JPS6052805B2 - boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler that has been improved so that the electric heater is turned off at the end of the cooking period to sufficiently uniformize the cooked food.

When cooking rice, if you hold the rice at a high temperature above Sanskrit °C for more than 1 minute after the rice is cooked, the rice will be evenly distributed and the rice will be cooked very well. When all the water has been absorbed by the rice and the rice is drying up, the temperature at the bottom of the pot suddenly rises, and the electricity to the electric heater is cut off. This is done using thermal energy stored in a pot.

However, since the stored thermal energy is reduced by radiating heat to the outside air, especially in winter when the ambient temperature around the pot is low, the temperature of the pot may drop below μs℃ before the required time (more than 1 minute) has elapsed. There is a tendency for the rice to become uneven and not be able to be sufficiently uniformed.

Therefore, in order to ensure sufficient heat distribution even in winter, it is possible to make the pot thicker to increase the amount of heat stored, or cover the pot with an insulating material to reduce the amount of heat dissipated, but this requires a large amount of material. The drawbacks are that it is heavy, the structure is complicated, and the manufacturing cost is high. The present invention has been made in view of the above circumstances, and by having a structure in which the electric heater is turned off immediately after the completion of cooking, it is possible to maintain the cooked food at a high temperature suitable for uneven cooking for a long time. To provide a simple-configured and inexpensive boiler that can be used for cooking.

An embodiment in which the present invention is applied to a heat-retaining rice cooker will be described below with reference to the drawings.

Reference numeral 1 denotes a bottomed cylindrical outer case with an open upper surface, and a bottom frame 4 having supporting legs 2 fixed thereto with screws 3 is fitted and fixed to the lower end of the outer case.

Reference numeral 5 denotes a bottomed cylindrical inner case with an open top surface, which is disposed inside the outer case 1 via a heat insulating material 6, and a flange 5a formed at the upper end of the inner case 5 is connected to the outer case 1. An annular decorative frame 7 made of heat-resistant plastic, for example, fitted around the inner periphery of the upper end is fixed with screws, and the side surface 5b- is formed in a tapered shape that becomes slightly larger in diameter as it goes upward. has been done.

Reference numeral 8 denotes a bottomed cylindrical pot having an outwardly directed annular flange part Ba formed at its upper end, and the flange part 8a is placed on the flange part 5a so that the entire circumference is in close contact with the pot. It is arranged inside the inner case 5.

In this pot 8, the side portion 8b is the side portion 5 of the inner case 5.
The pot 8 is formed into a tapered shape substantially similar to that of the inner case 5, and both side surfaces 5b and 8b are close to each other with a slight gap (for example, about 1 m).
The depth dimension is set to be smaller than the depth dimension by a predetermined length. Reference numeral 9 denotes an annularly curved sheathed heater, in which terminal portions 9a formed at both ends are removably plug-connected to plug-in terminals 10 provided on the bottom surface portion 5c of the inner case 5; is supported by the bottom part 5c via the support member 11 and the insulator 12, and is formed by the inner case 5 and the pot 8 at a predetermined distance from the bottom part 5c and the bottom part 8c of the pot 8, respectively. It is located in a closed space.

Reference numeral 13 denotes a first manual return type thermoswitch, which will be described in detail below.

Reference numeral 14 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 15 formed bulging at the inner bottom of the inner case 5, and provided at the lower end of the protective case 14. The protective case 1 is constantly biased upward by a compression coil spring 17 disposed between the flange 14a and the annular spring receiving plate 16 attached to the bottom surface 5c of the inner case 5.
The upper surface of the pot 4 is pressed against the bottom surface portion 8c of the pot 8.

An inwardly curved flange 15a is formed at the upper end of the guide tube 15, so that when the hot pot 8 is removed from the inner case 5, the flange 14a of the protective case 14 is connected to the guide tube. 1
It engages with the flange 15a of No. 5 to prevent it from coming off. 18 is a magnetic body made of a magnetic shunt material stuck to the inner bottom surface of the protective case 14.

Reference numeral 19 denotes a lever with a knob 19a attached to one end by integral molding or the like, and the middle part of this lever is rotatably supported via a pin 21 on a support arm 20 protruding from the lower surface of the inner case 5. A rising portion 19b provided at the other end is inserted into the guide cylinder 15 via the spring receiving plate 16, and a permanent magnet 22 is fixed to the upper end of the rising portion 19b.

A knob 19a attached to the lever 19 projects outward from a hole 23a of an operation panel 23 provided on the side surface of the outer case 1, and the lever 19 is always held at the arrow a by a torsion coil spring 24. biased in the direction. 25 is a microswitch attached to the outer case 1 via a support plate 25a, and when the permanent magnet 22 is attracted to the magnetic body 18 by pressing down the lever 19, the microswitch 25 is closed. It is becoming more and more common.

Reference numeral 26 denotes an automatic return type second thermoswitch using, for example, a bimetal as a heat-sensitive member. It is fixed to the lower end of the plate portion 27.

The sheathed heater 9 is connected to the micro switch 25 of the first thermoswitch 13 and the second thermoswitch 26.
It is connected to the power supply via the power supply in series (see Figure 2).
Further, the upper limit temperature T1 of the first thermoswitch 13 is set higher than the upper limit temperature T2 of the second thermoswitch 26 by a predetermined temperature. Reference numeral 28 denotes an outer lid made of, for example, plastic, which is rotatably supported via a pin 30 on a hinge member 29 fixed to the upper end of the outer case 1, and has a handle portion 31 integrally formed on the upper surface for carrying. There is.

32 is an inner cover, which is connected to the outer cover 28 via a heat insulating material 33.
is fixed to the inner surface of the

An engagement member 34 is located on the opposite side of the hinge member 29 and is fixed to the upper end of the outer case 1, and this engages with an engagement portion (not shown) provided on the handle portion 31 when the outer lid 28 is closed. together to hold the outer lid 28 in a closed state,
The engagement can be released by a push button 35.

Reference numeral 36 denotes an inner lid that is engaged and supported by an engaging portion 32a provided on the lower surface of the inner cover 32 via a supporting convex portion 37, and this is in pressure contact with the flange portion 8a of the pot 8 when the outer lid 28 is closed. It's summery.

Reference numeral 38 denotes a steam vent tube provided on the inner cover 36, which is inserted into an insertion hole 39 provided on the outer cover 28, and a spherical body 40 is disposed therein as a valve body.

Note that 41 and 42 are pilot lamps attached to the operation panel 23. Next, the operation of this embodiment configured as above will be explained.

Fill the pot 8 with washed rice and water necessary for cooking the rice, place the flange portion 8a on the flange portion 5a, store the pot 8 in the inner case 5, and close the outer lid 28. , the inner lid 36 is brought into pressure contact with the flange portion 8a of the pot 8, and the pot 8 is closed.
occlude. Next, by pushing up the knob 19a, the first
When the lever 19 of the thermo switch 13 is rotated in the opposite direction of the arrow a to cause the permanent magnet 22 to be attracted to the magnetic body 18, the micro switch 25 is closed and the temperature of the heat transfer plate portion 27 is changed to the second thermo switch 13. Since the thermo switch 26 is closed at a temperature lower than the lower limit set temperature T3 of the switch 26,
The sheathed heater 9 is energized via the microswitch 25 of the first thermoswitch 13 and the second thermoswitch 26, and generates heat. The heat of the sheathed heater 9 is transferred to the pot 8 through an air layer in the space formed between the inner case 5 of the pot 8 and the inner case 5 of the pot 8.
The heat is transferred to the inner case 5, and the heat transferred to the inner case 5 is transferred from the side surface 5b to the side surface 8b of the pot 8, which is opposed to the pot 8 with a small distance therebetween. In the early stages of rice cooking, the heat applied from the sheathed heater 9 to the outer periphery of the pot 8 facing it causes local convection in the water in the pot 8 along the side surface 8b, and as described above. Since heat is sufficiently transferred from the side surface 5b of the inner case 5 to the side surface 8b of the pot 8,
Heat is transferred well to the rice in the upper part, and as the water level in the pot 8 decreases as rice cooking progresses, the rice in the upper part acts as a so-called heat insulating layer, and the temperature of the rice in the lower part gradually rises. Immediately, the rice in the hot pot 8 is cooked from the top to the bottom, and the rice can be cooked evenly. When the water in the pot 8 begins to boil at the end of the rice cooking stage, the temperature of the bottom 8c of the pot 8 reaches 100.
When the temperature in the pot 8 reaches a stable state and then all the water in the pot 8 is absorbed by the rice and dries up, the temperature in the pot 8 begins to rise rapidly. On the other hand, the temperature t1 of the magnetic body 18 serving as the sensing portion of the first thermoswitch 13 and the temperature T2 of the lower end portion of the heat transfer plate portion 27 acting as the sensing portion of the second thermoswitch 26 are determined by radiation from the sheathed heater 9. Because of the influence of

That is, since the temperature at the bottom of the pot 8 rises relatively rapidly immediately after the start of rice cooking, the temperature at the lower end of the transmission plate 27 increases compared to the temperature at the protective case 14 due to the difference in the transmission distance from the sheathed heater 9. Although the temperature is delayed, heating by the sheathed heater 9 continues, and the temperature of the bottom portion 8c of the pot 8 increases slowly, so the difference between the temperatures t1 and T2 gradually decreases to the same temperature. After that, as mentioned above, while the temperature inside the pot 8 is in a boiling state, the temperature t1 and t become stable, and when the temperature of the pot 8 suddenly rises due to drying up, the temperature t1
And T2 also begins to rise rapidly. In this case as well, the temperature T2 rises later than the temperature tl, similarly to immediately after the start of rice cooking. When the temperature t1 reaches the upper limit setting temperature T2 of the second thermoswitch 26, the second thermoswitch 26 is opened and the sheathed heater 9 is cut off, but the temperatures u and T2 are then changed due to residual heat. The temperature rises slightly and then slowly decreases. During power outage of the sheathed heater 9, the temperature u is close to the pot 8, so the stored thermal energy is given to the pot 8 and the rice, and the temperature decreases slowly.
Since the temperature Q is close to the outside air and the heat dissipated from the electric heating plate part 27 is large, the rate of decrease is faster than that of the temperatures, and the temperature u<5.
A relatively large temperature difference occurs during t2. Then, after a predetermined time m1 has elapsed after the insulation of the sheathed heater 9, the temperature reaches T7! b
(When the lower limit set temperature T3 of the second thermoswitch 26 is reached, the sheathed heater 9 is energized again and the temperature u and T27 are reached.
However, as mentioned above, the temperature t1 rises quickly due to the difference in the transmission distance, and the temperature t1 rises quickly due to the difference in the transmission distance.
Since the temperature difference between the temperatures t1 and T2 when the power is cut off is added, after a predetermined period of time has passed after the re-energization of the sheathed heater 9, the temperature t1 reaches the upper limit of the first thermoswitch 13 before the temperature t1 reaches T2. When the set temperature T1 is reached, the magnetic body 18 of the first thermoswitch 13 reaches its magnetic transformation point, and the attraction force acting between it and the permanent magnet 22 is significantly reduced, so that the lever 19 is activated by the torsion coil spring 24. It is rotated back in the opposite direction of the arrow a by the spring force, the microswitch 25 is opened, and the sheathed heater 9 is cut off. After this, the temperature t1 of the pot 8 rises slightly above T1 as described above, and then gradually falls, and when a predetermined time j has elapsed after the second power cut of the sheathed heater 9, the temperature u falls to 100'C. . Therefore, during the time m1+M2+M3, the temperature of the bottom surface 8c of the pot 8 is maintained at 100 DEG C. or higher, the temperature of the rice in the pot 8 is also maintained at 100' C or higher, and the rice is uniformly mixed. In other words, if the temperatures of Tl, T2, and T3 are set so that the total time of m1+M2+M3 is one or more times,
The rice in pot 8 is evenly distributed and cooked very well. According to this embodiment, when all of the water in the pot 8 is absorbed by the rice and the rice is cooked (dry-up), the first thermoswitch 13 of the manual return type switches to the upper limit set temperature FV.
1, the automatic return type second thermoswitch 26 reaches the upper limit setting temperature T2 and turns off the sheathed heater 9, and after a predetermined period of time (m1) has elapsed, the second thermoswitch 26 When the lower limit set temperature T3 is reached, the sheath heat
Since the heater 9 is reenergized to further heat the pot 8 for a predetermined time (M2), compared to a conventional structure in which the electric heater is cut off when the rice reaches the completion (dry-up) state, the pot The rice in No. 8 is kept at a high temperature (above 10° C.) suitable for shading for at least an amount of time (m1+M2).

In other words, with the conventional structure, the uneven time tends to be insufficient when the ambient temperature is low, such as in winter, but in this embodiment, as described above, the uneven time is shorter than the conventional structure by at least (m1 + M2). Since it can be made for a long time, it is possible to ensure sufficient drying time even when the ambient temperature is low, such as in winter. Further, since the cooking time can be extended without making the pot 8 thicker than that of the conventional structure or covering it with a heat insulating material, the structure can be manufactured at low cost without complicating the structure. and,
Since the power to the sheathed heater 9 is temporarily turned off after the rice reaches a state where cooking is completed, the temperature of the bottom surface 8c of the pot 8 does not become extremely high, and the rice in the pot 8 does not burn. It can be prevented as much as possible. Incidentally, if the temperature difference between the upper limit set temperature Tl and the lower limit set temperature T2 of the second thermoswitch 26 is increased, the time (m1+M2) can be lengthened, and the uneven time can be lengthened.

Also, while increasing the set temperature T1 of the first thermoswitch 13, T2 and T3 of the second thermoswitch 2-6 are increased.
By reducing the temperature difference between the two, the sheathed heater 9 can be turned on and off several times after the rice has finished cooking (drying up). Can be maintained at a suitable high temperature (above 30°F),
In this case, when the first thermoswitch 13 returns to normal, the rice is considered to be finished and the rice can be eaten immediately. Further, in the above embodiment, the sheathed heater 9 is applied to a rice cooker in which the sheathed heater 9 is installed in the closed space formed between the pot 8 and the inner case 5. It can also be applied to rice cookers in which a sheathed heater is cast inside and the pot is placed on a hot plate.

In addition to rice cookers, the present invention can be widely applied to boilers that require uneven heating, and can also be applied to boilers with various heating methods. A second thermoswitch is provided to directly detect the temperature at the bottom of the pot, and a second thermoswitch is separated from the pot via a heat transfer body of a predetermined length to detect the temperature at the bottom of the pot. The temperature of the first thermoswitch may be set higher than the upper limit setting temperature of the second thermoswitch.

It goes without saying that the first thermoswitch 13 is not limited to the magnetic type as in the above embodiment, but may also be a bimetallic type. As explained above, the present invention can provide a simple and inexpensive boiler that can maintain cooked food at a high temperature suitable for uneven cooking for a long time.

[Brief explanation of drawings]

The drawings show an embodiment in which the present invention is applied to a heat-retaining rice cooker.
In Figure 3, the vertical axis shows temperature t (℃) and the horizontal axis shows time m (minutes).
FIG. In the drawings, 1 is an outer case, 5 is an inner case, 8 is a pot, 9 is a sheathed heater, 13 is a first thermoswitch, 25 is a microswitch, 26 is a second thermoswitch, and 27 is a heat exchanger plate ( heat transfer body).

Claims (1)

[Claims] 1. A pot for storing food to be cooked, a heater for heating the pot, and a first manual return type heater connected in series with the heater to directly detect the temperature at the bottom of the pot. a thermoswitch; and an automatic return type second thermoswitch connected in series with the first thermoswitch and provided to indirectly detect the temperature at the bottom of the pot via a heat transfer member of a predetermined length. 1. A boiler comprising a thermoswitch, wherein the upper limit temperature setting of the first thermoswitch is set higher than the upper limit setting temperature of the second thermoswitch.