JPS6147526B2 - - Google Patents

Description

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

BACKGROUND ART 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 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 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 has a configuration in which a heating space with an open upper end is provided around the outer periphery of a pot, and a heater is provided within this space at a predetermined distance from the pot. It is an object of the present invention to provide a boiling device that can cook food evenly, has a simple configuration, and reduces costs, and is easy to handle.

An embodiment in which the present invention is applied to a rice cooker will be described below with reference to the drawings. 1 is a substantially bottomed cylindrical outer case with an open top, and a heat insulating material 2 is placed inside this case.
An inner case 3 having a substantially bottomed cylindrical shape as a pot storage part is disposed through the inner case 2, and an annular decorative frame made of heat-insulating plastic, for example, fitted around the inner periphery of the upper end of the outer case 1. 4, the outer periphery of the upper end of the inner case 3 is fitted. Reference numeral 5 denotes a pot having an outwardly directed flange 6 formed on the upper opening edge, and the kneader 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 space 7 is formed by this, and this space 7 continuously faces the outer bottom surface and outer surface of the pot 5.
6a is a plurality of ventilation holes drilled in the flange 6;
a is a ventilation groove formed at the upper end of the decorative frame 4 to communicate the inside and outside of the space 7, and these ventilation holes 6a
The upper end of the space 7 is open through the ventilation hole 4a. 8A and 8B are two sheathed heaters that are curved into an approximately annular shape and are used for both cooking and keeping warm.
One sheathed heater 8A is supported within the space 7 via a support member (not shown) with a dimension d from the outer bottom surface of the pot 5, and its diameter is made slightly smaller than the outer diameter of the pot 5. Set the other sheathed heater 8
B has a dimension e on the outer circumferential surface of the pot 5 and is also provided in the space 7 so as to wrap around the pot 5;
is located a predetermined distance above the bottom surface of the 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, so that when the pot 5 is removed from the inner case 3, the flange 9a of the protective case 9 is attached to the guide tube 10. It engages with the flange 10a 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. and the other end is connected to the sliding shaft 1 via a pin 20.
It is rotatably connected to the lower end of 5. 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 a micro switch located opposite to one end of the lever 16 and fixed to the bottom plate 1a via a support plate 22;
When the lever 16 is rotated in the opposite direction of arrow b to attract the permanent magnet 14 to the magnetic body 12, the actuator 21a is pressed by the lever 16, thereby closing the sheathed heater 8A and 8B is now energized. 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 a grip portion 26 for carrying the case is integrally formed on the upper surface. ing. Reference numeral 27 denotes an inner cover, which is fixed to the inner surface of the outer cover 23 via a heat insulating material 28. 29 is an engagement member located on the opposite side of the hinge member 24 and screwed to the upper end of the outer case 1;
The engagement lever 30 is attached to the outer cover 23 so as to face this.
is rotatably supported via a pin 31.
When the outer cover 23 is closed, the engagement portion 30a provided at the tip of the engagement lever 30 is connected to the engagement member 30a.
It is designed to engage with the engaging portion 29a of 9,
The engagement lever 30 is rotatably biased by a spring (not shown) in a direction in which the engagement portion 30a engages with the engagement portion 29a. 32 is the inner cover, this is the inner cover 27
It is supported by a support pin 33 protruding from the lower surface of the holder so as to be movable up and down via a space 34, and is normally urged downward by a compression coil spring 35.
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. 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 microswitch 21, and a series circuit of a bimetal switch 36 and a diode 39 is connected in parallel to the microswitch 21.

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 wall 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, thereby placing the inner lid 32 on the top surface of the pot 5. The pan 5 is closed by pressure contact. Next, pick 17
By pressing down, 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 heater 8A is closed.
and 8B are energized. Sheathed heater 8A and 8
When B generates heat, the air in the space 7 is heated, causing convection as shown by arrow a in FIG. 1, and the pot 5 is heated through this heated air. In this case, some of the air that has risen inside the space 7 is
a and the ventilation groove 4a, and is further discharged to the outside from an exhaust hole (not shown) provided in the outer cover 23. In this way, a part of the air in the space 7 is removed. By discharging the rice, overheating near the upper end of the space 7 is prevented, and the rice is prevented from burning. 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. Figure 1 A, B
As a result of the measurement, the characteristic curve shown in FIG. 3, in which the vertical axis represents the temperature (t° C.) and the horizontal axis represents the elapsed cooking time (T), 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 at the upper part A of the pot 5 is lower than that at the middle part B and C. temperature tends to rise before that of . Now, the water absorption rate of rice 40 is most remarkable when the temperature is in the range of 60°C to 70°C, and the temperature of the upper part A of the pot 5 is higher than the middle part B and lower part C of 60°C to 70°C. By reaching the range of
will perform the water absorption action. As the rice cooking time elapses, the water 41 in the pot 5 is absorbed by the rice 40 and the water level drops, and the water level in the pot 5 is lowered.
The rice 40 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 effect of the rice 40 located in the middle part B increases. After further time has passed, rice 4 is located in the middle part B.
As the water absorption action of 0 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, and the lower part, where the temperature rises after the middle part B, is prevented from absorbing water more than necessary. The water absorption effect of rice 40 located at C increases. 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. body 1
2 as well, the temperature rises and the magnetic permeability decreases rapidly. Then, the attraction force acting between the magnetic body 12 and the permanent magnet 14 decreases, and when the attraction force becomes less than a predetermined value, the sliding shaft 15 acts on the lever 16 by its own weight and a spring (not shown). Due to the rotating force in the direction of arrow b, the force acting downward on the sliding shaft 15 exceeds the attraction force, and the permanent magnet 14 is moved downward away from the magnetic body 12, and the arrow of the lever 16 As the knob 17 is rotated in the b 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 sheathed heaters 8A and 8B via the bimetal switch 36 and the diode 39, and the sheathed heaters 8A and 8B are heated. 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 is transferred to the ventilation hole 6a of the flange 6.
The inside of the space 34 is heated through the heat, the pot 5 is kept warm, and the inner lid 32 is heated to prevent dew formation. Then, when the temperature of the inner case 3 reaches 70° C. or more through the space 34, the bimetal switch 36 opens, and the sheathed heaters 8A and 8B are cut off. After the rice is cooked, the bimetal switch 36 and the diode 39 control the power on and off of the sheathed heaters 8A and 8B as described above, and the power when the rice is on, so that the cooked rice 40 in the pot 5 can be kept for a long time. It is kept warm for an hour (see Figure 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. The optimal heating condition for keeping warm can be obtained.

As described above, according to the present embodiment, a space 7 is formed on the outer peripheral surface of the pot 5 by the inner case 3 and has an open upper end that faces continuously from the outer bottom surface to the outer surface of the pot 5. Sheathed heaters 8A and 8B for both cooking and keeping rice are disposed at a predetermined distance d and e from the outer bottom surface of the pot 5 in the portion 7, and these sheathed heaters 8A and 8B allow rice to be heated through the space 7. Since the pot 5 is heated to cook rice and keep it warm, the temperature in the upper part of the space 7 rises from the lower part due to convection and heat from the sheathed heater 8B, and the temperature distribution inside the pot 5 also changes to the temperature in the upper part A. tends to be higher than the middle part B and the lower part C. Therefore, when the water level in the pot 5 decreases as rice cooking progresses, the water 41 disappears fastest in the upper part A of the pot 5.
Rice 40 is heated to the optimum water absorption temperature (up to 60℃) at the beginning of cooking.
70° C.), and the rice 40 at the bottom of the pot 5, which contains water 41 to the end, reaches the optimal temperature for water absorption at the end of cooking.
That is, although the upper part of the pot 5 quickly reaches the optimum water absorption temperature, the water 41 runs out quickly, and the upper part of the pot 5
Although water exists in the lower part of the rice cooker until near the end of cooking, it is slow to reach the optimum temperature for water absorption, so the rice 40 in the pot 5 is in a water-absorbing state no matter where it is located in the upper part A, the middle part B, or the lower part C. The cooking time is approximately constant, and the water absorption rate is uniform throughout, resulting in less uneven cooking and a very good taste.

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

Furthermore, in the above embodiment, the upper end of the space 7 is connected to the ventilation hole 6.
Since the space 7 is in an open state by providing the space 7 and the ventilation groove 4a, overheating of the space 7 is prevented, and the rice is evenly cooked without sticking to the pot.

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.

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 described above, the present invention can provide a boiler that can cook food evenly, has a simplified configuration, reduces costs, and is easy to handle.

[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), 4 is a decorative frame, 4a is a ventilation groove, 5 is a pot, 6 is a flange, 6a is a ventilation hole, 7 is a space, 8A and 8B are Sheathed heater, 12 is a magnetic material, 14 is a permanent magnet, 16 is a lever, 21 is a micro switch,
23 is an outer cover, 32 is an inner cover, 34 is a space, 36 is a bimetal switch, 37 and 38 are power terminals,
39 is a diode, 40 is rice, and 41 is water.

Claims (1)

[Claims] 1. A pot for storing food to be cooked, an outer case having a pot storage section for storing the pot, and a heating space provided around the outer periphery of the pot by the pot storage section and having an open upper end. and a heater, which is provided in the space at a predetermined distance from the pot and heats the pot via the space.