JP7645783B2 - Breakers, safety circuits and secondary battery packs - Google Patents

Description

The present invention relates to small breakers and the like that are built into electrical equipment, etc.

Conventionally, breakers have been used as protective devices (safety circuits) for secondary batteries, motors, heaters, and other electrical equipment (see, for example, Patent Document 1).

WO2011/105175 publication

The above-mentioned Patent Document 1 discloses a breaker in which a cover member is ultrasonically welded to a case body that houses a thermally responsive element and a movable piece.

However, the movable piece is handled as a single unit in the pre-processing step where it is housed in the case body, so there is a risk that the elastic part will undergo plastic deformation due to inadvertent contact, etc. In addition, it is difficult to accurately position the movable piece relative to the case body, making it difficult to assemble the breaker so that the fixed contact and movable contact are in proper contact.

The present invention was devised in consideration of the above-mentioned circumstances, and its main objective is to provide a breaker that can be assembled so that the fixed contact and the movable contact are in proper contact while suppressing plastic deformation of the movable piece.

The present invention is a breaker that includes a fixed contact, a movable piece that is formed in a plate shape and has an elastic part that elastically deforms and a movable contact at one end of the elastic part, and presses the movable contact against the fixed contact to make contact with it, a thermally responsive element that deforms with a change in temperature to transition the movable piece from a conductive state in which the movable contact is in contact with the fixed contact to a cutoff state in which the movable contact is separated from the fixed contact, a first resin case in which a storage recess is formed to accommodate the fixed contact, the movable piece, and the thermally responsive element, and a second resin case that is integrated with the movable piece and is fixed to the first resin case to cover the storage recess, the second resin case having a fixing surface that is fixed to the first resin case, the elastic part protruding from the fixing surface toward the first resin case by a first protruding amount, and the second resin case having a protruding portion that protrudes from the fixing surface toward the first resin case by a second protruding amount that is greater than the first protruding amount.

In the breaker according to the present invention, it is desirable that the protrusions are provided on both sides of the movable contact in the short direction of the movable piece.

In the breaker according to the present invention, it is desirable that the first resin case is formed with a recess that fits into the protrusion.

In the breaker according to the present invention, it is desirable that the protrusion overlaps at least a portion of the one end when viewed from the short side direction of the movable piece.

In the breaker according to the present invention, it is desirable that at least a portion of the protrusion is formed outside one end of the elastic portion in the longitudinal direction of the movable piece.

The present invention is a safety circuit for electrical equipment that includes the above-mentioned breaker.

The present invention is a secondary battery pack equipped with the above-mentioned breaker.

In the breaker of the present invention, the movable piece is integrated with the second resin case, which reduces the risk of the elastic part undergoing plastic deformation in the process prior to being housed in the first resin case. In addition, the second resin case is formed with a protruding part that protrudes from the surface where the second resin case is fixed to the first resin case by a second protruding amount that is greater than the first protruding amount of the elastic part, so that the protruding part guards the elastic part and further reduces plastic deformation. In addition, the protruding part prevents contact between the elastic part and the first resin case in the initial stage of assembling the second resin case to the first resin case, which makes it possible to assemble the case so that the fixed contact and the movable contact are in proper contact.

FIG. 2 is a perspective view of a breaker manufactured according to the present invention in an unassembled state; FIG. 2 is a cross-sectional view showing the breaker in a normal charging or discharging state. 4 is a cross-sectional view showing the breaker in an overcharged state or during an abnormality. FIG. FIG. 4 is a perspective view showing a lid member in which a movable piece and a cover piece are embedded. FIG. 4 is a perspective view showing a case body in which a fixing piece is embedded. FIG. 4 is a cross-sectional view of a lid member in which a movable piece and a cover piece are embedded. FIG. 2 is a plan view showing the configuration of a secondary battery pack including the breaker of the present invention. FIG. 2 is a circuit diagram of a safety circuit including the breaker of the present invention.

A breaker according to one embodiment of the present invention will be described with reference to the drawings. Figs. 1 to 3 show the configuration of a breaker 1 manufactured according to the present invention. The breaker 1 is mounted on an electrical device, a secondary battery pack, etc., and protects the electrical device, the secondary battery pack, etc. from excessive temperature rise or overcurrent.

The breaker 1 is composed of a fixed piece 2 with a fixed contact 21, a movable piece 4 with a movable contact 41 at one end, a thermally responsive element 5 that deforms with temperature changes, a PTC (Positive Temperature Coefficient) thermistor 6, and a resin case 10 that houses the fixed piece 2, the movable piece 4, the thermally responsive element 5, and the PTC thermistor 6. The resin case 10 is composed of a case body (first resin case) 7, a cover member (second resin case) 8 that is attached to the top surface of the case body 7, and the like.

The fixed piece 2 is formed by pressing a metal plate whose main component is copper or the like (other metal plates include copper-titanium alloy, nickel silver, brass, etc.), and is embedded in the case body 7 by insert molding. One end of the fixed piece 2 is formed with a terminal 22 that is electrically connected to an external circuit, and the other end is formed with a support part 23 that supports the PTC thermistor 6. The terminal 22 protrudes to the outside of the case body 7. The PTC thermistor 6 is placed on and supported by convex projections (dowels) 24 formed in three places on the support part 23 of the fixed piece 2. By bending the fixed piece 2 in a stepped shape, the fixed contacts 21 and the support parts 23 are arranged in a stepped manner, and a space for storing the PTC thermistor 6 is easily secured.

The fixed contact 21 is formed at a position opposite the movable contact 41 by cladding, plating, welding, or coating with a highly conductive material such as silver, nickel, nickel-silver alloy, copper-silver alloy, gold-silver alloy, etc., and is exposed from a part of the opening 73a formed inside the case body 7. The terminal 22 protrudes outward from the edge of the case body 7. The support part 23 is exposed from an opening 73d formed inside the case body 7.

In this application, unless otherwise specified, the surface of the fixed piece 2 on which the fixed contact 21 is formed (i.e., the upper surface in FIG. 1) is described as the first surface, and the opposite surface is described as the second surface. The same applies to other components, such as the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, the resin case 10, etc.

The movable piece 4 is formed into an arm shape symmetrical about the center line in the longitudinal direction by pressing a plate-shaped metal material whose main component is copper or the like. A part of the movable piece 4 (fixed part 43 described later) is embedded in the cover member 8 by insert molding and is integrated with the cover member 8.

A movable contact 41 is formed at one end of the movable piece 4 in the longitudinal direction. The movable contact 41 is formed, for example, from the same material as the fixed contact 21, and is joined to one end of the movable piece 4 by welding, cladding, crimping, or other techniques.

A terminal 42 is formed on the other end of the movable piece 4, which is electrically connected to an external circuit. The terminal 42 protrudes outward from the edge of the cover member 8. A fixed portion 43 is provided between the movable contact 41 and the terminal 42, and is embedded and fixed in the cover member 8. The fixed portion 43 is disposed on the side of the terminal 42.

The movable piece 4 has an elastic part 44 between the movable contact 41 and the fixed part 43. The elastic part 44 extends from the fixed part 43 towards the movable contact 41. The movable piece 4 is supported in a cantilever manner by the cover member 8 at the fixed part 43 on the base end side of the elastic part 44, and in this state, the elastic part 44 elastically deforms towards the first surface, so that the movable contact 41 formed at the tip of the elastic part 44 is pressed against the fixed contact 21 and comes into contact, allowing electricity to flow between the fixed piece 2 and the movable piece 4.

It is preferable that the movable piece 4 is curved or bent by pressing at the elastic portion 44. There is no particular limit to the degree of curvature or bending as long as it can accommodate the thermally responsive element 5, and it may be set appropriately taking into consideration the elastic force at the operating temperature and the return temperature, the pressing force of the contacts, and the like. In addition, a pair of protrusions (contact portions) 44a, 44b are formed on the second surface of the elastic portion 44, facing the thermally responsive element 5. The protrusions 44a, 44b come into contact with the thermally responsive element 5, and the deformation of the thermally responsive element 5 is transmitted to the elastic portion 44 via the protrusions 44a, 44b (see Figures 1, 2, and 3).

The thermally responsive element 5 is disposed between the movable piece 4 and the PTC thermistor 6. That is, the thermally responsive element 5 is placed on the first surface of the PTC thermistor 6 described later. The thermally responsive element 5 changes its shape in response to a change in temperature, thereby shifting the state of the movable piece 4 from a conductive state in which the movable contact 41 contacts the fixed contact 21 to a cut-off state in which the movable contact 41 is separated from the fixed contact 21. The thermally responsive element 5 is formed into a plate shape by laminating thin plate materials with different thermal expansion coefficients, and has an initial shape with a cross section curved in an arc shape. When the reversal operating temperature is reached due to overheating, the curved shape of the thermally responsive element 5 reverses with a snap motion, and returns to its original shape when it cools down below the normal rotation return temperature. The initial shape of the thermally responsive element 5 can be formed by pressing. As long as the elastic part 44 of the movable piece 4 is pushed up by the reverse warping deformation of the thermally responsive element 5 at the desired temperature and returns to its original shape by the elastic force of the elastic part 44, the material and shape of the thermally responsive element 5 are not particularly limited, but a rectangular shape is preferable from the standpoint of productivity and efficiency of reverse warping deformation.

The material for the thermally responsive element 5 is a laminate of two types of materials with different thermal expansion coefficients, such as nickel silver, brass, and stainless steel, which are used in combination according to the required conditions. For example, a material for the thermally responsive element 5 that can obtain a stable reverse operating temperature and normal rotation return temperature is preferably a combination of a copper-nickel-manganese alloy on the high expansion side and an iron-nickel alloy on the low expansion side. Furthermore, a more preferable material from the standpoint of chemical stability is a combination of an iron-nickel-chromium alloy on the high expansion side and an iron-nickel alloy on the low expansion side. Still further, a more preferable material from the standpoint of chemical stability and workability is a combination of an iron-nickel-chromium alloy on the high expansion side and an iron-nickel-cobalt alloy on the low expansion side.

When the movable piece 4 is in an interrupted state, the PTC thermistor 6 conducts electricity between the fixed piece 2 and the movable piece 4 through the thermally responsive element 5. The PTC thermistor 6 is disposed between the fixed piece 2 and the thermally responsive element 5. That is, the support part 23 of the fixed piece 2 is located directly below the thermally responsive element 5, sandwiching the PTC thermistor 6. When the electrical connection between the fixed piece 2 and the movable piece 4 is interrupted by the reverse warpage deformation of the thermally responsive element 5, the current flowing through the PTC thermistor 6 increases. The PTC thermistor 6 can be selected according to the operating current, operating voltage, operating temperature, return temperature, and other requirements as long as it is a positive characteristic thermistor that increases in resistance with increasing temperature to limit the current, and the material and shape are not particularly limited as long as these various characteristics are not impaired. In this embodiment, a ceramic sintered body containing barium titanate, strontium titanate, or calcium titanate is used. In addition to ceramic sintered bodies, so-called polymer PTCs, which are polymers containing conductive particles such as carbon, may also be used.

The case body 7 and the cover member 8 that constitute the resin case 10 are molded from thermoplastic resins such as flame-retardant polyamide, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), and polybutylene terephthalate (PBT), which have excellent heat resistance. Materials other than resins may be used as long as they have properties equal to or better than those of the above-mentioned resins.

A storage recess 73 is formed on the first surface side of the case body 7, which is an internal space for accommodating the fixed contact 21, the movable piece 4, the thermally responsive element 5, and the PTC thermistor 6. The storage recess 73 has an opening 73a for accommodating the fixed contact 21 and the movable piece 4, an opening 73c for accommodating the movable piece 4 and the thermally responsive element 5, and an opening 73d for accommodating the PTC thermistor 6. The edges of the movable piece 4 and the thermally responsive element 5 incorporated in the case body 7 are abutted by the frame that constitutes the storage recess 73, and are guided when the thermally responsive element 5 undergoes reverse warping deformation. In other words, the storage recess 73 accommodates the movable piece 4 and the thermally responsive element 5 in a deformable manner.

The lid member 8 is configured to cover the storage recess 73. The lid member 8 may be configured to cover at least a portion of the storage recess 73. A cover piece 9 made of a metal plate mainly composed of copper or stainless steel is embedded in the lid member 8 by insert molding. The cover piece 9 is embedded in the lid member 8 together with the fixed portion 43 of the movable piece 4 in a state of contact with the first surface of the fixed portion 43. The cover piece 9 restricts the movement of the movable piece 4, and contributes to the miniaturization of the breaker 1 while increasing the rigidity and strength of the lid member 8 and thus the resin case 10 as the housing.

The case body 7 and the cover member 8 are formed by injection molding using the above-mentioned resin material. As already mentioned, the fixed piece 2 is inserted into the case body 7, and the movable piece 4 and the cover piece 9 are inserted into the cover member 8.

As shown in FIG. 1, the lid member 8 is attached to the case body 7 so as to close the openings 73a, 73c, etc. of the case body 7 that houses the fixed piece 2, the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, etc. The lid member 8 covers the housing recess 73. The case body 7 and the lid member 8 are joined by, for example, ultrasonic welding. In this way, the resin case 10 is formed.

Figures 2 and 3 show an outline of the operation of the breaker 1. Figure 2 shows the operation of the breaker 1 in a normal charging or discharging state. In a normal charging or discharging state, the thermally responsive element 5 maintains its initial shape before reverse bending. The movable contact 41 is pressed toward the fixed contact 21 by the elastic part 44, so that the movable contact 41 and the fixed contact 21 come into contact with each other, and the fixed piece 2 and the movable piece 4 of the breaker 1 are brought into a state in which they can be electrically connected via the elastic part 44 of the movable piece 4.

The elastic portion 44 of the movable piece 4 and the thermally responsive element 5 may be in contact. In this case, the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, and the fixed piece 2 are conductive as a circuit. However, since the resistance of the PTC thermistor 6 is overwhelmingly greater than the resistance of the movable piece 4, the current flowing through the PTC thermistor 6 is substantially negligible compared to the amount flowing through the fixed contact 21 and the movable contact 41.

Figure 3 shows the operation of the breaker 1 in an overcharged state or an abnormality. The thermally responsive element 5, which is a laminate of thin plates with different thermal expansion coefficients, deforms as the temperature rises so that the curved initial shape shown in Figure 2 is corrected. Then, when the thermally responsive element 5 reaches the operating temperature, it snaps into a reverse warped shape as shown in Figure 3. As a result, the thermally responsive element 5 comes into contact with the elastic part 44 of the movable piece 4, and the elastic part 44 is pushed up by the thermally responsive element 5, separating the fixed contact 21 and the movable contact 41. At this time, the current flowing between the fixed contact 21 and the movable contact 41 is cut off. Meanwhile, the thermally responsive element 5 comes into contact with the movable piece 4, and a small leakage current flows through the thermally responsive element 5 and the PTC thermistor 6. In other words, the PTC thermistor 6 conducts electricity between the fixed piece 2 and the movable piece 4 through the thermally responsive element 5, which is causing the movable piece 4 to transition to an interrupted state. The PTC thermistor 6 continues to generate heat as long as this leakage current flows, and the resistance value increases dramatically while maintaining the thermally responsive element 5 in a reverse warped state, so that the current does not flow through the path between the fixed contact 21 and the movable contact 41, and only the small leakage current mentioned above exists (forming a self-holding circuit). This leakage current can be used for other functions of the safety device.

When the overcharged state is released or the abnormal state is eliminated, the heat generated by the PTC thermistor 6 also stops, the thermally responsive element 5 returns to its normal rotation return temperature, and it returns to its original initial shape. Then, the elastic force of the elastic portion 44 of the movable piece 4 brings the movable contact 41 and the fixed contact 21 back into contact, the circuit is released from the interrupted state, and it returns to the conductive state shown in Figure 2.

Figure 4 shows the lid member 8 in which the movable piece 4 and the cover piece 9 are embedded. The movable piece 4 has a terminal 42 and a fixed portion 43. The fixed portion 43 is formed between the elastic portion 44 and the terminal 42. The fixed portion 43 is embedded in the resin that constitutes the lid member 8 together with the cover piece 9, and is fixed to the lid member 8. This integrates the movable piece 4, the cover piece 9, and the lid member 8. In this embodiment, the fixed portion 43 is in contact with the cover piece 9. This stabilizes the position of the movable piece 4 relative to the lid member 8. In addition, because the movable piece 4 is integrated with the lid member 8, the risk of plastic deformation of the elastic portion in the process prior to being housed in the case body 7 is reduced.

The cover member 8 has an embedded portion 81 in which the fixed portion 43 of the movable piece 4 is embedded, a fixing surface 82 that is fixed to the case body 7, and a storage recess 83 that is recessed on the opposite side of the case body 7.

The embedded portion 81 protrudes toward the case body 7 in order to embed the fixed portion 43. The embedded portion 81 embeds the fixed portion 43, so that the movable piece 4 is fixed at an accurate position relative to the cover member 8. The embedded portion 81 is formed to extend in the short direction D1 of the movable piece 4 along the edge of the cover member 8 on the terminal 42 side. In this embodiment, the embedded portion 81 extends to the edge of the cover member 8 in the short direction D1.

The fastening surface 82 is formed facing the case body 7. The tip surface of the embedded portion 81 constitutes a part of the fastening surface 82. It is preferable that the fastening surface 82 is formed in a flat shape, but as shown in FIG. 4, it may be formed in a partially inclined shape.

The accommodation recess 83 is recessed from the fixing surface 82 to accommodate the movable contact 41 and the elastic portion 44 of the movable piece 4. By forming the accommodation recess 83 in the cover member 8, the movable contact 41, the elastic portion 44, and the cover piece 9 are exposed to the internal space within the resin case 10.

Figure 5 shows the case body 7 in which the fixing piece 2 is embedded. The case body 7 has a welding portion 74 and a fixing surface 75.

The welded portion 74 is disposed in a position facing the embedded portion 81 when the cover member 8 is attached to the case body 7. The welded portion 74 is formed in a flat shape from the edge of the movable piece 4 in the longitudinal direction D2 of the case body 7 toward the storage recess 73. The welded portion 74 is welded to the embedded portion 81 and integrated with it.

When the lid member 8 is attached to the case body 7, the fixing surface 75 is disposed in a position and shape facing the fixing surface 82. The fixing surface 75 is welded to the fixing surface 82 and integrated with it. The fixing surface 75 and the fixing surface 82 may be formed with projections and recesses that fit into each other.

The fixed contact 21 is disposed in a receiving recess 73 that is recessed from the fixing surface 75. This reduces the height of the breaker 1.

Figure 6 shows a cross section parallel to the longitudinal direction D2 of the cover member 8 in which the movable piece 4 and the cover piece 9 are embedded.

The elastic portion 44 of the movable piece 4 protrudes from the fixed surface 82 toward the case body 7. More specifically, the movable contact 41 disposed at one end 44e of the elastic portion 44 protrudes from the fixed surface 82 around the elastic portion 44 by a first protrusion amount P1. This allows the fixed contact 21, which is recessed from the fixed surface 75, and the movable contact 41 to come into contact with each other with an appropriate pressure, reducing the contact pressure between them.

The cover member 8 has a protruding portion 84 that protrudes from the fixing surface 82 toward the case body 7. The protruding portion 84 protrudes from the fixing surface 82 around the elastic portion 44 toward the case body 7 by a second protruding amount P2 that is larger than the first protruding amount P1. In other words, the tip of the protruding portion 84 protrudes toward the case body 7 beyond the movable contact 41.

The elastic portion 44 protruding from the fixing surface 82 of the cover member 8 toward the case body 7 is likely to come into contact with some member (e.g., the case body 7) or a part of the breaker 1 assembly device during the process prior to being housed in the case body 7, and may be plastically deformed by the external force associated with such contact. For example, when the cover member 8 with the movable piece 4 embedded therein is wound into a coil as disclosed in Japanese Patent No. 3413167, the cover member 8 and the movable piece 4 that are adjacent in the radial direction may come into contact with each other, causing the elastic portion 44 to be plastically deformed.

However, in this breaker 1, the cover member 8 is formed with a protruding portion 84 that protrudes from the fixing surface 82 by a second protruding amount P2 that is larger than the first protruding amount P1 of the elastic portion 44, so that the elastic portion 44 is guarded by the protruding portion 84, and plastic deformation is further suppressed. In addition, the protruding portion 84 suppresses contact between the elastic portion 44 and the case body 7 in the initial stage of assembling the cover member 8 to the case body 7, so that the fixed contact 21 and the movable contact 41 can be assembled so as to be in proper contact.

It is preferable that the protrusions 84 are provided on both sides of the movable contact 41 in the short direction D1 of the movable piece 4. With this configuration, contact between the elastic part 44 and the case body 7, etc. is further suppressed, and plastic deformation of the elastic part 44 is further suppressed.

As shown in FIG. 5, it is preferable that a recess 76 is formed in the case body 7. The recess 76 is recessed from the fixing surface 75 at a position corresponding to the protrusion 84. More specifically, the recess 76 is provided on both sides of the fixed contact 21 in the short direction D1. When the cover member 8 is attached to the case body 7, the protrusion 84 fits into the recess 76. This allows the cover member 8 to be accurately positioned relative to the case body 7.

As shown in FIG. 6, it is desirable that the protrusion 84 overlaps at least a portion of one end 44e of the elastic part 44 in a side view seen from the short direction D1 of the movable piece 4. Such a protrusion 84 provides even more effective protection for the elastic part 44.

Furthermore, it is preferable that at least a portion of the protrusion 84 is formed further outward in the longitudinal direction D2 of the movable piece 4 than one end 44e of the elastic part 44. Such a protrusion 84 provides even more effective protection for the elastic part 44.

The breaker 1 of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment described above and can be modified and implemented in various forms.

That is, the breaker 1 of the present invention comprises at least a fixed contact 21, a movable piece 4 formed in a plate shape and having an elastically deformable elastic portion 44 and a movable contact 41 at one end 44e of the elastic portion 44, and pressing the movable contact 41 into contact with the fixed contact 21, a thermally responsive element 5 that deforms in response to a change in temperature to transition the movable piece 4 from a conductive state in which the movable contact 41 is in contact with the fixed contact 21 to a cutoff state in which the movable contact 41 is separated from the fixed contact 21, and a thermally responsive element 5 that deforms in response to a change in temperature to transition the movable piece 4 from a conductive state in which the movable contact 41 is in contact with the fixed contact 21 to a cutoff state in which the movable contact 41 is separated from the fixed contact 21. A breaker 1 includes a case body 7 having a storage recess 73 for storing an element 5, and a lid member 8 that is integrated with a movable piece 4 and is fixed to the case body 7 to cover the storage recess 73. The lid member 8 has a fixing surface 82 that is fixed to the case body 7, the elastic portion 44 protrudes from the fixing surface 82 toward the case body 7 by a first protrusion amount P1, and the lid member 8 has a protrusion 84 that protrudes from the fixing surface 82 toward the case body 7 by a second protrusion amount P2 that is greater than the first protrusion amount P1.

For example, the movable piece 4 may be made of a laminated metal such as a bimetal or trimetal, so that the movable piece 4 and the thermally responsive element 5 are integrally formed. In this case, the structure of the breaker 1 etc. is simplified.

In addition, in this embodiment, a self-holding circuit using a PTC thermistor 6 is provided, but it is also applicable to a configuration in which this configuration is omitted.

The breaker 1 of the present invention can also be widely applied to secondary battery packs, safety circuits for electrical equipment, and the like. FIG. 7 shows a secondary battery pack 500. The secondary battery pack 500 includes a secondary battery 501 and a breaker 1 provided in the output circuit of the secondary battery 501. FIG. 8 shows a safety circuit 502 for electrical equipment. The safety circuit 502 includes a breaker 1 in series in the output circuit of the secondary battery 501. The secondary battery pack 500 or safety circuit 502 including the breaker 1 can provide a secondary battery pack 500 or safety circuit 502 that provides stable conduction even when used at extremely low temperatures.

1: Breaker 4: Movable piece 5: Thermally responsive element 6: PTC thermistor 7: Case body (first resin case)
8: Lid member (second resin case)
10: Resin case 21: Fixed contact 41: Movable contact 44: Elastic portion 44e: One end 73: Storage recess 75: Fixing surface 76: Recess 77: Second recess 81: Buried portion 82: Fixing surface 83: Storage recess 500: Secondary battery pack 501: Secondary battery 502: Safety circuit D1: Short side direction D2: Longitudinal direction P1: First protrusion amount P2: Second protrusion amount

Claims (6)

A fixed contact;
a movable piece having an elastic portion formed in a plate shape, the elastic portion being elastically deformable and a movable contact at one end of the elastic portion, the movable contact being pressed against the fixed contact to bring the movable contact into contact with the fixed contact;
a thermally responsive element that deforms in response to a change in temperature to transition the movable piece from a conductive state in which the movable contact is in contact with the fixed contact to a cut-off state in which the movable contact is separated from the fixed contact;
a first resin case having an accommodating recess formed therein for accommodating the fixed contact, the movable piece, and the thermally responsive element;
a second resin case that is integrated with the movable piece and is fixed to the first resin case to cover the accommodating recess,
the second resin case has a fastening surface to be fastened to the first resin case,
the elastic portion protrudes from the fastening surface toward the first resin case by a first protrusion amount,
the second resin case has a protruding portion that protrudes from the fastening surface toward the first resin case by a second protruding amount that is greater than the first protruding amount,
The protrusions are provided on both sides of the movable contact in a short direction of the movable piece.
breaker. A fixed contact;
a movable piece having an elastic portion formed in a plate shape, the elastic portion being elastically deformable and a movable contact at one end of the elastic portion, the movable contact being pressed against the fixed contact to bring the movable contact into contact with the fixed contact;
a thermally responsive element that deforms in response to a change in temperature to transition the movable piece from a conductive state in which the movable contact is in contact with the fixed contact to a cut-off state in which the movable contact is separated from the fixed contact;
a first resin case having an accommodating recess formed therein for accommodating the fixed contact, the movable piece, and the thermally responsive element;
a second resin case that is integrated with the movable piece and is fixed to the first resin case to cover the accommodating recess,
the second resin case has a fastening surface to be fastened to the first resin case,
the elastic portion protrudes from the fastening surface toward the first resin case by a first protrusion amount,
the second resin case has a protruding portion that protrudes from the fastening surface toward the first resin case by a second protruding amount that is greater than the first protruding amount,
The protruding portion overlaps with the one end portion at least in part when viewed from a short side direction of the movable piece.
breaker. The breaker according to claim 1 or 2, wherein the first resin case has a recess formed therein that fits with the protrusion. 4. The breaker according to claim 1, wherein at least a part of said protruding portion is formed outside said one end portion of said elastic portion in the longitudinal direction of said movable piece . A safety circuit for an electrical device, comprising a circuit breaker according to any one of claims 1 to 4. A secondary battery pack comprising the breaker according to any one of claims 1 to 4.

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