JPH0734395B2 - Overtemperature prevention device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature overheating device that can be used in a high-frequency heating device such as a microwave oven.

2. Description of the Related Art Generally, as shown in FIG. 6, a high-frequency heating device is provided with an overheat prevention device for abnormal heating protection of the magnetron 6 and combustion detection / prevention of a heated object in a heating chamber. A bimetal type temperature switch 7 is used as the overheat prevention device.

The problem to be solved by the invention is that such a temperature switch 7 is provided with an operating temperature and a return temperature of the temperature switch 7 due to its configuration, and most of the temperature switches 7 are of an automatic return type. Has been adopted. Therefore, even if the temperature switch 7 once detects an abnormal temperature, the contact opens and the operation of the device is stopped, when the temperature returns to the return temperature, the contact closes again and the device restarts. However, there is a problem in that this is repeated many times and the final safety cannot be ensured. For this reason, conventionally, the position on the electric circuit of this overheat prevention device is defined, a double safety circuit is formed in conjunction with another switch, and the reset temperature of the temperature switch 7 is set to 0. Although it was necessary to set the temperature to ℃ or less and not recover from common sense, there was a problem that its accuracy and reliable safety were not guaranteed.

The present invention solves such a conventional problem and detects and prevents abnormal heating of the magnetron 6 and combustion in the heating chamber with a simple structure, and has an excellent temperature performance without repeatability. A rise prevention device is provided.

Means for Solving the Problems The overheat prevention device of the present invention is formed by a combination of a heat transfer part that transfers heat of a detected part and a current interrupting device.

The overheat prevention device of the present invention provides the current interrupt device with the heat of the detected part by the heat transfer part that transfers the heat of the detected part, and as a result, the ambient temperature of the current interrupt device rises and the current interrupt is interrupted. The heat dissipation effect of the device is reduced, and the self-heat generation causes the shutdown function to stop the equipment. In addition, it also functions to prevent overheating.

As described above, the function of the current interrupting device makes it possible to stop the function of the entire device and to stop the function forever unless it is reset again.

Embodiments An overheat prevention device that employs a current breaker 8 as a current interruption device according to an embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the current breaker 8 includes a breaker body 1 made of an insulator and a body 1
Inside, a bimetal 2 having a current characteristic as shown in FIG. 4 is provided, and contacts 3a and 3b forming a switching circuit by the bimetal 2 and the connection terminals 4a and 4b are provided. Further, a lid 5 made of a good heat transfer material (for example, a metal material) is provided, and a closed space for covering the bimetal 2 is formed with the main body 1. The other end of the lid 5 is fixed to the magnetron of the detected part or the wall of the heating chamber,
It also has the function of heat transfer. By doing so, each heat is transmitted to the magnetron 6 and the lid 5 fixed to the wall surface of the heating chamber as shown in FIGS. 2 and 3. When abnormal heat is generated in the above portion, the temperature of the space inside the breaker body 1 rises due to the heat transfer action of the lid 5.

If the description is added in FIG. 4, the characteristic of the current breaker 8 shown in FIG. 5 allows the point at the time of current interruption to be point A, the current value at that time is Ia, and the bimetal temperature is Ta.
The current value (I) and the bimetal temperature (T) in the normally used current region are set to values lower than Ia and Ta.

Now, the heat transferred by the lid 5 pushes up the atmospheric temperature in the main body 1 by ΔT. As is apparent from FIG. 4, the current characteristic of the bimetal 2 has a current characteristic including the increase ΔT in the ambient temperature, and the current interruption point A acts in the direction of decreasing the interruption current and becomes the point A ′. As a result, even at the current value I in the normal use current region, the current breaker 8 is activated by the temperature-sensing phenomenon, the contacts 3a and 3b are opened, and the equipment is stopped. Further, as a matter of course, even when an overcurrent flows, the function as the current breaker 8 is also achieved.

Therefore, by operating the current breaker 8, the device can be kept in the stopped state until it is reset, and it is possible to prevent the repeated operation as in the conventional case, and to provide the current cutoff function as in this embodiment. It is possible to integrate the overheat prevention function into a dual function, and improve productivity by reducing the number of parts.

Regarding the lid 5 which is a heat transfer plate, in order to further increase the temperature sensitivity, an aluminum-based material having a high heat transfer property is used, or both the upper and lower lids of the main body 1 are heat transfer plates. It is also possible to press the entire lid 5 against the heat sensitive portion.

Furthermore, by painting (coloring) the inside of the lid 5 with black, the heat dissipation coefficient of the conductive heat can be increased, and the conductive heat can be effectively utilized to improve the performance, and the outer surface can be mirror-finished. Thus, it is possible to prevent heat radiation to the outside and improve the performance.

As another embodiment of the present invention, the same effect can be obtained by using a current breaker and using the current fuse 10 instead of the current breaker 8. Further, an inversion button for the bimetal 2 is provided, and even if the bimetal 2 operates, the setting can be performed again later, so that it can withstand repeated use.

Effects of the Invention As described above, in the overheat prevention device of the present invention, a part of the main body of the current interrupting device having a function of interrupting overcurrent is made of a good heat conductive material and fixed to the heat sensitive part. The heat of the heat-sensitive part is transmitted to the current interrupting device via the above-mentioned conductive material to operate the current interrupting device. Therefore, after the overheat prevention device operates, the current interrupting device automatically recovers or has a double circuit. No structure is provided, the reliability of the overheat protection device is secured, and the current cutoff device and the overheat protection device are integrated to reduce the number of parts, and also in terms of cost. , Will help improve productivity. In particular, according to the present invention, since the current interruption function and the overheat prevention function are unified, even when the overheat prevention function works,
Since the current interruption function also works, high reliability can be obtained, which is extremely advantageous in practical use.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an overheat prevention device according to an embodiment of the present invention, FIG. 2 is a perspective view showing the same mounting state, FIG. 3 is a front view thereof, FIG. 4 is a characteristic view thereof, and FIG. FIG. 5 is a circuit diagram in which the same device is connected to a microwave oven, and FIG. 6 is a circuit diagram of a conventional example. 1 ... Main body, 2 ... Bimetal, 5 ... Lid.

Claims (3)

[Claims] 1. A current interrupting device having an overcurrent interrupting characteristic in which a current-sensing bimetal and a contact are arranged and the contact is opened by heat generated by an overcurrent flowing through the bimetal, and a space for enclosing and sealing the current interrupting device. A body having an electrically insulating property that constitutes this space and holds the current interrupt device,
It has a member that constitutes a space to be sealed together with this main body,
An overheat prevention device also having an overcurrent prevention current interruption function, wherein the member is made of a good heat conductive material and at least one end of the good heat conductor is fixed to a heat generating portion to be detected. 2. A device for preventing excessive temperature rise according to claim 1, wherein an inner surface of the good heat conductor on the side provided with the current interruption device is heat-dissipated. 3. The overheat prevention device according to claim 1, wherein the outer surface of the good heat conductor is mirror-finished.