JPS622802B2 - - 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. The structure is such that the heat is transferred to the bottom of the inner pot to cook rice. However, rice cookers with this conventional structure heat the entire bottom of the inner pot, so when rice is cooked, the top part is dry and has little moisture, and the bottom part is sticky and has a lot of moisture, resulting in so-called overcooked rice. The drawback was that it was uneven and the overall taste was poor.

The present invention has been made in view of the above circumstances, and provides a rice cooker that can cook rice evenly by improving the heating method and greatly improve the taste of cooked rice. The purpose is to

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 a substantially cylindrical outer case with open upper and lower surfaces, and a bottom plate 3 having support legs 2 is fixed to the lower surface of the outer case by screws.
Reference numeral 4 denotes an annular decorative frame made of a heat insulating material such as heat-resistant plastic that is fitted onto the upper end of the outer case 1, and a flange portion 5a formed at the upper end of the outer pot 5 is placed on this. Reference numeral 6 denotes a heating plate as a substantially annular heat conductive member having an inclined surface 7 formed by casting an aluminum alloy, for example, which has a downwardly directed leg portion 8 at one end, and a downwardly directed leg portion 8 at the other end. has a laterally directed leg 9, and the leg 8 has a screw 10.
The legs 9 are fixed to the inner bottom surface of the outer pot 5 with screws 11. Reference numeral 12 denotes a substantially annular storage groove formed on the lower surface of the heating plate 6, into which a sheathed heater 13, which is an electric heater, is fitted and held in place by a heat-resistant support 15 fixed with screws 14. . The sheathed heater 13 is located substantially in the center of the inclined surface 7, facing the inclined surface 7. 16 is a support plate whose one end is fixed to the outer pot 5 with a screw 10, and the other end of which is fixed to the bottom plate 3.
is screwed to. Reference numeral 17 denotes an inner pot made of aluminum alloy, for example, which has a sloped part _17b that slopes inward at the bottom of a side surface _17a , and when stored in the outer pot 5, the sloped part _17b becomes a heating plate. It is placed in close contact with the inclined surface 7 of the outer pot 5, and can be detached from the outer pot 5 at will. 18 is a magnetic thermostat that protrudes upward in the center of the outer cover 5, and this
8 _a is urged upward by a spring (not shown) and comes into close contact with the bottom surface 17 _c of the inner pot 17 to detect the temperature of the inner pot 17 . 19 is a lid that closes the upper surface of the outer pot 5, and has a knob _19a in the center.

Next, the operation of this embodiment configured as above will be explained. Storing washed rice 20 and water 21 necessary for cooking the rice 20 in the inner pot 17,
Place the inner pot 17 on the heating plate 6 inside the outer pot 5,
The outer pot 5 is closed with a lid 19. Next, when a switch (not shown) is closed, the sheathed heater 1
3 is energized, and the inner pot 17 is heated by the sheathed heater 13 via the heating plate 6. By heating the inner pot 17, the rice 20 in the inner pot 17 is cooked. and the lower part (indicated by A, B, and C in Figure 1), and the measurement results are shown in Figure 2, where the vertical axis shows the temperature (t°C) and the horizontal axis shows the elapsed cooking time T. A characteristic curve was obtained. That is, in this embodiment, the inner pot 17 is provided with an inclined part 17 _b at the lower part of the side part 17 _a , and the inclined part 1
Since 7 _b is in close contact with the inclined surface 7 of the heating plate 6,
The heat of the sheathed heater 7 is most efficiently transmitted to the inclined portion _17b , and the inner pot 17 in contact with the inclined portion _17b
The water 21 inside is heated to a high temperature, causing local convection as shown by arrow a in FIG. In other words, inner pot 1
The water in contact with the inner wall of No. 7 is more likely to undergo convection than the water in the center of the inner pot, and the water near the inner pot rises along the inner wall of the inner pot and goes to the upper part. The temperature tends to rise before the temperature of . Heat from the heating plate 6 attempts to be transmitted to the entire area of the inner pot 17 by heat transfer, but as described above, the water 21 in contact with the inclined surface 7 closest to the sheathed heater 13
The sheathed heater 1
In the early and middle stages of rice cooking, almost no heat is supplied to the bottom part _17c of the inner pot 17, and the temperature rise in the lower part C becomes slow. As the rice at the top absorbs more water as the cooking time progresses, the water level decreases.
Heat conduction in the upper part is worse than when water is hot up until now, and the heat transfer (the rice acts as a kind of thermal insulator) gradually progresses from the upper part to the lower part, and at the end of the cooking stage, the bottom part 17 of the inner pot 17 is heated. _The heat is sufficiently transferred to the water 21 from the bottom part _17c of the inner pot 17. Now, the water absorption rate of rice 20 is at a temperature of 60℃.
This is most noticeable when the temperature is in the range of 70°C to 70°C, and the temperature of the upper part A of the inner pot 17 reaches the range of 60°C to 70°C earlier than the middle part B and lower part C for the reasons mentioned above. The rice 20 located in the upper part A will absorb water. As the rice cooking time progresses, the water 21 in the inner pot 17 is absorbed by the rice 20 and the water level drops, and the rice 20 located in the upper part A automatically absorbs more water than necessary. As a result, the middle part B, whose temperature rises later than the upper part A, gradually reaches a range of 60°C to 70°C, and the water absorption effect of the rice 20 located in the middle part B increases. As time passes further and the water absorption action of the rice 20 located in the middle part B progresses, the water level in the inner pot 7 further decreases as described above, and the rice 20 located in the middle part B progresses.
0 is also prevented from absorbing more water than necessary, and the rice 20 located in the lower part C where the temperature rises after the middle part B increases its water absorption action. Then, when the water 21 in the inner pot 17 is completely absorbed by the rice 20,
When the bottom surface _17c of the inner pot 17 enters a so-called dry cooking state and the temperature rises rapidly, the thermostat 18 is opened and the sheathed heater 13 is cut off.

According to this embodiment, the temperature distribution within the inner pot 17 is such that the temperature at the upper part A is high and tends to decrease toward the middle part B and the lower part C. The rice 20 in the upper part A of the inner pot 17, where the water 21 disappears fastest as the water level in the inner pot 17 decreases, is kept at the optimal temperature for water absorption (60°C to 70°C) at the beginning of rice cooking.
℃), and the rice 20 in the lower part C of the inner pot 17, which contains water 21 to the end, reaches the optimum temperature for water absorption before the rice is cooked. That is, the upper part of the inner pot 17 quickly reaches the optimum temperature for water absorption, but the water 21 also runs out quickly, and the lower part of the inner pot 17 retains water until almost the end of the rice cooking period, but reaches the optimum temperature for water absorption. Since it is also slow, the inner pot 1
No matter where the rice 20 in 7 is located in the upper part A, the middle part B, or the lower part C, the time in which it absorbs water is approximately constant, and it can be cooked with a uniform water absorption rate as a whole. can. By the way, since the conventional structure was such that the entire bottom of the inner pot was heated by the heater, the temperature of the lower part of the inner pot near the heater tended to rise before the temperature of the upper part.
As the rice cooks, the rise in temperature at the top of the inner pot where the water runs out the quickest is delayed, resulting in the rice being cooked in a dry state with low water absorption. Because the temperature rises the fastest and the food is kept at a high temperature for a long time, it absorbs more water than necessary and ends up cooking in a sticky state, resulting in uneven cooking and poor quality. However, in this embodiment, the inner pot 1
Since the rice 20 in 7 is cooked in a substantially uniform water absorption state, there is no uneven cooking and the taste is greatly improved.

FIG. 3 shows another embodiment of the present invention, in which an annular rising portion 17 is provided on the lower outer periphery of the inner pot 17.
d, and the lower surface of this rising portion _17d is placed on the upper surface of the heating plate 22 as an annular heat conducting member.
Due to the convection indicated by , the temperature of the upper part A tends to rise before the temperature of the middle part B and the lower part C, and the same effect as in the above-mentioned embodiment is achieved.

In this embodiment, the rising portion _17d may be provided as necessary, and the heating plate 22 may be brought into close contact with the lower side of the inner pot 17, or the heating plates 6 and 22 may be connected to the inner pot. 17 may be placed close to each other with a slight gap between them.In short, the lower outer peripheral portion of the inner pot 17 may be heated by a heater.

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, such as being applicable to a rice cooker equipped with a heat-retaining function. can.

As described above, the present invention can provide a rice cooker that can cook rice evenly and greatly improve the taste of the cooked rice.

[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 drawing, 5 is an outer pot, 6 is a heating plate (thermal conduction member), 13 is a sheathed heater, 17 is an inner pot, 17 _a is a side part, 17 _b is an inclined part, 17 _c is a bottom part, 17 _d
is the rising part, 18 is the thermostat, 20 is the rice,
21 is water, and 22 is a heating plate (thermal conduction member).

Claims (1)

[Claims] 1. A pot for storing rice to be cooked, a heat conductive member provided in close proximity to or in close contact with the lower outer periphery of the pot, and a heat-conducting member that adjusts the optimal temperature for water absorption of the rice to be cooked in the pot as rice cooking progresses. A rice cooker comprising: an electric heater that heats the pot via the heat conductive member so as to move from the top to the bottom.