Circuit breaker and secondary battery pack provided with same

Abstract

Provided is a circuit breaker which can be used in a high-capacity secondary battery pack, has high thermal detection sensitivity, and can be arranged in a space-saving manner. A circuit breaker (1) is provided with a fixed piece (2) having a fixed contact (21), a movable piece (3) having a movable contact (31) and pressing the movable contact (31) against the fixed contact (21) to bring the fixed contact (21) into contact with the movable contact (31), a thermal response element (4) operating the movable piece (3) so that the movable contact (31) is separated from the fixed contact (21), a housing (6), and a flat-plate-shaped contact (8). The housing (6) accommodates the thermal response element (4), and the tabulate joint (8) is electrically connected to the fixed piece (2) or the movable piece (3). The joint (8) has a protruding section (81) which is welded to the fixed piece (2) on the surface of the fixed piece (2) opposite to the surface on which the fixed contact (21) is provided, and which protrudes further outward than the housing in plan view.

Description

Technical Field

[0001] The present invention relates to a circuit breaker for interrupting current when the ambient temperature rises abnormally, and a secondary battery pack having the circuit breaker. Background Art

[0002] In the past, secondary battery packs were equipped with temperature protection elements (circuit breakers) that blocked current when the ambient temperature rose abnormally. In particular, when charging in abnormal conditions such as overcharging, the temperature becomes very high, which may cause dangers such as fire. For this reason, secondary battery packs with built-in lithium-ion batteries are usually equipped with temperature protection elements such as the above-mentioned circuit breakers to ensure safety.

[0003] Furthermore, in a secondary battery pack equipped with a plurality of secondary battery cells, the circuit breaker is connected in series with the secondary battery cells between the battery terminals of the plurality of secondary battery cells. When the circuit breaker is connected in series with the secondary battery cells, the battery terminals and the circuit breaker terminals are not directly welded, but are generally welded via a thin metal plate called a joint. That is, aluminum frequently used in the battery terminals of lithium-ion batteries and copper frequently used in the terminals of circuit breakers are difficult to weld directly, and a joint made of nickel is required, which can be stably welded to both.

[0004] However, in this type of connector, welding points welded to the battery terminals or the terminals of the circuit breaker are usually arranged at both ends of the flat connector, and the current flows in the planar direction of the connector. However, nickel, as a conductive metal, is a material with relatively high resistance. When the current flows in the planar direction of the nickel connector, its resistance value cannot be ignored. In recent years, the current capacity of each battery cell in secondary battery packs has continued to increase, and there is a demand to reduce the overall resistance value of the assembly including the connector and the circuit breaker as much as possible and to increase the current capacity. Therefore, a circuit breaker has been developed, the terminals of which are made of a nickel and copper coating material, and the terminals of the circuit breaker can be directly welded to the battery terminals (for example, refer to patent document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent document 1: Japanese Patent Application Publication No. 2018-206732. Summary of the invention

[0008] Problem that the invention aims to solve

[0009] However, the cladding material is manufactured by rolling and joining different types of metals, which makes the manufacturing process complicated and may increase the component cost. On the other hand, the general nickel joint is cheap, so it is more preferable to use such a general joint to achieve high capacity.

[0010] Furthermore, when the battery terminals and the circuit breaker terminals are connected side by side horizontally via connectors, the circuit breaker and the battery terminals are separated, and the thermal conductivity of nickel connectors is lower than that of copper, etc. Therefore, the temperature of the secondary battery cell is difficult to be transmitted to the circuit breaker, and the thermal detection sensitivity of the circuit breaker may be reduced.

[0011] Furthermore, in recent years, secondary battery cells have been miniaturized and diversified. In some secondary battery cells, the interval between the positive terminal and the negative terminal is small. In such secondary battery cells, it is sometimes difficult to arrange the circuit breaker and one of the battery terminals horizontally side by side. For this reason, there is a demand for the circuit breaker to be arranged in a space-saving manner.

[0012] The present invention is made to solve the above-mentioned problems, and an object of the present invention is to provide a circuit breaker and a secondary battery pack using the circuit breaker, wherein the circuit breaker can be used for a high-capacity secondary battery pack, has high heat detection sensitivity and can be arranged in a space-saving manner.

[0013] Solutions to the problem

[0014] In order to achieve the above-mentioned purpose, the circuit breaker of the present invention is characterized in that it includes a fixed piece, a movable piece, a thermal response element, a shell and a flat-plate-shaped connector, wherein the fixed piece has a fixed contact, the movable piece has a movable contact and the movable contact is pressed onto the fixed contact to make the two contact, the thermal response element deforms as the temperature changes, thereby causing the movable piece to operate so that the movable contact is away from the fixed contact, the shell accommodates the thermal response element, and the flat-plate-shaped connector is electrically connected to the fixed piece, wherein the connector has a protrusion welded to the fixed piece on a surface of the fixed piece on the opposite side to the surface on which the fixed contact is provided, and protrudes outward more than the shell when viewed from above.

[0015] In the above circuit breaker, the housing includes a resin base and a resin cover, the resin base embeds a part of the fixing piece and accommodates the thermal response element, and the resin cover is welded to the resin base.

[0016] The resin base preferably has an opening for spot welding the joint and the fixing plate.

[0017] The circuit breaker of the present invention comprises a fixed piece, a movable piece, a thermal response element, a housing and a flat-plate-shaped connector, wherein the fixed piece has a fixed contact, the movable piece has a movable contact and the movable contact is pressed against the fixed contact to make the two contact, the thermal response element deforms as the temperature changes, thereby causing the movable piece to operate so that the movable contact moves away from the fixed contact, the housing accommodates the thermal response element, and the flat-plate-shaped connector is electrically connected to the movable piece, wherein the connector may have a protrusion welded to the movable piece on a surface of the movable piece on the opposite side to the surface on which the movable contact is provided and protruding outwardly more than the housing when viewed from above.

[0018] The circuit breaker of the present invention comprises a fixed piece, a movable piece, a thermal response element, a housing, a flat plate-shaped first connector and a flat plate-shaped second connector, wherein the fixed piece has a fixed contact, the movable piece has a movable contact, and the movable contact is pressed against the fixed contact to make the two contact, the thermal response element deforms as the temperature changes, thereby causing the movable piece to operate so that the movable contact moves away from the fixed contact, the housing accommodates the thermal response element, the flat plate-shaped first connector is electrically connected to the fixed piece, and the flat plate-shaped second connector is electrically connected to the movable piece, wherein the first connector may have a first protrusion welded to the fixed piece on a surface of the fixed piece opposite to a surface on which the fixed contact is provided and protruding outwardly more than the housing in a plan view, and the second connector may have a second protrusion welded to the movable piece on a surface of the movable piece opposite to a surface on which the movable contact is provided and protruding outwardly more than the housing in a plan view.

[0019] In the above circuit breaker, the first protrusion and the second protrusion are preferably formed so as not to overlap each other in a plan view.

[0020] The above-mentioned circuit breaker is preferably used for a secondary battery pack.

[0021] Effects of the Invention

[0022] According to the present invention, the flat-plate-shaped connector is electrically connected to the fixed plate (or movable plate) on a plane, so when it is engaged with the electrode terminal of the secondary battery cell, the current will flow between the electrode terminal and the circuit breaker along the thickness direction of the connector. Therefore, even if the connector is made of a material with a relatively high resistance, such as nickel, the resistance value between the secondary battery cell and the circuit breaker can be reduced, and it can be used for a high-capacity secondary battery pack. In addition, the distance between the secondary battery cell and the circuit breaker becomes shorter, so that the temperature of the secondary battery cell is easily transmitted to the circuit breaker, which can improve the thermal detection sensitivity. Furthermore, the circuit breaker is configured to overlap with the electrode of the secondary battery cell, so that it can be configured in a space-saving manner. Brief description of the attached figure

[0023] Figure 1 It is a view showing a schematic structure of a secondary battery pack using the circuit breaker according to the first embodiment of the present invention.

[0024] Figure 2 (a) is a plan view showing an example of the structure of a fixing piece, a housing, and a joint in the circuit breaker, (b) is a cross-sectional view showing the circuit breaker in a normal energized state, and (c) is a cross-sectional view showing the circuit breaker in an abnormal state.

[0025] Figure 3 (a) to (c) are views showing the steps of mounting the circuit breaker on a secondary battery pack.

[0026] Figure 4 (a) is a cross-sectional view of a circuit breaker according to a second embodiment of the present invention, and (b) is a plan view showing a configuration example of a case and a joint in the circuit breaker.

[0027] Figure 5 (a) is a cross-sectional view of a circuit breaker according to a third embodiment of the present invention, and (b) is a plan view showing a configuration example of a case and a joint in the circuit breaker.

[0028] Explanation of symbols

[0029] 1 circuit breaker, 2 fixed plate, 21 fixed contact, 3 movable plate, 31 movable contact, 4 thermal response element, 6 housing, 61 resin base, 62 resin cover, 65 opening (point opening), 8 joint, 8A first joint, 8B second joint, 81 protrusion, 81A first protrusion, 81B second protrusion DETAILED DESCRIPTION

[0030] Hereinafter, a circuit breaker and a secondary battery pack using the circuit breaker according to a first embodiment of the present invention will be described with reference to the accompanying drawings. As the secondary battery pack 10 of this embodiment, for example, a high-power battery for electric tools, such as Figure 1 As shown, the secondary battery pack 10 includes a plurality of secondary battery cells 11 connected in series. The secondary battery pack 10 also includes a plurality of temperature protection elements (circuit breakers 1 ) which are provided for each of the plurality of secondary battery cells 11 and interrupt current according to temperature changes.

[0031] The secondary battery cell 11 has a positive terminal 12 and a negative terminal 13 provided at the upper end of the plate-shaped battery cell body, and the circuit breaker 1 is connected to one of the terminals via a connector 8 described later. The positive terminal 12 and the negative terminal 13 of the adjacent secondary battery cells 11 are connected via an arm terminal 14 derived from the circuit breaker 1. The positive terminal 12 and the negative terminal 13 at both ends of the series circuit are connected to the circuit substrate (not shown) via an arm side connector 15 or directly. In addition, the figure shows a structure in which three secondary battery cells 11 and three circuit breakers 1 are used correspondingly, but the number of secondary battery cells 11 and circuit breakers 1 is not limited to the figure, and the number of each may be different.

[0032] like Figure 2 As shown in (a) to (c), the circuit breaker 1 has a current blocking unit that blocks the current according to temperature changes. The current blocking unit is mainly composed of a fixed plate 2 having a fixed contact 21, a movable plate 3 having a movable contact 31 at the front end, a thermal response element 4 that deforms with temperature changes, and a PTC (Positive Temperature Coefficient) thermistor 5. In addition, the circuit breaker 1 also has a housing 6 for accommodating the above-mentioned current blocking unit, a reinforcement component 7 installed on the housing 6, and a connector 8 provided on the outside of the housing 6 and electrically connected to the fixed plate 2. In addition, Figure 2 (a) shows only the fixing plate 2 , the housing 6 (resin base 61 ) and the joint 8 in the above structure.

[0033] As the fixed sheet 2, for example, a metal plate with copper as the main component is formed by stamping, and a part of it is embedded in the housing 6 by insert molding. The fixed contact 21 is formed at a position facing the movable contact 31 by coating, electroplating, riveting or coating with a material with good conductivity such as silver, copper-silver alloy, gold-silver alloy, etc. A terminal 22 electrically connected to the external circuit is formed on one end side of the fixed sheet 2, and the terminal 22 protrudes outward from the end edge of the housing 6. In addition, in this embodiment, the terminal 22 protrudes outside the housing 6 to facilitate the embedding and molding of the fixed sheet 2, but the conduction with the fixed sheet 2 is carried out via the connector 8, so that the terminal 22 is not electrically connected to the external circuit. In addition, a support portion 23 supporting the PTC thermistor 5 is formed on the other end side of the fixed sheet 2. A convex protrusion 24 is formed on the support portion 23 of the fixed sheet 2, and the PTC thermistor 5 is mounted and supported on the protrusion 24 provided on the support portion 23.

[0034] By stamping a plate-shaped metal material, the movable piece 3 is formed into an arm shape that is symmetrical with respect to the center line in the longitudinal direction. The material of the movable piece 3 is preferably a material with copper or the like as the main component, which is the same as that of the fixed piece 2. The movable contact 31 is formed of the same material as the fixed contact 21, and is joined near the free end constituting one end of the movable piece 3. A fixed portion 32 fixed to the housing 6 is formed on the portion of the movable piece 3 on the opposite side of the free end where the movable contact 31 is provided. Furthermore, an elastic portion 34 is formed between the movable contact 31 and the fixed portion 32. The movable piece 3 is further extended outward from the fixed portion 32, and the extended portion forms a terminal 33, which is electrically connected to an external circuit. With this structure, the elastic portion 34 of the movable piece 3 is elastically deformed, and the movable contact 31 formed at its free end is pressed against one side of the fixed contact 21 to make contact, and the fixed piece 2 and the movable piece 3 are in a state where electricity can be passed through (refer to Figure 2 (b)) In addition, although the present embodiment shows a structure in which the movable piece 3 and the terminal 33 are integrated, the movable piece 3 may be welded to a separate terminal 33, for example.

[0035] The thermal response element 4 is in an initial shape bent into an arc shape, and is formed by laminating thin plates with different thermal expansion coefficients. When the operating temperature is reached due to overheating, the bent shape of the thermal response element 4 will be reversely warped in a flash motion, and when the temperature is lower than the recovery temperature due to cooling, it will be restored to the bent shape. The initial shape of the thermal response element 4 is formed by stamping. There is no special limitation on the material and shape of the thermal response element 4, as long as the elastic part 34 of the movable piece 3 is pushed up by the reverse warping action of the thermal response element 4 at the desired temperature, and it can be restored to its original shape under the elastic force of the elastic part 34, but from the perspective of production performance and the efficiency of the reverse warping action, it is preferably a rectangular shape, and in order to effectively push up the elastic part 34 while taking into account miniaturization, it is preferably a rectangle close to a square. In addition, as the material of the thermal response element 4, for example, copper-nickel-manganese alloy or nickel-chromium-iron alloy is used on the high expansion side, and iron-nickel alloy is used on the low expansion side, and two materials with different thermal expansion coefficients composed of various alloys such as copper-nickel alloy, brass, and stainless steel are used in combination according to the required conditions.

[0036] The PTC thermistor 5 is arranged between the fixed sheet 2 and the thermal response element 4. In other words, the fixed sheet 2 is located directly below the thermal response element 4 with the PTC thermistor 5 sandwiched therebetween. Due to the reverse warping action of the thermal response element 4, when the energization of the fixed contact 21 and the movable contact 31 is blocked, the current flowing through the PTC thermistor 5 increases. As long as the PTC thermistor 5 is a positive characteristic thermistor that limits the current by increasing the resistance value as the temperature rises, the type can be selected according to the requirements of the operating current, operating temperature, recovery temperature, etc. As long as these characteristics are not damaged, there is no special limitation on its material and shape. 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 containing conductive particles such as carbon in a polymer can also be used.

[0037] The housing 6 is a roughly rectangular box-shaped component when viewed from above, and has a resin base 61 for accommodating the above-mentioned thermal response element 4 and PTC thermistor 5, and a resin cover 62 welded to the resin base 61. In the present embodiment, in the resin base 61 and the resin cover 62, a receiving recess 60 for accommodating the main components of the current interruption unit is formed on one side of the resin base 61. On the other hand, the resin cover 62 is a component with fewer receiving recesses and a smaller thickness. The resin base 61 and the resin cover 62 are formed of thermoplastic resin compositions such as flame-retardant polyamide, polyphenylene sulfide (PPS) with excellent heat resistance, liquid crystal polymer (LCP), and polybutylene terephthalate (PBT).

[0038] The resin base 61 is rectangular in plan view, and the terminal 22 is led out in the longitudinal direction. The resin base 61 holds the fixed sheet 2 at its bottom so that the outer side surface of the support portion 23 of the fixed sheet 2 (the surface opposite to the surface on which the fixed contact 21 is provided) is exposed to the outside. The portion of the fixed sheet 2 from the support portion 23 to the vicinity of the fixed contact 21 is buried in the resin base 61. The resin base 61 has a central opening 63 in which the PCT thermistor 5 is embedded, and a contact opening 64 in which the fixed contact 21 is exposed toward the movable contact 31 (especially, see Figure 2 (a)).

[0039] Furthermore, the resin base 61 has a plurality of circular spot openings 65 formed around the central opening 63 so that the fixing piece 2 is exposed on one side of the receiving recess 60. An electrode for spot welding is inserted into the spot opening 65, and another electrode is arranged outside the connector 8, and the fixing piece 2 and the connector 8 clamped by these electrodes are spot welded. The fixing piece 2 is embedded and fixed in the resin base 61, so that by welding the fixing piece 2 and the connector 8, the fixing piece 2, the connector 8 and the resin base 61 are formed as a unit. Furthermore, the outer side surface of the fixing piece 2 is exposed from the resin base 61, so that the fixing piece 2 and the connector 8 are in contact with each other on a plane. Furthermore, the circuit breaker 1 of this embodiment is assembled by arranging the PTC thermistor 5, the thermal response element 4 and the movable piece 3 in the above-mentioned unit and covering the resin cover 62 in which the reinforcing component 7 is embedded.

[0040] The reinforcing member 7 is formed by stamping a metal plate mainly composed of copper or stainless steel. The reinforcing member 7 is formed in a rectangular flat plate shape to improve the rigidity and strength of the housing 6 as a frame body and to contribute to the miniaturization of the circuit breaker 1. In addition, in the present embodiment, the reinforcing member 7 is insert-molded in the resin cover 62, and one end thereof protrudes outside the housing 6.

[0041] The connector 8 is a metal that can be stably welded to aluminum constituting the electrode terminal of the secondary battery 11 and copper constituting the fixing plate 2, for example, a rectangular thin plate made of nickel or a nickel alloy. The connector 8 of this embodiment is a planar rectangular shape, the length of the connector 8 in the short side direction is longer than the resin base 61, and has a protrusion 81 that is larger than the resin base 61 (housing 6) in a top view. The protrusion 81 is provided with a spot welding portion 82 described later.

[0042] Figure 2 (b) shows the state of the circuit breaker 1 when the normal power path is working. In this conductive state, the thermal response element 4 maintains the initial shape (before reverse warping), the fixed contact 21 is in contact with the movable contact 31, and the two terminals 22 and 33 of the circuit breaker 1 are conductive through the elastic portion 34 of the movable piece 3. The elastic portion 34 of the movable piece 3 is in contact with the thermal response element 4, and the movable piece 3, the thermal response element 4, the PTC thermistor 5 and the fixed piece 2 are conductive as a circuit. On the other hand, the resistance of the PTC thermistor 5 is very large compared to the resistance of the movable piece 3, so the current flowing through the PTC thermistor 5 is low to a level that can be basically ignored compared to the amount flowing through the fixed contact 21 and the movable contact 31.

[0043] Figure 2(c) shows the state of the circuit breaker 1 when an abnormality occurs. When the circuit breaker 1 is in a high temperature state due to the abnormality, the thermal response element 4 that has reached the operating temperature is reversely warped, the elastic portion 34 of the movable piece 3 is pushed up, and the fixed contact 21 is separated from the movable contact 31. At this time, the flow path of the current flowing between the fixed contact 21 and the movable contact 31 is blocked, and a small leakage current flows through the thermal response element 4 and the PTC thermistor 5. As long as this leakage current flows, the PTC thermistor 5 will continue to generate heat, causing the thermal response element 4 to maintain a reverse warping state and increase the resistance value sharply, so that the current will hardly flow in the path between the fixed contact 21 and the movable contact 31.

[0044] Secondly, refer to Figure 3 (a) to (c) illustrate the process of installing the circuit breaker 1 in the secondary battery unit 11. As described above, the circuit breaker 1 of this embodiment is connected to the terminal 8 that is in contact with the fixed piece 2 on the same plane. In addition, here, the movable piece 3 (refer to Figure 2 (b) The arm terminal 14 is connected to the movable piece 3. The arm terminal 14 may be a terminal extending from the terminal 33 of the movable piece 3, or may be a terminal to which another terminal is welded. Figure 3 As shown in (a), a secondary battery unit 11 and a circuit breaker 1 having a connector 8 and an arm terminal 14 are prepared.

[0045] Then, if Figure 3 As shown in (b), the circuit breaker 1 is welded to one terminal (here, the positive terminal 12) of the secondary battery cell 11. At this time, the protrusion 81 of the connector 8 protrudes outward, so by setting the protrusion 81 as the spot welding portion 82, the connector 8 and the positive terminal 12 can be easily welded and fixed. The connector 8 is electrically connected to the fixing plate 2, thereby the circuit breaker 1 is electrically connected to the secondary battery cell 11. Then, as shown in FIG. Figure 3 As shown in (c), an arm-side connector 15 led out from a circuit board (not shown) is soldered to the arm terminal 14 .

[0046] In the circuit breaker 1 of the present embodiment, the flat-plate-shaped connector 8 is electrically connected to the fixing plate 2 on the same plane, so that the current flows in the thickness direction of the connector 8 between the positive terminal 12 of the secondary battery cell 11 and the fixing plate 2 of the circuit breaker 1. Therefore, compared with the case where the current flows in the plane direction of the connector 8, the flow distance of the current is short, and even if the connector 8 is made of a material with a relatively large resistance such as nickel, the resistance value between the secondary battery cell 11 and the circuit breaker 1 can be reduced, and it can be used for a high-capacity secondary battery pack. In addition, in the present embodiment, the distance between the secondary battery cell 11 and the circuit breaker 1 is shortened, so that the temperature of the secondary battery cell 11 is easily transmitted to the circuit breaker 1, and the heat detection sensitivity can be improved. Furthermore, in the present embodiment, the circuit breaker 1 is configured to overlap with the electrode of the secondary battery cell 11, so that the circuit breaker 1 can be configured in a space-saving manner compared with the case where the electrodes of the secondary battery cell 11 are configured side by side horizontally.

[0047] Secondly, refer to Figure 4 (a) and (b) illustrate a circuit breaker 1 according to a second embodiment of the present invention. In the above embodiment, the connector 8 is provided on the side of the fixed piece 2, but in this embodiment, the connector 8 is provided on the side of the movable piece 3. The resin cover 62 of this embodiment is formed so that the reinforcing member 7 is exposed to the outside. In addition, the resin base 61 is shown as having a bottom and the support portion 23 of the fixed piece 2 is not exposed to the outside in the example, but the support portion 23 of the fixed piece 2 may also be exposed to the outside as in the above first embodiment.

[0048] The reinforcing component 7 is made of the same material as the movable piece 3, and is in surface contact with the movable piece 3, so that it is electrically connected to the movable piece 3 as a whole. Furthermore, in this embodiment, the reinforcing component 7 and the connector 8 that are in surface contact with the movable piece 3 are welded to each other so as to contact each other on a plane. In addition, as described above, the reinforcing component 7 is electrically connected to the movable piece 3 as a whole in structure, so the reinforcing component 7 is essentially a part of the movable piece 3, and the connector 8 is indirectly welded to the movable piece 3. In this embodiment, the connector 8 is welded to the reinforcing component 7 (movable piece 3), so the movable piece 3 is not provided with the terminal 33 as in the first embodiment described above, and the terminal 22 of the fixed piece 2 is electrically connected to the external circuit.

[0049] In this embodiment, the connector 8 also has a protruding portion 81 protruding outside the resin cover 62 (housing 6), so the protruding portion 81 forms a spot welding portion 82, and the circuit breaker 1 can be welded in a manner overlapping with the electrode of the secondary battery cell 11, as in the above embodiment. In addition, the circuit breaker 1 of this embodiment also has the same effect as the above embodiment.

[0050] Secondly, refer to Figure 5(a) and (b) are used to explain the circuit breaker 1 of the third embodiment of the present invention. In this embodiment, a first connector 8A is provided on the side of the fixed piece 2, and a second connector 8B is also provided on the side of the movable piece 3. The resin base 61 of this embodiment is configured in the same manner as the first embodiment, and the resin cover 62 is configured in the same manner as the second embodiment. In addition, in this embodiment, as in the first embodiment, the conduction with the fixed piece 2 is performed via the connector 8, so the terminal 22 is not electrically connected to the external circuit.

[0051] In this embodiment, the first connector 8A has a first protrusion 81A protruding outward from the housing 6, and the second connector 2B has a second protrusion 81B in the same manner as described above. Figure 5 As shown in (b), the first protrusion 81A and the second protrusion 81B are formed so as not to overlap each other in a plan view. The first protrusion 81A and the second protrusion 81B form spot welding portions 82A and 82B, respectively.

[0052] According to the present embodiment, for example, when the electrode terminal of the secondary battery cell 11 is to be connected to the fixed piece 2 side of the circuit breaker 1, the first protrusion 81A can be set as the spot welding portion 82A, 82B, and when the movable piece 3 side of the circuit breaker 1 is to be connected, the second protrusion 81B can be set as the spot welding portion 82B. According to the present embodiment, any terminal side of the circuit breaker 1 can be appropriately selected to be welded to the electrode terminal of the secondary battery cell 11.

[0053] The present invention is not limited to the above-mentioned embodiment and modified examples, and various modifications can be made to the circuit breaker 1 as long as the connector 8 is in contact with the fixed piece 2 or the movable piece 3 on the same plane 3 and the connector 8 can be welded at a portion protruding outward from the housing 6. As described above, the circuit breaker 1 of the above-mentioned embodiment and modified examples is assumed to be used in the secondary battery pack 10, but it can be used in all electrical equipment that can be welded via the connector 8.

Claims

1. A circuit breaker, characterized in that: The circuit breaker comprises a fixed piece, a movable piece, a thermal response element, a housing and a flat plate-shaped connector. The fixing piece has a fixing contact, The movable piece has a movable contact, and the movable contact is pressed against the fixed contact to make the two contact, The thermal response element deforms as the temperature changes, thereby causing the movable piece to operate so that the movable contact moves away from the fixed contact. The housing accommodates the thermal response element. The flat plate-shaped connector is electrically connected to the fixing plate. The connector has a protrusion that is welded to the fixing plate on a surface of the fixing plate opposite to a surface on which the fixed contact is provided and that protrudes outwardly from the housing in a plan view.

2. The circuit breaker according to claim 1, wherein: The housing includes a resin base and a resin cover. A portion of the fixing plate is embedded in the resin base to accommodate the thermal response element. The resin cover is welded to the resin base. The resin base has an opening for spot welding the joint and the fixing plate.

3. A circuit breaker, characterized in that: The circuit breaker comprises a fixed piece, a movable piece, a thermal response element, a housing and a flat plate-shaped connector. The fixing piece has a fixing contact, The movable piece has a movable contact, and the movable contact is pressed against the fixed contact to make the two contact, The thermal response element deforms as the temperature changes, thereby causing the movable piece to operate so that the movable contact moves away from the fixed contact. The housing accommodates the thermal response element. The flat plate-shaped connector is electrically connected to the movable piece. The connector has a protrusion that is welded to the movable piece on a surface of the movable piece opposite to a surface on which the movable contact is provided and that protrudes outwardly from the housing in a plan view.

4. A circuit breaker, characterized in that: The circuit breaker comprises a fixed piece, a movable piece, a thermal response element, a housing, a first flat-plate joint and a second flat-plate joint. The fixing piece has a fixing contact, The movable piece has a movable contact, and the movable contact is pressed against the fixed contact to make the two contact, The thermal response element deforms as the temperature changes, thereby causing the movable piece to operate so that the movable contact moves away from the fixed contact. The housing accommodates the thermal response element. The flat first connector is electrically connected to the fixing plate. The second flat-plate connector is electrically connected to the movable piece. The first connector has a first protrusion welded to the fixing plate on a surface of the fixing plate opposite to a surface on which the fixing contact is provided and protruding outwardly from the housing when viewed from above, The second terminal has a second protrusion that is welded to the movable piece on a surface of the movable piece opposite to a surface on which the movable contact is provided and that protrudes outward from the housing in a plan view.

5. The circuit breaker according to claim 4, wherein: The first protrusion and the second protrusion are formed so as not to overlap each other in a plan view.

6. A secondary battery pack, characterized in that: This secondary battery pack uses the circuit breaker according to any one of claims 1 to 5.

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