JPS6146125B2 - - Google Patents

Description

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

Conventionally, an electric rice cooker is a type in which, for example, a pot is removably disposed on the top of a hot plate having an electric heater, and rice is cooked by transmitting rice from the hot plate of the electric heater to the bottom of the pot. 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 includes a heating space provided around the outer periphery of a pot, a heater provided within the space at a predetermined distance from the pot, and a heater provided within the space at a predetermined distance from the pot. By having a structure equipped with a heat-retaining heater, it is possible to cook food evenly, the structure is simplified, and costs can be reduced. Moreover, the boiler is easy to handle and can maintain good heat retention after cooking. The purpose is to provide.

An embodiment in which the present invention is applied to a rice cooker will be described below with reference to the drawings. Reference numeral 1 denotes an outer case having a substantially bottomed cylindrical shape with an open top surface, and an inner case 3 having a substantially bottomed cylindrical shape serving as a pot storage section is disposed inside this via a heat insulating material 2. The outer periphery of the upper end of the inner case 3 is fitted into an annular decorative frame 4 made of heat-resistant plastic having heat insulating properties, which is fitted around the inner periphery of the upper end. Reference numeral 5 denotes a pot having an outwardly directed flange 6 formed at the upper opening edge, and this pot is disposed within the inner case 3 by placing the flange 6 on the upper surface of the decorative frame 4. The height and outer diameter of the pot 5 are each set to be smaller than the inner case 3, so the outer circumference of the pot 5 is surrounded by the inner case 3.
A closed space 7 is formed, and this space 7 continuously faces the outer bottom surface and outer surface of the pot 5. Reference numerals 8A and 8B are two sheathed heaters that are curved into an approximately annular shape and are used for both cooking and heat preservation. The sheathed heater 8B has a diameter slightly smaller than the outer diameter of the pot 5. It is provided so as to wrap around the pot 5 and is positioned a predetermined distance above the bottom surface of the pot 5. Reference numeral 9 denotes a bottomed cylindrical protective case with an open bottom, which is supported so as to be movable up and down by a guide tube 10 erected at the inner bottom of the inner case 3, and provided at the lower end of the protective case 9. A compression coil spring 11 disposed between the flange 9a and the inner case 3 constantly urges upward, and the top surface of the protective case 9 is pressed against the bottom surface of the pot 5. An inwardly curved flange 10a is formed at the upper end of the guide tube 10, and when the pot 5 is removed from the inner case 3, the protective case 10a
The flange 9a of the guide tube 10 engages with the flange 10a of the guide tube 10 to prevent it from coming off. Reference numeral 12 denotes a magnetic body made of a magnetic shunt material stuck to the inner bottom surface of the protective case 9. Reference numeral 13 denotes a guide tube portion formed in a bulge approximately in the center of the inner bottom of the inner case 3, into which a sliding shaft 15 having a permanent magnet 14 fixed to its upper end is inserted so as to be vertically movable. 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 via a pin 19 on a support arm 18 erected on the bottom plate 1a of the outer case 1. The other end is rotatably connected to the lower end of the sliding shaft 15 via a pin 20. A knob 17 attached to the lever 16 projects outward from a hole 1b provided in the side surface of the outer case 1, and the lever 16 is always biased in the direction of arrow b by a torsion spring (not shown). There is. 21 is lever 16
A micro switch is located opposite to one end and is fixed to the bottom plate 1a via a support plate 22. This is a micro switch that is operated by rotating the lever 16 in the opposite direction of arrow b to attract the permanent magnet 14 to the magnetic body 12. When that lever 1
6 closes the actuator 21a and energizes the sheathed heaters 8A and 8B. Reference numeral 23 denotes an outer cover made of, for example, plastic, which is rotatably supported via a pin 25 on a hinge member 24 screwed to the upper end of the outer case 1, and has a handle portion 26 integrally formed on the upper surface for carrying. ing. Reference numeral 27 denotes an inner cover, which is fixed to the inner surface of the outer lid 23 via a heat insulating material 28.
Reference numeral 29 denotes an engagement member located on the opposite side of the hinge member 24 and screwed to the upper end of the outer case 1. An engagement lever 30 is rotated via a pin 31 on the outer cover 23 so as to be opposite to this engagement member. Possibly supported. The engaging portion 30a provided at the tip of the engaging lever 30 engages with the engaging portion 29a of the engaging member 29 when the outer cover 23 is closed. Engagement part 30 by a spring that does not
a is rotationally biased in a direction to engage with the engaging portion 29a. Reference numeral 32 denotes an inner cover, which is supported by a support pin 33 protruding from the lower surface of the inner cover 27 so as to be movable up and down via a space 34, and is normally biased downward by a compression coil spring 35. has been done. Therefore, when the outer lid 23 is closed, the inner lid 32 comes into pressure contact with the flange 6 of the pot 5 to close the pot 5. Reference numeral 6a designates a plurality of vent holes formed in the flange 6, through which the spaces 7 and 34 are communicated with each other. 36 is a bimetal switch attached to the outer bottom surface of the inner case 3, and this is designed to open and close when the temperature of the inner case 3 is around 70°C, for example.

FIG. 2 shows the electrical configuration of this embodiment, in which a micro switch 2 is connected between power terminals 37 and 38.
1, a parallel circuit of sheathed heaters 8A and 8B is connected to the micro switch 21, a bimetal switch 36, a diode 39, and a series circuit of a heat-retaining heater 42 provided in the space 7 so as to correspond to the outer surface of the pot 5. are connected in parallel.

Next, the operation of this embodiment configured as above will be explained. Washed rice 40 and water 41 necessary for cooking the rice 40 are stored in the pot 5, the flange 6 is placed on the decorative frame 4, and the pot 5 is placed in the inner case 3.
The outer lid 23 is rotated in the closing direction to engage the engaging portion 30a of the engaging lever 30 with the engaging portion 29a of the engaging member 29, and the inner lid 32 is placed on the top surface of the pot 5. The pan 5 is closed by pressure contact. Next, by pressing down the knob 17, the lever 16 is rotated in the opposite direction of arrow b, and the sliding shaft 15 is moved upward so that the permanent magnet 14 is attracted to the magnetic body 12. Then, the micro switch 21 is closed based on the push-down operation of the knob 17, and the sheathed heaters 8A and 8B are energized. Sheathed heaters 8A and 8B
When heat is generated, the air in the sealed space 7 is heated and convection occurs as shown by arrow a in Figure 1.
The pot 5 is heated through this heated air.
By heating the pot 5, the rice 40 in the pot 5 is cooked, but the inventor of the present invention has determined that the temperature changes during cooking can be measured in the upper, middle, and lower portions of the rice 40 stored in the pot 5. The measurement results are shown in Figure 3, 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 space 7 is formed so as to continuously face the outer bottom surface and the outer surface of the pot 5, and the sheathed heaters 8A and 8B are arranged with dimensions d and e from the pot 5, respectively. Therefore, the convection shown by the arrow a mentioned above is performed relatively well, and the temperature above the space 7 tends to rise first, so that the temperature in the upper part A of the pot 5 tends to rise.
The temperature of the middle part B and the lower part C tends to rise before the temperature of the middle part B and the lower part C. Now, the water absorption rate of rice 40 depends on the temperature.
It is most noticeable when the temperature is between 60℃ and 70℃,
When the temperature of the upper part A of the pot 5 reaches the above-mentioned range of 60°C to 70°C before the middle part B and the lower part C, the rice 40 located in the upper part A starts to absorb water. As the rice cooking time progresses, the water level of the water 41 in the pot 5 drops as it is absorbed by the rice 40, and the rice 40 located in the upper part A automatically absorbs more water than necessary. The middle part B, where the temperature rises later than the upper part A, gradually reaches the range of 60℃ to 70℃, and the middle part B
The water absorption effect of rice 40 located at Further, as time passes and the water absorption action of the rice 40 located in the middle part B progresses, the water level in the pot 5 further decreases as described above, and the rice 40 located in the middle part B is also prevented from absorbing water more than necessary. , the rice 40 located in the lower part C, where the temperature rises later than the middle part B, absorbs more water. When all of the water 41 in the pot 5 is absorbed by the rice 40 and disappears, the bottom of the pot 5 enters a so-called dry cooking state and the temperature rises rapidly, causing magnetism to flow through the protective case 9. The temperature of the body 12 also increases and its magnetic permeability decreases rapidly. Then, the magnetic material 12
When the attraction force acting between the permanent magnet 14 and the permanent magnet 14 decreases, and the attraction force becomes less than a predetermined value, the sliding shaft 15
Due to its own weight and the turning force in the direction of arrow b acting on the lever 16 by a spring (not shown), the force acting downward on the sliding shaft 15 exceeds the attraction force, and the permanent magnet 14 becomes magnetic. The arrow b of the lever 16 moves downward away from the body 12 and is displaced.
With the rotation in the direction, the knob 17 is returned upward, the micro switch 21 is opened, the sheathed heaters 8A and 8B are cut off, and rice cooking is completed.

When the rice cooking is finished, the temperatures of the pot 5, the spaces 7 and 34, and the inner case 3 gradually decrease, but when the temperature of the inner case 3 falls below 70°C, the bimetal switch 36 closes. A half-wave of AC power is supplied to the heat-retaining heater 42 through the bimetal switch 36 and the diode 39, and the heat-retaining heater 42 is heated. At this time, sheathed heaters 8A and 8B are connected in series with the heat retention heater 42.
Current is also supplied to the heater 4, but the amount of current is
2, the sheathed heaters 8A and 8B perform auxiliary heating for keeping warm. Due to this heat, the air in the space 7 is convected and heated as shown by the arrow a as described above, and the heated air heats the inside of the space 34 through the ventilation hole 6a of the flange 6. This heat keeps the pot 5 warm and heats the inner lid 32 to prevent dew formation. Then, the inner case 3 is inserted through the space 34.
Bimetal switch 3 is activated when the temperature exceeds 70℃
6 opens, the heat retention heater 42 and the sheathed heaters 8A and 8B are de-energized. Then,
After rice cooking is completed, the heat retention heater 42 and the sheathed heater 8 are turned on.
As A and 8B mentioned above, the bimetal switch 36 and the diode 39 control the power on/off and on, and the cooked rice 40 in the pot 5 is kept warm for a long time (see Fig. 3). . In this case, it is generally better to heat the upper part of the pot 5 because the taste of the rice does not change even after a long time has passed after cooking, but the temperature of the upper part of the space 7 tends to be high even when keeping warm. As a result, a heating state optimal for keeping warm can be obtained, and since heating for keeping warm is performed through the space 7, there is no local heating, and therefore good heat keeping can be achieved.

As described above, according to this embodiment, a space 7 sealed by the inner case 3 is formed around the outer periphery of the pot 5, and a space 7 is formed at a predetermined distance d, e from the outer bottom surface of the pot 5 within this space 7. Since the sheathed heaters 8A and 8B are used to heat the pot 5 and cook rice through the space 7, the space 7 is free from convection and sheathed heaters. 8B
The temperature in the upper part rises higher than the lower part due to the heat of rice cooking, and the temperature distribution inside the pot 5 also shows that the temperature in the upper part A tends to be higher than the middle part B and the lower part C. The rice 40 in the upper part A of the pot 5, where the water 41 disappears the quickest due to the drop in water level, reaches the optimum temperature for water absorption (60°C to 70°C) at the beginning of rice cooking, and the water 41 reaches the optimum water absorption temperature until the end.
The rice 40 in the lower part C of the pot 5 with rice cooker 1 reaches the optimum water absorption temperature at the end of cooking. That is, the upper part of the pot 5 reaches the optimum water absorption temperature quickly, but the water 41 disappears quickly, and the lower part of the pot 5 retains water until near the end of rice cooking, but reaches the optimum water absorption temperature slowly. Therefore, regardless of whether the rice 40 in the pot 5 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 the rice 40 is cooked with a uniform water absorption rate as a whole. There is less uneven cooking and the flavor is much better.

Moreover, in the above embodiment, the pot 5 is housed in the inner case 3 through the space 7, so that strict dimensional accuracy is not required at all, unlike the conventional pot which is placed in close contact with a hot plate. Since there is no need to provide a hot plate, processing is very simple and costs can be greatly reduced.Furthermore, heat conduction does not change significantly due to deformation or corrosion, making handling easier. .

Incidentally, the sheathed heaters 8A and 8B of the above embodiment may be constituted by a single heater, in short, they are provided at a predetermined distance from the pot 5, so that the temperature of the upper part of the pot 5 rises earlier than the lower part. All you have to do is arrange it accordingly.

In addition, in the above configuration, the diode 39 is omitted and the sheathed heater 8A is operated only by the heat-retaining heater 42.
In such a configuration, the current to the sheathed heaters 8A and 8B may be controlled.
The heater mainly functions for heating during boiling, and the heat generated during keeping warm is negligible, so it essentially functions as a heater exclusively for boiling.

Further, in the above embodiment, the present invention is applied to a rice cooker as the most effective application example, but it can be widely applied to a rice cooker that retains heat after cooking.

As explained above, the present invention enables uniform cooking, simplifies the structure and reduces costs, is easy to handle, and can maintain heat without causing local heating after cooking. We can provide a boiler.

[Brief explanation of the drawing]

The drawings show an embodiment in which the present invention is applied to a rice cooker, and FIG. 1 is a longitudinal sectional view, FIG. 2 is an electrical configuration diagram, and FIG. 3 is a temperature characteristic diagram. In the drawings, 1 is an outer case, 3 is an inner case (pot storage part), 5 is a pot, 7 is a space, 8A and 8B are sheathed heaters, 12 is a magnetic material, 14 is a permanent magnet, 16
is a lever, 21 is a micro switch, 23 is an outer lid, 32 is an inner lid, 34 is a space, 36 is a bimetal switch, 37 and 38 are power terminals, 39 is a diode, 40 is rice, 41 is water, 42 is heat insulation It's a heater.

Claims (1)

[Claims] 1. A pot for storing food to be cooked, an outer case having a pot storage section for storing the pot, a heating space provided around the outside of the pot by the pot storage section, and this space. A space is provided in the space at a predetermined distance from the pot so that the optimum water absorption temperature of the food to be boiled shifts from the upper part of the food to the lower part as the cooking progresses. This boiler is equipped with a heater that heats the pot and a heat-retaining heater that keeps the food warm after it has been boiled.