JP2775703B2 - High voltage fuse - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuse that automatically cuts off current when an abnormal current flows in an electric circuit and a resistor or the like is overloaded.

[Related Art] In recent years, a large-sized display formed by arranging a large number of fluorescent tubes vertically and horizontally has been installed in a baseball field or the like. Here, when the life of the fluorescent tube expires, the degree of vacuum in the tube decreases and an excessive current flows in the circuit. Therefore, in order to protect the circuit, when an abnormal current flows, the circuit is shut off by a breaker.

A conventional fuse resistor is disclosed in Japanese Utility Model Laid-Open No. 57-197605, which uses a low melting point solder to function as a fuse, and is disclosed in JP-A-55-48902. As described above, there is a type in which a fuse acting body is attached to the surface of a film resistor, and this portion is cut when an abnormal load is applied by the fuse acting body.

[Problems to be Solved by the Invention] In the above-mentioned conventional display, when the vacuum degree of even one fluorescent tube is gradually reduced and abnormal discharge occurs, the breaker is dropped due to the abnormal current and the entire display disappears. There was a problem. Moreover, once the screen disappears, it is extremely difficult to find out where the fluorescent tube has been cut, and much time has been spent replacing the fluorescent tube. Therefore, it is conceivable to attach a fuse resistor to each fluorescent tube. However, when the above-described conventional fuse resistor is used in such a fluorescent tube, the power value at which the fuse is blown varies widely, and the time until the blow is long. This is not practical because it does not protect the circuit. In particular, in the state where a high voltage is applied even if the conventional fuse action body is attached, the fuse leaks in a gap between the cut portions, and is used as the above-described fluorescent tube fuse used at a high voltage. Cannot be used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the related art, and provides a high-voltage fuse that functions accurately even at a predetermined power value, particularly at a low power value, and has a sufficient withstand voltage after being cut off. The purpose is to:

Means for Solving the Problems According to the present invention, a connecting member made of a shape memory alloy is formed from a memory shape to a shape that can be engaged, and a conductive member is engaged with a tension applied by a coil spring to the connecting member. This is a high-voltage fuse that holds and connects them between a pair of electrode members.

[Function] The high-voltage fuse of the present invention is formed from a memory shape by a connecting member of a shape memory alloy, and returns to an original shape when the connecting member reaches a predetermined temperature by heat due to an abnormal current or the like, and the engagement is released. As a result, the spring contracts and the circuit is surely cut off.

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

1 and 2 show a first embodiment of the present invention. The high-voltage fuse of this embodiment is a fuse resistor, and a fixed resistor 1 of a carbon-resin solid resistor is used. Used. Fixed resistor 1 that is a conductive member
Are bent into a U-shape and a U-shape, and the terminal 3 is engaged with a connecting piece 2 which is a ring-shaped shape memory alloy connecting member.

The connecting piece 2 is made of Ni-
A shape memory alloy such as a Ti alloy or a Ni-Ti-Co alloy that operates at a lower temperature, and is formed into a coil shape by forming to form this into a shape different from the memory shape, and it is cut for each ring. .

Here, when the fluorescent tube abnormally discharges, the temperature of the fixed resistor 1 becomes about 200 ° C., and the heat causes the connecting piece 2 to become about 100 ° C. Therefore, in this case, the so-called As point at which the martensite phase of the shape memory alloy starts to return to the parent phase is formed at 100 ° C., and the connecting piece 2 returns to the memory shape at 100 ° C. The connecting piece 2 is further engaged with the locking portion 6 at one end of the metal coil spring 5 and is in a state of being pulled by the terminal 3 and the coil spring 5.

The locking portion 7 at the other end of the coil spring is inserted into an elongated hole (not shown) on the bottom surface of the cap-shaped electrode member 8 formed in a U-shape, and the U-shaped tip is inserted into the small hole of the electrode member 8. doing.

Further, the terminal 4 of the fixed resistor 1 is inserted into a long hole (not shown) on the bottom surface of the other cap-shaped electrode member 8 in the same manner as described above, and the U-shaped tip is fitted into the small hole of the electrode member 8. . The outer side of the bottom surface of each electrode member 8 is covered with the terminal 4 and the locking portion 7 by soldering or welding to form a smooth surface. Here, the terminal 4 and the locking portion 7 may be formed in an L-shape instead of a U-shape, pass through the through hole of the electrode member 8, engage and solder, and then cut out a protruding portion.

The fixed resistor 1 and the coil spring 5 are inserted into a transparent cylindrical glass cover 11, and a pair of cap-shaped electrode members 8 are attached so as to cover both ends of the cover 11. Reference numeral 5 is inserted into the cover 11 in a state of being stretched with a constant tension.

The fuse resistor of this embodiment is generally composed of a fixed resistor 1
Functions as a resistor, and is attached, for example, to each fluorescent tube of a large screen display formed by arranging a large number of fluorescent tubes vertically and horizontally, or to every several fluorescent tubes.

On the other hand, if excessive power is applied to this fuse resistor,
The temperature of the fixed resistor 1 reaches about 200 ° C., and this heat is also transmitted to the connecting piece 2 to increase the temperature of the connecting piece 2. When the temperature of the shape memory alloy of the connecting piece 2 reaches 100 ° C., which is the As point, the connecting piece 2 starts to return to the linear shape of the memory shape, the engagement is released, the coil spring 5 contracts, and the circuit is interrupted. .

According to this embodiment, the connecting piece 2 becomes linear at the predetermined temperature accurately, and the engagement with the coil spring 5 is released, so that the circuit is reliably cut off.

Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same members as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the terminal 3 of the fixed resistor 1 is formed of a memory alloy.

First, a linear shape memory alloy wire is cut into a predetermined length and fixed to one end of the fixed resistor 1 by soldering, brazing or welding. Then, the distal end of the terminal 3 is bent into a U-shape to form an engagement portion, and the terminal 3 is engaged with the locking portion 6 of the coil spring 5 and attached.

When the temperature of the terminal 3 becomes equal to or higher than the predetermined temperature due to the abnormal current, the fuse resistor of this embodiment returns to the linear shape of the memory shape, disengages, the coil spring 5 contracts, and the circuit is cut off.

According to this embodiment, the connecting piece does not need to be specially provided, and the size of the component can be reduced.

Next, another example of a fuse using a shape memory alloy will be described with reference to FIGS. Here, the same members as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this example, a fixed resistor is not provided and only a fuse for high voltage is used, and a connecting piece 12 is used as a connecting member, and a coil spring 5 is formed of a shape memory alloy. The coil spring 5 has a memory shape in which the coil spring is contracted, and when the coil spring 5 is attached between the electrode members 8, it is stretched and attached. As for the mounting method, one locking portion 7 is directly mounted on the electrode member 8, and the other locking portion 6 is engaged with one end of the connecting piece 12. The other end of the connecting piece 12
It is fixed to the electrode member 8.

When the abnormal temperature causes the coil spring 5 to reach a predetermined temperature or higher, the coil spring 5 returns to the memorized shape, and the engagement with the connecting piece 12 is released. The engagement with the connecting piece 12 is released by the force of the coil spring 5 contracting to return the engaging portion of the connecting piece 12.

According to this embodiment, it can be used as a normal fuse that does not include a resistor. Here, the connecting piece 12 of this example is also formed of a shape memory alloy, so that the engaging portion 13 extends linearly at a predetermined temperature, and returns to the memory shape at the same temperature as the coil spring 5. You may be sure. This more reliably shuts off the circuit at the predetermined temperature. Further, the connecting piece 12 may be formed of a shape memory alloy, and the coil spring 5 may be formed of ordinary spring steel.

Further, in the above-described embodiment, the temperature at which the connecting member and the coil spring return to the memorized shape may be set lower, and the operation may be performed when the ambient temperature around the circuit becomes abnormal. In such a case, a through hole is appropriately formed in the glass tube, or an insulator or the like having good air permeability is used instead of the glass tube so as to be sensitive to the ambient temperature.

The shape of the shape memory alloy of the high-voltage fuse according to the present invention can be set as appropriate. A coil spring of the shape memory alloy is directly attached to the circuit board without using a cover, and the coil spring shrinks at a predetermined temperature to reduce the circuit shape. May be disconnected.

[Effects of the Invention] The high-voltage fuse of the present invention engages a connecting member made of a shape memory alloy in a state where tension is applied thereto, and when an excessive electric power is applied or an abnormal temperature is reached, the connecting member is used. Alternatively, the coil spring returns to the memory shape, the engagement is released, the coil spring contracts, and the circuit is reliably shut off even at a high voltage.

Moreover, since the shape memory alloy is used, the circuit operates reliably at the As point of the set reverse transformation start temperature, there is no variation in the operating temperature, and the circuit is reliably shut off under predetermined conditions.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment of a high-voltage fuse of the present invention, FIG. 2 is a cross-sectional view of the high-voltage fuse of this embodiment in a cut state, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a cross-sectional view of the high-voltage fuse of the example, FIG. 4 is a side view of the fixed resistor of the second embodiment, FIG. 5 is a cross-sectional view of the high-voltage fuse of the second embodiment cut off, and FIG. Is a cross-sectional view of another example of a high-voltage fuse using a shape memory alloy, and FIG. 7 is a cross-sectional view of the state in which the high-voltage fuse of FIG. 6 is cut. 1 ... fixed resistor, 2,12 ... connecting piece, 3,4 ... terminal, 5 ... coil spring, 8 ... electrode member,

Claims (1)

(57) [Claims] A coil spring is provided between a pair of electrode members,
A conductive member is arranged between the coil spring and the electrode member,
In a high-voltage fuse held between the electrode members in a state where the coil spring is stretched and held in a state where tension is applied to the conductive member, an engaging portion is formed by applying a forming process from a memory shape to a wire of a shape memory alloy. Is formed, and the connecting member, the conductive member and the coil spring are connected in series, and the tension by the coil spring is held between the pair of electrode members in a state where the tension is applied to the conductive member and the connecting member. A high-voltage fuse characterized by: