JPS6147524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rice cooker with an improved heating method.

Conventionally, an electric rice cooker is a type in which, for example, a pot is removably placed on top of a hot plate having an electric heater, and heat from the electric heater is transferred from the hot plate to the bottom of the pot to cook the 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.

In addition, conventional structures require strict dimensional accuracy to ensure that the hot plate and pot are in close contact with each other, resulting in high costs.If the contact surfaces between the two become deformed or corroded during use, heat transfer may be impaired. The disadvantage is that the cooking becomes even and the unevenness of cooking increases.

The present invention has been made in view of the above circumstances, and includes a pot having a flat bottom portion and an arcuate surface formed between the bottom portion and the side portion, in the pot storage portion of the outer case. , by arranging an electric heater in a heating space formed by the pot storage section and the pot so as to be spaced apart from the pot and facing an area outside the flat portion, uneven cooking can be prevented. To provide a rice cooker which is capable of cooking rice without scorching, greatly improves the taste of cooked rice, and is inexpensive and easy to handle.

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 bottomed cylindrical outer case with an open top, and support legs 2 are attached to the lower end of the outer case.
A bottom frame 3 having a shape is fitted and fixed. Reference numeral 4 denotes a bottomed cylindrical inner case with an open top as a pot storage section, which is disposed inside the outer case 1 via a heat insulating material 5; It is fixed to a fitted annular decorative frame 6 made of heat-resistant plastic, for example, by screws. The inner case 4 is, for example, a press-molded product of aluminum, and at least the inner surface is mirror-finished by chemical polishing or electrolytic polishing, and the side surface 4a has a tapered shape that becomes slightly larger in diameter toward the top. It is formed. 7 is an annularly curved sheathed heater with a capacity of, for example, 600W, which is supported at a predetermined distance from the bottom surface 4b of the inner case 4 via a support member 8 and an insulator 9, and has a sheathed heater at both ends. The provided terminal portion 7a is removably plug-connected to a plug-in terminal 10 provided at the bottom of the inner case 4.
Reference numeral 11 denotes a bottomed cylindrical pot with an annular flange portion 11a formed at the upper end;
b, and the side surface portion 11c is formed in an inclined taper shape similarly to the side surface portion 4a, and a smooth arcuate surface 11d is formed between the bottom surface portion and the side surface portion 11c. The pot 11 is placed in the inner case 4 by placing the flange portion 11a on the decorative frame 6 so that the entire circumference is in close contact with the pot 11, but the height dimension H is It is set smaller than the inner case 4, and the flat part 11b is spaced a distance h from the sheathed heater 7, and both side parts 11c and 4a are close to each other with a small gap (for example, about 1 mm). It's summery. By the way, the direct diameter d of the sheathed heater 7 mentioned above
is set to be slightly smaller than the diameter D of the lower part of the pot 11, and the sheathed heater 7 is placed oppositely below the arcuate surface 11d, which is an area outside the flat portion 11b of the bottom surface of the pot 11. The pot 11 is, for example, a press-molded product made of aluminum, and the outer surface is alumite-treated, and the inner surface is alumite-treated or coated with fluororesin. Reference numeral 12 denotes a bottomed cylindrical protective case with an open bottom, which is supported in a vertically movable manner by a guide tube 13 erected at the inner bottom of the inner case 4, and is provided at the lower end of the protective case 12. The protective case 1 is constantly biased upward by the compression coil spring 14 disposed between the flange 12a and the inner case 4.
The upper surface of 2 is pressed against the flat part 11b of the pot 11. An inwardly curved flange 13a is formed at the upper end of the guide tube 13, and the pot 1
1 is removed from the inner case 4, the flange 12a of the protective case 12 engages with the flange 13a of the guide tube 13 to prevent it from coming off. Reference numeral 15 denotes a magnetic body made of a magnetic shunt material stuck to the inner bottom surface of the protective case 12. Reference numeral 16 denotes a lever with a knob 17 attached to one end by integral molding or the like, and the middle part of this lever is rotatably supported by a support arm 18 protruding from the lower surface of the inner case 4 via a pin 19. The guide tube 1 is connected to the guide tube 1 through a hole 4c provided in the bottom surface 4b of the inner case 4 through the rising portion 16a provided at the other end.
3, and a permanent magnet 20 is fixed to the upper end of the rising portion 16a. And lever 1
A knob 17 attached to the outer case 1 protrudes outward from a hole 21a of an operation panel 21 provided on the side surface of the outer case 1, and the lever 16 is attached to a torsion coil spring 22.
is always biased in the direction of arrow a. still,
Although not shown, there is a lever 16 at the bottom of the inner case 4.
A micro switch is provided that closes when the lever 16 is pushed down, and when the permanent magnet 20 is attracted to the magnetic body 15 by pushing down the lever 16, the micro switch is closed and the sheathed heater 7 is closed. It is now energized. 23 is a pin 2 attached to a hinge member 24 fixed to the upper end of the outer case 1.
The outer lid is made of plastic, for example, and is rotatably supported via the handle 4a, and has a carrying grip 2 on the top surface.
5 are integrally formed. 26 is an inner cover,
This is fixed to the inner surface of the outer lid 23 via a heat insulating material 27. Reference numeral 28 denotes an engaging member located on the opposite side of the hinge member 24 and fixed to the upper end of the outer case 1, which engages with an engaging portion (not shown) provided on the handle portion 25 when the outer lid 23 is closed. The outer cover 23 is held in a closed state by pressing the push button 29.
The engagement can be released by .
Reference numeral 30 denotes an inner lid that is engaged and supported by an engaging portion 26a provided on the lower surface of the inner cover 26 via a supporting convex portion 31, and this is in pressure contact with the flange portion 11a of the pot 11 when the outer lid 23 is closed. It's summery. Reference numeral 32 denotes a steam vent tube provided on the inner lid 30, which is inserted into an insertion hole 33 provided on the outer cover 23, and a spherical body 34 is disposed therein as a valve body.

Next, the operation of this embodiment configured as above will be explained. Washed rice 35 and water 36 necessary for cooking the rice 35 are stored in the pot 11, the flange portion 11a is placed on the decorative frame 6, the pot 11 is housed in the inner case 4, and the outer lid is closed. 23 is closed, and the inner lid 30 is brought into pressure contact with the upper surface of the pot 11 to close the pot 11.
occlude. Next, by pushing down the knob 17, the lever 16 is rotated in the opposite direction of arrow a, so that the permanent magnet 20 is attracted to the magnetic body 15. Then, based on the push-down operation of the knob 17, a micro switch (not shown) is closed, and the sheathed heater 7 is closed.
is energized and generates heat. Since the sheathed heater 7 is arranged to face the arcuate surface 11d of the pot 11, the radiant heat from the sheathed heater 7 is most efficiently transmitted to the arcuate surface 11d and comes into contact with the arcuate surface 11d. The water 36 in the pot 11 is heated to a high temperature, causing local convection as shown by arrow b in FIG. In other words, the water 36 in contact with the inner wall of the pot 11 is more likely to undergo convection than the water 36 in the center of the pot 11.
It rises along the inner wall of 1 and goes to the top. Simultaneously with this action, the bottom surface 4b of the inner case 4 is also heated by the heater 7. At this time, the inner surface of the inner case 4 is mirror-finished to reflect heat, but the thickness of the inner case 4 itself is Since it is thin at about 1 mm, it also has a heat conduction effect, and this heat conduction causes heat to be evenly transferred to the side surface 4a of the inner case 4, and the side surface 11c of the pot 11, which is located through a small gap from the inner case, to the side surface 11c of the pot 11. Heat. Therefore, the rice 35 stored in the pot 11
(A, B and C in Figure 1)
), the temperature in the upper part A tends to rise earlier than the temperature in the middle part B and the lower part C. Then, the heat from the sheathed heater 7 is transferred to the pot 1 by heat transfer.
However, as mentioned above, it is most efficiently transmitted to the water 36 that is in contact with the arcuate surface 11d closest to the season heater 7, and the water is transmitted to the entire area of the side surface 1.
1c, the heat of the sheathed heater 7 is applied to the bottom part 11b of the pot 11 during the initial and middle stages of rice cooking.
Almost no heat is supplied to the lower part C, and the temperature rise in the lower part C becomes slow. As the rice cooking time progresses, the water level of the light 35 in the upper part A decreases, and the heat conduction in the upper part A becomes worse than when there was water 36 (the rice is a kind of thermal insulator). The heat transfer gradually progresses from the upper part A to the lower part C, and at the end of the cooking stage, sufficient heat is transferred to the flat part 11b of the pot 11.
Heat is applied to the water 36 from the flat part 11b of the pot 11. Now, the water absorption rate of rice is 35, and the temperature is 60.
℃ to 70℃, and the temperature of the upper part A of the pot 11 reaches the range of 60℃ to 70℃ before the middle part B and lower part C for the above-mentioned reasons. The rice 35 located in the upper part A will absorb water. As the rice cooking time elapses, the water 36 in the pot 11 is absorbed by the rice 35, and the water level decreases, causing the water level in the pot 11 to drop.
The rice 35 located in the upper part A is automatically prevented from absorbing more water than necessary, and the middle part B, where the temperature rises after the upper part A, gradually reaches the range of 60°C to 70°C.
The water absorption action of the rice 36 located in the middle part B increases. After further time has passed, rice 3 is located in the middle part B.
As the water absorption action of 6 progresses, the water level in the pot 11 further decreases as described above, and the rice 36 located in the middle part B is also prevented from absorbing water more than necessary, and the lower part, where the temperature rises after the middle part B, is prevented. Rice 36 located in C
water absorption effect increases. Therefore, the water 3 in the pot 11
When all of the water in rice 35 is absorbed by the rice 35, the temperature of the flat part 11b of the pot 11 rises rapidly, causing the temperature of the magnetic body 15 to rise through the protective case 12. As a result, the magnetic permeability of the magnetic body 15 decreases rapidly. Then, the attraction force acting between the magnetic body 15 and the permanent magnet 20 decreases, and when the attraction force becomes less than a predetermined value, the rotational force acting on the lever 16 in the direction of arrow a by the spring 22 increases the attraction force. , the permanent magnet 20 is moved downward away from the magnetic body 15, the lever 16 and the knob 17 are returned upward, the micro switch (not shown) is opened, and the sheathed heater 7 is cut off. Ru.

By the way, the present applicant has recently developed a rice cooker as shown in the schematic diagram in Fig. 3 in order to eliminate the drawbacks of the conventional rice cooker.
A pot storage section 51 is provided on the outer peripheral surface of the pot 50 to store the pot 5.
A heating space 52 is provided continuously facing from the outer bottom surface to the outer surface of the rice cooker, and a sheathed heater 53 is disposed within this space 52 at a predetermined distance from the pot 50. They invented a rice cooker that can cook rice to a uniformly cooked state, but this rice cooker transfers the heat of the heater 53 to the pot 50 using air convection generated in the space 52, so its thermal efficiency is comparatively low. There was a tendency for the thermal efficiency to be poor, and research and development efforts were being continued to improve thermal efficiency.

Now, FIG. 2 shows how rice 35 is cooked using the rice cooker according to the embodiment of the present invention shown in FIG. 1 and the rice cooker shown in FIG.
1.4 This shows an example of cooking rice,
The vertical axis shows temperature T (℃), and the horizontal axis shows time t (minutes).
This is an example of the following. Also, Figures 1 and 3
In the figure, the diameter D of the lower part of the pots 11, 50 = 190
mm, height H = 140 mm, interval h = 10 mm, diameter d of the sheathed heaters 7, 53 = 150 mm, and the arc surface 50a of the pot 50 is set to have a smaller diameter than the arc surface 11d of the pot 11. The sea heater 53 is the pot 50
It faces the flat bottom surface portion 50b of. Also 1.4
When cooking 35 liters of rice, the water + rice capacity is approx.
The water line W is 85mm at 2300c.c. The cross-sectional diameter of the sheathed heaters 7 and 53 is 8 mm, and therefore the distance between the outer bottom surface of the pot 11 and the upper surface of the sheathed heater 7 is 6 mm. Further, the capacity of both the sheathed heaters 7 and 53 is 600W. In Figure 2,
A and A' are the top of rice 35 (center point 10mm below the water surface of pots 11 and 50), C and C' are the bottom of rice 35 (pot 1
1,50 center point 10mm above the inner bottom surface), B,
B' indicates the temperature change at the intermediate position 5 between the intermediate parts A, A' and B, B' of the rice 35, and each measurement point is
The same reference numerals are used in FIG. 3 and FIG.

That is, during rice cooking, the temperature of upper parts A and A' rises first, and the temperature of lower parts C and C' tends to rise later than upper parts A and A' and middle parts B and B', and the time required for cooking rice is This is the time it takes for the lower portions C and C' to reach 100°C. In the rice cooker of this embodiment shown in Figure 1, rice cooking is completed in 26 minutes, and in the rice cooker shown in Figure 3, it takes 26 minutes to complete cooking.
It takes 27 minutes. Therefore, the rice cooker of this example can reduce the rice cooking time by 1 minute compared to the rice cooker shown in FIG.
Electric power can be saved by 600 (W) x 1 (minute) / 60 (minutes) = 10 (W), and the heat exchange rate can be improved by an equivalent amount of 10W.

As described above, according to this embodiment, the temperature distribution within the pot 11 tends to be such that the temperature is high at the upper part A and becomes lower toward the middle part B and the lower part C. The rice 35 in the upper part A of the pot 11 will run out of water 36 the quickest due to the lowering of the water level in the pot 11.
reaches the optimum temperature for water absorption (60° C. to 70° C.) at the beginning of rice cooking, and the rice 35 in the lower part C of pot 11, where water 36 remains till the end, reaches the optimum temperature for water absorption at the end of cooking. That is, although the upper part of the pot 11 quickly reaches the optimum water absorption temperature, the water 36 runs out quickly, and the upper part of the pot 11
Water 36 exists in the lower part C of pot 1 until near the end of rice cooking, but it is slow to reach the optimum water absorption temperature. The time that the rice is in the water absorption state is approximately constant, and the rice can be cooked with a uniform water absorption rate as a whole.Moreover, at the end of cooking, the upper part A
Since the rice 35 located in the middle part B acts as a heat insulating layer, the temperature of the rice 35 in the lower part C can rise rapidly, and the cooking time will not be unnecessarily prolonged. By the way, the conventional structure was configured to heat only the bottom of the pot using a hot plate with a heater, so the temperature at the bottom of the pot near the heater tends to rise before the temperature at the top, making it difficult to cook rice. As cooking progresses, the rise in temperature at the top of the pot, where the water runs out fastest, is delayed, resulting in the rice being cooked in a dry state with low water absorption.Conversely, the temperature at the bottom of the pot, where water is present, rises the most until the end of cooking. Because the food is heated quickly and at high temperatures for a long period of time, it absorbs more water than necessary and ends up cooking in a sticky state, making it uneven and difficult to cook. However, in this embodiment, the rice 35 in the pot 11 is cooked in a substantially uniform water absorption state, so there is no uneven cooking and the taste can be greatly improved.

In addition, in the above embodiment, the pot 11 is housed in the inner case 3 with a predetermined distance from the sheathed heater 7, so strict dimensional accuracy is required as in the case of a pot that is closely attached to a conventional heating plate. Since it does not require any heat transfer or heating plates, processing is very simple and costs can be greatly reduced, and heat conduction does not change significantly due to deformation, corrosion, etc. Since there is no such thing, handling becomes easier.

In addition, in this embodiment, the sheathed heater 7 is connected to the pot 11.
Since the sheathed heater 53 is arranged to face the flat bottom part 50b of the pot 50 as shown in FIG. Compared to pot 1
The water in the pot 11 tends to cause local convection as shown by the arrow b, and the temperature rise in the upper part A of the rice 35 stored in the pot 11 is remarkable, and the rice 35 is cooked evenly and evenly. It is something that can be done.

In the above embodiment, the side surface 11c of the pot 11 and the side surface 4a of the inner case 4 are placed close to each other with an interval of 1 mm, but as shown in FIG. The side surface portion 4a is formed into a tapered shape that widens upwardly, so that the side surface portions 11c and 4a are in close contact with each other when the flange portion 11a of the pot 11 is positioned above the decorative frame 6. In this case as well, the point is that if the sheathed heater 7 is opposed to the outside of the flat part 11b of the bottom surface of the pot 11, the sheathed heater 7 can be connected to the inner case 4.
The heat transferred by radiation is also efficiently conducted from the side surface portion 4a to the side surface portion 11c, thereby further improving thermal efficiency.

Furthermore, in the above embodiment, the surface of the inner case 4 is mirror-treated to improve heat reflection, and the pot 1
Since the outer surface of 1 is alumite-treated to improve heat absorption, thermal efficiency can be further improved, but these treatments may be provided as necessary.

As explained above, the present invention provides a rice cooker that can cook rice evenly and greatly improve the taste of the finished rice, is inexpensive, is easy to handle, and has excellent thermal efficiency. can.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 show an embodiment of the present invention, Fig. 1 is a longitudinal cross-sectional view, Fig. 2 is a temperature characteristic diagram showing experimental results, and Fig. 3 is a schematic diagram showing a conventional structure. 4 are longitudinal sectional views of main parts showing other embodiments of the present invention. In the drawings, 1 is an outer case, 4 is an inner case (pot storage part), 7 is a sheathed heater, 11 is a pot, 11b is a flat part, 11c is a side part, 11d is an arcuate surface, 15 is a magnetic material, and 20 is a permanent part. Magnet, 23 is outer cover, 26 is inner cover, 30 is inner cover, 35 is rice, 36 is water, 50
51 is a pot storage section, and 53 is a sheathed heater.

Claims (1)

[Claims] 1. An outer case that includes a pot that is provided to store food to be cooked and has a flat bottom portion and an arcuate surface formed between the bottom portion and the side portion, and a pot storage portion that stores the pot. and a heating space provided on the outer peripheral surface of the pot by the pot storage section;
A rice cooker comprising: an electric heater provided in the space at a predetermined distance from the pot and facing an area outside the flat part of the bottom part.