JPS642502Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Field of Use This invention relates to an overtemperature rise prevention device, and is particularly used in various household electric heating devices such as electric heaters, electric rice cookers, and electric irons.

BACKGROUND ART Temperature fuses have conventionally been used to prevent burnouts and fires caused by heating of electrical equipment. This temperature fuse may be one using a temperature-sensitive member made of a chemical substance that melts at a specific temperature, as disclosed in, for example, Japanese Utility Model Application No. 56-110545; There is one that uses a fusible alloy that melts at a specific temperature, as disclosed in . This type of temperature fuse is generally connected in series to an electrical device, and when the electrical device reaches a predetermined temperature or higher, the temperature-sensitive member or fusible alloy melts and interrupts the circuit.

Problems to be Solved by the Invention However, with the above configuration, it is not known that the temperature is rising abnormally until the temperature fuse is activated, and when the temperature fuse is activated, the circuit is cut off and the electrical equipment suddenly shuts down. This may lead to unexpected situations depending on the electrical equipment.

Means for solving the problems In order to solve the above problems, this invention
It includes at least two temperature fuses with different operating temperatures and at least two impedance means, the temperature fuse with a low operating temperature and a part of the impedance are connected in series, and the other impedance means is connected across the temperature fuse. ,
It is characterized in that a temperature fuse with a high operating temperature is connected in series with at least the other impedance means.

The temperature fuse may use the above-mentioned temperature-sensitive member or may use a fusible alloy. Further, as the impedance means, a resistor can be used for a DC circuit, and a resistor, a capacitor, an inductance, or a combination thereof can be used for an AC circuit.

Effect According to the above means, a predetermined current flows through only a part of the impedance under normal conditions, and when the ambient temperature reaches the operating temperature of the low operating temperature temperature fuse, this temperature fuse is activated and the two impedances are Although the current decreases as the impedance increases due to the series connection, the circuit is not interrupted and the current continues to flow. Therefore, it is only necessary to notice the abnormality in this state and restore the normal state. If the abnormality is not noticed, and in the case of an electrical equipment shot, etc., the high operating temperature fuse will eventually operate and completely cut off the circuit.

Embodiment An overtemperature rise prevention device according to an embodiment of this invention will be described below with reference to the drawings.

FIG. 1 shows a circuit diagram of the overtemperature rise prevention device 1. As shown in FIG. In the figure, F1 and F2 are temperature fuses whose operating temperatures are T1 and T2, respectively, and the relationship T1<T2, and the temperature fuse F1 whose operating temperature T1 is low is preferably made of a relatively inexpensive fusible alloy. The temperature fuse F2, which has a high operating temperature T2, preferably uses a relatively expensive but highly reliable temperature-sensitive member. R1 and R2 are resistances as an example of impedance means, and their respective resistance values are shown for convenience.
Let r1 and r2 be r1=r2=r. The temperature fuse F1 and the resistor R1 are connected in series, and a series circuit of the temperature fuse F2 and the resistor R2 is connected across the temperature fuse F1. 2 and 3 are terminals.

Next, the operation will be explained using FIG. 2. Now, the voltage between terminals 2 and 3 is constant at V, and R
Assume that 1 is the load. Then, since the resistor R2 is short-circuited by the temperature fuse F1 at room temperature, a current of I2=V/r flows through the path of terminal 2, temperature fuse F1, resistor R1, and terminal 3. When the ambient temperature reaches the operating temperature T1 of the temperature fuse F1, the temperature fuse F1 is activated and becomes open, so that a path from terminal 2 to temperature fuse F2 to resistor R2 to resistor R1 to terminal 3 is formed. A current of I1=V/2r flows. Therefore, in this state, the electrical equipment cannot operate normally, and the temperature fuse F1
It can be seen that it is working. Here, if an abnormality notification light bulb or the like is used as the resistor R2, not only will the operation of the electrical equipment be different from normal operation, but also the abnormality can be notified by lighting the light bulb. After investigating the cause of the activation of the temperature fuse F1 and eliminating the cause, a new temperature fuse F1 is connected and the electrical equipment is energized again. If temperature fuse F1 is left activated, the ambient temperature may rise further in the event of an electrical equipment shoot accident, and in such a case, the ambient temperature may When temperature T2 is reached, temperature fuse F2 is activated, opening the circuit and reducing the current to zero.

Note that the temperature fuse F1 may be connected in parallel to the resistor R1. However, in this case, the temperature fuse F
Since current flows through the temperature fuse F2 even in the normal state of the temperature fuse F2, the illustrated example is preferable.

FIG. 3 shows a circuit diagram of an overtemperature rise prevention device 4 according to another embodiment of this invention. This embodiment uses n temperature fuses F1, F2,...Fn-1, Fn, each with an operating temperature T1, T2,...Tn-
1, Tn is set as T1<T2<...<Tn-1<Tn. In addition, n resistors R1, R2,...,
Using Rn-1, Rn, the temperature fuse F1,...
...Connected in cascade with Fn. According to this embodiment, the current can be changed in multiple stages as shown in FIG. 4 depending on the operating states of the temperature fuses F1 to Fn.

Effects of the invention According to this invention, as described above, by using a plurality of temperature fuses and impedance means, the circuit is not suddenly cut off due to the operation of the temperature fuse, and abnormal operation is prevented. By going through the condition, you can investigate and eliminate the cause,
Unexpected situations caused by sudden stoppage of electrical equipment can be eliminated.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an overtemperature rise prevention device according to an embodiment of the invention, and FIG. 2 is a temperature vs. current characteristic diagram for explaining its operation. FIG. 3 is a circuit diagram of an overtemperature rise prevention device according to another embodiment of this invention.
The figure is a temperature vs. current characteristic diagram for explaining the operation. 2, 3...Terminal, F1~Fn...Temperature fuse,
R1 to Rn... Impedance means (resistance).

Claims (1)

[Claims for Utility Model Registration] The invention includes at least two temperature fuses with different operating temperatures and at least two impedance means, the temperature fuse with a low operating temperature and some of the impedance means are connected in series, and the temperature fuse An overtemperature rise prevention device characterized in that at least another impedance means is connected across the range, and a temperature fuse with a high operating temperature is connected in series with at least the other impedance means.