JPS5913731Y2 - Thermal response device for circuit breakers and breakers - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a thermally responsive device for a circuit breaker, and in particular, when a bimetal is attached to a heating element, a metal plate with good thermal conductivity is provided behind the bimetal.

Traditionally, a bimetal has been incorporated into a circuit breaker with a cutoff mechanism along with a heating element, and when a predetermined current or more flows through the heating element, the temperature rises, the heat is transferred to the bimetal, and the bimetal bends and breaks the circuit. It is well known as a thermal type no-fuse breaker.

However, such a thermally responsive element using a bimetal has a structure in which the bimetal is directly attached to the heating element with screws, and the heat generated by the heating element, which is proportional to the energization circuit of the breaker, is not efficiently conducted to the bimetal. It took a considerable amount of time to adjust the operating time of the circuit breaker, and due to the physical properties of heat conduction, there were slight differences in the operating characteristic time depending on the mounting condition of the circuit breaker.

Taking these points into consideration, in the present invention, when attaching the bimetal to the heating element, a metal plate with good thermal conductivity is used, the bimetal is inserted between the heating element and the bimetal, and the bimetal is attached with a tightening screw.

In this case, the characteristics of the bimetal are such that the temperature of the heating element is completely and effectively transmitted to the bimetal, but since the only thing that exists is heat conduction, it is better to minimize the temperature difference between the two as much as possible.

In this way, by attaching a thermally good conductive metal plate behind the bimetal with respect to the heating element, these conventional drawbacks can be improved, and furthermore, it is possible to cut off the constant current at a predetermined time (the characteristics of the conventional method were poor due to air flow caused by heat generation). However, by attaching a thermally good conductive metal plate vertically behind the bimetal as in the present invention, it is possible to eliminate the variation in characteristics such that a constant current is cut off at a predetermined time.

To explain the present invention with reference to one embodiment shown in the figures, Fig. 1 is a side sectional view of a thermal response device of a circuit breaker according to the present invention, with the switching mechanism contacts etc. omitted, and Fig. 2 is a side sectional view of the thermal response device of the circuit breaker according to the present invention. FIG. 2 is an exploded perspective view of a thermally responsive element according to FIG.

In the figure, 1 is the lid of the circuit breaker, 2 is the mounting body of the new breaker mechanism, and 3 is a heating element, a part of which also serves as a lead wire through which the load current flows.

The heating element 3 has a magnet 8 fixed to the part that also serves as a lead wire.
A curved portion 3a is formed by extending the curved portion 3a as a detecting body of the heat generating portion, and is brought into close contact with the surface of the bimetal 4 to improve thermal efficiency as much as possible.

Furthermore, in the present invention, a metal plate 5 that is a good heat conductor such as copper or brass is attached vertically along the bimetal 4 on the opposite side of the heating element 3, similar to the bimetal 4, in order to bring these thermally responsive elements into close contact. Considering the property of easily transmitting the metal body upward, these three elements are stacked at the bottom and tightened using screws 6.

In addition, a fixed magnet 8 having a cross-sectional shape is screwed 11 to the heating element 3, which is usually made of brass or the like, and the electric current passes through the center of the heating element 3, which also serves as a lead wire, and the resulting electromagnetic force is When the current reaches a large current as shown by the dotted line in the figure, it passes through the movable iron piece 9 as shown by the dotted line at the top, and when the large current flows through the heating element 3, the electromagnetic force increases proportionally to the fixed magnet. Although not shown, the fixed magnet 8 instantly attracts the movable iron piece 9 so as to rotate the movable iron piece 9, which forms a part of the tripping mechanism installed opposite to the movable iron piece 8, around the shaft 7a. The opening/closing mechanism is removed to open the contacts.

On the other hand, when the load current reaches the overcurrent value, the heat generated by the heating element 3 is transmitted to the bimetal 4, which bends and pushes the movable piece 7, which is a part of the tripping mechanism, and the movable piece 7 is displaced around its axis 7a, causing The disengaging mechanism is disengaged from the engaging portion 10, and the tripping mechanism is operated to open the circuit in the same manner as in the case described above.

In this case, in the present invention, the heat generated by the heating element 3 is thermally conducted to the bimetal 4, and by providing a metal plate 5 with good thermal conductivity behind the bimetal 4, a portion of the heat dissipated through the contact air around the heating element 3 is absorbed. This has a great practical effect, as it effectively captures heat, greatly improves thermal efficiency, and improves interrupting performance characteristics.

[Brief explanation of the drawing]

FIG. 1 is a side view of a circuit breaker including a side sectional view of the main parts according to the present invention, and FIG. 2 is an exploded perspective view of a thermally responsive element. FIG. 3 is a side sectional view for explaining the electromagnetic operation of the heating element 3, fixed magnet 8, and movable iron piece 9. In the figure, 2 and 3 are heating elements, 4 is a bimetal, and 5 is a metal plate that is a good thermal conductor.

Claims (1)

[Scope of utility model registration request] Attaching the cutoff mechanism A magnet 8 is attached to a part of the heating element 3 which also serves as a lead wire and whose one end is fixed to the main body 2, and the other end of the heating element 3 is extended to form a curved part 3a as a detecting body of the heating part. While the thermal efficiency is improved by closely contacting the surface of the bimetal 4, a metal plate 5 having good thermal conductivity such as copper or brass is placed vertically in the same manner as the bimetal 4.
These three elements 3, 4, and 5 are stacked at the lower bottom so that they are on the opposite side of the heating element 3, and are tightened and fixed using screws 6, so that the bimetal 4 is heated by the heating element 3. A circuit breaker in which a movable piece 7, which is a part of a tripping mechanism, is pushed by the curvature of the circuit breaker, and the movable piece 7 is displaced about its axis 7a to disengage from an engagement part 10 of the tripping mechanism. thermal response device.