JP2020195741A - rice cooker - Google Patents

Abstract

To realize ideal rice cooking while improving a taste of cooked rice.SOLUTION: A rice cooker 10 includes a bottomed cylindrical rice cooking pot 12, a plurality of coils 21A to 21C for induction-heating the rice cooking pot 12, a detection part 36A, 36B for detecting a temperature of the inside of the rice cooking pot 12, a switching part 48 for switching a power supply state to the plurality of the coils 21A to 21C, and a control part 45 which controls the switching part 48 and the plurality of the coils 21A to 21C for performing rice cooking processing including a preheating process, a temperature rising process, and a boiling maintenance process. The switching part 48 switches the power supply state in a manner to include at least a first state in which the power is supplied to one or more first coils 21A and the other are blocked and a second state in which the power is supplied to one or more second coils 21B and the other are blocked. The temperature rising state includes a first step continuing from the preheating process and a second step continuing to the boiling maintenance process. A first period Sb of the first step in which the power supply state is switched by the switching part 48 is longer than a second period Sc of the second step.SELECTED DRAWING: Figure 4

Description

The present invention relates to a rice cooker.

Patent Document 1 discloses a rice cooker in which three coils are arranged at intervals in the circumferential direction on the bottom of a bottomed tubular rice cooker. In this rice cooker, the rice cooker is induced and heated by the coils while switching the energized state in a predetermined order so that one of the three coils is energized and the rest is cut off.

JP-A-2018-61573

Patent Document 1 describes that the energization state of the coil is switched at predetermined time intervals. However, the rice cooker of Patent Document 1 has room for improvement in improving the taste of cooked cooked rice.

An object of the present invention is to provide a rice cooker capable of improving the taste of cooked cooked rice and realizing ideal cooked rice.

In one aspect of the present invention, a bottomed tubular rice cooker, a plurality of coils arranged side by side in the circumferential direction around the axis of the rice cooker, and inducing and heating the rice cooker, and the temperature inside the rice cooker are heated. A detection unit to detect, a first state in which at least one or more first coils of the plurality of coils are energized and the rest are cut off, and one of the plurality of coils other than the first coil. A switching unit that switches the energized state of the plurality of coils, and the switching unit and the plurality of coils are controlled so as to include a second state in which one or more second coils are energized and the rest are cut off. The preheating step of heating the rice cooker so that the detection temperature by the detection unit maintains the predetermined preheating temperature, and the above-mentioned so as to raise the detection temperature to a predetermined boiling temperature higher than the preheating temperature. The rice cooker is provided with a control unit that executes a rice cooking process including a temperature raising step of heating the rice cooker and a boiling maintenance step of heating the rice cooker so that the detected temperature maintains the boiling temperature. The first cycle of the first step, which has a first step continuous with the preheating step and a second step continuous with the boiling maintenance step, and the energization state is switched by the switching unit, is the second step. Provide a rice cooker that is longer than the second cycle of.

In this rice cooker, the energization state is switched so that a predetermined coil among a plurality of coils is energized by the switching unit, so that per unit area is compared with the case where the entire rice cooker is heated by one coil. The power that can be put into the rice cooker (that is, the amount of heating) can be increased. Therefore, the local part of the rice cooking pot can be concentrated and heated with a large amount of heat.

In the temperature raising step, the cycle for switching the energized state of the coil is different between the first step continuous with the preheating step and the second step continuous with the boiling maintenance step, and the first cycle of the first step is the second step. It is longer than the second cycle of. In the first stage, which is close to the preheating temperature, the heating stop time due to the switching of the energized state is shorter than in the second stage, so that the inside of the rice cooking pot can be heated faster than in the second stage. Therefore, the temperature inside the cooked rice pot can be quickly raised to a temperature at which reducing sugars that contribute to the taste (sweetness and luster) of cooked rice are produced. In the second stage, which is close to the boiling temperature, the energized state is switched earlier than in the first stage, so that convection due to bubbles generated by local heating can be promoted. Therefore, since the cooked rice can be agitated efficiently, it is possible to cook cooked rice without uneven heating. As a result, the taste of cooked cooked rice can be improved and ideal cooked rice can be realized.

The temperature raising step is composed of only the first step and the second step. According to this aspect, a large amount of heat can be reliably input in the early stage of the temperature raising step in which rapid temperature rise is desirable, and convection can be promoted in the latter stage of the temperature rising step in which efficient stirring is desirable.

The control unit is defined with a transition temperature that corresponds to the temperature at which the preheating temperature of rice and rice begins to be preheated, is higher than the preheating temperature, and is lower than the boiling temperature. In the temperature raising step, the control unit is the detection unit. When the temperature detected by the above rises to the transition temperature, the transition from the first stage to the second stage is performed. According to this aspect, the temperature inside the cooked rice can be raised quickly to the temperature at which reducing sugars are produced, and then the inside of the cooked rice that has started pregelatinization can be efficiently stirred, so that the taste of cooked cooked rice is improved. , Ideal rice cooking can be realized.

The first energizing time of the first cycle is set in the range of 5 seconds or more and 15 seconds or less. According to this aspect, a part of the rice cooking pot can be reliably heated.

The second energizing time of the second cycle is set to be shorter than the first energizing time in the range of 2.5 seconds or more and 7.5 seconds or less. According to this aspect, it is possible to convection the inside of the rice cooking pot without bias while heating a part of the rice cooking pot.

With the rice cooker of the present invention, the taste of cooked cooked rice can be improved and ideal cooked rice can be realized.

The schematic diagram of the rice cooker which concerns on embodiment of this invention. A block diagram showing the arrangement of coils for induction heating and the configuration of a rice cooker. A time chart showing an example of rice cooking. A time chart showing the relationship between the switching cycle and the temperature in the middle-papping process. Flow chart of rice cooking process. Flowchart of the middle-sized process. A time chart showing a modified example of the middle-sized process. A time chart showing other variations of the middle-papper process. The bottom view which shows the modification of the coil arrangement.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a rice cooker 10 according to an embodiment of the present invention. The rice cooker 10 includes a rice cooker main body 17 in which a rice cooker pot 12 is arranged, and a lid 26 attached to the rice cooker main body 17 so as to be openable and closable, and a plurality of rice cooker main bodies 17 (three in the present embodiment). ) Is a multi-coil type in which the coils 21A to 21C are arranged. In the present embodiment, by optimally energizing the coils 21A to 21C at an appropriate time, the pregelatinization of cooked rice in the cooked rice pot 12 is promoted, and the taste of cooked cooked rice is improved.

(Overview of rice cooker)
The rice cooker 12 is made of a magnetic material and has an integral structure formed by press working or casting. The rice cooking pot 12 has a bottomed tubular shape, and includes a disk-shaped bottom portion 13, a cylindrical outer peripheral portion 14 in which the axis A passes through the center of the bottom portion 13, and a curved portion 15 that connects them.

The rice cooker main body 17 includes an accommodating portion 18 for detachably accommodating the rice cooker 12. The accommodating portion 18 has a bottomed tubular shape including a metal inner body 19 and a resin (non-conductive material) protective frame 20, and is provided below an opening formed on the upper surface of the rice cooker main body 17. There is. By arranging the rice cooking pot 12 in the accommodating portion 18, the axis line of the protective frame 20 and the axis line A of the rice cooking pot 12 coincide with each other. On the outside of the protective frame 20, three coils 21A to 21C are arranged so as to be arranged in the circumferential direction about the axis A of the rice cooking pot 12. A holder 23 for holding the ferrite core 22 is arranged outside the individual coils 21A to 21C, and the coils 21A to 21C are held (fixed) between the holder 23 and the protective frame 20.

The coils 21A to 21C have a shape in which a plurality of windings are wound in an elliptical ring shape, and an eddy current is generated by energizing a high-frequency current to induce and heat the rice cooker 12. The arrangement of the coils 21A to 21C with respect to the rice cooking pot 12 is shown in FIG. With reference to FIG. 2, the coils 21A to 21C are arranged at intervals in the circumferential direction with the axis A of the rice cooking pot 12 as the center. Referring to FIG. 1, the individual coils 21A to 21C are arranged around the curved portion 15 from the bottom portion 13 to the outer peripheral portion 14 of the rice cooking pot 12, and are fixed to the outer surface of the protective frame 20. However, the coils 21A to 21C may be arranged in the protective frame 20 so as to be located only outside the bottom portion 13, or may be arranged in the protective frame 20 so as to be located outside from the bottom portion 13 to the curved portion 15. Good.

As shown in FIG. 1, the lid 26 is rotatably attached to the hinge connecting portion 24 on the back of the rice cooker main body 17 located on the right side in FIG. The lid 26 is provided with a heat radiating plate 27 on the inner surface side (lower side in FIG. 1) facing the rice cooking pot 12. An inner lid 28 that closes the upper end opening of the rice cooking pot 12 is provided on the lower surface of the heat radiating plate 27. The inner lid 28 may be detachable or non-removable with respect to the lid 26. A lid heater 29 is provided on the upper surface of the heat radiating plate 27 to heat the inner lid 28 via the heat radiating plate 27 and evaporate the dew adhering to the inner lid 28.

The lid 26 is formed with an exhaust passage 30 for discharging the steam in the rice cooker 12 to the outside. The inlet of the exhaust passage 30 is the exhaust port 31 formed in the inner lid 28, and the outlet of the exhaust passage 30 is the exhaust port 33 of the steam port set 32 provided on the back side of the lid 26. A gap 34 is provided between the inner lid 28 and the heat radiating plate 27 at a predetermined interval, and the gap 34 constitutes a communication passage for communicating the vent 31 and the steam port set 32. The configuration of the exhaust passage 30 including the steam port set 32 can be changed as needed.

Subsequently, referring to FIG. 1, two sensors 36A and 36B are arranged in the rice cooker 10 as detection units for detecting the temperature in the rice cooker 12. The first sensor 36A is arranged on the rice cooker main body 17, and the second sensor 36B is arranged on the lid body 26. The sensor 36A for the pot is arranged so as to penetrate the accommodating portion 18 and come into contact with the outer surface of the rice cooking pot 12, and detects the cooked rice temperature or the cooked rice temperature containing water inside through the rice cooking pot 12. The sensor 36B for the lid is arranged so as to come into contact with the heat radiating plate 27, and detects the temperature in the rice cooking pot 12 (in the void 34) via the heat radiating plate 27.

Referring to FIG. 2 together, the rice cooker 10 includes an operation panel 38 having a plurality of switches (input units) 39 and a liquid crystal panel (display unit) 40. Although the operation panel 38 is formed on the upper surface of the front surface of the rice cooker main body 17 in the present embodiment, it may be formed on the upper surface of the lid body 26, and its arrangement can be changed as needed. The plurality of switches 39 include a rice cooking switch for starting the rice cooking process, a heat retaining switch for starting the heat retaining process, and a pick-up switch for ending the rice cooking process and the heat retaining process. The liquid crystal panel 40 displays the selected state of the rice cooking menu and the current operating state.

As shown in FIG. 1, a control board 43 is arranged on the front side of the rice cooker main body 17 via a holder 42. The control board 43 is provided with a control unit 45 for controlling electrical components (see FIG. 2). The control unit 45 is composed of a single microcomputer or a plurality of microcomputers, and other electronic devices. As shown in FIG. 2, the control unit 45 includes a program for executing the rice cooking process and the heat retention process, and a storage unit (memory) 46 in which the set values (temperature and time) used in the program are stored. Further, the control unit 45 includes a time measuring unit (timer) 47 for measuring time.

Subsequently referring to FIG. 2, the control unit 45 includes a switching unit 48 for switching the energization state of the coils 21A to 21C. The coils 21A to 21C are individually connected to the switching unit 48, and an inverter circuit (power supply unit) 49 for inputting power to the coils 21A to 21C is connected to the switching unit 48. The switching unit 48 is composed of, for example, switch elements arranged for each of the coils 21A to 21C, and is formed on the control board 43 or a different circuit board.

The switching unit 48 switches the energized state in a predetermined order so that one of the three coils 21A to 21C is energized and the remaining two coils are de-energized. That is, the switching unit 48 electrically connects the coil (first coil) 21A to the coil (second coil) 21B in the first energized state (first state) in which the other coils 21B and 21C are cut off. The second energized state (second state) in which the other coils 21A and 21C were cut off by connecting to the coil (third coil), and the third energized state in which the other coils 21A and 21B were cut off by electrically connecting the coil (third coil) 21C. The state is switched in the order of the state (third state), and this switching operation is repeated.

When the switching unit 48 switches the energized state, the energization of the coil before switching (for example, coil 21A) and the energization of the coil after switching (for example, coil 21B) are set so as not to overlap. However, at the time of switching, if the total power input to the coil before switching and the coil after switching is equal to or less than the rated power, the energization of the coil before switching and the energization of the coil after switching may be overlapped. ..

In general, most switchboards installed in Japanese homes have 20 amperes and outlets of 15 amperes, so the maximum rated power that can be input per unit time in electrical equipment including this type of rice cooker 10. It is 1500W. In the case of a rice cooker using one coil that covers the entire bottom portion 13, the entire rice cooker pot 12 is induced and heated by a heating amount corresponding to the rated power. On the other hand, in the rice cooker 10 of the present embodiment, the rated power is applied to one of the three coils 21A to 21C at the maximum, so that the heating region of 1/3 of the corresponding rice cooker 12 is increased. Induction heating is performed with the maximum concentration of heating amount according to the rated power. Therefore, as compared with the rice cooker using one coil, the rice cooker 10 of the present embodiment can increase the maximum heating amount per unit area of the rice cooker 12. Therefore, in the present embodiment, the local portion of the rice cooking pot 12 can be concentrated and heated with a large amount of heat.

Next, the rice cooking process by the control unit 45 will be specifically described.

FIG. 3 is a time chart showing an example of rice cooking processing. Referring to FIG. 3 together with FIG. 5, the rice cooking process includes a preheating step (step S1), a middle-papping step (step S2), a boiling maintenance step (step S3), a cooking step (step S4), and an unevenness step. (Step S5), and these steps are executed in this order. When this rice cooking process is completed, the heat retention process is subsequently executed.

In the preheating step, the rice cooking pot 12 is heated (temperature controlled) so that the cooked rice absorbs water so as to maintain a predetermined preheating temperature (for example, 40 ° C.). In this preheating step, the coils 21A to 21C are sequentially duty-controlled with an output of 66% of the rated power, and on / off control is performed based on the detection temperature TP or TL of the sensor 36A or 36B. When the specified time elapses (the transition condition is satisfied), the preheating process ends. For example, the transition time is 20 minutes in the case of normal rice cooking and 10 minutes in the case of reserved rice cooking.

In the middle-papping step (heating step), the rice cooking pot 12 is heated at a high output until the boiling temperature becomes higher than the preheating temperature, and the water inside is boiled in a short time. In this middle step, the coils 21A to 21C are sequentially controlled to maintain the on state at an output of 100% of the rated power. Further, in the middle-papping step, the rice cooking capacity is determined by the time (temperature rise gradient) required for raising the temperature from the predetermined first set temperature to the second set temperature. When the detection temperature of the rice cooking pot 12 reaches a predetermined boiling temperature, the middle-papping process is completed. For example, the boiling temperature based on the detection temperature TL of the lid sensor 36B is 60 to 70 ° C. when the rice cooking capacity is large (full amount), and 50 to 60 ° C. when the rice cooking capacity is not full. The boiling temperature based on the detection temperature TP of the pan sensor 36A is 90 ° C.

In the boiling maintenance step, the rice cooking pot 12 is heated (temperature controlled) so as to maintain the boiling temperature (for example, the detection temperature TP is 90 ° C.), and the water inside is eliminated (first step). In this first step, the coils 21A to 21C are sequentially duty-controlled with an output of 85% of the rated power, and on / off control is performed based on the detection temperature TP of the pan sensor 36A. When the detection temperature TP of the pan sensor 36A reaches a predetermined dry-up temperature (for example, 110 ° C.), the output is suppressed and the rice cooking pan 12 is heated over low heat (second step). In this second step, the coils 21A to 21C are sequentially duty-controlled with an output of 40% of the rated power, and on / off control is performed based on the detection temperature TL of the lid sensor 36B. After the dry-up is detected in the first step, the boiling maintenance step ends when the time (for example, 5 minutes) specified in the second step elapses. The boiling temperature used to determine the transition from the middle-papping step to the boiling maintenance step and the boiling temperature used as the temperature control reference in the boiling maintenance step may be the same or slightly different.

In the cooking process, the cooked rice is cooked with a higher output than the second step of the boiling maintenance process. In this cooking step, the coils 21A to 21C are sequentially duty-controlled with an output of 75% of the rated power, and on / off control is performed based on the detection temperature TL of the lid sensor 36B. When the detection temperature TP of the pan sensor 36A reaches the dry-up temperature, the cooking process ends.

In the murashi process, the temperature of the rice cooking pot 12 is adjusted at a low output, and the cooked rice is steamed. In this unevenness step, the coils 21A to 21C are sequentially duty-controlled with an output of 10% of the rated power, and on / off control is performed based on the detection temperature TL of the lid sensor 36B. When the specified time elapses, the unevenness process ends.

As described above, the control unit 45 executes the rice cooking process while switching the energization states of the coils 21A to 21C in a predetermined order. Which of the detection temperature TP of the pan sensor 36A and the detection temperature TL of the lid sensor 36B is used for determination can be changed as necessary.

(Outline of coil switching cycle)
In the rice cooking process described above, the steps for adjusting the temperature of the rice cooking pot 12 are a preheating step, a boiling maintenance step, a cooking step, and an unevenness step. In these steps, it is not necessary to raise the temperature of the rice cooking pot 12 immediately, but it is preferable to prevent the temperature of even a part of the rice cooking pot 12 from dropping. On the other hand, the step of raising the temperature of the rice cooking pot 12 immediately is the middle-papping step. In this middle-papping step, a large amount of water remains in the rice cooking pot 12, and it is preferable to heat the whole with as much heat as possible and with high efficiency.

On the other hand, switching of the energized state by the switching unit 48 is accompanied by an unavoidable heating stop time (including a rise time) in terms of control. If the energization time t (that is, the switching cycle S) of the individual coils 21A to 21C is made excessively short, the heating stop time increases, so that the amount of heating of the rice cooking pot 12 within the specified time decreases. Even if the energization of the coils before and after switching is duplicated, it is necessary to halve the power input to each coil (power is input stepwise), so it is undeniable that the amount of heating is reduced. On the other hand, if the energization time t for the individual coils 21A to 21C is lengthened, the heating stop time is reduced, so that the heating amount of the rice cooking pot 12 within a predetermined time is increased. However, of the three coils 21A to 21C, the region of the rice cooking pot 12 corresponding to the two that are cut off is not heated. Therefore, if the energizing time t for one coil is excessively long, the entire rice cooking pot 12 is used. Heating efficiency may decrease.

Further, in the rice cooking pot 12, when the temperature rises to a predetermined temperature (for example, 70 ° C.) by heating, bubbles are generated from the heating region (curved portion) of the rice cooking pot 12 corresponding to one energized rice cooker, and the bubbles generate a diameter. Convection occurs toward opposite positions in the direction. This convection continues after the individual coils 21A to 21C are raised by energization until the energization is cut off. If the energization time t for the individual coils 21A to 21C is made excessively short, the movement (stirring) of the rice and rice located in the heating region due to convection becomes insufficient. On the other hand, if the energization time t of the individual coils 21A to 21C is made excessively long, the amount of rice and rice located in the heating region becomes too small due to the movement due to convection, so that wasted time that does not contribute to stirring occurs.

That is, it is not preferable that the energization time t (switching cycle S) for the coils 21A to 21C is too long or too short. Therefore, the present inventors have found the optimum energization time t according to the purpose in the multi-coil type induction heating.

Specifically, when the entire rice cooking pot 12 is uniformly heated (temperature controlled), the coils 21A to 21C are controlled by a short cycle Sa in which the energization state is switched every relatively short energization time ta. The energizing time ta is set in the range of 0.3 seconds or more and 3 seconds or less. When the energizing time ta is less than 0.3 seconds, the rice cooking pot 12 cannot be heated because the rising time occupies most of the time. When the energization time ta is made longer than 3 seconds, the temperature of the corresponding heating region of the rice cooker 12 drops when the coil is energized again after making a round, even if it is the on time in the temperature control (on / off control). Is starting to do. Therefore, when the temperature of the rice cooking pot 12 is adjusted, it is preferable to set the energization time ta (switching cycle Sa) to the individual coils 21A to 21C in the above range.

The energizing times ta1, ta2, ta3, and ta4 are set in the preheating step, the boiling maintenance step, the cooking step, and the unevenness step of adjusting the temperature of the rice cooking pot 12, respectively. These energization times ta1 to ta4 are set to times within the range of the energization time ta, respectively, and are all set to the same 0.5 seconds in the present embodiment. However, the energizing times ta1 to ta4 may be different from each other.

When the temperature of the rice cooking pot 12 is raised quickly, the coils 21A to 21C are controlled in a long cycle in which the energization state is switched every longer energization time than in the case of temperature control. As shown in FIG. 4, the middle-papping step corresponding to this embodiment has a first step continuous with the preheating step and a second step continuous with the boiling maintenance step. In the first stage, the energized state of the coils 21A to 21C is switched in the first cycle Sb, and in the second stage, the energized state of the coils 21A to 21C is switched in the second cycle Sc (two stages). The first cycle Sb and the second cycle Sc are set according to the necessity of promoting convection.

Since the first step is continuous with the preheating step and the temperature inside the rice cooking pot 12 is lower than the temperature at which bubbles connected to convection are generated (for example, 70 ° C.), it is not necessary to consider the promotion of convection. Since the second step is continuous with the boiling maintenance step, the temperature inside the rice cooking pot 12 is higher than the temperature at which bubbles are generated, and convection is generated, it is preferable to consider the promotion of convection. Therefore, the first cycle Sb (energization time tb) of the first stage that emphasizes heating efficiency is more important than the second cycle Sc (energization time tc) of the second stage for the purpose of achieving both temperature rise and stirring in the rice cooking pot 12. ) Is set long.

In the first cycle Sb, the energization state of the coils 21A to 21C is switched every energization time tb longer than the energization time ta. The energizing time tb is set in the range of 5 seconds or more and 15 seconds or less. If it is less than 5 seconds, the heating stop time becomes long, so that the amount of heating of the rice cooking pot 12 per unit time becomes insufficient. If it is longer than 15 seconds, the local heating becomes excessive and the temperature of other parts begins to decrease. Therefore, when the heating in the rice cooking pot 12 is emphasized, the energization time tb (switching cycle Sb) for the individual coils 21A to 21C is preferably set in the above range, and is set to 10 seconds in the present embodiment. ..

In the second cycle Sc, the energization state of the coils 21A to 21C is switched for each energization time ct that is longer than the energization time ta and shorter than the energization time tb. The energizing time tc is set to a time shorter than the energizing time tb in the range of 2.5 seconds or more and 7.5 seconds or less. If it is set to less than 2.5 seconds, the generation of air bubbles connected to convection becomes insufficient, and an effective stirring action cannot be obtained. If it is longer than 7.5 seconds, a wasted time that does not contribute to stirring occurs, so that an efficient stirring action cannot be obtained. Therefore, in order to achieve both temperature rise and stirring in the rice cooking pot 12, it is preferable to set the energization time ct (switching cycle Sc) to the individual coils 21A to 21C in the above range, and in this embodiment, 5 seconds (energization). It is set to half the time tb).

Subsequently referring to FIG. 4, the timing of transition from the first stage (first cycle Sb) to the second stage (second cycle Sc) is set to the temperature Ta at which the pregelatinization of rice and rice begins. This transition temperature Ta (eg 60 ° C.) is higher than the preheating temperature Tb (eg 40 ° C.) and lower than the boiling temperature Tc (eg 90 ° C.). Pregelatinization means that the starch contained in cooked rice becomes paste-like, and this starch produces reducing sugars that contribute to the taste (sweetness and luster) of cooked rice. The amount of this reducing sugar produced increases when it reaches an appropriate temperature.

In the middle-papping process, since the transition temperature Ta from the first stage to the second stage is set to the temperature at which pregelatinization starts, optimum control for improving the taste can be realized. Specifically, in the first stage after the completion of the preheating step, as much reducing sugar as possible can be produced by raising the temperature in the rice cooking pot 12 to the transition temperature Ta in the shortest possible time. Further, in the second stage after reaching the transition temperature Ta, the taste of cooked rice can be improved without bias by efficiently stirring (convection) without retention.

Next, the control of the middle-papping process will be described with reference to FIG.

When shifting from the preheating step to the middle-papping step, the control unit 45 sets the output of the inverter circuit 49 to 100% in step S2-1. Subsequently, in step S2-2, it is determined whether or not the detection temperature TP of the pan sensor 36A is smaller than the transition temperature Ta. When the detection temperature TP is smaller than the transition temperature Ta, the energization time (timer count time) of the individual coils 21A to 21C is set to tb (first cycle Sb) in step S2-3. When the detection temperature TP is equal to or higher than the transition temperature Ta, the energization time of the individual coils 21A to 21C is set to tk (first cycle Sc) in step S2-4.

Next, in step S2-5, the switching timer for measuring the energization time is reset and started. Subsequently, in step S2-6, the switching timer waits until the counting up, and when the counting up occurs, the energization state of the coils 21A to 21C is switched in step S2-7. Then, in step S2-8, it is determined whether or not the detection temperature TP of the pan sensor 36A is equal to or higher than the boiling temperature (the temperature at which the boiling maintenance step is started) Tc. Then, when the detection temperature TP is lower than the boiling temperature Tc, steps S2-2 to S2-7 are repeated until the boiling temperature Tc or higher is reached. When the detection temperature TP becomes equal to or higher than the boiling temperature Tc, the middle-papping process is terminated (returned) and the process proceeds to the boiling maintenance process.

The rice cooker 10 of the present invention configured as described above has the following features.

Since the energization state is switched so that one of the plurality of coils 21A to 21C is energized by the switching unit 48, the rice cooker is charged per unit area as compared with the case where the entire rice cooking pot is heated by one coil. The possible power (that is, the amount of heating) can be increased. Therefore, the local portion of the rice cooking pot 12 can be concentrated and heated with a large amount of heat.

In the temperature raising step, the cycle for switching the energization state of the coils 21A to 21C is different between the first step continuous with the preheating step and the second step continuous with the boiling maintenance step, and the first cycle of the first step. Sb is longer than the second period Sc of the second stage. In the first stage, which is close to the preheating temperature Tb, the heating stop time due to the switching of the energized state is shorter than in the second stage, so that the inside of the rice cooking pot 12 can be heated faster than in the second stage. Therefore, the temperature inside the cooked rice pot 12 can be quickly raised to a temperature at which reducing sugars that contribute to the taste (sweetness and luster) of cooked rice are produced. In the second stage, which is close to the boiling temperature Tc, the energized state is switched earlier than in the first stage, so that convection due to bubbles generated by local heating can be promoted. Therefore, since the cooked rice can be agitated efficiently, it is possible to cook cooked rice without uneven heating. As a result, the taste of cooked cooked rice can be improved and ideal cooked rice can be realized.

The cycle for switching the energized state in the temperature raising step is two steps, the first cycle Sb and the second cycle Sc. Therefore, a large amount of heat can be reliably input in the early stage of the temperature raising step in which rapid temperature rise is desirable, and convection can be promoted in the latter stage of the temperature rising step in which efficient stirring is desirable. The temperature at which the first stage shifts to the second stage corresponds to the temperature at which the pregelatinization of rice and rice begins. Therefore, the temperature inside the cooked rice pot 12 can be raised quickly to the temperature at which reducing sugars are produced, and then the inside of the cooked rice pot 12 that has started pregelatinization can be efficiently stirred, so that the taste of cooked cooked rice is improved, which is ideal. Rice cooking can be realized.

The first energization time tb of the first cycle Sb is set in the range of 5 seconds or more and 15 seconds or less, and the second energization time tc of the second cycle Sc is set in the range of 2.5 seconds or more and 7.5 seconds or less. There is. Therefore, it is possible to perform optimum control according to the purpose, such as emphasizing heating or achieving both heating and stirring.

(Experimental example)
In order to confirm the effect of the configuration of the present invention, the inventors of the present application compared the value of the reducing sugar of cooked rice cooked with the rice cooker 10 and the conventional rice cooker shown in the present embodiment and the taste. ..

Regarding the product of the present invention, in the middle-papping process, the energization state of the coils 21A to 21C is switched every 10 seconds until the temperature of the rice cooking pot 12 reaches 60 ° C., and after the temperature of the rice cooking pot 12 reaches 60 ° C. The energized state of the coils 21A to 21C was switched every 5 seconds. As the first comparative product, a rice cooker using three coils was used as in the above embodiment, and the energized state of the coils 21A to 21C was switched every 10 seconds in the entire middle-papping process. For the second comparative product, a rice cooker that heats the rice cooker with one coil was used, and the rice cooker was continuously heated at an output of 100% in the middle-papping process. The control of other preheating step, boiling maintenance step, cooking step, and unevenness step is the same as that of the product of the present invention and the first comparative product.

The reducing sugar of cooked rice cooked by these rice cookers was measured by a predetermined inspection institution. As a result, the reducing sugar of cooked rice cooked by the product of the present invention is 4% higher than the reducing sugar of cooked rice cooked by the first comparative product, and 10% higher than the reducing sugar of cooked rice cooked by the second comparative product. it was high. That is, according to the product of the present invention, it can be said that the reducing sugar that contributes to the taste can be increased as compared with the first comparative product in which the heating mode is not changed in the middle-papping step and the second comparative product using one coil.

In addition, about the cooked rice cooked by the product of the present invention and the cooked rice cooked by the first comparative product, 10 persons skilled in the art who were enthusiastically experimenting with excellent taste sensation were allowed to evaluate the taste sensation. The evaluation items are aroma, appearance, softness, stickiness, and sweetness. As a result, the cooked rice according to the present invention was highly evaluated in all items as compared with the cooked rice according to the conventional first comparative product. In addition, regarding the overall, none of the 10 people evaluated it as worse than the first comparative product, 7 people evaluated it as the same, and 3 people evaluated it as good. That is, according to the product of the present invention, it can be said that the taste can be improved as compared with the first comparative product.

The rice cooker 10 of the present invention is not limited to the configuration of the above embodiment, and various modifications can be made.

For example, as shown in FIG. 7, in the middle-papping process, the cycle for switching the energization state of the coils 21A to 21C is between the first cycle Sb in the early stage of transition and the second cycle Sc in the latter stage of transition. There may be three stages having a third period Sd in the middle of the transition. The energization time is the longest in the first cycle Sb, and shortens in the order of the third cycle Sd and the second cycle Sc. Further, as shown in FIG. 8, in the middle-papping process, the cycle for switching the energization state of the coils 21A to 21C may be stepless so that the energization time is gradually shortened from the first cycle Sb to the second cycle Sc. Good. Even in these ways, the same actions and effects as those of the above-described embodiment can be obtained.

The timing for switching between the two or more steps (cycles) constituting the middle-papper process is not limited to the temperature corresponding to the temperature at which the pregelatinization of rice and rice begins, and can be changed as necessary. Moreover, the energization time tb of the first cycle Sb and the energization time tc of the second cycle Sc can also be changed as needed.

The number of coils may be four (21A to 21D) as shown in FIG. 9, and can be changed as needed. Further, the configuration is not limited to the configuration in which one of the plurality of coils is energized and the rest is cut off, and the mode of the energized coil can be changed as needed. That is, two of the four coils 21A to 21D shown in FIG. 9 may be controlled as a set. For example, the opposing coils 21A and 21C are used as a set of first coils, and the other opposing coils 21B and 21D are used as a set of second coils, and the first coils 21A and 21C and the second coils 21B and 21D are used. The energization may be switched in order. Further, the adjacent coils 21A and 21B are used as a set of the first coil, and the other adjacent coils 21C and 21D are used as a set of the second coil, and the first coil 21A and 21B and the second coil 21C and 21D are used. The energization may be switched in order. Of course, depending on the total number of the plurality of coils, the number of coils to be one set may be three or more, or the number of sets of two or more coils may be three or more. Further, the configuration is not limited to the configuration in which the opposing or adjacent coils are made into one set, and the positional relationship of the coils to be made into one set can be changed as necessary depending on the total number of coils.

Only two coils may be arranged in the circumferential direction about the axis of the rice cooking pot 12, or four or more coils may be arranged. The rice cooker 10 may be a pressure rice cooker having a movable valve body in the middle of the exhaust passage 30 so that the pressure inside the rice cooker 12 can be increased to a pressure higher than the atmospheric pressure.

10 ... Rice cooker 12 ... Rice cooker 13 ... Bottom 14 ... Outer part 15 ... Curved part 17 ... Rice cooker body 18 ... Storage part 19 ... Inner body 20 ... Protective frame 21A-21D ... Coil 22 ... Ferrite core 23 ... Holder 24 ... Hinged connection part 26 ... Lid body 27 ... Heat dissipation plate 28 ... Inner lid 29 ... Lid heater 30 ... Exhaust passage 31 ... Vent 32 ... Steam port set 33 ... Exhaust port 34 ... Void 36A, 36B ... Temperature sensor (detection part)
38 ... Operation panel 39 ... Switch 40 ... Liquid crystal panel 42 ... Holder 43 ... Control board 45 ... Control unit 46 ... Storage unit 47 ... Timekeeping unit 48 ... Switching unit 49 ... Inverter circuit

Claims (5)

With a bottomed tubular rice cooker
A plurality of coils arranged side by side in the circumferential direction around the axis of the rice cooking pot to induce and heat the rice cooking pot,
A detector that detects the temperature inside the rice cooker and
At least, the first state in which one or more of the first coils of the plurality of coils are energized and the rest is cut off, and one or more second coils of the plurality of coils other than the first coil. A switching unit for switching the energized state of the plurality of coils so as to include a second state in which the coil is energized and the rest is cut off.
A preheating step of controlling the switching unit and the plurality of coils to heat the rice cooker so that the temperature detected by the detection unit maintains a predetermined preheating temperature, and the detection temperature is higher than the preheating temperature. A rice cooking process including a temperature raising step of heating the rice cooker so as to raise the temperature to a predetermined boiling temperature and a boiling maintenance step of heating the rice cooker so that the detected temperature maintains the boiling temperature is executed. Equipped with a control unit
The temperature raising step has a first step continuous with the preheating step and a second step continuous with the boiling maintenance step.
A rice cooker in which the first cycle of the first stage, in which the energized state is switched by the switching unit, is longer than the second cycle of the second stage. The rice cooker according to claim 1, wherein the temperature raising step comprises only the first step and the second step. The control unit defines a transition temperature that corresponds to the temperature at which the preheating of rice and rice begins, is higher than the preheating temperature, and is lower than the boiling temperature.
The rice cooker according to claim 2, wherein in the temperature raising step, when the temperature detected by the detection unit rises to the transition temperature, the control unit shifts from the first step to the second step. The rice cooker according to any one of claims 1 to 3, wherein the first energizing time of the first cycle is set in the range of 5 seconds or more and 15 seconds or less. The rice cooker according to claim 4, wherein the second energizing time of the second cycle is set to a time shorter than the first energizing time in the range of 2.5 seconds or more and 7.5 seconds or less.

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