JPH04122218A - Electric cooker - Google Patents

Abstract

PURPOSE:To obviate uneveness in cooking by providing a heating means which boils evenly objects to be heated in a container after the objects in the container are nearly boiled. CONSTITUTION:After rice 39 and water 40 to be heated are received previously in a container 15, a lid 17 is closed and a control means 29 is operated by an operating section 35. First, soaking cooking is carried out under 60 deg.C for 5 minutes. Current continuously supplied with 100% input to an exothermic body 22 for 5 minutes, interrupted thereafter for 10 minutes and then the process is shifted substantially to the rice cooking process in which current is supplied to the exothermic body 22 continuously with 100% input for about 10 minutes for boiling and then to the exothermic body 22 with 50% input. When a temperature detector 26 detects the completion of rice cooking, current to the exothermic body 22 is interrupted. After the completion of the rice cooking, the rice is steamed in high temperature by remaining heat, uneven cooking is obviated. Then, a heat retaining heater generates heat to provide the heat retaining condition.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an electric cooking device such as a rice cooker.

(Prior Art) In the conventional radiant heating rice cooker, a container 1, which is a pot, is housed in a container frame 2, as shown in FIG. A space 3 is formed, and a heating element 4 such as an annular sheathed heater is attached to the bottom of the container frame 2, and a heat sensitive element 5 for controlling the heating element 4 is pressed against the bottom of the container 1. It has become.

In the hot plate type rice cooker, as shown in FIG. 7, a container 7, which is an aluminum pot, is housed in a female frame 6, and a hot plate 8 is attached to the bottom of the container frame 6 so as to be in contact with the bottom of the container 7. At the same time, the heat sensitive body 10 that controls the heating element 9 of the hot plate 8 is pressed against the bottom of the container 7.

(Problem to be solved by the invention) It is generally said that gelatinization of rice begins at 55°C to 70°C, when the cell wall of the starch inside the rice is broken and heat and water enter the starch granules during cooking. However, in reality, it takes about 12 hours for rice to gelatinize at 70°C, so there is almost no gelatinization of rice at 70°C during rice cooking, and rather, the gelatinization of rice is almost at 98°C, which is at 70°C. It can be said that a condition in which water is present for 20 minutes or more at a temperature of °C or higher is required. In other words, the gelatinization is more likely to cause the cell walls to collapse when the thermal energy is high. Therefore, water absorption by rice due to gelatinization during actual rice cooking starts at 98°C, which is the boiling state, and rapidly increases when it reaches the boiling state. It can be concluded that the higher the thermal energy in the boiling state, the more active the process.

The radiant heating type rice cooker has a disadvantage in that the rice is cooked soft at the outer periphery of the container 1 and hard at the center of the container 1. In a radiant heating rice cooker, when rice cooking starts, heat flows from near the heating element 4 as shown by arrow A, that is, from the bottom outer periphery of the container 1 to the outer periphery of the container 1 due to heat conduction. After moving upward along the surface, it reaches the water surface, the center, and below the center. This heat flow is caused by the fact that the heating element 4 is arranged in an annular shape facing the outer periphery of the bottom of the container 1, and the watt density of the surface of the heating element 4 is very high, so that the surface temperature of the heating element 4 reaches 700. ~
It is a lick that reaches a high temperature of 800°C. When cooking rice in such a radiant heating rice cooker, as mentioned above, as the temperature rises, there will be a temperature difference in the water in the container 1, and the water will move from the higher temperature side to the lower temperature side, until the water boils. Therefore, the water temperature in the container 1 shifts as shown by arrow A, and in the center of the container 1, heat moves from the top to the bottom, and when heated further, it reaches a boiling state and the cell walls of the starch grains in the rice melt. It breaks, allowing water and heat to enter the interior. In this state, the rice rapidly absorbs water and becomes gelatinized.

However, once the water reaches a boiling state, the water temperature no longer rises, so no difference in water temperature occurs, and therefore almost no heat transfer occurs.

In this situation, when the bottom of the container 1 is heated by the heating element 4, the rice and water in the upper part of the container 1 act as a heat insulating layer, and the pressure in the lower part of the container 1 increases, forming bubbles and causing the so-called boiling phenomenon. occurs. Furthermore, when the heating element 4 generates heat, the bottom part of the container 1 that the heating element 4 faces has more thermal energy than other parts of the bottom, even if the temperature is approximately the same, and therefore this radiant heating rice cooker As shown by arrow B, boiling occurs only at the outer periphery of the container 1, and gelatinization progresses rapidly because the thermal energy in that area is high.As a result, the outer periphery of the container 1 absorbs too much water. On the other hand, the center of the container 1 absorbs less water and becomes hard, resulting in uneven cooking, and the surface of the center becomes concave, spoiling the image of deliciousness.

The hot plate type rice cooker has the disadvantage that, contrary to the radiant heating type rice cooker, the rice is cooked hard at the outer periphery of the container 7 and soft at the center of the container 7. This is because in a hot plate rice cooker, the container 7 and the hot plate 8 are in contact with each other at the outer periphery, so when rice cooking starts, the outer periphery of the bottom of the container 7 is mainly heated, and the water temperature inside the container 7 rises to the point indicated by the arrow. Transition as shown in . As the rice cooking progresses, the container 7 and the hot plate 8 become hot and thermally expand, and the center of the bottom of the container 7 comes into contact with the hot plate 8 as shown by the dashed line. Therefore, at the start of rice cooking, the outer periphery of the bottom of the container 7 is heated by the hot plate 8, but in the middle of rice cooking, the heating at the center of the container 7 becomes stronger, and boiling occurs at the center of the container 7, as shown by the arrow. . As a result, in a hot plate rice cooker, the outer periphery of the container 7 becomes hard due to water absorption or too little water absorption, while the center of the container 7 becomes soft due to water absorption or too much water, resulting in uneven cooking and a convex surface at the center. This spoils the image of how delicious it is when cooked.

Furthermore, in the radiant heating rice cooker, when the container 1 is taken out and the inside of the container body 2 is cleaned, the heating element 4 gets in the way and is difficult to clean, and the heating element 4 is exposed at the bottom of the container body 2. The drawback was that it gave the impression of being dangerous. In addition, in the hot plate rice cooker, if rice grains or the like adhere to the hot plate 8, the contact between the container 7 and the hot plate 8 will deteriorate when the container 7 is stored in the main body 6, causing unevenness. There were drawbacks such as the occurrence of

The present invention solves the above-mentioned problems and provides an electric cooker that can boil water-based materials at almost the same time after almost boiling them. The purpose is to provide

[Configuration of the Invention (Means for Solving the Problems) The present invention comprises a container 15 that accommodates a heated object 40 mainly consisting of water 39, and a radiant heating plate that faces substantially the entire surface of the bottom 15B of the container 15. 20 is provided, and after the object to be heated 39.40 in the container 15 reaches a substantially boiling state, the container 15 is
The heating means 23 is configured to uniformly boil the objects 39 and 40 inside.

Further, according to the present invention, a ceramic coating 24 mainly made of aluminum oxide and containing titanium oxide and cobalt oxide is provided on the surface of the radiant heating plate 20 that is substantially opposite to the entire surface of the bottom 15B of the container 15.

(Function) With the above configuration, when the object to be heated 3940 in the container 15 reaches a substantially boiling state, the heating means 23 heats the object to be heated 39.
40 can be heated evenly and boiled.

Further, with the above configuration, the radiant heating plate 20 can be easily cleaned by wiping it, and the color tone of the radiant heating plate 20 can be prevented from changing even when heated with high flame at a high temperature exceeding 500°C.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

11 is a refractory, which consists of an outer case 13 made of heat-resistant ABS resin connected by an upper frame part 12, and an inner case 14 which is a container storage part inside this outer case 13,
The inner case 14 is, for example, a press-molded product of a heat-conducting member such as an aluminum plate or a steel plate such as a stainless steel plate, and depending on the case, the inner surface is mirror-finished by chemical polishing or electrolytic polishing. Reference numeral 15 denotes a pot-like container that is housed in the inner drawer 14. The flange 16 of this container 15 is tightly locked to the upper frame portion 12, and 1i17 is removably provided at the upper opening of the container 15. It is being Further, a side sealed space 18, which is a space for heating, is formed between the side part 15A of the container 15 and the side part of the inner case 14, and a heating space 18 is formed between the bottom part 15B of the container 15 and the bottom part of the inner case 14. The bottom sealed space 19, which is a space for
It is formed in communication with

Reference numeral 20 denotes a substantially disc-shaped radiant heating plate provided substantially in the center of the bottom sealed space 19, which is made of a heat-resistant stainless steel alloy or the like, and is made of a high-radiation and highly heat-resistant material and has a predetermined heat capacity. A heat-resistant stainless steel pipe 22A is installed on the lower surface of the heating plate main body 21, which is substantially opposite to the entire surface of the bottom portion 15B of the container 15.
A heating element 22, such as a high temperature sheathed heater, is fixed by brazing with Nilagel wax 22B or the like. The heating element 22 is spirally arranged so as to avoid the central part of the lower surface of the heating plate main body 21 where heat is concentrated and mainly heat the central part from the side part 15A of the container 15. Further, this radiation heating plate 20 is set so that the bottom surface temperature of the heating plate main body 21 is approximately 700°C or less, and the distribution of the top surface temperature at the outer periphery, inner periphery, and the intermediate portion thereof is approximately 550°C to 60°C.
The bottom portion 15B of the container 15 is heated almost uniformly at 50° C. without any variation, and furthermore, after the object to be heated, which will be described later, stored in the container 15 has almost boiled, the space is, 19 and the radiation is heated. The outer periphery and the center of the container 15 are boiled almost simultaneously by a heating means 23 constituted by a heating plate 20. In addition, when the radiant heating plate 20 has a rice cooking capacity of 1.8Q, the heating element 22 is
If the temperature is 0W or more, for example 1200W, the boiling time is 5 to 15 minutes, for example around 10 minutes.

Further, a ceramic coating 24 is provided on the upper surface of the heating plate main body 21. This ceramic coating 24 is mainly made of aluminum oxide (AQ 203
) Ceramic powder containing about 90% of titanium oxide (Ti 02 ) and about 2% of cobalt oxide (Coo) is coated with a thickness of about 30 μll to 70 μm by plasma spraying or the like, and this ceramic coating 24 improves heat radiation to the container 15rpJ, and also provides a bluish black color to ensure a high quality appearance. In addition, @L of the side sealed space 18
+ is formed around 0.5Il to 1.511, and the bottom 15B of the container 15 has a slightly protruding center;
The height between the outer periphery of the bottom portion 15B and the heating plate main body 21, that is, the height L2 of the upper bottom sealed space 19A is at least 1111.
Furthermore, the width L3 of the communication space connecting the front nQ h side bottom closed space 19A and the lower bottom sealed space 19B is set to be around 81I. Reference numeral 26 denotes a temperature sensor such as a thermistor that can be inserted into a hole 27 formed in the center of the heating plate main body 21 and brought into contact with the container bottom 15B. It cooks rice under control.

FIG. 3 is a block diagram showing the electrical configuration, and 28 is an A/D converter connected to the temperature detector 26, which outputs a signal according to the detected temperature.

29 is a control means consisting of a microcomputer, which, as is well known, is connected to the CPU 30. Clock circuit 31, memory 32
．． Input circuit 33. It has an output circuit 34 and the like, and the control means 29 has a program to be described later. Further, the control means 29 drives and controls the heating element 22 using a drive circuit 36 in accordance with the operation signal from the operating section 35 and the detected temperature of the container 15, and also controls the drive of the display section 38 for displaying the time and the like using a drive circuit 37. It is.

Next, the operation of the above structure will be explained.

After storing rice 39 and water 40 as the objects to be heated in the container 15 in advance, the container 1117 is closed and the control means 29 is actuated by the operating section 35, whereby first, the rice is boiled at 60° C. or lower for 5 minutes. This is 100% for heating element 22 for 5 minutes
When inputted, the power is turned on continuously, then the power is turned off for 10 minutes, and then the rice cooking process begins.

In this rice cooking process, the heating element 22 is continuously energized with 100% input and boiled for about 10 minutes, and then the heating element 22 is energized with 50% input as described above, and the temperature sensor 2
6 or when the completion of rice cooking is detected, the power supply to the heat generator #22 is cut off. After the rice has been cooked in this manner, the rice is heated to a high temperature due to the residual heat, and then a heat-retainer (not shown) generates heat to keep it warm.

Further, the above action will be explained in detail.

When the heating element 22 generates heat with 100% input after the boiling, the radiant heat of the heating element 22 flows into the lower bottom sealed space 19B.
The side part 15A of the container 15 is heated by secondary radiation from the air through the communication space 25 to the side sealed space 18, and the heating plate main body 21 is heated by the heating element 22, so that the heating plate main body 2
The bottom 15B of the container 15 is heated by the radiant heat emitted from the container 15. At this time, since the distance between the outer periphery of the bottom part 15B is smaller than that of the center part, the outer periphery of the bottom part 15B is heated more strongly. As a result, as shown in the following table, each point ■■■ of the bottom $15B as shown in FIG.

Temperature distribution when the bottom of the container is 100'C (unit: °C) According to the above table, the temperature difference in the case of one example is 2
5° C., and 35° C. and 40° C. in both conventional examples, and it is clear that the temperature difference inside the container 15 is small in this practical example.

Furthermore, due to the heat conduction of the container 15 and the heating action of the side part 15A, the rice 39 and water 40, which are the objects to be heated, are heated from the bottom part 15B to the upper part of the side part 15A in sequence, that is, to each point. Heat moves sequentially from the upper center point ■ to the center point ■ and the lower point ■. In this way, as rice cooking progresses, the amount of radiant heat increases as the radiant heating plate 20, which has a predetermined heat capacity, cools down. In addition, Fig. 5 (A> shows the cooking temperature of 1,8Q cooking using the radiant heating plate 20, and Fig. 5 (B) shows the cooking temperature of 1,8Q cooking using the radiant heating rice cooker in the prior art. Comparing the two, in Fig. 5 <A>, the time TI for the entire container 15 to boil is 8 minutes, and it takes 9 minutes to complete the scouring.
The holding time at 8° C. or higher was 18.5 to 26.5 minutes, whereas in FIG. 5 minutes, and in Fig. 5 (A>), the temperature rises quickly and local heating is improved.After boiling, even though the water 40 in the container 15 is in a state where thermal convection is difficult to occur, the water 40 in the container 15
The bottom part 15B of the container 15 is uniformly heated as shown by the arrow E by the radiant heating plate 20, and as a result, each point near the side 15A of the container 15 and each point in the center of the container 15 are heated simultaneously. It boils violently and is blown upwards throughout the container 15. That is, the pressure at each point ■■■■ side at the bottom increases and bubbles are formed, and boiling can be continued in a state where water is uniformly present. As a result, uneven heating of rice, that is, variations in moisture content due to uneven heat energy, is reduced, eliminating uneven cooking and making it possible to cook rice with a flat surface. After this, to clean the container body 11, the container 15 is taken out and the ceramic coating 24 of the radiant heating plate 20 is lightly wiped to easily remove rice grains and the like.

FIG. 4 shows the surface infrared emissivity of the radiant heating plate (1200W, 620°C) provided with the ceramic coating 24 and the radiation heating heating element <1200 in the conventional technology.
This is a graph showing the surface infrared emissivity according to W, 770°C), and the radiation heating plate 20 according to this embodiment has a wavelength of 7.92 μm to 10.6 μm even at a relatively low temperature.
It turns out that the radiation efficiency can be improved in the μm range. The following table shows the rice cooking performance with and without Cerami Tsukusukorten 24.

This table shows that the ceramic coating 24 improves the water cooking efficiency.

As described above, in the embodiment, the container 15 for storing water 39 and rice 40 is stored in the refractory 11, and the lower part 15B and side part 1 of the container 15 are placed in the eight frames 11.
A heating space 19°18 is provided outside of the container 15.
A radiant heating plate 20 having a substantially uniform temperature distribution is provided substantially opposite to the entire surface of the bottom portion 15B of the space 18.1.
The heating means 23 of the container 15 formed by the radiant heating plate 9 and the radiant heating plate 20 is designed to boil the water 39 and the rice 40 in the container 15 almost simultaneously after the water temperature reaches a nearly boiling state. Heating can be done with a uniform heat balance, and therefore, uneven cooking such as rice 40 having too much water or too little water does not occur, and the rice cooking characteristics can be improved. Furthermore, when the rice is cooked, there are no irregularities on the top surface and the rice cooks flat, so the image of the food's deliciousness is not affected.

Further, the radiant heating plate 20 has a disc-shaped radiant heating plate main body 2.
By providing the heating element 22 in a spiral shape on the lower surface of 1,
Since the radiant heating plate main body 21 can have a substantially uniform temperature distribution during radiation, uneven cooking can be further eliminated.

In the embodiment described above, the radiation heating plate main body 21 is plate-shaped and is provided with a ceramic Y-scum coating 24, so that high temperature and high radiation can be achieved as shown in FIG.

Furthermore, by increasing the hardness of the upper surface of the radiant heating plate main body 21 with the ceramic coating 24, rice grains etc. can be easily swept away and scratches etc. can be prevented.
Moreover, since the ceramic coating 24 is mainly made of aluminum oxide and contains titanium oxide and cobalt oxide, the color tone of the ceramic coating 24 does not change even when heated over high flame at a high temperature exceeding 500° C., and the appearance quality deteriorates. can be prevented. In other words, it is well known that coating with ceramics is effective in ensuring high radiation efficiency in high-temperature conditions, but it is also effective in reducing color change in high-temperature conditions of approximately 500°C or higher and preventing rice grains from falling off and carbonizing. One possible way to create a black tone so that it is less noticeable when it occurs is to use ceramics made of silicon carbide (SiC) or iron oxide (Fed), ferric oxide (Fe203), and titanium oxide (T102). However, it is difficult to coat the silicon carbide by plasma spraying, etc., and those containing mainly iron oxide have low stability at high temperatures, and oxidation progresses to form iron oxide (Fe 304 ), resulting in red color or coating. There are problems such as the film itself peeling off.

It is well known that high-temperature stability can be improved by adding chromium oxide to iron oxide as the main ingredient, but such products are expensive and pose food hygiene problems. Furthermore, aluminum oxide (AQ 2
0s) with titanium oxide (T102) added, but in such a product, there is a problem that when the temperature reaches 500℃ or higher, the titanium oxide turns white and the whole becomes white. .

However, in the above example, titanium oxide and cobalt oxide, which is highly stable even at high temperatures, are added to aluminum oxide to prevent the blue color from disappearing, so even if the titanium oxide changes color toward white at high temperatures, the cobalt oxide makes the blue color stronger. As a result, the overall appearance color does not change much from the initial bluish-white black, so deterioration in appearance quality can be prevented. In addition, such aluminum oxide, titanium oxide,
and ceramic coating 24 made of cobalt oxide.
When the surface temperature reaches a high temperature of 700° C. or higher, the white color of titanium oxide becomes extremely strong. Therefore, the radiant heating plate 20 is set so that its operating temperature is 700° C. or lower.

It should be noted that the present invention is not limited to the above-mentioned embodiments. For example, in the embodiment, a sheathed heater is provided spirally on the lower surface of the radiant heating plate body so that the temperature distribution of the radiant heating plate body is almost uniform. Various modifications are possible, such as forming concentric grooves in the radiant heating plate main body, disposing a sheathed heater in the grooves, and providing a ceramic plate on the upper surface of the radiant heating plate main body.

[Effects of the Invention] The present invention provides a heating space formed between the container and the eight frames;
The heating means for the container is constituted by a radiant heating plate which is provided substantially opposite to the entire bottom surface of the container and has a substantially uniform temperature distribution, and the heating means is used to heat the heated material, mainly water, after the object to be heated has reached a substantially boiling state. Since the entire object to be heated is boiled almost simultaneously, uniform heating is possible during boiling, and the object to be heated can be cooked uniformly.

Furthermore, by providing a flat radiant heating plate opposite to the bottom of the container, the present invention makes it possible to easily wipe off dust on the top surface of the radiant heating plate.Furthermore, the surface of the radiant heating plate is mainly made of aluminum oxide, and titanium oxide is added to the surface of the radiant heating plate. By providing a ceramic coating containing cobalt oxide, it is possible to heat the product over high heat using high-temperature radiation, and even when used at high temperatures, there is no change in color tone, and deterioration in appearance quality can be prevented.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the present invention, in which FIG. 1 is a partially enlarged sectional view, FIG. 2 is an explanatory diagram showing parts of the container, and FIG. 3 is a block diagram. Figure 4 is a graph showing surface infrared emissivity, Figures 5 (A) and (B) are graphs of cooking temperature, Figure 6 is a cross-sectional view of a conventional example, and Figure 7 is a cross-sectional view of another conventional example. . 11... Refractory 15... Container 15A... Side part 15B... Bottom part 18, 19... Space 20... Radiation heating plate 23... Heating means 24... Ceramic coating 39... ...Water (substance to be heated) 40...Rice (object to be heated) Applicant: Toshiba Thermal Appliances Co., Ltd. Rido University Patent attorney Ushiki Patent attorney Susuki 1) Long Part 4 Part 6 Figures 1 and 7

Claims (2)

[Claims] (1) a container for storing a heated substance mainly composed of water; a container frame for storing the container; and a heating space provided within the container frame below the bottom and outside the side of the container; A radiant heating plate is provided in the bottom space at a predetermined distance from the bottom of the container, substantially facing the entire bottom of the container, and has a substantially uniform temperature distribution, and radiant heating is provided in the bottom space. An electric cooking device characterized in that the heating means of the container formed by a plate is configured to boil the entire object to be heated almost simultaneously after the object to be heated has reached a substantially boiling state. (2) a container for accommodating an object to be heated mainly composed of water, a container frame for accommodating the container, and a heating space provided within the container frame below the bottom and on the outside of the side of the container; A radiant heating plate provided in the bottom space at a predetermined distance from the bottom of the container and substantially facing the entire bottom of the container; and a ceramic coating containing titanium oxide and cobalt oxide.