JPH0341441Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a positive characteristic thermistor with a temperature fuse function.

[Conventional technology]

A positive temperature coefficient thermistor has, for example, the characteristics shown in FIG. 3, and is widely used, for example, as a heating element or for controlling an electric circuit.

However, positive temperature coefficient thermistors are semiconductor devices, and under special operating conditions, such as incorrect use of voltage, use in a reducing atmosphere, use in a humid atmosphere, etc., thermal breakdown may occur, although very rarely. There is a risk of it happening.

Therefore, assuming such a case, for example, the fourth
As shown in the figure, a current fuse 6 is normally used to open the circuit due to the large current that flows when the PTC thermistor 2 is destroyed by heat. 8 is a power source.

[Problem that the invention attempts to solve]

However, when the positive temperature coefficient thermistor 2 is used to control the load 10, as shown in FIG. 5, for example,
Even if the positive temperature coefficient thermistor 2 is destroyed and becomes short-circuited, the circuit current is suppressed by the load 10, so the current that is sufficient to blow the current fuse 6 does not flow through the circuit, and therefore the positive temperature coefficient thermistor 2 becomes abnormal. If the situation continues, the abnormal current continues to flow through the load 10 and may develop into a thermal effect on the outside.

Therefore, the object of this invention is to provide a positive temperature coefficient thermistor that can prevent the above situation.

[Means for solving problems]

The PTC thermistor of this invention has a PTC thermistor element having electrodes on both main surfaces housed in a case, and two terminals connected to both electrodes are pulled out of the case. A contact part that opens by its own elastic force is inserted in series in the middle of the case, and a fusing element that melts at a predetermined temperature is thermally coupled to a positive temperature coefficient thermistor element between this contact part and the case. It is characterized in that the contact portion is closed by inserting the contact point.

[Effect]

The PTC thermistor of this invention has a temperature fuse function, and since the contact portion is normally closed by the fusing element, it is possible to conduct electricity to the PTC thermistor element. On the other hand, if the temperature of the positive temperature coefficient thermistor element rises abnormally for some reason, the temperature of the fusing element in the same case exceeds a predetermined temperature and it melts, causing the contact part to act on its own elastic force. The circuit is opened and current to the positive temperature coefficient thermistor element is cut off.

〔Example〕

FIG. 1 is a sectional view showing a positive temperature coefficient thermistor with a temperature fuse function according to an embodiment of the invention. In this PTC thermistor 12, a disk-shaped PTC thermistor element 14 having electrodes 16a and 16b on both main surfaces is housed in a case 18 made of resin, for example, and two electrodes connected to the electrodes 16a and 16b, respectively, are housed in a case 18 made of resin, for example. Two terminals 20a and 20b are drawn out of the case 18. Terminals 20a, 20
b respectively have restraining parts 22a and 22b made of stainless steel or the like for elastically restraining and holding the positive temperature coefficient thermistor element 14, and drawer parts 24a and 24b connected thereto.

A contact portion 30 consisting of contacts 26 and 28 is inserted in series in the middle of the drawer portion 24b in the case 18 of one terminal, in this example the terminal 20b. This contact 26 is designed to separate from the contact 28 and open due to its own elastic force if there is no fusing element 30, which will be described later, or if it melts. And contact 26 and case 18
A fusing element 32 that melts at a predetermined temperature is inserted between the contact point 26 and the contact point 28, thereby closing the contact portion 30. The fusing element 32 is made of, for example, a low melting point metal, an organic fusing material, or the like.

The positive temperature coefficient thermistor 12 has a temperature fuse function, and the contact portion 30 is normally closed by the fusing element 32.
It is possible to supply current to the positive temperature coefficient thermistor element 14 via a and 20b.

On the other hand, due to some reason, the positive temperature coefficient thermistor element 1
4 becomes abnormal and its temperature rises abnormally due to thermal breakdown or the like, the fusing element 3 located in the same case 18 and in the vicinity of the positive temperature coefficient thermistor element 14
2 exceeds a predetermined temperature and melts, thereby causing the contact portion 30, more specifically, the contact portion 2
6 is opened by its own elastic force, and the current to the positive temperature coefficient thermistor element 14 is quickly cut off. Therefore, even if the positive temperature coefficient thermistor element 14 generates abnormal heat, the case 18 is prevented from being damaged or burned, and there is no thermal influence on the outside.
Accidents such as burnout of sets incorporating the positive temperature coefficient thermistor 12 can also be prevented.

Figure 2 shows the above positive temperature coefficient thermistor 12 as a load 10.
This shows an example of a circuit when connected to the PTC thermistor 12, and due to the above-mentioned temperature fuse function of the PTC thermistor 12, even if the circuit current is suppressed by the load 10 in an abnormal state of the PTC thermistor element 14. , unlike the conventional case, the circuit can be opened quickly and protected.

Typical examples of the load 10 include auxiliary coils for starting induction motors used in refrigerators, air conditioners, etc., and demagnetizing coils for color televisions and color displays.

It goes without saying that the way the PTC thermistor element 14 is held, the way the terminals are drawn out from it, the structure of the case 18, etc. are not necessarily limited to those in the above example.

[Effect of idea]

As described above, this invention has a temperature fuse function and can detect abnormal heat generation of the PTC thermistor element internally based on the temperature and quickly open the circuit. It is possible to prevent thermal effects from being exerted on the device.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a positive temperature coefficient thermistor with a temperature fuse function according to an embodiment of the invention. FIG. 2 is a diagram showing an example of a circuit using the positive temperature coefficient thermistor of FIG. 1. FIG. 3 is a diagram showing an example of resistance temperature characteristics of a positive temperature coefficient thermistor element. FIG. 4 and FIG. 5 are diagrams each showing an example of a circuit using a conventional positive temperature coefficient thermistor. 12... Positive temperature coefficient thermistor with temperature fuse function according to this invention, 14... Positive coefficient thermistor element, 16a, 16b... Electrode, 18... Case,
20a, 20b...terminal, 30...contact part, 3
2... Fusing element.

Claims (1)

[Scope of utility model registration request] A positive temperature coefficient thermistor element having electrodes on both main surfaces is housed in a case, and two terminals connected to both electrodes are pulled out of the case. A contact portion that opens due to the elastic force of A positive temperature coefficient thermistor with a temperature fuse function characterized by a closed circuit.