JP4146809B2 - rice cooker - Google Patents

Description

  The present invention relates to a rice cooker that adds rice and rice with appropriate amounts of water and heat.

  In a conventional rice cooker, the washed rice and an appropriate amount of water are put into an inner pot that is detachably accommodated in the main body, and an electromagnetic induction coil is installed on the opposite surface of the inner pot, and an electromagnetic induction coil is used. The inner pot is heated by high-frequency electromagnetic induction, convection of water in the inner pot is promoted, and rice is cooked (see, for example, Patent Document 1). The temperature in the inner hook is detected by a temperature sensor that contacts the bottom surface of the inner hook (see, for example, Patent Document 2).

JP-A-10-113278 (page 3, FIG. 2) Japanese Patent Laid-Open No. 9-10098 (page 4, FIG. 1)

In the conventional rice cooker, in the inner pot, the opposing part of the electromagnetic induction coil generates heat at a high temperature, but the part other than the opposing part tends to be low temperature, and temperature distribution occurs in the rice and water in the inner pot. There was a problem. Generation | occurrence | production of this temperature distribution means that the quality of rice, such as the hardness of rice, stickiness, sweetness, and fragrance, arises, and it is necessary to reduce this quality variation. Therefore, in order to reduce the occurrence of this temperature distribution, a method of increasing the amount of heat transfer in the hook material by increasing the thickness of the inner hook material, a method of promoting convection in the inner hook, A method of moving (replacing) the heat generating part has been proposed. However, each of the above methods has not led to the direct elimination of the temperature distribution.
In particular, since the maximum amount of heating is performed by an electromagnetic induction coil when the temperature rises in the boiling process of rice cooking, the temperature distribution is most likely to occur and a boiling state rich in free water (water not absorbed by the rice) is maintained. Since the hardness of the rice is almost determined by the length of the cooking time, the occurrence of the temperature distribution in the boiling process leads to the variation in the hardness of the rice as it is.

Next, the temperature distribution in the inner pot will be described with reference to the drawings.
FIG. 10 is a configuration diagram of a conventional rice cooker, FIG. 11 is a diagram showing the temperature distribution of each part in the inner pot at the start of boiling in the conventional rice cooker, and FIG. 12 is an inner pot in the entire rice cooking process in the conventional rice cooker. The figure which shows the temperature change of each measurement point of Table 1, Table 1 is a figure which shows the hardness of the rice in each measurement point in the inner pot in the conventional rice cooker.

  In the figure, a temperature sensor 2 is provided on the bottom of the inner pot 1 of the rice cooker, and an electromagnetic induction coil 3 is disposed so as to face the inner pot 1 while avoiding the temperature sensor 2. The electromagnetic induction coil 3a that is opposed to the bottom surface of the inner shell 1 and the electromagnetic induction coil 3b that is opposed to the lower side surface of the inner pot 1 are configured.

  According to the measurement results of conventional rice cooking shown in FIGS. 11 and 12 and Table 1, the rice above the heating surface by the electromagnetic induction coils 3a and 3b is sufficiently heated and softened at the boiling temperature, but the rice above the temperature sensor 2 is low temperature. The temperature at the point A in the figure is about 14 minutes later than the start of boiling near the heating surface, so that the gelatinization of the rice is insufficient even at the end of cooking, and the center of the rice is hard It becomes (rice with a core). Disposing the electromagnetic induction coil 3 while avoiding the temperature sensor 2 in this way has a problem that a temperature distribution is generated in the inner pot and the quality of the rice is lowered.

  Furthermore, the surface of the rice itself is relatively hard, and even if water is absorbed in the water in the inner pot 1, there is a gap between the rice and the rice. For this reason, in a preheating process, when temperature distribution arises in the inner pot, water moves in the gap between the rice and gentle convection heat transfer occurs. On the other hand, when the rice starch is gelatinized (α-ized) into a rice state, the surface of the rice becomes sticky and soft due to the glue of the rice starch, the rice and the rice stick together and there is almost no gap, and convection heat transfer Is disturbed. Since the gelatinization temperature of rice starch is about 60 ° C, the preheating process is completed and the rice grains start to stick when they enter the boiling process, and the rice becomes a lump in the inner pot. At the time of temperature rise at, almost no convection occurs. Therefore, the method of devising the position of the electromagnetic induction coil to promote convective heat transfer is also less effective in the most expected boiling process, and the electromagnetic induction coil facing portion of the inner pot 1 generates heat at a high temperature, and other than the facing portion. There was a problem that the part was likely to become low temperature.

  The present invention has been made to solve the above-described problems. In the inner pot, the opposing portion of the temperature sensor unit where the electromagnetic induction coil cannot be arranged can be heated, and the rice and water in the inner pot can be removed. An object of the present invention is to provide a rice cooker that can be heated uniformly and hardly causes temperature distribution in the inner pot.

  The rice cooker according to the present invention includes an inner pot that is detachably accommodated in the main body, an induction heating coil that heats the inner pot, and a temperature sensor that detects the temperature of the inner pot, and the temperature sensor includes a heating element. And heating the heating element for a predetermined time when the cooked rice in the inner pot is boiled.

  In the present invention, a heating element is provided in the temperature sensor, and the heating element is heated for a predetermined time when the food to be cooked in the inner pot is boiled, so that heat is generated at the initial stage of boiling where the most heat supply is required and at the temperature rising stage. Because it has a function, it is possible to increase the temperature near the top of the temperature sensor, which was the lowest temperature in the conventional method, uniformly heat the rice and water in the inner pot, and it is difficult for temperature distribution to occur in the inner pot, You can cook delicious rice.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a rice cooker in Embodiment 1 for carrying out the present invention, FIG. 2 is a configuration diagram of a temperature sensor unit in this rice cooker, and FIG. 3 is a temperature in an inner pot in each step of this rice cooker. FIG. 4 is a timing chart of the electromagnetic induction coil, the temperature sensor, and the lid temperature sensor in the rice cooking process of this rice cooker, and a diagram showing the temperature change. FIG. 5 is the inside of the inner pot at the start of boiling of this rice cooker. The figure which shows the temperature distribution of each part, FIG. 6 is a figure which shows the temperature change of each measuring point in the inner pot in the whole rice cooking process of this rice cooker, Table 2 is the rice in each measuring point in the inner pot in this rice cooker. It is a figure which shows the hardness of.

  In the figure, the rice cooker main body 4 is provided with a lid 5 that opens and closes the upper surface opening, and an inner pot 6 that is detachably accommodated in the main body 4, and the washed rice 7 and an appropriate amount of water 8 are put into the inner pot 6. Put in and cook rice. The temperature sensor 9 having a heat generating function detects the temperature by contacting the bottom of the inner hook 6. The control circuit unit 10 drives the electromagnetic induction coil 11 to control the heat generation amount. The lid temperature sensor 12 is provided on the lid 5 and detects the temperature of the lower surface of the lid 5.

  The temperature sensor 9 includes an outer frame 13, a thermistor 14 that is in contact with the outer frame 13 on the upper surface and detects temperature, a heating element 15 that is inscribed in the outer frame 13, a common lead wire 16 for the thermistor 14 and the heating element 15, and a thermistor lead. A wire 17, a lead wire 18 for the heating element 15, and a coil spring 19 for reliably obtaining contact between the temperature sensor 9 and the inner hook 6 are provided.

Next, the operation will be described.
First, rice 7 and water 8 are put in the inner pot 6, set in the rice cooker body 4, and a rice cooking switch (not shown) on the operation panel is inserted. The rice cooker enters the preheating process, and the control circuit unit 10 heats the inner pot 6 while adjusting the energization amount of the electromagnetic induction coil 11 so that the temperature value detected by the temperature sensor 9 does not exceed 60 ° C. The rice 7 and water 8 are heated (a in FIG. 3).
In this preheating step, an output between the common lead wire 16 and the thermistor lead wire 17 is sent to the control circuit unit 10. Furthermore, the amount of rice cooking is roughly detected from the relationship between the current amount of the electromagnetic induction coil 11 and the energization time and the output of the temperature sensor 9 (detected temperature value).

  Next, when the control circuit unit 10 measures that about 15 minutes have elapsed from the start of rice cooking by a timer (not shown), the control circuit unit 10 automatically enters a boiling process (b in FIG. 3). Therefore, the temperature value detected by the temperature sensor 9 is ignored without being controlled, and a predetermined voltage is applied between the common lead wire 16 and the heating element lead wire 18 to heat the heating element 15 and at the same time, the electromagnetic induction coil The energization amount of 11 is maximized. Thereafter, the heat generation of the heating element 15 and the state of maximum energization of the electromagnetic induction coil 11 are continued, and when the temperature in the inner pot 6 reaches 100 ° C., the water boils, and the generated water vapor causes the lid portion temperature sensor 12 to The detected temperature is slightly delayed to 100 ° C., and the boiling state is detected. In addition, although the temperature distribution in the inner pot at the time of a boiling start is shown in FIG. 5, the phenomenon that the temperature of the temperature sensor 9 upper part becomes low is not seen.

  Further, at the time of boiling, the rice is gelatinized as described above, and the surface is covered with a paste-like substance, forming a sticky lump in the inner pot 6. Therefore, the weak flow of water such as convection caused by the temperature difference is hindered, but gas such as water vapor generated by boiling is greatly different from the water in the mass of rice, and can pass through the steam. Make a spout. This steam spout is a crab hole that is generally said, and the more crab holes, the better the rice cooking method that is uniformly heated. This is because the crab hole once formed is not only easy for boiling steam to pass through, but it can also pass weak water flow such as convection even with low heat heating in the late stage of the boiling process, so the state of uniform cooking rice with a small temperature distribution can be achieved. Can be made. In this embodiment, since the inner hook 6 is heated including the temperature sensor 9 which has not been heated conventionally, uniform heating is possible, and a large number of the crab holes are formed equally.

When detecting the boiling state with the lid temperature sensor 12, the control circuit unit 10 stops the heat generation of the heating element 15 and appropriately controls the energization amount of the electromagnetic induction coil 11. After this state is continued for about 5 minutes, the temperature value detected by the temperature sensor 9 is set as a control target. In about 5 minutes, almost the amount of heat generated by the heating element 15 is absorbed by the inner hook 3, and the temperature of the temperature sensor 9 is equal to the temperature of the inner hook 6.
About 15 minutes have passed since the boiling process, and when the free water is almost evaporated, the temperature of the inner pot 6 exceeds 100 ° C. Therefore, the excess of 100 ° C is detected by the temperature sensor 9, and the steaming process (C in Fig. 3) is performed. enter.

  Here, although the heat generation of the temperature sensor 9 is a short time of about 5 minutes, it is possible to make it difficult to cause temperature nonuniformity at the time of boiling when the temperature distribution becomes the largest as described above. Furthermore, the crab hole once formed at the initial boiling stage where the stickiness between rice and rice is relatively low is maintained even after the heat generation of the temperature sensor 9 is stopped, and the temperature uniformity effect can be maintained and the temperature distribution can be eliminated. it can.

  In the steaming process, the control circuit unit 10 controls the energization amount of the electromagnetic induction coil 11 to be further reduced, and maintains the temperature in the inner pot at about 100 ° C. by the output of the temperature sensor 9. After this state is continued for about 15 minutes, the steaming process is automatically terminated, and at the same time, the user is notified by the operation panel display and a notification sound (not shown) that the rice cooking has been completed, and the whole rice cooking process is completed.

  The temperature change of each part in the inner pot 6 in the whole rice cooking process is shown in FIG. 6, and the rice at the top of the temperature sensor 9 is also heated in the same manner as the other parts. Conventionally, about 14 minutes delay from the start of boiling to the boiling of point A However, it can be seen that it has been shortened by 7 minutes. Moreover, the measurement result of the rice cooking of Table 2 shows that the hardness of the rice of A point (middle center part) becomes the hardness similar to another part, and is cooking softly.

As described above, in the first embodiment, since it is configured to heat the vicinity of the temperature sensor portion in the inner pot where the temperature is likely to be lowered at the initial stage of boiling and the temperature rising stage where the most heat supply is required. As described above, the temperature sensor portion is not lowered in temperature so that only this portion becomes hard rice, the inside of the inner pot can be heated uniformly, and the rice can be cooked deliciously. Furthermore, since it has the function required as a temperature sensor conventionally, the temperature management indispensable for rice cooking can be performed as usual.
In addition, in this Embodiment 1, although the example which performs the amount detection of rice cooking in the temperature rising stage from room temperature to 60 degreeC was shown, you may carry out in the stage which heats up from 60 degreeC to 100 degreeC.

Embodiment 2. FIG.
FIG. 7 is a configuration diagram of a temperature sensor portion of the rice cooker in the second embodiment for carrying out the present invention.
In the figure, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals. The temperature sensor 20 includes an outer frame 13, a thermistor 14 that is in contact with the outer frame 13 on the upper surface and detects temperature, a common lead wire 16 for the thermistor 14 and a tubular heating element 21 (described later), a thermistor lead wire 17, a tubular heating element. The lead wire 18 for 21 and the coil spring 19 for reliably obtaining contact between the temperature sensor 20 and the inner hook 6 are provided, and a dedicated tubular heating element 21 is fitted and fixed to the outer periphery of the temperature sensor 20. The inner diameter of the tubular heating element 21 is equal to the outer diameter of the temperature sensor 20.
In addition, the structure of the whole rice cooker is the same as that of Embodiment 1 except the temperature sensor 20. FIG.

In the rice cooking operation, operations other than the heating of the inner pot by the tubular heating element 21 are the same as those in the first embodiment, and thus the description thereof is omitted.
Both the temperature sensor 20 and the tubular heating element 21 come into contact with the bottom surface of the inner pot 6, the tubular heating element 21 generates heat in about 5 minutes at the beginning of the boiling process, heats the inner pot, and the temperature in the inner pot during boiling rises. Uniformity is less likely to occur and temperature distribution is eliminated.

In addition to the above-described configuration, it may be non-tubular as long as it can maintain a sufficient contact state with the temperature sensor. The tubular heating element 21 may be fitted and fixed to a conventional temperature sensor.
Further, in addition to the configuration in which the upper surface of the tubular heating element 21 is in contact with the bottom surface of the inner pot and improves the heat conduction with the inner pot, the tubular heating element 21 is provided at the lower outer periphery of the temperature sensor 20. The same effect can be obtained even when only the temperature sensor 20 is in contact with the inner hook without contacting the inner hook.

  As described above, in the second embodiment, a tubular heating element is fitted to the outside of the temperature sensor, and it is configured to heat the vicinity of the temperature sensor portion in the inner pot that is likely to be lowered in temperature. Temperature uniform rice cooking can be realized.

Embodiment 3 FIG.
FIG. 8 is a configuration diagram of the temperature sensor portion of the rice cooker in Embodiment 3 for carrying out the present invention.
In the figure, the same reference numerals are assigned to the same or corresponding parts as those in the first and second embodiments. The temperature sensor 22 is in contact with the outer frame 13, the outer frame 13 on the upper surface, and detects the temperature, the common lead wire 16 of the thermistor 14 and the plate-like heating element 23 (described later), the thermistor lead wire 17, the plate shape. The heating element 23 has a lead wire 18, a coil spring 19 for ensuring contact between the temperature sensor 22 and the inner hook 6, and a plate-like heating element 23 is provided above the temperature sensor 22. Is arranged between the temperature sensor and the inner hook. Further, the plate-like heating element 23 is in contact with the bottom surface of the inner hook 3 and uses a material having good thermal conductivity, such as copper, silver, aluminum or the like.
In addition, the structure of the whole rice cooker is the same as that of Embodiment 1 except the temperature sensor 22. FIG.

In the rice cooking operation, the operations other than the heating of the inner pot by the plate-like heating element 23 are the same as those in the first embodiment, and thus the description thereof is omitted.
The plate-like heating element 23 comes into contact with the bottom surface of the inner pot and generates heat for about 5 minutes at the beginning of the boiling process. The inner pot is heated to make it difficult to cause uneven temperature in the inner pot at the time of boiling. Is to eliminate.
In the above configuration, the diameter of the plate-like heating element 23 and the diameter of the upper surface of the temperature sensor 22 are the same. However, they may not be the same. Any material may be used as long as it can prevent temperature non-uniformity at the temperature and can detect the temperature by the thermistor 14.

  As described above, in the third embodiment, the plate-like heating element is disposed between the temperature sensor and the inner pot, and the heating is performed including the vicinity of the temperature sensor portion in the inner pot where the temperature is easily lowered. Easily temperature uniform cooking can be realized.

Embodiment 4 FIG.
FIG. 9 is a configuration diagram of a rice cooker according to Embodiment 4 for carrying out the present invention.
In the figure, the same or corresponding parts as those in the first to third embodiments are denoted by the same reference numerals and description thereof is omitted. The storage battery 24 stores electric power supplied to the heating element 15 of the temperature sensor 9. The lead wire 25 connects the control circuit unit 10, the temperature sensor 9, and the storage battery 24. The lead wire 25 has the function of the lead wires 16, 17, and 18 of the first to third embodiments.

Next, the operation will be described.
Rice 7 and water 8 are put in the inner pot 6 and accommodated in the rice cooker main body 4, a rice cooking switch (not shown) on the operation panel is inserted, and a preheating process is started. In the preheating process, since the power supplied to the electromagnetic induction coil 5 is relatively small, the power is supplied from the control circuit unit 10 and the storage battery 24 is charged. The amount of power to be charged is the power required to generate heat for about 5 minutes, that is, about 5 WHr, assuming that the amount of heat generated by the temperature sensor 9 is 50 W, for example. This electric power is adjusted according to the required calorific value. Other operations in the preheating step are the same as those in the first embodiment.

Next, the boiling process is started, and in the initial stage of the boiling process, power is most required in all the rice cooking processes, so the power to the heating element 15 of the temperature sensor 9 is supplied from the storage battery 24 via the lead wire 25, The heating element 15 generates heat.
Here, because there are legal restrictions on the maximum power for household electrical appliances such as rice cookers, power is used for temperature sensors as in the first to third embodiments at the beginning of the boiling process that requires the most heat generation. Then, it is necessary to reduce the amount of power supplied to the electromagnetic induction coil 11, but by this power storage function, the heating element 15 of the temperature sensor 9 is heated by another power source without reducing the amount of heat generated by the electromagnetic induction coil 11. The required amount can be secured.
Other operations in the boiling process and operations in the steaming process are the same as those in the first embodiment.

  In the present embodiment, the temperature sensor using the temperature sensor 9 according to the first embodiment has been described. However, the temperature sensor 20 according to the second embodiment or the temperature sensor 22 according to the third embodiment may be used. Soon, the same effect is achieved.

  As described above, in the fourth embodiment, since the electric power of the heating element of the temperature sensor unit is stored in advance before the boiling process, in the initial stage of boiling where the most heat supply is required and the temperature raising stage thereof, Without reducing the amount of power supplied to the electromagnetic induction coil, a necessary amount of heat generated by the electromagnetic induction coil can be secured, and ideal rice cooking with a small temperature distribution can be realized.

It is a block diagram of the rice cooker which shows Embodiment 1 of this invention. It is a block diagram of the temperature sensor part of the rice cooker which shows Embodiment 1 of this invention. It is a figure which shows the temperature change in the inner pot in each process of the rice cooker which shows Embodiment 1 of this invention. It is a figure which shows the timing chart and temperature change of each part in the rice cooking process of the rice cooker which shows Embodiment 1 of this invention. It is a figure which shows the temperature distribution of each part in an inner pot at the time of the boiling start of the rice cooker which shows Embodiment 1 of this invention. It is a figure which shows the temperature change of each measuring point in the inner pot in the rice cooking whole process of the rice cooker which shows Embodiment 1 of this invention. It is a block diagram of the temperature sensor part of the rice cooker which shows Embodiment 2 of this invention. It is a block diagram of the temperature sensor part of the rice cooker which shows Embodiment 3 of this invention. It is a block diagram of the rice cooker concerning Embodiment 4 of this invention. It is a block diagram of the conventional rice cooker. It is a figure which shows the temperature distribution of each part in an inner pot at the time of the boiling start in the conventional rice cooker. It is a figure which shows the temperature change of each measuring point in the inner pot in the whole rice cooking process in the conventional rice cooker.

Explanation of symbols

  4 Rice cooker body, 6 Inner pot, 7 Rice, 8 Water, 9 Temperature sensor, 10 Control circuit part, 11 Electromagnetic induction coil, 15 Heating element, 21 Tubular heating element, 23 Plate heating element, 24 Storage battery

Claims (5)

An inner pot that is detachably accommodated in the main body,
An induction heating coil for generating heat in the inner pot;
A temperature sensor for detecting the temperature of the inner pot;
A rice cooker, wherein a heating element is provided in the temperature sensor, and the heating element is heated for a predetermined time when the cooked rice in the inner pot is boiled.   The rice cooker according to claim 1, wherein the heating element is built in the temperature sensor.   The rice cooker according to claim 1, wherein the heating element is arranged around the temperature sensor.   The rice cooker according to claim 1, wherein the heating element is disposed on the inner pot facing portion of the temperature sensor. A power storage unit for storing electric power;
The rice cooker according to any one of claims 1 to 4 , wherein electric power is supplied from the power storage unit to cause the heating element to generate heat.

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