JPH0728804B2 - Electric rice cooker - Google Patents

Description

TECHNICAL FIELD The present invention relates to improvement of a safety mechanism for preventing overheating in an electric rice cooker.

[Prior Art] In an electric rice cooker normally used at home, a measure for preventing overheating of the rice cooker is taken as one of the safety mechanisms.

FIG. 3 is a partial cross-sectional view of a conventional electric rice cooker, in which 1 is an inner hook, 2 is an outer hook, 3 is a rice cooking heater, 4 is a heat shield plate, 5 is a temperature fuse, and 6 is a fuse attachment. A plate, 7 is a fuse fitting, 8 is a heat-retaining heater, and 9 is a timer. Although not shown, a printed circuit board, a code reel, etc., which is connected to the timer 9 and a power cord and has electronic components mounted thereon, is housed in the space inside the bottom of the rice cooker including below the fuse mounting plate 6. Then, the bottom plate of the bottom of the rice cooker is removed, and the electric inspection and adjustment of the printed circuit board and the like are performed.

In an electric rice cooker, as shown in the figure, a 280w ring-shaped rice-cooking heater 3 is disposed on the upper surface of the bottom of an outer kettle to heat the inner kettle 1 from the bottom, and a 12w heat-insulating heater 8 It is arranged in a ring shape on the outer peripheral portion of the outer kettle and is configured to heat the inner kettle 1 from the side surface.

When using the above rice cooker, put a certain amount of rice and water in the inner kettle 1 and set the rising time by the timer 9, the rice cooking heater 3 will be turned on at the predetermined time, and Gama 1
The rice inside is heated to start cooking rice. When the rice cooks up and there is no more water to evaporate in the inner kettle 1, the temperature of the rice rises sharply, so a temperature sensor (not shown) arranged at the bottom of the inner kettle 1 operates and the rice cooking heater. When 3 is turned off, the heat-retaining heater 8 is turned on, that is, the rice is cooked and the heat is maintained.

By the way, when the temperature sensor does not function or there is other trouble, the rice cooking heater 3 does not turn off even if the rice is cooked, and the heater 3 continues to be energized, that is, the so-called continuous energization state. There is. Since there is water in the inner kettle 1 during the cooking time until the rice is cooked,
The temperature of the inner kettle 1 does not rise above 100 ℃ and does not rise so much, but since the water inside the inner kettle 1 has disappeared after the rice has been cooked, the latent heat of vaporization of water is not required.
The temperature of the rice and inner kettle 1 rises rapidly.

In addition, the temperature of the inner kettle 1 is 100 ° C during cooking time as described above.
The temperature difference between the rice cooking heater 3 and the heater 3 is large, and the amount of heat dissipated from the rice cooking heater 3 to the inner kettle 1 is large, and the rice cooking heater 3 maintains a temperature of about 700 ° C. However, when rice cooking is completed, the temperature of the inner kettle 1 rises sharply as described above, so that the temperature difference between the inner kettle 1 and the rice cooking heater 3 becomes small. As a result, the amount of heat radiated from the heater 3 to the inner kettle 1 decreases, and the temperature of the rice cooking heater 3 rises above 700 ° C. Therefore, the temperature inside the rice cooker may rise, which may burn parts of the rice cooker or, in the worst case, cause a fire.

In order to avoid such a danger, a temperature fuse 5 is arranged in the bottom of the outer kettle 2 in the rice cooker. When the temperature inside the rice cooker rises above a predetermined temperature, the temperature fuse 5 is activated to operate the rice cooker 3 Is configured to be turned off.

FIG. 4 is a sectional view of the thermal fuse 5. In the figure, 5a is a fuse shell made of a conductive material, 5b is a pellet made of an insulating and heat-soluble material, and 5c is a conductive material. A partition wall, 5d is a spring, 5e is an insulating part, 5f and 5g are cords, and 5h attached to the tip of the cord 5g is a conductive cord tip metal object. A slit is formed on the wall surface of the partition wall 5c, and the pellet 5b cannot pass through the slit in a pellet shape, but can pass through the slit when melted and liquefied. As shown in the figure, the thermal fuse 5 accommodates the pellet 5b in the front part of its outer shell 5a, and the pellet 5b is pressed by a spring 5d via a partition wall 5c. Further, in this state, the tip of the cord tip metal piece 5h is in contact with the partition wall 5c.

When the thermal fuse 5 configured in this way is placed in the circuit connecting the power supply and the rice cooking heater 3, the current normally flows from the cord 5f to the cord 5g through the fuse shell 5a, the partition wall 5c, and the tip metal 5h. , Energize the heater 3. However, the rice cooker overheats due to the continuous energization, etc., the temperature around the temperature fuse 5 rises, and the pellet 5b is heated to a predetermined temperature of 18
When it reaches 8 ° C, the pellet 5b melts and becomes liquid, and the partition wall 5
Since it comes to pass through the slit of c, the partition wall 5c pressed by the spring 5d moves to the left in the drawing. As a result partition
5c and cord tip hardware 5h are separated, cord 5f and cord 5g
Is cut off, so that the rice cooking heater 3 is turned off.

As shown in FIG. 5, the thermal fuse 5 is arranged directly below the rice cooking heater and on the bottom rear surface of the outer kettle 2. Fifth
The figure is a detailed mounting view of the thermal fuse 5. In the figure, 5 is a thermal fuse, 6 is a fuse mounting plate, 7 is a fuse mounting metal fitting, 10 is an insulating tube, and 11 is a protective tape.

[Problems to be Solved by the Invention] In the conventional rice cooker, the temperature fuse 5 is used.
Is covered with an insulating tube 10 and further wrapped with a protective tape 11. The reason why the protective tape 11 is wrapped is to prevent the insulating tube 10 from being broken and short-circuited by the edge of the mounting member 7.

However, since the temperature fuse is double-coated in this way, the heat conduction from the rice cooking heater 3 to the temperature fuse 5 is poor, and it takes time to melt the fuse 5 in the case of the above continuous energization. The plastic part of the above may cause damage such as heat melting, which has been a problem for some time.

The present invention has been made to solve the above problems of the conventional rice cooker, and an object of the present invention is to provide an electric rice cooker in which the thermal fuse is quickly melted in the case of the continuous energization.

[Means for Solving the Problems] In the electric rice cooker according to the present invention, an outer pot having an arcuate contact portion protruding toward the inner bottom surface, and an inner pot detachably accommodated in the outer pot And a heater for cooking rice, which is provided in a gap between the inner bottom portion of the outer pot and the outer bottom portion of the inner pot to partially contact the contact portion of the outer pot and heats the inner pot from the bottom, and an insulating tube. A thermal fuse surrounded by a coated cylindrical conductive shell to prevent overheating of the heater temperature;
A fuse mounting plate fixed to a fuse mounting plate provided on the outer bottom of the outer pot by providing a concave mounting part concentric with the outer shape of the thermal fuse at a free end, and the mounting part of the fuse mounting bracket. An electric rice cooker was constructed in which a protective tape was attached to and the temperature fuse was elastically pressed against the contact portion of the outer pot by the attaching portion.

[Operation] Since the overheat prevention device is brought into contact with the outer pot in the vicinity of the heater, if the temperature of the rice cooking heater rises after completion of rice cooking, the rice cooker operates in a short time and the electric circuit of the rice cooker is cut off.

Further, since the overheat prevention device is provided in the concave portion of the outer pot that contacts the heater, it operates faster and shuts off the electric path of the rice cooker.

Further, since the thermal fuse is covered only by the insulating tube, the heat conduction from the rice cooking heater to the thermal fuse is much better in the case of continuous energization, as compared with the conventional one. Therefore, the thermal fuse is blown faster during continuous energization as compared with the conventional rice cooker, so that burnout of parts of the rice cooker is avoided.

Since the protective tape is wrapped around the fuse fitting, damage to the insulation tube of the thermal fuse due to the edge of the fitting is sufficiently prevented.

[Embodiment of the Invention] FIG. 1 is a cross-sectional view of an electric rice cooker showing an embodiment of the present invention, in which 1 to 9 are the same as or equivalent to a conventional rice cooker.

As shown in the figure, a concave portion 10 was formed on the bottom rear surface of the rice cooker 2 just below the rice cooking heater 3, and the thermal fuse 5 was arranged in this concave portion.

Since the temperature fuse 5 is disposed close to the rice-cooking heater 3, when the temperature of the heater 3 rises as described above after the rice-cooking is finished, the temperature fuse 5 rises in temperature in a short time and melts down. , The current of the fuse 3 is cut off. As a result, the rise in temperature of the rice cooker is suppressed and burning of parts due to overheating is avoided. It should be noted that the time until the thermal fuse 5 is cut off after the completion of rice cooking is 15 minutes in the conventional rice cooker, but it is 10 minutes in the embodiment of the present invention.

FIG. 2 is a detailed view of a thermal fuse mounting portion showing an embodiment of the present invention.

As shown in the figure, when attaching the thermal fuse 5 to the bottom rear surface of the outer casing 2 of the rice cooker, only the insulating tube 10 is covered with the thermal fuse, and the thermal fuse is loaded on the mounting bracket 7 wrapped with the protective tape 11. I put it on.

Since the thermal fuse 5 is covered only with the insulating tube 10, the heat conduction from the rice cooking heater 3 to the thermal fuse 5 is improved during continuous energization, and the thermal fuse 5 melts faster.

[Advantages of the Invention] The present invention has an outer pot having an arcuate contact portion protruding toward the inner bottom surface, an inner pot detachably accommodated in the outer pot, and a part of the contact portion of the outer pot. A rice cooking heater which is provided in a gap between the inner bottom portion of the outer pot and the outer bottom portion of the inner pot to heat the inner pot from the bottom surface, and a cylindrical conductive shell covered with an insulating tube. A thermal fuse that is surrounded and prevents the temperature of the heater from rising too much, and a concave mounting portion that is concentric with the outer contour of the thermal fuse is provided at the free end of the fuse mounting plate that is provided at the outer bottom portion of the outer pot. An electric rice cooker comprising a fixed fuse mounting metal fitting, a protective tape being mounted on the mounting portion of the fuse mounting metal fitting, and the thermal fuse being elastically pressed against the contact portion of the outer pot by the mounting portion. did.

As a result, since the thermal fuse is wrapped in the concentric arc portion of the outer shell, the insulating tube and the outer pot and is in surface contact, the thermal coupling with the rice cooking heater brought into contact with the contact portion becomes close and heat is not transferred. Transmission is reliable and quick. Further, since the temperature fuse is sandwiched between the recesses of the outer pot and the fuse mounting metal via the protective tape, it can be safely mounted while being positioned. In addition, the protective tape is also wrapped around the back side of the fuse mounting bracket mounting area, so the temperature fuse and cord connection area is protected from external force applied by tools such as when checking the printed circuit board in the bottom of the rice cooker. It can also be protected electrically and electrically.

Therefore, according to the present invention, the assembling is easy and there is no failure,
The thermal conduction to the thermal fuse is rapid, and the thermal fuse is blown quickly in the continuous energized state, and the occurrence of accidental burnout of parts due to overheating is greatly reduced.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an electric rice cooker showing an embodiment of the present invention, FIG. 2 is a detailed view of mounting a temperature fuse of the electric rice cooker showing an embodiment of the present invention, and FIG. 3 is a conventional electric rice cooker. FIG. 4 is a partial sectional view of the rice cooker, FIG. 4 is a sectional view of the thermal fuse, and FIG. 5 is a detailed view of mounting the conventional thermal fuse. In the figure, 3 is a rice cooking heater, 5 is a thermal fuse, 10 is an insulating tube, and 11 is a protective tape. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Oshima, 1728 Omaeda, Omaeda, Hanazono-cho, Saitama Prefecture 1 Mitsubishi Electric Home Equipment Co., Ltd. (72) Inventor Tomoaki Okuse 1728, Omaeda, Hanazono-cho, Osato-gun, Saitama Prefecture Mitsubishi Electric Home Equipment Co., Ltd. (72) Inventor Yoshitaka Kawamura 1728 Omaeda, Omaeda, Hanazono-cho, Ozato-gun, Saitama 1 Mitsubishi Electric Home Equipment Co., Ltd. (56) Reference JP-A-2-203817 (JP, A) Kai 61-98221 (JP, A) Actual flat 2-90726 (JP, U) Actual 55-53012 (JP, U)

Claims (1)

[Claims] 1. An outer pot having an arcuate contact portion protruding toward the inner bottom surface, and an inner pot detachably accommodated in the outer pot.
A rice-cooking heater that partially contacts the contact portion of the outer pot and is provided in a gap between the inner bottom portion of the outer pot and the outer bottom portion of the inner pot to heat the inner pot from the bottom surface, and is covered with an insulating tube. A thermal fuse that is surrounded by a cylindrical conductive outer shell to prevent the temperature of the heater from rising excessively, and a concave mounting portion that is concentric with the outer shell of the thermal fuse is provided at the free end of the outer pot. A fuse mounting metal fitting fixed to a fuse mounting portion provided on the bottom is provided, and a protective tape is attached to the mounting portion of the fuse mounting metal fitting to elastically press the temperature fuse to the contact portion of the outer pot by the mounting portion. An electric rice cooker characterized by being installed.