JPS635084B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a rice cooker with an improved heating method.

Conventional electric rice cookers have a heating plate heated by an electric heater at the bottom of the outer pot, and the inner pot containing rice is removably placed on the heating plate. This method transfers the heat from the rice to the bottom of the inner pot to cook rice. However, when rice is cooked in a rice cooker with such a conventional structure, the upper part becomes dry with less water and the lower part becomes sticky with a lot of water, resulting in so-called uneven cooking and the overall taste deteriorates. It was hot.

The present invention has been made in view of the above circumstances, and improves the heating method so that rice can be cooked evenly, and the taste of the cooked rice can be greatly improved, and in addition, To provide a rice cooker that can reliably detect when rice is cooked.

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.
This will be explained with reference to the figures. Reference numeral 1 denotes an outer case whose upper and lower surfaces are open, and an annular bottom frame 2 is press-fitted into the lower part of the outer case. Reference numeral 3 denotes a bottom plate having legs 4, 4, which is fixed to the bottom frame 2 with screws so as to close the opening 2a of the bottom frame 2. Reference numeral 5 denotes an annular decorative frame made of heat insulating material such as heat-resistant plastic that is fitted onto the upper end of the outer case 1. Reference numeral 6 denotes a substantially cylindrical inner case screwed to the decorative frame 5, which is connected to the outer case 1. A heat insulating material 7 is disposed between the inner case 6 and the inner case 6. Reference numeral 8 denotes a heating plate as a substantially annular heating body formed by casting an aluminum alloy, for example, and the outer periphery of this is fixed to the inner periphery of the lower part of the inner case 6 with screws, and the upper surface is fixed to the inner periphery of the lower part of the inner case 6. An inclined surface 9 is formed which is oriented downward toward the center. Reference numeral 10 denotes an annular sheathed heater, which is press-fitted to the vicinity of the inner periphery of the lower surface of the heating plate 8 by caulking and deforming a tongue piece 8 _a protruding from the lower surface of the heating plate 8. . The heating plate 8 has a thick inner circumference, and the thickness gradually decreases toward the outer circumference. Now, reference numeral 11 is a pot made of aluminum alloy, for example, which has a sloped part _11b that slopes inward at the lower part of the side part _11a , and an inner case 6.
When stored inside, the inclined portion _11b is placed in close contact with the inclined surface 9 of the heating plate 8. 1
Reference numeral 2 denotes a magnetic body as a heat-sensitive part made of a magnetic shunt material having a magnetic transformation point, such as an MS alloy, which is attached to the bottom surface _11c of the pot 11, and this is arranged near the inner circumference of the heating plate 8, for example. ing. A lever 13 is rotatably supported by the inner case 6 via a shaft pin 14. A permanent magnet 15 corresponding to the magnetic body 12 is provided at one end of the lever, and a through hole 1 of the outer case 1 is provided at the other end. _a
A knob 16 is attached that protrudes outward from the. 1
7 is a fixed contact piece 1 attached to the lower part of the inner case 6
7 _a and a movable contact piece 17 _b , this is a switch that controls energization/disconnection of the sheathed heater 10.
The movable contact piece _17b is formed, for example, by an elastic plate spring, and the fixed contact piece _17a is always fixed.
Moreover, this movable contact piece 17b has a resilient force in the direction of separating from the lever 13, and the movable contact piece _17b is rotated in the direction of the arrow A by the lever 13 via the contact body 18 made of an insulating material provided on the lever 13. It provides power. Therefore, when the lever 13 is rotated in the opposite direction of arrow A through the knob 16 with the pot 11 set on the heating plate 8, the permanent magnet 15 is attracted to the magnetic body 12 when the temperature of the pot 11 is low. and is held in an adsorbed state. In this state, the permanent magnet 15 is always urged away from the magnetic body 12, that is, in the direction of arrow _A , by its own gravity and the elastic force of the movable contact piece 17b. Although not shown, the pot 11 is provided with positioning means so that the magnetic body 12 is set in correspondence with the permanent magnet 15. Reference numeral 19 denotes an outer lid rotatably supported by the outer case 1, which integrally forms a carrying handle 20, and has a heat insulating material 21 disposed inside, which is covered with a cover 22. keeping. Reference numeral 23 denotes an inner lid that closes the upper surface of the pot 11, and this is supported so as to be movable up and down on a shaft pin 24 protruding from the cover 22. spring 25
is always biased downward. Therefore, when the outer lid 19 is closed, the inner lid 23 comes into close contact with the stepped portion 11 _d formed on the upper edge of the pot 11.

Next, the operation of this embodiment configured as above will be explained. Washed rice 26 and rice cooking water 27 are stored in a pot 11, the pot 11 is set on a heating plate 8, and an outer lid 19 and an inner lid 23 are closed.
Next, when the lever 13 is rotated in the opposite direction of arrow A using the knob 16 and the permanent magnet 15 is attracted to the magnetic body 12, the movable contact piece _17b is attached to the fixed contact piece _17a via the contact body 18. They are moved so that they make contact, the switch 17 is closed, and the sheathed heater 10 is energized. Then, the heating plate 8 is heated by the sheathed heater 10.
The pot 11 is heated through. Now, by heating the pot 11, the rice 26 in the pot 11 is cooked, but the present inventor has determined that the upper, middle, and lower portions of the rice 26 stored in the pot 11 ( The characteristic curve shown in Figure 2 shows the temperature (t°C) on the vertical axis and the elapsed cooking time T on the horizontal axis as the measurement results. was gotten. That is, in this embodiment, since the inclined portion _11b of the pot 11 is heated by the sheathed heater 10 via the heating plate 8, the local convection shown by the arrow a in FIG. 1 occurs at the beginning of rice cooking. This is done well, and the temperature of the upper part A of the pot 11 tends to rise before the middle part B and lower part C. In addition, as the rice cooking progresses, the water level in the pot 11 decreases, and the rice located at the top acts as a heat insulator, and when the water level drops from the upper end of the slope _11b , the slope 11 The amount of heat transferred from _b to the water 27 gradually decreases, and the amount of heat transferred from the heating plate 8 to the bottom portion 11 _c of the pot 11 gradually increases. That is,
At the end of rice cooking, the rice located at the top acts as a thermal insulator and the amount of heat transferred to the bottom part _11c of the pot 11 increases, and the temperature of the lower part C in FIG. 2 rises at the end of rice cooking, so the rice is relatively cooked. It only takes a short time,
As shown by the two-dot chain line C, the temperature rise is delayed and the rice cooking time does not take long. When the water 27 in the pot 11 is completely absorbed by the rice 26 and disappears, the pot 11 becomes a so-called dry cooking state, but the inner circumference of the heating plate 8 is thick and the sheathed heater 10 is not attached to the inner circumference. Since the heating plate 8 is located near the inner periphery of the heating plate 8, the temperature becomes highest, and the temperature of the magnetic body 12 located near the inner periphery of the heating plate 8 rises rapidly. Then, the relative magnetic permeability of the magnetic body 12 decreases significantly, and the attraction force acting between the magnetic body 12 and the permanent magnet 15 rapidly decreases. In this way, when the attraction force between the magnetic body 12 and the permanent magnet 15 becomes less than a predetermined value, the urging force applied to the permanent magnet 15 in the direction of arrow A exceeds the attraction force, Therefore, the lever 13 rotates in the direction of arrow A, the permanent magnet 15 separates from the magnetic body 12 and is displaced downward, and the movable contact piece _17b moves towards the fixed contact piece 1.
_7a , the switch 17 is opened, the sheathed heater 10 is cut off, and the rice cooking ends.

Now, the water absorption rate of rice 26 is most remarkable when the temperature is in the range of 60°C to 70°C, and
60 above before the middle part B and the lower part C.
When the temperature reaches the range of .degree. C. to 70.degree. C., the rice 26 located in the upper part A begins to absorb water. Then, as the cooking time progresses, the pot 11
As the water 27 inside is absorbed by the rice 26, the water level is lowered, and the rice 26 located in the upper part A is automatically prevented from absorbing more water than necessary.
The temperature of the intermediate portion B, which rises later, gradually reaches the range of 60° C. to 70° C., and the water absorption action of the rice 26 located in the intermediate portion B increases. Further, as time passes and the water absorption action of the rice 26 located in the middle part B progresses, the water level in the pot 11 further decreases as described above, and the rice 26 located in the middle part B is also prevented from absorbing water more than necessary. , the rice 26 located in the lower part C, where the temperature rises later than the middle part B, absorbs more water.

By the way, the conventional structure uses a heater to heat only the bottom of the pot, so the temperature at the bottom of the pot tends to rise before the temperature at the top, and as rice cooking progresses, the temperature at the bottom tends to rise. The temperature rise at the top of the pot, where water runs out quickly, is delayed, resulting in rice being cooked in a dry state with low water absorption.On the other hand, until the end of cooking, the temperature rises fastest at the bottom of the pot, where water is present, and the rice remains at a high temperature for a long time. However, in this example, pot 11 was used.
In the upper part A of the pot 11, water 27 quickly reaches the optimum temperature for absorption (60°C to 70°C), but also quickly runs out of water, and in the lower part C of the pot 11, water remains until near the end of cooking, but the optimum water absorption temperature is not reached. Therefore, no matter where the rice 26 is located in the pot 11, the time it takes to reach the optimum water absorption temperature is approximately constant.
By cooking the rice 26 to a uniform water absorption rate without any uneven cooking, the rice 26 can be cooked evenly and the taste can be greatly improved.

Now, in the method of heating the lower side of the pot 11 as in this embodiment, even when the rice 26 is cooked, the temperature at the center of the bottom of the pot 11 rises relatively slowly, unlike the conventional structure. If the heat-sensitive part for detection is provided at the center of the bottom of the pot, it will take a long time until the sheathed heater 10 is turned off after cooking is completed (as shown by D' in FIG. 2), and the side surface of the pot 11 will be _11a
However, in this _embodiment , the sheathed heater 10 is provided near the inner periphery of the heating plate 8, and the inner periphery of the heating plate 88 is made thick. Furthermore, since the inner peripheral part of the heating plate 8 and the magnetic body 12 as a heat-sensitive part are placed close to each other, heat is efficiently transferred from the heating plate 8 to the bottom part _11c of the pot 11 at the end of rice cooking. The cooking time can be shortened, and the temperature of the bottom part _11c near the magnetic body 12 rises in a relatively short time as shown by "D" in FIG. The time until the power is cut off can be shortened as much as possible, and rice 26 can be prevented from sticking to the side part _11a and the slope part _11b as much as possible. Note that FIG. 3 shows another embodiment of the present invention, and only the parts different from FIG. 1 will be described. That is, the heating plate 8 is formed to have a substantially uniform thickness, and the sheathed heater 10 has a substantially uniform thickness by caulking and deforming the tongues 8 _b and 8 _c slightly closer to the outer periphery than the center of the heating plate 8. It is pressed against the heating plate 8. 28 is the bottom part 1 of the pot 11
1 _c is a thick walled portion serving as a transmission means, and its outer periphery is brought into close contact with the inner periphery of the heating plate 8,
The magnetic body 12 is provided approximately at the center of this thick portion 28,
The permanent magnet 15 is made to correspond to the magnetic body 12. Therefore, the same effects as described above are obtained in this embodiment as well, and the rice cooking time can be shortened by good heat transfer from the heating plate 8 to the thick wall portion 28 especially at the end of rice cooking. The thick part 28 has a substantially uniform temperature as a whole when rice cooking is completed, and the time from the completion of rice cooking to the power cut-off of the sheathed heater 10 can be shortened as much as possible, and the rice 26 can be prevented from burning.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, but can be implemented with various modifications within the scope of the invention.

As explained above, the present invention enables rice to be cooked evenly and greatly improves the flavor of the cooked rice, and in addition, it is possible to reliably detect when the rice is cooked and prevent rice from burning as much as possible. We can provide equipment.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a longitudinal sectional view, FIG. 2 is a temperature characteristic diagram, and FIG. 3 is a schematic diagram showing another embodiment of the present invention. FIG. In the drawings, 1 is an outer case, 8 is a heating plate, 9 is an inclined surface, 10 is a sheathed heater, 11 is a pot, 12 is a magnetic material, 15 is a permanent magnet, 17 is a switch, 19 is an outer lid, and 23 is an inner lid. , 26 is rice, 27 is water, and 28 is a thick part (transmission means).

Claims (1)

[Claims] 1. A pot for storing rice to be cooked, and a pot for storing rice in the pot so that the optimum water absorption temperature of the rice to be cooked in the pot shifts from the upper part of the rice to the lower part as the rice cooking progresses. It is equipped with a heater that heats the lower outer circumferential portion and a heat-sensitive section provided to detect the temperature of the bottom of the pot, and at least at the end of rice cooking, the heat from the heater is transferred to the pot through the bottom of the pot. A rice cooker characterized by having a transmission means for facilitating the transmission of heat to a heat sensitive part. 2. Claim No. 2, characterized in that the heater is constituted by a heating body that is in close contact with the lower side of the pot, and the transmission means is constituted by arranging a heat-sensitive part close to the heating body. The rice cooker described in item 1. 3. Claims characterized in that the heater is constituted by a heating element that is in close contact with the lower side of the pot, and the transmission means is constituted by a thick wall portion that is integrally provided at the bottom of the pot. The rice cooker described in paragraph 1.