Breaker, safety circuit, and secondary battery pack

Abstract

A breaker 1 comprises: a fixed piece 2 having a fixed contact 21; a movable piece 4 having an elastic part 44 and a movable contact 41; a thermoresponsive element 5 that deforms in conjunction with a change in temperature; and a PTC thermistor 6. The movable piece 4 includes: a body 45 constituting the elastic part 44; and first protrusions 46 protruding from the body 45 toward the thermoresponsive element 5. The first protrusions 46 overlap the PTC thermistor 6 in a plan view.

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 elastic portion that elastically deforms and a movable contact at one end of the elastic portion, and 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; and 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, wherein the movable piece has a main body portion that constitutes the elastic portion and a first protrusion that protrudes from the main body portion toward the thermally responsive element, and the first protrusion overlaps the positive temperature coefficient thermistor in a planar view viewed in the thickness direction of the movable piece.

[0008] In the breaker of the present invention, the movable piece has a first protrusion on the elastic portion that protrudes from the main body toward the thermally actuated element, so that even when the breaker receives a large impact, the first protrusion comes into contact with the thermally actuated element, causing the movable piece to suppress the movement of the thermally actuated element and, in turn, the movement of the PTC thermistor. Furthermore, because the first protrusion overlaps the PTC thermistor in a plan view, the effect of the movable piece suppressing the movement of the PTC thermistor via the thermally actuated element is further enhanced.

[0009] 1. A perspective view showing a breaker according to an embodiment of the present invention in an unassembled state. 2. A cross-sectional view showing the breaker in a normal charging or discharging state. 3. A cross-sectional view showing the breaker in an overcharged state or during an abnormality. 4. A perspective view showing the movable piece of FIG. 1. 5. A plan view of the breaker of FIG. 1 seen through the cover member. 6. A cross-sectional view showing the breaker in a conductive state. 7. A cross-section of the breaker of FIG. 6 taken along line A-A. 8. A perspective view of a modified example of the movable piece of FIG. 4. 9. A perspective view of a modified example of the breaker of FIG. 1. 10. A cross-sectional view of the breaker of FIG. 11. 11. A front view of a secondary battery pack including the breaker of FIG. 1 and the like. 12. A circuit diagram of a safety circuit including the breaker of FIG. 1 and the like.

[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] The breaker 1 is composed of a fixed piece 2 having a fixed contact 21, a movable piece 4 having 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 case 10 that houses the fixed piece 2, the movable piece 4, the thermally responsive element 5, and the PTC thermistor 6. The case 10 is composed of a case body (first case) 7, a cover member (second case) 8 attached to the top surface of the case body 7, and the like.

[0012] The fixed 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. 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 portion 23 that supports the PTC thermistor 6. The PTC thermistor 6 is placed on and supported by convex protrusions (dowels) 24 formed in three locations on the support portion 23 of the fixed piece 2. By bending the fixed piece 2 in a stepped manner, the fixed contacts 21 and the support portion 23 are positioned at different levels, making it easy to ensure space to accommodate the PTC thermistor 6.

[0013] The fixed contact 21 is formed at a position facing the movable contact 41 by cladding, plating, or coating with a highly conductive material such as silver, nickel, nickel-silver alloy, copper-silver alloy, or gold-silver alloy, and is exposed from a part of the opening of a recess 73a formed inside the case body 7. The terminal 22 protrudes outward from the edge of the case body 7. The support portion 23 is exposed from a recess 73d formed inside 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 movable piece 4, the thermally responsive element 5, the PTC thermistor 6, and the case 10.

[0015] The movable piece 4 is formed into an arm shape symmetrical with respect to the center line in the longitudinal direction DrL (see FIG. 4) by pressing a plate-shaped metal material mainly composed of copper or the like.

[0016] A movable contact 41 is formed at one end of the movable piece 4 in the longitudinal direction DrL. The movable contact 41 is made of, for example, 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.

[0017] A terminal 42 electrically connected to an external circuit is formed on the other end of the movable piece 4. The movable piece 4 has a contact portion 43 (corresponding to the base end of the arm-shaped movable piece 4 and the portion embedded in the case 10) and an elastic portion 44 between the movable contact 41 and the terminal 42.

[0018] The contact portion 43 contacts the case body 7 and the lid member 8 between the terminal 42 and the elastic portion 44. The contact portion 43 has a protruding portion 43a that protrudes like a wing in the short-side direction DrS (see FIG. 4 ) of the movable piece 4. By providing the protruding portion 43a, the contact portion 43 is sandwiched over a wide and large area by the case body 7 and the lid member 8, and the movable piece 4 is firmly fixed to the case 10. The protruding portion 43a also functions effectively to position the movable piece 4 relative to the case 10 and prevent it from coming off.

[0019] The elastic portion 44 extends from the abutting portion 43 toward the movable contact 41. The movable piece 4 is cantilevered by the case 10 at the abutting portion 43 on the base end side of the elastic portion 44, and when the elastic portion 44 elastically deforms in this state, the movable contact 41 formed at the tip end of the elastic portion 44 is pressed against the fixed contact 21 and comes into contact with it, allowing electricity to flow between the fixed piece 2 and the movable piece 4.

[0020] The movable piece 4 is desirably curved or bent by press working at the elastic portion 44. The movable piece 4 is curved or bent so that the tip of the elastic portion 44 is positioned closer to the bottom surface of the case 10 than the base end. The degree of curvature or bending is not particularly limited as long as it can accommodate the thermally responsive element 5, and 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.

[0021] 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 top surface of the PTC thermistor 6, which will be described later. The thermally responsive element 5 transitions the state of 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. The thermally responsive element 5 is formed into a plate shape by laminating thin plates with different thermal expansion coefficients, and has an initial shape with a curved arc-like cross section. When the reverse 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 the temperature drops below the forward rotation return temperature due to cooling. 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 elastic portion 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 portion 44, but a rectangular shape is desirable from the standpoint of productivity and efficiency of the reverse warping deformation.

[0022] 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, or stainless steel, which are combined according to the required conditions. For example, a material for the thermally responsive element 5 that can achieve stable reverse operation temperatures and forward rotation return temperatures 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, from the standpoint of chemical stability, a more desirable material is a combination of an iron-nickel-chromium alloy on the high expansion side and an iron-nickel alloy on the low expansion side. Furthermore, from the standpoint of chemical stability and processability, a more desirable material 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.

[0023] When the movable piece 4 is in an interrupted state, the PTC thermistor 6 establishes electrical continuity between the fixed piece 2 and the movable piece 4 via 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 portion 23 of the fixed piece 2 is located directly below the thermally responsive element 5, sandwiching the PTC thermistor 6 therebetween. When the electrical continuity between the fixed piece 2 and the movable piece 4 is interrupted due to reverse warpage of the thermally responsive element 5, 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 increases in resistance with increasing temperature to limit the current. 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 contained in a polymer may also be used.

[0024] 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.

[0025] A recess 73 is formed on the top surface of the case body 7, which is an internal space for accommodating the movable piece 4, the thermally responsive element 5, and the PTC thermistor 6. The recess 73 has recesses 73a and 73b for accommodating the movable piece 4, a recess 73c for accommodating the movable piece 4 and the thermally responsive element 5, and a recess 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 frames that form the recess 73, and are guided when the thermally responsive element 5 undergoes reverse warpage deformation.

[0026] The lid member 8 is configured to cover the recess 73. The lid member 8 may be configured to cover at least a portion of the recess 73. A cover piece 81 made of a metal plate mainly composed of copper or stainless steel may be embedded in the lid member 8 by insert molding. The cover piece 81 abuts against the top surface of the movable piece 4 as appropriate to restrict 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, ultimately, the case 10 serving as a housing.

[0027] 1, the cover member 8 is attached to the case body 7 so as to cover recesses 73a, 73b, 73c, etc. of the case body 7, which houses the fixed piece 2, the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, etc. The case body 7 and the cover member 8 are joined together by, for example, ultrasonic welding.

[0028] 2 and 3 show an outline of the operation of the breaker 1. Fig. 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 warping. The movable contact 41 is pressed toward the fixed contact 21 by the elastic portion 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 portion 44.

[0029] Figure 3 illustrates the operation of the breaker 1 in an overcharged state or during an abnormality. The thermally responsive element 5, which is constructed by laminating thin plates with different thermal expansion coefficients, deforms as the temperature rises, correcting its curved initial shape shown in Figure 2. When the thermally responsive element 5 reaches its operating temperature, it snaps into the inverted shape shown in Figure 3. This causes the thermally responsive element 5 to contact the elastic portion 44 of the movable contact 4, pushing the elastic portion 44 upward and separating the fixed contact 21 from the movable contact 41. At this time, the current flowing between the fixed contact 21 and the movable contact 41 is interrupted. Meanwhile, the thermally responsive element 5 contacts the movable contact 4, allowing a small leakage current to flow through the thermally responsive element 5 and the PTC thermistor 6. In other words, the PTC thermistor 6 establishes electrical continuity between the fixed contact 2 and the movable contact 4 via the thermally responsive element 5, which transitions the movable contact 4 to an interrupted state. As long as this leakage current flows, the PTC thermistor 6 continues to generate heat, maintaining the thermally responsive element 5 in a reversely curved state and dramatically increasing its resistance, so that the current does not flow through the path between the fixed contact 21 and the movable contact 41, and only the slight leakage current mentioned above exists (forming a self-holding circuit). This leakage current can be used for other functions of the safety device.

[0030] When the overcharge state is released or the abnormal state is resolved, the heat generation from the PTC thermistor 6 subsides, the temperature of the thermally responsive element 5 returns to the 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.

[0031] As already mentioned, the PTC thermistor 6 is housed in the recess 73d of the case body 7. However, when the breaker 1 receives a large impact, the PTC thermistor 6 pushes up the elastic portion 44 of the movable piece 4, jumping out of the recess 73d, and part of the periphery of the PTC thermistor 6 rides up onto the recess 73c for housing the thermally responsive element 5. This may cause the movable contact 41 to be separated from the fixed contact 21, maintaining the interrupted state.

[0032] 4 shows the movable piece 4. The movable piece 4 has a main body 45 that constitutes the elastic portion 44 and a first protrusion 46 that protrudes from the main body 45 toward the thermally responsive element 5. In the breaker 1 of the present invention, the movable piece 4 has the first protrusion 46 that protrudes from the main body 45 toward the thermally responsive element 5 in the elastic portion 44. Therefore, even when the breaker 1 receives a large impact, the first protrusion 46 comes into contact with the thermally responsive element 5, causing the movable piece 4 to restrict the movement of the thermally responsive element 5 and press the thermally responsive element 5 toward the PTC thermistor 6. This restricts the movement of the PTC thermistor 6 and prevents it from jumping out of the recess 73d.

[0033] 5 is a plan view of the breaker 1 seen through the cover member 8. In this embodiment, the first protrusion 46 overlaps with the PTC thermistor 6 in a plan view seen from the thickness direction of the movable piece 4. This further enhances the effect of the movable piece 4 in suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5.

[0034] 4 and 5, it is desirable that the first protrusion 46 is formed continuously over its entire periphery from the main body portion 45. Here, "the first protrusion 46 is formed continuously over its entire periphery from the main body portion 45" means that the first protrusion 46 is not separated from the main body portion 45 via a notch, a slit, or the like.

[0035] In the breaker 1 of this embodiment, the first protrusion 46 is formed continuously from the main body 45 around its entire periphery, so that the amount of protrusion of the first protrusion 46 relative to the main body 45 is stable when the first protrusion 46 abuts against the thermally responsive element 5 and presses the thermally responsive element 5 toward the PTC thermistor 6. This further suppresses movement of the PTC thermistor 6.

[0036] 6 shows the breaker 1 in a conductive state. The thermally responsive element 5 has a top 51 that protrudes toward the movable piece 4 in the conductive state. This causes the thermally responsive element 5 to assume a curved shape that is convex toward the movable piece 4. Such a thermally responsive element 5 can instantaneously deform (so-called snap deformation) in response to a temperature change, causing the breaker 1 to instantly transition from a conductive state to a cut-off state.

[0037] The first protrusion 46 is preferably disposed in a region where the distance between the main body 45 and the thermally responsive element 5 is smallest in a cross section parallel to the longitudinal direction DrL of the movable piece 4. This reduces the clearance between the first protrusion 46 and the thermally responsive element 5 in the conductive state, further enhancing the effect of the movable piece 4 suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5.

[0038] Since the thermally actuated element 5 is formed in a curved shape, the distance between the main body 45 and the thermally actuated element 5 is often smallest at a certain point. However, in an extremely small breaker 1, it is difficult to identify the point where the distance is smallest. In such a case, for example, the region where the distance is 100% to 130% of the minimum value may be defined as the region where the distance is smallest.

[0039] The thermally responsive element 5 is usually placed on the top surface of the PTC thermistor 6 so that the center of the thermally responsive element 5 coincides with the center of the PTC thermistor 6 in the longitudinal direction DrL of the movable piece 4. As already mentioned, the elastic part 44 of the movable piece 4 is curved or bent by press working, so that when the side of the movable contact 41 is the front side, the elastic part 44 is configured to be inclined forward toward the tip. Therefore, the area where the distance between the main body part 45 and the thermally responsive element 5 is smallest is located forward of the center of the thermally responsive element 5 in the longitudinal direction DrL of the movable piece 4.

[0040] Fig. 7 shows a cross section of the breaker 1 taken along line AA in Fig. 6. The cross section of line AA is a cross section of the breaker 1 that passes through the first protrusion 46 and is parallel to the short-side direction DrS of the movable piece 4.

[0041] It is desirable that a plurality of first protrusions 46 are arranged along the short-side direction DrS of the movable piece 4. In this embodiment, a pair of first protrusions 46 are arranged parallel to the short-side direction DrS of the movable piece 4. The pair of first protrusions 46 are provided symmetrically with respect to the center line of the longitudinal direction DrL of the movable piece 4. With this configuration, protrusion of the PTC thermistor 6 in the short-side direction DrS, as shown by the dashed line in FIG. 7, is suppressed. The number of first protrusions 46 may be three or more, and a plurality of first protrusions 46 may be arranged parallel to the longitudinal direction DrL of the movable piece 4.

[0042] 1 to 6, the movable piece 4 may have a pair of second protrusions 47a, 47b that protrude from the main body 45 toward the thermally responsive element 5. The second protrusions 47a, 47b are formed in an area that does not overlap with the PTC thermistor 6 in a plan view (see FIG. 5).

[0043] 3, when the thermally responsive element 5 is deformed due to overheating, it comes into contact with the second protrusions 47a and 47b, and the deformation of the thermally responsive element 5 is transmitted via the second protrusions 47a and 47b to the elastic portion 44. Furthermore, the provision of the second protrusions 47a and 47b makes it possible to easily ensure the distance between the fixed contact 21 and the movable contact 41 during breaking, stabilizing the operation of the breaker 1.

[0044] 2, the thermally responsive element 5 is spaced apart from the second protrusions 47a and 47b of the movable piece 4 in the conductive state, which makes it easier to maintain the contact pressure between the movable contact 41 and the fixed contact 21, stabilizing the contact resistance therebetween.

[0045] The elastic portion 44 of the movable piece 4 may be in contact with the thermally responsive element 5. In this case, the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, and the fixed piece 2 are 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.

[0046] The first distance Ds1 from the first protrusion 46 to the thermally responsive element 5 is preferably smaller than the second distance Ds2a from the second protrusion 47a to the thermally responsive element 5. Similarly, the first distance Ds1 from the first protrusion 46 to the thermally responsive element 5 is preferably smaller than the second distance Ds2b from the second protrusion 47b to the thermally responsive element 5. This reduces the clearance between the first protrusion 46 and the thermally responsive element 5 in the conductive state, further enhancing the effect of the movable piece 4 suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5.

[0047] Fig. 8 is a perspective view of a movable piece 4A which is a modified example of the movable piece 4 in Fig. 4. The configuration of the movable piece 4 described above can be adopted for the portions of the movable piece 4A which are not described below.

[0048] In the movable piece 4A, the first protrusion 46A has a longitudinal direction. In this embodiment, the longitudinal direction of the first protrusion 46A coincides with the longitudinal direction DrL of the movable piece 4A. Such a first protrusion 46A also functions as a reinforcing rib that increases the elastic force of the elastic portion 44 of the movable piece 4A. The longitudinal direction of the first protrusion 46A may be configured to coincide with the lateral direction DrS of the movable piece 4A.

[0049] Fig. 9 is a perspective view of a breaker 1B which is a modified example of the breaker 1 in Fig. 1. The configuration of the breaker 1 described above can be adopted for parts of the breaker 1B that are not described below.

[0050] Breaker 1B differs from breaker 1 in that it includes a movable piece 4B.

[0051] 10 shows the movable piece 4B. The movable piece 4B has a wide portion 48 in the elastic portion 44. The wide portion 48 is a portion of the movable piece 4B whose width in the short-side direction DrS is wider than that of the PTC thermistor 6. In this embodiment, the wide portion 48 is formed by extending both end edges of the elastic portion 44 in the short-side direction DrS in the short-side direction DrS. The wide portion 48 may extend in the short-side direction DrS so that its width in the short-side direction DrS is wider than that of the abutting portion 43, that is, so that the width in the short-side direction DrS of the movable piece 4B is maximum.

[0052] In the breaker 1B, the movable piece 4B has a wide portion 48 in the elastic portion 44, so that even when the breaker 1B receives a large impact, the wide portion 48 comes into contact with the thermally responsive element 5, causing the movable piece 4B to suppress the movement of the thermally responsive element 5 and press the thermally responsive element 5 toward the PTC thermistor 6. This suppresses the movement of the PTC thermistor 6 and prevents it from jumping out of the recess 73d.

[0053] 11 is a plan view of the breaker 1B seen through the cover member 8. The wide portion 48 desirably overlaps the PTC thermistor 6 in a plan view seen from the thickness direction of the movable piece 4B. This further enhances the effect of the movable piece 4B suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5. In addition, because the width of the wide portion 48 in the short-side direction DrS is wider than that of the PTC thermistor 6, the effect of the movable piece 4B suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5 is further enhanced.

[0054] 12 shows a cross section parallel to the short-side direction DrS of the movable piece 4B of the breaker 1B. Both ends of the wide portion 48 in the short-side direction DrS are preferably curved or bent toward the PTC thermistor 6. Such wide portion 48 reduces the clearance between the wide portion 48 and the thermally responsive element 5 in the conductive state, further enhancing the effect of the movable piece 4B suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5.

[0055] Furthermore, the wide portion 48 may be provided with a third protrusion (not shown) that protrudes toward the thermally responsive element 5. Such a third protrusion reduces the clearance between the third protrusion and the thermally responsive element 5 in the conductive state, further enhancing the effect of the movable piece 4B suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5.

[0056] It is preferable to provide a plurality of third protrusions. In this case, it is preferable that the plurality of third protrusions are arranged along the short-side direction DrS of the movable piece 4B. For example, it is preferable that the third protrusions are arranged outside the PTC thermistor 6 in a plan view seen from the thickness direction of the movable piece 4.

[0057] The third protrusions do not need to be arranged parallel to the short-side direction DrS of the movable piece 4B, but may be arranged diagonally across the wide portion 48. In this case, it is desirable that the third protrusions be arranged at positions symmetrical with respect to the center of the PTC thermistor 6 in the plan view.

[0058] 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. 13 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. 14 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.

[0059] 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 embodied in various forms. For example, the breaker 1 and the like of this embodiment include a movable piece 4 in which the terminal 42 and the elastic portion 44 are integrally formed, but the present invention can also be applied to a configuration in which the terminal and the movable piece are formed as separate parts (for example, the breaker described in JP 2018-005994 A).

[0060] [Additional Notes] The present invention includes the following aspects.

[0061] [Invention 1] A breaker comprising: a fixed piece having a fixed contact; a movable piece having a plate-shaped elastic portion that elastically deforms 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 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; and 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, wherein the movable piece has a main body that constitutes the elastic portion and a first protrusion that protrudes from the main body toward the thermally responsive element, and the first protrusion overlaps the positive temperature coefficient thermistor in a plan view seen in the thickness direction of the movable piece. [Invention 2] The breaker according to Invention 1, wherein the first protrusion is formed continuously from the main body around its entire circumference. [Invention 3] The breaker according to Invention 1, wherein the thermally responsive element is formed in a curved shape convex toward the movable piece, and the first protrusion is arranged in a region where the distance between the elastic portion and the thermally responsive element is shortest. [Invention 4] The breaker according to Invention 1, wherein a plurality of the first protrusions are arranged along the short direction of the movable piece. [Invention 5] The breaker according to Invention 1, wherein the first protrusion has a longitudinal direction. [Invention 6] The breaker according to Invention 1, wherein the movable piece has a second protrusion that protrudes from the main body portion toward the thermally responsive element in a region that does not overlap with the positive temperature coefficient thermistor in the plan view, and wherein a first distance from the first protrusion to the thermally responsive element is shorter than a second distance from the second protrusion to the thermally responsive element.[Invention 7] A breaker comprising: a fixed piece having a fixed contact; a movable piece formed in a plate-like 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 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; and a positive temperature coefficient thermistor that provides electrical continuity between the fixed piece and the movable piece when the movable piece is in the cut-off state, wherein the movable piece has a wide portion in the elastic portion that is wider in the lateral direction than the positive temperature coefficient thermistor, and the wide portion overlaps the positive temperature coefficient thermistor in a plan view seen from the thickness direction of the movable piece. [Invention 8] The breaker according to Invention 7, wherein both ends in the lateral direction of the wide portion are curved or bent toward the positive temperature coefficient thermistor. [Invention 9] The breaker according to Invention 7, wherein the wide portion has a third protrusion protruding toward the thermally responsive element. [Invention 10] A safety circuit for an electrical device, comprising the breaker according to any one of Inventions 1 to 9. [Invention 11] A secondary battery pack, comprising the breaker according to any one of Inventions 1 to 9.

[0062] 1: Breaker 1B: Breaker 2: Fixed piece 4: Movable piece 4A: Movable piece 4B: Movable piece 5: Thermally responsive element 6: PTC thermistor 21: Fixed contact 24: Protrusion 41: Movable contact 44: Elastic portion 44a: Protrusion 44b: Protrusion 45: Main body portion 46: First protrusion 46A: First protrusion 47a: Second protrusion 47b: Second protrusion 48: Wide portion 500: Secondary battery pack 501: Secondary battery 502: Safety circuit Ds1: First distance Ds2a: Second distance Ds2b: Second distance

Claims

1. A breaker comprising: a fixed piece having a fixed contact; a movable piece formed in a plate shape and having an elastic portion that elastically deforms and a movable contact at one end of the elastic portion, pressing the movable contact against the fixed 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; and 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, wherein the movable piece has a main body that constitutes the elastic portion and a first protrusion that protrudes from the main body toward the thermally responsive element, and the first protrusion overlaps the positive temperature coefficient thermistor in a plan view seen in the thickness direction of the movable piece.

2. The breaker according to claim 1, wherein said first projection is formed continuously from said main body portion around its entire periphery.

3. The breaker as described in claim 1, wherein the thermally responsive element is formed in a curved shape that is convex toward the movable piece, and the first protrusion is disposed in an area where the distance between the elastic portion and the thermally responsive element is minimum.

4. The breaker according to claim 1, wherein a plurality of said first projections are arranged along the short side direction of said movable piece.

5. The breaker of claim 1, wherein said first projection has a longitudinal direction.

6. A breaker as described in claim 1, wherein the movable piece has a second protrusion protruding from the main body portion toward the thermally responsive element in an area not overlapping with the positive temperature coefficient thermistor in the planar view, and a first distance from the first protrusion to the thermally responsive element is smaller than a second distance from the second protrusion to the thermally responsive element.

7. A breaker comprising: a fixed piece having a fixed contact; a movable piece formed in a plate shape and having an elastic portion that elastically deforms and a movable contact at one end of the elastic portion, pressing the movable contact into contact with the fixed 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; and a positive temperature coefficient thermistor that provides electrical continuity between the fixed piece and the movable piece when the movable piece is in the cut-off state, wherein the movable piece has a wide portion in the elastic portion whose width in the short direction of the movable piece is wider than that of the positive temperature coefficient thermistor, and the wide portion overlaps with the positive temperature coefficient thermistor in a plan view seen in the thickness direction of the movable piece.

8. The breaker according to claim 7, wherein both ends of the wide portion in the short direction are curved or bent toward the positive temperature coefficient thermistor.

9. The breaker according to claim 7, wherein said wide portion has a third projection protruding toward said thermally responsive element.

10. A safety circuit for electrical equipment comprising a circuit breaker according to any one of claims 1 to 9.

11. A secondary battery pack comprising a breaker according to any one of claims 1 to 9.

Images