Breaker, safety circuit for electrical equipment and secondary battery pack

Abstract

To provide a breaker capable of maintaining a stable conductive state even when used at extremely low temperatures.SOLUTION: A breaker 1 includes a fixed piece 2 having a fixed contact 21, a movable piece 4 formed in a plate shape, having an elastically deformable elastic portion 43 and a movable contact 41 at one end of the elastic portion 43, and pressing the movable contact 41 into contact with the fixed contact 21, and a thermally responsive element 5 which deforms with a change in temperature to transition the movable piece 4 from a conductive state in which the movable contact 41 is in contact with the fixed contact 21 to a cutoff state in which the movable contact 41 is separated from the fixed contact 21. The movable piece 4 includes a thin portion 45 which is recessed in the opposite direction to the thermally responsive element 5 in its thickness direction.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, the thermally responsive element is curved so that its center protrudes toward the movable piece. When the temperature of this type of thermally responsive element rises, the peripheral part of the element pushes up the movable piece, separating the movable contact from the fixed contact.

[0005] However, when the electrical equipment is exposed to extremely low temperatures, the degree of curvature of the thermally responsive element increases, and the center of the element may push up the movable piece, causing the movable contact to separate from the fixed contact. Even if the movable contact does not separate, the contact pressure between the movable contact and the fixed contact decreases, and the resistance across the breaker increases.

[0006] The present invention has been devised in view of the above circumstances, and has as its main object to provide a breaker that can maintain a stable conductive state even when used at extremely low temperatures. [Means for solving the problem]

[0007] The present invention includes 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, The movable piece has a thin-walled portion that is recessed in a thickness direction opposite to the thermally responsive element. It's a breaker. Effect of the Invention

[0008] Because the breaker of the present invention has the above-mentioned configuration, even when used at extremely low temperatures, the center of the thermally responsive element is prevented from pushing up the movable piece, and a stable conductive state can be maintained between the movable contact and the fixed contact. [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] 2 is a perspective view showing the configuration of the movable piece in FIG. 1 with a part cut away. FIG. [Diagram 5] FIG. 4 is a cross-sectional view of the breaker in a cryogenic state. [Figure 6] FIG. 2 is a plan view of the movable piece and the thermally responsive element shown in FIG. [Figure 7] 5 is a perspective view showing a configuration of a modified example of the movable piece 4 in FIG. 4 with a part cut away. [Figure 8] FIG. 2 is a front view of the secondary battery pack equipped with the breaker and the like shown in FIG. [Figure 9] 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] 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, the terminal piece 3, 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 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.

[0013] The fixed contact 21 is formed by cladding, plating, or coating a material with good conductivity such as silver, nickel, nickel-silver alloy, copper-silver alloy, gold-silver alloy, etc. The fixed contact 21 is formed at a position facing the movable contact 41 of the fixed piece 2, and is exposed to the housing part 73 of the case body 7 from a part of a recess 73a 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 terminal piece 3, the movable piece 4, the thermally responsive element 5, the case 10, the cover piece 9, etc.

[0015] The terminals 22 protrude from the side walls of the case body 7 and are connected to lands on a circuit board or tabs on a secondary battery circuit, etc. The terminals 22 may be configured to be exposed from the bottom wall of the case body 7.

[0016] 2, the fixed piece 2 has a support portion 23 that supports the PTC thermistor 6, and a stepped bent portion 25 that is bent in a stepped shape (crank-shaped in side view). The stepped bent portion 25 connects the fixed contact 21 and the support portion 23, and arranges the fixed contact 21 and the support portion 23 at different heights. The PTC thermistor 6 is placed on and supported by convex projections (dowels) 24 formed in three places on the support portion 23. By bending the fixed piece 2 in a stepped shape and arranging the fixed contact 21 and the support portion 23 at different levels, a space for storing the PTC thermistor 6 can be easily secured.

[0017] The terminal piece 3, like the fixed piece 2, is formed by pressing a metal plate mainly composed of copper or the like, and is embedded in the case body 7 by insert molding. The terminal piece 3 has a connection portion 31 connected to the movable piece 4, and a terminal 32.

[0018] The connection portion 31 is exposed to the 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. Meanwhile, the terminal 32 protrudes from the side wall of the case body 7 on the opposite side to the terminal 22, and is connected to a land portion of a circuit board or a tab of a secondary battery circuit, or the like. The terminal 32 may be configured to be exposed from the bottom wall of the case body 7.

[0019] The movable piece 4 is formed into a plate shape by pressing a metal material mainly composed of copper etc. The movable piece 4 is formed into an arm shape symmetrical with respect to a center line in the longitudinal direction.

[0020] 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 part 42 described later), and the terminal 32 protrudes from the side wall of the case body 7.

[0021] A movable contact 41 is formed on 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 techniques.

[0022] The other end of the movable piece 4 is formed with a connection part 42 that is electrically connected to the connection part 31 of the terminal piece 3. The top surface of the connection part 31 of the terminal piece 3 and the bottom surface of the connection part 42 of the movable piece 4 are fixed to each other by, for example, laser welding. Laser welding is a welding method in which a laser beam is irradiated onto the workpieces (corresponding to the terminal piece 3 and the movable piece 4 in this embodiment) to locally melt and solidify the workpieces, thereby joining the workpieces together. On the surface of the workpiece irradiated with the laser beam, a laser weld mark is formed that is different in shape from the weld marks formed by other welding methods (for example, resistance welding that utilizes Joule heat).

[0023] The movable piece 4 has an elastic portion 43 between the movable contact 41 and the connection portion 42. The elastic portion 43 extends from the connection portion 42 toward the movable contact 41. As a result, the connection portion 42 is provided on the opposite side to the movable contact 41 with the elastic portion 43 in between.

[0024] 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 of the elastic part 43 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. The movable piece 4 and the terminal piece 3 are electrically connected at the connection parts 31 and 42, allowing electricity to flow between the fixed piece 2 and the terminal piece 3.

[0025] The movable piece 4 is curved or bent at the elastic portion 43 by press processing. 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, and the like. In addition, 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 come into contact with 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).

[0026] The thermally responsive element 5 transitions 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 has an initial shape with a cross section curved in an arc shape so as to be convex toward the movable piece 4, and is formed by laminating thin plate materials with different thermal expansion coefficients. When the operating temperature is reached by overheating, the curved shape of the thermally responsive element 5 reverse warps with a snap motion, and returns to its original shape when cooled below the return temperature. The initial shape of the thermally responsive element 5 can be formed by pressing. As long as the elastic part 43 of the movable piece 4 is pushed up by the reverse warping action of the thermally responsive element 5 at a desired temperature and returns to its original shape by the elastic force of the elastic part 43, the material and shape of the thermally responsive element 5 are not particularly limited, but a rectangular shape is preferable from the viewpoint of productivity and efficiency of the reverse warping action, and a rectangular shape close to a square is preferable in order to efficiently push up the elastic part 43 while being small in size. The material for 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, which are combined according to the required conditions.

[0027] The PTC thermistor 6 conducts 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 23 of the fixed piece 2 and the thermally responsive element 5. That is, the support 23 is located directly below the thermally responsive element 5, sandwiching the PTC thermistor 6. When the electrical connection between the fixed piece 2 and the movable piece 4 is interrupted by the reverse warping 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.

[0028] 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.

[0029] The top surface of the case body 7 is provided with a storage section 73, which is an internal space for storing the movable piece 4, the thermally responsive element 5, the PTC thermistor 6, and the like. The storage section 73 is recessed from the joint surface with the cover member 8 (the top surface of the case body 7) toward the bottom surface of the case body 7. The storage section 73 has recesses 73a and 73b for storing the movable piece 4, a recess 73c for storing the movable piece 4 and the thermally responsive element 5, and a recess 73d for storing 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 a frame constituting the storage section 73, and are guided during reverse warpage deformation of the thermally responsive element 5.

[0030] 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 metal mainly composed of copper or stainless steel. The cover piece 9 increases the rigidity and strength of the lid member 8 and, in turn, the case 10 serving as a housing, while contributing to the miniaturization of the breaker 1.

[0031] As shown in FIG. 1, the cover member 8 is attached to the case body 7 so as to close the recesses 73a, 73b, 73c, etc. of the case body 7 that accommodates the fixed piece 2, the terminal piece 3, 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 by, for example, ultrasonic welding. At this time, the case body 7 and the cover member 8 are continuously joined over the entire circumference of their respective outer edges, improving the airtightness of the case 10. As a result, the internal space of the case 10 created by the accommodation portion 73 is sealed, and the components such as the movable piece 4, the thermally responsive element 5, and the PTC thermistor 6 are isolated from the atmosphere outside the case 10 and can be protected. In this embodiment, the resin is entirely disposed on the top surface side of the cover piece 9, so that the airtightness of the accommodation portion 73 is further improved.

[0032] 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). At this time, the fixed piece 2 and the terminal piece 3 of the breaker 1 are electrically connected through the elastic part 43 of the movable piece 4 and the like. The elastic part 43 of the movable piece 4 and the thermally responsive element 5 may be in contact with each other, 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 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.

[0033] FIG. 3 shows the operation of the breaker 1 in an overcharged state or an abnormality. When the breaker 1 is in a high temperature state due to overcharge or an abnormality, the thermally responsive element 5 reaches its operating temperature and warps inversely, pushing up the elastic part 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 the thermally responsive element 5 is deformed 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 cut off, 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 such leakage current flows, and the resistance value increases dramatically while maintaining the thermally responsive element 5 in a 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 above-mentioned small leakage current exists (constituting a self-holding circuit). This leakage current can be used for other functions of the safety device.

[0034] 4 shows a partially cutaway configuration of the movable piece 4. The movable piece 4 has a thin-walled portion 45 that is thinner than the surrounding area in the elastic portion 43. The thin-walled portion 45 is formed by the bottom surface of the movable piece 4 being recessed in the thickness direction of the movable piece 4 in the opposite direction to the thermally responsive element 5.

[0035] 5 shows the circuit breaker 1 in an extremely low temperature state. The extremely low temperature state refers to a state in which the ambient temperature around an electrical device in which the circuit breaker 1 is mounted is -10°C or lower, for example.

[0036] 5, in the breaker 1 in an extremely low temperature state, the degree of curvature of the thermally responsive element 5 increases, and the central portion 51 approaches the bottom surface of the movable piece 4. However, in the movable piece 4 of this embodiment, a thin-walled portion 45 that is recessed in the opposite direction to the thermally responsive element 5 is formed on the bottom surface of the elastic portion 43, so that the central portion 51 of the thermally responsive element 5 is prevented from contacting the movable piece 4. As a result, even in an extremely low temperature state, the central portion 51 of the thermally responsive element 5 is prevented from pushing up the elastic portion 43 of the movable piece 4, and a stable conductive state can be maintained between the movable contact 41 and the fixed contact 21.

[0037] Furthermore, as shown in FIG. 1, a thin portion 45 is formed in the movable piece 4 in an area facing the central portion 51 of the thermally responsive element 5, so that the movable piece 4 can be positioned close to the thermally responsive element 5, making it possible to easily make the breaker 1 thinner.

[0038] At the thin-walled portion 45, it is desirable that the top surface of the movable piece 4 is substantially flat. The term "substantially flat" is not limited to a completely flat shape, but rather intends to allow slight curvature or the like that is originally formed in the elastic part 43 around the thin-walled portion 45. In other words, it is desirable that at the thin-walled portion 45, the bottom surface of the movable piece 4 is recessed so that the top surface of the movable piece 4 does not protrude. With such a configuration, the cover piece 9 can be disposed close to the movable piece 4, and it is possible to easily make the breaker 1 thinner.

[0039] 4, the movable piece 4 has a longitudinal direction DL in which the elastic portion 43 extends toward the movable contact 41, and a lateral direction DS perpendicular to the longitudinal direction DL. When the longitudinal direction DL and the lateral direction DS are defined as above, FIGS. 2, 3, and 5 are cross sections perpendicular to the lateral direction DS passing through the center of the breaker 1 in the lateral direction DS.

[0040] It is desirable that the thin portion 45 is disposed in a region where the distance between the elastic portion 43 and the thermally responsive element 5 is the smallest when viewed from the short side direction DS. With this configuration, even in an extremely low temperature state, the center portion 51 of the thermally responsive element 5 is further prevented from pushing up the elastic portion 43 of the movable piece 4, and a stable conductive state can be maintained between the movable contact 41 and the fixed contact 21. In addition, the movable piece 4 can be disposed even closer to the thermally responsive element 5, and the breaker 1 can be easily made thinner. The distance between the elastic portion 43 and the thermally responsive element 5 is measured with the breaker 1 placed in an atmosphere at room temperature (e.g., 20°C).

[0041] FIG. 6 is a plan view of the movable piece 4 and the thermally responsive element 5 as viewed from the thickness direction of the movable piece 4. As shown in FIG.

[0042] 4 and 6, the elastic portion 43 has a maximum width portion 46 in which the length L1 in the short side direction DS is maximum. The maximum width portion 46 is formed by expanding the central region in the longitudinal direction DL of the elastic portion 43 in the short side direction DS. The maximum width portion 46 easily increases the elastic force generated by the elastic portion 43, improving the contact pressure between the movable contact 41 and the fixed contact 21 and reducing the contact resistance between them.

[0043] In this embodiment, it is preferable that the thin-walled portion 45 is formed in the maximum width portion 46. According to such a configuration, the reduction in elastic force caused by the formation of the thin-walled portion 45 in the elastic portion 43 is compensated for by the maximum width portion 46, and it becomes possible to easily maintain the contact pressure between the movable contact 41 and the fixed contact 21 at an appropriate value or higher. In addition, an increase in conductor resistance caused by the formation of the thin-walled portion 45 in the elastic portion 43 is suppressed, and it becomes possible to suppress the voltage drop in the movable piece 4.

[0044] 6, it is preferable that the area center 45c of the thin portion 45 is located closer to the movable contact 41 than the area center 5c of the thermally responsive element 5. With this configuration, it is possible to easily maintain the contact pressure between the movable contact 41 and the fixed contact 21 at an appropriate value or higher.

[0045] As shown in FIG. 4, the thin portion 45 is formed by providing a hole 45A in the movable piece 4. The bottom of the hole 45A constitutes the thin portion 45. The hole 45A is formed on the bottom surface of the movable piece 4 so as to face the center portion 51 of the thermally responsive element 5. In the breaker 1 in an extremely low temperature state, the center portion 51 of the thermally responsive element 5 is accommodated in the hole 45A formed in the movable piece 4, and the center portion 51 of the thermally responsive element 5 is prevented from pushing up the elastic portion 43 of the movable piece 4. Note that the hole 45A is desirably formed to have a size sufficient to accommodate the center portion 51 of the thermally responsive element 5, the degree of curvature of which increases in an extremely low temperature state, and is desirably formed to have a size that does not reach the edge of the elastic portion 43 in the short-side direction DS.

[0046] It is preferable that the hole 45A is formed in a tapered shape such that the area in a plan view seen from the thickness direction of the movable piece 4 increases toward the thermally responsive element 5. With this configuration, even in an extremely low temperature state, the central part 51 of the thermally responsive element 5 is further prevented from pushing up the elastic part 43 of the movable piece 4.

[0047] The thin-walled portion 45 may be formed in an elliptical shape having a major axis in the longitudinal direction DL. By combining such a thin-walled portion 45 with a rectangular thermally responsive element 5 having a long side in the longitudinal direction DL, the central portion 51 of the thermally responsive element 5 is further prevented from pushing up the elastic portion 43 of the movable piece 4 even in an extremely low temperature state. In addition, the formation of the thin-walled portion 45 in the elastic portion 43 prevents a decrease in elastic force, making it possible to easily maintain the contact pressure between the movable contact 41 and the fixed contact 21 at an appropriate value or higher. In addition, the formation of the thin-walled portion 45 in the elastic portion 43 prevents an increase in conductor resistance, making it possible to suppress a voltage drop in the movable piece 4.

[0048] 6, in the elastic portion 43, the difference W1A-W1B between the width W1A in the short-side direction DS of the first portion 47 in which the thin portion 45 is formed and the width W1B in the short-side direction DS of the thin portion 45 is preferably equal to or greater than the width W2 in the short-side direction DS of the second portion 48 in which the movable contact 41 is formed. With this configuration, the reduction in elastic force caused by the formation of the thin portion 45 in the elastic portion 43 is suppressed, and it becomes possible to easily maintain the contact pressure between the movable contact 41 and the fixed contact 21 at an appropriate value or higher. In addition, the increase in conductor resistance caused by the formation of the thin portion 45 in the elastic portion 43 is suppressed, and it becomes possible to suppress the voltage drop in the movable piece 4.

[0049] The thickness of the elastic portion 43 is preferably 0.05 to 0.2 mm. By making the thickness of the elastic portion 43 0.05 mm or more, the decrease in elastic force caused by the formation of the thin portion 45 in the elastic portion 43 is suppressed, and it becomes possible to easily maintain the contact pressure between the movable contact 41 and the fixed contact 21 at an appropriate value or higher. In addition, the increase in conductor resistance caused by the formation of the thin portion 45 in the elastic portion 43 is suppressed, and it becomes possible to suppress the voltage drop in the movable piece 4. On the other hand, by making the thickness of the elastic portion 43 0.2 mm or less, it becomes possible to easily make the breaker 1 thinner.

[0050] Fig. 7 is a perspective view showing a movable piece 4A, which is a modified example of the movable piece 4 in Fig. 4, with a part cut away. For the parts of the movable piece 4A that are not described below, the configuration of the movable piece 4 described above can be adopted.

[0051] 7, the movable piece 4A differs from the movable piece 4 in that a hole 45A penetrates the elastic portion 43. Since the hole 45A penetrates the elastic portion 43, the movable piece 4A has a configuration in which the thickness of the thin-walled portion 45 is zero.

[0052] With the movable piece 4A, even in an extremely low temperature state, the center part 51 of the thermally responsive element 5 is further prevented from pushing up the elastic part 43 of the movable piece 4, and a stable conductive state can be maintained between the movable contact 41 and the fixed contact 21. Also, the movable piece 4 can be arranged even closer to the thermally responsive element 5, which makes it easy to make the breaker 1 thinner. Furthermore, the movable piece 4A can be manufactured more cheaply and easily than the movable piece 4.

[0053] 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. 8 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. 9 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 formed by a cable including a connector equipped with the breaker 1 and the like. By using 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 maintain a stable conduction state even in an extremely low temperature state.

[0054] 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 may be modified and embodied in various forms. [Note] The present invention includes the following aspects.

[0055] [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, The movable piece has a thin-walled portion that is recessed in a thickness direction opposite to the thermally responsive element. breaker. [Invention 2] the thin-walled portion is formed by providing a hole in the movable piece, The breaker according to claim 1, wherein the hole penetrates the movable piece in the thickness direction. [Invention 3] The thermally responsive element is formed in a curved shape that is convex toward the movable piece, the movable piece has a longitudinal direction in which the elastic portion extends toward the movable contact and a lateral direction perpendicular to the longitudinal direction, The breaker according to claim 1, wherein the thin portion is disposed in a region where the distance between the elastic portion and the thermally responsive element is minimum when viewed from the short side direction. [Invention 4] the movable piece has a longitudinal direction in which the elastic portion extends toward the movable contact and a lateral direction perpendicular to the longitudinal direction, The elastic portion has a maximum width portion whose length in the short side direction is maximum, 2. The breaker according to claim 1, wherein the thin-walled portion is formed in the maximum width portion. [Invention 5] The breaker according to claim 1, wherein, in a plan view seen from the thickness direction of the movable piece, the center of area of ​​the thin portion is located closer to the movable contact than the center of area of ​​the thermally responsive element. [Invention 6] the thin-walled portion is formed by providing a hole in the movable piece, The breaker according to claim 1, wherein the hole is formed in a tapered shape such that the area in a plan view seen from the thickness direction increases toward the thermally responsive element. [Invention 7] the movable piece has a longitudinal direction in which the elastic portion extends toward the movable contact and a lateral direction perpendicular to the longitudinal direction, The breaker according to claim 1, wherein the thin portion is formed in an elliptical shape having a major axis in the longitudinal direction. [Invention 8] the movable piece has a longitudinal direction in which the elastic portion extends toward the movable contact and a lateral direction perpendicular to the longitudinal direction, The breaker described in invention 1, wherein in the elastic portion, the difference W1A-W1B between the short-side width W1A of the first portion in which the thin-walled portion is formed and the short-side width W1B of the thin-walled portion is greater than or equal to the short-side width W2 of the second portion in which the movable contact is formed. [The present invention 9] 2. The breaker according to claim 1, wherein the elastic portion has a thickness of 0.05 to 0.2 mm. [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]

[0056] 1: Breaker 2: Fixed piece 4: Movable piece 4A: Movable piece 5: Thermal response element 5c: center of area 21: Fixed contact 41: Movable contact 43: Elastic part 45: Thin section 45A: Hole 45c: center of area 46: Maximum width part 47 :1st part 48:Second part 500: Secondary battery pack 501: Secondary battery 502 :Safety circuit DL: Longitudinal direction DS: Short direction W1A: Width W1B:Width W2:Width

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, The movable piece has a thin-walled portion that is recessed in a thickness direction opposite to the thermally responsive element. breaker.

2. the thin-walled portion is formed by providing a hole in the movable piece, The breaker according to claim 1 , wherein the hole penetrates the movable piece in the thickness direction.

3. The thermally responsive element is formed in a curved shape that is convex toward the movable piece, the movable piece has a longitudinal direction in which the elastic portion extends toward the movable contact and a lateral direction perpendicular to the longitudinal direction, The breaker according to claim 1 , wherein the thin portion is disposed in a region where a distance between the elastic portion and the thermally responsive element is minimum when viewed in the short side direction.

4. the movable piece has a longitudinal direction in which the elastic portion extends toward the movable contact and a lateral direction perpendicular to the longitudinal direction, The elastic portion has a maximum width portion whose length in the short side direction is maximum, The breaker of claim 1 , wherein the thin portion is formed in the widest portion.

5. 2. The breaker according to claim 1, wherein, in a plan view seen from the thickness direction of the movable piece, the center of area of ​​the thin portion is located closer to the movable contact than the center of area of ​​the thermally responsive element.

6. the thin-walled portion is formed by providing a hole in the movable piece, The breaker according to claim 1 , wherein the hole is formed in a tapered shape such that an area in a plan view seen from the thickness direction increases toward the thermally responsive element.

7. the movable piece has a longitudinal direction in which the elastic portion extends toward the movable contact and a lateral direction perpendicular to the longitudinal direction, The breaker according to claim 1 , wherein the thin-walled portion is formed in an elliptical shape having a major axis in the longitudinal direction.

8. the movable piece has a longitudinal direction in which the elastic portion extends toward the movable contact and a lateral direction perpendicular to the longitudinal direction, 2. The breaker according to claim 1, wherein in the elastic portion, a difference W1A-W1B between a width W1A in the short side direction of a first portion in which the thin portion is formed and a width W1B in the short side direction of the thin portion is greater than or equal to a width W2 in the short side direction of a second portion in which the movable contact is formed.

9. 2. The breaker according to claim 1, wherein the elastic portion has a thickness of 0.05 to 0.2 mm.

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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