JP7809582B2 - rice cooker - Google Patents

Description

This disclosure relates to a rice cooker.

A rice cooker has been proposed that sends steam into the inner pot to prevent rice from drying out while being kept warm. The abstract of Patent Document 1 states, "In this rice cooker, the outer lid 2 is provided with an outer lid steam passage 12 that connects to the exhaust port 8, the inner pot 4, the inner lid 3 that covers the top of the inner pot 4 and is attached to the outer lid 2 and is provided with an inner lid steam passage 11 that connects to the outer lid steam passage 12, the condensation tray 21 that is attached to the underside of the inner lid 3, the lid heating means 16 on the outer lid 2 that heats the inner lid 3 and the condensation tray 21, and the control unit 20 that controls the lid heating means 16. The condensation tray 21 has a larger heat capacity than aluminum, and is therefore heat-resistant. It is made of a highly resistant material, its outer surface is in close contact with the underside of the inner lid 3, forming a space 24 between it and the inner lid 3, and has a bulge 21f that protrudes toward the inner lid 3 in a position that does not face the inner lid steam passage 11, and a steam hole 21e is provided on the upper surface of the bulge 21f, so that the space 24 between the condensation tray 21 and the inner lid 3 is filled with steam, causing condensation water to accumulate in the condensation tray 21, and the condensation water accumulated in the condensation tray 21 is heated by the lid heating means 16 to generate steam."

Japanese Patent Application Laid-Open No. 2015-221118

The rice may turn yellow when it dries out while being kept warm. As the rice life cycle changes, the time it is kept warm tends to become longer, making the rice more susceptible to yellowing. Therefore, a rice cooker that can adequately prevent yellowing while being kept warm is desired.
The problem that the present disclosure aims to solve is to provide a rice cooker that can sufficiently suppress yellowing of cooked rice.

The rice cooker of the present disclosure comprises an inner pot that is detachably attached to the main body and can contain rice, a lid that is attached to the main body so as to cover at least the upper opening of the inner pot and has a storage section for storing condensation water and a surface facing the inner pot, a first heating mechanism that heats the lid, a second heating mechanism that heats the upper part of the inner pot, and a control device that executes a heat retention process that controls the first heating mechanism and the second heating mechanism so that the temperature of the inner pot is higher than the temperature of the lid and the temperature difference between the lid and the inner pot is a temperature difference that can suppress dew dripping on the inner pot and the surface, and the control device further executes a fourth heat retention process that changes the amount of steam generated depending on the amount of rice, and in the fourth heat retention process, the control device generates steam by lowering the conduction rate of the first heating mechanism as the amount of rice increases .

FIG. 1 is a perspective view of a rice cooker according to the present disclosure. FIG. 1 is a perspective view of the rice cooker of the present disclosure with the lid open. FIG. 2 is a diagram showing the internal structure of the rice cooker of the present disclosure. 10 is a time chart during a keep-warm process in the rice cooker of the present disclosure.

Below, modes for implementing the present disclosure (referred to as embodiments) will be described with reference to the drawings. Within the description of one embodiment below, other embodiments that can be applied to the first embodiment will also be described as appropriate. The present disclosure is not limited to the following embodiments, and different embodiments can be combined or modified as desired without significantly impairing the effects of the present disclosure. Furthermore, the same components will be given the same reference numerals, and duplicate descriptions will be omitted. Furthermore, components having the same functions will be given the same names. The contents shown are merely schematic, and for the sake of illustration, the actual configuration may be changed, and some components may be omitted or modified between drawings, within the scope of not significantly impairing the effects of the present disclosure.

Figure 1 is a perspective view of a rice cooker 10 of the present disclosure. The rice cooker 10 comprises a main body 1 and a lid 2 that closes the top opening of the main body 1. The lid 2 is rotatably attached to the main body 1 via a hinge 24 (Figure 2). The lid 2 comprises an outer lid 21 and an inner lid 22 (Figure 2). The outer lid 21 is exposed to the outside. The top surface of the outer lid 21 is equipped with a steam vent 8, an operation unit 31, and a display unit 32. The steam vent 8 exhausts steam generated inside the inner pot 4 (Figure 2). The operation unit 31 is used to operate various menus and is, for example, a button. The display unit 32 displays various information such as the time, the progress of rice cooking, and the settings for various menus and is, for example, an LCD display. By operating the operation unit 31 while checking the display unit 32, the user can start rice cooking, set various menus, set timer cooking, etc.

Figure 2 is a perspective view of the rice cooker 10 of the present disclosure with the lid 2 open. Of the lid 2, the inner lid 22 (lid 2) has a surface 26 facing the inner pot 4. The inner pot 4 is detachably attached to the main body 1 and is capable of containing rice. Cooked rice is obtained by cooking the rice. The inner pot 4 is contained in the outer pot 7 (Figure 3). The inner lid 22 (lid 2) is attached to the main body 1 so as to cover at least the upper opening 4b of the inner pot 4. The lower peripheral edge of the inner lid 22 is provided with a gasket 23 that comes into tight contact with the flange portion 4a at the upper end of the inner pot 4 when the lid 2 is closed. The gasket 23 seals the upper opening 4b of the inner pot 4.

For example, during rice cooking and warming steps S1 to S3 (Figure 4), steam generated in the inner pot 4 flows through the steam vent 34 and recovery port 35 into the storage section 33 (Figure 3), which is the space formed between the outer lid 21 and the inner lid 22. The steam that flows into the storage section 33 is cooled by outside air through the outer lid 21 and turns into condensed water. Therefore, the storage section 33 is provided in the lid 2 and stores the condensed water. Furthermore, if the lid 2 is placed upright with condensed water on the inner lid 22, the condensed water flows down the surface of the inner lid 22 and flows into the storage section 33 through the recovery port 35 formed on the hinge 24 side. The condensed water that flows in is stored in the storage section 33.

Figure 3 is a diagram showing the internal structure of the rice cooker 10 of the present disclosure. As described above, the inner lid 22 has a reservoir 33 formed therein. The rice cooker 10 is equipped with a first heating mechanism 15. The first heating mechanism 15 heats the lid 2, and in the example of the present disclosure, heats the inner lid 22. The first heating mechanism 15 is, for example, an induction heating coil, and when current is applied to the induction heating coil, the opposing inner lid 22 is heated. The first heating mechanism 15 is equipped, for example, on the outer lid 21, and the entire surface of the inner lid 22 is heated evenly by the first heating mechanism 15.

The rice cooker 10 is equipped with a second heating mechanism 19. The second heating mechanism 19 heats the upper part of the inner pot 4 (e.g., the upper side) and is, for example, an induction heating coil. When current is applied to the induction heating coil, the opposing upper side wall of the inner pot 4 is heated. The second heating mechanism 19 can mainly heat the side wall (the side wall of the inner pot 4) above the rice contained in the inner pot 4.

The rice cooker 10 is equipped with a third heating mechanism 14. The third heating mechanism 14 heats the inner pot 4 from the bottom, and is, for example, an induction heating coil. When current is applied to the induction heating coil, the bottom of the opposing inner pot 4 is heated, thereby heating the entire inner pot 4, which has thermal conductivity.

The inner lid 22 comprises an inner lid steam passage 11 through which steam generated in the inner pot 4 passes, an outer lid steam passage 12 connected to the steam vent 8, and a pressure adjustment mechanism 13 placed on the top of the inner lid steam passage 11 and closing the inner lid steam passage 11. The pressure adjustment mechanism 13 comprises a pressure adjustment ball 13a and a pressure adjustment base 13b. The pressure adjustment ball 13a is placed on top of the pressure adjustment base 13b. The pressure adjustment ball 13a can be moved as desired by an opening mechanism 16 (e.g., a solenoid) operated by the control device 50, allowing the pressure in the inner pot 4 to be freely adjusted. The pressure adjustment base 13b is formed by narrowing the passage from the inner lid steam passage 11 that passes through the inner lid 22.

When the steam pressure inside the inner pot 4 exceeds a predetermined pressure, the pressure adjustment ball 13a is lifted, releasing the pressure through the outer lid steam passage 12 and discharging it outside the main body 1 through the steam vent 8. Furthermore, when the steam pressure falls below the predetermined pressure, the pressure adjustment ball 13a again closes the inner lid steam passage 11, causing the steam pressure to increase. This process is repeated until the pressure inside the inner pot 4 is adjusted to the predetermined pressure.

The rice cooker 10 is equipped with a control device 50. The control device 50 controls the operation of the rice cooker 10, and controls the operation of the first heating mechanism 15, second heating mechanism 19, and third heating mechanism 14 (e.g., turning on and off electricity, controlling the electricity rate when electricity is turned on, etc.). By controlling these, the control device 50 executes the rice cooking process (not shown) and keep-warm process S1 to S3 (Figure 4) described below. The specific functions of the control device 50 will be described later with reference to Figure 4.

The control device 50 is configured with, for example, a CPU (Central Processing Unit) 51, RAM (Random Access Memory) 52, and ROM (Read Only Memory) 53. The control device 50 is realized when a specific rice cooking program stored in ROM 53 is loaded into RAM 52 and executed by CPU 51.

The rice cooker 10 is equipped with a first temperature sensor 18 that measures the temperature of the inner pot 4. The first temperature sensor 18 is provided at the bottom of the outer pot 7 and is in contact with the outer bottom of the inner pot 4. The measurement value by the first temperature sensor 18 is input to the control device 50 as temperature information for the inner pot 4. The rice cooker 10 is equipped with a second temperature sensor 25 that measures the temperature of the lid 2 (inner lid 22). The second temperature sensor 25 is provided in contact with the inner lid 22. The measurement value by the second temperature sensor 25 is input to the control device 50 as temperature information for the inner lid 22.

The operation of the rice cooker 10 will now be described. Operation mainly includes the rice cooking process (not shown) and the keep-warm process S1 to S3. Rice cooking begins when the user places rice and water in the inner pot 4 and operates the operation unit 31 (Figure 1). The control device 50 heats the inner pot 4 according to the rice cooking program so as to execute the process set by the user. Heating of the inner pot 4 is performed by controlling the operation of the first heating mechanism 15, second heating mechanism 19, and third heating mechanism 14 based on the temperature information from the first temperature sensor 18 and second temperature sensor 25 and the amount of rice to be cooked.

Eventually, when the rice inside the inner pot 4 boils, the pressure regulation mechanism 13 activates its pressure regulation function, and steam that passes through the pressure regulation mechanism 13 is released from the steam vent 8. This regulates the amount of steam inside the inner pot 4, maintaining a constant pressure inside the inner pot 4. After that, when the water inside the inner pot 4 evaporates, the temperature at the bottom of the inner pot 4 rises rapidly. When the first temperature sensor 18 detects this rise, the control device 50 reduces the heating and transitions to the steaming process. After the rice has been steamed for a certain period of time, cooking is complete. When cooking is complete, the control device 50 transitions the operation of the rice cooker 10 to the keep-warm process S1.

Figure 4 is a time chart of the warming steps S1 to S3 in the rice cooker 10 of the present disclosure. Below, Figure 4 will be described with reference to Figure 3 as well. The flow shown in Figure 4 is executed by the control device 50 unless otherwise specified. The warming step S1 (first warming step), the warming step S2 (first warming step, third warming step), and the warming step S3 (second warming step) are executed in this order. The warming step S3 is followed by the warming step S1.

The keeping-warm step S1 is a step of lowering the temperature of the inner pot 4 to the adjustment temperature T1 (e.g., 65°C). During the keeping-warm step S1, the first heating mechanism 15 and the second heating mechanism 19 are energized, while the third heating mechanism 14 is not energized. The keeping-warm step S2 is a step of generating steam while maintaining a constant temperature of the inner pot 4 (e.g., 65°C). During the keeping-warm step S2, the first heating mechanism 15, the second heating mechanism 19, and the third heating mechanism 14 are all energized. The first heating mechanism 15 and the third heating mechanism 14 are energized at the same time. The keeping-warm step S3 is a step of raising the temperature of the inner pot 4 while generating steam. During the keeping-warm step S3, the first heating mechanism 15, the second heating mechanism 19, and the third heating mechanism 14 are all energized. The first heating mechanism 15 and the third heating mechanism 14 are energized at the same time.

In the example of the present disclosure, steam is not generated in the heat retention step S1, but is generated in the heat retention steps S2 and S3. Steam is generated by heating the condensed water stored in the storage section 33. Meanwhile, in the heat retention step S1, condensed water is stored in the storage section 33, and in the heat retention step S2, condensed water is stored in the storage section 33 when steam is not being generated. In the heat retention step S3, condensed water is not stored in the storage section 33. Therefore, in the heat retention steps S1 to S3, the storage of condensed water and the above-mentioned generation using the stored condensed water are alternated.

The control device 50 executes the heat retention steps S1 and S2, which control the first heating mechanism 15 and the second heating mechanism 19 so that the temperature of the inner pot 4 is higher than the temperature of the inner lid 22 (lid 2) and the temperature difference between the inner lid 22 and the inner pot 4 is large enough to prevent dew from dripping on the inner pot 4 and the surface 26. However, in the heat retention step S2, this control is executed only when condensed water is accumulated, and the step in which this control is executed corresponds to the first heat retention step.

This type of control can suppress the formation of condensation water in the inner pot 4, which becomes relatively hot, and promote condensation on the inner lid 22, which becomes relatively cold. In addition, by maintaining the temperature difference between the inner lid 22 and the inner pot 4 at the above temperature difference, it is possible to suppress dripping of condensation water that forms on the surface 26 of the inner lid 22 and increase the amount of moisture that exists as steam. As a result, the steam that flows into the storage section 33 can be cooled and stored by outside air, increasing the amount of steam over a long period of time. As a result, the amount of steam that comes into contact with the rice in the inner pot 4 increases, suppressing yellowing of the rice due to drying.

In the example disclosed herein, the control device 50 controls the first heating mechanism 15 and the second heating mechanism 19 during the warming steps S1 and S2 so that the temperature difference between the inner lid 22 and the inner pot 4 is 3°C or less, preferably 2°C or less, and more preferably 1.5°C or less, although this temperature difference is not limited to this. This type of control can prevent dripping from the surface 26.

In the heat retention process S1, the power supply rate of the first heating mechanism 15 is reduced, for example, in stages, the power supply rate of the second heating mechanism 19 is controlled to a constant value, and the power supply rate of the third heating mechanism 14 is set to 0 (power supply is stopped). The power supply rate is defined as the ratio of the output of the first heating mechanism 15, second heating mechanism 19, and third heating mechanism 14 to the rated output. The higher the power supply rate, the more heat is applied.

As the temperature measured by the first temperature sensor 18 decreases, the power supply rate of the first heating mechanism 15 decreases, for example, in stages. However, the power supply rate may also decrease gradually. In this way, the temperature difference between the temperature of the inner pot 4, which is the temperature measured by the first temperature sensor 18, and the temperature of the inner lid 22 can be maintained at a certain level (or may be constant), thereby suppressing the promotion of condensation and dripping caused by a large temperature difference.

During the heat retention steps S1 and S2, the control device 50 sets the power supply rate of the second heating mechanism 19 higher than the power supply rate of the first heating mechanism 15. However, as described above, during the heat retention step S2, this control is only executed when condensed water is being stored. This keeps the temperature of the inner pot 4 higher than that of the inner lid 22, suppresses dripping from the inner pot 4, and increases the amount of steam flowing into the storage section 33, allowing more condensed water to be stored.

When the temperature of the inner pot 4 falls below the adjustment temperature T1, the control device 50 executes the heat retention process S2. In the example disclosed herein, the adjustment temperature T1 is 65°C, but is not limited to this temperature and can be, for example, 57°C or higher, preferably 60°C or higher, and more preferably 63°C or higher.

In the keep-warm step S2, when the temperature of the inner pot 4 falls below the adjusted temperature T1, the inner pot 4 is heated by energizing the first heating mechanism 15 and the second heating mechanism 19. At the same time, the third heating mechanism 14 is energized at a lower energization rate than the energization rate used in the rice cooking step (not shown) performed before the keep-warm steps S1 to S3, heating the inner pot 4 from the bottom. As a result, the temperature of the inner pot 4 rises above the adjusted temperature T1.

While the first heating mechanism 15, second heating mechanism 19, and third heating mechanism 14 are energized, i.e., while the rice is being heated, the control device 50 controls the first heating mechanism 15 and the second heating mechanism 19 so that the energization rate of the first heating mechanism 15 is higher than the energization rate of the second heating mechanism 19. This allows the condensed water in the storage section 33 (Figure 3) to evaporate, generating steam, which can then come into contact with the rice as it is being heated, making the rice moist.

When the temperature of the inner pot 4 reaches or exceeds the adjusted temperature T1 due to the application of current to the first heating mechanism 15, second heating mechanism 19, and third heating mechanism 14, the control device 50 applies current to these mechanisms so that the current flow rate of the second heating mechanism 19 is higher than that of the first heating mechanism 15, as in the warming step S1 described above. This promotes the accumulation of condensed water in the reservoir 33 while the temperature of the rice is decreasing, as in the warming step S1. At the same time, the control device 50 applies current to the third heating mechanism 14 at a lower current flow rate than that used in the rice cooking step (not shown) performed before the warming steps S1 to S3.

When the temperature of the inner pot 4 falls below the adjustment temperature T1 again, the control described at the beginning of the explanation of the keep-warm step S2 is performed again. That is, steam can be generated by increasing the power supply rate of the first heating mechanism 15 above that of the second heating mechanism 19. This keeps the rice moist and prevents yellowing. In particular, in the rice cooker 10, condensed water is stored in the storage section 33 during the keep-warm steps S1 and S2. This allows a large amount of condensed water to be stored, allowing steam to be generated for a long period of time.

In this way, the control device 50 executes the heat retention process S2 (third heat retention process) which maintains the temperature within a predetermined range (a range that includes the adjusted temperature T1) while generating steam. Steam is generated, for example, by heating the condensed water that accumulates in the heat retention processes S1 and S2. This allows steam to come into contact with rice that is within the predetermined temperature range, preventing the rice from drying out.

In the example disclosed herein, the control device 50 generates steam intermittently during the warming process S2. That is, steam is not generated constantly during the warming process S2, but rather steam generation and condensation water storage are repeatedly switched between at the adjusted temperature T1. This makes it possible to more effectively prevent the rice from drying out and yellowing compared to when steam is generated constantly.

After a predetermined time (e.g., two to four hours) has elapsed since the start of the warming step S2, the control device 50 executes the warming step S3 (second warming step), which heats the rice at a temperature increase rate that suppresses the yellowing of the rice caused by cooking the rice and also suppresses bacterial growth. Executing the warming step S3 not only suppresses yellowing, but also kills bacteria, allowing the rice to last longer.

The inventors' research has shown that the greater the temperature rise, the more likely yellowing occurs. On the other hand, if the temperature rise is small or the temperature rise rate is slow, bacteria will not be killed. Therefore, in the example of the present disclosure, the temperature rise rate in the warming step S3 is a predetermined rate of 15°C or more and 20°C or less per hour, although this rate is not limited to this rate. By raising the temperature at a predetermined rate within this range, yellowing can be suppressed, bacteria can be killed, and the rice can be kept fresh for a longer period of time.

In the warming step S3, in the example disclosed herein, the control device 50 controls the first heating mechanism 15, the second heating mechanism 19, and the third heating mechanism 14 to heat the rice from the adjusted temperature T1 (e.g., 65°C) to the adjusted temperature T2 (e.g., 80°C) at a rate of 15°C to 20°C per hour. The control device 50 relatively increases the power supply rate of the first heating mechanism 15 immediately after the start of the warming step S3, and then relatively decreases it after a predetermined time has elapsed. Thus, the control device 50 gradually decreases the power supply rate of the first heating mechanism 15. By increasing the power supply rate relatively immediately after the start, the condensed water stored in the storage section 33 of the inner lid 22 can be heated to generate steam, which can then be returned to the rice. This allows the rice temperature to be increased while maintaining its moisture content. In particular, the presence of a large amount of steam when the rice begins to heat up can give the rice a glossy texture. Furthermore, by gradually decreasing the power supply rate, steam can be generated for a longer period of time compared to when steam is continuously generated at a high temperature. When the temperature of the inner pot 4 reaches the adjustment temperature T2, the control device 50 repeats the warming process S1 and subsequent steps.

These heat retention steps S1 to S3 allow steam to be generated for a long period of time, while keeping the rice moist and maintaining its whiteness and deliciousness for a long period of time.

In another embodiment, the control device 50 executes heat retention steps S2 and S3 (fourth heat retention step) that change the amount of steam generated depending on the amount of rice contained in the inner pot 4. This allows the steam to come into contact with the entire rice, preventing uneven contact and preventing localized yellowing due to insufficient steam. The amount of rice contained can be determined, for example, based on changes in the measurement value (rate of temperature rise) from the first temperature sensor 18, or it can be determined based on operation by the user via the operating unit 31 (Figure 1).

At this time, in the heat retention steps S2 and S3, the control device 50 generates steam by lowering the power supply rate of the first heating mechanism 15 as the amount of rice stored increases. When the amount of rice is large, temperature fluctuations inside the inner pot 4 are small. Therefore, temperature fluctuations in the inner lid 22 facing the inner pot 4 are small, and even when the power supply to the first heating mechanism 15 is stopped, the storage section 33 is less likely to cool. For this reason, even at a low power supply rate, condensation water stored in the storage section 33 can be evaporated to generate steam. This reduces the power consumption required to generate steam.

1 Main body 10 Rice cooker 11 Inner lid steam passage 12 Outer lid steam passage 13 Pressure adjustment mechanism 13a Pressure adjustment ball 13b Pressure adjustment base 14 Third heating mechanism 15 First heating mechanism 16 Opening mechanism 18 First temperature sensor 19 Second heating mechanism 2 Lid 21 Outer lid 22 Inner lid 23 Gasket 24 Hinge 25 Second temperature sensor 26 Surface 31 Operation unit 32 Display unit 33 Storage unit 34 Steam vent 35 Recovery port 4 Inner pot 4a Flange unit 50 Control device 51 CPU
52 RAM
53 ROM
7 Outer pot 8 Steam vent S1 Heat retention process (first heat retention process)
S2 Heat retention process (first heat retention process, third heat retention process, fourth heat retention process)
S3 Heat retention process (second heat retention process, fourth heat retention process)
T1 Adjustment temperature T2 Adjustment temperature

Claims (7)

An inner pot that can be detached from the main body and can hold rice,
A lid is attached to the main body so as to cover at least the upper opening of the inner pot, and has a reservoir for storing condensed water and a surface facing the inner pot;
a first heating mechanism that heats the lid;
a second heating mechanism for heating an upper portion of the inner pot;
A control device that executes a first heat retention process to control the first heating mechanism and the second heating mechanism so that the temperature of the inner pot is higher than the temperature of the lid and the temperature difference between the lid and the inner pot is a temperature difference that can suppress dew dripping on the inner pot and the surface ,
The control device
Furthermore, a fourth heat-retaining step is carried out in which the amount of steam generated is changed depending on the amount of rice.
In the fourth warming step, the larger the amount of rice, the lower the power supply rate of the first heating mechanism to generate steam.
A rice cooker characterized by the above. The rice cooker according to claim 1, wherein the control device controls the first heating mechanism and the second heating mechanism so that the temperature difference between the lid and the inner pot is 3°C or less during the first warming process. When the ratio of the output of the first heating mechanism and the second heating mechanism to the rated output is defined as a power duty ratio,
The rice cooker according to claim 1 , wherein the control device sets a power supply rate of the second heating mechanism higher than a power supply rate of the first heating mechanism in the first warming step. The rice cooker according to claim 1, wherein the control device executes a second warming step of heating the cooked rice at a temperature increase rate that suppresses yellowing of the cooked rice caused by cooking the rice and also suppresses bacterial growth. The rice cooker according to claim 4, wherein the temperature rise rate is a predetermined rate of 15°C to 20°C per hour. The rice cooker according to claim 1 , wherein the control device executes a third warming step of maintaining the temperature within a predetermined range while generating steam. The rice cooker according to claim 6 , wherein the control device generates the steam intermittently.