JP2762704B2 - Circuit breaker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a small circuit breaker such as a wiring circuit breaker or an earth leakage circuit breaker, and more specifically, electrically connects a movable contact that is driven by an opening / closing mechanism to perform an opening / closing motion and a connection conductor fixed to a case. Related to a configuration for connection.

[Prior art]

16 and 17 are longitudinal sectional views of a central pole portion showing an example of a conventional circuit breaker (wiring breaker) having a three-pole configuration.
FIG. 16 shows a closed state, and FIG. 17 shows an open state. In FIG. 16, reference numeral 1 denotes a resin molded case, 2 denotes a cover, and 3 denotes a fixed contact formed integrally with the terminal 3a on the power supply side and fastened to the case 1 with screws (not shown). The fixed contact 5 provided is a movable contact that is rotatably held on a holder 6 of a resin molded product via a shaft 7. The movable contact 8 is provided on the movable contact 5 so as to face the fixed contact 4. , 9 is a bimetal 9a, an L-shaped fixed conductor 9b welded to the bimetal 9a, a fixed magnet 9c disposed around the bimetal 9a, and an overcurrent draw comprising an armature 9d rotatably provided opposite to the bimetal 9a. A disconnecting device, 10 is a connection conductor that 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 respectively connected to the movable contact 5 and the connection conductor 10 by brazing, and 13 is a screw. Load-side end fastened to case 1 at 14 The child 15 is a flexible conductor whose both ends are connected to the bimetal 9a and the terminal 13, respectively. Reference numeral 16 denotes an opening / closing mechanism which opens and closes the movable contact 5 together with the holder 6, although not described in detail. The opening / closing mechanism 16 is normally latched by a tripping mechanism 18 including a cross bar 17 extending over each pole. Reference numeral 19 denotes a handle lever which is swingably supported in the left and right directions in the figure. An open / close spring 20 is hung between the handle lever and the open / close mechanism 16, and an operation handle 21 is mounted on the head. Holder 6
A contact spring 22 is inserted between the movable contact 5 and the movable contact 5, and the movable contact 5 is urged toward the fixed contact 3. On the left and right sides of the movable contact 5, left and right pole movable contacts (not shown) are arranged side by side, 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 formed opening / closing shaft (not shown), and the whole is rotatably supported in a bearing groove (not shown) of the case 1 via the opening / closing shaft. Reference numeral 23 denotes an arc-extinguishing chamber arranged so as to surround the movement locus of the movable contact 8. In such a configuration, the current flows from the fixed contact 3
Fixed contact 4, movable contact 8, movable contact 5, flexible conductor 12,
Connection conductor 10, fixed conductor 9b, bimetal 9a, and flexible conductor
It flows to terminal 13 via 15. In this case, when an overload current of about 10 times the rated current flows, the bimetal 9a curves to the left in the figure and pushes the crossbar 17. This enables the trip mechanism
The latch of the opening / closing mechanism 16 is broken by 18, and the movable contact 5 is repelled by the force of the opening / closing spring 20, rotates together with the holder 6, and is quickly separated 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 the electromagnetic force, where it is cooled and extinguished. Further, when a large current such as a short-circuit current flows, the fixed magnet 9c attracts the armature 9d, hits the crossbar 17 instantly without waiting for the bimetal 9b to bend, and the movable contact 5
Is separated. As shown in FIG. 17, when the operating handle 21 is opened rightward in the figure, the movable contact 5 is repelled by the spring force of the opening / closing spring 20 while the opening / closing mechanism 16 remains latched. Separate as shown.

[Problems to be solved by the invention]

Now, in the conventional circuit breaker described above, the movable contact 5 driven by the opening / closing mechanism 16 to open and close and the connection conductor 10 fixed to the case 1 are electrically connected via the flexible conductor 12. Have been. In general, the flexible conductor 12 is formed by knitting a thin copper wire in small bundles. However, such a configuration has the following disadvantages. (1) The flexible conductor 12 also oscillates with the opening and closing movement of the movable contact 5, but when the separation distance of the movable contact 5 is increased, the oscillating becomes large, and the flexibility due to accumulation of metal fatigue is increased. There is a risk of the conductor 12 breaking. (2) In order to prevent disconnection of the flexible conductor 12, it is necessary to allow sufficient space in the accommodation space so that the deformation of the flexible conductor 12 at the time of the above-mentioned swinging will not be excessive. for that reason,
If the rated current becomes large and the flexible conductor 12 becomes thick accordingly, the case 1 becomes large for accommodating the same, making it difficult to miniaturize the circuit breaker. (3) The movable contact 5 receives a resistance force from the flexible conductor 12 at the time of the opening and closing movement, and this resistance force varies depending on the joining state between both ends of the flexible conductor 12 and the partner member and the number of times of opening and closing of the circuit breaker. Under the influence of the resistance, the contact pressure between the contacts 4 and 8 and the opening / closing speed of the movable contact 5 vary. Therefore, an object of the present invention is to provide a circuit breaker in which the above-mentioned disadvantages are eliminated by electrically connecting a movable contact and a fixed-side connection conductor without using a flexible conductor. is there. Another object of the present invention is to provide a circuit breaker in which the electrical connection is made more reliable in the circuit breaker. A further object of the present invention is to provide a circuit breaker in which the movable contact is easily mounted on the holder in the circuit breaker. Still another object of the present invention is to provide a circuit breaker having a longer life in the electrical connection portion in the circuit breaker.

[Means for Solving the Problems]

In order to achieve the above object, according to the present invention, a movable contact is held by an insulator holder rotatably supported by a case via an opening / closing shaft, and the movable contact is driven by an opening / closing mechanism to move the movable contact. In a circuit breaker that opens and closes around the opening / closing axis together with a holder, a movable contact and a connection conductor fixed to a case are electrically connected by sliding contact. Then, in order to perform the sliding contact, a pair of arms facing the connection end of the connection conductor with the movable contact is formed to elastically sandwich the movable contact, and the arm and the movable contact are formed. A shaft is inserted through a contact portion with the contact, the movable contact is rotatably connected to the arm, and a compression coil spring that presses the arm against a side surface of the movable contact is inserted into both ends of the shaft. It shall be. In this case, the contact pressure can be increased by providing more effective use of the electromagnetic force by providing a portion in the vicinity of the contact portion between the arm of the connection conductor and the movable contact, the gap being smaller than the contact portion. The movable contact is mounted on a mounting bracket made of a thin plate formed by cutting and bending an engaging piece, and the mounting bracket is press-fitted into a holder having a concave portion having an engaging step corresponding to the engaging piece. If the holder is held, assembly becomes easy. In the above sliding contact, the contact portion is heated due to frictional heat due to sliding and Joule heat due to energization, but copper or copper alloy, which is a normal conductive material, is oxidized due to the heating and the contact resistance increases. As a result, the current carrying capacity decreases. As a usual means for preventing such oxidation and stably maintaining the current carrying capacity of the sliding contact portion, silver (Ag) plating may be applied to the sliding contact surface. However, according to the experiments conducted by the inventors, when the no-load switching (in this case, the contact portion slides in a non-energized state) is repeated, the Ag plating layer is worn out, the copper base is exposed, and a large current is applied. (In this case, the contact portion slides in an energized state), the Ag plating layer is melted and the copper base is also exposed. Therefore, in the present invention, at least one of the sliding contact surfaces of the movable contact and the connection conductor is subjected to a coating treatment with a composite material of silver and carbon. Further, when the temperature of the sliding contact portion between the movable contact and the connection conductor rises due to a large current exceeding a certain level, and a phenomenon such as softening, melting or welding is concerned, the movable contact and the connection conductor are connected. May be connected to each other by a lead wire so as to form a parallel circuit with respect to a sliding contact portion therebetween.

[Action]

By making the movable contact and the connection conductor directly in sliding contact with each other and electrically connecting them, a flexible conductor becomes unnecessary,
There is no need to secure the accommodation space in the case. In this case, the braking torque acting on the movable contact from the connection conductor in accordance with the opening and closing movement of the movable contact (rotational movement about the connecting shaft connecting the holder) is determined by the frictional force of the sliding contact surface and the contact area of the small area. , And has a small effect on the contact pressure and switching speed of the movable contact provided at the distal end of the movable contact, which is much longer than this rotational radius. Further, the frictional force hardly changes unless the sliding contact surface is squeezed or welded, so that the fluctuation of the braking torque is small. If a pair of arms facing the connection end of the connection conductor with the movable contact is formed and the movable contact is sandwiched, the contact area is doubled as compared with a case where only one surface of the movable contact makes contact with the movable contact. Furthermore, the arms are pressed against the movable contact by the electromagnetic attraction force acting between the opposing arms of the connection conductor during the current flowing in the same direction, so that the contact pressure increases. . In that case, if a portion where the facing interval is smaller than the contact portion is provided in the vicinity of the contact portion of the arm of the connection conductor with the movable contact, the electromagnetic attraction force more effectively utilizes the electromagnetic attraction force to increase the contact pressure. it can. If springs are provided on both sides for pressing the arm against the side surface of the movable contact, a 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 engaging piece, and the mounting bracket is provided with a recess having an engaging step corresponding to the engaging piece. By press-fitting the formed holder, the movable contact can be mounted on the holder in one operation, and the assembling work is simplified. By the way, according to the considerations of the inventors, when the movable contact and the connection conductor are brought into sliding contact, the Ag plating is worn out by the no-load opening and closing, and the copper base is exposed. This is because the Ag plating layer on both sides of the conductor is bitten.
In addition, the reason why the copper base is exposed when a large current is interrupted is that the two Ag plating layers are welded to each other. At this time, if the welded portion breaks during the sliding process, the portion becomes rough and the electrical contact is lost. As the temperature worsens, the heat generated by energization increases, and melting and welding become easier. Such a problem can be solved by applying a coating treatment made of a composite material in which carbon (C) particles are dispersed in a silver matrix to the sliding contact surface instead of the Ag plating. As is well known, carbon has excellent lubricity, but does not dissolve at all with silver. Therefore, the silver-carbon composite material can prevent squealing at the time of no-load opening and closing, and at the same time, hardly weld together even if it is melted by heat generation when a large current is applied. In any case, the sliding contact surface is kept smooth. It is possible to maintain stable current carrying capacity. In addition, when a large current such as a short-circuit current flows by connecting the movable contact and the connection conductor with a lead wire so as to form a parallel circuit with the sliding contact portion, the current is slid. By dividing the current into the contact portion and the lead wire, the thermal load on the sliding contact portion can be reduced, and the current capacity can be increased accordingly.

【Example】

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings showing the embodiment, the same reference numerals are given to portions substantially the same as those in the conventional example. First, FIG. 1 is a perspective view of a movable contact portion of a center pole according to a first embodiment of the present invention in principle. Movable contact
31 is formed by punching out a predetermined shape from a copper strip, and a movable contact 32 is brazed to the tip. The connection conductor 33 is formed integrally with the bimetal 9a, and is fastened to the case 1 by a screw (not shown) passing through the hole. In this case, the fixed conductor 9b (FIG. 16) for fixing the bimetal 9a is unnecessary. A pair of arms 33a opposed to each other are formed on the connection conductor 33 by bending, and the arms 33a elastically sandwich the end of the movable contact 31 and make sliding contact with the movable contact 31 that opens and closes. Although not shown, a common hole is formed in the movable contact 31 and the arm 33a, and the shaft 35 is inserted as shown. On the other hand, a concave portion 36a for receiving the movable contact 31 is formed in the holder 36 of the resin molded product.
Are fitted at both ends. Also, at that time, the arm
A compression spring 37 made of a coil spring is inserted into the shaft 35 on both sides of the arm 33a, and the movable contact 3
It is pressed against the side of 1. Reference numeral 38 denotes an integrally formed opening / closing shaft for connecting the holder 36 to holders on the left and right poles on both sides thereof (not shown). 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, the movable contact 31 opens and closes around the opening / closing shaft 38, and the left and right pole movable contacts similarly held by a holder (not shown) also open and close integrally. The overcurrent tripping device 9 of the conventional example of FIG. 16 and the embodiment of FIG. 1 is of a direct heating type in which a current flows through the bimetal 9a itself, but a current flows through the heater conductor to generate heat. There is an indirectly heated type that transfers heat to the combined bimetal. FIG. 2 shows a basic embodiment of a circuit breaker using such an overcurrent trip device, in which case a connecting conductor is used.
33 is formed integrally with the heater conductor 39. Other configurations are the same as those in the embodiment of FIG. 3 and 4 are longitudinal sectional views of the circuit breaker provided with the movable contact 31 and the connection conductor 33 shown in the embodiment of FIG. 1. FIG. 3 is a closed 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
The sliding contact between the side surface of the arm 31a and the inner wall surface of the arm 33a directly flows into the connection conductor 33, passes through the bimetal 9a, the flexible conductor 15, and the terminal 13
Leads to. Numeral 40 denotes a contact spring consisting of a compression spring inserted between the movable contact 31 and the case 1, and
Numeral 31 is urged toward the fixed contact 3 to give an appropriate contact pressure. Other configurations and operations are the same as those of the conventional example, and the description is omitted. Next, FIGS. 5 to 9 show a practical third embodiment of the present invention. Hereinafter, this will be described in detail. First, FIG. 5 shows a state in which a fixed contact and a connecting conductor which makes sliding contact with the fixed contact are combined. FIG. 5 (A) shows a state in which an upper plate of a mounting bracket 44 (described later) is partially removed. (B) is a side view in which a front side plate of the mounting bracket 44 is partially removed, and (C) is a rear view. In the figure, 41 is a movable contact stamped out of a copper strip in the illustrated shape, 42 is a movable contact brazed to the tip thereof, 43 is a connection conductor bent from a copper plate, and 44 is a thin steel plate having a large spring property. The mounting bracket 45 formed in a gate shape is a current limiting latch made of a steel plate constituting a current limiting mechanism. The connection conductor 43 is a screw passing through the hole 46 and is the case 1 of the circuit breaker.
A pair of opposing arms 43b is raised from a base 43a fastened to (FIG. 3), and the arm 43b is a movable contact.
The movable contact 41, which is bent into the shape shown in the drawing to a slightly smaller interval than the plate thickness of 41, is elastically sandwiched between the rear ends of the inserted movable contacts 41, and comes into sliding contact with the side surface thereof. . Also, as shown in FIG. 5 (A), the base 43a has a slit 43c extending from the left end to a position short of the hole 46 along the center line.
The arm 43b is easily elastically deformed in the lateral direction. A common through hole is formed in a sliding contact portion between the movable contact 41 and the arm 43b, and a shaft 47 is inserted through a slight gap. Then, a spring 49 made of a compression coil spring is inserted into the shaft 47 with a washer 48 on both sides of the arm 43b, and both ends of the shaft 47 are joined to the side plate of the mounting bracket 44 by caulking. As a result, the movable contact 41 is rotatable around the axis 47, and the arm 43b is pressed against the movable contact 41 by the spring 49 to apply an appropriate contact pressure. Here, FIG. 9 (A) is a side view of the connection conductor 43, and FIG. 9 (B) is a cross-sectional view along the line BB. As shown in FIG. 9, an annular convex portion 43c is formed inside the arm 43b so as to surround the through hole 50 through which the shaft 47 passes, and the movable contact 41 is formed at this portion.
It comes in contact with. This allows the movable contact 41
The contact range between the arm and the arm 43b is specified within the range of a small average radius, the braking torque to the movable contact 41 due to the frictional force can be suppressed to a small value, the contact pressure is improved, and even if the opening and closing movements are repeated, the contact surface becomes Constant and stable contact is maintained. Referring again to FIG. 5, the mounting bracket 44 has a shaft attached to its side plate.
The current limiting latch 45 is rotatably supported by another shaft 51 having both ends fixed similarly to 47. Current limiting latch 45 is shaft 51
Is a bifurcated hard member bent into a U-shape at the portion where it penetrates, and a normal surface 45a substantially perpendicular to the axis 47 on the side facing the axis 47 with the inflection point V in between, and a counterclockwise direction in FIG. And a current limiting surface 45b that is inclined. The current limiting latch 45 is provided with a current limiting pin 52 implanted on the normal surface 45a of the movable contact 41 so as to protrude left and right in a normal open / close state.
, And is pressed against the current limiting pin 52 by a pair of left and right current limiting springs 53 spanned between the upper end thereof and the upper part of the mounting bracket. On the other hand, the movable contact 41 is provided with a torque that rotates around the axis 47 in the counterclockwise direction in FIG. This torque is applied to the movable contact 42 when incorporated in the circuit breaker as described later.
Is generated toward the fixed contact 4. That is, 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 portion of the side plate of the mounting bracket 44 so as to project outward. The assembly of the illustrated movable contact 41 and the connection conductor 43 is fixed to the holder using the engagement pieces 44a and 44b. Next, the holder will be described. FIG. 6 is a plan view of the holder, and FIG. 7 is a cross-sectional view thereof along the line VII-VII. As shown in FIG. 6, holders 54 of respective poles made of a mold resin are connected to each other by an opening / closing shaft 55. 55a is an inter-phase barrier formed integrally with the opening / closing shaft 55. The holder 54 is rotatably supported by the connection shaft 55 being fitted into a bearing groove (not shown) formed in the phase gap wall 1a of the case 1 shown by a two-dot chain line. Notches 54a for connecting links of the opening and closing mechanism are formed on the left and right side surfaces of the holder 54 of the center pole. The assembly of FIG. 5 is mounted on the holder 54 as shown in FIG. That is, the holder 54 is formed with a concave portion 56 for inserting the above-mentioned assembly from the rear surface thereof, and a window 57 for opening the movable contact 41 so that the movable contact member 41 can be opened and closed. A fitting surface 56a is formed on the left and right walls of the concave portion 56 in accordance with the width of the mounting bracket 44, and a front edge 56b of the fitting surface 56a is formed in a contour of a front surface of the mounting bracket 44. Further, a step 56c is provided on the ceiling wall of the concave portion 56 corresponding to the engaging piece 44a, and further on the left and right walls along the lower portion of the fitting surface front edge 56b, a step corresponding to the engaging piece 44b. 56d is provided. On such a holder 54, the engaging pieces 44a and 4
When the assembly shown in FIG. 5 is pushed in while elastically deforming the inner side 4b, the mounting bracket 44 stops when the front surface of the mounting bracket 44 abuts the front edge 56b of the fitting surface of the left and right walls, and at the same time, the engagement pieces 44a and 44b
Is returned by the elastic force and engages with the steps 56c and 56d, respectively, and is fixed in the state shown in FIG. FIG. 8 is a perspective view showing the holder 54 to which the movable contact 41 is fixed as described above. Reference numeral 54b is a through hole into which a pin connecting the link of the opening / closing mechanism is inserted. FIG. 14 is a longitudinal sectional view of a center pole portion of the circuit breaker in which the holder 54 holding the assembly of FIG. 5 is incorporated, and the figure shows a closed state. The base 43a of the connection conductor 43 is bimetal 9
It is fastened to Case 1 together with a. In the illustrated state, the movable contact 41 is pressed by the fixed contact 3 to
Around the shaft 51 slightly counterclockwise around the shaft 51 against the current limiting spring 53 via the current limiting pin 52. I have. As a result, the movable contact 41 receives a rotational moment from the current-limiting spring 53 in the counterclockwise direction in the drawing to obtain a contact pressure between the contacts 4 and 42. The holder 54 and the movable contact 41 rotate about the axis A of the opening / closing shaft 55 in FIG. 7 during the opening / closing movement, or the axis B of the shaft 47 is moved away from the point A as shown in the figure. The shaft 47 pivots about point A by a radius r. Therefore, as shown in FIG. 9 (A), the through hole 50 through which the shaft 47 is inserted is formed as an elongated hole so as not to hinder its rotation. The reason that the point B of the axis supporting the movable contact 41 is shifted from the point A of the axis of the opening / closing shaft 55 is that the movable contact 41 is moved back and forth (horizontal direction in FIG. 14) with the rotation of the holder 54. Is moved slightly to slide between the contacts 4 and 42 to remove the oxide film on the contact surface. Next, the current limiting interruption by the action of the current limiting latch 45 is described. In FIG. 14, a fixed contact 3 has a movable contact 5
A conductor portion 3b located in parallel with the conductor of
, The directions of the currents flowing through the conductor portion 3b and the movable contact 31 are opposite to each other as shown by arrows. Therefore, the movable contact
31 is always receiving force in the direction of separation. 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, and pushes back the current limiting latch 45 against the force of the current limiting spring 53 to rotate around the shaft 47. To rotate clockwise. As a result, the current limiting pin 52 slides on the normal surface 45a of the current limiting latch 45, crosses the inflection point V, and rides on the current limiting surface 45b. When the current limiting pin 52 is in contact with the normal surface 45a, the angle between the normal surface 45a and the current limiting surface 45b in the current limiting latch 45 is limited by the current limiting latch 45 based on the spring force of the current limiting spring 53. pin
The force acting on 52 acts to rotate the movable contact 41 in the counterclockwise direction in the figure, and when the current limiting pin 52 moves to the current limiting surface 45b,
The force is set so as to act to rotate the movable contact 41 clockwise. Therefore, as described above, when the movable contact 41 is rotated more than a certain opening distance and exceeds the inflection point V, the movable contact 41 is rotated by the current limiting spring 53 in addition to the electromagnetic repulsion. In response to the opening, the opening and closing mechanism 16 is quickly opened prior to the opening. As a result, the arc voltage is rapidly increased, and so-called current limiting interruption is performed. FIG. 7 shows the result of such a current limiting cutoff. In FIG. 14, the reset of the current limiting latch 45 is performed in such a manner that the movable contact 41 is integrated with the cover 2 in the trip operation of the opening / closing mechanism 16 following the current limiting operation in accordance with a command of the overcurrent trip device 9 in FIG. This is performed by forcibly rotating the holder 54 in the clockwise direction in the figure while the holder 54 is in contact with the formed stopper 2a, and the current limiting pin 52 crosses the inflection point V in the reverse direction and engages with the normal surface 45a again. I do. FIG. 10 is an explanatory diagram for clarifying the force relationship at the time of the current limiting operation described above. FIG. 10 (A) shows a closed state of the circuit breaker, and FIG. 10 (B) shows a state immediately after the opening of the circuit breaker. Is shown.
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), the current-limiting spring
Due to the spring force P _{1 of} 53 and the distance L ₁ from the pin 52, a torque of P ₁ × L ₁ acts on the current limiting latch 45. This torque gives a force of P _{2 to} the current limiting pin 52 at a distance of L ₂ from the pin 51 on the substantially vertical normal surface 45a (P ₁ × L ₁ =
P ₂ × L _2), P ₂ × the force P ₂ from the limiting pin 52 by a distance L ₃ to the axis 47, in a counterclockwise direction with respect to the movable contact 41
Give the torque of the L _3. This torque causes the movable contact 42
A contact pressure between the contact and the fixed contact 4 occurs. On the other hand, in the state shown in FIG. 10B beyond the inflection point V, the torque acting on the current limiting latch based on the spring force P ₃ from the current limiting spring 53 causes the distance from the pin 51 on the current limiting surface 45b to be reduced. L force P ₄ occurs for limiting pin 52 at the point of _4. This force P
₄ the relationship between the tilt angle of Kiriryumen 45b, P ₄ × L ₅ to the movable contact 41 by a distance L ₅ to the shaft 47 through the top of FIG axis 47
The clockwise torque is applied to accelerate the separating operation. FIG. 11 shows a state in which the direction of the torque acting on the movable contact 41 reverses as soon as the current limiting pin 52 slides on the normal surface 45a and exceeds the inflection point V due to the electromagnetic repulsion, The + side of the torque indicates a counterclockwise direction, and the one side indicates a clockwise direction. By the way, when a large current flows and the electromagnetic repulsion exceeds the contact pressure, it is desired that the above-mentioned torque reversal occurs in as short a time as possible. To this end, an increase in the torque in the + direction while the current limiting pin 52 moves from the closed position to the inflection point V is suppressed, and the amount of engagement between the current limiting pin 52 and the current limiting latch 45 in FIG. it is necessary to reduce as much as possible L _6. In order to reduce the increase in the torque in the + direction, the angle difference between the normal surface 45a and the current limiting surface 45b may be reduced. However, the direction of the force P ₂ If the angle difference is small close to the shaft 47 side, the distance L ₃ is also made by the contact pressure is reduced smaller.
Further, when the engaging amount L ₆ is too small, the risk of limiting pin 52 exceeds the inflection point caused by contact bounce during circuit breaker closing. Therefore, in consideration of these tradeoffs, the angle and engaging amount L ₆ of the normal surface 45a appropriately determined. In the case of a circuit breaker configured to separate the movable contact from the fixed contact by electromagnetic repulsion, simply deforming the contact spring increases the reaction force of the contact spring with the separation of the movable contact. The movement of the movable contact is hindered. In contrast, the current limiting mechanism shown has a large current limiting effect, for example, AC46
It has been confirmed that when the current of 0 V and 42 kA is cut off, the peak value of the passing current decreases from about 33 kA to about 26 kA. Next, FIG. 12 (A) shows a main part of a movable contact 41 and a connection conductor 43 which make sliding contact, and FIG. 12 (B) is an enlarged view of the B part. As shown, the current flows through several contact points P in the contact area. This current gathers toward the contact point P as indicated by an arrow i in FIG. 12 (B) and spreads at the same time as passing through the contact point P. Therefore, the direction of the current is reversed before and after the contact point P, and Electromagnetic repulsion acts between the contact 41 and the arm 43b of the connection conductor 43. Assuming that the passing current at one contact point P is I _K (kA), the magnitude F ₁ of the electromagnetic repulsive force is F ₁ = Σ51 _j ² × 10 ^-2 (kg), where n is the number of contact points P. j = 1 to n). The electromagnetic repulsive force F ₁ increases at an increasing rate as the current passing through the circuit breaker increases, and thus increases as the current passing through each contact point P increases. As a result, the force of the spring 49 is reduced, the number of the contact points P is reduced, and the passing current at the remaining contact points P becomes excessive, and there is a possibility that arcing or welding occurs at that portion. For this reason, when the movable contact 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 to increase the limit value, a problem arises that the frictional force is increased this time and the constant opening / closing speed of the movable contact 41 is reduced. As a means for solving this problem, as shown in FIG. 5 (C) and FIG. 9 (B), the distance between the arm 43b and the movable contact 41 near the contact portion of the arm 43b is greater than that of the contact portion. Also, a portion 58 with a narrow interval is provided. In the following,
This will be described with reference to FIG. Now, assuming that the length of the arm 43b in the portion 58 is l, the interval between the arms 43b is S, and the current shunted to each arm 43b is I [kA],
Current I from flowing through the arm 43b in the same direction, the following electromagnetic attracting force F ₂ generated in the inter-arm 43b. F ₂ = 2.04 kl / S · I ² (k: constant) Therefore, if the interval S is determined so that the electromagnetic attraction force F ₂ is larger than the electromagnetic repulsion force F ₁ , the force of the spring 49 is increased. The applicable short-circuit current rating can be improved without performing. In FIG. 17 the electromagnetic repulsive force F ₁ and the electromagnetic attractive force F ₂ indicates the state of performing change with short-circuit current passing through the circuit breaker. The contact force in the figure is a force obtained by the elasticity of the spring 49 and the connection conductor 43. Further, as shown in FIG. 9 (B), the annular convex portion 43c provided at the contact portion of the arm 43b is provided outside the arm 43b with the movable contactor 41.
It acts to reduce the electromagnetic repulsive force F ₁ to the size of the interval of the current flowing in opposite directions before and after the distance therebetween, the contact between the. Further, by applying a coating treatment with a composite material of silver (Ag) and carbon (C) to at least one of the sliding contact surfaces of the movable contact and the connection conductor, the circuit breaker can be repeatedly opened and closed with no load or interrupted by a large current. To prevent the contact surface from sticking and welding
The current-carrying performance can be greatly improved. Thus, test results will be described below for an embodiment in which the above-mentioned coating treatment is applied to the movable contact 41 and the connection conductor 43 having the structure shown in FIG. First, each of the movable contact 41 and the connection conductor 43 is made of Ag-6.
% C (vol%) was electroplated to a thickness of 7 μm.
At this time, the C particles dispersed in Ag used were flaky particles having a major axis of 0.5 to 2 μm and a minor axis of 0.2 to 0.5 μm (Experimental Example 1). Similarly, each of the movable contact 41 and the connection conductor 43 has an Ag-
A 3% C (vol%) coating was electroplated to a thickness of 7 μm. At this time, the C particles dispersed in Ag have a major axis of 0.8 to 5 μm.
m, and a piece having a minor axis of 0.3 to 1 μm was used (Experimental Example 2). Further, as a comparative example, a similar movable contact and a connection conductor coated with 7 μm of Ag plating were prepared. Table 1 shows the results obtained by incorporating these movable contacts and connection conductors into a circuit breaker, and performing a no-load switching test and a large current cutoff test. According to this, it can be understood that the copper base material is less likely to be exposed in the case where the Ag-C composite material is plated than in the case of the normal plating. Although two examples are shown in the above experimental examples, the effect of the present invention depends on the nature of C, so that the C% and the size of C grains are not limited to these. In addition, the ease of biting and melting of the sliding contact portion is also affected by the width and surface pressure of the contact portion, and thus the C% and the size of the C grains are determined collectively. However, C has conductivity but the electrical resistance is Ag
Of several hundred to several thousand times. Therefore, C%
Large C that penetrates the plating thickness
The use of particles is not preferable because it increases the heat generated in the sliding contact portion and increases the terminal temperature 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 method of forming the film is not limited to electroplating. Since the presence of C in the sliding contact surface contributes to the prevention of fraying or welding, it is effective to form an Ag-C coating only on one of the movable contact and the connection conductor. In that case, it is desirable that the other component is plated with Ag, but since C has an antioxidant effect, some current-carrying characteristics can be obtained even with copper. Note that the coating need not be applied to the entire surface of the conductor, and may be formed only on the sliding contact surface. Further, the fine hard particles as third particles Ag-C, for example _{SiC, WC, ZrB, Al 2} O 3, ZrO 2, CrO 3, TiO 2, R
₂ O ₃ , ThO ₂ , Y ₂ O ₃ , MoO ₃ , W ₂ C, TiC, B ₄ C, CrB ₂
By dispersing such particles, increase the hardness of the entire coating,
A long-life contact portion that is less likely to be worn can be configured. Finally, FIG. 15 shows a fourth embodiment of the present invention in which a movable contact and a connecting conductor which slides on the movable contact are further connected by a lead wire. FIG. 15 (A) shows a movable contact portion. (B) is a side view thereof, and (C) is a rear view thereof. In the figure, reference numeral 59 denotes a flexible lead wire having substantially the same resistance as the sliding contact portion between the movable contact 41 and the connection conductor 43, one end of which is the lower surface of the rear end of the movable contact 41. The other end is connected to the upper surface of the base 43a of the connection conductor 43 by brazing, respectively, and the lead wire 59 forms a parallel circuit for the sliding contact portion. As a result, the current flowing between the movable contact 41 and the connection conductor 43 is almost divided into the sliding contact portion and the lead wire 59, and the thermal contact of the sliding contact portion when a large current such as a short-circuit current flows. The load is reduced by half, and the limit current value of the entire circuit breaker can be increased accordingly.

【The invention's effect】

ADVANTAGE OF THE INVENTION According to this invention, a movable contactor and a connection conductor can be electrically connected, without using a flexible conductor, and it is possible to form a small circuit breaker with excellent reliability and high breaking performance. Becomes Further, at this time, by applying a coating treatment made of a composite material of silver and carbon to the sliding contact surface of the movable contact or the connection conductor, it is possible to maintain a good energized state for a long period of time. Further, if necessary, a part of the current of the sliding contact portion is diverted to the lead wire,
It is possible to increase the current capacity.

[Brief description of the drawings]

FIG. 1 is a perspective view of a movable contact portion of a first embodiment of the present invention, FIG. 2 is a perspective view of a movable contact portion of a second embodiment of the present invention, and FIG. FIG. 4 is a longitudinal sectional view of a circuit breaker having a movable contact portion in a closed state of a central pole portion, FIG. 4 is a longitudinal sectional view of the circuit breaker in an open state, and FIG. 5 (A) is a third embodiment of the present invention. FIG. 5 (B) is a side view, FIG. 5 (C) is a rear view, and FIG.
5 is a plan view of a holder for holding the movable contact portion of FIG. 5, FIG. 7 is a sectional view taken along the line VII-VII of FIG. 6, and FIG. 8 is a movable view of FIG. 9 (A) is an enlarged side view of the connection conductor in FIG. 5, FIG. 9 (B) is a cross-sectional view along the line BB, FIG. 10 ( FIG. 10A illustrates a force relationship between the current limiting latch and the current limiting pin in a closed state, FIG. 10B illustrates a force relationship immediately after opening, and FIG. FIG. 12 (A) is a diagram showing the relationship between the torque acting on the movable contact and the opening distance of the movable contact based on FIG. 12 (A). FIG. 5 (C) is a rear view, FIG. 12 (B) is an enlarged view of the portion B, and FIG. 13 is a diagram showing the relationship between the magnetic repulsive force and magnetic attractive force and the short-circuit current at the contact portion in FIG. Show line FIG. 14 is a longitudinal sectional view showing a closed state of a center pole portion of the circuit breaker having the movable contact portion shown in FIG. 5, and FIG. 15 (A) is a movable contact according to a fourth embodiment of the present invention. 15 (B) is a side view thereof, FIG. 15 (C) is a rear view thereof, FIG. 16 is a longitudinal sectional view showing a closed state of a center pole portion of a conventional circuit breaker, FIG. The figure is a longitudinal sectional view of the same open state. 1 ... case, 16 ... opening / closing mechanism, 31 ... movable contact, 33
… Connection conductor, 33a… Arm, 35… Spring, 36… Holder, 37… Open / close axis, 41… Movable contact, 43… Connection conductor, 43a… Arm, 44… Mounting bracket, 44a, 44b …… engaging piece,
49: spring, 54: holder, 55: open / close shaft, 56: recess, 56c, 56d: step, 59: lead wire.

──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 2-31215 (32) Priority date Hei 2 (1990) February 9 (33) Priority claim country Japan (JP) (72) Inventor Tatsunori Takahashi 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. Person Takeyuki Kandatsu 1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. References JP-A-63-174238 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01H 71/08 H01H 73/02 H01H 73/20

Claims (5)

(57) [Claims] A movable contact is held by an insulator holder rotatably supported by a case via an opening / closing shaft, and the movable contact is driven by an opening / closing mechanism and is moved together with the holder by the opening / closing shaft. In a circuit breaker that opens and closes around, the movable contact and the connection conductor fixed to the case are electrically connected by sliding contact, and the connection end of the connection conductor with the movable contact is A pair of opposing arms are formed to elastically sandwich the movable contact, and a shaft is inserted through a contact portion between the arm and the movable contact, so that the movable contact can be turned on the arm. A circuit breaker, which is connected and has a compression coil spring inserted at both ends of the shaft to press the arm against a side surface of the movable contact. 2. The circuit breaker according to claim 1, wherein a portion of the arm of the connection conductor near the contact portion of the arm with the movable contact is provided at a portion where the facing distance is smaller than the contact portion. vessel. 3. The circuit breaker according to claim 1, wherein the movable contact is mounted on a mounting member made of a thin plate formed by cutting and bending an engaging piece, and this mounting metal corresponds to the engaging piece. A circuit breaker, wherein the movable contact is held by the holder by press-fitting into a holder having a recess having an engagement step. 4. The circuit breaker according to claim 1, wherein at least one of the sliding contact surfaces of the movable contact and the connection conductor is formed of a composite material of silver and carbon. A circuit breaker characterized by having been subjected to. 5. The circuit breaker according to claim 1, wherein the movable contact and the connection conductor are formed in a parallel circuit with respect to a sliding contact portion therebetween. A circuit breaker characterized by being connected by a flexible lead wire.