Protection element

Abstract

To provide a protection element capable of suppressing the occurrence of a tracking phenomenon.SOLUTION: A protection element 11 includes a fuse element 20, a first terminal 22 and a second terminal 23 connected to both ends of the fuse element 20 in the current-carrying direction, and a case that accommodates parts of the first terminal 22 and the second terminal 23, and the fuse element 20. Each of the first terminal 22 and the second terminal 23 includes a connection portion 70 that is connected with the fuse element 20 in an overlapping area SA where the parts that face each other in the current-carrying direction are positioned inside both ends of the fuse element 20 in a plan view and overlap with the fuse element 20, and a hollow portion 71 is formed therein.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a protection element. [Background technology]

[0002] Conventionally, there are fuse elements that generate heat and melt to cut off the current path when a current exceeding the rated value flows through the current path. Protective devices (fuse elements) equipped with fuse elements are used in a wide range of fields, from home appliances to electric vehicles.

[0003] For example, lithium-ion batteries are used in a wide range of applications, from mobile devices to electric vehicles (EVs) and storage batteries, and their capacity is increasing. As the capacity of lithium-ion batteries increases, the risk of them catching fire or other problems increases. For this reason, in order to ensure product safety, a method is generally adopted in which a protection circuit using a protection element is incorporated.

[0004] For example, Patent Document 1 discloses a protection element including an insulating substrate and a fusible conductor mounted on the surface of the insulating substrate. The inside of this protection element is protected by covering the insulating substrate with a cover member. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-53260 Summary of the Invention [Problem to be solved by the invention]

[0006] Increasing the rated voltage requires improving insulation after interruption. As the voltage increases, sparks (discharges) become more likely to occur after the fuse element has interrupted. If these sparks occur repeatedly, soot from the fuse element will adhere to the insulating substrate and carbonize. As this carbonization progresses, a carbonized conductive path (track) is formed, which can cause a short circuit between the electrodes (terminals), potentially resulting in heat generation and fire (tracking). Tracking can hinder the fuse element from interrupting or melting, increasing the risk of it not cutting. To increase the current capacity, the volume of the fuse element can be increased or the thickness of the conductor on the base substrate can be increased. As the fuse element becomes thicker, the melting shock (explosion) when the fuse element is cut off becomes more severe, and the insulation after cutting off deteriorates. This makes it more likely that tracking will occur after cutting off, making it difficult to cut off the circuit when an abnormal current flows.

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a protection element that can suppress the occurrence of the tracking phenomenon. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following means.

[0009] [1] A protective element comprising: a fuse element; a first terminal and a second terminal connected to both ends of the fuse element in the current-carrying direction; and a case that houses a portion of the first terminal and a portion of the second terminal, and the fuse element, wherein each of the first terminal and the second terminal has a connection portion that connects to the fuse element in an overlapping region where the portions that face each other in the current-carrying direction are positioned inside the both ends of the fuse element in a planar view and overlap with the fuse element, and a hollow portion is formed therein.

[0010] [2] The protection element according to [1], wherein the hollow portion is formed to include a recess that is recessed outward in the current flow direction from the portions where the first terminal and the second terminal face each other in the current flow direction when viewed in the plane.

[0011] [3] The protection element according to [2], wherein the recess is formed so that the distances from a center position, which is the center between the first terminal and the second terminal facing each other in the current-carrying direction in the plan view and is the center in a width direction perpendicular to the current-carrying direction, to the facing portions are the same.

[0012] [4] The protection element according to [2], wherein the recess is formed in a V-shape that is convex outward in the current-carrying direction in the plan view.

[0013] [5] The protection element according to [2], wherein the recess is formed in an arc shape that curves outward in the current-carrying direction in the plan view.

[0014] [6] The protection element according to [2], wherein the recess is formed in a U-shape recessed outward in the current-carrying direction in the plan view.

[0015] [7] The protection element according to [1], wherein the hollow portion is formed to include a plurality of through holes that open in the overlapping region in the plan view.

[0016] [8] The protection element described in [7], wherein the number of through holes is greater in the portions closer to the center position, which is the center between the first terminal and the second terminal facing each other in the current-carrying direction in the planar view and the center in the width direction perpendicular to the current-carrying direction, from the opposing portions.

[0017] [9] The protection element according to any one of [1] to [8], further comprising: an insulating substrate housed in the case and arranged between the first terminal and the second terminal facing each other in the current-carrying direction in the planar view; and a heating resistor provided on the insulating substrate. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a protection element that can suppress the occurrence of a tracking phenomenon. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a circuit diagram of a battery pack according to a first embodiment. [Figure 2] FIG. 2 is a plan view showing a protection element according to the first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2. [Figure 5] 1 is a plan view showing a state in which the case is removed from the protection element according to the first embodiment. [Figure 6] FIG. 2 is a plan view showing the fuse element, the first terminal, and the second terminal according to the first embodiment. [Figure 7] 3 is a plan view showing hollow portions formed in each of the first terminal and the second terminal according to the first embodiment. FIG. [Figure 8] FIG. 2 is a perspective view showing an example of a fuse element according to the first embodiment. [Figure 9] FIG. 2 is a diagram showing an example of a circuit diagram of the battery pack according to the first embodiment, illustrating a state before a thermostat serving as a heat-sensitive element is heated. [Figure 10] FIG. 2 is a diagram showing the thermostat when heated and the fuse element is melted. [Figure 11] FIG. 2 is a diagram showing an example of a circuit diagram of the battery pack according to the first embodiment, in which a protection IC and a switch are mounted. [Figure 12] FIG. 10 is a plan view showing a protection element according to a comparative example. [Figure 13] FIG. 10 is a plan view showing the protective element according to the comparative example when it is cut off (explosion). [Figure 14] FIG. 10 is a plan view showing a first modified example of the hollow portion. [Figure 15]FIG. 10 is a plan view showing a second modified example of the hollow portion. [Figure 16] FIG. 10 is a plan view showing a third modified example of the hollow portion. [Figure 17] FIG. 10 is a plan view showing a fourth modified example of the hollow portion. [Figure 18] FIG. 10 is a cross-sectional view of a protection element according to a second embodiment. [Figure 19] FIG. 10 is a plan view showing a protection element according to a second embodiment. [Figure 20] FIG. 10 is a cross-sectional view of a protection element according to a third embodiment. [Figure 21] FIG. 10 is a plan view showing a protection element according to a third embodiment. [Figure 22] FIG. 10 is a cross-sectional view of a protection element according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the effects of the present invention.

[0021] (First embodiment) First, a battery pack and a protection circuit including a protection element according to one embodiment of the present invention will be described with reference to Fig. 1. The battery pack according to this embodiment constitutes a part of a high-voltage, high-current (100V / 100A or more) electric circuit that uses, for example, a lithium-ion secondary battery. The battery pack is mounted, for example, in an electric vehicle (EV).

[0022] As shown in FIG. 1, the battery pack 10 includes, for example, a battery stack 15 consisting of a plurality of lithium-ion secondary battery cells 15a (see FIG. 9), a protection element 11 connected in series with the battery stack 15, and a thermal sensitive element 12 that controls the operation of the protection element 11.

[0023] The protection element 11 cuts off the charge / discharge path of the battery stack 15 when an abnormality occurs in the battery pack 10. The electrical characteristics of the heat-sensitive element 12, such as on / off conduction, resistance value, and output voltage, fluctuate due to heat. The heat-sensitive element 12 activates the protection element 11 when heated to a temperature above a predetermined temperature. The operation of the protection element 11 in the battery pack 10 is controlled according to the fluctuations in the electrical characteristics of the heat-sensitive element 12.

[0024] The battery stack 15 includes battery cells 15a (see FIG. 9) that require control to protect against overvoltage, overcurrent, and the like. The battery cells 15a are connected in series and / or parallel. The battery stack 15 is detachably connected to a charging device 13 via a positive terminal 10a and a negative terminal 10b of the battery pack 10. A charging voltage from the charging device 13 is applied to the battery stack 15 via the positive terminal 10a and the negative terminal 10b of the battery pack 10. The battery pack 10 charged by the charging device 13 can operate an electronic device by connecting the positive terminal 10a and the negative terminal 10b to the electronic device.

[0025] The battery pack 10 includes a charge / discharge control circuit 16 that controls charging and discharging of the battery stack 15. The charge / discharge control circuit 16 includes two current control elements 17 and 18 connected in series to a current path that flows from the battery stack 15 to the charging device 13, and a control unit 19 that controls the operation of these current control elements 17 and 18.

[0026] The current control elements 17 and 18 are configured, for example, with field effect transistors (hereinafter also referred to as "FETs"). The current control elements 17 and 18 control the conduction and interruption of the current path of the battery stack 15 in the charge direction and / or discharge direction by controlling the gate voltage with the control unit 19. The control unit 19 operates by receiving power supply from the charging device 13. The control unit 19 determines whether the battery stack 15 is over-discharged or over-charged based on the detection result of a detection circuit (not shown) that detects the voltage of each battery cell 15a. When the control unit 19 determines that the battery stack 15 is over-discharged or over-charged, it controls the operation of the current control elements 17 and 18 to interrupt the current path.

[0027] (protective element) The protection element 11 is connected, for example, on a charge / discharge current path between the battery stack 15 and the charge / discharge control circuit 16. The operation of the protection element 11 is controlled by a heat-sensitive element 12. Referring also to FIGS. 2 to 5 , the protection element 11 includes a fuse element 20, a first terminal 22 and a second terminal 23 connected to both ends of the fuse element 20 in the current-carrying direction, a case 60 that houses the fuse element 20 and parts of the first terminal 22 and the second terminal 23, an insulating substrate 26 that is disposed between the first terminal 22 and the second terminal 23 that face each other in the current-carrying direction in a plan view and that is housed in the case 60, and a heating resistor 24 provided on the insulating substrate 26.

[0028] Specifically, the protection element 11 includes an insulating substrate 26, first and second terminals 22 and 23 functioning as fuse terminals, a third terminal 25 functioning as a heater terminal, a heating resistor 24 formed on the surface of the insulating substrate 26, an insulating layer 27 covering the heating resistor 24, a heating element lead electrode 21 laminated on the insulating layer 27 and connected to the heating resistor 24, a fuse element 20 mounted across the first terminal 22, the heating element lead electrode 21, and the second terminal 23 via fixing solder 28 (hereinafter also referred to as "fixing member 28"), an island electrode 33, and a case 60. The first and second terminals 22 and 23 are arranged spaced apart from each other in a predetermined direction.

[0029] In the following, an XYZ Cartesian coordinate system (three-dimensional Cartesian coordinate system) may be set appropriately in each drawing, and each configuration may be explained. The predetermined direction in which the first terminal 22 and the second terminal 23 are aligned is called the front-rear direction. The front-rear direction corresponds to the X-axis direction in each drawing. In the X-axis direction, the -X side is called the front side, and the +X side is called the rear side. Note that the front-rear direction is the direction connecting the first terminal 22 and the second terminal 23, and is also the direction in which electricity flows when the protection element 11 is in use, so it may also be called the current flow direction.

[0030] The direction in which the plate surfaces of the first terminal 22 and the second terminal 23 face is called the up-down direction. The up-down direction is a direction perpendicular to the front-rear direction and corresponds to the Z-axis direction in each drawing. In the up-down direction, the upper side corresponds to the +Z side, and the lower side corresponds to the -Z side.

[0031] The direction perpendicular to the front-rear direction and the up-down direction is called the left-right direction. The left-right direction corresponds to the Y-axis direction in each drawing. In the left-right direction, the left side corresponds to the -Y side, and the right side corresponds to the +Y side. Specifically, the -Y side is the left side when the protection element 11 is viewed from the rear (+X side), and the +Y side is the right side when the protection element 11 is viewed from the rear. The left-right direction may also be referred to as the width direction. In this case, for example, one side in the width direction corresponds to the -Y side, and the other side in the width direction corresponds to the +Y side.

[0032] In this embodiment, the terms "front side," "rear side," "upper side," "lower side," "left side," and "right side" are convenient names for clearly explaining the relative positional relationships of each component, and the actual positional relationships may be other than those indicated by these names.

[0033] The first and second terminals 22, 23 are terminals connected to the charge / discharge path of the battery cell 15a. The first and second terminals 22, 23 are each formed in a plate shape extending in a plane direction (XY plane direction) perpendicular to the up-down direction. Specifically, the first and second terminals 22, 23 are formed in a substantially rectangular plate shape.

[0034] The rear end (+X end) of the first terminal 22 is connected to the front end (-X end) of the fuse element 20. The front end of the first terminal 22 is exposed to the outside of the protection element 11 from the front side of the protection element 11. The front end of the second terminal 23 is connected to the rear end of the fuse element 20. The rear end of the second terminal 23 is exposed to the outside of the protection element 11 from the rear side of the protection element 11.

[0035] 1, the heating resistor 24 is connected to a third terminal 25. The heating resistor 24 is connected to the heat-sensitive element 12 via the third terminal 25. The heating resistor 24 is connected to the fuse element 20 and the charge / discharge path of the battery stack 15 by electrically connecting the heating element lead electrode 21 to the fuse element 20.

[0036] The insulating substrate 26 is formed of an insulating material such as alumina, glass ceramics, mullite, or zirconia. Referring to FIGS. 3 to 5, the insulating substrate 26 is formed, for example, in a substantially rectangular shape. The insulating substrate 26 may also be formed of a material used for printed wiring boards, such as a glass epoxy board or a phenolic board. For example, the configuration of the insulating substrate 26 can be changed according to design specifications.

[0037] First and second terminals 22, 23 are formed on both opposing ends of insulating substrate 26 (specifically, the front end and rear end of insulating substrate 26). First and second terminals 22, 23 are formed of conductive patterns of Ag, Cu, or the like. First and second terminals 22, 23 are connected to connection electrodes provided on an external circuit board on which protection element 11 is mounted. As a result, fuse element 20 is incorporated into part of a current path formed on the external circuit board.

[0038] The heating resistor 24 is a conductive member with a relatively high resistance that generates heat when current is passed through it. The heating resistor 24 is made of, for example, nichrome, W, Mo, Ru, or a material containing any of these. The heating resistor 24 can be formed by mixing a powder of these alloys, compositions, or compounds with a resin binder or the like to form a paste, which is then patterned on the insulating substrate 26 using a screen printing technique and then fired.

[0039] The heating resistor 24 is thermally connected to the fuse element 20 by being superimposed thereon. When the heating resistor 24 generates heat due to the passage of current, it melts the fuse element 20. One end of the heating resistor 24 is connected to the heat-sensitive element 12, so that the current and heat generation of the heating resistor 24 are constantly limited. The amount of heat generated by the heating resistor 24 increases as the current increases due to the passage of current through the heat-sensitive element 12 or a decrease in electrical resistance. The increased amount of heat generated by the heating resistor 24 can melt the fuse element 20. The heating resistor 24 is also electrically connected to the fuse element 20.

[0040] The fuse element 20 is connected across the first terminal 22 and the second terminal 23 by fixing solder 28. The fuse element 20 is made of, for example, a metal plate-like member, a metal sheet-like member, or a metal foil. In the example shown in the figure, the fuse element 20 has a rectangular shape that is long in the front-to-rear direction when viewed from the top-to-bottom direction. During normal use, the fuse element 20 provides electrical continuity between the first and second terminals 22, 23, and constitutes part of the current path of the external circuit in which the protection device 11 is incorporated.

[0041] The fuse element 20 melts due to self-heating (Joule heat) caused by a current exceeding its rated value. The fuse element 20 melts when heated to a predetermined temperature or higher by the heating resistor 24. The fuse element 20 melts due to the heat generated by the heating resistor 24, and disconnects the first and second terminals 22, 23.

[0042] The fuse element 20 has a predetermined rated current value and melts quickly due to heat generated by the heating resistor 24 or self-heating when a current exceeding the rated current value is applied. The fuse element 20 preferably contains one selected from nickel, tin, and lead as its main component. The term "main component" refers to a component that accounts for 50 wt% or more of the total mass of the material.

[0043] 8, the fuse element 20 may have a laminated structure in which a low-melting-point metal layer 41 and a high-melting-point metal layer 42 are laminated. For example, it is preferable to use a solder such as Pb-free solder as the low-melting-point metal. For example, it is preferable to use Ag, Cu, or an alloy containing these as a main component as the high-melting-point metal. By containing a high-melting-point metal and a low-melting-point metal, when the protection element 11 is reflow-mounted, even if the reflow temperature exceeds the melting temperature of the low-melting-point metal layer and the low-melting-point metal melts, the fuse element 20 will not blow.

[0044] For example, the fuse element 20 may have an inner layer made of a low-melting-point metal and an outer layer made of a high-melting-point metal. For example, the fuse element 20 may have a configuration in which the entire surface of the inner low-melting-point metal layer 41 is covered with the outer high-melting-point metal layer 42. With this configuration, even if a low-melting-point metal with a melting point lower than the reflow temperature is used, the low-melting-point metal of the inner layer can be prevented from leaking out during reflow mounting. Furthermore, when the fuse element 20 blows, the low-melting-point metal of the inner layer melts, corroding (soldering) the high-melting-point metal of the outer layer, allowing it to melt quickly.

[0045] The heat-sensitive element 12 may be an electronic component whose electrical characteristics are temperature-dependent. Referring to both FIGS. 1 and 9, the heat-sensitive element 12 may be a thermostat 12a that opens and closes a circuit in response to changes in the ambient temperature. For example, the heat-sensitive element 12 may be disposed in close proximity to or in contact with the battery stack 15 and thermally connected to the battery stack 15. In this case, the heat-sensitive element 12 is heated by abnormal heat generation in the battery stack 15. This causes changes in the electrical characteristics of the heat-sensitive element 12, such as its resistance value and output voltage.

[0046] For example, if a thermostat 12a is used as the heat-sensitive element 12, one end of the thermostat 12a is connected to the open end of the battery stack 15. The other end of the thermostat 12a is connected to the heating resistor 24 of the protection element 11. The thermostat 12a always opens the current path from the battery stack 15 to the heating resistor 24. When the thermostat 12a in the battery pack 10 heats up due to abnormal heat generation in the battery stack 15 or the like, the thermostat 12a is displaced so as to close the current path from the battery stack 15 to the heating resistor 24. As a result, sufficient power from the battery stack 15 to melt the fuse element 20 is passed through the heating resistor 24.

[0047] Although not shown, the heat-sensitive element 12 may be a thermostat 12a or a negative temperature coefficient thermistor (NTC thermistor, CTR thermistor) whose resistance decreases with an increase in the ambient temperature. The heat-sensitive element 12 may also be a diode whose voltage changes when the temperature exceeds a threshold value. Other examples of the heat-sensitive element 12 include a Peltier element, a thermocouple, a bimetal, and a temperature sensor. For example, the configuration of the heat-sensitive element 12 may be changed according to design specifications.

[0048] 3 to 5, the case 60 includes a first holding member 61 and a second holding member 62 that are stacked in the vertical direction. The first holding member 61 is in the shape of a substantially rectangular cylinder with a closed top and an open bottom. The first holding member 61 may have recesses (not shown) formed at each of its four corners. The second holding member 62 has a substantially rectangular shape in plan view that has the same outer shape as the first holding member 61, and has a concave shape that opens upward in the center in cross section. Each corner (four corners) of the second holding member 62 may be provided with a convex portion (not shown) that can fit into a concave portion formed in the first holding member 61.

[0049] The recessed portions formed in the first holding member 61 and the protruding portions provided on the second holding member 62 may constitute a positioning structure for the case 60. For example, first, an adhesive is applied to at least one of the lower surface of the first holding member 61 and the upper surface of the second holding member 62. Next, the lower surface of the first holding member 61 and the upper surface of the second holding member 62 are aligned so that the first holding member 61 and the second holding member 62 overlap in a plan view, thereby fitting the protruding portions into the recessed portions. In this way, the first holding member 61 and the second holding member 62 may be fixed together with the adhesive.

[0050] Note that the present invention is not limited to forming recesses at each corner of the first holding member 61 and providing protrusions at each corner of the second holding member 62. For example, protrusions may be provided at each corner of the first holding member 61 and recesses may be provided at each corner of the second holding member 62. For example, the manner in which the protrusions are provided and the manner in which the recesses are formed can be changed according to design specifications.

[0051] The rear end (+X end) of the first terminal 22 is connected to the front end (-X end) of the fuse element 20. The front end of the first terminal 22 protrudes from the front side of the case 60 to the outside of the case 60 and is exposed. The front end of the second terminal 23 is connected to the rear end of the fuse element 20 . The rear end of the second terminal 23 protrudes from the rear side of the case 60 to the outside of the case 60 and is exposed. The right end of the third terminal 25 is connected to the left end of the heat generating element lead electrode 21. The left end of the third terminal 25 protrudes from the left side of the case 60 to the outside of the case 60 and is exposed.

[0052] The protective element 11 of this embodiment is of a screw type. Specifically, the protective element 11 is connected to wiring by passing a screw through the holes of the terminals 22, 23, and 25 protruding out of the case 60.

[0053] The island-shaped electrodes 33 are formed on both ends of the surface of the insulating substrate 26. The island-shaped electrodes 33 on one end of the insulating substrate 26 and the island-shaped electrodes 33 on the other end are spaced apart in the front-to-rear direction via the heating resistor 24 and other elements. When the fuse element 20 melts, the island-shaped electrodes 33 hold a portion of the molten conductor of the fuse element 20 away from the first and second terminals 22, 23 due to their wettability.

[0054] (protection circuit) 1 and 9, the protection element 11 has a circuit configuration including a fuse element 20 connected in series across first and second terminals 22, 23, and a heating resistor 24 that melts the fuse element 20 by passing current through a connection point of the fuse element 20 to generate heat. The protection element 11 has a current path from the heat-sensitive element 12, the third terminal 25, the heating resistor 24, and the fuse element 20 to the heating resistor 24, and the current flow to the heating resistor 24 is controlled by the heat-sensitive element 12.

[0055] The protection element 11 is connected to one open end of the battery stack 15 via a first terminal 22. The protection element 11 is connected to the positive terminal 10a of the battery pack 10 via a second terminal 23. As a result, the fuse element 20 is connected in series to the charge / discharge current path of the battery pack 10 via the first and second terminals 22, 23.

[0056] The third terminal 25 of the protection element 11 is connected to one open end of the battery stack 15 that energizes the heating resistor 24, and the heat-sensitive element 12 (e.g., thermostat 12a) limits the current flow to the heating resistor 24. Therefore, the fuse element 20 does not melt due to heat generated by the heating resistor 24, and the charge / discharge current path of the battery pack 10 is allowed to pass current.

[0057] The battery pack 10 may need to interrupt its current path due to abnormal heat generation caused by an overvoltage of the battery cell 15a or abnormal overheating of the surrounding temperature caused by a fire or the like. In this case, the battery pack 10 closes the current path to the heating resistor 24 when the heat-sensitive element 12 heats up and exceeds a predetermined threshold. This allows current to flow from the battery stack 15 to the heating resistor 24. As a result, the protective element 11 heats up the heating resistor 24 to a high temperature, melting the fuse element 20 incorporated in the current path of the battery pack 10. The molten conductor of the fuse element 20 is attracted to the heating element lead electrode 21 and the first and second terminals 22 and 23, which have high wettability, thereby melting the fuse element 20. Therefore, the battery pack 10 melts the path between the first terminal 22, the heating element lead electrode 21, and the second terminal 23, thereby interrupting the current path of the battery stack 15 (see FIG. 10 ).

[0058] Such a battery pack 10 can cut off the charge / discharge current path of the battery stack 15 by activating the protection element 11 with the heat-sensitive element 12. Therefore, regardless of the switch operation of the current control elements 17 and 18 or the control IC that controls the protection element 11, the charge / discharge current path of the battery stack 15 can be cut off without the risk of malfunction even when exposed to a high-temperature environment.

[0059] The protective element 11 forms part of the current path to the heating resistor 24 by connecting the fuse element 20 to the heating resistor 24. Therefore, when the fuse element 20 melts and the connection to the external circuit is cut off, the current path to the heating resistor 24 is also cut off, so that the protective element 11 can stop heat generation.

[0060] 11, the battery pack 10 may include a switch circuit 50 in addition to the heat-sensitive element 12 (thermistor 12b in the figure). The switch circuit 50 has a function of detecting an abnormal voltage of the entire battery stack 15 and / or an abnormal voltage of each battery cell 15a, and activating the protection element 11 by operating a switch. For example, the switch circuit 50 includes a protection IC 51 that monitors the voltage of the entire battery stack 15 and / or the voltage of each battery cell 15a, and a switch 52 that is operated by the protection IC 51.

[0061] The switch 52 is, for example, a FET. One end of the switch 52 is connected to one open end of the battery stack 15 or the battery cell 15a. The other end of the switch 52 is connected to the heating resistor 24 of the protection element 11. This connects the switch 52 in parallel with the heat-sensitive element 12 (thermistor 12b in the figure). The switch 52 is controlled by the protection IC 51 to switch between an on state and an off state.

[0062] The Protection IC 51 is connected to, for example, both open ends of the battery stack 15 and each battery cell 15 a. The Protection IC 51, for example, constantly monitors the voltage of the entire battery stack 15 and / or the voltage of each battery cell 15 a, and turns on the switch 52 to energize the heating resistor 24 when an abnormal voltage is detected.

[0063] Specifically, the Protection IC 51 determines whether or not an overvoltage exists based on the voltage across the battery stack 15 and / or the battery cell 15a. For example, if the voltage of the battery cell 15a exceeds a predetermined threshold during charging, the Protection IC 51 determines that the voltage of the battery stack 15 or the battery cell 15a is an overvoltage. If the Protection IC 51 determines that an overvoltage exists, it controls the switch 52 to change from an OFF state to an ON state. This activates the protection element 11, which melts the fuse element 20, thereby interrupting the charge / discharge current path of the battery stack 15.

[0064] In the protection circuit described above, the heat-sensitive element 12 is provided in parallel with the charge / discharge path of the battery stack 15, but this is not limiting. For example, the heat-sensitive element 12 may be provided on a path electrically independent of the charge / discharge path of the battery stack 15, and power may be supplied from a separately provided power source. Furthermore, the battery pack of the present invention is not limited to use in the battery pack 10 of lithium-ion secondary batteries, and can be applied to various uses that require the current path to be cut off in the event of abnormal overheating.

[0065] (Connection with fuse elements, etc.) 3 to 5, the fuse element 20 of this embodiment is provided so as to straddle the first terminal 22 and the second terminal 23. The fuse element 20 is fixed to the first terminal 22, the second terminal 23, and the heating element lead electrode 21 via fixing solder 28 (hereinafter simply referred to as "solder 28"). The fixing solder 28 is an example of a fixing member having electrical conductivity.

[0066] For example, the solder 28 is a Pb-free solder. For example, the material of the solder 28 can be a metal material such as Sn, an Sn-Cu alloy, an Sn-Bi alloy, or an Sn-Ag alloy. For example, the material of the solder 28 can be a mixture of low-melting-point metal particles (Bi) and high-melting-point metal particles (Sn, Ag, Cu, etc.), or a material in which a coating layer of low-melting-point metal particles is formed on the surface of high-melting-point metal particles. For example, the material of the solder 28 is not limited to the above and can be changed according to design specifications.

[0067] (Configuration of the first and second terminals) 5 to 7, each of the first terminal 22 and the second terminal 23 has a connection portion 70 that is connected to the fuse element 20 in an overlapping area SA where the portions that face each other in the current-carrying direction are positioned more inward than both ends of the fuse element 20 in a plan view and overlap with the fuse element 20, and a hollow portion 71 is formed therein. Note that the hollow portion 71 is not formed in the overlapping area SA of the fuse element 20.

[0068] The hollow portion 71 is formed to include a recess 72 recessed outward in the current-carrying direction from the first terminal 22 and the second terminal 23 that face each other in the current-carrying direction in plan view. When the inner end of each of the rectangular terminals 22, 23 in the current-carrying direction in plan view (a virtual line along the width direction indicated by a two-dot chain line in FIG. 7) is used as a reference, the recess 72 is a portion recessed outward in the current-carrying direction from this inner end.

[0069] The recess 72 is formed so that distances D1 and D2 from a center position CP, which is the center between the opposing first terminal 22 and the opposing second terminal 23 in the current-carrying direction and the center in the width direction perpendicular to the current-carrying direction in a plan view, to the opposing portions are the same. These distances D1 and D2 refer to the lengths from the center position CP to the bottom edge of the recess 72 in a plan view.

[0070] The recess 72 is formed in a V-shape that protrudes outward in the current-carrying direction in plan view. In other words, the recess 72 is formed in a shape that follows the two hypotenuses of an isosceles triangle whose vertices are on an imaginary line (on the dashed-dotted line shown in FIG. 7) that passes through the center position CP and extends in the front-rear direction in plan view.

[0071] The connecting portion 70 is formed to include a right-angled triangular portion having one side that is the hypotenuse of the recess 72 in a plan view. The connecting portion 70 is formed to include a pair of portions that sandwich the recess 72 in the width direction in a plan view. The pair of portions are formed to have an axisymmetric shape with respect to a virtual line (the dashed dotted line shown in FIG. 7) as the axis of symmetry in a plan view.

[0072] In this embodiment, solder 28 (corresponding to part of fixing member 28) is provided on connecting portion 70. In the example shown in the figure, solder 28 is provided in a portion along the outer edge of fuse element 20, inside connecting portion 70 in plan view (see FIG. 5).

[0073] (Protective element manufacturing method) The method for manufacturing the protection element 11 of this embodiment includes a step of connecting the fuse element 20 to the terminals 21, 22, and 23 via fixing solder 28. An example of the method for manufacturing the protection element 11 of this embodiment will be described below.

[0074] First, fixing solder 28 is applied to the heating element lead electrode 21 and each of the terminals 22, 23. Then, the fuse element 20 is connected to the heating element lead electrode 21 and each of the terminals 22, 23 via the fixing solder 28. For example, a solder paste containing a Sn-Bi based solder material is used as the fixing solder 28. Note that an adhesive-type Sn-Bi solder paste may also be used as the fixing solder 28.

[0075] Next, reflow heating is performed using a reflow furnace (reflow device) not shown, and the fuse element 20 is solder-connected to the heating element lead electrode 21 and each of the terminals 22, 23. In this embodiment, by using a Sn-Bi based solder material as the fixing solder 28, reflow heating can be performed at a temperature of less than 150°C. The reflow heating melts the fixing solder 28, and alloys the base metal and the fuse element 20. This electrically connects and fixes the fuse element 20 to the heating element lead electrode 21 and each of the terminals 22, 23. Note that the heating method used during solder connection is not limited to the above, and a hot plate using a heater as a heat source may also be used.

[0076] In this embodiment, each of the first terminal 22 and the second terminal 23 has a connection portion 70 connected to the fuse element 20 and a hollow portion 71 formed in the overlapping area SA. The solder 28 is provided in the portion that overlaps with the connection portion 70 in a plan view. Note that the solder 28 is not provided in the portion that overlaps with the hollow portion 71 in a plan view (see FIG. 5).

[0077] (Effects of this embodiment) The protective element 11 of the present embodiment described above includes a fuse element 20, a first terminal 22 and a second terminal 23 connected to both ends of the fuse element 20 in the current-carrying direction, and a case 60 that accommodates parts of the first terminal 22 and the second terminal 23, and the fuse element 20. Each of the first terminal 22 and the second terminal 23 has a connection part 70 that connects to the fuse element 20 in an overlapping area SA where the parts that face each other in the current-carrying direction are positioned inside both ends of the fuse element 20 in a plan view and overlap with the fuse element 20, and a hollow part 71 is formed therein. After extensive research, the inventors discovered that providing a connection portion 70 and a hollow portion 71 in the overlapping region SA of each of the first terminal 22 and the second terminal 23 prevents tracking from occurring after current interruption, even when a high voltage is interrupted. Therefore, this configuration makes it possible to provide a protective element 11 that can suppress the occurrence of tracking. In addition, the protective element 11 can be used to safely blow the fuse element 20.

[0078] In this embodiment, the hollow portion 71 is formed to include a recess 72 recessed outward in the current-carrying direction from the portions where the first terminal 22 and the second terminal 23 face each other in the current-carrying direction in a plan view. According to this configuration, even if sparks are generated repeatedly after the fuse element 20 is cut off, the formation of the recessed portion 72 can suppress the adhesion of soot and the progression of carbonization (track formation) of the fuse element 20. Therefore, the occurrence of the tracking phenomenon can be more effectively suppressed.

[0079] In this embodiment, the recess 72 is formed so that the distances D1 and D2 from the center position CP, which is the center between the first terminal 22 and the second terminal 23 facing each other in the current flow direction when viewed in a plane and the center in the width direction perpendicular to the current flow direction, to the opposing portions are the same. With this configuration, even if the melting impact (explosion) when the fuse element 20 is cut off is severe, the distances D1 and D2 from the center of the explosion are the same, making it easier for the fuse element 20 to melt concentrically. This makes it possible to suppress the adhesion of soot and the progression of carbonization (track formation) on the fuse element 20. Therefore, the occurrence of the tracking phenomenon can be more effectively suppressed.

[0080] In this embodiment, the recess 72 is formed in a V-shape that protrudes outward in the current-carrying direction in plan view. With this configuration, even if the fuse element 20 is subjected to a severe melting impact (explosion) when it is cut off, the fuse element 20 is likely to melt along the V-shape of the recess 72. This makes it possible to suppress the adhesion of soot to the fuse element 20 and the progression of carbonization (track formation). Therefore, the occurrence of the tracking phenomenon can be more effectively suppressed.

[0081] In this embodiment, the protection element 11 is arranged between the first terminal 22 and the second terminal 23 that face each other in the current flow direction when viewed in a plane, and includes an insulating substrate 26 housed in a case 60, and a heating resistor 24 provided on the insulating substrate 26. According to this configuration, in the protection element 11 having the heating resistor 24 on the insulating substrate 26, it is possible to suppress the occurrence of the tracking phenomenon.

[0082] A protective element 11X according to a comparative example will be described with reference to FIGS. The protection element 11X according to the comparative example includes an insulating substrate, first and second terminals functioning as fuse terminals, a third terminal functioning as a heater terminal, a heating resistor formed on the surface of the insulating substrate, an insulating layer covering the heating resistor, a heating element lead electrode laminated on the insulating layer and connected to the heating resistor, a fuse element mounted via a fixing member across the first terminal, the heating element lead electrode, and the second terminal, an island electrode, and a case. In the protection element 11X according to the comparative example, each of the first terminal and the second terminal is formed in a rectangular shape in a plan view. In the protection element 11X according to the comparative example, no hollow portion is formed in the overlapping region of each of the first terminal and the second terminal.

[0083] In the protective device 11X according to the comparative example, an explosion occurs when the fuse element melts during current interruption. After that, soot from the fuse element adheres to the insulating substrate and turns black and carbonized, which increases the likelihood of a tracking phenomenon. This tracking phenomenon becomes more pronounced as the withstand voltage and current increase (as the rated voltage increases and the current capacity increases).

[0084] In the case of the protection element 11X according to the comparative example, after current is interrupted at a voltage greater than 80 V (for example, 100 V or more), sparks occur between the insulating substrate and the first and second terminals functioning as fuse terminals, followed by a tracking phenomenon.

[0085] In contrast, in the protection element 11 according to this embodiment, as described above, the occurrence of tracking after current interruption can be suppressed even when a high voltage current is interrupted by providing the connection portion 70 and the hollow portion 71 in the overlapping region SA of each of the first terminal 22 and the second terminal 23. In the case of the protection element 11 according to this embodiment, the occurrence of tracking after current interruption can be prevented even when the voltage is greater than 80 V (for example, 100 V or more).

[0086] The present invention is not limited to the above-described embodiment, and the configuration may be modified within the scope of the present invention, as described below. In the illustrations of other embodiments and modifications, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the following mainly describes the differences.

[0087] (Variation) In the above embodiment, an example has been described in which the hollow portion is formed to include a recess recessed outward in the current-carrying direction from the portions of the first terminal and the second terminal facing each other in the current-carrying direction in a plan view, but this is not limited thereto. For example, the hollow portion may be formed to include a through-hole that opens in a plan view. For example, the hollow portion may be formed to include a recess and / or a through-hole. The form of the hollow portion can be changed according to design specifications.

[0088] In the above embodiment, the recesses are formed so that the distances from the center position, which is the center between the first and second terminals facing each other in the current-carrying direction in a plan view and the center in the width direction perpendicular to the current-carrying direction, to the opposing portions are the same, but this is not limited to this. For example, the recesses may be formed so that the distances from the center position, which is the center between the first and second terminals facing each other in the current-carrying direction in a plan view and the center in the width direction perpendicular to the current-carrying direction, to the opposing portions are different. The formation mode of the recesses can be changed depending on the design specifications.

[0089] In the above embodiment, the recess is formed in a V-shape convex outward in the current-carrying direction in a plan view, but this is not limiting. For example, the recess may be formed in a U-shape in a plan view. The planar shape of the recess can be changed according to design specifications.

[0090] In the above embodiment, the protective element is disposed between the first terminal and the second terminal that face each other in the current-carrying direction in a plan view, and includes an insulating substrate housed in a case and a heating resistor provided on the insulating substrate. However, the present invention is not limited to this. For example, the protective element does not need to include an insulating substrate and a heating resistor. The installation mode of the insulating substrate and / or the heating resistor can be changed according to design specifications.

[0091] (Other variations) Another modified example according to the embodiment of the present invention will be described with reference to Figures 14 to 17. In each figure of this modified example, components that are the same or substantially the same as those in the first embodiment are given the same reference numerals or names, and descriptions thereof may be omitted.

[0092] In the above embodiment, the recesses are formed in a V-shape that protrudes outward in the current-carrying direction in plan view. However, this is not limiting. As shown in Figs. 14 and 15, for example, the recesses 72A and 72B may be formed in an arc shape that curves outward in the current-carrying direction in plan view. In the example of Fig. 14, the recess 72A is formed in an arc shape that conforms to an ellipse with its major axis in the width direction in plan view. In the example of Fig. 15, the recess 72B is formed in an arc shape that conforms to a circle that is offset in the current-carrying direction from a perfect circle concentric with the center position CP in plan view.

[0093] In the modified examples of FIGS. 14 and 15, the recesses 72A and 72B are formed in an arc shape that curves outward in the current-carrying direction in plan view. With this configuration, even if the fuse element 20 is subjected to a severe melting impact (explosion) when it is cut off, the fuse element 20 is likely to melt along the arc-shaped recesses 72A, 72B. This makes it possible to suppress the adhesion of soot and the progression of carbonization (track formation) of the fuse element 20. Therefore, the occurrence of the tracking phenomenon can be more effectively suppressed. 15, the recess 72B is formed in an arc shape along a circle that is offset in the current-carrying direction from a perfect circle concentric with the center position CP in a plan view, so that when the fuse element 20 explodes from the center position CP and spreads concentrically (or offset in the current-carrying direction) after an interruption, the fuse element 20 is more likely to melt concentrically. This makes it possible to more effectively suppress the occurrence of tracking.

[0094] For example, as shown in Fig. 16, the recess 72C may be formed in a U-shape recessed outward in the current-carrying direction in plan view. In the example of Fig. 16, the recess 72C is formed in a shape that follows three sides of a rectangle whose longitudinal sides are in the width direction in plan view.

[0095] In the example of FIG. 16, the recess 72C is formed in a U-shape recessed outward in the current-carrying direction in a plan view. With this configuration, even if the fuse element 20 is subjected to a severe melting impact (explosion) when it is cut off, the fuse element 20 is likely to melt along the U-shape of the recess 72C. This makes it possible to suppress the adhesion of soot and the progression of carbonization (track formation) of the fuse element 20. Therefore, the occurrence of the tracking phenomenon can be more effectively suppressed.

[0096] For example, as shown in Fig. 17, hollow portion 71 may be formed to include a plurality of through holes 72D that open in overlapping region SA in plan view. In the example of Fig. 17, the number of through holes 72D increases as distances D1, D2 from center position CP, which is the center between first terminal 22 and second terminal 23 that face each other in the current-carrying direction and the center in the width direction perpendicular to the current-carrying direction, to the facing portions.

[0097] 17, each of the first terminal 22 and the second terminal 23 is formed to have a rectangular outer shape in a plan view. In the example of Fig. 17, 27 through holes 72D (3 rows in the width direction and 9 columns in the current-carrying direction) are formed in a portion of each of the first terminal 22 and the second terminal 23 that is on the inner side in the current-carrying direction and the inner side in the width direction. Note that the arrangement of the through holes 72D (the location and number of the through holes) is not limited to the above and can be changed according to design specifications.

[0098] In the example of FIG. 17, the hollow portion 71 is formed to include a plurality of through holes 72D that open in the overlapping region SA in a plan view. According to this configuration, even if sparks are generated repeatedly after the fuse element 20 is cut off, the formation of the plurality of through-holes 72D can suppress the adhesion of soot and the progression of carbonization (track formation) of the fuse element 20. Therefore, the occurrence of the tracking phenomenon can be more effectively suppressed.

[0099] In the example of Figure 17, the number of multiple through holes 72D formed is greater in areas where the distances D1, D2 from the center position CP, which is the center between the first terminal 22 and the second terminal 23 facing each other in the current flow direction when viewed in a plane and the center in the width direction perpendicular to the current flow direction, to the opposing parts are closer. With this configuration, even if the melting impact (explosion) when the fuse element 20 is cut off is severe, many through-holes 72D are formed in the area close to the center of the explosion, making the fuse element 20 more likely to melt. This makes it possible to suppress the adhesion of soot and the progression of carbonization (track formation) on the fuse element 20. Therefore, the occurrence of the tracking phenomenon can be more effectively suppressed.

[0100] (Protection element (second embodiment)) A protective element 211 according to a second embodiment of the present invention will be described with reference to Figures 18 and 19. The protective element 211 of the second embodiment differs from the first embodiment described above mainly in that a heating resistor is provided on the rear surface (back surface) of the insulating substrate (a rear heater is provided). Note that in the drawings of this embodiment, components that are the same or substantially the same as those in the first embodiment may be denoted by the same reference numerals or names, and descriptions thereof may be omitted.

[0101] 18 and 19 , the protection element 211 includes an insulating substrate 26, first and second terminals 22 and 23 functioning as fuse terminals, a third terminal 25 functioning as a heater terminal, a heating resistor 24 formed on the back surface of the insulating substrate 26 (the surface opposite to the fuse element 20), an insulating layer 27 covering the heating resistor 24, a heating element lead electrode 21 stacked on the insulating layer 27 via the insulating substrate 26 and connected to the heating resistor 24, a fuse element 20 mounted across the first terminal 22, the heating element lead electrode 21, and the second terminal 23 via fixing solder 28, an island electrode 33, and a case 60. The fuse element 20 is joined to the terminals 22 and 23 by the solder 28.

[0102] In the protective element 211 according to the second embodiment, by providing a connection portion 70 and a hollow portion 71 in the overlapping region SA of each of the first terminal 22 and the second terminal 23, it is possible to suppress the occurrence of tracking phenomenon after current interruption, even when a high voltage current is interrupted.

[0103] (Protection element (third embodiment)) A protection element 311 according to a third embodiment of the present invention will be described with reference to Figures 20 and 21. The protection element 311 of the third embodiment differs from the first embodiment described above mainly in that the heating resistor 324 is located on insulating substrates 326A and 326B, sandwiching the fuse element 20. In the drawings of this embodiment, components that are similar or substantially similar to those in the first and second embodiments may be denoted by the same reference numerals or names, and descriptions thereof may be omitted.

[0104] 20 and 21 , the protection element 311 includes first and second insulating substrates 326A and 326B, first and second terminals 22 and 23, a heating resistor 324 provided on the surfaces of the insulating substrates 326A and 326B, an insulating layer 327 covering the heating resistor 324, a heating element lead electrode 321 laminated on the insulating layer 327 and connected to the heating resistor 324, a fuse element 20 mounted across the first terminal 22, the heating element lead electrode 321, and the second terminal 23 via fixing solder 28, a surface electrode 371, a conductive layer 372, a back electrode 373, an island electrode 333, and a case 60. The fuse element 20 is joined to the terminals 22 and 23 by the solder 28.

[0105] The insulating substrates 326A and 326B are disposed between the first and second terminals 22 and 23. The insulating substrates 326A and 326B are spaced apart from each other in the vertical direction. One insulating substrate 326A is disposed above the fuse element 20. The other insulating substrate 326B is disposed below the fuse element 20. The insulating substrates 326A and 326B are formed with through-holes 326h that penetrate the insulating substrates 326A and 326B in the thickness direction.

[0106] The surface electrode 371 is formed on the surface of the insulating substrates 326A and 326B (on the surface on the fuse element 20 side). The surface electrode 371 is disposed between the fuse element 20 and the insulating layer 327. The surface electrode 371 is connected to a part of the fuse element 20 via solder or the like.

[0107] When the fuse element 20 melts due to the heat generated by the heating resistor 324, the melted fuse element 20 (hereinafter also referred to as the "molten conductor") aggregates on the surface electrode 371. As a result, the molten conductor aggregated on the surface electrode 371 can be drawn into the through-hole 326h by capillary action. As a result, even when the cross-sectional area of ​​the fuse element 20 is increased to accommodate high-current applications, the protection device 311 can reliably interrupt the current path between the first and second terminals 22, 23 without the molten conductor excessively agglomerating on the surfaces of the insulating substrates 326A, 326B.

[0108] The conductive layer 372 is formed on the inner circumferential surface of the through-hole 326h of the insulating substrates 326A and 326B. The conductive layer 372 is continuous with the surface electrode 371. The conductive layer 372 is formed, for example, from a metal material that allows a molten conductor to spread thereon. The conductive layer 372 is formed, for example, by a paste process, a plating process, or the like.

[0109] Since the conductive layer 372 is continuous with the surface electrode 371, the protective element 311 can easily draw the molten conductor that has aggregated on the surface electrode 371 into the through-hole 326h. This allows a larger amount of the molten conductor to be drawn into the through-hole 326h.

[0110] The back electrode 373 is formed on the back surface of the insulating substrates 326A, 326B (the surface opposite to the fuse element 20). The back electrode 373 is formed on the opposite side of the insulating substrates 326A, 326B from the front electrode 371. The back electrode 373 is continuous with the conductive layer 372.

[0111] Because the back electrode 373 is continuous with the conductive layer 372, the molten conductor that has traveled along the conductive layer 372 and been drawn into the through-hole 326h is concentrated on the back electrode 373. This allows even more molten conductor to be drawn in.

[0112] The island electrodes 333 are formed on the edges of the surfaces of the insulating substrates 326A and 326B. The island electrodes 333 are spaced apart from the outer surface electrodes 371 in the front-to-rear direction. When the fuse element 20 melts, the island electrodes 333 retain a portion of the molten conductor at a distance from the surface electrodes 371 and the first and second terminals 22 and 23 due to their wettability.

[0113] The through-hole 326h may be filled with preliminary solder 375 having a melting point lower than that of the fuse element 20. With this configuration, when the heating resistor 324 generates heat, the preliminary solder 375 melts before the fuse element 20, and the molten conductor can be drawn into the through-hole 326h. As a result, the molten conductor can be efficiently drawn from the front side to the back side of the insulating substrates 326A and 326B, and the current path between the first terminal 22 and the second terminal 23 can be reliably interrupted regardless of the position.

[0114] For example, at least a portion of through-hole 326h may be filled with flux together with or instead of pre-solder 375. This configuration also improves the wettability of fuse element 20, allowing the molten conductor to be efficiently drawn into through-hole 326h.

[0115] In this embodiment, a plurality of heating resistors 324 are arranged on both sides of the fuse element 20 in the vertical direction. One end of each heating resistor 324 is connected to the fuse element 20 via a heating element lead electrode 321. The other end of each heating resistor 324 is connected to a power source for generating heat from the heating resistor 324 via an external connection electrode (not shown).

[0116] When the protective element 311 melts the fuse element 20, each heating resistor 324 generates heat and draws the molten conductor into each through-hole 326h. Therefore, even when the cross-sectional area of ​​the fuse element 20 is increased to accommodate large current applications and a large amount of molten conductor is generated, the protective element 311 can draw the molten conductor from both the top and bottom directions and reliably melt the fuse element 20. Furthermore, by drawing the molten conductor from both the top and bottom directions, the protective element 311 can melt the fuse element 20 more quickly.

[0117] The protective element 311 can quickly blow the fuse element 20 even when the fuse element 20 has a coating structure in which a low-melting-point metal constituting the inner layer is coated with a high-melting-point metal. A fuse element 20 coated with a high-melting-point metal requires time to heat up to a temperature at which the high-melting-point metal in the outer layer melts, even when the heating resistor 324 generates heat. The protective element 311 includes multiple heating resistors 324, and by simultaneously heating each heating resistor 324, the high-melting-point metal in the outer layer can be quickly heated to its melting temperature. Therefore, the protective element 311 allows the thickness of the high-melting-point metal layer constituting the outer layer to be increased, thereby achieving a higher rating and maintaining fast-fusing characteristics.

[0118] The protective element 311 is preferably connected to the fuse element 20 with a pair of heating resistors 324 facing each other. This allows the protective element 311 to simultaneously heat the same location on the fuse element 20 from both sides with the pair of heating resistors 324 and to attract molten conductor from both above and below. This allows the fuse element 20 to be heated and blown more quickly.

[0119] In the protection element 311 of the third embodiment, by providing a connection portion 70 and a hollow portion 71 in the overlapping region SA of each of the first terminal 22 and the second terminal 23, it is possible to suppress the occurrence of tracking phenomenon after current interruption, even when a high voltage current is interrupted.

[0120] (Protection element (fourth embodiment)) A protective element 411 according to a fourth embodiment of the present invention will be described with reference to Fig. 22. The protective element 411 of the fourth embodiment differs from the third embodiment described above mainly in that a heating resistor is provided on the rear surface (back surface) of the insulating substrate (a rear heater is provided). In the drawings of this embodiment, components that are the same or substantially the same as those of the first to third embodiments may be given the same reference numerals or names, and descriptions thereof may be omitted.

[0121] 22 , the protection element 411 includes first and second insulating substrates 326A and 326B, first and second terminals 22 and 23, a heating resistor 324 provided on the back surfaces of the insulating substrates 326A and 326B (the surfaces opposite to the fuse element 20), an insulating layer 327 covering the heating resistor 324, a heating element lead electrode 321 laminated on the insulating layer 327 and connected to the heating resistor 324, the fuse element 20 mounted across the first terminal 22, the heating element lead electrode 321, and the second terminal 23 via fixing solder 28, a surface electrode 371, a conductive layer 372, a back electrode 373, an island electrode 333, and a case 60. The fuse element 20 is joined to the terminals 22 and 23 by the solder 28.

[0122] In the protection element 411 of the fourth embodiment, by providing a connection portion 70 and a hollow portion 71 in the overlapping region SA of each of the first terminal 22 and the second terminal 23, it is possible to suppress the occurrence of tracking phenomenon after current interruption, even when a high voltage current is interrupted.

[0123] The protection element of the present invention is not limited to the above-described embodiment.

[0124] The present invention may be combined with the various configurations described in the above-described embodiments, modifications, and reference examples, and may also include additions, omissions, substitutions, and other modifications of the configurations, without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the above-described embodiments, but is limited only by the claims. [Explanation of symbols]

[0125] 11,211,311,411 Protection elements 20 Fuse element 22 1st terminal 23 2nd terminal 24 Heating resistor 26 Insulating substrate 60 cases 70 Connection 71 Hollow part 72 recess CP center position D1,D2 distance SA overlap area

Claims

1. A fuse element; a first terminal and a second terminal connected to both ends of the fuse element in the current-carrying direction; a case that accommodates the first terminal, a portion of the second terminal, and the fuse element; Each of the first terminal and the second terminal has a connection portion connected to the fuse element and a hollow portion formed in an overlapping region where portions facing each other in the current-carrying direction are arranged inside the both end portions of the fuse element in a plan view and overlap with the fuse element. Protection element.

2. the hollow portion is formed to include a recess that is recessed outward in the current-carrying direction from portions of the first terminal and the second terminal that face each other in the current-carrying direction in the plan view. The protection element according to claim 1 .

3. the recess is formed so that the distances from a center position, which is a center between the first terminal and the second terminal facing each other in the current-carrying direction and a center in a width direction perpendicular to the current-carrying direction, to the facing portions are equal to each other in the plan view. The protection element according to claim 2 .

4. The recess is formed in a V-shape that is convex outward in the current-carrying direction in the plan view. The protection element according to claim 2 .

5. The recess is formed in an arc shape that curves outward in the current-carrying direction in the plan view. The protection element according to claim 2 .

6. The recess is formed in a U-shape recessed outward in the current-carrying direction in the plan view. The protection element according to claim 2 .

7. The hollow portion is formed to include a plurality of through holes that open in the overlapping region in the plan view. The protection element according to claim 1 .

8. the plurality of through holes are formed in a greater number in the areas where the distance from a center position, which is a center between the first terminal and the second terminal facing each other in the current-carrying direction and a center in a width direction perpendicular to the current-carrying direction, to the facing areas is shorter in the plan view; The protection element according to claim 7 .

9. an insulating substrate disposed between the first terminal and the second terminal facing each other in the current-carrying direction in the plan view and accommodated in the case; a heating resistor provided on the insulating substrate, The protection element according to claim 1 .

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