JP2010218765A - Overcurrent tripping device of circuit breaker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an overcurrent tripping device of a circuit breaker which prevents a delay in overcurrent tripping action to improve current-breaking performance. <P>SOLUTION: Between a heater 9c disposed on a current path and a trip bar 24 of a switching mechanism 15, a bimetal 26 is disposed with its base end fixed to the heater and its front end extended toward the trip bar, and a runoff tab 27 is fixed to the tip of the bimetal with a free end thereof located near the trip bar. A flow of overcurrent through the current path causes the heater to generate heat so that the tip of the bimetal is heated and bent. This bending of the bimetal tip results in a shift in the position of the free end of the runoff tab, which eventually comes in contact with the trip bar. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermal overcurrent tripping device used for a circuit breaker such as a circuit breaker or a leakage breaker.

The thermal overcurrent tripping device for a circuit breaker is such that when an overcurrent flows between the power supply side terminal and the load side terminal, the heated bimetal bends, and the bending action of this bimetal acts by opening and closing the contact mechanism. It is a device that opens the child.
As a method of heating the bimetal, there is a direct heating type in which a current is directly applied to the bimetal and heated to bend and deform, and a heater that generates heat by the flow of current, and the bimetal is heated to bend and deform by the generated heat. A thermal type is known, and an indirectly heated type mainly equipped with a heater is adopted except for some models with a small rated current.

As a circuit breaker provided with an indirectly heated overcurrent tripping device, for example, the device of Patent Document 1 is known.
In the apparatus of Patent Document 1, the base end of the bimetal is joined to the heater, the tip of the bimetal is disposed close to a part of the opening / closing mechanism, and an overcurrent flows between the power supply side terminal and the load side terminal. The bimetal is bent and deformed by the heat generated by the heater, and the opening / closing mechanism opens the contact.

JP 2001-84885 A

By the way, normally, the amount of bending of the bimetal is set on the basis of the temperature at which the bimetal is in a thermal equilibrium state near the minimum operating current, so in the overcurrent region, the temperature rise of the bimetal is delayed with respect to the heat generation of the heater, A time delay occurs in the operation of the overcurrent tripping device with respect to the heat generation amount of the entire circuit breaker.
As a cause of the time delay of the operation of the overcurrent tripping device, there are a delay in the time for the amount of heat generated outside the heater to reach the heater and a delay in the time for the amount of heat generated in the heater to be transmitted to the entire bimetal. Here, when a high current flows, a delay in time during which the amount of heat generated by the heater is transmitted to the entire bimetal is a cause of a time delay in the operation of the overcurrent tripping device.

  Here, in the device of Patent Document 1 in which a single bimetal extends between the heater and the opening / closing mechanism, heat from the base end side (heater side) to the tip end side of the bimetal increases when an overcurrent increases. Since conduction is slow and a large temperature gradient occurs between the base end and tip end of the bimetal, it is necessary to ensure that the bimetal has the same amount of deflection as at the minimum operating current by deformation due to heating only on the heater side (base end side). There is.

Therefore, in the device of Patent Document 1, the heating temperature of the conductor composed of the base end portion of the bimetal and the heater is very high compared to the minimum operating current, the change in overcurrent detection characteristics due to the permanent deformation of the bimetal, There are problems such as dropping of the contacts electrically connected to the conductor, thermal damage due to bimetal and fusing of the conductor, and the like.
In the device of Patent Document 1, the amount of bending deformation can be increased by increasing the length of the bimetal between the heater and the opening / closing mechanism, but the operation delay time when a high current flows increases. Conversely, if the length of the bimetal between the heater and the opening / closing mechanism is shortened, the operation delay time when a high current flows is shortened, but a large amount of bending deformation of the bimetal necessary for the operation of the opening / closing mechanism cannot be obtained. .

Furthermore, when the device of Patent Document 1 secures the length from the base end side (heater side) to the tip end side of the bimetal so that the deflection amount necessary for the operation of the opening / closing mechanism is obtained at the minimum operating current, a high current is generated. There is a possibility that the time delay when flowing will be larger than the allowable time.
Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and the overcurrent of the circuit breaker capable of improving the breaking performance without causing a time delay in the overcurrent tripping operation. The object is to provide a trip device.

  In order to achieve the above object, an overcurrent tripping device for a circuit breaker according to the present invention provides an overcurrent tripping circuit breaker for opening the switching mechanism by contacting a trip bar of the switching mechanism. A bimetal having a proximal end fixed to the heater and a distal end extending to the trip bar side between the heater provided in the current path and the trip bar; and a distal end of the bimetal An extension plate that is fixed and has a free end positioned in the vicinity of the trip bar. Overcurrent flows through the current path and the heater generates heat. The tip of the bimetal heated by the heat generated by the heater is bent and deformed. The free end of the extension plate that is displaced along with the bending deformation of the tip end portion of the bimetal is in contact with the trip bar.

  According to this invention, a single bimetal is not disposed between the heater and the trip bar of the opening / closing mechanism as in the prior art, and the short bimetal whose base end is fixed to the heater is bent and deformed with a small amount of bending, The extension plate fixed to the tip of the bimetal converts the small bending deformation of the bimetal into a large displacement, and normally performs the opening operation of the opening / closing mechanism. Thereby, since the short bimetal has a small temperature gradient from the base end portion to the tip end portion, no time delay occurs in the operation of the overcurrent tripping device.

  And, for example, if the area of ½ of the space between the heater and the trip bar of the opening / closing mechanism is bimetal, the heat transfer length of the bimetal will be halved, but the amount of bimetal displaced to contact the trip bar It is possible to secure about 1/4 of the amount of bending and about 3/4 of the amount of displacement of the extension plate. In addition, if the area of 1/3 of the space between the heater and the trip bar of the opening / closing mechanism is bimetal, the amount of deflection of the bimetal that is displaced to contact the trip bar is about 1/2, and the amount of displacement of the extension plate Can also secure about 1/2. Thus, the present invention changes the length of the bimetal and the extension plate, so that the amount of displacement and temperature required to contact the trip bar are prevented so as not to cause a time delay in the operation of the overcurrent trip device. The length of the bimetal whose gradient changes can be set as appropriate.

In the overcurrent tripping device for a circuit breaker according to the present invention, the extension plate may be composed of a metal plate made of a single metal material or a synthetic resin plate.
According to the present invention, not only a relatively expensive single bimetal is arranged between the heater and the trip bar of the opening / closing mechanism, but an inexpensive single metal material metal plate or an extension plate made of a synthetic resin plate is used. Therefore, the manufacturing cost of the circuit breaker can be reduced.

Furthermore, it is preferable that the overcurrent tripping device for a circuit breaker according to the present invention has the bimetal tip and the extension plate fixed by caulking.
According to the present invention, since the bimetal tip and the extension plate are fixed by caulking with a simple structure, the manufacturing cost of the circuit breaker can be further reduced.

  According to the overcurrent tripping device for a circuit breaker according to the present invention, the bimetal and the extension plate are connected to each other between the heater and the trip bar of the opening / closing mechanism, and the base end is fixed to the heater. The short bimetal bends and deforms with a small amount of bending, and the extension plate fixed to the tip of the bimetal converts the small bending deformation of the bimetal into a large displacement, so that the opening / closing mechanism can be normally opened. . In addition, since the short bimetal has a small temperature gradient from the base end portion to the tip end portion, there is no time delay in the operation of the overcurrent tripping device, and the interruption performance can be improved.

It is sectional drawing which shows schematic structure of the circuit breaker which concerns on this invention. It is a perspective view which shows the bimetal and extension plate of an integral structure which comprise the overcurrent trip apparatus of 1st Embodiment of the circuit breaker which concerns on this invention. It is a figure which shows operation | movement of the overcurrent trip apparatus of 1st Embodiment which concerns on this invention. It is a figure which shows operation | movement of the overcurrent trip apparatus of conventional structure. It is a graph which shows the bending simulation when a temperature gradient generate | occur | produces toward a free end from the base end part in the bimetal used in 1st Embodiment which concerns on this invention, and the long bimetal of a prior art. It is a perspective view which shows the bimetal and extension plate of the integral structure which comprise the overcurrent trip apparatus of 2nd Embodiment which concerns on this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.
1 to 6 show a circuit breaker according to the present invention, FIG. 1 is a sectional view showing a schematic configuration of the circuit breaker, and FIG. 2 is an overcurrent tripping circuit according to a first embodiment of the circuit breaker. FIG. 3 is a diagram showing the operation of the overcurrent trip device according to the first embodiment, and FIG. 4 is a diagram showing the operation of the overcurrent trip device having a conventional structure. FIG. 5 is a graph showing a bending simulation when a temperature gradient is generated from the base end portion toward the free end of the bimetal used in the first embodiment and the long bimetal of the prior art, and FIG. It is a perspective view which shows the bimetal and extension plate of the integral structure which comprise the overcurrent trip apparatus of 2nd Embodiment of a circuit breaker.

As shown in FIG. 1, the circuit breaker according to this embodiment includes an arc extinguishing chamber 3, an overcurrent trip device 4, a stationary contact 5, and a movable member in an insulating container composed of a case 1 and a cover 2. A contact 6, a holder 7 that rotatably holds the movable contact 6, and an opening / closing mechanism 15 that opens and closes the movable contact 6 via the holder 7 are disposed.
The fixed contact 5 has a power supply side terminal 5a formed on one end side and a fixed contact 5b formed on the other end side. The movable contact 6 is formed with a movable contact 6 a that contacts the fixed contact 5 b of the fixed contact 5. The arc extinguishing chamber 3 extinguishes an arc generated due to an opening / closing operation between the fixed contact 5b and the movable contact 6a. The cover 2 includes a middle cover 2a and a top cover 2b.

One end of a flexible lead wire 8 is connected to the proximal end of the movable contact 6, and the other end of the lead wire 8 is connected to one end of the relay conductor 9 via a wire connection plate 10.
The relay conductor 9 is bent from the lower flat plate portion 9b connected to the electric wire connecting plate 10, the rising plate portion 9c rising from the end portion of the lower flat plate portion 9b, and the upper end of the rising plate portion 9c. And an upper flat plate portion 9d extending in a direction away from the lower flat plate portion 9b, and a load side terminal 9a formed on the other end side of the upper flat plate portion 9d. The rising plate portion 9c of the relay conductor 9 serves as a heater (hereinafter referred to as a heater 9c).

  The opening / closing mechanism 15 engages with a handle 16 that performs an opening / closing operation, a handle lever 17 that operates in conjunction with the handle 16, a toggle link mechanism 21 that includes an upper toggle 18 and a lower toggle 19, a latch 20, and a latch 20. A latch bar 22, an intermediate latch 23, and a trip bar 24 that rotates the intermediate latch 23 to disengage the latch 20 and the latch receiver 22. The upper toggle 18 and the lower toggle 19 are connected to each other via a toggle pin 25, the upper end of the upper toggle 18 is connected to the latch 20 so as to freely rotate, and the lower toggle 19 is connected to the holder 7. Further, a lower end hook portion of a spring (not shown) is hooked on the toggle pin 25, and an upper end hook portion of the spring is hooked on the upper end of the handle lever 17.

  The overcurrent trip device 4 includes a bimetal 26 having a lower portion fixed to the rising plate portion 9c of the relay conductor 9, and an extension plate 27 fixed to the free end of the upper portion of the bimetal 26 and extending to the vicinity of the trip bar 24. An adjustment screw 28 that engages with the free end of the upper portion of the extension plate 27 and is movable forward and backward so as to provide a predetermined gap with the trip bar 24, and a heater 9c that is caulked and fixed to the lower portion of the bimetal 26, When a large current such as a short-circuit current flows between the power supply side terminal 5a and the load side terminal 9a, an armature 30 and a fixed magnet 29 are provided to strike the trip bar 24 at the tip and disengage the latch 20 from the latch receiver 22. ing.

  As shown in FIGS. 2A and 2B, the bimetal 26 is a rectangular plate-like member that is long in the vertical direction. The extension plate 27 is formed of a metal plate made of a long single metal material narrower than the bimetal 26 or a synthetic resin plate, and extends in the same direction as the surface direction of the bimetal 26 by being fixed to the bimetal 26. The flat plate portion 27a is provided, and the bent portion 27b is bent slightly in the direction from the flat plate portion 27a toward the trip bar 24 and engaged with the adjusting screw 28.

The lower portion (one in the longitudinal direction) of the bimetal 26 and the rising plate portion 9c are fixed by caulking by the rivet 31a, and the upper portion (the other in the longitudinal direction) of the bimetal 26 and the lower portion of the extension plate 27 are caulked by the rivet 31b. It is fixed.
The extension plate 27 may not be a single metal material. However, if iron, copper, aluminum, or the like is used as the single metal material, the formability is better than that of the bimetal. There is an advantage of increasing the degree.

Next, the operation of the circuit breaker of this embodiment will be described with reference to FIGS. 1, 3A and 3B, and a conventional circuit breaker (long bimetal without using an extension plate) will be described. The operation of the apparatus using 32: hereinafter referred to as the prior art will be compared with the apparatus of this embodiment with reference to FIGS. 4 (a) and 4 (b).
As shown in FIG. 1, the circuit breaker according to the present embodiment is in a closed state where the fixed contact 5 and the movable contact 6 are closed, as shown in FIG. 1, the power supply side terminal 5a, the fixed contact 5, the movable contact 6, and the lead. A current flows through the current path of the wire 8, the wire connection plate 10, the heater 9c, the relay conductor 9, and the load side terminal 9a.

  When the current flowing through the current path is overloaded, the bimetal 26 is bent counterclockwise by the heat generated from the heater 9c and is simultaneously fixed to the bimetal 26 as shown in FIG. 27 also rotates counterclockwise, the tip of the adjusting screw 28 contacts the trip bar 24, and the trip bar 24 rotates counterclockwise around the support shaft 24a. By rotating the trip bar 24, the intermediate latch 23 is rotated, the latch 20 and the latch receiver 22 are disengaged, the toggle link mechanism 21 is operated, and the holder 7 connected to the lower toggle 19 is rotated. The movable contact 6 is separated from the fixed contact 5 to be in an open state.

  When a large current such as a short-circuit current flows to the heater 9c, the armature 30 of the overcurrent trip device 4 rotates counterclockwise and is instantaneously attracted to the fixed magnet 29, and the tip bar 24 Tap. When the trip bar 24 is struck, the latch 20 and the latch receiver 22 are disengaged, the toggle link mechanism 21 is operated, the holder 7 connected to the lower toggle 19 is rotated, and the movable contact 6 is fixed. It is separated from the contactor 5 to be in an open state.

  Here, as shown in FIGS. 3A and 3B, the initial gap between the adjusting screw 28 and the trip bar 24 is G1, and the intermediate latch 23 is rotated to engage the latch 20 and the latch receiver 22. Assuming that the operating stroke of the trip bar 24 to be removed is S1, the overcurrent tripping device 4 of the present embodiment uses a bimetal 26 for moving the upper part of the extension plate 27 by a displacement amount D1 (D1 = G1 + S1) during the opening operation. The deflection amount B1 is a value that is significantly smaller than the displacement amount D1 of the upper portion of the extension plate 27 (B1 <D1).

  On the other hand, in the conventional technique using the long bimetal 32 without using the extension plate, as shown in FIGS. 4 (a) and 4 (b), the adjustment engaged with the free end on the upper part of the bimetal 32. When the initial gap between the screw 28 and the trip bar 24 is G2, and the operation stroke of the trip bar 24 that disengages the latch 20 and the latch receiver 22 is S1, the value obtained by adding the initial gap G2 and the operation stroke S1 is bimetal. It becomes the amount of bending B2 which 32 itself bends and deforms.

  As is clear from FIGS. 3 and 4, the overcurrent tripping device 4 provided with the bimetal 26 and the extension plate 27 according to the present embodiment opens and closes the extension plate 27 by the bending deformation of the bimetal 26 with a small deflection amount B1. A displacement amount D1 necessary for the opening operation of the mechanism 15 is ensured. On the other hand, in the conventional technique including only the bimetal 32, the bimetal 32 itself secures the displacement amount D2 necessary for the opening operation of the opening / closing mechanism 15 (deflection amount B2 = displacement amount D2).

  Next, FIG. 5 shows a temperature gradient generated by abruptly raising the lower heating temperature of the short bimetal 26 of the present embodiment (described as the present invention in FIG. 5) and the long bimetal 32 of the prior art. 3 shows a bending simulation at the moment when the bending of the tips of the bimetal 26 and the bimetal 32 becomes the same as that at the time of temperature equilibrium. In this simulation, the temperature at equilibrium is made uniform throughout.

  As is apparent from FIG. 5, when the lower heating temperature is suddenly increased to generate the same deflection as that at the equilibrium temperature, the lower temperature of the conventional long bimetal 32 is increased by 2.5 times that of the equilibrium state. Even under such conditions, the short bimetal 26 of the present embodiment is accommodated about 1.7 times. This difference becomes wider as the temperature gradient becomes larger, and there is a possibility that the conductor is blown, the fixed contact 5b and the movable contact 6a are dropped, the bimetal 32 is permanently deformed, and the like.

  As described above, according to the conventional technique, the long single bimetal 32 is disposed between the heater 9c and the trip bar 24 of the opening / closing mechanism 15, so that the large deflection amount B2 required for the opening operation of the opening / closing mechanism 15 is achieved. (Displacement amount D2) is obtained, but the long bimetal 32 has a large temperature gradient due to slow heat conduction from the lower part (heater 9c side) to the upper part (adjustment screw 28 side). There is a problem in terms of time delay of operation. Further, in the prior art, it is necessary to ensure a deflection amount equivalent to that at the time of the minimum operating current by heating only the lower part, but the heating temperature of the lower part of the bimetal 32 by the heater 9c becomes very high, and due to permanent deformation of the bimetal 32. There are problems such as thermal damage due to changes in overcurrent detection characteristics, fusing of conductors composed of bimetals and heaters, and the like.

  On the other hand, the overcurrent tripping device 4 of the present embodiment is bent and deformed with a small bending amount B1 by using a short bimetal 26 as compared with the prior art, but connected to the upper part of the bimetal 26. The extension plate 27 can obtain the displacement amount D1 necessary for the opening operation of the opening / closing mechanism 15. Further, the short bimetal 26 as compared with the prior art does not slow down the heat conduction from the lower part (on the heater 9c side) to the upper part (on the adjusting screw 28 side), resulting in a small temperature gradient. There is no time delay in the operation. In addition, since the bimetal 26 of the present embodiment does not set the heating temperature by the heater 9c high and the bending deformation of the bimetal 26 can be reduced, it is possible to prevent a change in overcurrent detection characteristics due to permanent deformation of the bimetal 26. Problems such as thermal damage of the bimetal 26 and parts contacting the bimetal 26 do not occur.

Therefore, according to the overcurrent trip device 4 of the present embodiment, since no time delay occurs in the operation of the overcurrent trip device 4 at the time of overcurrent, the interruption performance can be improved.
In addition, since the overcurrent tripping device 4 is configured by combining the extension plate 27 and the bimetal 32, the present embodiment is not a single member made of only a relatively expensive bimetal, so that the manufacturing cost of the circuit breaker is reduced. Reduction can be achieved.

Further, since the extension plate 27 is made of a metal plate made of an inexpensive single metal material or a synthetic resin plate, the manufacturing cost of the circuit breaker can be further reduced.
In addition, since the upper part of the bimetal 26 and the lower part of the extension plate 27 of the present embodiment are integrated with a simple structure by caulking and fixing with the rivets 31b, the manufacturing cost of the circuit breaker can be further reduced. it can.

  The bimetal may be a trimetal. In the above embodiment, the upper part of the bimetal 26 and the lower part of the extension plate 27 are integrated by caulking and fixing with a rivet 31b, but as shown in FIGS. 6 (a) and 6 (b), the lower part of the extension plate 27 is integrated. The engaging claws 33a and 33b projecting in a direction perpendicular to the surface of the extension plate 27 that contacts the bimetal 26 are formed, and the engaging holes 34a and 33b into which the engaging claws 33a and 33b enter the upper part of the bimetal 26, respectively. 34b is formed and the engaging claws 33a and 33b inserted into the engaging holes 34a and 34b are caulked, so that the rivet 32 is not necessary even if the upper part of the bimetal 26 and the lower part of the extension plate 27 are integrated. Furthermore, the manufacturing cost of the circuit breaker can be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Case, 2 ... Cover, 2a ... Middle cover, 2b ... Top cover, 3 ... Arc-extinguishing chamber, 4 ... Overcurrent tripping device, 5 ... Fixed contact, 5a ... Power supply side terminal, 5b ... Fixed contact, 6 ... movable contact, 6a ... movable contact, 7 ... holder, 8 ... lead wire, 9 ... relay conductor, 9a ... load side terminal, 9b ... lower flat plate portion, 9c ... rising plate portion (heater), 9d ... upper flat plate portion DESCRIPTION OF SYMBOLS 10 ... Electric wire connection board, 15 ... Opening / closing mechanism, 16 ... Handle, 17 ... Handle lever, 18 ... Upper toggle, 19 ... Lower toggle, 20 ... Latch, 21 ... Toggle link mechanism, 22 ... Latch receptacle, 23 ... Intermediate latch , 24 ... Trip bar, 25 ... Toggle pin, 26 ... Bimetal, 27 ... Extension plate, 27a ... Flat plate portion, 27b ... Bending portion, 28 ... Adjustment screw, 29 ... Fixed magnet, 30 ... Armature, 31a, 31b ... Rivet 33a, 33b ... engaging claws, 34a, 34b ... engaging hole

Claims (3)

An overcurrent tripping device for a circuit breaker that performs an opening operation of the switching mechanism by contacting a trip bar of the switching mechanism,
Between the heater provided in the current path and the trip bar, a base end portion is fixed to the heater, a tip end portion is fixed to the tip end portion of the bimetal, and a free end Comprises an extension plate located in the vicinity of the trip bar,
Overcurrent flows through the current path, the heater generates heat, the tip of the bimetal heated by the heat generation of the heater is bent and deformed, and the free end of the extension plate is displaced along with the deformation of the tip of the bimetal. An overcurrent tripping device for a circuit breaker, which contacts the trip bar.   2. The circuit breaker overcurrent trip device according to claim 1, wherein the extension plate is a metal plate made of a single metal material or a synthetic resin plate.   The overcurrent tripping device for a circuit breaker according to claim 1 or 2, wherein a tip end portion of the bimetal and the extension plate are fixed by caulking.

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