JP2010282787A - Thermal tripping device, and circuit breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal tripping device for preventing a change in the curving characteristics of a bimetal when assembled. <P>SOLUTION: The thermal tripping device includes the bimetal 11 to be heated by an overcurrent, and a conductive extension member 10 to which a flexible conductor 7 is joined. The extension member 10 is joined to the bimetal 11 with mechanical joint. The extension member 10 has one end extending from the opening end of the bimetal 11 for pushing a trip bar 8 by curving of the bimetal 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a thermal tripping device used for a circuit breaker, for example.

  In the conventional thermal tripping device, the power supply side terminal and the fixed contact are connected, and the movable contact is arranged so as to contact the fixed contact. Constitute. The movable contact is joined to the bimetal and is switched by an electrical connection / disengagement with the fixed contact by being driven by an opening / closing mechanism. The bimetal faces the trip bar in the vicinity of the open end that pushes the trip bar, and is arranged in a direction that curves toward the trip bar as the bimetal temperature rises. A flexible conductor is joined in the vicinity of the open end of the bimetal, and the other end of the flexible conductor is connected to the load side terminal.

JP-A-9-82202 (FIG. 5)

  However, the conventional thermal tripping apparatus generally uses welding to join the flexible conductor to the bimetal, and in the welding, direct heating to the bimetal is indispensable. There is a risk that the bending characteristics may change. When the bimetal bending characteristic changes, there is a problem that the overcurrent detection characteristic of the circuit breaker varies.

  An object of the present invention is to obtain a thermal tripping device that prevents a change in the bending characteristics of a bimetal during assembly.

  The thermal tripping device according to the present invention includes a bimetal heated by an overcurrent and a conductive extension member joined with a flexible conductor. The extension member is joined to the bimetal by mechanical joining, and one end portion extended from the open end portion of the bimetal in the extension member pushes the trip bar due to the curvature of the bimetal.

  In the thermal tripping device according to the present invention, since the bimetal and the extension member are joined by mechanical joining, it is possible to prevent a change in the bending characteristics of the bimetal during assembly.

It is a partially broken side view which shows the circuit breaker which has a thermal tripping device in Embodiment 1 of this invention. It is a sectional side view of the thermal tripping device in the circuit breaker of FIG.

Embodiment 1 FIG.
1 is a partially broken side view showing a circuit breaker having a thermal tripping device according to Embodiment 1 of the present invention. An insulating housing 30 of the circuit breaker includes a base 1 and a lid 2 each made of synthetic resin. A power supply terminal 3 for detachably connecting a power supply side electric wire and a load terminal 6 for detachably connecting a load side electric wire are mounted on the base 1. A fixed contact 4 provided with a power terminal 3 at one end is attached to the base 1. The movable contact 5 that contacts and separates from the fixed contact 4 is connected to a thermal trip device 20 that operates the opening / closing mechanism 9 in response to an overcurrent. The flexible conductor 7 having one end connected to the load terminal 6 is connected to a thermal tripping device 20.

  The thermal tripping device 20 is an extension provided with a bimetal 11, a support 12 fixed to the lower end portion of the bimetal 11 with a rivet 14, a yoke 13, and an adjustment screw 16 fixed to the upper end portion of the bimetal 11 with a rivet 15. Consists of member 10. The opening / closing mechanism 9 that opens and closes the movable contact 5 with respect to the fixed contact 4 has a trip bar 8, and operates when the trip bar 8 is pressed by a thermal tripping device 20. The operation when an overcurrent exceeding the rated current flows will be described below.

  When an overcurrent flows through the bimetal 11, the temperature of the bimetal 11 rises due to Joule heat. The bimetal 11 bends as the temperature of the bimetal 11 increases. The bending amount of the bimetal 11 is increased, the adjusting screw 16 is brought into contact with the trip bar 8, and the bending amount of the bimetal 11 is further increased, so that the thermal tripping device 20 pushes the trip bar 8. When the trip bar 8 is pressed by the thermal tripping device 20, the opening / closing mechanism 9 is activated, and the movable contact 5 is instantaneously separated from the fixed contact 4 to reach the load terminal 6 from the power supply terminal 3. A certain main circuit is shut off (tripped).

  The thermal tripping device 20 will be described in detail. 2 is a side sectional view of the thermal trip device in the circuit breaker of FIG. The support 12 connects the movable contact 5 and the bimetal 11 as a member constituting the energization path of the main circuit, and simultaneously fixes the bimetal 11 to the base 1. The yoke 13 operates when the armature (not shown) is attracted to the yoke 13 by a magnetic field generated by a current when a short-circuit current flows in the main circuit, and the opening / closing mechanism 9 is operated. The yoke 13, the support 12, and the bimetal 11 are caulked together by a rivet 14 and fixed to each other.

  The lower end portion of the bimetal 11 is a fixed end portion fixed to the base 1 via the support 12, and the upper end portion of the bimetal 11 is an open end portion that rotates with the fixed end portion as a fulcrum by the bending of the bimetal 11. . The extension member 10 is fixed to the upper end portion of the bimetal 11 by a rivet 15, that is, the extension member 10 is joined to the bimetal 11 by mechanical joining. The extension member 10 is provided with a screw hole, and an adjustment screw 16 is assembled. The adjusting screw 16 is attached at a position where it abuts on the trip bar 8 when the bimetal 11 is curved.

  The adjusting screw 16 adjusts the distance between the thermal tripping device 20 and the trip bar 8. In addition to the method using the adjusting screw 16 shown in this example, there are a method of joining the adjusting member, a method of adjusting by bending the adjusting member, and the like, and these methods can also be used. Further, an adjusting member such as the adjusting screw 16 may be incorporated in the trip bar 8 instead of the bimetal 11 side.

  One end of the flexible conductor 7 is joined to the lower end portion of the extension member 10, and the other end of the flexible conductor 7 is joined to the load side terminal 6. For the flexible conductor 7, a flexible conductive member such as a copper stranded wire is used so as not to disturb the bending of the bimetal 11. The flexible conductor 7 and the extension member 10 are joined by welding or caulking using rivets.

  Conventionally, the flexible conductor 7 and the bimetal 11 are joined using a brazing material in order to prevent the temperature rise as much as possible. In the first embodiment, when the flexible conductor 7 and the extension member 10 are welded before the extension member 10 and the bimetal 11 are joined, the brazing material is used in the welding of the flexible conductor 7 and the extension member 10. There is no need. Therefore, the work is simplified as compared with the conventional case, and bonding can be performed at a low cost.

  Conventionally, it has been difficult to use caulking for joining the bimetal 11 and the flexible conductor 7. The bimetal 11 used for the circuit breaker is because when the caulking process is used for joining the bimetal 11 and the flexible conductor 7, the pressurization to the bimetal 11 is non-uniform and cracks are likely to occur. However, in the first embodiment, when the flexible conductor 7 is joined to the thermal tripping device 20 by caulking, unlike the conventional case in which the flexible conductor 7 is caulked to the bimetal 11, the flexible conductor 7 and the extension member are used. 10 and the bimetal 11 is not cracked. Therefore, it is not necessary to use a brazing material that has been necessary in the prior art, and the work is simplified as compared with the prior art, and bonding can be performed at low cost.

  In order to energize the bimetal 11, it is necessary to connect the conductors of the main circuit at two different locations of the bimetal 11. In the first embodiment, one side is connected to a lower end portion of the bimetal 11 with a support 12 made of a conductive material such as copper, iron, or aluminum so as to be fixed to the base 1 of the circuit breaker. The other has an extension member joined to the upper end of the bimetal 11 by mechanical joining. The flexible conductor 7 connected to the load terminal 6 is connected to the extension member so as not to prevent the bending displacement of the bimetal 11.

  In the thermal tripping device 20 according to the first embodiment, the flexible conductor 7 connected to the load terminal 6 is connected to the extension member 10, and the extension member 10 is joined to the upper end portion of the bimetal 11 by mechanical joining. The bimetal 11 is not heated when forming the main circuit. Accordingly, since the flexible conductor 7 is joined to the bimetal 10 by welding, heating to the bimetal 11 is unavoidable, and unlike the conventional case in which the bending characteristics of the bimetal 11 may change due to the heating, The bending characteristics of the bimetal 11 can be maintained without changing the bending characteristics. Further, since the extension member 10 is joined to the upper end portion of the bimetal 11 by mechanical joining, the amount of use of the bimetal 11 can be reduced.

  In the first embodiment, unlike the conventional case, the length of the bimetal 11 in the longitudinal direction is shortened. That is, the open end of the bimetal 11 is brought close to the fixed end. Instead, the extension member 10 is joined to the open end of the bimetal 11 that has become shorter. The extension member 10 is made of a metal different from the bimetal 11, and unlike the bimetal 11, the extension member 10 does not bend even when the temperature rises. Therefore, in the first embodiment, the length of the bimetal 11 at the position of the adjusting screw 16 is longer than that of the conventional thermal tripping device in which the length from the fixed end of the bimetal 11 to the tip of the extension member 10 is all bimetal. The amount of displacement due to the curvature of is reduced. However, the decrease in the displacement amount hardly affects the operation of the thermal tripping device 20 for the following reason.

  Consider a case where the temperature of the entire bimetal 11 rises uniformly. Assume that the length of the conventional bimetal 11 in the longitudinal direction is 50 mm, and 20% of the length from the tip is replaced with the extension member 10. When the extension member 10 is connected when the displacement amount at the open end of the conventional bimetal is 3 mm, the decrease in the displacement amount at the open end of the thermal trip device 20 is about 4%. Stay on the decline. This greatly affects the displacement at the open end of the thermal trip device 20 at the lower end of the bimetal, that is, at the fixed end, and relatively at the upper end, that is, at the open end. This is because the influence is small. If the displacement is reduced by about 4%, it can be said that there is almost no influence. Therefore, the opening / closing mechanism 9 and the like in the circuit breaker is redesigned by setting the length of the extension member 10 from the joined portion to the open end in the joined body of the bimetal 11 and the extending member 10 to 20% or less of the total length of the joined body. The thermal tripping device 20 can be replaced with that of the first embodiment without any problem. That is, if the decrease in the amount of displacement at the open end is about 0.12 mm, which is 4% of 3 mm, the distance between the adjustment screw 16 and the trip bar 8 is adjusted by adjusting the adjustment screw 16 according to the first embodiment. Can be the same as before replacement.

  Moreover, in Embodiment 1, the joining process of the bimetal 11 and the extension member 10 will naturally increase by replacing the open end of the conventional bimetal 11 with the extension member 10. However, since the bimetal 11 is more expensive than a general conductor material, the cost reduction by reducing the amount of bimetal used is greater than the cost increase due to the increase in the number of joining steps, and the overall cost of the thermal tripping device 20 is low. Reduction. Therefore, the cost of the circuit breaker incorporating the thermal trip device 20 of the first embodiment can be reduced.

  The range of operating characteristics (tripping characteristics) when an overcurrent flows is defined by standards such as JIS, and products must satisfy this range. In general, the operating point of the tripping mechanism, that is, the position where the thermal tripping device 20 pushes the trip bar 8 is the processing / assembly error of each component constituting the thermal tripping device 20 and the opening / closing mechanism 9. Variations in the tripping characteristics occur due to variations in the accumulation of manufacturing variations such as variations in material characteristics. Therefore, in order to absorb such manufacturing variations, the distance (gap) between the adjusting screw 16 and the trip bar 8 is adjusted and inspected in the assembly process.

  Since the circuit breaker of the first embodiment does not change the bending characteristics of the bimetal 11 when the thermal trip device 20 is incorporated in the base 1 to form the main circuit, the overcurrent of the circuit breaker is not changed. Detection characteristics do not vary greatly. Therefore, since the overcurrent detection characteristic of the circuit breaker does not vary greatly, the distance (gap) between the adjusting screw 16 and the trip bar 8 is rarely adjusted. Therefore, it is possible to shorten the time for the inspection / adjustment process of the thermal tripping device 20.

  As described above, the thermal tripping device 20 according to the first embodiment of the present invention includes the bimetal 11 heated by overcurrent and the conductive extension member 10 to which the flexible conductor 7 is joined. The extension member 10 is joined to the bimetal by mechanical joining, and one end portion extended from the open end of the bimetal 11 in the extension member 10 pushes the trip bar due to the bimetal curve, so that the conventional bimetal curve characteristic changes. Unlike the case where there is a risk of the occurrence of such a problem, it is possible to prevent a change in the bending characteristics of the bimetal during assembly.

  According to the circuit breaker in Embodiment 1 of the present invention, the thermal trip device 20 includes the bimetal 11 heated by overcurrent and the conductive extension member 10 to which the flexible conductor 7 is joined. The extension member 10 is joined to the bimetal by mechanical joining, and one end of the extension member 10 extended from the open end of the bimetal 11 pushes the trip bar due to the bimetal curve, so that the overcurrent detection characteristic of the circuit breaker is It does not vary greatly.

  In addition, although the example which uses the rivet 15 as a mechanical joining of the bimetal 11 and the extending member 10 was demonstrated, joining using a screw | thread or the joining by fitting may be sufficient.

  Alternatively, the flexible conductor 7 and the extension member 10 may be joined after the extension member 10 and the bimetal 11 are joined. Even in this case, since the flexible conductor 7 is not directly joined to the bimetal 11, heat conduction to the bimetal 11 can be reduced as compared with the conventional case, and a change in the bending characteristics of the bimetal during assembly can be prevented. When the flexible conductor 7 and the extension member 10 are welded after the extension member 10 and the bimetal 11 are joined, heat conduction to the bimetal 11 can be reduced by using a brazing material.

  Moreover, although the example in which the joint portion between the extension member 11 and the flexible conductor 7 is the lower end portion of the extension member 11 has been described, the joint may be joined to another place as long as the adjustment operation is not hindered. For example, a joining space may be provided by extending the member in the center of the extension member 11 or in the left-right direction.

  Further, a heating body may be disposed in the vicinity of the bimetal 11 and a method of indirectly heating the bimetal 11 from the heating body and a method of directly heating the bimetal 11 may be used in combination.

  Since the thermal tripping device according to the present invention can prevent a change in the bending characteristics of the bimetal during assembly, it can be suitably applied to a circuit breaker having an opening / closing mechanism for opening / closing an electric circuit.

DESCRIPTION OF SYMBOLS 1 Base 2 Lid 4 Fixed contact 5 Movable contact 7 Flexible conductor 8 Trip bar 9 Opening / closing mechanism 10 Extension member 11 Bimetal 20 Thermal tripping device 30 Insulation case

Claims (4)

A thermal trip device that pushes the trip bar by bending of the bimetal heated by overcurrent,
A conductive extension member joined with a flexible conductor;
The extension member is joined to the bimetal by mechanical joining,
One end portion of the extension member extended from the open end portion of the bimetal pushes the trip bar by bending of the bimetal.   The thermal trip device according to claim 1, wherein the extension member is joined to the open end of the bimetal.   In the joined body of the bimetal and the extension member, the length from the end of the extension member to the joined portion of the joined body in the joined body is 20% or less of the total length of the joined body. The thermal tripping device according to claim 1 or 2. An insulating housing composed of a base and a lid, a fixed contact mounted on the base of the insulating housing, a movable contact installed facing the fixed contact, and a trip bar. An open / close mechanism that opens and closes the movable contact with respect to the fixed contact; and a thermal trip device that is connected to the movable contact and operates the open / close mechanism in response to an overcurrent.
4. The circuit breaker according to claim 1, wherein the thermal trip device is the thermal trip device according to claim 1.

Images