JPH0419938A - Circuit breaker - Google Patents

Abstract

PURPOSE:To further ensure connection by electrically connecting a movable contact and a connection conductor, fixed to a case, by sliding contact. CONSTITUTION:A movable contact 32 is soldered to the end of a movable contact 31 made of a copper plate. A connection conductor 33 is integrated with a bimetal 9a. A pair of arms 33a are bent and formed on the conductor 33, and the end portion of the movable contact 31 is elastically sandwiched between, being the arms 33a brought into sliding contact with the arms 33a. A shaft 35 is passed through the common hole of the contact 31 and the arms 33. A recessed portion 36a is formed in a resin holder 36 and both ends of the shaft 35 are fitted in a wall. In this case, a compression spring 37 is inserted into the shaft 35 on both sides of the arms 33a. A closing shaft 38 connects the holder 36 to the holder of a pole on each side of the holder 36. The holder 36 is supported to a case via a shaft 38 in such a manner as being freely put in a turning movement. By this constitution a circuit breaker of high reliability and high breaking performance is obtained. Each sliding contact face is coated with a composite material of Ag and C whereby good electric conduction is maintained for a long period of time.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a small circuit breaker such as a molded circuit breaker or an earth leakage breaker, and more specifically, the present invention relates to a small circuit breaker such as a molded circuit breaker or an earth leakage breaker, and more specifically, it electrically connects a movable contact that moves to open and close by being driven by an opening and closing mechanism and a connecting conductor that is fixed to a case. Concerning the configuration for connecting.

[Conventional technology]

Figures 16 and 17 show a conventional three-pole circuit breaker (
This is a vertical cross-sectional view of the center pole part of a molded case circuit breaker).
FIG. 16 shows a closed circuit state, and FIG. 17 shows an open circuit state. In Fig. 16, 1 is a resin molded case, 2 is a cover, 3 is a fixed contact that is integrated with the terminal 3a on the power supply side and is fastened to the case 1 with a screw (not shown), and 4 is attached to the fixed contact 2. 5 is a movable contact rotatably held on a resin molded holder 6 via a shaft 7; 8 is a movable contact provided on the movable contact 5 facing the fixed contact 4; , 9 is a bimetal 9a, and L welded to this
An overcurrent exception device consisting of a fixed conductor 9b having a shape, a fixed magnet 9C disposed surrounding a bimetal 9a, and an armature 9d rotatably provided opposite the bimetal 9a;
10 is a connecting conductor which is overlapped with the fixed conductor 9b and fastened to the case 1 with screws 11; 12 is a flexible conductor whose both ends are connected to the movable contact 5 and the connecting conductor 10 by brazing, and 13 is a screw 14. The load-side terminal 15 fastened to the case 1 is a flexible conductor whose both ends are connected to the bimetal 9a and the terminal 13, respectively. Although not described in detail, 16 is an opening/closing mechanism that opens and closes the movable contact 5 together with the holder 6, and is normally latched by a tripping mechanism 18 including a crossbar 17 extending across various parts. Reference numeral 19 denotes a handle lever supported so as to be swingable in the left-right direction in the figure, and an opening/closing spring 20 is disposed between it and the opening/closing mechanism 16.
The rope is handed over, and the operating handle 21 is attached to the head. A contact spring 22 is inserted between the holder 6 and the movable contact 5, and urges the movable contact 5 toward the fixed contact 3. Left and right movable contacts (not shown) are arranged side by side on the left and right sides of the movable contact 5, and these movable contacts are also rotatably held by a holder similar to the illustrated holder 6 via a shaft. These three-pole holders are connected to each other by an integrally molded opening/closing shaft (not shown), and the whole is rotatably supported in a bearing groove of a correlative partition (not shown) of the case 1 via the opening/closing shaft. Note that 23 is an arc extinguishing chamber arranged surrounding the movement locus of the movable contact 8. In such a configuration, current flows from the fixed contact 3 to the fixed contact 4, the movable contact 8, the movable contact 5, the flexible conductor 12,
It flows to the terminal 13 via the connecting conductor 10, the fixed conductor 9b, the bimetal 9a, and the flexible conductor 15. In that case, if an overload current of about 10 times the rated current flows, the bimetal 9
a curves to the left in the figure and pushes the cross spar 17. As a result, the latch of the switch 1116 by the tripping mechanism 18 collapses, and the movable contact 5 is sprung up by the force of the switch spring 20, rotates together with the holder 6, and quickly opens and separates from the fixed contact 3. . At this time, the arc generated between the fixed contact 4 and the movable contact 8 is drawn into the arc extinguishing chamber 23 by electromagnetic force, where it is cooled and extinguished. Furthermore, when a large current such as a short circuit current flows, the fixed magnet 9c attracts the armature 9d, and the bimetal 9b
The cross spar 17 is instantly struck without waiting for the curve of the movable contact 5 to open. Further, as shown in FIG. 17, when the operation handle 21 is opened to the right in the figure, the opening/closing mechanism 16 remains latched, and the movable contact 5 is also flipped up by the spring force of the opening/closing spring 2o, as shown in the figure. Open as shown.

[Problem to be solved by the invention]

Now, in the conventional circuit breaker described above, the movable contact 5 that is driven by the opening/closing mechanism 16 to open and close and the connecting conductor 1o fixed to the case 1 are electrically connected via the flexible conductor 12. has been done. The flexible conductor 12 is generally made of thin copper wire bundled into small bundles. However, such a configuration has the following drawbacks. (]) The flexible conductor 12 also oscillates as the movable contactor 5 opens and closes, but if the separation distance of the movable contactor 5 is increased, this oscillation also increases, and the flexibility due to the accumulation of metal fatigue increases. There is a risk of disconnection of the conductor 12. (2) In order to prevent disconnection of the flexible conductor 12, it is necessary to provide a space for accommodating the flexible conductor 12 so that the deformation of the flexible conductor 12 during the swinging described above is not unreasonable. Therefore, the rated current increases and the visible conductor 1
If 2 becomes thicker, the case 1 becomes larger to accommodate it, making it difficult to downsize the circuit breaker. (3) The movable contactor 5 receives a resistance force from the flexible conductor 12 during the opening/closing movement, and this resistance force changes depending on the state of connection between both ends of the flexible conductor 12 and the mating member and the number of times the circuit breaker is opened and closed. Under the influence of this resistance force, variations occur in the contact pressure between the contacts 4 and 8 and the opening/closing speed of the movable contact 5. SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit breaker that eliminates the above-mentioned drawbacks by electrically connecting a movable contact and a fixed-side connecting conductor without using a flexible conductor. be. Another object of the present invention is to provide a circuit breaker in which the electrical connection is made more reliable. A further object of the present invention is to provide a circuit breaker in which the movable contact can be easily attached to the holder. Furthermore, it is an object of the present invention to provide a circuit breaker in which the life of the electrical connection portion is extended.

[Means to solve the problem]

In order to achieve the above object, the present invention has a movable contact that is held in an insulating holder that is rotatably supported on a case via an opening and closing shaft, and that this movable contact is driven by an opening and closing mechanism to In a circuit breaker that opens and closes around the opening and closing shaft together with a holder, a movable contact and a connecting conductor fixed to a case are electrically connected by sliding contact. In order to make the above-mentioned sliding contact, a pair of arms are formed opposite to the connecting end of the connecting conductor with the movable contact, the movable contact is sandwiched between the arms, and the arms are pressed against the side surface of the movable contact. It is preferable to provide springs on both sides. In that case, by providing a portion in the vicinity of the contact portion of the arm of the connection conductor with the movable contactor, the opposing interval is narrower than the contact portion, so that the electromagnetic force can be used more effectively and the contact pressure can be increased. The movable contact is attached to a mounting bracket made of a thin plate formed by cutting and bending an engagement piece, and the mounting bracket is press-fitted into a holder having a recessed portion having an engagement step corresponding to the engagement piece. If the holder holds the holder, assembly becomes easy. In the above-mentioned sliding contact, the contact portion is heated due to frictional heat due to sliding and zigzag heat due to current flow, but copper and copper alloy, which are normal conductive materials, are oxidized due to the heating. Contact resistance increases and current carrying capacity decreases. The usual means to prevent such oxidation and maintain stable current carrying capacity of the sliding contact area is to apply silver (Ag) to the sliding contact surface.
It is possible to apply plating. However, according to experiments conducted by the inventors, repeating no-load opening and closing (in this case, the contact part slides in a non-energized state)
The Ag plating layer is worn away and the copper base is exposed, and when a large current is cut off (in this case, the contact portion slides while energized), the Ag plating layer melts and the copper base is exposed as well. Therefore, in the present invention, the sliding contact surface of at least one of the movable contactor and the connecting conductor is coated with a composite material of silver and carbon. Furthermore, if the temperature of the sliding contact between the movable contact and the connecting conductor increases due to a large current at a constant rate, and there is a concern that phenomena such as softening, melting, or welding may occur, the movable contact and the connecting conductor may It is preferable to connect the conductor to the sliding contact between them by a lead wire so as to form a parallel circuit.

[For use]

By bringing the movable contact and the connecting conductor into direct sliding contact to electrically connect them, there is no need for a flexible conductor, and there is no need to secure a space for housing it in the case. In that case, the braking torque that acts on the movable contact from the connecting conductor as the movable contact opens and closes (rotational motion around the connecting shaft that connects the holder) is caused by the frictional force of the sliding contact surface and the small area of contact. The effect on the contact pressure and opening/closing speed of the movable contact provided at the tip of the movable contact, which is much longer than this rotation radius, is small. Further, since the frictional force hardly changes unless clouding or welding occurs on the sliding contact surface, the variation in the braking torque is also small. By forming a pair of arms facing the connecting end of the connecting conductor with the movable contact and sandwiching the movable contact, the contact area will be doubled compared to when contact is made only on one side of the movable contact. Furthermore, the electromagnetic attraction forces that act on each other between the currents flowing in the same direction through the opposing arms of the connecting conductor press the arms against the movable contact, increasing the contact pressure. In that case, if a part is provided in the vicinity of the contact part of the arm of the connecting conductor with the movable contact, the facing distance is narrower than the contact part, so that the above-mentioned electromagnetic attraction force can be used more effectively and the contact pressure can be increased. can. Further, if springs are provided on both sides of the movable contact for pressing the arms against the side surfaces of the movable contact, constant contact pressure can be ensured. As a structure for holding the movable contact in the holder, the movable contact is attached to a mounting bracket made of a thin plate formed by cutting and bending an engagement piece, and the mounting bracket is attached to a recessed part having an engagement step corresponding to the engagement piece. By press-fitting the movable contact into the formed holder, the movable contact can be attached to the holder in one motion, which simplifies the assembly work. By the way, according to the inventors' considerations, when the movable contact and the connecting conductor are brought into sliding contact, the reason why the Ag plating wears out and the copper base is exposed due to no-load switching is due to the movable contact and the connecting conductor. This is because the Ag plating layers on both sides of the conductor are coated. In addition, the copper substrate is exposed when a large current is cut off.
This is because the plating layers weld to each other, and if the welded part breaks during the sliding process, the surface of that part will become rough, the electrical contact will be poor, and the heat generated by electricity will increase, making it easier to melt and weld. . Such problems can be solved by applying a coating treatment on the sliding contact surface made of a composite material in which carbon (C) grains are dispersed in a silver matrix instead of Ag plating. As is well known, carbon has excellent lubricating properties, but it is completely incompatible with silver. Therefore, the silver-carbon composite material can prevent warping during no-load opening and closing, and at the same time, it is less likely to weld together even if it melts due to heat generation when a large current is applied, and in both cases, the sliding contact surface is smooth. It is possible to maintain stable current carrying capacity. In addition, so as to form a parallel circuit for the sliding contact part,
By connecting the movable contact and the connecting conductor with a lead wire, when a large current such as a short circuit current flows, this current is divided between the sliding contact and the lead wire, reducing the thermal load on the sliding contact. can be reduced, and the current capacity can be increased accordingly.

【Example】

Hereinafter, the present invention will be explained in detail based on the drawings. In addition,
In the drawings showing the embodiment, parts that are substantially the same as those in the conventional example are given the same reference numerals. First, FIG. 1 is a perspective view of a movable contact portion of a central pole of a first embodiment which shows the principle of the present invention. The movable contact 31 is formed by punching a copper strip into a predetermined shape, and has a movable contact 32 brazed to its tip. The connecting conductor 33 is integrally formed with the bimetal 9a, and is fastened to the case 1 by a screw (not shown) passing through the hole 34. In this case, the fixed conductor 9b (FIG. 16) for fixing the bimetal 9a is unnecessary. Connection conductor 3
A pair of arms 33a facing each other are formed by bending.The arms 33a elastically sandwich the ends of the movable contact 31 and come into sliding contact with the movable contact 31 which makes an opening/closing motion. Although not shown, a common hole is bored in the movable contactor 31 and the arm 33a, and the shaft 35 is inserted therethrough as shown. On the other hand, the resin molded holder 36 is formed with a recess 36a into which the movable contact 31 is received, and both ends of the shaft 35 are fitted into the walls at both ends of the recess 36a. Further, at this time, compression springs 37 made of coil springs are inserted into the shaft 35 on both sides of the arm 33a, and press the inner wall surface of the arm 33a against the side surface of the movable contact 31 between the arm 33a and the holder 36. Reference numeral 38 denotes an integrally formed opening/closing shaft that connects the holder 36 and right and left holders (not shown) on both sides thereof.The holder 36 is rotatably supported by the case 1 via the opening/closing shaft 38. When the movable contact 31 is driven by the opening/closing mechanism 16, it opens and closes around the connecting shaft 38, and the left and right movable contacts similarly held in a holder (not shown) also open and close in unison. The overcurrent tripping device 9 of the conventional example shown in FIG. 16 and the embodiment shown in FIG. There is an indirect heating type that transfers heat to bonded bimetals. FIG. 2 shows a basic embodiment of a circuit breaker using such an overcurrent tripping device, in which the connecting conductor 33 is constructed integrally with the heater conductor 39. The rest of the configuration is the same as that of the embodiment shown in FIG. 1, so the explanation will be omitted. 3 and 4 are longitudinal sectional views of the circuit breaker equipped with the movable contact 31 and the connecting conductor 33 shown in the embodiment of FIG. 1, with FIG. 3 showing the closed circuit state, and FIG. indicates an open circuit state. In the figure, the current flowing from the fixed contact 3 to the movable contact 31 via the fixed contact 4 and the movable contact 8 is directly connected to the connecting conductor 33 due to sliding contact between the side surface of the movable contact 31 and the inner wall surface of the arm 33a. Flow, bimetal 9a, flexible conductor 15
The terminal 13 is reached through the terminal 13. A contact spring 40 is a compression spring inserted between the movable contact 31 and the case 1, which urges the movable contact 31 toward the fixed contact 3 and applies appropriate contact pressure. . Other configurations,
Since the operation is the same as the conventional example, the explanation will be omitted. Next, FIGS. 5 to 9 show a third practical embodiment of the present invention. This will be explained in detail below. First, Fig. 5 shows a combination of a movable contact and a connecting conductor that makes sliding contact with the movable contact, and Fig. 5 (A)
is a plan view with the upper plate of the mounting bracket 44 (described later) partially removed, (B) is a side view with the front side plate of the mounting bracket 44 partially removed, and (C) is a rear view. . In the figure, 41 is a movable contact punched out from a copper strip in the shape shown, 42 is a movable contact brazed to its tip, and 43
Reference numeral 44 designates a connecting conductor formed by bending a copper plate; reference numeral 44 designates a mounting bracket formed by bending a thin steel plate with high springiness into a gate shape; and reference numeral 45 designates a current limiting latch made of a steel plate constituting a current limiting mechanism. The connecting conductor 43 has a pair of opposing arms 43b raised from a base 43a which is fastened to the circuit breaker case l (Fig. 3) with a screw passing through a hole 46.
is bent into the shape shown in the figure to a distance slightly narrower than the plate thickness of the movable contact 41, and is pushed out to elastically sandwich the rear end of the inserted movable contact 41, and is in sliding contact with the side surface of the movable contact 41. It looks like this. Further, as shown in FIG. 5(A), a hole 46 is provided in the base 43a from the left end of the figure along the center line.
A slit 43c is cut in front of the arm 43.
b is designed to be easily elastically deformed in the lateral direction. A common through hole is formed in the sliding contact portion between the movable contactor 41 and the arm 43b, and the shaft 47 is inserted through a slight gap. Then, a spring 49 made of a compression spring is inserted into the shaft 47 with a washer 48 in between on both sides of the arm 43b.
Both ends of 7 are joined to the side plates of the mounting bracket 44 by caulking. As a result, the movable contact 41 can be rotated around the shaft 47, and the arm 43b can be rotated around the movable contact 41 by the spring 49.
1 and a suitable contact pressure is applied. Here, FIG. 9(A) is a side view of the connecting conductor 43, and FIG. 9(B) is a side view of the connecting conductor 43.
) is a sectional view taken along the line BB. As shown in FIG. 9, an annular convex portion 43c is formed on the inside of the arm 43b surrounding the through hole 50 through which the shaft 47 passes, and comes into contact with the movable contact 41 at this portion. As a result, the contact range between the movable contact 41 and the arm 43b is specified within the range of a small average radius, and the braking torque applied to the movable contact 41 due to frictional force can be suppressed to a small level, the contact pressure is increased, and the opening/closing movement is further suppressed. Even after repeated contact, the contact surface remains constant and stable contact is maintained. Returning again to FIG. 5, a current-limiting latch 45 is rotatably supported on the mounting bracket 44 by another shaft 51 having both ends fixed to its side plate in the same way as the shaft 47. Current limiting latch 4
Reference numeral 5 denotes a bifurcated hard member bent into a U-shape at the part where the shaft 51 passes through, and has a nearly perpendicular normal surface 45a with an inflection point (■) in between on the side opposite to the shaft 47; A current limiting surface 45b is provided which is inclined counterclockwise in the figure. In the normal opening/closing state, the current limiting latch 45 engages with the current limiting pin 52 implanted in the movable contact 41 so as to protrude left and right at its normal surface 45a, and its upper end and the upper part of the mounting bracket engage with each other. The bridge is pressed against the current limiting pin 52 by a pair of left and right current limiting springs 53. On the other hand, the movable contact 41 is connected to the shaft 4 via the current limiting bottle 52 by the current limiting spring 53.
7, a torque is applied to rotate it in the counterclockwise direction of FIG. 5(B). This torque is applied when the movable contact 42 is connected to the fixed contact 4 when installed in a circuit breaker as described later.
Generates contact pressure that presses toward. In other words, the current limiting spring 53 has the function of a contact spring. Engagement pieces 44a and 44b are formed by cutting and bending on the upper plate and the lower side plate of the mounting bracket 44, respectively, so as to project outward. Illustrated movable contactor 41 and connection conductor 43
The assembly with the engagement piece 44a. 44b, and the holder will be explained next. FIG. 6 is a plan view of the holder, and FIG. 7 is a cross-sectional view thereof taken along the line ■-■. As shown in FIG. 6, various holders 54 made of molded resin are connected to each other by an opening/closing shaft 55. As shown in FIG. 55a is an interphase barrier formed integrally with the opening/closing shaft 55. The holder 54 is rotatably supported by a connecting shaft 55 fitted into a bearing groove (not shown) formed in the interphase wall 1a of the case 1, indicated by a chain double-dashed line. Note that cutouts 54a for connecting links of the opening/closing mechanism are formed on the left and right side surfaces of the holder 54 of the central bridge. The assembly of FIG. 5 is mounted in holder 54 as shown in FIG. That is, the holder 54 is formed with a recess 56 into which the assembly is inserted from the back side, and a window 57 is formed in the front wall through which the movable contact 41 is inserted so as to be able to open and close. Mounting brackets 44 are installed on the left and right walls of the recess 56.
A fitting surface 56a is formed according to the width of the front edge 56.
b is shaped like the outline of the front surface of the mounting bracket 44. Further, a stepped portion 5 is provided on the ceiling wall of the recessed portion 56 corresponding to the engaging piece 44a.
6c, and furthermore, a step portion 56d corresponding to the engagement piece 44b is provided on the left and right walls along the lower part of the front edge 56b of the fitting surface. The engagement piece 44a of the mounting bracket 44 is attached to such a holder 54.
When the assembly shown in FIG. 5 is pushed in while elastically deforming the fittings 44b and 44b inward, it stops when the front surface of the mounting bracket 44 abuts the front edges 56b of the fitting surfaces of the left and right walls, and at the same time, the engaging pieces 44a and 44b elastically deform. They are returned by force and engaged with the stepped portions 56c and 56'd, respectively, and are fixed in the state shown in FIG. 7. FIG. 8 is a perspective view showing the holder 54 to which the movable contact 41 is fixed in this manner. Furthermore, 54
b is a through hole into which a bottle connecting links of the opening/closing mechanism is inserted. FIG. 14 is a longitudinal sectional view of the central part of the circuit breaker incorporating the holder 54 holding the assembly shown in FIG. 5, and shows the circuit breaker in a closed state. The base portion 43a of the connecting conductor 43 overlaps the bimetal 9a and is fastened to the case 1 together. In the illustrated state, the movable contact 41 is pressed by the fixed contact 3 and slightly rotates around the shaft 47 in the clockwise direction in the figure, thereby causing the current limiting latch 45 to limit the current through the current limiting bottle 52. It is rotated counterclockwise around a shaft 51 against a spring 53. As a result, the movable contactor 41 receives a rotational moment from the current limiting spring 53 in the counterclockwise direction in the drawing, thereby obtaining contact pressure between the contacts 4 and 42. When the holder 54 and the movable contact 41 perform opening and closing movements,
The opening/closing shaft 55 rotates around the axial center point A in FIG.
The shaft 47 rotates around the point A with a radius r. Therefore, as shown in FIG. 9(A), the through hole 50 through which the shaft 47 is inserted is made into an elongated hole so as not to impede its rotation. The reason why the eight axial centers supporting the movable contactor 41 are shifted from the axial center point A of the opening/closing shaft 55 is that the movable contactor 41 is moved in the front-rear direction (the first
This is to remove the oxide film on the contact surface by slightly moving it in the left-right direction in Figure 4 and sliding between the contacts 4 and 42. Next, the current limiting and shutting off by the action of the current limiting latch 45 will be explained. In FIG. 14, the fixed contact 3 is provided with a conductor portion 3b located parallel to the conductor of the movable contact 5, and the current flowing through the conductor portion 3b and the movable contact 31 via the contact 4.42 is indicated by an arrow. The directions are opposite to each other. Therefore, the movable contactor 31 is always subjected to force in the direction of separation due to the electromagnetic repulsion force acting between these currents. When a large current such as a short-circuit current flows through such a circuit breaker, the movable contact 41 receives an extremely large driving force, resists the force of the current-limiting spring 53, pushes away the current-limiting latch 45, and closes the shaft 4.
Rotate clockwise around 7. As a result, the current-limiting bottle 52 slides on the normal surface 45a of the current-limiting latch 45, crosses the inflection point (3), and rides on the current-limiting surface 45b. The angle between the normal surface 45a and the current limiting surface 45b in the current limiting latch 45 is determined based on the spring force of the current limiting spring 53 when the current limiting bottle 52 is in contact with the normal surface 45a.
The force acting on the current-limiting bottle 52 acts to rotate the movable contact 41 counterclockwise in the figure, and when the current-limiting bottle 52 moves to the current-limiting surface 45b, the force causes the movable contact 41 to rotate clockwise. It is set so that it rotates in the direction. Therefore, as described above, when the movable contact 41 rotates beyond a certain opening distance and crosses the inflection point (■), the movable contact 41 is rotated by the rotational force due to the current limiting spring 53 in addition to the electromagnetic repulsive force described above. In response to this, the opening/closing mechanism 16 quickly opens and closes prior to opening due to the operation of the opening/closing mechanism 16. As a result, the arc voltage increases rapidly, and so-called current-limiting interruption is performed. FIG. 7 shows the result of such current limiting interruption. The current limiting latch 45 is reset as shown in FIG.
When the tripping operation of the opening/closing mechanism 16 is performed following the current limiting operation by a command from the overcurrent disconnection device 9, the movable contact 41 is attached to the stopper 2a integrally formed in the cup \-2.
This is done by forcibly rotating the holder 54 in the clockwise direction in the figure while the current limiting bottle 52 crosses the inflection point V in the opposite direction and engages with the normal surface 45a again. Figure 10 is an explanatory diagram that clarifies the force relationship during the current limiting operation described above. Figure 10 (A) shows the closed state of the circuit breaker, and Figure 10 (B) shows the state immediately after opening. It shows. Further, FIG. 11 is a diagram showing the relationship between the torque acting on the movable contact 41 based on the spring force of the current limiting spring 53 during the current limiting operation and the separation distance of the movable contact 41. First, in FIG. 10(A), in the closed circuit state, due to the spring force P of the current limiting spring 53 and the distance L1 from the bottle 52,
A torque of P+xL acts on the current limiting latch 45. This torque is applied to the bottle 5 in the almost vertical normal plane 45a.
Apply a PgO force to the current limiting bottle 52 at a distance from 1 to L2 (P, x Ll = F)2XL2), and this force P
2 is the distance from the current-limiting bottle 52 to the axis 47, and by J,
A torque of Pz Xi3 is applied to the movable contact 41 in a counterclockwise direction. This torque creates contact pressure between the movable contact 42 and the fixed contact 4. On the other hand, in the state shown in FIG. 10(B) where the inflection point ■ has been exceeded, the torque acting on the current limiting latch based on the spring force P3 from the current limiting spring 53 causes a distance L4 from the bottle 51 on the current limiting surface 45b. A force P4 is generated on the current limiting bottle 52 at the point . This force P4 is caused by the axis 4 due to the inclination angle of the current limiting surface 45b.
7 to the shaft 47, a clockwise torque of Pa Xi, . FIG. 11 shows that the current limiting bottle 52 is moved to the normal surface 45 due to electromagnetic repulsion.
This figure shows how the direction of the torque acting on the movable contact 41 is reversed as soon as it slides on the point a and crosses the inflection point ■.
The positive side of the torque represents counterclockwise direction, and the negative example represents clockwise direction. By the way, when a large current flows and the electromagnetic repulsion force exceeds the contact pressure, it is desired that the torque reversal occurs in as short a time as possible. In order to do this, it is necessary to suppress the increase in ten-direction torque while the current limiting pin 52 moves from the closing position to the inflection point (2), and to reduce the engagement between the current limiting pin 52 and the current limiting latch 45 in FIG. 10(A). . need to be minimized as much as possible. In order to reduce the increase in torque in the ten directions, the angular difference between the normal surface 45a and the current limiting surface 45b may be reduced. However, if this angular difference becomes small (when the direction of the force P2 shifts toward the shaft 47 side, the distance L3 also becomes small, and the contact pressure decreases. Also, if the above-mentioned engagement amount Lb becomes too small, the contact bounce occurs when the circuit breaker is closed). Therefore, there is a risk that the current limiting bottle 52 will exceed the inflection point. Therefore, in consideration of these balances, the angle of the normal surface 45a and the engagement amount L6 are adjusted.
Decide appropriately. In the case of a circuit breaker configured to separate the movable contact from the fixed contact using electromagnetic repulsion, simply deforming the contact spring will cause the reaction force of the contact spring to increase as the movable contact separates. Movement of the movable contact is inhibited. On the other hand, the illustrated current limiting mechanism has a large current limiting effect, for example, AC4
It has been confirmed that when a current of 60V and 42kA is interrupted, the peak value of the passing current decreases from about 33kA in the conventional case to about 26kA. Next, FIG. 12(A) shows the main parts of the movable contactor 41 and the connecting conductor 43 which are in sliding contact, and FIG. 12(B) is an enlarged view of the B part. As shown in the figure, the current flows through several contact points P within the contact range. This current is the first
As shown by the arrow i in Fig. 2 (B), the current gathers toward the contact point P and diffuses as soon as it passes the contact point P, so the direction of the current is reversed before and after the contact point P, and the movable contact 41 and An electromagnetic repulsive force acts between the connecting conductor 43 and the arm 43b. The magnitude of this electromagnetic repulsion force F is calculated as follows, assuming that the current passing through one contact point P is 1 m (kA), and the number of contact points P is n. =
I to n). This electromagnetic repulsion force F1 increases at an accelerating rate as the current passing through the circuit breaker increases and therefore the current passing through each contact point P increases. As a result, the force of the spring 49 is reduced and the number of contact points P is reduced, and the current passing through the remaining contact points P becomes excessive, creating a possibility that arcing or welding will occur at that part. . For this reason, when the movable contactor 41 and the connection conductor 43 are connected by sliding contact (surface contact), there is a limit to the applicable short circuit current rating. If the force of the spring 49 is increased in order to increase this limit value, a problem arises in that the frictional force increases and the normal opening/closing speed of the movable contact 41 decreases. As a means to solve this problem, Figures 5 (C) and 9
As shown in Figure (B), a portion 58 is provided in the vicinity of the contact portion of the arm 43b with the movable contact 41, where the opposing distance between the arms 43b is narrower than that of the contact portion. The effect will be explained below with reference to FIG. 12(A). Now, the length of the arm 43b at the above portion 58! , the opposing interval is S, and the current divided into each arm 43b is 1 (kA). Since the current I flows through each arm 43b in the same direction, the following electromagnetic attractive force F2 is generated between the arms 43b. Ru. Fz=2.04, ρ/S-1'' (k: constant) Therefore, if the above-mentioned interval S is determined so that this electromagnetic attractive force F2 is larger than the above-mentioned electromagnetic repulsive force F, the force of the spring 49 can be reduced to The applicable short-circuit current rating can be improved without increasing the current rating. Fig. 17 shows how the electromagnetic repulsive force F1 and the electromagnetic attractive force F2 change with the short-circuit current passing through the circuit breaker. , is a force obtained by the elasticity of the contact force spring 49 and the connection conductor 43 in the figure.In addition, as shown in FIG. By increasing the distance between the arm 43b and the movable contact 41 and increasing the interval between the currents flowing in opposite directions before and after the contact portion, the electromagnetic repulsion force F1 is increased.
acts to reduce the Furthermore, by coating the sliding contact surface of at least one of the movable contactor and the connecting conductor with a composite material of silver (Ag) and carbon (C), it is possible to prevent the circuit breaker from repeating no-load opening/closing or interrupting large currents. This prevents warping and welding of the contact surface caused by this, and greatly improves current carrying performance. Therefore, the test results will be explained below regarding an experimental example in which the movable contactor 41 and the connecting conductor 43 having the structure shown in FIG. 5 were subjected to the above coating treatment. First, the movable contact 41 and the connection conductor 43 are each
A coating of -6% C (vol%) was electroplated to a thickness of 7 μm. At that time, the major diameter of the 0 grains dispersed in Ag is 0.5 to 2.
A piece with a short diameter of 0.2 to 0.56 m0 was used (Experimental Example 1). Similarly, the movable contact 41 and the connecting conductor 43 are each
A coating of g-3% C (vol%) was electroplated to a thickness of 7 μm. At that time, the major diameter of the 0 grains dispersed in Ag is 0.8~
Pieces with a diameter of 5 μm and a short axis of 0.3 to 1 μm were used (
Experimental example 2). In addition, as a comparative example, a similar movable contact and a connecting conductor with 7 μm Ag plating were prepared. Table 1 shows the results of a no-load switching test and a large current interrupting test conducted by incorporating these movable contacts and connecting conductors into a circuit breaker. According to this, it can be seen that the copper substrate is less likely to be exposed in the Ag-C composite material plated plate compared to the normal plated plate. Although two examples were shown in the above experimental examples in Table 1, since the effects of this invention depend on the properties of C, the size of 0% and 0 grains is not limited to these. Furthermore, the ease of thickening and melting of the sliding contact portion is also influenced by the width of the contact portion and the surface pressure, so the size of 0% and 0 grains is determined by taking these factors into consideration. However, although C has conductivity, the electrical resistance is lower than that of Ag.
It is several hundred to several thousand times larger. Therefore, 0%
or large zero that penetrates the plating thickness.
The use of grains is undesirable because it increases the heat generation of the sliding contact and raises the temperature of the terminals of the circuit breaker. Although the above experimental example shows the case of an electroplated film, it is important that the film is a composite material of Ag and C, and the film forming method is not limited to electroplating. Forming a film is also effective. In that case, the other part is A
It is preferable to use G plating, but since C has an anti-oxidation effect, a certain degree of current-carrying properties can be obtained even if copper is used as is. Note that the above coating does not need to be applied to the entire surface of the conductor, and may be formed only to the sliding contact surface. Furthermore, fine hard particles such as SiC, WCSZrB, Alz are added to Ag-C as third particles.
O3, Zr0z, CrzO,, Ti0z, Rz
Os, Thoz, YzO3, Mo5s, WzC,T
By dispersing particles such as iC, B-C, CrBz, etc., the hardness of the entire coating can be increased and a contact portion that is less likely to wear out and has a longer life can be constructed. Finally, FIG. 15 shows a fourth embodiment of the present invention in which a movable contact and a connecting conductor that makes sliding contact with the movable contact are further connected by a lead wire, and FIG. 15 (A) shows the movable contact portion. FIG. 2B is a plan view, FIG. 1B is a side view, and FIG. 1C is a rear view. In the figure, 59 indicates the movable contact 41 and the connecting conductor 4.
3, one end of which is attached to the lower surface of the rear end of the movable contact 41, and the other end is attached to the base 43a of the connecting conductor 43. It is being carried out. As a result, the current flowing between the movable contactor 41 and the connecting conductor 43 is almost divided between the sliding contact portion and the lead wire 59, and the thermal loss of the sliding contact portion when a large current such as a short circuit current flows. The load is halved, and the limit current value of the circuit breaker as a whole can be increased accordingly.

【Effect of the invention】

According to this invention, the movable contact and the connecting conductor can be electrically connected without using a flexible conductor, and the circuit breaker has excellent reliability and high breaking performance. becomes possible. Further, in this case, by applying a film treatment made of a composite material of silver and carbon to the sliding contact surface of the movable contactor or the connecting conductor, a good current conduction state can be maintained for a long period of time. Furthermore, if necessary, part of the current in the sliding contact portion is shunted to the lead wire,
It is possible to increase the current capacity.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a movable contact portion of a first embodiment of the invention, FIG. 2 is a perspective view of a movable contact portion of a second embodiment of the invention, and FIG. 3 is a perspective view of a movable contact portion of a second embodiment of the invention. FIG. 4 is a vertical cross-sectional view of the center pole portion of a circuit breaker with a movable contact portion in a closed state, FIG. 4 is a vertical cross-sectional view of the center pole portion in an open state, and FIG. A plan view of the movable contact portion of FIG. 5 (B
) (A side view of the main body, FIG. 5(C) is a rear view thereof, FIG. 6 is a plan view of the holder that holds the movable contact portions shown in FIGS. 1 to 5, and FIG. 8 is a perspective view of the movable contact portion of FIG. 5 attached to the holder of FIG. 6, FIG. 9(A) is an enlarged side view of the connecting conductor in FIG. 5, FIG. 9(B) is a cross-sectional view along the line B-B,
FIG. 10(A) is a diagram explaining the force relationship between the current limiting latch and the current limiting bottle in the closed circuit state, FIG. 10(B) is a diagram also explaining the force relationship immediately after opening, and FIG. 11 12(A) is a diagram showing the relationship between the torque acting on the movable contact based on the current limiting spring and the opening distance of the movable contact, and FIG. 12(A) shows the force acting between the movable contact and the connecting conductor. For illustrative purposes, the rear view corresponds to FIG. 5(C), FIG. 12(B) is an enlarged view of part B, and FIG. 13 shows the magnetic repulsion force, magnetic attraction force, and short circuit at the contact part in FIG. 12. 14 is a diagram showing the relationship with current; FIG. 14 is a vertical cross-sectional view of the central pole portion of the circuit breaker equipped with the movable contact portion shown in FIG. 5 in a closed circuit state; FIG. FIG. 15 (B) is a plan view of the movable contact portion of Example 4
) is its side view, Fig. 15 (C) is its rear view, Fig. 16
The figure is a longitudinal sectional view of the central pole portion of a conventional circuit breaker in a closed state, and FIG. 17 is a longitudinal sectional view of the center pole portion of a conventional circuit breaker in an open state. DESCRIPTION OF SYMBOLS 1... Case, 16... Opening/closing mechanism, 31... Movable contact, 33... Connection conductor, 33a... Arm, 35...
...Spring, 36...Holder, 37...Opening/closing shaft, 41
... Movable contact, 43... Connection conductor, 43a...
Arm, 44... Mounting bracket, 44a, 44b... Engaging piece, 49... Spring, 54... Holder, 55... Opening/closing shaft, 56... Recess, 56c, 56d... Danbe, 59
···Lead. (A) (B) (A) (B) (A) (B) (A) (B) (A) (B) (A) (B) (A) (B) (A) (B) (A) (B) (B) Figure (A) (B) Figure 2 Figure

Claims (1)

[Claims] 1) A movable contact is held in an insulating holder rotatably supported by the case via an opening/closing shaft, and this movable contact is driven by the opening/closing mechanism to move along with the holder. A circuit breaker that opens and closes around the opening and closing shaft, characterized in that a movable contact and a connecting conductor fixed to a case are electrically connected by sliding contact. 2) In the circuit breaker according to claim 1, a pair of arms are formed opposite to the connecting end of the connecting conductor to the movable contact so as to sandwich the movable contact, and the arms are attached to a side surface of the movable contact. A circuit breaker characterized in that pressure-contacting springs are provided on both sides of the circuit breaker. 3) The circuit breaker according to claim 2, wherein a portion of the arm of the connecting conductor that contacts the movable contact is provided with a portion having a narrower facing distance than the contact portion. 4) In the circuit breaker according to any one of claims 1 to 3, the movable contact is attached to a mounting bracket made of a thin plate formed by cutting and bending an engagement piece, and the mounting bracket corresponds to the engagement piece. A circuit breaker characterized in that the movable contact is held in the holder by being press-fitted into a holder having a recessed portion having an engagement step. 5) In the circuit breaker according to any one of claims 1 to 4, the sliding contact surface of at least one of the movable contact and the connecting conductor is treated with a film made of a composite material of silver and carbon. A circuit breaker characterized by: 6) The circuit breaker according to any one of claims 1 to 5, in which the movable contact and the connecting conductor are arranged in a flexible manner so as to form a parallel circuit with respect to the sliding contact between them. A circuit breaker characterized by being connected by a lead wire.