Breaker, safety circuit, and secondary battery pack

Abstract

To provide a breaker capable of suppressing the movement of a positive temperature coefficient thermistor even when the breaker receives a large shock.SOLUTION: A breaker 1 includes a fixed piece 2 having a fixed contact 21, a movable piece 4 having an elastic portion 44 and a movable contact 41, a thermally responsive element 5 that deforms with temperature change, and a PTC thermistor 6. The movable piece 4 has a main body portion 45 constituting the elastic portion 44, and a first protrusion 46 protruding from the main body portion 45 toward the thermally responsive element 5. The first protrusion 46 overlaps with the PTC thermistor 6 in a plan view.SELECTED DRAWING: Figure 1

Description

[Technical field]

[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. [Background technology]

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

[0003] [Patent Document 1] WO2011 / 105175 publication Summary of the Invention [Problem to be solved by the invention]

[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 dropped or otherwise subjected to a large shock, 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 has been devised in view of the above-mentioned circumstances, and has as its main object to provide a breaker that can suppress the movement of a positive temperature coefficient thermistor even when subjected to a large shock. [Means for solving the problem]

[0007] The present invention relates to A fixed piece having a fixed contact; a movable piece having an elastic portion formed in a plate shape, which elastically deforms, 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 positive temperature coefficient thermistor that electrically connects the fixed piece and the movable piece via the thermally responsive element when the movable piece is in the interrupted state, the movable piece has a main body portion constituting the elastic portion and a first protrusion protruding from the main body portion toward the thermally responsive element, The first projection overlaps the positive temperature coefficient thermistor in a plan view seen in the thickness direction of the movable piece. Effect of the Invention

[0008] In the breaker of the present invention, the movable piece has a first protrusion on the elastic part that protrudes from the main body part 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 thus suppressing the movement of the positive temperature coefficient thermistor. Furthermore, since the first protrusion overlaps with the positive temperature coefficient thermistor in a plan view, the effect of the movable piece suppressing the movement of the positive temperature coefficient thermistor via the thermally actuated element is further enhanced. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a breaker according to an embodiment of the present invention in an unassembled state; [Diagram 2] FIG. 2 is a cross-sectional view showing the breaker in a normal charging or discharging state. [Diagram 3] 4 is a cross-sectional view showing the breaker in an overcharged state or during an abnormality. FIG. [Figure 4] FIG. 2 is a perspective view showing the movable piece of FIG. 1; [Diagram 5] FIG. 2 is a plan view of the breaker seen through the cover member of FIG. 1. [Figure 6] FIG. 4 is a cross-sectional view showing a breaker in a conductive state. [Figure 7]Cross section of the breaker shown in Figure 6 along line AA. [Figure 8] FIG. 5 is a perspective view of a modified example of the movable piece in FIG. [Figure 9] FIG. 2 is a perspective view of a modified example of the breaker of FIG. 1; [Figure 10] FIG. 10 is a perspective view of the movable piece of FIG. [Figure 11] FIG. 10 is a plan view of the breaker seen through the cover member of FIG. 9 . [Figure 12] Cross section of the breaker in Figure 11. [Figure 13] FIG. 2 is a front view of the secondary battery pack equipped with the breaker and the like shown in FIG. [Figure 14] Circuit diagram of a safety circuit equipped with the breaker shown in Figure 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A 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 breaker 1 of the present invention. The breaker 1 is mounted in an electric device or the like and protects the electric device from an excessive temperature rise or an 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 upper 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 (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 section 23 that supports the PTC thermistor 6. The PTC thermistor 6 is placed on and supported by convex projections (dowels) 24 formed in three places on the support section 23 of the fixed piece 2. By bending the fixed piece 2 in a stepped shape, the fixed contacts 21 and the support sections 23 are arranged in staggered positions, and a space for accommodating the PTC thermistor 6 can be easily secured.

[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, gold-silver alloy, etc., 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 an 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 described as the top surface, and the opposite surface is described 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, the case 10, etc.

[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 an abutment 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 abutment portion 43 abuts against the case body 7 and the cover member 8 between the terminal 42 and the elastic portion 44. The abutment 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. Due to the provision of the protruding portion 43a, the abutment portion 43 is sandwiched between the case body 7 and the cover member 8 over a wide and large area, and the movable piece 4 is firmly fixed to the case 10. In addition, the protruding portion 43a effectively functions to position the movable piece 4 relative to the case 10 and to prevent it from coming off.

[0019] The elastic portion 44 extends from the abutment portion 43 toward the movable contact 41. The movable piece 4 is supported in a cantilever manner by the case 10 at the abutment 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 portion 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] It is desirable that the movable piece 4 is curved or bent by press working at the elastic part 44. The movable piece 4 is curved or bent so that the tip of the elastic part 44 is located on the bottom side of the case 10 with respect to 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 appropriately set in consideration of 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 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 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 in a plate shape by laminating thin plate materials with different thermal expansion coefficients, and has an initial shape in which the cross section is curved in an arc shape. When the reversal operating temperature is reached due to overheating, the curved shape of the thermally responsive element 5 reversely warps with a snap motion, and returns to its original shape when the temperature falls below the normal rotation return temperature due to cooling. The initial shape of the thermally responsive element 5 can be formed by pressing. 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. However, a rectangular shape is preferable from the standpoint of productivity and efficiency of the reverse warping deformation.

[0022] As the material of the thermally responsive element 5, a laminate of two kinds of materials with different thermal expansion coefficients made of various alloys such as nickel silver, brass, and stainless steel is used in combination according to the required conditions. For example, as a material of the thermally responsive element 5 that can obtain a stable reverse operation temperature and normal rotation return temperature, a combination of a copper-nickel-manganese alloy on the high expansion side and an iron-nickel alloy on the low expansion side is preferable. Furthermore, from the viewpoint of chemical stability, a more preferable 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 viewpoint of chemical stability and processability, a more preferable 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 conducts 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 current 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 the ceramic sintered body, a so-called polymer PTC in which conductive particles such as carbon are contained in a polymer may be used.

[0024] The case body 7 and the cover member 8 constituting the case 10 are molded from thermoplastic resins such as flame-retardant polyamide, polyphenylene sulfide (PPS) with excellent heat resistance, liquid crystal polymer (LCP), polybutylene terephthalate (PBT), etc. Materials other than resins may be used as long as they have properties equal to or better than those of the above-mentioned resins.

[0025] A recess 73 is formed on the top surface side of the case body 7 as an internal space for accommodating the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, etc. 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 constituting the recess 73, and are guided during reverse warpage deformation of the thermally responsive element 5.

[0026] The lid member 8 is configured to cover the recess 73. The lid member 8 may be in a form that covers at least a portion of the recess 73. A cover piece 81 made of a metal plate mainly composed of copper or the like, stainless steel or the like may be embedded in the lid member 8 by insert molding. The cover piece 81 appropriately abuts against the top surface of the movable piece 4 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 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 accommodating 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 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 conductive state via the elastic part 44.

[0029] FIG. 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 FIG. 2 is corrected. Then, when the thermally responsive element 5 reaches the operating temperature, it snaps into an inverted shape as shown in FIG. 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. That is, the PTC thermistor 6 makes the fixed piece 2 and the movable piece 4 conductive through the thermally responsive element 5, which is causing the movable piece 4 to transition to an interrupted state. As long as such leakage current flows, the PTC thermistor 6 continues to generate heat, and the resistance value increases dramatically while maintaining the thermally responsive element 5 in a reversely 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 slight leakage current described above exists (forming a self-holding circuit). This leakage current can be used for other functions of the safety device.

[0030] When the overcharged state is released or the abnormal state is eliminated, the heat generation of the PTC thermistor 6 stops, 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 FIG. 2.

[0031] As already described, the PTC thermistor 6 is housed in the recess 73d of the case body 7. However, when the breaker 1 receives a large shock, the PTC thermistor 6 pushes up the elastic portion 44 of the movable piece 4 and jumps 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. For this reason, there is a risk that the interruption state in which the movable contact 41 is separated from the fixed contact 21 will be maintained.

[0032] 4 shows the movable piece 4. The movable piece 4 has a main body 45 constituting the elastic part 44, and a first protrusion 46 protruding 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 protruding from the main body 45 toward the thermally responsive element 5 in the elastic part 44. Therefore, even when the breaker 1 receives a large impact, the first protrusion 46 comes into contact with the thermally responsive element 5, so that the movable piece 4 suppresses the movement of the thermally responsive element 5 and presses 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.

[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 suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5.

[0034] 4 and 5, it is preferable that the first projection 46 is formed continuously over its entire circumference from the main body portion 45. Here, "the first projection 46 is formed continuously over its entire circumference from the main body portion 45" refers to a form in which the first projection 46 is not separated from the main body portion 45 via a notch, slit, or the like.

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

[0036] 6 shows the breaker 1 in a conductive state. The thermally responsive element 5 has an apex 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 protrudes toward the movable piece 4. Such a thermally responsive element 5 can instantaneously deform (so-called snap deformation) in response to a temperature change, and can instantly transition the breaker 1 from a conductive state to a cutoff state.

[0037] It is preferable that the first projection 46 is disposed in a region where the distance between the main body 45 and the thermally responsive element 5 is minimum in a cross section parallel to the longitudinal direction DrL of the movable piece 4. This reduces the clearance between the first projection 46 and the thermally responsive element 5 in the conductive state, and further enhances 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 responsive element 5 is formed in a curved shape, the distance between the main body 45 and the thermally responsive 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 area where the distance is 100% to 130% of the minimum value may be defined as the area 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 minimum 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 passes through the first projection 46 and is parallel to the short-side direction DrS of the movable piece 4.

[0041] It is preferable 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. In 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 protruding 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 deformed due to overheating comes into contact with the second protrusions 47a, 47b, the deformation of the thermally responsive element 5 is transmitted to the elastic portion 44 via the second protrusions 47a, 47b. In addition, by providing the second protrusions 47a, 47b, it is possible to easily ensure the distance between the fixed contact 21 and the movable contact 41 during interruption, and the operation of the breaker 1 is stabilized.

[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. This 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 and the thermally responsive element 5 may be in contact with each other. 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 larger 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] It is desirable that the first distance Ds1 from the first projection 46 to the thermally responsive element 5 is smaller than the second distance Ds2a from the second projection 47a to the thermally responsive element 5. Similarly, it is desirable that the first distance Ds1 from the first projection 46 to the thermally responsive element 5 is smaller than the second distance Ds2b from the second projection 47b to the thermally responsive element 5. This reduces the clearance between the first projection 46 and the thermally responsive element 5 in the conductive state, and further enhances 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. For the portions of the movable piece 4A which are not described below, the configuration of the movable piece 4 described above can be adopted.

[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 enhances 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. For parts of the breaker 1B that are not described below, the configuration of the breaker 1 described above can be adopted.

[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 the 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 is maximum in the movable piece 4B.

[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. It is preferable that the wide portion 48 overlaps with 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, since the width of the wide portion 48 in the short-side direction DrS is wider than 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 desirably curved or bent toward the PTC thermistor 6. Such a wide portion 48 reduces the clearance between the wide portion 48 and the thermally responsive element 5 in the conductive state, and the movable piece 4B can further suppress 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, and the effect of the movable piece 4B suppressing the movement of the PTC thermistor 6 via the thermally responsive element 5 is further enhanced.

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

[0057] The third projections do not need to be arranged parallel to the short-side direction DrS of the movable piece 4B, and may be arranged diagonally across the wide portion 48. In this case, it is preferable that the third projections are 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 devices, 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 an output circuit of the secondary battery 501. FIG. 14 shows a safety circuit 502 for electrical devices. The safety circuit 502 includes a breaker 1 and the like in series in an output circuit of the secondary battery 501. A part of the safety circuit 502 may be configured by a cable including a connector equipped with the breaker 1 and the like. According to the secondary battery pack 500 or the safety circuit 502 equipped with the 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 or the like even when a large shock is applied.

[0059] Although the breaker 1 of the present invention has been described in detail above, the present invention is not limited to the above specific embodiment and can be modified and implemented in various forms. For example, the breaker 1 of the present embodiment includes a movable piece 4 in which the terminal 42 or the elastic part 44 is integrally formed, but the present invention can also be applied to a form in which the terminal and the movable piece are configured as separate parts (for example, the breaker described in JP 2018-005994 A).

[0060] [Note] The present invention includes the following aspects.

[0061] [Invention 1] A fixed piece having a fixed contact; a movable piece having an elastic portion formed in a plate shape, which elastically deforms, 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 positive temperature coefficient thermistor that electrically connects the fixed piece and the movable piece via the thermally responsive element when the movable piece is in the interrupted state, the movable piece has a main body portion constituting the elastic portion and a first protrusion protruding from the main body portion toward the thermally responsive element, the first protrusion overlaps with the positive temperature coefficient thermistor in a plan view seen from the thickness direction of the movable piece; breaker. [Invention 2] The breaker according to claim 1, wherein the first projection is formed continuously from the main body over its entire periphery. [Invention 3] The thermally responsive element is formed in a curved shape that is convex toward the movable piece, The breaker according to claim 1, wherein the first projection is disposed in a region where the distance between the elastic portion and the thermally responsive element is minimum. [Invention 4] The breaker according to the first aspect of the present invention, wherein a plurality of the first protrusions are arranged along the short side direction of the movable piece. [Invention 5] The breaker according to claim 1, wherein the first projection has a longitudinal direction. [Invention 6] the movable piece has a second projection that projects from the main body toward the thermally responsive element in a region that does not overlap with the positive temperature coefficient thermistor in the plan view, The breaker according to claim 1, wherein 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. [Invention 7] A fixed piece having a fixed contact; a movable piece having an elastic portion formed in a plate shape, which elastically deforms, 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 positive temperature coefficient thermistor that electrically connects the fixed piece and the movable piece when the movable piece is in the interrupted state, the movable piece has a wide portion in the elastic portion, the wide portion having a width in a short side direction of the movable piece that is wider than the positive temperature coefficient thermistor; the wide portion overlaps with the positive temperature coefficient thermistor in a plan view seen from the thickness direction of the movable piece; breaker. [Invention 8] A breaker as described in invention 7, wherein both ends of the wide portion in the short direction are curved or bent toward the positive temperature coefficient thermistor. [The present invention 9] The breaker according to invention 7, wherein the wide portion has a third projection that projects toward the thermally responsive element. [The present invention 10] A safety circuit for an electrical device, comprising a breaker according to any one of claims 1 to 9. [The present invention 11] A secondary battery pack comprising a breaker according to any one of claims 1 to 9. [Explanation of symbols]

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

Claims

1. A fixed piece having a fixed contact; a movable piece having an elastic portion formed in a plate shape, which elastically deforms, 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 positive temperature coefficient thermistor that electrically connects the fixed piece and the movable piece via the thermally responsive element when the movable piece is in the interrupted state, the movable piece has a main body portion constituting the elastic portion and a first protrusion protruding from the main body portion toward the thermally responsive element, the first protrusion overlaps with the positive temperature coefficient thermistor in a plan view seen from the thickness direction of the movable piece; breaker.

2. The breaker according to claim 1 , wherein the first projection is formed continuously from the main body portion over an entire periphery thereof.

3. The thermally responsive element is formed in a curved shape that is convex toward the movable piece, The breaker according to claim 1 , wherein the first projection is disposed in a region where a distance between the elastic portion and the thermally responsive element is minimum.

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

5. The breaker of claim 1 , wherein the first protrusion has a longitudinal direction.

6. the movable piece has a second projection that projects from the main body toward the thermally responsive element in a region that does not overlap with the positive temperature coefficient thermistor in the plan view, 2. The breaker of claim 1, wherein a first distance from said first protrusion to said thermally responsive element is less than a second distance from said second protrusion to said thermally responsive element.

7. A fixed piece having a fixed contact; a movable piece having an elastic portion formed in a plate shape, which elastically deforms, 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 positive temperature coefficient thermistor that electrically connects the fixed piece and the movable piece when the movable piece is in the interrupted state, the movable piece has a wide portion in the elastic portion, the wide portion having a width in a short side direction of the movable piece that is wider than the positive temperature coefficient thermistor; the wide portion overlaps with the positive temperature coefficient thermistor in a plan view seen from the thickness direction of the movable piece; breaker.

8. 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 the wide portion has a third projection that projects toward the thermally responsive element.

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

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

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