JP2015046310A - Circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit breaker which allows stable overload interruption when it is brought into electric conduction.SOLUTION: A circuit breaker comprises: a housing 1; a load-side conductive part 11 fixed to the housing 1; a fixed-side conductive part 14 fixed to the bottom face of the housing 1; a bendable magnetostrictive bimetal 8 whose one end is bonded to the fixed-side conductive part 14; a coil 9 whose one end is electrically connected to the magnetostrictive bimetal 8 while being wound around the outer periphery of the magnetostrictive bimetal 8, and whose other end is electrically connected to the load-side conductive part 11; and an opening/closing mechanism 15 which opens and closes between a movable contact 3 and a fixed contact 2. If an overload current flows into the coil 9 so that a magnetic field is generated in the coil 9, the magnetostrictive bimetal 8 is bent in the direction of the opening/closing mechanism 15 so as to be brought into contact with the opening/closing mechanism 15. Consequently, the opening/closing mechanism 15 releases the contact between the movable contact 3 and the fixed contact 2.

Description

  The present invention relates to a circuit breaker that opens and closes contacts when an overload current exceeding the rated current of the circuit flows, and interrupts the circuit.

  In the conventional circuit breaker, the circuit is interrupted when an overload current exceeding the rated current flows by using a bimetal that bends according to the current value. In such a circuit breaker, when an overload current flows, the bimetal is bent and contacts the trip lever, and the switching mechanism is operated to open and close the contacts.

  For example, Patent Documents 1 and 3 describe a circuit breaker that breaks a circuit by operating an opening / closing mechanism using a bimetal that is curved as the temperature rises.

  Further, for example, Patent Document 2 describes a bimetal that is bent by the generation of a magnetic field.

Japanese Patent No. 2934893 (paragraphs [0001] to [0011], FIG. 1, FIG. 3, FIG. 9) Japanese Examined Patent Publication No. 7-122116 (paragraphs [0031] to [0046]) Japanese Patent No. 3518101 (paragraphs [0001] to [0009])

  In such a circuit breaker, the contact area between the contacts varies due to the switching operation, and the switching resistance in the circuit and the contact resistance of the contacts change. In addition, the connection state between the circuit breaker and an external circuit such as an electric wire changes each time it is connected. As a result of the contact resistance changing due to these factors, when the bimetal generates heat due to the current, the resistance value changes each time the current is applied even if the current is the same. Then, the amount of heat generated by the bimetal and the circuit changes, and the amount of bending of the bimetal varies. As a result, there is a problem that even if the load is an overload current, the switching mechanism does not operate and does not shut off, or conversely, the circuit is shut down even if the overload current is not reached, and the amount of bending becomes unstable. Further, when it is necessary to energize again after the circuit is cut off, there is a problem that the bent bimetal must be cooled until it returns to a position where it can be energized again to a position where the circuit is cut off due to heat generation of the circuit.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a circuit breaker that performs a stable overload breaking operation when energized.

  The circuit breaker according to the present invention can be bent by joining a housing, a load-side conductive portion fixed to the housing, a fixed-side conductive portion fixed to the bottom surface in the housing, and one end of the fixed-side conductive portion. A magnetostrictive bimetal, a coil that is electrically connected to the magnetostrictive bimetal at one end and wound around the outer periphery of the magnetostrictive bimetal and the other end is electrically connected to the load-side conductive portion, and a movable contact and a fixed contact are opened and closed. When an overload current flows through the coil and a magnetic field is generated in the coil, the magnetostrictive bimetal curves in the direction of the switching mechanism and contacts the switching mechanism, and the switching mechanism is released from the contact between the movable contact and the fixed contact. It is characterized by making it.

  The circuit breaker of the present invention generates a magnetic field when energized by a coil arranged around the magnetostrictive bimetal, and the magnetostrictive bimetal is bent and the switching mechanism is operated by overload energization to shut off the circuit. The load can be cut off.

1 is a front view showing a circuit breaker according to Embodiment 1. FIG. It is a front view which shows the magnetostriction bimetal periphery of the circuit breaker by Embodiment 1. It is a front view which shows the magnetostriction bimetal periphery of the circuit breaker by Embodiment 1. FIG. 3 is a front view illustrating a current flow around the magnetostrictive bimetal of the circuit breaker according to the first embodiment. It is a figure which shows the relationship between the number of coil turns in the structural example of the circuit breaker by Embodiment 1, and a magnetic field. It is a front view which shows the magnetostriction bimetal periphery of the circuit breaker by Embodiment 3. It is a figure which shows the relationship between the coil turns in the structural example of the circuit breaker by Embodiment 4, and a magnetic field. It is a front view which shows the magnetostriction bimetal periphery of the circuit breaker by Embodiment 5. It is a front view which shows the magnetostriction bimetal periphery of the circuit breaker by Embodiment 6.

Embodiment 1 FIG.
FIG. 1 is a front view showing a circuit breaker according to Embodiment 1 of the present invention. An opening / closing mechanism 15 having a mechanism portion 4, a load-side conductive portion 11, a fixed-side conductive portion 14, a magnetostrictive bimetal 8, and a fixed contact 2 are provided inside the circuit breaker casing 1. .

  The opening / closing mechanism 15 includes a trip lever 6 installed at a position where it can come into contact with the magnetostrictive bimetal 8, a latch 7 that can come into contact with the trip lever 6, and a mechanism portion 4 that can rotate. The opening / closing mechanism 15 has a movable contact 3 provided on the housing 1, and the movable contact 3 can contact the fixed contact 2.

  The magnetostrictive bimetal 8 is erected in the longitudinal direction and is fixed to the fixed-side conductive portion 14. The magnetostrictive bimetal 8 is formed by bonding alloys having different magnetostrictive characteristics. The coil 9 is disposed so as to wind around the magnetostrictive bimetal 8. In addition, the coil 9 is fixed to the load side conductive portion 11 by welding or caulking on the tip side of the magnetostrictive bimetal 8. Further, the coil 9 is connected and fixed to the fixed-side conductive portion 14 by welding or caulking on the base side of the magnetostrictive bimetal 8.

  The movable contact 3 is connected to the coil 9 through a conducting portion. The load-side conductive portion 11 is connected to an external load such as a motor with an electric wire or the like. The stationary-side conductive portion 14 is fixed to the housing 1 with screws or caulking. The fixed-side conductive portion 14 is electrically connected to the power-source-side conductive portion 12 via the fixed contact 2 to form a current circuit. The fixed contact 2 is fixed to the power supply side conductive portion 12 and is connected to an external circuit by an electric wire or the like.

  Subsequently, the operation of the circuit breaker will be described. When an overload current flows and a magnetic field is generated in the coil 9 by energization and the magnetostrictive bimetal 8 is bent, the magnetostrictive bimetal 8 comes into contact with the trip lever 6. The trip lever 6 removes the latch 7 and rotates the mechanism unit 4 clockwise. When the mechanism unit 4 operates, the movable contact 3 is released from contact with the fixed contact 2 and the circuit is interrupted.

  FIG. 2 is a front view showing the periphery of the magnetostrictive bimetal 8 according to Embodiment 1 of the present invention. Since the coil 9 is wound with the magnetostrictive bimetal 8, a magnetic field is generated in the longitudinal direction of the magnetostrictive bimetal 8 by energization. When the magnetostrictive bimetal 8 is not energized, it is not curved as shown in FIG. 2, and this state is set as the initial position.

  FIG. 3 is a front view showing the operation around the magnetostrictive bimetal 8 in the first embodiment. When the magnetostrictive bimetal 8 is energized, the magnetostrictive bimetal 8 is curved because an alloy having different magnetostrictive characteristics is bonded to the magnetic field generated in the longitudinal direction of the magnetostrictive bimetal 8. As a configuration of the magnetostrictive bimetal 8, for example, a Co—Mn—Fe—Tb alloy is used as a positive magnetostrictive alloy and a Sm—Dy—Fe—Co alloy is used as a negative magnetostrictive alloy. is there.

  FIG. 4 is a front view showing a current flow around the magnetostrictive bimetal 8 in the first embodiment. The actual current flow is alternating current. As shown in FIG. 4, the current flows from the fixed-side conductive portion 14 to the connection portion of the coil 9, flows through the coil 9, and then flows to the load-side fixed portion 11.

  According to such a configuration, when an overload current is passed and the circuit is interrupted, the contact area between the movable contact 3 and the fixed contact 2 changes due to opening and closing, and the resistance value changes. Further, the resistance value varies depending on the contact resistance of the connection between the load side conductive portion 11 or the power source side conductive portion 12 and the external circuit. The magnetostrictive bimetal 8 is bent by a magnetic field generated in the longitudinal direction of the magnetostrictive bimetal 8 when energized.

  Therefore, the circuit breaker according to the first embodiment can reduce the influence of the change in contact resistance compared to the circuit breaker that uses a thermal bimetal that changes and curves when heat is applied. Can be cut off.

The configuration of the magnetostrictive bimetal 8 will be described using examples of magnetostrictive characteristics and dimensional values. There is a configuration in which a Co—Mn—Fe—Tb alloy is a positive magnetostrictive alloy and a Sm—Dy—Fe—Co alloy is a negative magnetostrictive alloy and the two are joined. In this configuration, the magnetostrictive bimetal 8 has a length of 30 mm, a thickness of 1.5 mm, and a width of 3 mm, and an applied magnetic field of H = 100 (Oe) (≈8 × 10 ³ (A / m)). The amount of bending is 3 mm.

The configuration of the circuit breaker using the magnetostrictive bimetal 8 in this configuration is shown below. When a circuit breaker with a rated current of 100 A is overloaded by 125%, if the magnetostrictive bimetal 8 is bent 3 mm and the mechanism unit 4 is operated, an applied magnetic field of 100 (Oe) ≈8 × 10 ³ (A / m) Is required. The number of turns of the coil 9 necessary for generating this applied magnetic field is expressed by the following formula 1.

  H: Magnetic field, n: Number of turns, I: Current, L: Coil length, r: Coil inner diameter

FIG. 5 is a diagram illustrating a relationship between the number of coil turns and a magnetic field in the configuration example of the circuit breaker according to the first embodiment. I = 125 (A), L = 0.03 (m), and r = 0.005 (m). In this configuration, the number of turns necessary for generating a magnetic field of H = 8 × 10 ³ (A / m) is n = 130 (turns), and when a 0.1 mm winding is used, the winding width is 13 mm. Therefore, the coil 9 is wound around the magnetostrictive bimetal 8 having a length of 30 mm so that the windings of the coil 9 do not contact each other. Also, E = 2.5 × 10 ³ (kgf / m ² ), D = 3 (mm), w = 3 (mm), t = 1.5 (mm), l = 30 (mm) P = 7.0 (kgf), and the mechanism unit 4 is designed to perform a cutoff operation with this output. The output of the magnetostrictive bimetal 8 in this configuration is expressed by the following formula 2.

  P: output, E: elastic modulus, D: displacement, w: width, t: thickness, l: length

  With this configuration, when the circuit breaker of the first embodiment trips, no current flows through the coil 9, so that the magnetic field generated by energization when the circuit is interrupted decreases. Accordingly, the magnetostrictive bimetal 8 returns from the curved state as shown in FIG. 3 to the initial position shown in FIG. The thermal circuit breaker needs to be cooled in order to return the bent bimetal to the original state due to the heat generated during energization. On the other hand, in the magnetostrictive circuit breaker according to the first embodiment, since the bending of the magnetostrictive bimetal 8 is caused by a magnetic field, cooling is unnecessary. I can do it.

Embodiment 2. FIG.
In addition to the configuration of the first embodiment, the circuit breaker of the second embodiment insulates the magnetostrictive bimetal 8 and the coil 9 with an insulating cover 10. An example of the insulating cover 10 is a resin film having electrical insulation (for example, polytetrafluoroethylene).

  According to this configuration, the magnetostrictive bimetal 8 and the coil 9 are insulated from each other, thereby preventing a short circuit at the winding portion between the coil 9 and the magnetostrictive bimetal 8. That is, it is possible to prevent the problem that the required magnetostriction characteristic cannot be obtained because the magnetic field is not sufficiently generated in the winding portion. In addition, it is possible to suppress the occurrence of problems such as the disturbance of the generated magnetic field due to the increased variation in the current value flowing through the coil 9 and the occurrence of variations in the bending amount of the magnetostrictive bimetal 8 due to the disturbance of the generated magnetic field.

Embodiment 3 FIG.
FIG. 6 is a front view showing the periphery of the magnetostrictive bimetal 8 of the circuit breaker according to the third embodiment. In the circuit breaker of the third embodiment, in addition to the configuration of the first embodiment, a magnetic shield 13 is attached around the coil 9 as shown in FIG. As an example of the magnetic shield 13, there is a configuration in which the outside of the coil 9 is covered with an insulating cover 10 and the magnetic shield 13 is wound from above. The material used for the magnetic shield 13 is a metal mesh made of a magnetic material having a high magnetic permeability such as an Fe—Ni alloy, metal ink, or plating.

  According to this configuration, the magnetic shield 13 restricts the electromagnetic field around the coil 9 from affecting the inside of the magnetic shield 13. As a result, since the magnetic field other than the magnetic field generated by the coil 9 is restricted from affecting the magnetostrictive bimetal 8, the circuit breaker of the third embodiment is more stable than the circuit breaker of the first embodiment. It becomes possible to do.

Embodiment 4 FIG.
FIG. 7 is a diagram showing the relationship between the number of coil turns and the magnetic field in the specific configuration of the circuit breaker according to the fourth embodiment. The circuit breaker of the fourth embodiment uses a magnetostrictive bimetal 8 having characteristics different from those of the magnetostrictive bimetal 8 of the overload cutoff operation described in the first embodiment. When a short-circuit current of about 1000 to 2000% of the rated value is applied, the magnetostrictive bimetal 8 can be used for the instantaneous interruption operation by installing the magnetostrictive bimetal 8 that instantaneously cuts off. For example, as a configuration of the magnetostrictive bimetal 8, a Co—Mn—Fe—Tb alloy is used as an alloy having a positive magnetostriction characteristic, and an Sm—Dy—Fe—Co alloy is used as an alloy having a negative magnetostriction characteristic, and the two are joined. .

The operating current during instantaneous operation is 1300%, and I = 1300 (A), L = 0.03 (m), and r = 0.005 (m). According to this configuration, when the magnetostrictive bimetal 8 having the same dimensions and characteristics as in the first embodiment is used, the number of turns necessary for generating a magnetic field of H = 8 × 10 ³ (A / m) is n = 13 (times). When a 0.1 mm winding is used, the winding width is 1.3 mm.

  The circuit breaker according to the fourth embodiment can be adapted to the instantaneous breaking operation by using the magnetostrictive bimetal 8 having magnetostriction characteristics different from those of the first embodiment.

Embodiment 5 FIG.
FIG. 8 is a front view showing the periphery of the magnetostrictive bimetal 8 of the circuit breaker according to the fifth embodiment. In addition to the configuration of the circuit breaker according to the first embodiment, the circuit breaker according to the fifth embodiment changes the number of turns of the coil 9 between the tip side and the root side of the magnetostrictive bimetal 8, thereby changing the characteristics of the magnetostrictive bimetal 9. Change.

  For example, in the configuration shown in FIG. 8, as in the coil 9, the number of turns of the coil 9 is increased on the base side of the magnetostrictive bimetal 8, and the number of turns of the coil 9 is decreased near the tip side of the magnetostrictive bimetal 8. In this configuration, when a current is applied to the magnetostrictive bimetal 8, the number of turns is large on the base side of the magnetostrictive bimetal 8, so that the magnetic field is large, and the magnetostrictive bimetal 9 is greatly curved accordingly. However, since the number of turns of the coil 9 is small at the front end side of the magnetostrictive bimetal 8, the generated magnetic field is also small, and the magnetostrictive bimetal is bent slightly.

  The circuit breaker according to the fifth embodiment is curved by changing the number of turns of the coil 9 even when the material and configuration of the magnetostrictive bimetal 8 and the coil 9 are the same when changing the required operating characteristics depending on the rating and the like. It is possible to adjust the amount and operating time.

  Similarly, for example, the number of turns of the coil 9 may be reduced on the base side of the magnetostrictive bimetal 8 and the number of turns may be increased on the tip side of the magnetostrictive bimetal 8. With this configuration, the amount of bending at the tip side of the magnetostrictive bimetal 8 can be made larger than that at the base side, and the amount of bending, operating time, etc. can be adjusted for the same magnetostrictive bimetal 8.

Embodiment 6 FIG.
FIG. 9 is a front view showing the periphery of the magnetostrictive bimetal 8 of the circuit breaker according to the sixth embodiment. In the first embodiment, the load side conductive portion 11 is connected to the coil 9 on the tip side of the magnetostrictive bimetal 8. On the other hand, in the circuit breaker according to the sixth embodiment, the connection portion between the coil 9 and the load side conductive portion 11 is installed near the base side of the magnetostrictive bimetal 8 as shown in FIG. The front end side of the magnetostrictive bimetal 8 and the coil 9 are directly energized, and the magnetostrictive bimetal 8 is connected in series with the coil 9 on the front end side of the magnetostrictive bimetal 8.

  When the magnetostrictive bimetal 8 having this configuration is bent by the coil 9 connected at the tip side of the magnetostrictive bimetal 8, the stress generated between the coil 9 and the load side conductive portion 11 is reduced, and an appropriate curve is obtained. It is done. In addition, the coil 9 connected on the distal end side of the magnetostrictive bimetal 8 can reduce the variation in stress compared to a configuration in which the coil 9 is not used, and a more stable interruption operation is possible.

Embodiment 7 FIG.
In the circuit breaker according to the seventh embodiment, the magnetostrictive bimetal 8 is used for operation as a thermodynamic bimetal that is bent by heat generation. Since the magnetostrictive bimetal 8 has a structure in which a plurality of alloys are bonded together, the magnetostrictive bimetal 8 can be bent due to a difference in coefficient of thermal expansion. As a configuration of the magnetostrictive bimetal 8, for example, a Co—Mn—Fe—Tb alloy is used as a positive magnetostrictive alloy and a Sm—Dy—Fe—Co alloy is used as a negative magnetostrictive alloy. There is.

  With this configuration, the coil 9 is energized when energized, and the magnetostrictive bimetal 8 is bent by the heat generation of the magnetostrictive bimetal 8 or the coil 9, so that the magnetostrictive bimetal 8 is bent by heat in addition to the generation of the magnetic field. Therefore, the circuit breaker according to the seventh embodiment can bend the magnetostrictive bimetal 8 more greatly when energized than the circuit breaker according to the first embodiment.

DESCRIPTION OF SYMBOLS 1 Case 2 Fixed contact 3 Movable contact 4 Mechanism part 5 Handle 6 Trip lever 7 Latch 8 Magnetostrictive bimetal 9 Coil 10 Insulation cover 11 Load side conductive part 12 Power supply side conductive part 13 Magnetic shield 14 Fixed side conductive part 15 Opening and closing mechanism

Claims (8)

A housing,
A load-side conductive portion fixed to the housing;
A fixed-side conductive portion fixed to the bottom surface in the housing;
One end of the magnetostrictive bimetal which is bonded to the fixed conductive portion and can be bent,
A coil having one end electrically connected to the magnetostrictive bimetal and wound around an outer periphery of the magnetostrictive bimetal and the other end electrically connected to the load-side conductive portion;
An open / close mechanism that opens and closes between the movable contact and the fixed contact;
When an overload current flows through the coil and a magnetic field is generated in the coil, the magnetostrictive bimetal is bent in the direction of the opening / closing mechanism and comes into contact with the opening / closing mechanism, and the opening / closing mechanism is brought into contact with the movable contact and the fixed contact. Circuit breaker characterized by being opened. The circuit breaker according to claim 1, wherein an insulating cover is provided between the magnetostrictive bimetal and the coil. The circuit breaker according to claim 1, wherein the magnetostrictive bimetal is surrounded by a magnetic shield. The circuit breaker according to claim 1, wherein the magnetostrictive bimetal has a magnetostrictive characteristic that interrupts when a short-circuit current is applied. 2. The circuit breaker according to claim 1, wherein the number of turns per unit length of the coil wound around the magnetostrictive bimetal is large on the tip side and small on the root side. 2. The circuit breaker according to claim 1, wherein the number of turns per unit length of the coil wound around the magnetostrictive bimetal is small on the tip side and large on the root side. 2. The circuit breaker according to claim 1, wherein the load-side conductive portion is connected on the base side of the magnetostrictive bimetal and directly supplies electricity to the magnetostrictive bimetal. The circuit breaker according to any one of claims 1 to 7, wherein the magnetostrictive bimetal is a heat-responsive type.

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