breaker

Abstract

To form an elastic arm plate and a terminal plate from different metal plates and connect the plates by arc welding, and nonetheless to stabilize a contact state between the plates.SOLUTION: A breaker comprises: a stationary contact metal plate 4 including a stationary contact 5; an elastic arm plate 6 including a movable contact 7 at a position opposed to the stationary contact 5; a terminal plate 3 configured by being connected to the elastic arm plate 6; a sheath case 1 configured by fixing the terminal plate 3 and the stationary contact metal plate 4; and a bimetal 8 which is incorporated in the sheath case 1 and performs switching to an OFF state by pressurizing the elastic arm plate 6 thereby separating the movable contact 7 from the stationary contact 5. The elastic arm plate 6 has elasticity that enables movable contact 7 to be pressurized to the stationary contact 5 and enables an ON state to be held by its own elasticity in a non-pressurized state of the bimetal 8. The elastic arm plate 6 and the terminal plate 3 are laminated and connected via a welded portion 30 to which a laminated portion 40 is laser-welded. The welded portion 30 includes a linearly extending weld line 31 or any one of or both a plurality of weld spots 32.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a breaker that detects temperature with a bimetal, and the bimetal elastically deforms an elastic arm plate to separate a movable contact from a fixed contact to switch to an off state.

Background Art

[0002] Devices such as battery packs and motors can improve safety by interrupting current when the temperature becomes abnormally high. To achieve this, a small micro breaker that switches the contact to off when the set temperature is reached is used. For example, a battery pack incorporating a lithium-ion battery has its temperature increase when charged and discharged under abnormal usage conditions. Therefore, a small breaker is built into the protection circuit to interrupt the current at abnormally high temperatures to ensure safety. Also, motors and the like may have an abnormally high temperature in an overloaded state or when an abnormal current flows. In this state, the breaker interrupts the current to protect the motor.

[0003] As a micro breaker used for such applications, a breaker that detects a temperature rise with a bimetal and separates a movable contact from a fixed contact to switch to an off state has been developed. (See Patent Document 1)

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The circuit breaker described in Patent Document 1 switches the movable contact to the off state by reversing a bimetallic strip. In this circuit breaker, when the temperature rises above the set temperature, the bimetallic strip reverses, and the reversing bimetallic strip deforms so as to push up the elastic arm plate that fixes the movable contact at its tip, separating the movable contact from the fixed contact and turning it off, thus interrupting the current. When the temperature drops and the bimetallic strip returns to its original shape, the elasticity of the elastic arm plate causes the movable contact to come into contact with the fixed contact, returning it to the on state. When the elastic arm plate is not being pushed up by the bimetallic strip, that is, when the bimetallic strip is not reversing due to temperature, it elastically presses the movable contact against the fixed contact. In this state, the movable contact is kept in the on state by the elasticity of the elastic arm plate and in contact with the fixed contact.

[0006] The circuit breaker described in Patent Document 1 has an elastic arm plate built into an outer casing, which is connected to a terminal plate inside the outer casing, and the terminal plate is brought out to the outside of the outer casing to serve as a connection terminal. While this structure allows the use of metal plates of optimal material and thickness for the elastic arm plate and terminal plate, the elastic arm plate and terminal plate are connected by spot welding, such as laser welding. This makes it difficult for the elastic arm plate to stably press the movable contact against the fixed contact over a long period of time, resulting in the disadvantage of unstable contact conditions. Unstable contact conditions increase the contact resistance. Circuit breakers with increased contact resistance experience greater power loss in the ON state, and also generate more Joule heat due to the contact resistance. The temperature rise due to Joule heat can cause the bimetal to invert, so in environments where the ambient temperature is lower than the set temperature, the bimetal may invert due to its own heat generation and switch to the OFF state.

[0007] This invention was developed with the aim of solving the shortcomings of conventional circuit breakers. An important objective of this invention is to provide a circuit breaker that can stabilize the contact state of the contacts while connecting the elastic arm plate and the terminal plate by laser welding them as separate metal plates. [Means for solving the problem]

[0008] A circuit breaker according to one aspect of the present invention comprises a fixed contact metal plate having a fixed contact, an elastic arm plate having a movable contact at its tip located opposite the fixed contact, a terminal plate connected to the elastic arm plate, an outer casing fixing the terminal plate and the fixed contact metal plate, and a bimetal built into the outer casing that presses the elastic arm plate to separate the movable contact from the fixed contact and switch it to the off state. In the non-pressing state of the bimetal, the elastic arm plate has elasticity that presses the movable contact against the fixed contact and holds it in the on state with its own elasticity, and the elastic arm plate and the terminal plate are laminated and connected via a laser-welded weld at the laminated portion. The weld includes a linearly extending weld line. The outer casing covers the upper part of the elastic arm plate without having through holes in the laminated section. [Effects of the Invention]

[0009] The above-described circuit breaker has the advantage of stabilizing the contact state of the contacts while connecting the elastic arm plate and terminal plate by laser welding them together as separate metal plates. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of a circuit breaker according to one embodiment of the present invention. [Figure 2] Figure 1 is a vertical cross-sectional view showing the ON state of the circuit breaker. [Figure 3] Figure 2 is a vertical cross-sectional view showing the circuit breaker in the OFF state. [Figure 4] Figure 2 is a cross-sectional view of the circuit breaker between lines IV and IV. [Figure 5] Figure 2 is an exploded cross-sectional view of the circuit breaker. [Figure 6] Figure 5 is a plan view of the main body case of the circuit breaker. [Figure 7] Figure 2 is an enlarged cross-sectional view showing the contact structure of the circuit breaker. [Figure 8] This is a cross-sectional view showing the laser welding process at the laminated portion of the terminal plate and the elastic arm plate. [Figure 9] This is an enlarged plan view showing an example of a welded joint. [Figure 10]It is an enlarged plan view showing another example of a welded part. [Figure 11] It is an enlarged plan view showing another example of a welded part. [Figure 12] It is an enlarged plan view showing another example of a welded part. [Figure 13] It is an enlarged plan view showing another example of a welded part. [Figure 14] It is an enlarged plan view showing another example of a welded part. [Figure 15] It is an enlarged plan view showing another example of a welded part. [Figure 16] It is an enlarged plan view showing another example of a welded part. [Figure 17] It is an enlarged plan view showing another example of a welded part. [Figure 18] It is an enlarged plan view showing another example of a welded part. [Figure 19] It is an enlarged plan view showing another example of a welded part. [Figure 20] It is an enlarged plan view showing another example of a welded part. [Figure 21] It is a cross-sectional view showing an example of mounting the breaker shown in FIG. 2 on a circuit board. [Figure 22] It is a cross-sectional view showing another example of mounting the breaker shown in FIG. 2 on a circuit board.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail based on the drawings. In the following description, terms indicating specific directions or positions (for example, "up", "down", and other terms including those terms) are used as necessary, but the use of those terms is for facilitating the understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meanings of those terms. Also, parts denoted by the same reference numerals in a plurality of drawings indicate the same or equivalent parts or members. Furthermore, the embodiments described below illustrate specific examples of the technical concept of the present invention and do not limit the present invention to those described below. Also, the dimensions, materials, shapes, relative arrangements, etc., of the components described below are intended to be illustrative, and not to limit the scope of the present invention unless otherwise specified. Moreover, the content described in one embodiment or example is applicable to other embodiments and examples. Additionally, the size and positional relationships of the members shown in the drawings may be exaggerated for clarity.

[0012] A circuit breaker according to one embodiment of the present invention comprises a fixed contact metal plate having a fixed contact, an elastic arm plate having a movable contact at its tip located opposite the fixed contact, a terminal plate connected to the elastic arm plate, an outer casing fixing the terminal plate and the fixed contact metal plate, and a bimetal built into the outer casing that presses the elastic arm plate to separate the movable contact from the fixed contact and switch it to the off state. In the non-pressing state of the bimetal, the elastic arm plate has elasticity that presses the movable contact against the fixed contact and holds it in the on state with its own elasticity, and the elastic arm plate and the terminal plate are laminated and connected via a weld formed by laser welding of the laminated portion. The weld includes either a linearly extending weld line or a plurality of weld spots, or both.

[0013] The above circuit breaker has the feature of stabilizing the contact state of the contacts while connecting the elastic arm plate and the terminal plate by laser welding them as separate metal plates. This is because the above circuit breaker connects the laminated portion of the elastic arm plate and the terminal plate via a laser-welded section that includes either a linear welding line or multiple welding spots, or both, thereby reliably preventing relative misalignment between the elastic arm plate and the terminal plate. In particular, the elastic arm plate is not always fixed in a fixed position without deformation, but deforms each time it is switched on or off, and each time the contact is switched to the ON state the movable contact collides with the fixed contact, and each time the contact is switched to the OFF state the tip of the elastic arm plate collides with the inner surface of the case and receives an impact, so it deforms itself and receives an impact, causing the movable contact and the fixed contact to be relatively misaligned. Easy It is placed in the environment.

[0014] The above breaker uses a linear welding line or multiple welding spots to connect the elastic arm plate and the terminal plate, thereby welding the elastic arm plate and the terminal plate over a long area to prevent relative misalignment, and preventing relative misalignment of the contact area between the movable contact and the fixed contact. The movable contact and the fixed contact make local contact to become ON, but misalignment of the contact area causes a change in contact resistance. This is because the surfaces of the movable contact and the fixed contact are not always uniform across their entire surface. This is evident from the fact that even a slight misalignment of the activated contact surface rapidly increases the contact resistance. Contact can be switched on and off in a short time by ultrasonic vibration in the energized state, and activated by the discharge between the contacts that occurs at the moment of switching to OFF. 。 In this method, only the extremely narrow area where the contacts are in contact with each other in the ON state is activated. Therefore, even a slight misalignment of the contact points will cause the unactivated areas to come into contact, increasing the contact resistance. While ultrasonic vibrations in the energized state can effectively activate the contacts, even unactivated contacts are activated by the discharge that occurs between them the moment the system switches from the energized state to the OFF state. Therefore, even a slight misalignment of the contact positions of the movable and fixed contacts will increase the contact resistance.

[0015] In particular, small circuit breakers have extremely low contact pressure, and even slight displacement of the contact position can increase the contact resistance. Furthermore, the elastic arm plate deforms each time the contacts are switched on and off, and in circuit breakers where the movable contacts collide and receive impact, the relative positional displacement of the movable and fixed contacts tends to increase contact resistance. However, the above circuit breaker achieves an extremely important feature in circuit breakers: it prevents relative positional displacement of the contacts and stabilizes contact resistance with an extremely simple structure.

[0016] In another embodiment of the present invention, the breaker has a welding line that extends in the longitudinal direction of the elastic arm plate. In yet another embodiment of the present invention, the breaker has a welding section that has multiple rows of vertical welding lines, and the multiple rows of vertical welding lines are spaced apart in the width direction of the elastic arm plate.

[0017] In another embodiment of the present invention, the breaker has a weld line that extends in the width direction of the elastic arm plate. In yet another embodiment of the present invention, the breaker has a weld that has multiple rows of horizontal weld lines, and the multiple rows of horizontal weld lines are spaced apart in the longitudinal direction of the elastic arm plate.

[0018] In another embodiment of the present invention, the breaker may have a welded portion that includes a longitudinal weld line extending in the longitudinal direction of the elastic arm plate and a transverse weld line extending in the width direction of the elastic arm plate. In another embodiment of the present invention, the breaker may have a welded line that includes a corrugated weld line. In another embodiment of the present invention, the breaker has an annular weld line that extends along an annular shape. In yet another embodiment of the present invention, the breaker has an annular weld line that is circular or elliptical. Furthermore, in another embodiment of the present invention, the breaker can form a rectangular annular welding line.

[0019] In another embodiment of the present invention, the breaker may have a weld that includes both linearly extending weld lines and weld spots. In another embodiment of the present invention, the breaker has a welded portion with multiple welding spots, and the multiple welding spots are spaced apart in the longitudinal direction of the elastic arm plate. Furthermore, in another embodiment of the present invention, the breaker has a welded portion with multiple welding spots, and the multiple welding spots are spaced apart in the width direction of the elastic arm plate. In addition, in another embodiment of the present invention, The welded area has multiple welding spots, Multiple welding spots are positioned apart in the longitudinal and widthwise directions of the elastic arm plate.

[0020] In another embodiment of the present invention, the circuit breaker has activated contacts, which are fixed contacts and movable contacts that have been activated by ultrasonic vibration while energized.

[0021] In another embodiment of the present invention, the breaker has an elastic arm plate made of a metal plate that is thinner than the terminal plate.

[0022] Another embodiment of the present invention is a microbreaker in which the thickness of the elastic arm plate is 50 μm or more and 200 μm or less.

[0023] In another embodiment of the present invention, the circuit breaker has an outer casing comprising an outer perimeter wall in which a fixed contact metal plate and a terminal plate are embedded, and the inside of the outer perimeter wall is provided as a storage space for arranging an elastic arm plate, with an exposed portion in the storage space in which the surface of the terminal plate is exposed, and the terminal plate is laminated and welded to the exposed portion, and the outer perimeter wall is provided on the storage space side with a recess to enlarge the exposed area of ​​the exposed portion, and the elastic arm plate is laminated and laser welded to the exposed portion of the terminal plate. Furthermore, in another embodiment of the present invention, the breaker has an outer casing in which an elastic arm plate is arranged inside the outer peripheral wall in a fitted structure, and a clearance of 10 μm to 50 μm can be provided between the outer periphery of the elastic arm plate and the inner surface of the outer peripheral wall.

[0024] In another embodiment of the present invention, the circuit breaker has an outer casing integrally molded with a bottom plate that is in close contact with the back surface of the terminal board.

[0025] In another embodiment of the present invention, the breaker has an elastic arm plate made of a Cu-Cr-Ag-Si alloy.

[0026] In another embodiment of the present invention, the breaker is made of an elastic metal plate of a copper alloy having a total content of Cr, Ag, and Si of 0.5 to 3% by weight.

[0027] In another embodiment of the present invention, the breaker is made of an elastic metal plate of a copper alloy containing Ni, P, Zn, and Fe for the elastic arm plate.

[0028] In another embodiment of the present invention, the breaker uses an elastic metal plate made of a copper alloy containing Fe, P, and Zn as the elastic arm plate.

[0029] In another embodiment of the present invention, the breaker is made of an elastic metal plate of a copper alloy containing 75% to 95% IACS with Cr and Mg as the elastic arm plate.

[0030] In another embodiment of the present invention, the breaker uses an elastic metal plate made of a copper alloy containing 80% to 95% Zr-containing IACS as the elastic arm plate.

[0031] In another embodiment of the present invention, the breaker uses an elastic metal plate made of a copper alloy containing 80% to 95% Sn-containing IACS as the elastic arm plate.

[0032] (Embodiment 1) The circuit breaker 100 shown in Figures 1 to 6 below is built into a battery pack and cuts off the current by deforming the built-in bimetal when the battery or ambient temperature becomes high, or when the battery pack is used in an abnormal state. However, the present invention does not specify the circuit breaker or its application, and can be used in any application where a temperature rise is detected and the current is cut off, such as in a motor.

[0033] (Breaker 100) The circuit breaker 100 shown in Figures 1 to 6 comprises a fixed contact metal plate 4 having a fixed contact 5, an elastic arm plate 6 with a movable contact 7 positioned opposite the fixed contact 5, a terminal plate 3 connecting the elastic arm plate 6, a bimetal 8 positioned to switch the elastic arm plate 6 on and off, and an outer casing 1 that houses the fixed contact 5 of the fixed contact metal plate 4 and the movable contact 7 of the elastic arm plate 6, and also houses the bimetal 8. When the ambient temperature rises and the circuit breaker 100 becomes hot, it detects this temperature rise and the bimetal 8 deforms. The deforming bimetal 8 deforms the elastic arm plate 6, causing the movable contact 7 to separate from the fixed contact 5 and switch the contact to the off state. When the ambient temperature drops to a predetermined temperature, the elastic arm plate 6 and bimetal 8 return to their original state, causing the movable contact 7 to contact the fixed contact 5 and switch to the on state.

[0034] The circuit breaker 100 shown in Figures 1 to 6 has a terminal plate 3 connecting a fixed contact metal plate 4 and an elastic arm plate 6 fixed to an outer case 1, and a bimetal 8 that deforms the elastic arm plate 6 and a heater 9 that heats the bimetal 8 are built into the elastic arm plate 6. The circuit breaker 100 shown in the figures has a heater 9 built into it that heats the bimetal 8, making it ideal for applications where the bimetal 8 is heated by the heater 9 to keep the current interrupted.

[0035] (Outer case 1) The outer casing 1 consists of a plastic main body case 1A and a lid case 1B, with the lid case 1B connected to the main body case 1A. The outer casing 1 has a fixed contact metal plate 4 and a terminal plate 3 fixed to the bottom of the main body case 1A by insert molding, and the lid case 1B is fixed to the top surface. The main body case 1A has a first outer wall 11A and a second outer wall 11B protruding from both ends, and a storage space 20 is provided between the first outer wall 11A and the second outer wall 11B. In the outer casing 1 shown in the figure, the bottom surface of the storage space 20 provided in the main body case 1A is closed with the fixed contact metal plate 4, and the top surface of the storage space 20 is closed with the connecting lid case 1B.

[0036] (Main unit case 1A) The main case 1A has an outer perimeter wall 10 around the storage space 20. The outer perimeter wall 10 consists of an outer wall 11 made up of a first outer wall 11A and a second outer wall 11B, and an opposing wall 12 connecting both ends of the first outer wall 11A and the second outer wall 11B, and the opposing wall 12 and the outer wall 11 are provided around the storage space 20. The main case 1A surrounds the storage space 20 with the outer perimeter wall 10, and the bottom and top surfaces of the outer perimeter wall 10 are closed. The bottom surface of the storage space 20 is closed by a bottom 13 and a fixed contact metal plate 4 which are integrally molded with the main case 1A, and the top surface is closed by a lid case 1B which is connected to the main case 1A, making the storage space 20 a closed, hollow space.

[0037] The main case 1A is fixed by insert molding a fixed contact metal plate 4 and a terminal plate 3. The fixed contact metal plate 4 is fixed by embedding a portion of it in the first outer wall 11A. In Figures 2 and 3, the fixed contact metal plate 4 is fixed to the main case 1A by insert molding so that its intermediate portion 4B is embedded in the middle of the first outer wall 11A. This fixed contact metal plate 4 is fixed to the main case 1A in a state that it penetrates the first outer wall 11A, with a fixed contact 5 provided in the portion exposed inside the storage space 20, and a connection terminal 4X in the portion that is pulled out to the outside.

[0038] Furthermore, the main case 1A is fixed by embedding a portion of the terminal board 3 into the second outer wall 11B. In Figures 2 and 3, the terminal board 3 has its intermediate portion 3B embedded in the second outer wall 11B. One end of the terminal board 3 is exposed within the storage space 20 as an exposed portion 3A to form a laminated portion 40 for connecting the elastic arm plates 6, and the other end is brought out to the outside of the main case 1A as a connection terminal 3X. The elastic arm plates 6 are laminated on the exposed portion 3A in the storage space 20 of the terminal board 3, and the elastic arm plates 6 are laser-welded to the laminated portion 40 by irradiating it with a laser beam.

[0039] In Figures 5 and 6, the main case 1A has a recess 21 on the outer peripheral wall 10 that enlarges the exposed area of ​​the exposed portion 3A on the storage space 20 side. In Figures 5 and 6, the breaker 100 has a recess 21 in the center of the second outer wall 11B, which is the outer peripheral wall 10, on the storage space 20 side. The recess 21 is provided on the stacking portion 40 side and enlarges the exposed portion 3A for welding the elastic arm plate 6. With the exposed area of ​​the exposed portion 3A enlarged by the recess 21, the welding area of ​​the elastic arm plate 6 is enlarged, and the elastic arm plate 6 can be reliably welded. Furthermore, this second outer wall 11B has wide portions 14 on both sides of the recess 21 to increase the area that covers the surface of the terminal plate 3 and securely fixes it to the main case 1A. The exposed portion 3A is the stacking portion 40 where the elastic arm plates 6 are stacked, and a laser beam is irradiated onto the surface of the elastic arm plates 6 to laser weld the elastic arm plates 6 to the terminal plate 3. The elastic arm plate 6, which is laser-welded, is connected via a welded portion 30 formed by laser welding with the movable contact 7 positioned opposite the fixed contact 5 and one end in close contact with the exposed portion 3A of the terminal plate 3.

[0040] The main case 1A sets the elastic arm plate 6 in a fixed position and stacks the rear end 6B of the elastic arm plate 6 on top of the terminal plate 3. The stacked elastic arm plate 6 is connected to the terminal plate 3 by laser welding. The elastic arm plate 6 is attracted to a suction cup of a transport arm (not shown) provided on an automatic assembly machine (not shown) and set in a fixed position on the main case 1A. The transport arm holds the elastic arm plate 6 in a specific posture and sets the end to be welded inside the outer peripheral wall 10 of the main case 1A using a fitting structure to position it in the fixed position. The main case 1A positions the rear end 6B of the elastic arm plate 6 inside the outer peripheral wall 10 using a fitting structure to position it in the fixed position. With this structure, the main case 1A can set the elastic arm plate 6 in an accurate position by narrowing the clearance between the outer circumference of the rear end 6B of the elastic arm plate 6 and the inner surface of the outer peripheral wall 10. However, if this clearance is narrow, it becomes difficult to smoothly set the elastic arm plate 6 inside the outer peripheral wall 10. A clearance of approximately 10 μm to 50 μm is provided between the elastic arm plate 6 and the outer wall 10 so that the transport arm can quickly set the elastic arm plate 6 in the designated position on the main case 1A.

[0041] The clearance between the elastic arm plate 6 and the outer peripheral wall 10 can cause misalignment of the elastic arm plate 6 when it is set in the main case 1A. The elastic arm plate 6 is welded to the terminal plate 3 while set inside the outer peripheral wall 10 of the main case 1A. In this state, the elastic arm plate 6, positioned in the main case 1A, is welded to the terminal plate 3 and positioned in its fixed position, and its rear end 6B is further positioned inside the outer peripheral wall 10 in a fitting structure, so that the rear end 6B is also positioned in its fixed position. When the elastic arm plate 6 is securely welded to the terminal plate 3, it is positioned in its fixed position in the main case 1A. Since the fixed contact 5 is provided on the fixed contact metal plate 4 fixed to the main case 1A, in a breaker 100 where both the elastic arm plate 6 and the fixed contact metal plate 4 can be positioned in their fixed positions in the main case 1A, no misalignment of the contact position between the movable contact 7 and the fixed contact 5 occurs. The fixed contact metal plate 4 can be integrally molded with the main case 1A and positioned in a fixed location, but the elastically deformable elastic arm plate 6 is positioned in the main case 1A by connecting its rear end 6B to the terminal plate 3. Therefore, if the connection strength with the terminal plate 3 is insufficient, it cannot be positioned in the fixed location on the main case 1A. In a breaker 100 where the elastic arm plate 6 cannot be positioned in a fixed location, the movable contact 7 at the tip cannot reciprocate in a fixed position, causing the contact position with the fixed contact 5 to shift and increasing the contact resistance. In Figure 6, the elastic arm plate 6 is positioned in a fixed location on the outer case 1 by fitting its rear end 6B into the recess 21, and furthermore, the laminated portion 40 between the rear end 6B of the elastic arm plate 6 and the exposed portion 3A of the terminal plate 3 is laser-welded, so that the elastic arm plate 6 is securely fixed in the fixed location on the terminal plate 3.

[0042] Furthermore, the main case 1A shown in the cross-sectional views of Figures 2 to 5 is provided with a storage recess 29 in which the heater 9 is placed in the storage space 20. The storage recess 29 is located in the center of the storage space 20 and its bottom surface is closed by the tip 4A of the fixed contact metal plate 4. The internal shape of the storage recess 29 is slightly larger than the external shape of the heater 9 so that the heater 9 can be inserted there. The storage recess 29 is also provided with a protrusion 19 along its outer edge. The heater 9 inserted into the storage recess 29 protrudes slightly from the upper surface of the protrusion 19 and has a curved bimetal 8 on its upper surface in a thermally coupled state.

[0043] The storage space 20 is closed off by a fixed contact metal plate 4 at the bottom of the storage recess 29, and the outer bottom surface of the storage recess 29 is closed off by the plastic of the main body case 1A. The main body case 1A is fixed to the plastic bottom 13 that closes off the bottom of the storage space 20 on the outside of the storage recess 29 by insert molding the fixed contact metal plate 4 into the main body case 1A.

[0044] (Lid case 1B) As shown in Figures 2 to 5, the lid case 1B is positioned on the opening side of the main case 1A, covering the upper part of the elastic arm plate 6. The lid case 1B shown in the figures is made of plastic and is fixed to the main case 1A by fixing its outer peripheral edge to the upper surface of the outer peripheral wall 10 of the main case 2. As shown in Figure 5, the lid case 1B has an outer peripheral wall 22 that protrudes toward the main case 1A on the outer peripheral edge opposite the outer peripheral wall 10 of the main case 1A. The inside of this outer peripheral wall 22 is shaped as a recess with a downward opening, forming a storage section 23 for housing the elastic arm plate 6 which is elastically deformed when pressed by the bimetal 8. The outer peripheral wall 22 of the lid case 1B is fixed to the first outer wall 11A and the second outer wall 11B provided at both ends of the main case 1A, and is further fixed to the opposing wall 12. The plastic lid case 1B is connected to the main case 1A by ultrasonic welding.

[0045] The outer case 1 shown in Figures 5 and 6 is equipped with connecting protrusions 17 and connecting recesses 18 that fit together to connect the lid case 1B and the main body case 1A while precisely positioning them. The lid case 1B shown in Figure 5 is provided with connecting protrusions 17 on both sides of the end of the main body case 1A on the first outer wall 11A side, protruding from the lower surface of the outer peripheral wall 22 toward the main body case 1A. As shown in Figure 6, the main body case 1A is provided with connecting recesses 18 on the upper surface of the outer peripheral wall 10 facing these connecting protrusions 17 to guide the connecting protrusions 17. Furthermore, the lid case 1B shown in Figure 5 is provided with a fitting protrusion 16 that fits into the open end of a recess 21 provided on the second outer wall 11B side of the main body case 1A and is positioned on the upper surface of the laminated portion 40 of the elastic arm plate 6. The outer shape of this fitting projection 16 approximates the planar shape of the recess 21 and is shaped to fit into the stepped recess 24 formed on the upper surface side of the rear end portion 6B of the elastic arm plate 6 which is fitted into the recess 21.

[0046] In the above-described outer case 1, at the end of the main body case 1A on the first outer wall 11A side, the connecting protrusions 17 on both sides of the lid case 1B are guided into the connecting recesses 18 of the main body case 2, and at the end of the main body case 2 on the second outer wall 11B side, the fitting protrusions 16 of the lid case 1B are guided into the stepped recesses 24 formed on the upper surface side of the laminated portion 40 of the elastic arm plate 6, thereby connecting the lid case 1B to the main body case 1A in the correct position.

[0047] (Fixed contact metal plate 4) The fixed contact metal plate 4 is insert-molded and fixed to the main case 1A. The fixed contact metal plate 4 is insert-molded so that its tip portion 4A closes the opening at the bottom 13 of the storage space 20, and the middle portion 4B and a part of the tip portion 4A are embedded in the first outer wall 11A of the main case 1A from the bottom 13 of the storage space 20, and fixed to the main case 1A. In Figures 2 and 3, the fixed contact metal plate 4 has a stepped portion so that the portion embedded in the first outer wall 11A is higher than the portion that closes the bottom of the storage recess 29, and the stepped portion is embedded in the bottom 13 of the main case 1A, with the rear end of the stepped portion 4D exposed on the upper surface of the bottom 13, and this exposed portion serves as the fixed contact 5.

[0048] As shown in Figure 7, the fixed contact metal plate 4 has a silver inlay material 35 pressed into it to form the fixed contact 5. The metal plate of the fixed contact 5 is made of copper, copper alloy, nickel, or nickel alloy. The inlay material 35 can be made thicker to extend the life of the contact, so its thickness is set to 200 μm. However, although not shown, the surface of the fixed contact metal plate 4 can be silver plated, and the silver plated layer can serve as the fixed contact. The silver plated layer of the fixed contact is thicker than the silver plated layer 37 of the movable contact, for example, 6 μm. However, the film thickness of the silver plated layer of the fixed contact can be 5 μm to 100 μm, preferably 3 μm to 50 μm, which is thicker than that of the movable contact. By making the silver plated layer of the fixed contact thicker, the fixed contact can be connected to a polarity that is prone to damage, thereby extending the life of the connection.

[0049] The connection terminals 4X of the fixed contact metal plate 4 are bent so that the connection surface (bottom surface in Figures 2 and 3) of the tip that extends outward from the outer case 1 is positioned almost flush with the bottom surface of the outer case 1, i.e., the bottom surface of the main case 1A, so that they can be fixed to the surface of the circuit board by soldering with reflow solder or the like. This breaker 100 is heat-treated and reflow-soldered with the connection terminals 4X positioned on the solder surface of the circuit board. However, the breaker can also be constructed by using the exposed portion of the fixed contact metal plate 4 that is exposed from the bottom surface of the insulating case 2 as the exposed terminal 44, and reflow-soldering this exposed terminal 44 to the solder surface of the circuit board. This breaker can be fixed by soldering the exposed terminal 44 of the fixed contact metal plate 4 to the surface of the circuit board, etc., without necessarily extending the connection terminals 4X outward from the outer case 1.

[0050] (Terminal board 3) The terminal board 3 is insert-molded and fixed to the main case 1A. The terminal board 3 is insert-molded so that its tip is exposed in the storage space 20 as an exposed portion 3A for connecting the elastic arm plate 6, and its middle portion 3B is embedded in the second outer wall 11B, and is fixed to the main case 1A. The connection terminals 3X of the terminal board 3 are bent so that the connection surface of the tip that extends outward from the outer case 1 (bottom surface in Figures 2 and 3) is positioned almost flush with the bottom surface of the outer case 1, i.e., the bottom surface of the main case 1A, so that they can be fixed to the circuit board by soldering such as reflow soldering. This breaker 100 is heat-treated and reflow-soldered with the connection terminals 3X positioned on the solder surface of the circuit board.

[0051] (Welded section 30) Conventional circuit breakers connect the elastic arm plate and terminal plate by spot welding. However, the strength of the weld connecting the elastic arm plate and terminal plate is insufficient, making it difficult to keep the elastic arm plate in a fixed position over long periods. In particular, in main body cases where the rear end of the elastic arm plate is fitted inside the outer wall, there is a clearance between the elastic arm plate and the outer wall. Therefore, while the elastic arm plate is positioned in a fixed position by the fitting structure, the contact position of the movable contact and the fixed contact cannot be kept constant. The misalignment of the contact position of the movable contact and the fixed contact causes fluctuations in the contact resistance. In particular, in micro-circuit breakers that use an extremely thin metal plate for the elastic arm plate, the contact pressure of the contacts is considerably small, less than 10g, making it difficult to maintain low contact resistance. An increase in contact resistance leads to an increase in Joule heat due to the current, causing damage to the contacts and accelerating the increase in contact resistance. It also causes various problems such as thermal deformation of the plastic outer case.

[0052] The terminal plate 3 is connected to the elastic arm plate 6 by laser welding. The terminal plate 3 is welded to the surface of the elastic arm plate 6, which is laminated on the exposed portion 3A, by irradiating it with a laser beam. Laser welding preferably uses a fiber laser beam to melt and weld both the elastic arm plate 6 and the terminal plate 3. The elastic arm plate 6 and the terminal plate 3 are in close contact with each other without any gaps when the laser beam is irradiated onto their surfaces. Any gaps between the elastic arm plate 6 and the terminal plate 3 would hinder the stability of the weld. To ensure that the elastic arm plate 6 and the terminal plate 3 are in close contact without any gaps, the surface of the elastic arm plate 6 is pressed by a pusher 51, as shown in Figure 8. The pusher 51 that presses the elastic arm plate 6 against the terminal plate 3 presses near the welding area 30 to which the laser beam 50 is irradiated, for example, on both sides or around the welding area 30, so that the elastic arm plate 6 is in close contact with the terminal plate 3 and the laser beam 50 is irradiated.

[0053] In the cross-sectional view of Figure 8, the outer case 1 is provided with a bottom plate 15 on the back surface of the exposed portion 3A of the terminal board 3 so that it is in close contact with the surface of the terminal board 3 when the elastic arm plate 6 is pressed by the pusher 51. The bottom plate 15 is integrally molded with the main case 1A so as to be in close contact with the terminal board 3. In this breaker 100, when the elastic arm plate 6 is pressed by the pusher 51, the bottom plate 15 supports the lower surface of the terminal board 3, causing the elastic arm plate 6 to be in close contact with the surface of the terminal board 3. In the process of welding the elastic arm plate 6 to the terminal board 3, the outer case 1 is placed on a flat base plate 52 and the elastic arm plate 6 is pressed to make it adhere to the terminal board 3. When the elastic arm plate 6 is pressed by the pusher 51, the terminal board 3 is supported by the base plate 52 via the bottom plate 15. Therefore, with the pusher 51 pressing against the elastic arm plate 6, the stacked elastic arm plate 6 and terminal plate 3 are sandwiched between the pusher 51 and the bottom plate 15, creating a tight, gap-free seal. This breaker 100 structure has the advantage of being able to be mass-produced efficiently because the main body case 1A is placed on a flat base plate 52, the elastic arm plate 6 is pressed against the terminal plate 3, and then laser-welded. This is because it does not require high-precision adjustment of the position in which the main body case 1A is set on the base plate 52. Furthermore, in this structure, with the pusher 51 pressing against the elastic arm plate 6, the thermoplastic plastic bottom plate 15 acts as a buffer layer. As a result, the bottom plate 15 absorbs errors in the pressing position of the pusher 51, and the pressing force between the elastic arm plate 6 and the terminal plate 3 can be adjusted to an optimal state.

[0054] The main body case 1A in Figure 8 has an opening 15A in the bottom plate 15, and a support rib 53 protruding from the base plate 52 that directly supports the lower surface of the terminal board 3. The opening 15A of the bottom plate 15 is located on the lower surface of the exposed portion 3A of the terminal board 3. The main body case 1A is set in place on the base plate 52 by guiding the support rib 53 into the opening 15A. With the support rib 53 supporting the lower surface of the terminal board 3, the elastic arm plate 6, which is laminated on the terminal board 3, is pressed by the pusher 51, and the elastic arm plate 6 and the terminal board 3 are laser welded together in close contact.

[0055] The elastic arm plate 6, which has a movable contact 7 fixed to its tip, is connected to the terminal plate 3 at its rear end 6B by laser welding. Laser welding involves locally irradiating the elastic arm plate 6 and the terminal plate 3 with a laser beam to melt and spot weld them together. The elastic arm plate 6, connected to the terminal plate 3 by spot welding, is switched to the off state by being pushed by the reversing bimetal 8, and then switched back to the on state when the bimetal 8 returns to its original position. The elastic arm plate 6 can be switched from the off state by separating the movable contact 7 from the fixed contact 5, to the on state by contacting the fixed contact 5. However, since the movable contact 7 is located at the tip and the rear end 6B is fixed to the terminal plate 3, even a slight misalignment of the rear end 6B will result in a larger misalignment of the movable contact 7 at the tip. Therefore, even a slight misalignment of the rear end 6B of the elastic arm plate 6 can cause a shift in the contact position between the movable contact 7 and the fixed contact 5. Even a slight shift in the contact position between the movable contact 7 and the fixed contact 5 will cause a change in contact resistance. Locally spot-welded elastic arm plates make it difficult to prevent the contact position from shifting over long periods due to the reciprocating motion of the movable contacts.

[0056] Furthermore, in laser welding, various external conditions such as temperature and surface condition can cause fluctuations in the weld state, making it difficult to reliably connect the elastic arm plate and the terminal plate and reliably prevent misalignment of the contact position in all breakers produced in large quantities. Moreover, the bimetal instantly reverses when the ambient temperature reaches the set temperature and instantly returns to its original position when the ambient temperature drops to the return temperature, impacting the elastic arm plate. This also makes it difficult to reliably fix the elastic arm plate to the terminal plate over a long period of time. In addition to this, in microbreakers, which are extremely small overall, even a slight misalignment of the contact position increases the contact resistance. This is because the contact pressure between the movable contact and the fixed contact is weak, and in the ON state, the movable contact and the fixed contact are in contact in an extremely narrow local area. Furthermore, the surfaces of the movable and fixed contacts of the breaker are not always kept uniform across the entire surface, and the contact resistance increases in the non-contacting areas compared to the areas that are always in contact due to thin oxide films and other factors.

[0057] Microbreakers employ an activation process to reduce the contact resistance of their contacts. This activation process involves applying ultrasonic vibrations while the contacts are energized in the ON state. Contacts activated in this way have reduced contact resistance only when the movable and fixed contacts are in contact at specific positions; therefore, if the contact positions shift, the contact resistance increases.

[0058] Figures 9 to 20 show a welded joint 30 that fixes the elastic arm plate 6 to the terminal plate 3 while preventing displacement. The welded joint 30 between the elastic arm plate 6 and the terminal plate 3 shown in these figures can be a linear, elongated weld line 31, or welded with multiple welding spots 32, or welded with both a linear weld line 31 and multiple welding spots 32.

[0059] In Figure 9, the welded portion 30 has a weld line 31 which is a vertical weld line 31A extending in the longitudinal direction of the elastic arm plate 6. In this figure, the vertical weld line 31A is a straight line parallel to the longitudinal direction of the elastic arm plate 6, but the vertical weld line 31A can also be a straight line extending in a direction inclined in the longitudinal direction of the elastic arm plate 6, or it can be a curved shape. In this figure, the vertical weld line 31A extends in the longitudinal direction of the elastic arm plate 6 (the X-axis direction in the figure), so even when elastically deformed to curve in the X-axis direction, the region of the laminated portion 40 of the elastic arm plate 6 that extends in the X-axis direction, i.e., the region from part a to part b, can be in close contact with the terminal plate 3. This prevents misalignment of the contact position between the movable contact 5 and the fixed contact 7, and realizes the feature of stabilizing the contact pressure of the contacts.

[0060] In Figure 10, the welded section 30 has multiple rows of vertical welded lines 31A arranged with the weld line 31 spaced apart in the width direction of the elastic arm plate 6. Although the welded section 30 in this figure has two rows of vertical welded lines 31A, it is also possible to have three or more rows of vertical welded lines 31A. Furthermore, although the vertical welded lines 31A in this figure are straight lines parallel to the longitudinal direction of the elastic arm plate 6, the vertical welded lines 31A can also be straight lines extending in a direction inclined in the longitudinal direction of the elastic arm plate 6, or they can be curved. In the welded section 30 in this figure, multiple vertical welded lines 31A extending in the longitudinal direction of the elastic arm plate 6 are spaced apart in the width direction, so the laminated section 40 can be in close contact with the terminal plate 3 in both the X-axis and Y-axis directions. Therefore, this welded section 30 can reliably prevent misalignment of the contact position between the movable contact and the fixed contact in both the X-axis and Y-axis directions. Furthermore, this welded joint 30 also has the advantage of being able to stabilize the contact pressure at the contact point.

[0061] In Figure 11, the welded portion 30 has a weld line 31 that is a lateral weld line 31B extending in the width direction of the elastic arm plate 6. In this figure, the lateral weld line 31B is a straight line parallel to the width direction of the elastic arm plate 6, but the lateral weld line 31B can also be a straight line extending in a direction inclined in the width direction of the elastic arm plate 6, or it can be a curved shape. In this figure, the lateral weld line 31B extends in the width direction of the elastic arm plate 6 (Y-axis direction in the figure), so when the elastic arm plate 6 is elastically deformed, the region of the laminated portion 40 of the elastic arm plate 6 that extends in the Y-axis direction, that is, the region from c to d, can be brought into close contact with the terminal plate 3. This prevents the contact position of the movable contact 7 and the fixed contact 5 from shifting in the width direction, and the contact pressure of the contacts can also be stabilized.

[0062] In Figure 12, the welded section 30 has multiple rows of horizontal welded lines 31B arranged separately in the longitudinal direction of the elastic arm plate 6. Although the welded section 30 in this figure has two rows of horizontal welded lines 31B, it is also possible to have three or more rows of horizontal welded lines 31B. Furthermore, although the horizontal welded lines 31B in this figure are straight lines parallel to the width direction of the elastic arm plate 6, the horizontal welded lines 31B can also be straight lines extending in a direction inclined in the width direction of the elastic arm plate 6, or they can be curved. In the welded section 30 in this figure, multiple horizontal welded lines 31B extending in the width direction of the elastic arm plate 6 are arranged separately in the longitudinal direction, so the laminated section 40 can be in close contact with the terminal plate 3 in both the X-axis and Y-axis directions. Therefore, this welded section 30 can reliably prevent misalignment of the contact position between the movable contact 7 and the fixed contact 5 in both the X-axis and Y-axis directions. Furthermore, this welded joint 30 also has the advantage of being able to stabilize the contact pressure at the contact point.

[0063] The welded sections 30 in Figures 13 and 14 have a weld line 31 that is an annular weld line 31X extending along the annular shape. In Figure 13, the annular weld line 31X of the welded section 30 is circular, while in Figure 14, the annular weld line 31X is elliptical. These annular weld lines 31X are substantially identical in shape to those with two rows of curved line sections 31C extending vertically and two rows of curved line sections 31D extending horizontally at opposing positions, so that the laminated section 40 can be in close contact with the terminal plate 3 in both the X-axis and Y-axis directions. Therefore, these welded sections 30 also have the advantage of reliably preventing misalignment of the contact position between the movable contact 7 and the fixed contact 6 in both the X-axis and Y-axis directions, thereby stabilizing the contact pressure of the contacts.

[0064] Furthermore, the welded portion 30 can also be shaped such that a part of the annular weld line 31X is composed of a vertical weld line portion 31A extending in the longitudinal direction of the elastic arm plate 6, or a part of the annular weld line 31X is composed of a horizontal weld line portion 31B extending in the width direction of the elastic arm plate 6. For example, the annular weld line 31X shown in Figure 15 has an overall shape that is roughly rectangular, with two rows of vertical weld line portions 31A and two rows of horizontal weld line portions 31B provided at opposing positions and connected to each other. Also, the annular weld line 31X shown in Figure 16 has an overall shape that is oval, with two rows of horizontal weld line portions 31B provided separately in the longitudinal direction and connected at both ends by a curved line portion 31C. These welded portions 30 also have the feature of being able to reliably prevent misalignment of the contact position between the movable contact 7 and the fixed contact 5 in both the X-axis direction and the Y-axis direction, thereby stabilizing the contact pressure of the contacts.

[0065] Furthermore, in the welded section 30 shown in Figure 17, the welding line 31 is a corrugated welding line 31Y. The corrugated welding line 31Y shown in the figure is a roughly sinusoidal wave that extends in the width direction of the elastic arm plate 6. This corrugated welding line 31Y is formed by arranging multiple inclined line sections 31E that extend in an inclined position in the longitudinal direction, with the inclination directions alternating and opposite, and by connecting adjacent inclined line sections 31E with curved line sections 31D to form a wave shape that extends in the width direction, so that the laminated section 40 can be in close contact with the terminal plate 3 in both the X-axis and Y-axis directions. However, although not shown, the corrugated welding line can also be a wave shape that extends in the longitudinal direction of the elastic arm plate. Furthermore, the corrugated welding line 31Y is not limited to a sinusoidal wave, but can also be a triangular wave, a rectangular wave, or a trapezoidal wave. For example, a corrugated welding line, which has an overall rectangular wave shape, can reliably prevent positional displacement in both the X-axis and Y-axis directions by connecting a longitudinal welding line section that extends in the longitudinal direction with a transverse welding line section that extends in the width direction.

[0066] Furthermore, the welded portion 30 in Figure 18 has multiple welding spots 32, which are spaced apart in the longitudinal direction of the elastic arm plate 6. In this welded portion 30, two welding spots 32 are provided spaced apart in the longitudinal direction of the elastic arm plate 6, but it is also possible to provide three or more welding spots 32. The welded portion 30 in this figure has multiple welding spots 32 provided spaced apart in the longitudinal direction of the elastic arm plate 6, so the region of the laminated portion 40 of the elastic arm plate 6 that extends in the X-axis direction, that is, the region from section e to section f, is in close contact with the terminal plate 3, which has the advantage of preventing misalignment of the contact position between the movable contact 7 and the fixed contact 5, while stabilizing the contact pressure of the contacts.

[0067] Furthermore, the welded portion 30 in Figure 19 has multiple welding spots 32 arranged spaced apart in the width direction of the elastic arm plate 6. In this figure, the welded portion 30 has two welding spots 32 spaced apart in the width direction of the elastic arm plate 6, but it is also possible to have three or more welding spots 32. In this figure, the welded portion 30 has multiple welding spots 32 spaced apart in the width direction of the elastic arm plate 6, so that when the elastic arm plate 6 is elastically deformed, the region extending in the width direction of the laminated portion 40 of the elastic arm plate 6, that is, the region from g to h, can be in close contact with the terminal plate 3. This prevents the contact positions of the movable contact 7 and the fixed contact 5 from shifting in the width direction, and the contact pressure of the contacts can also be stabilized.

[0068] Furthermore, the welded portion 30 in Figure 20 has multiple welding spots 32 arranged apart in the longitudinal and width directions of the elastic arm plate 6. The welded portion 30 in the figure has two welding spots 32 spaced apart in both the longitudinal and width directions, for a total of four welding spots 32, but it is also possible to have three or more welding spots 32 in both the longitudinal and width directions. Because the welded portion 30 in this figure has multiple welding spots 32 spaced apart in both the longitudinal and width directions of the elastic arm plate 6, the laminated portion 40 can be in close contact with the terminal plate 3 in both the X-axis and Y-axis directions. Therefore, this welded portion 30 can reliably prevent misalignment of the contact position between the movable contact 7 and the fixed contact 5 in both the X-axis and Y-axis directions. Furthermore, this welded portion 30 also has the advantage of being able to stabilize the contact pressure of the contacts.

[0069] (Contact activation process) Microbreakers with low contact pressure can have their contact resistance reduced by activating the contacts in their assembled state. The contact activation process is performed by ultrasonically vibrating the contacts of the assembled breaker 100 while current is flowing through them. The breaker 100 is ultrasonically vibrated so that the movable contact 7 and the fixed contact 5 collide with each other and move away from each other. That is, the breaker 100 is ultrasonically vibrated so that the fixed contact 5 and the movable contact 7 move relatively towards and collide with each other, and then move away from each other. The contact current during ultrasonic vibration is preferably 0.1A to 100A under resistive load conditions. Increasing the contact current during ultrasonic vibration activates the contacts more effectively. In an inductive load with a coil connected in series with a resistor, the current energy stored in the coil increases when the current is interrupted, so the contact current can be reduced to activate the contacts. This is because the discharge current of the contacts increases to consume the current energy stored in the coil. Therefore, the contact current is set to an optimal value considering both resistive and inductive loads. Furthermore, the circuit breaker 100 has the characteristic that when the current through the contacts is increased, it generates heat through Joule heating and switches itself to the off state. In order to activate the contacts with ultrasonic vibration, it is necessary to keep the movable contact 7 in the ON state, in contact with the fixed contact 5. Therefore, the method of passing a large current through the contacts to cause ultrasonic vibration should be shortened so that the ultrasonic vibration occurs while the contacts are in the ON state.

[0070] The time for ultrasonic vibration of the contacts while energized should be between 0.1 milliseconds and 1 second. While a longer ultrasonic vibration time can activate the contacts more effectively, excessively long vibrations can damage the silver plating layer. Therefore, the time should be set to activate the contacts without damaging the silver plating layer. Furthermore, the activation of the contacts by ultrasonic vibration is also affected by the contact current, the type of load, and the amplitude of the ultrasonic vibration. Larger contact currents and amplitudes result in more effective activation in a shorter time. Therefore, the ultrasonic vibration time should be set to an optimal value within the aforementioned range, taking into account the contact current and the amplitude of the ultrasonic vibration.

[0071] Furthermore, the frequency used to ultrasonically vibrate the contacts is set to 20 kHz to 6 GHz, preferably 20 kHz to 1 GHz. Increasing the ultrasonic vibration frequency increases the number of collisions and separations between the movable contact 7 and the fixed contact 5 per unit time. However, if the ultrasonic vibration frequency is too high, the distance between the movable contact 7 and the fixed contact 5 becomes narrower, reducing activation by discharge. Conversely, if the frequency is too low, the number of collisions decreases, reducing activation. Therefore, the ultrasonic vibration frequency is set to an optimal value considering the thickness and length of the elastic arm plate 6, as well as the resonant frequency of the elastic arm plate 6.

[0072] Furthermore, the amplitude of ultrasonic vibration of the breaker 100 is set to 0.01 μm to 100 μm. Increasing the amplitude of ultrasonic vibration increases the kinetic energy of the movable contact 7 as it collides with the fixed contact 5, and also increases the distance at which the movable contact 7 separates from the fixed contact 5. The amplitude of ultrasonic vibration of the breaker 100 affects the distance at which the movable contact 7 separates from the fixed contact 5. However, the distance at which the movable contact 7 separates from the fixed contact 5 can be made greater than the amplitude of ultrasonic vibration of the breaker 100 by resonating the elastic arm plate 6. Therefore, by setting the frequency of ultrasonic vibration of the breaker 100 to the resonant frequency of the elastic arm plate 6, its vicinity, an integer multiple of that resonant frequency, or an integer fraction of the resonant frequency, the movable contact 7 can be moved to a sufficient distance from the fixed contact 5 and effectively activated.

[0073] To increase the amplitude of ultrasonic vibration of the circuit breaker 100, it is necessary to increase the output of the ultrasonic transducer or ultrasonic horn that contacts the circuit breaker 100 and causes ultrasonic vibration. However, if a high-output ultrasonic transducer or ultrasonic horn is pressed against the outer casing 1 of the circuit breaker 100 and causes ultrasonic vibration, problems such as deformation of the contact point with the ultrasonic transducer due to heat generated by the ultrasonic vibration may occur. Therefore, the amplitude of ultrasonic vibration of the circuit breaker 100 is set to be small enough to activate the contacts.

[0074] (Heater 9) The heater 9 generates heat when energized, heating the bimetal 8. The heater 9 is a thick PTC heater with oval or rectangular opposing surfaces and electrodes on its top and bottom surfaces. However, it is not necessary to use a PTC heater; any heater that can heat the bimetal 8 when energized can be used. The heater 9, which has electrodes on its top and bottom surfaces, has its bottom surface in contact with the fixed contact metal plate 4 and its top surface in contact with the elastic arm plate 6 via the bimetal 8. When the movable contact 7 of the elastic arm plate 6 is in the ON state, in contact with the fixed contact 5, the elastic arm plate 6 and the bimetal 8 are not in contact and no energy is supplied. When the movable contact 7 of the elastic arm plate 6 is separated from the fixed contact 5 and in the OFF state, the heater 9 generates heat by supplying energy through the bimetal 8 in contact with the elastic arm plate 6 and the fixed contact metal plate 4, heating the bimetal 8. The heated bimetal 8 maintains the OFF state, separating the movable contact 7 from the fixed contact 5, as shown in Figure 3. This non-powered type circuit breaker 100 can be safely used with a battery pack because, when switched to the off state, it keeps the movable contact 7 in the off state. This is because, after the battery pack is used in an abnormal state and the temperature rises above the set temperature, and the non-powered type circuit breaker 100 switches to the off state, power continues to flow from the battery in the battery pack to the heater 9, heating the bimetal 8. As a result, the circuit breaker 100 does not return to the on state and remains in a state of interrupting the current until the battery is discharged.

[0075] However, circuit breakers are not necessarily limited to structures that incorporate a heater. In circuit breakers without a built-in heater, when the bimetallic strip becomes deformed due to exceeding the set temperature, and deforms the elastic arm plate to switch the contacts to the off state, the circuit breaker does not heat the bimetallic strip to keep the breaker in the off state. Instead, when the bimetallic strip cools down to a predetermined temperature, the bimetallic strip and the elastic arm plate return to their original state, switching the breaker to the on state.

[0076] (Bimetal 8) The bimetal 8 is made of stacked metals with different coefficients of thermal expansion so that it deforms when heated. The bimetal 8 is positioned between the heater 9 and the elastic arm plate 6 and deforms by reversing when heated, separating the movable contact 7 from the fixed contact 5 and switching the breaker 100 to the OFF state. The bimetal 8 has a curved shape with a central convexity. When it is not thermally deformed, that is, when the movable contact 7 is in contact with the fixed contact 5, it is positioned with the central protrusion protruding towards the elastic arm plate 6, as shown in Figure 2. When it deforms by thermal deformation and reverses, it is positioned with the central protrusion protruding towards the heater 9, as shown in Figure 3. As shown in Figure 3, when the bimetal 8 is thermally deformed and reverses, it brings the central protrusion into contact with the heater 9 and presses both ends against the elastic arm plate 6, pushing up the movable portion 6A of the elastic arm plate 6 and separating the movable contact 7 from the fixed contact 5, switching it to the OFF state.

[0077] (Elastic arm plate 6) As shown in Figures 2 and 3, the elastic arm plate 6 has a movable contact 7 at its tip that is positioned opposite to the fixed contact 5. Its rear end 6B is laminated to the exposed portion 3A of the fixed contact metal plate 3 and fixed by laser welding, and the movable portion 6A, which is the middle part, is arranged inside the storage space 20. The elastic arm plate 6 is an elastic metal plate that can be elastically deformed when placed in the storage space 20. This elastic arm plate 6 is a Cu-Cr-Ag-Si alloy. The Cu-Cr-Ag-Si alloy contains Cu as the base material, 0.01 to 5 wt%, preferably 0.01 to 2.5 wt%, of Cr, 0.01 to 5 wt%, preferably 0.01 to 2.5 wt%, of Ag, and 0.01 to 5 wt%, preferably 0.01 to 2.5 wt%, of Si. Furthermore, the elastic arm plate may be an elastic metal plate (QMET 300, a registered trademark of Materion Performance Alloys and Composites USA) made of a copper alloy with a total content of 0.5 to 3% by weight of Cr, Ag, and Si, and an IACS of 78% to 84%. In addition, the elastic arm plate 6 can also be an elastic metal plate such as a copper alloy containing Ni, P, Zn, and Fe; a copper alloy containing Fe, P, and Zn; a copper alloy containing Cr and Mg with an IACS of 75% to 95%; a copper alloy containing Zr with an IACS of 80% to 95%; or a copper alloy containing Sn with an IACS of 80% to 95%. However, IACS (International Annealed Copper Standard) is an internationally adopted standard for annealed copper (volume resistivity of 1.7241 × 10⁻¹⁰) as a standard for electrical resistance or electrical conductivity. -2 This notation specifies conductivity (μΩm) as 100%.

[0078] Furthermore, the elastic arm plate 6 has a movable contact 7 on the tip of the movable part 6A, on the surface facing the fixed contact 5. The movable contact 7 of the elastic arm plate 6 shown in Figure 7 has a silver plating layer 37 in the region facing the fixed contact 5, which reduces contact resistance with the fixed contact 5. When the bimetal 8 is not thermally deformed, the movable contact 7 contacts the fixed contact 5 and the elastic arm plate 6 is in the ON state. When the bimetal 8 is thermally deformed, the movable part 6A, which is pressed by the bimetal 8, elastically deforms, and the movable contact 7 separates from the fixed contact 5 and the elastic arm plate 6 is in the OFF state. The non-energized type breaker 100 shown in Figures 2 and 3 has a pressing projection 25 that protrudes from the inner surface of the lid case 1B to press the rear end side of the movable part 6A downward, so that the movable contact 7 can be reliably made to contact the fixed contact 5 when the bimetal 8 is not thermally deformed. The elastic arm plate 6 is biased downward by the pressing projection 25 at the rear end of the movable part 6A, thereby ensuring that the tip of the movable part 6A makes secure contact with the fixed contact 5 at the tip of the movable contact 7.

[0079] Furthermore, the breaker 100 in Figures 2 and 3 is provided with a deformation-restricting projection 26 on the lid case 1B. The deformation-restricting projection 26 is located at the tip of the movable part 6A, i.e., the side of the movable contact 7, and protrudes toward the movable part 6A, in order to limit the amount of deformation that occurs when the movable part 6A of the elastic arm plate 6 is pushed by the bimetal 8 in the off state, when the bimetal 8 is thermally deformed and the movable contact 7 separates from the fixed contact 5. This breaker 100 can limit the amount of deformation that occurs when the movable part 6A is pushed up by the inverted bimetal 8 by the deformation-restricting projection 26, i.e. toward the fixed contact 5. Therefore, the breaker 100 with this structure has the advantage of preventing the inverted bimetal 8 from pushing up the movable part 6A of the elastic arm plate 6 beyond its elastic limit and reducing its springiness, and after returning to its original state, it can press the movable contact 7 against the fixed contact 5 with a predetermined contact pressure and maintain low contact resistance.

[0080] Furthermore, the elastic arm plate 6 shown in Figures 2 to 5 has protrusions 6C on its lower surface, and both ends of the bimetal 8 are brought into contact with these protrusions 6C to press against each other. The protrusions 6C shown in the figures have an arc shape on their outer surface, ensuring that both ends of the bimetal 8 make contact and press against each other without sliding laterally. The elastic arm plate 6 shown in the figures has multiple protrusions 6C on its lower surface facing both ends of the bimetal 8. This structure ensures that even a wide bimetal 8 can be reliably brought into contact and pressed against each other.

[0081] As shown in Figures 1 to 4, the circuit breaker 100 is fixed to the circuit board 60 by soldering the connection terminals 3X of the terminal plate 3 and the connection terminals 4X of the fixed contact metal plate 4, which are drawn out from both ends of the outer casing 1, to the circuit board 60, as shown in Figure 21. The circuit breaker 100 is placed on the circuit board 60 with the bottom surface of the outer casing 1, i.e., the bottom surface of the main body case 1A, facing the top surface of the circuit board 60, and then soldered. The circuit breaker 100 is heat-treated and reflow-soldered with the connection terminals 3X and 4X provided at both ends of the outer casing 1 positioned on the solder surface 61 provided on the surface of the circuit board 60. The circuit breaker 100 is connected to the solder surface 61 of the circuit board 60 via the connection terminals 3X and 4X, and is fixed in a fixed position on the circuit board 60.

[0082] Furthermore, the circuit breaker 100 shown in Figure 22 is fixed to the circuit board 60 by soldering the connection terminal 3X of the terminal plate 3, which is drawn out from one end of the outer case 1, and the exposed terminal 44 of the fixed contact metal plate 4, which is exposed from the bottom surface of the main case 1A. Since this circuit breaker 100 connects the exposed terminal 44 of the fixed contact metal plate 4 to the circuit board 60, the connection terminal 4X shown in Figure 2 is cut off at the dashed line portion of the figure. This circuit breaker 100 is also placed on the upper surface of the circuit board 60 with the bottom surface of the outer case 1, i.e., the bottom surface of the main case 1A, facing the upper surface of the circuit board 60, and then soldered. This circuit breaker 100 is heat-treated and reflow-soldered with the connection terminal 3X provided at one end of the outer case 1 and the exposed terminal 44 exposed from the bottom surface of the main case 1A positioned on the solder surface 61 provided on the surface of the circuit board 60. The circuit breaker 100 is connected to the solder side 61 of the circuit board 60 via the connection terminal 3X and the exposed terminal 44, and is fixed in place on the circuit board 60.

[0083] [Example 1] A prototype circuit breaker was fabricated using a Cu-Cr-Ag-Si alloy with a thickness of 100 μm for the elastic arm plate 6, with a length of 3.3 mm and a width of 1 mm, a movable contact 7 provided at the tip of the elastic arm plate 6, the surface of which the movable contact 7 is coated with a 5 μm silver plating layer 37, and the fixed contact 5 is made of an inlay material 35 (AgNi) with a thickness of 30 μm. As shown in Figure 9, the length of the vertical welding line section 31A is 0.5 mm, and the outer dimensions of the outer case 1 are 4 mm in length, 2.5 mm in width, and 1.05 mm in height. When 100 prototype circuit breakers were fabricated using this circuit breaker with a contact current of 20 A, an ultrasonic vibration frequency of 100 KHz, a vibration amplitude of 5 μm, and an ultrasonic vibration time of 10 msec, the on-resistance of this circuit breaker, including the contact resistance, was 4.1 mΩ on average. For comparison, the on-resistance of the contacts before activation treatment was 7.0 mΩ on average. Furthermore, this circuit breaker exhibits extremely excellent characteristics, with an increase in contact resistance of less than 0.5 mΩ after 12,000 on / off cycles under a resistive load with a contact current of 18 A.

[0084] The Cu-Cr-Ag-Si alloy used in Example 1 had the following composition. Cu………97.5wt% Cr...1.0wt% Ag………1.0wt% Si... 0.5 wt

[0085] [Examples 2 and 3] The circuit breaker in Example 2 is the same as in Example 1, but the welded section 30 has a length of 0.5 mm and consists of two rows of vertical welded lines 31A as shown in Figure 10, and the circuit breaker in Example 3 is the same as in Example 1 except that it has two rows of horizontal welded lines 31B as shown in Figure 12. The on-resistance before activation treatment is 6.7 mΩ and the contact resistance after activation treatment is 4.0 mΩ. Furthermore, when a contact current of 12 A is passed through the contacts with a resistive load, the increase in the contact resistance of the contacts after 20,000 on / off cycles is less than 0.5 mΩ, showing extremely excellent characteristics.

[0086] [Examples 4 and 5] The circuit breaker in Example 4 is the same as in Example 1, but with a diameter of 0.5 mm and a welded portion 30 of the annular weld line 31X shown in Figure 13. The circuit breaker in Example 5 is the same as in Example 1 except that the welded portion 30 of the annular weld line 31X has a minor diameter of 0.3 mm and a major diameter of 0.7 mm, as shown in Figure 14. The on-resistance before activation treatment is 6.9 mΩ, and the contact resistance after activation treatment is 4.1 mΩ. Furthermore, when a contact current of 12 A is passed through the contacts with a resistive load, the increase in contact resistance of the contacts after 20,000 on / off cycles is less than 0.7 mΩ, demonstrating extremely excellent characteristics.

[0087] [Example 6] The circuit breaker of Example 6 is the same as in Example 1, except that the welding spots 32 are arranged at 0.5 mm intervals at the vertices of a square as shown in Figure 20. The circuit breaker of Example 6 has an on-resistance of 7.2 mΩ without activation treatment and a contact resistance of 4.3 mΩ after activation treatment. Furthermore, when a contact current of 12 A is passed through the contacts with a resistive load, it is switched on and off 20,000 times and the increase in the contact resistance of the contacts is less than 0.7 mΩ, showing extremely excellent characteristics.

[0088] [Examples 7 and 8] Furthermore, the circuit breakers of Examples 7 and 8, which are the same as those of Example 1 except that the welding spots 32 are arranged at 0.5 mm intervals as shown in Figures 18 and 19, exhibit extremely excellent characteristics. The on-resistance is 7.3 mΩ before activation, and the contact resistance is 4.5 mΩ after activation. Moreover, when a contact current of 12 A is passed through the contacts under a resistive load, the increase in contact resistance of the contacts after 20,000 on / off cycles is less than 0.9 mΩ.

[0089] [Example 9] The circuit breaker of Example 9, which is the same as that of Example 1 but uses phosphor bronze for the elastic arm plate 6, exhibits extremely excellent characteristics: an on-resistance of 15.1 mΩ or less without activation treatment, a contact resistance of 10.2 mΩ or less after activation treatment, and an increase in contact resistance of 0.5 mΩ or less after 20,000 on / off cycles with a resistive load and a contact current of 10 A.

[0090] [Examples 10-11] The circuit breaker in Example 10, which is the same as in Example 1, but uses an elastic metal plate ("QMET 300 registered trademark of MATERION PERFORMANCE ALLOYS AND COMPOSITES USA") made of a copper alloy with a total content of Cr, Ag, and Si of 0.5 to 3% by weight for the elastic arm plate 6, and the circuit breaker in Example 11, which uses an elastic metal plate made of a copper alloy containing Ni, P, Zn, and Fe, exhibit extremely excellent characteristics. The on-resistances in the unactivated state are 6.8 mΩ or less and 8.1 mΩ or less, respectively, and the contact resistances after activation are 3.9 mΩ or less and 5.5 mΩ or less. Furthermore, when a contact current of 12 A is passed through the contacts under a resistive load and the circuit is switched on and off 20,000 times, the increase in contact resistance of the contacts is 0.5 mΩ or less.

[0091] [Examples 12-14] The breaker of Example 12 is the same as that of Example 1, but the material of the elastic arm plate 6 is a copper alloy containing 83% IACS with Cr and Mg, The breaker of Example 13 is a copper alloy containing 93% IACS with Zr, The circuit breaker in Example 14, which uses a copper alloy containing 90% Sn-containing IACS, exhibited on-resistances of 6.5 mΩ, 5.5 mΩ, and 5.8 mΩ respectively before activation, and contact resistances of 3.5 mΩ, 3.1 mΩ, and 3.2 mΩ after activation. Furthermore, after 20,000 on / off cycles with a resistive load and a contact current of 12 A, the increase in contact resistance was less than 0.5 mΩ, demonstrating extremely excellent characteristics. [Industrial applicability]

[0092] This invention can be suitably used as a circuit breaker where stabilization of the contact state of the contacts is required, by laser welding together an elastic arm plate and a terminal plate as separate metal plates. [Explanation of Symbols]

[0093] 100... Circuit breaker 1…Outer case 1A…Main unit case 1B... Lid case 3...Terminal board 3A…Exposed part 3B…middle part 3X…Connection terminal 4…Fixed contact metal plate 4A…Tip 4B...Middle section 4D…Step part 4X…Connection terminals 5…Fixed contact 6…Elastic arm plate 6A…Movable parts 6B…Rear end 6C…Protrusion 7…Movable contact 8…Bimetal 9… Heater 10...Outer wall 11…Exterior walls 11A...First exterior wall 11B...Second outer wall 12… Opposing wall 13...Bottom 14…Wide section 15…Bottom plate 15A…Opening 16…Matching protrusion 17…Connecting protrusion 18…Connecting recess 19...Protruding part 20...Storage space 21…recess 22...Outer wall 23...Storage section 24... Stepped recess 25...Pressure protrusion 26...Deformation-restricting protrusions 29…Storage recess 30... Welded part 31... Welding line 31A...Vertical welding line section 31B... Horizontal welding line section 31C, 31D... Curved line section 31E... Inclined line section 31X...Annular welding line 31Y...Wavy welding line 32... Welding spot 35…Inlay material 37…Silver plating layer 40…Laminated section 44...Exposed terminal 50… Laser beam 51... Pusher 52…Base plate 53…Support ribs 60... Circuit board 61...Solder side

Claims

1. A metal plate with a fixed contact, An elastic arm plate having a movable contact at its tip located opposite the fixed contact, A terminal plate connected to the aforementioned elastic arm plate, An outer casing comprising the terminal board and the fixed contact metal plate fixed together, A circuit breaker comprising a bimetal, which is housed in the outer casing and presses the elastic arm plate to separate the movable contact from the fixed contact and switch it to the off state, The elastic arm plate is In the non-compressed state of the aforementioned bimetal, due to its own elasticity, The movable contact has elasticity to press against the fixed contact and hold it in the ON state, The elastic arm plate and the terminal plate are stacked, The laminated sections are connected via laser-welded welds. The aforementioned welded joint is It is a microbreaker that includes a linearly extending welding line, A breaker in which the outer casing covers the upper part of the elastic arm plate without having through holes in the laminated portion.

2. The circuit breaker according to Claim 1, The aforementioned outer case has a main body case and a lid case. The aforementioned lid case, It is connected to the opening side of the main body case and closes the opening, A breaker in which the cover case covers the upper part of the elastic arm plate without having through holes in the laminated portion.

3. A circuit breaker according to claim 2, The lid case is a breaker provided with a fitting projection on the upper surface of the laminated portion of the elastic arm plate.

4. A metal plate with a fixed contact, An elastic arm plate having a movable contact at its tip located opposite the fixed contact, A terminal plate connected to the aforementioned elastic arm plate, An outer casing comprising the terminal board and the fixed contact metal plate fixed together, A circuit breaker comprising a bimetal, which is housed in the outer casing and presses the elastic arm plate to separate the movable contact from the fixed contact and switch it to the off state, The elastic arm plate is In the non-compressed state of the aforementioned bimetal, due to its own elasticity, The movable contact has elasticity to press against the fixed contact and hold it in the ON state, The elastic arm plate and the terminal plate are stacked, The laminated sections are connected via laser-welded welds. The surface of the elastic arm plate is pressed, The elastic arm plate and the terminal plate are in close contact with each other without any gaps, and a laser beam is irradiated onto them. The aforementioned welded joint is A breaker characterized by being a microbreaker that includes a linearly extending welding line.

5. A circuit breaker according to claim 1, The aforementioned welding line A breaker characterized by having a longitudinal welding line portion extending in the longitudinal direction of the elastic arm plate.

6. The circuit breaker according to claim 5, The aforementioned welded portion Having multiple rows of the aforementioned vertical welding lines, Multiple rows of the aforementioned vertical welding line section, A circuit breaker characterized by having elastic arm plates arranged at a distance from each other in the width direction.

7. A circuit breaker according to claim 1, The aforementioned welding line A breaker characterized by having a transverse welding line portion extending in the width direction of the elastic arm plate.

8. The circuit breaker according to claim 7, The aforementioned welded portion Having multiple rows of the aforementioned horizontal welding lines, The multiple rows of the aforementioned horizontal welding lines, A breaker characterized in that the elastic arm plates are arranged at a distance from each other in the longitudinal direction.

9. A circuit breaker according to any one of claims 1 to 4, The aforementioned welded portion The longitudinal welding line portion extending in the longitudinal direction of the elastic arm plate, A breaker characterized by having a transverse welding line portion extending in the width direction of the elastic arm plate.

10. A circuit breaker according to any one of claims 1 to 4, A breaker characterized in that the welding line has a corrugated welding line.

11. A circuit breaker according to any one of claims 1 to 4, The aforementioned welding line A breaker characterized by having an annular welding line that extends along the annular shape.

12. The circuit breaker according to claim 11, The aforementioned annular welding line A circuit breaker characterized by being circular or oval in shape.

13. The circuit breaker according to claim 11, A breaker characterized in that the aforementioned annular welding line is rectangular.

14. A circuit breaker according to any one of claims 1 to 4, The aforementioned welded joint is A breaker that includes both linearly extending welding lines and welding spots.

15. A fixed contact metal plate having a fixed contact, An elastic arm plate having a movable contact at its tip located opposite the fixed contact, A terminal plate connected to the aforementioned elastic arm plate, An outer casing comprising the terminal board and the fixed contact metal plate fixed together, A circuit breaker comprising a bimetal, which is housed in the outer casing and presses the elastic arm plate to separate the movable contact from the fixed contact and switch it to the off state, The elastic arm plate is In the non-compressed state of the aforementioned bimetal, due to its own elasticity, The movable contact has elasticity to press against the fixed contact and hold it in the ON state, The elastic arm plate and the terminal plate are stacked, The laminated sections are connected via laser-welded welds. The welded portion has multiple welding spots, Multiple of the aforementioned welding spots, The elastic arm plates are arranged to be separated in the longitudinal direction, A breaker in which the outer casing covers the upper part of the elastic arm plate without having through holes in the laminated portion.

16. A fixed contact metal plate having a fixed contact, An elastic arm plate having a movable contact at its tip located opposite the fixed contact, A terminal plate connected to the aforementioned elastic arm plate, An outer casing comprising the terminal board and the fixed contact metal plate fixed together, A circuit breaker comprising a bimetal, which is housed in the outer casing and presses the elastic arm plate to separate the movable contact from the fixed contact and switch it to the off state, The elastic arm plate is In the non-compressed state of the aforementioned bimetal, due to its own elasticity, The movable contact has elasticity to press against the fixed contact and hold it in the ON state, The elastic arm plate and the terminal plate are stacked, The laminated sections are connected via laser-welded welds. The welded portion has multiple welding spots, Multiple of the aforementioned welding spots, The elastic arm plates are arranged to be spaced apart in the width direction, A breaker in which the outer casing covers the upper part of the elastic arm plate without having through holes in the laminated portion.

17. A fixed contact metal plate having a fixed contact, An elastic arm plate having a movable contact at its tip located opposite the fixed contact, A terminal plate connected to the aforementioned elastic arm plate, An outer casing comprising the terminal board and the fixed contact metal plate fixed together, A circuit breaker comprising a bimetal, which is housed in the outer casing and presses the elastic arm plate to separate the movable contact from the fixed contact and switch it to the off state, The elastic arm plate is In the non-compressed state of the aforementioned bimetal, due to its own elasticity, The movable contact has elasticity to press against the fixed contact and hold it in the ON state, The elastic arm plate and the terminal plate are stacked, The laminated sections are connected via laser-welded welds. The welded portion has multiple welding spots, Multiple of the aforementioned welding spots, The elastic arm plate is arranged to be separated in the longitudinal and width directions, A breaker in which the outer casing covers the upper part of the elastic arm plate without having through holes in the laminated portion.

18. A circuit breaker according to any one of claims 1 to 17, The fixed contact and the movable contact, A circuit breaker characterized by having activated contacts that have been activated by ultrasonic vibrations while energized.

19. A circuit breaker according to any one of claims 1 to 18, The elastic arm plate A circuit breaker characterized by having a metal plate that is thinner than the terminal plate.

20. A circuit breaker according to any one of claims 1 to 19, The thickness of the elastic arm plate is set to be 50 μm or more and 200 μm or less. A circuit breaker characterized by being a microcircuit breaker.

21. A circuit breaker according to any one of claims 1 to 20, The aforementioned outer casing is The outer periphery wall is formed by embedding the fixed contact metal plate and the terminal plate, The inside of the outer peripheral wall is used as a storage space for arranging the elastic arm plate, An exposed portion is provided within the storage space, where the surface of the terminal board is exposed. The terminal plate is formed by laminating and welding the elastic arm plate to the exposed portion. The aforementioned outer wall is A recess is provided on the storage space side to increase the exposed area of ​​the exposed portion, In the exposed portion of the terminal board, A breaker characterized in that the elastic arm plates are stacked and laser-welded together.

22. A circuit breaker according to any one of claims 1 to 21, The elastic arm plate, A circuit breaker characterized by being made of a Cu-Cr-Ag-Si alloy.

23. A circuit breaker according to any one of claims 1 to 21, The elastic arm plate, A circuit breaker characterized by being an elastic metal plate of a copper alloy containing Ni, P, Zn, and Fe.

24. A circuit breaker according to any one of claims 1 to 21, The elastic arm plate, A circuit breaker characterized by being an elastic metal plate of a copper alloy containing Fe, P, and Zn.

25. A circuit breaker according to any one of claims 1 to 21, The elastic arm plate, A breaker characterized by being an elastic metal plate of a copper alloy containing 75% to 95% IACS, which contains Cr and Mg.

26. A circuit breaker according to any one of claims 1 to 21, The elastic arm plate, A circuit breaker characterized by being an elastic metal plate of a copper alloy having 80% to 95% Zr-containing IACS.

27. A circuit breaker according to any one of claims 1 to 21, The elastic arm plate, A circuit breaker characterized by being an elastic metal plate of a copper alloy having 80% to 95% IACS containing Sn.

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