Breaker, safety circuit, and secondary battery pack

Abstract

A breaker 1 comprises: a fixed piece 2 that has a fixed contact 21; a movable piece 4 that has an elastic section 43 and a movable contact 41 and that presses the movable contact 41 into contact with the fixed contact 21; a thermally-actuated element 5 that, by deforming in association with a change in temperature, shifts the movable piece 4 from a conduction state to a cut-off state; a PTC thermistor 6 that electrically connects the fixed piece 2 and the movable piece 4 via the thermally-actuated element 5; a case body 7 that has a first housing part 73; and a lid member 8 that is mounted to the case body 7. The lid member 8 communicates with the first housing part 73, has a second housing part for housing the thermally-actuated element 5 when deformed, and has a protrusion that protrudes from the inner top surface of the second housing part toward the thermally-actuated element 5.

Description

Breakers, safety circuits and secondary battery packs

[0001] The present invention relates to a small breaker or the like that is built into a secondary battery pack or the like of an electrical device.

[0002] 2. Description of the Related Art Conventionally, a breaker is known that includes a fixed contact, a movable piece having a movable contact, a thermally responsive element, and a positive temperature coefficient thermistor (see, for example, Patent Document 1).

[0003] WO2011 / 105175 publication

[0004] In a breaker, a positive temperature coefficient thermistor is usually housed in a recess provided in a case.

[0005] However, when the electrical device is subjected to a large impact, such as being dropped, the positive temperature coefficient thermistor may jump out of the recess and deform the movable piece, causing the movable contact to separate from the fixed contact.

[0006] The present invention was devised in view of the above circumstances, and its main object is to provide a breaker that can suppress the movement of a positive temperature coefficient thermistor even when subjected to a large impact.

[0007] The present invention provides a breaker comprising: a fixed piece having a fixed contact; a movable piece formed in a plate shape and having an elastically deformable elastic portion and a movable contact at one end of the elastic portion, pressing the movable contact against the fixed contact to bring it into contact; a thermally responsive element that deforms in response to temperature changes, thereby transitioning 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 positive temperature coefficient thermistor that provides electrical conductivity between the fixed piece and the movable piece via the thermally responsive element when the movable piece is in the cut-off state; a first case having a first housing portion for housing the fixed contact, the movable piece, the thermally responsive element, and the positive temperature coefficient thermistor; and a second case attached to the first case for closing an opening of the first housing portion, wherein the second case has a second housing portion that communicates with the first housing portion and houses the thermally responsive element when deformed, and a protrusion that protrudes from the inner bottom surface of the second housing portion toward the thermally responsive element.

[0008] In the breaker of the present invention, the second case has a protrusion that protrudes from the inner bottom surface of the second accommodating section toward the thermally responsive element, so that even when the breaker receives a large impact, the protrusion abuts against the thermally responsive element, causing the second case to suppress the movement of the thermally responsive element, and ultimately suppressing the movement of the positive temperature coefficient thermistor.

[0009] 1 is a perspective view showing a state before assembly of a breaker according to an embodiment of the present invention; a cross-sectional view showing the breaker in a normal charging or discharging state; a cross-sectional view showing the breaker in an overcharged state or during an abnormality; a perspective view of the cover member of FIG. 1 as viewed from the bottom side; a bottom view of the cover member of FIG. 4; a cross-section of the cover member of FIG. 5 taken along line A-A; an enlarged cross-sectional view of one of the protrusions and its surroundings in FIG. 6; a perspective view of a modified example of the cover member of FIG. 4; a perspective view of a modified example of the cover member of FIG. 8; a perspective view of another modified example of the cover member of FIG. 4; a front view of a secondary battery pack equipped with the breaker etc. of FIG. 1; a circuit diagram of a safety circuit equipped with the breaker etc. of FIG. 1;

[0010] A circuit breaker according to an embodiment of the present invention will be described with reference to the drawings. Figures 1 to 3 show the configuration of a circuit breaker 1 according to the present invention. The circuit breaker 1 is mounted in an electrical device or the like and protects the electrical device from excessive temperature rise or overcurrent.

[0011] 1, the breaker 1 is composed of a fixed piece 2 having a fixed contact 21 and a terminal 22, a terminal piece 3 having a terminal 32, a movable piece 4 having a movable contact 41 at its tip, a thermally responsive element 5 that deforms with temperature changes, a PTC (Positive Temperature Coefficient) thermistor 6, and a case 10 that houses the fixed piece 2, terminal piece 3, movable piece 4, thermally responsive element 5, and PTC thermistor 6. The case 10 is composed of a case main body (first case) 7, a cover member (second case) 8 attached to the case main body 7, and the like.

[0012] The fixing piece 2 is formed, for example, 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.

[0013] The fixed contact 21 is formed by cladding, plating, or coating a highly conductive material such as silver, nickel, a nickel-silver alloy, a copper-silver alloy, or a gold-silver alloy. The fixed contact 21 is formed in a position facing the movable contact 41 of the fixed piece 2, and is exposed to the first housing portion 73 of the case body 7 from a part of a recess 73a formed inside the case body 7. The fixed contact 21 and the terminal 22 are arranged at different heights by a stepped bent portion (not shown) embedded in the case body 7.

[0014] 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 referred to as the top surface, and the opposite surface is referred to as the bottom surface. The same applies to other components, such as the terminal piece 3, the movable piece 4, the thermally responsive element 5, the case 10, the cover piece 9, etc.

[0015] The terminals 22 are exposed from the bottom wall of the case body 7 in a rectangular shape and are connected to lands on the circuit board by soldering or other methods. In this embodiment, a pair of terminals 22 are arranged side by side in the short side direction of the breaker 1.

[0016] As in the breaker disclosed in the above-mentioned Patent Document 1, the fixed piece 2 may be configured to protrude from the side wall of the case body 7.

[0017] 2, the fixed piece 2 has a stepped bent portion 25 bent in a stepped manner (crank-shaped in side view), and a support portion 26 that supports the PTC thermistor 6. The stepped bent portion 25 connects the fixed contact 21 and the support portion 26, and the fixed contact 21 and the support portion 26 are positioned at different heights. The PTC thermistor 6 is placed on and supported by convex protrusions (dowels) 26a formed in three locations on the support portion 26.

[0018] Like the fixed piece 2, the terminal piece 3 is formed by pressing a metal plate whose main component is copper or the like, and is embedded in the case body 7 by insert molding. The terminal piece 3 has a connection portion 31 that is connected to the movable piece 4, and a terminal 32. The connection portion 31 and the terminal 32 are arranged at different heights by a stepped bent portion (not shown) embedded in the case body 7.

[0019] The connection portion 31 is exposed to the first housing portion 73 of the case body 7 from a part of the recess 73b formed inside the case body 7, and is electrically connected to the movable piece 4. On the other hand, the terminal 32 is exposed in a rectangular shape from the bottom wall of the case body 7, and is connected to a land portion of the circuit board by a method such as soldering. In this embodiment, a pair of terminals 32 are arranged side by side in the short direction of the breaker 1.

[0020] The movable piece 4 is formed into a plate shape by pressing a metal material whose main component is copper, etc. The movable piece 4 is formed into an arm shape symmetrical with respect to the center line in the longitudinal direction.

[0021] As in the breaker disclosed in the above-mentioned Patent Document 1, the movable piece 4 may be formed integrally with the terminal piece 3. In this case, a terminal 32 is formed on a part of the movable piece 4 (on the side of a connection portion 42 described later), and the terminal 32 protrudes from the side wall of the case body 7.

[0022] A movable contact 41 is formed at one end of the movable piece 4. The movable contact 41 is formed on the bottom surface of the movable piece 4 using the same material as the fixed contact 21, and is joined to the tip of the movable piece 4 by welding, cladding, crimping, or other methods.

[0023] A connection portion 42 that is electrically connected to the connection portion 31 of the terminal piece 3 is formed at the other end of the movable piece 4. The top surface of the connection portion 31 of the terminal piece 3 and the bottom surface of the connection portion 42 of the movable piece 4 are fixed together by, for example, laser welding. Laser welding is a welding technique in which workpieces (corresponding to the terminal piece 3 and the movable piece 4 in this embodiment) are irradiated with laser light to locally melt and solidify the workpieces, thereby joining them together. Laser weld marks are formed on the surface of the workpiece irradiated with laser light, which have a form different from weld marks formed by other welding techniques (for example, resistance welding that utilizes Joule heat).

[0024] The movable piece 4 has an elastic portion 43 between the movable contact 41 and the connecting portion 42. The elastic portion 43 extends from the connecting portion 42 toward the movable contact 41. As a result, the connecting portion 42 is provided on the opposite side of the elastic portion 43 from the movable contact 41.

[0025] The movable piece 4 is fixed by being fixed to the connection part 31 of the terminal piece 3 at the connection part 42, and as the elastic part 43 elastically deforms, the movable contact 41 formed at the tip thereof is pressed against the fixed contact 21 and makes contact, thereby enabling electrical conduction between the fixed piece 2 and the movable piece 4. The movable piece 4 and the terminal piece 3 are electrically connected at the connection parts 31 and 42, so that electrical conduction between the fixed piece 2 and the terminal piece 3 is possible.

[0026] The movable piece 4 is curved or bent by press working at the elastic portion 43. There are no particular limitations on 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, etc. Also, a pair of protrusions (contact portions) 44a, 44b are formed on the bottom surface of the elastic portion 43 so as to face the thermally responsive element 5. The protrusions 44a, 44b contact the thermally responsive element 5, and deformation of the thermally responsive element 5 is transmitted to the elastic portion 43 via the protrusions 44a, 44b (see FIGS. 1 and 3).

[0027] The thermally responsive element 5 transitions from a conductive state in which the movable contact 41 contacts the fixed contact 21 to a disconnected state in which the movable contact 41 is separated from the fixed contact 21. The thermally responsive element 5 has an initial shape curved in an arc and is formed by laminating thin plates with different thermal expansion coefficients. When heated to an operating temperature, the curved shape of the thermally responsive element 5 reverses with a snap motion and returns to its original shape when cooled below the recovery temperature. The initial shape of the thermally responsive element 5 can be formed by press working. The material and shape of the thermally responsive element 5 are not particularly limited as long as the reverse bending action of the thermally responsive element 5 pushes up the elastic portion 43 of the movable piece 4 at the desired temperature and returns to its original shape by the elastic force of the elastic portion 43. However, a rectangular shape is preferable from the viewpoints of productivity and efficiency of the reverse bending action, and a rectangular shape close to a square is preferable to efficiently push up the elastic portion 43 while maintaining a small size. The material of the thermally responsive element 5 may be a laminate of two materials with different thermal expansion coefficients, for example, a copper-nickel-manganese alloy or a nickel-chromium-iron alloy on the high expansion side, and an iron-nickel alloy or various alloys such as nickel silver, brass, and stainless steel on the low expansion side, and these materials may be combined according to the required conditions.

[0028] The PTC thermistor 6 establishes electrical continuity between the fixed piece 2 and the movable piece 4 when the movable piece 4 is in an interrupted state. The PTC thermistor 6 is disposed between the support portion 26 of the fixed piece 2 and the thermally-activated element 5. That is, the support portion 26 is located directly below the thermally-activated element 5, sandwiching the PTC thermistor 6 therebetween. When the thermally-activated element 5 reversely bends, interrupting electrical continuity between the fixed piece 2 and the movable piece 4, the current flowing through the PTC thermistor 6 increases. The PTC thermistor 6 can be selected based on the operating current, operating voltage, operating temperature, and recovery temperature, as long as it is a positive temperature coefficient thermistor that limits current by increasing its resistance with increasing temperature. The material and shape of the PTC thermistor 6 are not particularly limited as long as these characteristics are not impaired. In this embodiment, a ceramic sintered body containing barium titanate, strontium titanate, or calcium titanate is used. In addition to the ceramic sintered body, a so-called polymer PTC, in which conductive particles such as carbon are incorporated into a polymer, may also be used.

[0029] The case body 7 and the lid member 8 that constitute the case 10 are molded from a thermoplastic resin such as flame-retardant polyamide, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polybutylene terephthalate (PBT), or other thermoplastic resins that have excellent heat resistance. Materials other than resins may also be used as long as they have properties equivalent to or better than those of the above-mentioned resins.

[0030] A first housing section 73 is formed on the top surface of the case body 7, which is an internal space for housing the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, etc. The first housing section 73 is recessed from the joint surface 74 with the lid member 8 (the top surface of the case body 7) toward the top surface of the lid member 8. The first housing section 73 has recesses 73a and 73b for housing the movable piece 4, a recess 73c for housing the movable piece 4 and the thermally responsive element 5, and a recess 73d for housing 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 frames that constitute the first housing section 73, and are guided during reverse warpage deformation of the thermally responsive element 5.

[0031] A cover piece 9 is embedded in the lid member 8 by insert molding. The cover piece 9 is formed into a plate shape by pressing a metal such as the above-mentioned copper-based metal or a metal such as stainless steel. As shown in Figures 2 and 3 , the cover piece 9 abuts against the top surface of the movable piece 4 as appropriate to restrict the movement of the movable piece 4, and also contributes to the miniaturization of the breaker 1 while increasing the rigidity and strength of the lid member 8 and, by extension, the case 10 serving as the housing.

[0032] As shown in FIG. 1 , the cover member 8 is attached to the case body 7 so as to close recesses 73a, 73b, 73c, etc., of the case body 7, which houses the fixed piece 2, terminal piece 3, movable piece 4, thermally-activated element 5, PTC thermistor 6, etc. The case body 7 and the cover member 8 are joined together by, for example, ultrasonic welding. At this time, the case body 7 and the cover member 8 are continuously joined around the entire periphery of their respective outer edges, improving the airtightness of the case 10. This seals the internal space of the case 10 defined by the first housing portion 73, and protects the components, such as the movable piece 4, thermally-activated element 5, and PTC thermistor 6, from the atmosphere outside the case 10. In this embodiment, resin is entirely disposed on the top surface of the cover member 9, further enhancing the airtightness of the first housing portion 73.

[0033] FIG. 2 shows the operation of the breaker 1 under normal charging or discharging conditions. Under normal charging or discharging conditions, the thermally responsive element 5 maintains its initial shape (before reverse bending). The cover piece 9 has a protrusion 91 that abuts against the top 43a of the movable piece 4 and presses the top 43a toward the thermally responsive element 5. When the protrusion 91 presses the top 43a, the elastic portion 43 elastically deforms, and the movable contact 41 formed at its tip is pressed toward the fixed contact 21, bringing them into contact. This establishes electrical continuity between the fixed piece 2 and the terminal piece 3 of the breaker 1 through the elastic portion 43 of the movable piece 4. The elastic portion 43 of the movable piece 4 contacts the thermally responsive element 5, and the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, and the fixed piece 2 may be electrically connected 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 of current flowing through the fixed contact 21 and the movable contact 41.

[0034] FIG. 3 illustrates the operation of the breaker 1 during an overcharge or other abnormal condition. When a high temperature occurs due to overcharge or other abnormality, the thermally responsive element 5 reaches its operating temperature and bends backward, pushing up the elastic portion 43 of the movable piece 4 and separating the fixed contact 21 and the movable contact 41. The operating temperature of the thermally responsive element 5, when it deforms inside the breaker 1 and pushes up the movable piece 4, is, for example, 70°C to 90°C. At this time, the current flowing between the fixed contact 21 and the movable contact 41 is interrupted, and a small leakage current flows through the thermally responsive element 5 and the PTC thermistor 6. The PTC thermistor 6 continues to generate heat as long as this leakage current flows, maintaining the thermally responsive element 5 in a bent state and dramatically increasing its resistance. Therefore, current does not flow through the path between the fixed contact 21 and the movable contact 41, and only the small leakage current described above exists (forming a self-holding circuit). This leakage current can be used for other functions of the safety device.

[0035] FIG. 4 is a perspective view of the cover member 8 as viewed from the bottom side, and FIG. 5 is a bottom view of the cover member 8. As shown in FIG.

[0036] The cover member 8 has a second accommodating section 81 for accommodating the thermally responsive element 5 when deformed, and a protrusion 83 that protrudes from the inner top surface 82 of the second accommodating section 81 (the bottom surface of the cover piece 9) toward the thermally responsive element 5.

[0037] The second storage section 81 is recessed from the joint surface 84 with the case body 7 (the bottom surface of the lid member 8) toward the top surface of the lid member 8. The second storage section 81 communicates with the first storage section 73 of the case body 7.

[0038] The projection 83 of this embodiment projects from the cover piece 9 toward the thermally actuated element 5. The tip 83a of the projection 83 projects further toward the thermally actuated element 5 than the joining surface 84.

[0039] When the breaker 1 receives a large impact, the tip 83a of the protrusion 83 comes into contact with the top surface of the thermally responsive element 5. This allows the cover member 8 to suppress the movement of the thermally responsive element 5, which in turn suppresses the movement of the PTC thermistor 6. Therefore, even when the electrical equipment in which the breaker 1 is mounted receives a large impact, such as being dropped, the PTC thermistor 6 is prevented from jumping out of the first housing portion 73 and deforming the movable piece 4, causing the movable contact 41 to separate from the fixed contact 21.

[0040] When the movable piece 4 is in the conductive state or the cut-off state, it is desirable that the protrusion 83 does not come into contact with the thermally responsive element 5. When the movable piece 4 is "in the conductive state or the cut-off state," it is intended that the breaker 1 is in the state shown in Figures 2 and 3, i.e., in a normal operating state excluding when the electrical equipment has been subjected to a large impact such as being dropped. In such a normal operating state, the protrusion 83 does not come into contact with the thermally responsive element 5, thereby reducing the risk that the deformation of the thermally responsive element 5 will be hindered by the protrusion 83, and normal operation of the breaker 1 can be expected.

[0041] 4 and 5, the lid member 8 of this embodiment has a main body 85 made of resin or the like. The cover piece 9 is embedded in the main body 85. The cover piece 9 reinforces the main body 85.

[0042] The protrusion 83 in this embodiment is a portion of the main body 85 that protrudes toward the thermally responsive element 5. The protrusion 83 and the thermally responsive element 5 are directly opposed to each other. "Directly opposed" means that no other structure, such as the movable piece 4, is interposed between the protrusion 83 and the thermally responsive element 5. With this configuration, when the breaker 1 receives a large impact, the protrusion 83 and the thermally responsive element 5 come into direct contact with each other, further suppressing the movement of the thermally responsive element 5 and, in turn, the PTC thermistor 6.

[0043] 4 and 5, the cover piece 9 preferably has a through-hole 92 that penetrates the cover piece 9 in the thickness direction D3. Examples of the form of the through-hole 92 include a through-hole as shown in the figures, and a notch that is continuous with the edge of the cover piece 9.

[0044] The through-hole 92 is preferably formed in a region overlapping the protrusion 83 in a plan view seen from the thickness direction D3 of the cover piece 9. With this configuration, the main body 85 and the protrusion 83 are formed continuously through the through-hole 92. That is, when the cover piece 9 is inserted into a mold or the like for molding the lid member 8, the cavity space for molding the main body 85 and the cavity space for molding the protrusion 83 communicate through the through-hole 92. This makes it possible to mold the lid member 8 with high precision easily and in a short time. Furthermore, the strength of the protrusion 83 is improved, and damage to the protrusion 83 is suppressed even when the breaker 1 is subjected to a large impact.

[0045] It is desirable that the area S1 of the through portion 92 perpendicular to the thickness direction D3 is smaller than the cross-sectional area S2 perpendicular to the thickness direction D3 of the protrusion 83. With this configuration, it is possible to mold the protrusion 83 with high precision.

[0046] Figure 6 shows a cross section of the cover member 8 taken along line A-A (see Figure 5). As shown in Figures 5 and 6, the protrusion 83 is preferably disposed more inward than the edge 82a of the second housing portion 81 in the short-side direction D2 of the movable piece 4. The protrusion 83 is also preferably disposed more inward than the edge 73e of the first housing portion 73 in the short-side direction D2 of the movable piece 4. With this configuration, the risk of interference between the case body 7 and the protrusion 83 is reduced when the case body 7 and the cover member 8 are welded together, improving the welding accuracy between them.

[0047] It is desirable that a plurality of protrusions 83 are arranged along the short-side direction D2 of the movable piece 4. In this embodiment, a pair of protrusions 83 is provided along the short-side direction D2 at the center of the longitudinal direction D1 of the thermally responsive element 5. With this configuration, when the breaker 1 receives a large impact, the movement of the thermally responsive element 5 and therefore the PTC thermistor 6 is further suppressed.

[0048] Fig. 7 is an enlarged view of one of the protrusions 83 and its surroundings in Fig. 6. As already mentioned, the first housing portion 73 has a recess (third housing portion) 73d for housing the PTC thermistor 6 therein.

[0049] In this embodiment, it is desirable that the sum a+b of the first distance a from the protrusion 83 to the thermally responsive element 5 and the second distance b from the third housing portion 73d to the thermally responsive element 5 is equal to or less than the thickness c of the PTC thermistor 6. Here, the first distance a and the second distance b are measured when the breaker 1 is in a normal operating state and the thermally responsive element 5 is stationary.

[0050] With this configuration, even if the breaker 1 receives a large impact and the thermally responsive element 5 moves toward the cover member 8, the maximum distance from the third storage section 73d to the thermally responsive element 5 is less than the above sum a + b, thereby preventing the PTC thermistor 6 from detaching from the recess 73d.

[0051] The thickness c of the PTC thermistor 6 is measured as the total thickness of the PTC thermistor 6. This method of measuring the thickness c is effective when the entire PTC thermistor 6 has approximately the same thickness. The PTC thermistor 6 may also have its edges chamfered in a C-shape or an R-shape.

[0052] Furthermore, the thickness of the PTC thermistor 6 may decrease in multiple stages from the center toward the edges. Fig. 7 shows a PTC thermistor 6 having two thickness stages via a C-plane, with the thickness at the edges becoming thinner. In such a PTC thermistor 6, the sum a + b is preferably equal to or less than the thickness d of the edges of the PTC thermistor 6. This configuration prevents the edges of the PTC thermistor 6 from separating from the recess 73d, even if the breaker 1 receives a large impact and the thermally responsive element 5 moves toward the cover member 8.

[0053] Fig. 8 is a perspective view of a cover member 8A which is a modified example of the cover member 8 shown in Fig. 4 etc. The configuration of the cover member 8 described above can be adopted for parts of the cover member 8A that are not described below.

[0054] The lid member 8A differs from the lid member 8 in that the movable piece 4A is electrically connected to the cover piece 9. The movable piece 4A is connected to the cover piece 9 by welding at a connection portion 42.

[0055] A breaker that uses the cover member 8A is disclosed in, for example, Japanese Patent Application Laid-Open No. 2022-066783, and therefore, a description thereof will be omitted.

[0056] The protrusion 83 is disposed in a position facing the connecting portion 42 of the movable piece 4A and a part of the edge of the elastic portion 43. In the lid member 8A configured in this manner, when the movable piece 4A is placed on the bottom surface of the cover piece 9 for welding, the protrusion 83 protruding from the joining surface 84 functions to guide the movable piece 4A. This allows the movable piece 4A to be positioned easily and accurately.

[0057] In the cover member 8A, the protrusion 83 and the thermally responsive element 5 also directly face each other. With this configuration, similar to the cover member 8, when the breaker 1 receives a large impact, the protrusion 83 and the thermally responsive element 5 come into direct contact with each other, so that the movement of the thermally responsive element 5 and therefore the PTC thermistor 6 is further suppressed.

[0058] 8, it is desirable that the edge of the tip 83a of the protrusion 83 is rounded. The edge of the tip 83a of the protrusion 83 may be chamfered. With this configuration, the function of the protrusion 83 to guide the movable piece 4A is improved.

[0059] Fig. 9 is a perspective view of a cover member 8B which is a modified example of the cover member 8A shown in Fig. 8. The configuration of the cover member 8A described above can be adopted for parts of the cover member 8B that are not described below.

[0060] The cover member 8B differs from the cover member 8A in that the movable piece 4B is provided with a pair of movable contacts 41. Each movable contact 41 is provided at the tip of an elastic portion 43 provided on either side of the connection portion 42. A breaker employing the cover member 8B is disclosed in, for example, Japanese Patent Application Laid-Open No. 2021-150116, and therefore a description thereof will be omitted.

[0061] The cover member 8B is provided with two pairs of protrusions 83 due to the adoption of the configuration of the movable piece 4B described above. The protrusions 83 are arranged in positions facing the connecting portion 42 of the movable piece 4 and part of the edge of the elastic portion 43. Also in the cover member 8B, the protrusions 83 directly face the thermally responsive element 5. The edge of the tip portion 83a of the protrusions 83 is rounded or otherwise processed. The function and effect of the protrusions 83 are the same as those of the cover member 8A.

[0062] Fig. 10 is a perspective view of a cover member 8C, which is another modified example of the cover member 8 shown in Fig. 4 etc. The configuration of the cover member 8 etc. described above can be adopted for parts of the cover member 8C that are not described below.

[0063] The lid member 8C differs from the lid member 8 and the like in that it has a protrusion 93 that is a protrusion formed on a part of the cover piece 9, instead of the protrusion 83 that is a protrusion formed on a part of the main body 85. The protrusion 93 protrudes from the bottom surface of the cover piece 9 toward the thermally responsive element 5.

[0064] The protrusion 93 in this embodiment is formed by cutting and bending the cover piece 9 when the cover piece 9 is press-formed, for example.

[0065] The protrusion 93 may be formed by fastening a small piece prepared as a separate part to the bottom surface of the cover piece 9. In this case, the material of the protrusion is not limited to the same metal as the cover piece 9, but may be, for example, the same resin as the main body 85 of the lid member 8C.

[0066] In the cover member 8C, the protrusion 93 and the thermally responsive element 5 also directly face each other. With this configuration, similar to the cover member 8, when the breaker 1 receives a large impact, the protrusion 93 and the thermally responsive element 5 come into direct contact with each other, so that the movement of the thermally responsive element 5 and therefore the PTC thermistor 6 is further suppressed.

[0067] The breaker 1 and the like of the present invention can also be widely applied to secondary battery packs, safety circuits for electrical equipment, and the like. FIG. 11 shows a secondary battery pack 500. The secondary battery pack 500 includes a secondary battery 501 and a breaker 1 and the like provided in the output circuit of the secondary battery 501. FIG. 12 shows a safety circuit 502 for electrical equipment. The safety circuit 502 includes a breaker 1 and the like connected in series in the output circuit of the secondary battery 501. A part of the safety circuit 502 may be formed by a cable including a connector equipped with a breaker 1 and the like. By using a secondary battery pack 500 or a safety circuit 502 equipped with a breaker 1 and the like, it is possible to manufacture a secondary battery pack 500 or a safety circuit 502 that can continue to supply current to a load, etc., even when subjected to a large shock.

[0068] Although the breaker 1 and the like of the present invention have been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and implemented in various forms.

[0069] [Additional Notes] The present invention includes the following aspects.

[0070] [Invention 1] A breaker comprising: a fixed piece having a fixed contact; a movable piece formed in a plate shape and having an elastically deformable elastic portion and a movable contact at one end of the elastic portion, pressing the movable contact against the fixed contact to bring it into contact; a thermally responsive element that deforms in response to a change in temperature, thereby transitioning 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 positive temperature coefficient thermistor that provides electrical continuity between the fixed piece and the movable piece via the thermally responsive element when the movable piece is in the cut-off state; a first case having a first housing portion for housing the fixed contact, the movable piece, the thermally responsive element, and the positive temperature coefficient thermistor; and a second case attached to the first case for closing an opening of the first housing portion, wherein the second case is connected to the first housing portion and has a second housing portion for housing the thermally responsive element when it is deformed, and a protrusion protruding from an inner top surface of the second housing portion toward the thermally responsive element. [Invention 2] The breaker according to Invention 1, wherein the protrusion does not contact the thermally actuated element when the movable piece is in the conductive state or the cut-off state. [Invention 3] The breaker according to Invention 1, wherein the second case has a main body and a cover piece embedded in the main body to reinforce the main body, the protrusion is a portion of the main body that protrudes toward the thermally actuated element, and the protrusion and the thermally actuated element directly face each other. [Invention 4] The breaker according to Invention 3, wherein the cover piece has a through-hole penetrating through the thickness direction in a region that overlaps with the protrusion in a plan view seen from the thickness direction. [Invention 5] The breaker according to Invention 4, wherein the area perpendicular to the thickness direction of the through-hole is smaller than the cross-sectional area of ​​the protrusion perpendicular to the thickness direction. [Invention 6] The breaker according to Invention 3, wherein the movable piece is electrically connected to the cover piece. [Invention 7] The breaker according to Invention 3, wherein the tip of the protrusion is chamfered or rounded. [Invention 8] The breaker according to Invention 3, wherein the protrusion is arranged inward from an edge of the second housing portion in the lateral direction of the movable piece. [Invention 9] The breaker according to Invention 1, wherein a plurality of the protrusions are arranged along the lateral direction of the movable piece.[Invention 10] The breaker according to Invention 1, wherein the first housing has a third housing for housing the positive temperature coefficient thermistor, and the sum of the first distance from the protrusion to the thermally responsive element and the second distance from the third housing to the thermally responsive element is smaller than the thickness of the edge of the positive temperature coefficient thermistor. [Invention 11] The breaker according to Invention 1, wherein the second case has a main body and a cover piece embedded in the main body to reinforce the main body, the protrusion being a raised portion of the cover piece, and the protrusion and the thermally responsive element directly face each other. [Invention 12] The breaker according to Invention 1, wherein the second case has a main body and a cover piece embedded in the main body to reinforce the main body, the protrusion being a small piece fixed to the cover piece, and the protrusion and the thermally responsive element directly face each other. [Invention 13] A safety circuit for an electrical device, comprising a breaker according to any one of Inventions 1 to 12. [Invention 14] A secondary battery pack comprising the breaker according to any one of Inventions 1 to 12.

[0071] DESCRIPTION OF SYMBOLS 1: Breaker 2: Fixed piece 4: Movable piece 4A: Movable piece 4B: Movable piece 5: Thermally responsive element 6: Thermistor 7: Case body (first case) 8: Lid member (second case) 9: Cover piece 10: Case 21: Fixed contact 41: Movable contact 43: Elastic portion 73: First housing portion 73d: Third housing portion 73e: Edge 81: Second housing portion 82: Inner top surface 82a: Edge 83: Protrusion 83a: Tip portion 85: Main body portion 92: Penetration portion 93: Protrusion 500: Secondary battery pack 501: Secondary battery 502: Safety circuit D2: Short side direction D3: Thickness direction S1: Area S2: Cross-sectional area a : First distance b: Second distance c: Thickness

Claims

1. A fixing piece having a fixed contact point, A plate-shaped, elastically deformable elastic portion and a movable contact at one end of the elastic portion, the movable contact being pressed against and brought into contact with the fixed contact, A thermally responsive element that deforms in response to temperature changes, causing the movable piece to transition from a conductive state where the movable contact is in contact with the fixed contact to a disconnected state where the movable contact is separated from the fixed contact, When the movable piece is in the blocked state, a positive characteristic thermistor is used to conduct electricity between the fixed piece and the movable piece via the thermally responsive element, A first case having a first housing section for housing the fixed contact, the movable piece, the thermally responsive element, and the positive characteristic thermistor, A circuit breaker comprising a second case attached to the first case to close the opening of the first housing, The second case comprises a main body, a cover piece embedded in the main body to reinforce the main body, a second housing that communicates with the first housing and houses the thermal responsive element when deformed, and a projection that protrudes from the inner top surface of the second housing toward the thermal responsive element. The aforementioned projection is formed when a part of the main body protrudes toward the side of the thermal responsive element. The projection and the thermal responsive element are directly opposite each other. breaker.

2. A fixing piece having a fixed contact point, A plate-shaped, elastically deformable elastic portion and a movable contact at one end of the elastic portion, the movable contact being pressed against and brought into contact with the fixed contact, A thermally responsive element that deforms in response to temperature changes, causing the movable piece to transition from a conductive state where the movable contact is in contact with the fixed contact to a disconnected state where the movable contact is separated from the fixed contact, When the movable piece is in the blocked state, a positive characteristic thermistor is used to conduct electricity between the fixed piece and the movable piece via the thermally responsive element, A first case having a first housing section for housing the fixed contact, the movable piece, the thermally responsive element, and the positive characteristic thermistor, A circuit breaker comprising a second case attached to the first case to close the opening of the first housing, The second case comprises a main body, a cover piece embedded in the main body to reinforce the main body, a second housing that communicates with the first housing and houses the thermal responsive element when deformed, and a projection that protrudes from the inner top surface of the second housing toward the thermal responsive element. The aforementioned protrusion is a raised portion of the cover piece. The projection and the thermal responsive element are directly opposite each other. breaker.

3. A fixing piece having a fixed contact point, A plate-shaped, elastically deformable elastic portion and a movable contact at one end of the elastic portion, the movable contact being pressed against and brought into contact with the fixed contact, A thermally responsive element that deforms in response to temperature changes, causing the movable piece to transition from a conductive state where the movable contact is in contact with the fixed contact to a disconnected state where the movable contact is separated from the fixed contact, When the movable piece is in the blocked state, a positive characteristic thermistor is used to conduct electricity between the fixed piece and the movable piece via the thermally responsive element, A first case having a first housing section for housing the fixed contact, the movable piece, the thermally responsive element, and the positive characteristic thermistor, A circuit breaker comprising a second case attached to the first case to close the opening of the first housing, The second case comprises a main body, a cover piece embedded in the main body to reinforce the main body, a second housing that communicates with the first housing and houses the thermal responsive element when deformed, and a projection that protrudes from the inner top surface of the second housing toward the thermal responsive element. The projection is composed of a small piece fixed to the cover piece, The projection and the thermal responsive element are directly opposite each other.

4. The circuit breaker according to any one of claims 1 to 3, wherein the projection does not come into contact with the thermally responsive element when the movable piece is in the conductive state or the interrupted state.

5. The breaker according to claim 4, wherein the cover piece has a through portion that penetrates in the thickness direction in a region that overlaps with the projection when viewed in a plan view from the thickness direction.

6. The breaker according to claim 5, wherein the area of ​​the through portion perpendicular to the thickness direction is smaller than the cross-sectional area of ​​the projection perpendicular to the thickness direction.

7. The circuit breaker according to any one of claims 1 to 3, wherein the movable piece is electrically connected to the cover piece.

8. The breaker according to any one of claims 1 to 3, wherein the tip of the projection is chamfered or rounded.

9. The breaker according to any one of claims 1 to 3, wherein the projection is positioned inward from the edge of the second housing portion in the short direction of the movable piece.

10. The breaker according to any one of claims 1 to 3, wherein a plurality of projections are arranged along the short direction of the movable piece.

11. The first housing section has a third housing section for housing the positive characteristic thermistor, The breaker according to any one of claims 1 to 3, wherein the sum of the first distance from the projection to the thermal responsive element and the second distance from the third housing to the thermal responsive element is less than or equal to the thickness of the positive characteristic thermistor.

12. A safety circuit for electrical equipment comprising the circuit breaker described in any one of claims 1 to 3.

13. A secondary battery pack comprising the circuit breaker described in any one of claims 1 to 3.