JPS5843163Y2 - thermal protector - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a thermal protector.

Generally, a thermal protector has a pair of open/close electrodes consisting of a fixed electrode and a movable electrode equipped with a thermally responsive element such as a bimetal. It cuts off current and is widely used as a safety device to prevent overheating in various electrical devices.

There are two types of thermal protectors: one is a self-recovery type that temporarily opens due to a rise in the surrounding temperature, and then, when the surrounding temperature drops after a while, the two electrodes come into contact again and flow current to the load, and the other is a self-resetting type that temporarily opens the main circuit. There is a manual return type, in which the main circuit does not close again even if the ambient temperature drops after it is opened, and the circuit is manually reclosed after inspection and countermeasures are taken.

In the latter case, conventionally, there is a structure in which a heating wire is connected in parallel to the opening/closing electrode.

In this case, even if the temperature of the device exceeds a certain level and the switching electrode is opened and the device itself cools down, the heat generated by the heating wire keeps the bimetal above the closing temperature and does not close the switching electrode.

The mechanism is such that the opening/closing electrode can only be closed once the heating wire is turned off.

However, in this case, the heating wire coil may be deformed due to vibration, or the electrodes may become conductive in the middle, resulting in loss of reliability as a thermal protector, and the structure is complicated, resulting in poor productivity. was.

The present invention aims to improve this drawback and provide a thermal protector with high vibration resistance, high reliability, and good productivity.

The present invention has a fixed electrode, a thermally responsive element that separates from the fixed electrode and becomes an open circuit when a predetermined temperature is reached, a movable electrode disposed opposite to the fixed electrode, and two holes. The present invention is characterized by a thermal protector comprising a positive temperature coefficient thermistor, and the fixed electrode and the movable electrode are inserted and connected to holes of the positive coefficient thermistor, respectively.

In the thermal protector of the present invention, after both electrodes are in an open circuit state at a predetermined temperature, the open circuit state is maintained by constant temperature heat generation of the positive temperature coefficient thermistor, and the closed circuit state can be returned only manually.

A positive temperature coefficient thermistor performs a constant-temperature heating operation in which when the temperature rises, the resistance increases and the amount of heat generated is suppressed to a small level, and when the temperature falls, the resistance decreases and the amount of heat generated increases.

Therefore, the safety of the thermal protector of the present invention is extremely high.

An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a positive temperature coefficient thermistor 1 with a minimum resistivity of 10 Ω and made of barium titanate as a main component has two holes 1a and 1b, and the distance between them is as shown in FIG. The distance l' is set to be approximately the same as the distance l between the open/close electrode leads of the electrode 2 and the fixed electrode 6. As shown in FIG. 3, a fixed contact 5 is provided at the tip of the fixed electrode 6, and a movable contact 4 is provided at the opposite position The lower end of the snap-action type thermally responsive element 3 provided with the glass bead 7 is connected to the movable electrode lead, and both electrodes are supported and fixed by the glass bead 7. A mount body in which a positive temperature coefficient thermistor 1 is inserted and fixed at an intermediate position is sealed in a glass tube 8 filled with an inert gas.

Further, FIG. 4 shows a configuration in which the movable electrode 2 and the fixed electrode 6 are supported and fixed by a positive temperature coefficient thermistor 1, and the positive coefficient thermistor also serves as a glass beat.

As an example, the opening operating temperature is 130°C, and the closing operating temperature is 90°C.
The thermal protector manufactured using the ℃ design is 1
The contacts became open at 30°C.

After that, the positive temperature coefficient thermistor 1 inserted and fixed in both electrode leads can maintain a constant temperature of 90°C or higher, which is the temperature at which the circuit is closed, so as long as voltage is applied between both electrodes, the contact will not open. The condition can be maintained.

Therefore, the contact can be returned to closed circuit only by opening the main switch, resulting in a manual return type structure for further improving the functional reliability for preventing burnout of electrical equipment.

In this way, by skillfully utilizing the characteristics of positive temperature coefficient thermistors,
Highly reliable and safer temperature control possible.

Furthermore, by using a positive temperature coefficient thermistor without using a heating wire or the like, and by inserting and connecting both electrodes through holes provided in the thermistor, it is possible to provide a thermal protector with high vibration resistance and high productivity. .

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a positive temperature coefficient thermistor, FIG. 2 is a side view of a switching electrode lead, and FIGS. 3 and 4 are side sectional views of a thermal protector in each embodiment of the present invention. 1... Positive characteristic thermistor, 2... Movable electrode, 3... Thermal response element, 6... Fixed electrode.

Claims (1)

[Scope of utility model registration request] A positive temperature coefficient thermistor having a fixed electrode, a thermally responsive element that separates from the fixed electrode and becomes an open circuit when a predetermined temperature is reached, a movable electrode disposed opposite to the fixed electrode, and two holes. A thermal protector, characterized in that the fixed electrode and the movable electrode are inserted and connected to holes of the positive temperature coefficient thermistor, respectively.