JPH0760629B2 - circuit protector - Google Patents

Description

The present invention relates to a circuit protector for preventing an excessive current from flowing in a circuit.

[Prior Art] Conventionally, a no-fuse type circuit protector generally uses a bimetal and operates the bimetal by heat generation due to an overcurrent.

Further, Japanese Utility Model Laid-Open No. 182247/1983 discloses a structure in which a shape memory alloy is used for the movable part. The shape memory alloy used here is a wire wound into a coil shape, and when the coil is heated by overcurrent, the coil that was pushed in and locked extends to the original memory shape and contacts It opens.

[Problems to be Solved by the Invention] When the above-mentioned conventional bimetal is used, the operating conditions vary greatly, the adjustment at the time of shipment is troublesome, and the operation is not stable even during long-term use. There is a drawback that.

In the case of using the coil-shaped shape memory alloy, it is not preferable that one end of the coil becomes a movable part and the electrical contact part moves. Moreover, the coil takes up a relatively large amount of spatial space, which has been an obstacle to the miniaturization of the device. It is possible to use a shape memory alloy for the plate material here, but it is not practical because it is more expensive than the wire material and the operating range and stroke are limited.

This invention was made in view of the above-mentioned conventional technology,
It is an object of the present invention to provide a circuit protector that is accurate in operation and that can save space and reduce the size of the device.

[Means for Solving the Problems] According to the present invention, a wire rod made of a shape memory alloy is provided with an operating member having a loop portion of several turns or less formed at both ends and extending in the same direction at both ends. Both ends are fixed to the terminals of both poles of the circuit and the actuating member is extended so that the loop part is contracted, and the contact connected in series with this actuating member and the contact actuated by engaging the loop part of the actuating member. It is a circuit protector provided with a contact opening member for opening.

[Operation] In the circuit protector of the present invention, the actuating member has a flat shape, does not occupy a space, and the electric connecting portion does not move so that the operating range is large and the loop portion returns to a memorized shape at a predetermined temperature and becomes large. The contact force is surely opened by that force.

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

In the circuit protector of this embodiment, a toggle switch 2 is provided in an insulating case 1, and an operating member 3 made of a wire material made of a shape memory alloy and electrically connected in series with the toggle switch 2 is attached. ing. The toggle switch 2 includes a toggle spring 4, a contact member 5 attached to its tip, a leaf spring 6 and a contact receiver 7 attached to its tip. As shown in FIGS. 4 to 6, the actuating member 3 has a loop portion 8 which is formed by bending a wire and rotating it once and a half turns. The shape shown in FIG. 4 is memorized. There is.

Further, inside the case 1, there is provided a contact opening member 10 having a convex portion 9 fitted into the loop portion 8 of the actuating member 3. The contact opening member 10 has a cam portion 11 for tilting the contact receiver 7 toward the contact member, a cam portion 12 for manually setting and releasing and an engaging portion 19, and a coil spring 13 The convex portion 9 engages with the loop portion 8 and biases the actuating member 3 in a pulling direction.

The cam portion 12 has a set rod 14 used for manual setting.
The engaging portion (extending in the back surface direction in the drawing) at the tip of the set abuts, and the base end of the set rod 14 is a manual operation member 15
It is attached to the tip of. The operation member 15 is biased by a coil spring 16 in a direction in which the set rod 14 is separated from the cam 12. Further, the case 1 is provided with a guide surface 17 for guiding the movement of the tip end portion of the set rod 14, and a fixed cam 18 with which the set rod 14 is engaged together with the cam portion 12.

Further, terminals 20 are attached to the case 1, and both ends of the toggle switch 2 and both ends of the operating member 3 are connected and fixed to the four terminals 20, respectively. Here, the operating member 3 is crimped to each terminal 20 because it cannot be soldered. Then, as shown in FIG. 7, the terminal 20 is connected so that the operating member 3 and the toggle switch 2 are connected in series.

Next, the operation of the circuit protector of this embodiment will be described.

Here, for example, if the rated current of the circuit is 0.4 A, it is preferable that the shape memory alloy of this embodiment has an Af point of 90 ° C. and an As point of about 60 ° C. The temperature rises above the As point. Further, the current value and the circuit interruption time are in an inversely proportional relationship, and the attraction force of the operating member 3 and the current value are in a proportional relationship, but under the condition that the temperature of the operating member 3 is Af point or more, for example, 0.6 A or more, The increasing tendency of the attraction force becomes smaller than that in the case where the operating member 3 is between the As and Af points. Further, the relationship between the displacement of the actuating member 3 and the attraction force is also proportional.

First, the shape memory alloy actuating member 3 is stretched from the shape shown in FIG. 4 to the shape shown in FIG. 6 so that the loop portion 8 is contracted.
Then, the extended loop portion 8 of the operating member 3 is fitted into the convex portion 9 of the contact opening member 10, and both ends of the operating member 3 are connected to the terminals 20.
Crimp to each. Further, other members are attached as shown in FIG.

Then, when the operating member 15 is pushed in, the set rod 14 slides along the cam portion 12, and as shown in FIG. 2, the engaging portion of the set rod 14 is placed on the cam surface facing the guide surface 17. Engage. At this time, the toggle spring 4 is moved toward the contact receiver 7 by the set rod 14, and when the neutral point is exceeded, the contact member 5 elastically abuts on the contact receiver 7 by the spring action. This state is normal and the circuit is closed.

However, when an abnormal current flows in the circuit, the operating member 3 is heated, and when it exceeds the transformation point of the shape memory alloy, the operating member 3 begins to return to the memorized shape as shown in FIG. At this time, as shown in FIG. 3, as the loop portion 8 becomes larger, the loop portion 8 moves toward both the crimped ends. Along with this, the contact opening member 10 moves to the left side in the figure against the coil spring 13 via the convex portion 9. Then, the contact portion 7 pushes the toggle spring 4 to the side opposite to the neutral point by the cam portion 11, and when the neutral point is exceeded, the contact member 5 and the contact point 7 are separated at once by the spring action. Further, the operation member 15 is
When the set rod 14 is released beyond the fixed cam 18, the coil spring 16 returns to the projecting position. As a result, the circuit is cut off and protected.

When the operating member 15 is pushed from the state of FIG. 2, the set rod 14 is guided by the guide surface 17 and the engagement with the cam portion 12 is released, and the operating member 15 engages with the engaging portion of the contact opening member 10. The contact opening member 10 is moved by engaging with 19, and the toggle switch 2 is opened in the same manner as above.

According to this embodiment, the actuating member 3 has a flat shape, and it is possible to reduce the size of the device without taking up space. Moreover, the operating point is accurate, and there is no variation in operation.

The operating member of the circuit protector of the present invention is
The number of turns of the loop portion may be appropriately set within a few turns, and may be determined in consideration of the required strength durability and the like.

[Effect of the Invention] In the circuit protector of the present invention, since the operating member that opens the circuit is flat, the device can be made compact without taking up space, and both ends of the operating member are fixed. , The electrical contacts do not move and are highly reliable and durable.

Moreover, since the shape memory alloy is used, the operating point is accurate, the variation is small, and there is no secular change.

[Brief description of drawings]

FIG. 1 is a front view showing the inside of a circuit protector of one embodiment of the present invention, FIG. 2 is a front view showing the inside of another state of this embodiment, and FIG. 3 is a further state of this embodiment. 4 is a front view showing the inside of the working member, FIG. 4 is a front view showing the working member of this embodiment, FIG. 5 is a side view of the working member, and FIG. 6 is a front view showing the operating state of the working member. The drawing is a circuit diagram showing a usage state of the circuit protector of this embodiment. 2 ... Toggle switch, 3 ... Actuating member, 4 ... Toggle spring, 5 ... Contact member, 7 ... Contact receiving member, 8 ... Loop part, 10 ... Contact opening member, 11,12 ... Cam part,

Claims (1)

[Claims] 1. A circuit protector for protecting a circuit by shutting off the circuit when a current of a predetermined value or more flows, wherein an operating member made of a wire of shape memory alloy is provided, and the operating member has a few turns or less in an intermediate portion. The loop part is formed and both ends memorize its shape in a state of extending in the same direction, and the mounting member is formed by extending the memory member so that the loop part is contracted when mounting. Both ends of the operating member are fixed to the terminals of both poles of the circuit, and a contact electrically connected in series with the operating member is provided to operate by engaging the loop portion of the operating member. A contact opening member is provided which opens the contact when the loop portion of the actuating member returns to a memory shape and becomes large and the loop portion approaches both ends fixed to the terminal. Circuit protector which is characterized.