JPS6147525B2 - - 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 the heat of the electric heater is transferred from the hot plate to the bottom of the pot to cook rice. However, when rice is cooked in a rice cooker with such a conventional structure, the top part becomes dry and dry, and the bottom part becomes sticky with a lot of moisture, resulting in uneven cooking and an overall poor taste. There was a downside.

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 providing a pot storage section made of a heat conductive material that forms a space around the outer periphery of the pot, and disposing a heater in the space. A heating means is constituted by the part and the heat conductive member, and the heating means is configured to heat the food to be cooked in the pot so that the temperature of the upper part becomes higher than the temperature of the lower part. To provide a rice cooker capable of cooking rice evenly, greatly improving the taste of cooked rice, and being 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 an inner case serving as a bottomed cylindrical pot storage part with an open top surface, which is disposed inside the outer case 1 via a heat insulating material 5, and the upper end of this case is connected to the inner circumferential surface of the upper end of the outer case 1. 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 aluminum plate serving as a heat conductive part, and at least the inner surface is mirror-finished by chemical polishing or electrolytic polishing, and the diameter of the side part 4a becomes slightly larger as it goes upward. It is formed in a tapered shape. 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 inserted into the inner case 4.
It is removably plug-connected to a plug-in terminal 10 provided at the bottom of the. Reference numeral 11 denotes a bottomed cylindrical pot having an annular flange portion 11a formed at the upper end, and has a bottom portion 11b having a substantially planar shape and a side portion 11c.
is formed in an inclined taper shape similar to the side surface portion 4a, and a smooth circular arc surface 11d is formed between the bottom surface portion 11b 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 bottom part 11b has a dimension h from the sheathed heater 7.
Also, both side portions 11
c and 4a are arranged close to each other with a small gap (for example, about 1 mm). That is, a heating space k is formed on the outer peripheral surface of the pot 11 by the inner case 4, and the aforementioned sheathed heater 7 is located within this space k. By the way, the diameter d of the aforementioned sheathed heater 7 is set to be slightly smaller than the diameter D of the lower part of the pot 11, and the sheathed heater 7 is located below the circular arc surface 11d. and,
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 coded with fluororesin. Thus, the above-mentioned sheathed heater 7, the space k, and the heat conductive member constituting the inner case 4 cooperate to constitute a heating means s, and the pot 11 is heated by this heating means s. ing. Reference numeral 12 denotes a bottomed cylindrical protective case with an open bottom, which is vertically movably supported by a guide tube 13 provided at the inner bottom of the inner case 4 and provided at the lower end of the protective case 12. A compression coil spring 14 disposed between the flange 12a and the inner case 4 constantly urges upward, and the top surface of the protective case 12 is pressed against the bottom surface 11b of the pot 11. An inwardly curved flange 13a is formed at the upper end of the guide tube 13, so that when the pot 11 is removed from the inner case 4, the flange 12a of the protective case 12 is attached to the guide tube 13. Tsuba part 1
It engages with 3a to prevent it from coming off. 1
5 is a magnetic body made of a magnetic shunt material stuck to the inner bottom surface of the protective case 12. 16 has a knob on one end 17
The lever is attached by integral molding or the like, the middle part of which is rotatably supported via a pin 19 on a support arm 18 protruding from the lower surface of the inner case 4, and the other end part The rising portion 16a provided in the guide tube 13 is inserted through the hole 4c provided in the bottom surface 4b of the inner case 4, and
A permanent magnet 20 is fixed to the upper end of a. A knob 17 attached to the lever 16 projects 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 always supported in the direction of arrow a by a torsion coil spring 22. is energized by Although not shown, a micro switch is provided at the bottom of the inner case 4 and is closed when the lever 16 is pressed down.
By pressing down the permanent magnet 20, the magnetic body 15
When the sheathed heater is attracted, the microswitch is closed and the sheathed heater is energized. 2
Reference numeral 3 denotes an outer lid made of, for example, plastic, which is rotatably supported via a pin 24a on a hinge member 24 fixed to the upper end of the outer case 1, and a handle portion 25 for carrying is integrally formed on the upper surface. There is. 26 is an inner cover, which is connected to the outer cover 23 via a heat insulating material 27.
is fixed to the inner surface of the 28 is a hinge member 24
This is an engaging member located on the opposite side of the outer case 1 and fixed to the upper end of the outer case 1. When the outer cover 23 is closed, it engages with an engaging part (not shown) provided on the handle part 25 and closes the outer cover. 23 is held in a closed state, and the engagement can be released by pressing a push button 29. Reference numeral 30 denotes an inner lid that engages and supports an engaging portion 26a provided on the lower surface of the inner cover 26 via a supporting convex portion 31, and when the outer lid 23 is closed, the pot 1
It is adapted to come into pressure contact with the flange portion 11a of No. 1. 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 lid 23, and has a spherical body 34 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 via the space k. The water 36 in the pot 11 in contact with the arcuate surface 11d is heated to a high temperature, causing local convection as shown by arrow b in FIG. That is, 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, and rises along the inner wall of the pot 11 and goes to the top. Also, at the same time as this action, the bottom surface 4 of the inner case 4
b is also heated by the heater 7, and at this time the inner case 4
The inner surface of the case 4 is mirror-finished to reflect heat, but since the inner case 4 is made of aluminum, which is a heat-conducting material, and its thickness is as thin as approximately 1 mm, a heat-conducting effect occurs. Heat is evenly transmitted to the side surface 4a of the inner case 4, and the side surface 1 of the pot 11 is located with a slight gap from the inner case 4.
1c is heated through the space k. That is, pot 11
is heated by a heating means s by the cooperation of the sheathed heater 7, the space k, and the heat conductive members constituting the inner case 4. Therefore, the temperature of the upper, middle, and lower parts (indicated by A, B, and C in FIG. 1) of the rice 35 stored in the pot 11 is such that the temperature of the upper part A is earlier than the temperature of the middle part B and the lower part tends to rise. 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 35 in the upper part A absorbs more water as the rice cooking time progresses, the water level decreases, and the heat conduction in the upper part A becomes worse than when the water 36 has been hot (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 bottom part 11b of the pot 11.
Heat is applied to the water 36 from the bottom portion 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, whose temperature rises later than the upper part A, gradually reaches the range of 60°C to 70°C, and the rice 35 is located in the middle part B. The water absorption effect of rice 36 increases. After further time has passed, rice 36 is located in the middle part B.
As the water absorption action progresses, the water level in the pot 11 further falls as described above, and the rice 36 located in the middle part B is also prevented from absorbing more water than necessary, and the lower part C, whose temperature rises after the middle part B, is prevented from absorbing water more than necessary. The water absorption effect of rice 36 located at 36 is increased. Therefore, the water 36 in the pot 11
When all the water is absorbed by rice 35, the pot 1
When the bottom portion 11b of the magnetic body 1 enters a so-called dry-cooked state and the temperature rises rapidly, the temperature of the magnetic body 15 also rises via the protective case 12, and the magnetic permeability of the magnetic body 15 rapidly decreases. 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 spring 2
2, the rotational force acting on the lever 16 in the direction of arrow a exceeds the attraction force, and the permanent magnet 20 is moved downward away from the magnetic body 15, and the knob 17 is moved upward together with the lever 16. After the return movement, a micro switch (not shown) is opened and the sheathed heater 7 is cut off.

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 Shows the experimental results for rice cooking, with temperature T (℃) plotted on the vertical axis and time t plotted on the horizontal axis.
(minutes). In addition, in FIGS. 1 and 3, 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 and 53 = 150 mm, and when cooking 1.4 rice 35, the water + rice capacity is approximately 230 mm.
cc and the water level line W is approximately 85mm. Further, the cross-sectional diameter of the sheathed heaters 7 and 53 is 8 mm, so the pot 1
The distance between the outer bottom surface of the heater 1 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 upper part of the rice 35 (the center point 10 mm below the water surface of the pots 11 and 50), and C and C' are the lower part of the rice 35 (the center point 10 mm above the inner bottom surface of the pots 11 and 50). point), B, B' are rice 35
This figure shows the temperature change at the middle part (midway position between A, A' and B, B'), and each measuring point is shown with the same reference numeral in FIGS. 1 and 3.

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 disappears quickly, and the upper part of the pot 11
Water 36 exists in the lower part C of pot 11 until near the end of rice cooking, but it is slow to reach the optimum water absorption temperature. The amount of time the rice 35 stays in a water-absorbing 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 rice 35 located in the upper part A and the middle part B acts as a heat insulating layer. Because of this action, 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 uses a heater to heat the entire bottom of the pot, so the temperature at the bottom of the pot near the heater tends to rise before the temperature at the top, and as rice cooking progresses. The temperature rise at the top of the pot, where the water runs out first, is delayed, resulting in a dry rice with low water absorption, and conversely, until the end of cooking, the temperature rises fastest at the bottom of the pot, where the water is, and the rice remains at a high temperature for a long time. Because the rice was cooked in such a state, it absorbed more water than necessary and ended 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.

Moreover, in the above embodiment, the pot 11 is housed in the inner case 3, that is, in the space k, with a predetermined distance from the sheathed heater 7, so that it is similar to the pot 11 that is placed in close contact with the hot plate of the conventional structure. Since strict dimensional accuracy is not required at all, and there is no need to provide a hot plate, processing is extremely simple and costs can be greatly reduced, and heat conduction is greatly reduced due to deformation, corrosion, etc. It also becomes easier to handle because it does not change.

In addition, in this 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.
As is clear from the experimental results shown in Figure 2, the third
Thermal efficiency can be improved more than the method shown in the figure in which a space 52 is provided on the outer surface of the pot 50 and the pot 50 is heated using air convection within the space 52.

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 way, the heat transferred from the sheathed heater 4 to the inner case 4 by radiation is efficiently conducted from the side surface portion 4a to the side surface portion 11c, and the thermal efficiency can be further improved. .

In addition, in the above embodiment, the surface of the inner case 4 is mirror-finished 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 section, heat conduction member), 4a is a side view, 7 is a sheathed heater, 11 is a pot, k is a space, s is a heating means, 1
5 is a magnetic material, 20 is a permanent magnet, 23 is an outer cover, 26
is the inner cover, 30 is the inner lid, 35 is rice, 36 is water,
50 is a pot, 51 is a pot storage section, and 53 is a sheathed heater.

Claims (1)

[Claims] 1. A pot for storing food to be cooked, an outer case having a pot storage section made of a heat conductive member to be stored in the pot, and a heating space provided around the outer periphery of the pot by the pot storage section. and a heater provided in the space at a predetermined distance from the pot, and the heater, the space, and the heat conductive member constitute a heating means, and the heating means A rice cooker characterized by being configured to heat the food to be cooked in the rice cooker so that the temperature of the upper part of the rice cooker reaches a higher temperature before the temperature of the lower part.