JPH0574309A - Circuit breaker - Google Patents

Abstract

PURPOSE:To miniaturize a circuit breaker and reduce a manufacturing cost by using a coil-like shape memory alloy having a transformation temperature higher than a room temperature for breaking a circuit. CONSTITUTION:In a switch, leaf springs 3, 4 with contact pieces 5, 6 attached in the center thereof are fixed to fixing bases 7, 8, respectively, and one end of a movable piece 2 is held between the springs 3, 4 by spring force. In this state, the movable piece 2 is brought into contact with the contact pieces 5, 6, and a circuit is closed. When an overcurrent is supplied to the circuit, heat is generated in a coil portion of a shape memory alloy 1. When a temperature of the alloy 1 reaches a transformation temperature, contracting force of the alloy 1 overcomes restraining force of the springs 3, 4 so that the alloy 1 is contracted and the movable piece 2 is separated from the contacts 5, 6, thus breaking the circuit. A lever 9 is rotated on a clamp 10, to be displaced. When the lever is returned to the original position, the end of the movable piece 2 enters between the contacts 5, 6, whereby the circuit is closed again. Consequently, a structure can be simplified functionally, and a breaker of a small size can be obtained at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit breaker for breaking a circuit when an overcurrent flows through the circuit.

[0002]

2. Description of the Related Art Conventionally, a general circuit breaker uses a bimetal, and when an overcurrent flows in the bimetal, the bimetal is heated and curvedly displaced in response to the overcurrent, and a spring hooked on the bimetal portion. There is a mechanical type in which the operating plate comes off and the lever falls to shut off the circuit.

On the other hand, as shown in FIG. 3, there is also an oil damper type circuit breaker. Cylinder 12 is plug 1
It is sealed by 3, and a plunger 14 is inserted in the cylinder, and the plunger is pressed in the direction opposite to the plug by a spring 15 placed on the plug side. The cylinder is filled with silicone oil. A solenoid coil 16 is wound around the outside of the cylinder.

When a current flows through the solenoid coil, it forms a magnetic field. When the current flowing through the solenoid coil is normal, the magnetic field does not have enough force to move the plunger. When an overcurrent flows through the solenoid coil, the magnetic force becomes stronger and the plunger is pulled toward the plug against the force of the spring. When the magnetic force reaches a certain strength, the plunger reaches the plug, and the plug attracts the armature 17 by the magnetic force to cut off the circuit.

The silicone oil in the cylinder plays a role in adjusting the moving speed of the plunger. Then, when the circuit is interrupted, the magnetic field disappears because no current flows through the coil, and the plunger is returned to its original position by the spring.

This oil damper type circuit breaker
The solenoid coil is wound on the outside of the cylinder, and the number of turns of the coil is extremely large, resulting in a large shape and extremely high manufacturing cost.

[0007]

The inventors of the present invention invented a novel circuit breaker which is small in size and extremely low in manufacturing cost, and applied for a patent on July 3, 1991 (reference number P9107). -009 and P9107-010). The present invention relates to the improvement of the above invention, and further, the structure is functionally simplified and the manufacturing cost is reduced.

[0008]

According to the present invention, a coil-shaped shape memory alloy having a transformation temperature higher than room temperature is used, and when an overcurrent flows in a circuit, the coil portion of the alloy is heated and connected to the alloy. The circuit breaks the circuit by operating the movable piece.

A shape memory effect is a phenomenon in which a material remembers its shape in a high temperature state and instantly returns to its original shape when heated even if it is severely deformed at room temperature. Such a material is an alloy exhibiting martensitic transformation, in which the high temperature phase is an ordered lattice phase and the transformation is a thermoelastic type, and martensite has a low symmetric crystal structure.

Various shape memory alloys such as nickel-titanium type, copper-aluminum-nickel type, copper-zinc-aluminum type and copper-tin type are known. It is necessary to select a memory alloy having a transformation temperature, that is, a shape recovery temperature higher than room temperature.
It preferably has a transformation temperature of 70 to 80 ° C.
Hereinafter, a detailed description will be given according to examples.

[0011]

Embodiment 1 FIGS. 1 and 2 are principle diagrams of this embodiment. The coil-shaped shape memory alloy 1 having one end fixed has a shape memorized in such a manner that it contracts when heated. The other end of the alloy is connected to the movable piece 2. The other end of the movable piece is in good contact with the switch.

In the structure of the switch, contacts 5 and 6 are attached to the central portions of the leaf springs 3 and 4, which are fixed to fixed bases 7 and 8 and the other end of the movable piece is sandwiched by the spring force of the leaf spring. It has a structure. Such a switch is also novel and operates in a very good and functional harmonization with the present invention.

In this state, the movable piece that opens and closes the circuit contacts the contact 5 of the switch, and the circuit is closed. The lever 9 is stopped by a stopper plate 10, and the lever has a structure of rotating around the stopper plate, and the tip of the lever is in contact with a protrusion provided on the movable piece 2.

When an overcurrent flows through the circuit, the coil portion of the shape memory alloy 1 generates heat, and when the temperature of the alloy reaches the transformation temperature, the contracting force of the alloy overcomes the restraining force of the two leaf springs and contracts. Then, the movable piece disconnects from the contacts 5 and 6 of the switch to cut off the circuit.

At this time, as shown in FIG. 2, the lever 9 rotates about the stopper plate 10 and is displaced. Next, if this lever is returned to its original position, the other end of the movable piece enters into the contacts 5 and 6 of the switch, and the circuit is closed again. Although the leaf spring is used in the switch structure in this embodiment, a spring may be used instead of the leaf spring.

[0016]

According to the present invention, compared with the conventional circuit breaker, and even compared with the above-mentioned patent application, the structure is functionally simplified, so that the size is further reduced and the cost is further reduced. It has the feature that a circuit breaker can be manufactured.

[Brief description of drawings]

FIG. 1 is a principle diagram of an embodiment of a circuit breaker according to the present invention, and is a closed circuit diagram.

FIG. 2 is a principle diagram of an embodiment of a circuit breaker according to the present invention, and is an open circuit diagram.

FIG. 3 is a sectional view of a conventional oil damper type circuit breaker.

[Explanation of symbols]

 1 coil shape memory alloy 2 movable piece 3 leaf spring 4 leaf spring 5 contactor 6 contactor 7 leaf spring fixing base 8 leaf spring fixing base 9 lever 10 clasp 11 load 12 cylinder 13 plug 14 plunger 15 spring 16 solenoid coil 17 Amateur

Claims (1)

[Claims] 1. A circuit breaker characterized in that a circuit is cut off by using a coil-shaped shape memory alloy having a transformation temperature higher than room temperature.