boiling maintenance process.

[0102] Also, in the above description, it is assumed that the pressure reduction in the temperature rising process is performed twice, but the present disclosure is not limited to this. The pressure reduction in the temperature rising process may be performed once or three or more times.

[0103] Also, in the above description, in the boiling maintenance process, when the temperature of the water in the pot 2 rises to near the boiling point corresponding to the pressure in the internal space SP2, the control unit 13 moves the pressure valve 62 to the open position, but the present disclosure is not limited to this. The timing at which the control unit 13 moves the pressure valve 62 to the open position may be, for example, when a predetermined time has elapsed since the start of the boiling maintenance process, when the detected temperature of the pot temperature sensor 12 reaches a predetermined temperature, or when the detected pressure of the pressure detection unit 35 reaches a predetermined pressure. Further, the timing may be, for example, when the rising speed of the detected temperature of the pot temperature sensor 12 becomes a predetermined speed or more, or when the rising speed of the detected pressure of the pressure detection unit 35 becomes less than a predetermined speed.

[0104] Further, in the above description, in the steaming process, the control unit 13 gradually decreases the pressure in the internal space SP2 by 0.1 atm at a time. However, the present disclosure is not limited to this. For example, in the steaming process, the pressure reduction amount per step of the internal space SP2 may be larger or smaller than 0.1 atm. Further, the control unit 13 may control the pressure valve 62 and the pressure valve moving mechanism 63 so as to repeat opening and then closing the steam discharge hole 42 for a predetermined time. By this control as well, a stepwise pressure reduction of the internal space SP2 can be realized. Further, when the control unit 13 gradually decreases the pressure in the internal space SP2, the pressure reduction amounts at each step of the internal space SP2 may be the same as or different from each other.

[0105] Further, in the above description, the heating unit 5 is a coil that inductively heats the pot 2. However, for example, it may be an electric heater.

[0106] Further, in the above description, the temperature of the internal space SP2 is estimated based on the detected temperature of the pot temperature sensor 12. However, the present disclosure is not limited to this. For example, the rice cooker may include a temperature detection sensor disposed between the outer lid 3 and the pot 2 instead of or in addition to the pot temperature sensor 12. In this case, the temperature of the internal space SP2 may be directly measured by the temperature detection sensor.

[0107] Further, in the above description, the pressure detection unit 35 is a pressure sensor that directly measures the pressure in the internal space SP2. However, the present disclosure is not limited to this. For example, the pressure detection unit 35 may be a pressure estimation unit built in the control unit 13 that estimates the pressure in the internal space SP2 based on the detected temperature of the pot temperature sensor 12 or the temperature detection sensor. In this case, the pressure estimation unit estimates the pressure in the internal space SP2 based on the saturated vapor pressure of water at various temperatures stored in the memory of the control unit 13 and the detected temperature. FIG. 9 shows a saturated vapor pressure curve indicating the saturated vapor pressure of water at various temperatures. For example, when the temperature of the internal space SP2 detected by the pot temperature sensor 12 is 105° C., the pressure estimation unit estimates that the pressure in the internal space SP2 is about 1.2 atm.

[0108] By appropriately combining any of the various embodiments or modifications thereof, it is possible to achieve the respective effects. Also, combinations of embodiments with each other, combinations of examples with each other, or combinations of an embodiment and an example are possible, and combinations of features from different embodiments or examples are also possible.

[0109] This disclosure is fully described in connection with preferred embodiments with reference to the accompanying drawings, but various variations and modifications will be apparent to those skilled in the art. Such variations and modifications should be understood to be included therein as long as they do not depart from the scope of this disclosure as defined by the appended claims.

Industrial Applicability

[0110] This disclosure is useful for rice cookers because it can improve the taste of the rice while suppressing the increase in the size of the rice cooker.

Explanation of Signs

[0111] 1 Rice cooker main body 1a Upper surface 2 Pot 2a Contact area 3 Outer lid 4 Inner lid 5 Heating unit 8 Eluate 9 Bubble 11 Pot storage section 12 Pot temperature sensor 13 Control unit 21 Flange section 22 Pot bottom 23 Peripheral wall section 31 Upper outer member 32 Lower outer member 33 Steam passage 34 Display operation section 35 Pressure detection section 41, 42 Steam discharge holes 43 Hole section 51 Bottom inner heating coil 52 Bottom external heating coil 53 Wall heating coil 61 Pressure regulating valve 62 Pressure valve 63 Pressure valve moving mechanism 71 Upper surface of the food to be cooked 72 Water surface 73 Upper surface of rice 74 Upper surface of bubbles 111 Side wall part 112 Bottom part 321 Recess 331 First opening end 332 Second opening end 611 Blocking member 612 Spring SP1 Exhaust space SP2 Internal space SP3 Pressure detection space

Claims

1. A pot containing the rice and water to be cooked, A heating unit for heating the pot, A lid for closing the opening of the pot, A pressure valve for opening and closing a steam discharge hole that communicates the internal space of the pot with the outside of the pot, A control unit for controlling the heating unit and the pressure valve, the control unit performing a rice cooking process including a temperature rising process of heating the pot until the temperature of the water reaches about 100°C, and a boiling maintaining process of boiling and maintaining the water after the temperature rising process, comprising, In the first half stage of the boiling maintaining process where there is sufficient moisture in the pot, the control unit closes the pressure valve to pressurize the internal space to a boiling pressure exceeding atmospheric pressure, and in the second half stage of the boiling maintaining process where the moisture in the pot decreases, the control unit opens the pressure valve to lower the pressure of the internal space from the boiling pressure, thereby expanding the gaps between the grains of rice. A rice cooker.

2. In the boiling maintaining process, when the temperature of the water in the pot rises to near the boiling point corresponding to the pressure of the internal space, the control unit opens the pressure valve to lower the pressure of the internal space from the boiling pressure. The rice cooker according to Claim 1.

3. Further comprising a pressure detection unit for detecting the pressure of the internal space, When a predetermined time has elapsed since the pressure of the internal space detected by the pressure detection unit has risen to 1.5 atmospheres, the control unit opens the pressure valve to lower the pressure of the internal space from the boiling pressure. The rice cooker according to Claim 1.

4. Further comprising a selection unit for selecting a rice cooking time, In the boiling maintaining process, the shorter the rice cooking time selected by the selection unit, the higher the control unit sets the boiling pressure and lowers the pressure of the internal space from the boiling pressure. The rice cooker according to Claim 1.

5. The control unit performs a steaming process of steaming the rice after the boiling maintenance process. The control unit closes the pressure valve to pressurize the internal space after the opening of the pressure valve in the boiling maintenance process, and in the steaming process, gradually or gently reduces the pressure in the internal space. The rice cooker according to any one of claims 1 to 4.

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