JP4757898B2 - Protective element - Google Patents

Description

  The present invention relates to a protection element for an electrical device, which is useful for interrupting overcurrent to a high-capacity secondary battery, for example, a high-capacity lithium ion secondary battery, and stopping charging and discharging at the time of overcharge or overdischarge. It is.

In secondary batteries, for example, lithium ion secondary batteries, it is required to shut off the secondary battery from the load or the charging power source against overcurrent, overcharge or overdischarge. An alloy fuse and a resistor that are in close proximity to each other are known.
FIG. 3 shows an example of a secondary battery protection circuit.
In FIG. 3, E is a secondary battery, L is a load, S is a charging power source, sw is a switch such as a transistor, and T is an IC that detects a overcharge or overdischarge of the secondary battery and issues a switch-on signal. When each circuit is shown and an overcurrent flows, the low melting point alloy fuse 30 ′ of the protective element A ′ is blown to cut off the load L and the secondary battery E, and the secondary battery E is overdischarged. On the other hand, the switch sw is turned on by the IC circuit T, the resistor 8 ′ of the protective element A ′ is energized and heated by the secondary battery E, and the low melting point alloy fuse 30 ′ is blown by the generated heat, and the secondary battery E The load L is interrupted.
Furthermore, for overcharge, the switch sw is turned on by the IC circuit T, the resistor 8 ′ of the protection element A ′ is energized and heated by the secondary battery E or the charging power source S, and the generated heat reduces the protection element A ′. The melting point alloy fuse 30 ′ is blown to block between the secondary battery E and the charging power source S.

  In the present inventors, when a direct current is passed through a low melting point alloy fuse such as a Bi based low melting point alloy or an Sb based low melting point alloy for a long time, among the electrodes at both ends of the fuse, the anode side electrode and the low melting point alloy It has been confirmed that the alloy at the interface with the fuse undergoes migration and cracks occur before the low melting point alloy fuse performs its original operation.

The reason for the migration of the low melting point alloy fuse can be estimated as follows.
Low melting point alloys include eutectic type alloys, solid solution type alloys, and intermetallic compound type alloys. From a microscopic viewpoint, these two types of metal atoms are mixed to create a crystal lattice with a new atomic arrangement. It can be said that the ionized atoms at the lattice points are in an equilibrium state. However, Bi atoms and Sb atoms are likely to jump out of the equilibrium position, and are given energy by the applied voltage, jump out of the lattice points, dislodge in the crystal lattice as a dislocation atom, and in the case of direct current, the dislocation atom is a cathode. Moves to the side and deposits at the cathode interface. In the vacancies where the dislocation atoms jumped out, as if a certain seat was vacant in the crowded seat, the passengers next to the vacant seat moved one by one and filled in new vacancies, It can be presumed that they move to the anode interface, where the pores coalesce at the interface and cracks occur.

Examples of migration of Bi-based low melting point alloy fuses and Sb-based low melting point alloy fuses are as follows.
A copper lead conductor with a diameter of 1 mmφ was welded to both ends of a 57 wt% Bi-remainder Sn, 1 mmφ diameter, 5 mm long low melting point alloy piece, and a 15 ampere direct current was applied for 5000 hours. The end face of the copper lead conductor on the cathode side A Bi metal layer having a thickness of 200 μm was deposited in contact therewith, and a gap having a thickness of 30 μm was formed in contact with the end face of the copper lead conductor on the anode side.
Also, a copper lead conductor with a diameter of 2 mmφ was welded to both ends of a 5 wt% Sb-remainder Sn, a diameter of 2 mmφ and a length of 7 mm and a copper lead conductor with a diameter of 2 mmφ was energized for 5000 hours. An Sb metal layer having a thickness of 50 μm was deposited in contact with the end surface of the electrode, and a 20 μm-thick void was formed in contact with the end surface of the copper lead conductor on the anode side.

  In FIG. 3, “a protective element in which a low melting point alloy fuse and a resistor are collectively” indicated by reference numeral A ′ is well known (for example, Patent Document 1, Patent Document 2, etc.).

Japanese Utility Model Publication No. 62-024451 Japanese Utility Model Publication No. 58-157943

  Thus, in FIG. 3, the polarity of the both end electrodes of the low melting point alloy fuse 30 ′ changes at the time of charging and discharging, but the amount of power per hour is larger at the time of charging than at the time of discharging. The migration of the low melting point alloy fuse 30 'is difficult to avoid.

Therefore, the present inventors have proposed a protective element as shown in FIG. (Patent Document 3)
In FIG. 4, 10 is a heat-resistant insulating pedestal. Reference numerals 1 and 1 denote a pair of parallel pin electrodes which are inserted and fixed to the insulating base 10. Reference numeral 8 denotes a wire-wound resistor. Cap electrodes 801 with lead conductors are attached to both ends of a heat-resistant insulating core, resistance wires are wound around the core, and each winding end is joined to each cap electrode 801, 802 by welding or the like. Thus, the other lead conductor 80b is drawn out from the insulating base 10 between the pin electrodes 1 and 1. Reference numeral 2 denotes an overcurrent exothermic piece, which is inserted in the hole through the guide shaft 6 and in contact with the pin electrodes 1 and 1 with a sufficiently low resistance, compared to the cross section of the electrode 1. A thin metal plate or an alloy plate having a higher specific resistance than the electrode 1 can be used. Reference numeral 3 denotes a fusible alloy in which the overcurrent exothermic piece 2 and the pin electrodes 1 and 1 and the overcurrent exothermic piece 2 and the guide shaft 6 are joined. Reference numeral 7 denotes a spring, which is inserted into the guide shaft 6 in a compressed state between the overcurrent exothermic piece 2 and one end of the resistor body. When the fusible alloy 3 is melted, the overcurrent exothermic piece 2 is Stress energy that can be detached from the pin electrodes 1 and 1 is retained. Reference numeral 800 denotes a resin mold coating provided on the body of the resistor 8 across the pin electrodes 1 and 1. 5 is a case.

The protection element is used as a protection element of the secondary battery protection circuit shown in FIG.
When an overcurrent flows during discharge, the overcurrent exothermic piece 2 of the protective element A is heated to melt the fusible alloy 3, release the stress energy of the spring 7, and place the overcurrent exothermic piece 2 between the electrodes 1 and 1. Is disconnected from the load L and the secondary battery E, and the switch sw is turned on by a signal from the IC circuit T in response to the overdischarge of the secondary battery E, and the resistor 8 is connected to the secondary battery. The battery E is energized and heated, the fusible alloy 3 is melted by the generated heat, the compression stress energy of the spring 7 is released, the overcurrent exothermic piece 2 is detached from between the electrodes 1 and 1, and the secondary battery E The load L is disconnected.
In this case, even if the melting point of the fusible alloy has changed due to the migration, the resistance value of the overcurrent exothermic piece is set so that the exothermic temperature of the overcurrent exothermic piece takes into account the change. Thus, the overcurrent interruption can be surely performed.

Further, during charging, the switch sw is turned on by a signal from the IC circuit T for overcharging, the resistor 8 is energized and heated by the secondary battery E or the charging power source S, and the fusible alloy 3 is melted by the generated heat. Then, the compressive stress energy of the spring 7 is released, and the overcurrent exothermic piece 2 is detached from the interelectrodes 1 and 1 so that the secondary battery E and the charging power source S are disconnected.
In this case, even if the melting point of the fusible alloy has changed due to the migration, the energization is cut off by setting the resistance value of the resistor so that the heating temperature of the resistor body takes into account the change. Can be performed reliably.

  In the protection element shown in FIG. 4, the reaction force of the compression spring 7 is generated by two portions of the fusible alloys 3 and 3 joining the pin electrodes 1 and 1 and the overcurrent exothermic piece 2 and one of the resistors 8. Since the lead conductor 80a and the overcurrent exothermic piece 2 are supported at a total of three locations of the fusible alloy 3, the stress of the fusible alloy at each location can be reduced, and the fusible alloy can be reduced accordingly. The creep can be reduced well, and the operation can be secured well.

  However, in the protection element shown in FIG. 4, the spring 7 is interposed between the resistor body 8 and the overcurrent exothermic piece 2, and the distance from the resistor body 8 to each of the soluble alloys 3, 3, 3 is Since it is far away, the time required for the heat generated by the resistor main body 8 to be transmitted to each fusible alloy becomes longer, and there is a problem in the operation speed.

  An object of the present invention is to dispose an overcurrent exothermic piece across one lead conductor of a resistor and a pair of pin electrodes, and the overcurrent exothermic piece, the one lead conductor, and the pair of pin electrodes. A spring is provided between each of the pair of pin electrodes and one of the lead conductors so that the overcurrent exothermic piece is detached from the pair of pin electrodes and one of the lead conductors. Improves the speed of operation of the protective element that connects a resistor heating circuit that melts the fusible alloy by energizing and heating the resistor body when the protected device is abnormal. There is to make it.

According to a first aspect of the present invention, a resistor having a lead conductor on both ends of a resistor body, a pair of pin electrodes, and a guide shaft are juxtaposed, and overcurrent heat is generated across one lead conductor of the resistor and the pair of pin electrodes. The overcurrent exothermic piece and the one lead conductor and the overcurrent exothermic piece and the pair of pin electrodes are respectively joined with a fusible alloy to melt the fusible alloy. The guide shaft in a state where a spring for detaching the overcurrent exothermic piece from the pair of pin electrodes and one lead conductor is compressed by a support plate supporting the overcurrent exothermic piece or the overcurrent exothermic piece. A resistor that is inserted through the resistor and causes the resistor body to generate heat and melt the soluble alloy between the other lead conductor of the resistor and one of the pair of pin electrodes when the protected device is abnormal. Connect the heat generation circuit. The features.
The protective element according to claim 2 is the protective element according to claim 1, wherein one lead conductor of the resistor main body is omitted, and one end of the resistor main body and the overcurrent exothermic piece are joined with a soluble alloy. It is characterized by.
According to a third aspect of the present invention, in the protective element according to the first or second aspect, the support plate is an insulator, and the support plate is slidably inserted into the guide shaft.
The protective element according to claim 4 is the protective element according to claim 1 or 3 , wherein the overcurrent exothermic piece is contacted with one end of the resistor main body through the hole in the center of the support plate and one of the protrusions penetrating the protrusion. A lead conductor insertion hole is provided, and one lead conductor and an overcurrent exothermic piece are joined by a soluble alloy at the boundary between the protrusion and one end of the resistor body, and each pin electrode is formed on a support plate. Through holes for receiving one end of each of these pins are provided, and in each of these holes, one end of each pin electrode and each end of the overcurrent exothermic piece are joined by a soluble alloy, and guide shaft insertion holes are formed at both ends of the support plate. And a spring is inserted through each guide shaft inserted through each guide shaft insertion hole.
The protection element according to claim 5 is the protection element according to any one of claims 1 to 4, wherein the other lead conductor of the resistor and the lead portion of the pair of pin electrodes are drawn from the pedestal, and the guide shaft is fixed to the pedestal. A case is mounted on the pedestal.
The protection element according to claim 6 is the protection element according to claim 5, wherein an insulator that changes color due to heat generation of the resistor body is provided to cover the resistor body and the pair of pin electrodes, and the case can be seen through. It is characterized by being.
The protective element according to claim 7 is the protective element according to any one of claims 1 to 6, which is for protecting the secondary battery, the overcurrent is the allowable load current of the secondary battery, and the abnormal battery It is overcharge or overdischarge, and the overcurrent is overcurrent when the secondary battery is discharged .
The protection element according to claim 8 is the protection element according to claim 7, wherein the amount of the fusible alloy that joins the pin electrode on the anode side during charging and the overcurrent exothermic piece is the same as that of the other pin electrode. It is characterized by being larger than the amount of the fusible alloy that joins the exothermic pieces.
A protection element according to claim 9 is the protection element according to any one of claims 1 to 8, characterized in that the fusible alloy is a Bi-based or Sb-based alloy.

(1) The location where the spring reaction force acts on the fusible alloy consists of two locations where each end of the overcurrent exothermic piece and each pin electrode are joined, and the intermediate portion of the overcurrent exothermic piece and the guide shaft. Since it is dispersed in a total of three places, one place to be joined, the stress acting on the fusible alloy can be reduced as compared with the case of one or two places. Therefore, creep of the fusible alloy can be reduced, and proper operation of the protective element can be ensured.
(2) When an overcurrent flows under direct current heating, the overcurrent exothermic piece generates heat, and the fusible alloy joining the overcurrent exothermic piece and the electrode is melted by the generated heat, and the stress of the spring With the energy, the overcurrent exothermic piece is detached from between the pin electrodes and the overcurrent is interrupted. In this case, even if the melting point of the fusible alloy has changed due to the migration, the resistance value of the overcurrent exothermic piece is set so that the exothermic temperature of the overcurrent exothermic piece takes into account the change. Thus, the overcurrent interruption can be surely performed.
(3) When an abnormality other than the overcurrent occurs in the protected device, the resistor is heated by energization, the fusible alloy is melted by the generated heat, and the overcurrent exothermic piece is moved between the pin electrodes by the stress energy of the spring. The power supply to the protected device is stopped after being detached. In this case, even if the melting point of the fusible alloy has changed due to the migration, the energization is cut off by setting the resistance value of the resistor so that the heating temperature of the resistor body takes into account the change. Can be performed reliably.
In this case, unlike the protective element shown in the figure, the spring is not moved between the resistor body and the overcurrent exothermic piece 3, but the spring is moved to another position, and each soluble alloy is moved from the resistor body. Therefore, the generated heat of the resistor body can be transferred to each soluble alloy as quickly as possible, and the operation can be speeded up.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1-1 (a) is a side view showing an embodiment of the protection element according to the present invention, and (b) in FIG. 1-1 is a cross-sectional view taken along line (b) in FIG. 1-1.
In FIG. 1-1, 10 is a heat-resistant insulating base, for example, a phenol resin base. Reference numerals 1 and 1 denote a pair of parallel pin electrodes, which are fixed to an insulating base 10 and lead parts 11 are drawn out from the base 10.
The pin electrode 1 can be made of copper or brass, and can be cylindrical, flat or the like, and is subjected to concave bending or bending on the resistor side so that it is easy to receive radiant heat from the resistor. Is preferred. Reference numeral 8 denotes a winding type or metal oxide film type resistor, and cap electrodes 801 (802) with lead conductors 80a (80b) are attached to both ends of a heat resistant insulating core such as a ceramic score, and resistance wires or metal oxides are attached to the core. A film is provided, and each end of the resistor is joined to each cap electrode 801, 802 by welding or the like, and is arranged between the pin electrodes 1, 1. The other cap electrode 802 of this resistor is brought into contact with the protrusion 101 at the center of the base, and the other lead conductor 80b is drawn from the insulating base 10 through the protrusion 101. Reference numeral 2 denotes an overcurrent exothermic piece, as shown in FIG. 1B, having a protrusion 20 on the back surface, a hole penetrating the protrusion 20, and one lead conductor of the resistor 8 in the through hole. 80a is inserted, the protrusion 20 and one cap electrode 801 of the resistor main body 80 are brought into contact with each other, and one lead conductor 80a and the overcurrent exothermic piece 2 are joined with the soluble alloy 3 at the contact point. At the same time, one half of one end face of each pin electrode 1 is brought into contact with the back surface of each end of the overcurrent exothermic piece 2, and the other half of one end face of each pin electrode and each end face of the overcurrent exothermic piece 2 are connected. Joined by a fusible alloy 3.

As shown in FIG. 1-2, the cavity 30 is formed by shaving the wall of the back surface protrusion 30 of the overcurrent exothermic piece 2, the overcurrent exothermic piece 2 is inserted into one lead conductor 80a, The cavity 30 is filled with a fusible alloy, and each end portion 200 of the overcurrent exothermic piece 2 and each of the overcurrent exothermic pieces 2 in a state where the protrusion 20 of the overcurrent exothermic piece 2 is in contact with one cap electrode 801 of the resistor body 80. The end surface of the pin electrode 1 is joined by the fusible alloy 3, and the fusible alloy in the cavity 30 is melted by heat at the time of joining, so that the overcurrent exothermic piece 2 and the one lead conductor 80a are fusible. Bonding with the alloy 3 can be performed.
In this case, it is necessary to support the compression reaction force of the springs 7 and 7 by pressing a support plate 4 described later until the soluble alloy is solidified. If the heat at the time of joining is transmitted to the springs 7 and 7, the spring characteristics are inevitably deteriorated. Therefore, the support plate is preferably a thermal insulator.

In FIG. 1A, reference numerals 6 and 6 denote guide shafts which are implanted in the spring supporters 102 and 102 of the base 10 with the resistor 8 and the pair of pin electrodes 1 and 1 interposed therebetween.
Reference numerals 7 and 7 denote springs inserted through the guide shafts 6 and 6, and slide the support plate 4 common to the one lead conductor 80 a and the pair of pin electrodes 1 and 1 and the guide shafts 6 and 6 of the resistor 8. The overcurrent exothermic piece 2 is supported by the support plate 4, and the compression reaction force of the springs 7, 7 is transmitted to the soluble alloys 3, 3, 3 via the support plate 4.

  As shown in FIG. 1-3, the support plate 4 has a hole 201 having a diameter slightly larger than the diameter of the protrusion of the overcurrent exothermic piece 2 and holes 101 and 101 having a diameter slightly larger than the diameter of the pin electrode. Holes 601 and 601 having a diameter slightly larger than the diameter of the guide shaft are provided. Instead of these holes, a single inner hole that is smaller than the outer shell of the overcurrent exothermic piece and encloses the hole in the figure can be provided in the support plate. In FIG. 1-1, 5 is a case and it is preferable to be able to see through.

In order to assemble the protection element, the springs 7 and 7 are inserted into the guide shafts 6 and 6, and the one lead conductor 80 a of the resistor 8 and the pair of pin electrodes 1 and 1 and the guide shafts 6 and 6 are supported by the support plate 4. In a state where the support plate 4 is pressed with a jig to support the compression reaction force of the spring, the overcurrent exothermic piece 2 is inserted into one lead conductor 80a, and the cavity 30 of the overcurrent exothermic piece 2 is inserted. Is filled with a fusible alloy, and the protrusion 20 of the overcurrent exothermic piece 2 is brought into contact with one cap electrode 801 of the resistor body 80, and then each end portion 200 of the overcurrent exothermic piece 2 and each pin electrode. 1 is welded to the end face of the meltable alloy 3, and the meltable alloy in the cavity 30 is melted by heat at the time of joining, so that the fusible alloy 3 of the overcurrent exothermic piece 2 and one of the lead conductors 80 a is melted. And wait for solidification of the fusible alloy to remove the jig and hold the support plate 4 It can be divided.
Instead of pressing the support plate with a jig, the overcurrent exothermic piece 2 is pressed with a heat insulating jig to support the compression reaction force of the spring 7, and in this state, each end 200 of the overcurrent exothermic piece 2 is supported. And the end surface of each pin electrode 1 are joined by a fusible alloy 3, and the fusible alloy in the cavity 30 is melted by the heat at the time of joining, so that the overcurrent exothermic piece 2 and one lead conductor 80 a Joining with the fusible alloy 3 can also be performed.

It is possible to integrate the overcurrent exothermic piece 2 and the support plate 4, omit the support plate, and provide a guide shaft insertion hole portion in the overcurrent exothermic piece. 1-4 shows an example of the arrangement of resistors, pin electrodes, and spring insertion guide shafts in the latter case. 1-4 (a), 4 is an overcurrent exothermic piece, 1, 1 is a pin electrode, 80a is one lead conductor of the resistor body or one cap electrode 801, 6 is a spring insertion guide shaft. The compression reaction force of the spring should be evenly distributed at the junction between the overcurrent exothermic piece and the pin electrode, and at the junction between the overcurrent exothermic piece and one lead conductor of the resistor body or one cap electrode. It is.
In this case, as shown in (b) of FIG. 1-4, the thermal insulation support plate 4 is inserted into the guide shaft 6 and the overcurrent exothermic piece 2 is disposed, and the overcurrent exothermic piece 2 is thermally insulated. It is also possible to perform the joining with the soluble alloy in a state where the compression reaction force of the presser spring 7 is supported by the tool.

Even if the spring 7 is inclined with respect to the guide shaft 6, it is preferable to allow play in the guide shaft insertion hole of the support plate so that the support plate 4 can be smoothly slid relative to the guide shaft 6 without being caught. For example, as shown in FIG. 1-5, the grooves 602 and 602 are preferable.
The support plate may be made of metal, but is preferably made of an insulator such as glass epoxy resin or ceramic.

  One lead conductor of the resistor is omitted, and a fusible alloy is inserted from the hole of the protrusion of the overcurrent exothermic piece 2, and the protrusion of the overcurrent exothermic piece 2 and one cap electrode 801 of the resistor 8 May be joined with a soluble alloy.

The protection element according to the present invention can be suitably used as a protection element of a secondary battery protection circuit.
In FIG. 2, E is a secondary battery, L is a load, S is a charging power source, sw is a switch such as a transistor, and T is an IC that detects a overcharge or overdischarge of the secondary battery and issues a switch-on signal. Each circuit is shown.
A shows a protection element according to the present invention, and has a configuration in which the lead portions 101 and 101 of the electrodes 1 and 1 and the other lead conductor 80b of the resistor main body 80 have three terminals.
When an overcurrent flows during discharge, the overcurrent exothermic piece 2 of the protection element A is heated to melt the low melting point fusible materials 3 and 3 to release the stress energy of the spring 7, and the overcurrent exothermic piece 2 is connected to the electrode 1. , 1 is disconnected to disconnect between the load L and the secondary battery E, and the switch sw is turned on by a signal from the IC circuit T in response to overdischarge of the secondary battery E, and the resistor body 80 is energized and heated by the secondary battery E, the low melting point soluble material 3 is melted by the generated heat, the compression stress energy of the spring 7 is released, and the overcurrent exothermic piece 2 is detached from between the electrodes 1 and 1. The secondary battery E and the load L are disconnected.
Furthermore, during charging, the switch sw is turned on by a signal from the IC circuit T for overcharging, and the resistor main body 80 is energized and heated by the secondary battery E or the charging power source S, and the low melting point soluble material 3 is generated by the generated heat. Is melted, the compressive stress energy of the spring 7 is released, and the overcurrent exothermic piece 2 is detached from the interelectrodes 1, 1 to cut off the secondary battery E and the charging power source S.

  In the secondary battery protection circuit, the polarity of both pin electrodes changes alternately at the time of charging and discharging, but the amount of electric power per hour is higher at the time of charging than at the time of discharging, and a low melting point is possible. DC migration of the molten alloy becomes a problem. However, the contact surface between the overcurrent exothermic piece and the pin electrode and the contact surface between the overcurrent exothermic piece projection and the cap electrode of the resistor body also serve as a current path at the fusible alloy joint, and flows into the fusible alloy. Since the current ratio is reduced, DC migration can be well suppressed, and for some DC migration, as described above, the spring stress of each soluble alloy can be sufficiently suppressed. Can be eliminated well.

  When an overcurrent flows under direct current heating, the overcurrent exothermic piece generates heat, and the fusible alloy that joins the overcurrent exothermic piece and the electrode is melted by the generated heat, and is overheated by the stress energy of the spring. The current exothermic piece is detached from between the pin electrodes and the overcurrent is interrupted. In this case, even if the melting point of the fusible alloy is increased by the migration, the resistance value of the overcurrent exothermic piece is set so that the overcurrent exothermic piece is heated to a temperature that accounts for the increased temperature. Therefore, overcurrent interruption can be surely performed. This resistance value is set by adjusting the thickness or material of the overcurrent exothermic piece.

  When an overcharge or overdischarge of the secondary battery occurs, the resistor heats up, the fusible alloy melts with the generated heat, and the overcurrent exothermic pieces are detached from the pin electrodes by the stress energy of the spring. Charging and power supply are stopped. In this case, even if the melting point of the fusible alloy changes due to the migration, the resistance value of the resistor is set so that the heating temperature of the resistor body is heated to a temperature that anticipates the change. Blocking can be performed reliably.

  In this case, in the protection element shown in FIG. 4, the spring 7 is interposed between the resistor body 80 and the overcurrent exothermic piece 3, but in the protection element according to the present invention, no spring is provided at this position. In addition, the spring is moved to another position and the distance from the resistor main body 80 to each of the fusible alloys 3, 3, 3 is shortened. Fast transmission and quick operation.

  In addition, there is no possibility of current bypassing the spring when the resistor is energized and heated (in the protective element shown in FIG. 4, the specific resistance value of the spring 7 is not so high compared to the lead conductor 80a of the resistor. 7, there is a possibility that current will bypass), and there is no deterioration of the spring characteristics due to energization heating of the spring, and good operability can be guaranteed.

  In the protective element according to the present invention, if a material that changes color due to heat generated by the resistor body is used for the heat-resistant insulating coating 800 and the case 5 can be seen through, whether the operation of the protective element is due to overcurrent or other than overcurrent. It is possible to easily determine whether it is due to an abnormality.

  In the protection element according to the present invention, in order to secure an insulation distance between each pin electrode 1, 1 and the other lead conductor 80b of the resistor, as shown in FIG. 11 can be pulled out from the side surface of the base 10.

In the protective element according to the present invention, when the surface area of the pin electrode is large, such as a flat plate, the heat dissipation becomes high, and heat from the resistor may escape and the operation may be delayed. As shown in FIG. 5, it is preferable to provide a portion having a small cross-sectional area by partially notching or drilling.

In the protection element according to the present invention, it is ideal that the entire current flows on one side of the overcurrent exothermic side and the current is not bypassed on the fusible alloy side, but a bypass of several percent to 30% is acceptable. . In this case, the amount of the fusible alloy that joins the pin electrode on the anode side and the overcurrent exothermic piece as a whole is larger than the amount of the fusible alloy that joins the other pin electrode and the overcurrent exothermic piece. Increasing the number is effective as a countermeasure against the migration.
A mark that can recognize this can be attached to the pin electrode that is on the anode side during charging.

1 is a view showing an embodiment of a protection element according to the present invention. It is drawing which shows the soluble alloy joining state in the protection element shown in FIG. It is drawing which shows an example of the support plate used with the protection element which concerns on this invention. It is drawing which shows the principal part of the Example different from the above of the protection element which concerns on this invention. It is drawing which shows an example different from the above of the support plate used with the protection element which concerns on this invention. It is drawing which shows the principal part of the Example different from the above of the protection element which concerns on this invention. It is drawing which shows the principal part of the Example different from the above of the protection element which concerns on this invention. It is drawing which shows the use condition of the protection element which concerns on this invention. 2 is a diagram illustrating a secondary battery protection circuit. 2 is a diagram illustrating a protective element that has been proposed by the present applicant.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Insulation base 1 Pin electrode 2 Overcurrent exothermic piece 3 Soluble alloy 4 Support plate 5 Case 6 Guide shaft 7 Spring 8 Resistor 80a One lead conductor of resistor 800 Insulation coating layer

Claims (9)

A resistor having a lead conductor on both ends of the resistor body, a pair of pin electrodes, and a guide shaft are juxtaposed, and an overcurrent exothermic piece is disposed across one lead conductor of the resistor and the pair of pin electrodes. The current exothermic piece and the one lead conductor and the overcurrent exothermic piece and the pair of pin electrodes are each joined by a fusible alloy, and when the fusible alloy melts, the overcurrent exothermic piece is A spring to be detached from a pair of pin electrodes and one lead conductor is inserted into the guide shaft in a state compressed by the overcurrent exothermic piece or the support plate supporting the overcurrent exothermic piece, and the other of the resistor A resistor heating circuit is connected between the lead conductor and one of the pair of pin electrodes to cause the resistor body to generate heat and melt the soluble alloy when the protected device is abnormal. Protective element. 2. The protective element according to claim 1, wherein one lead conductor of the resistor body is omitted, and one end of the resistor body and the overcurrent exothermic piece are joined by a soluble alloy. The protection element according to claim 1 or 2, wherein the support plate is an insulator, and the support plate is slidably inserted into the guide shaft. The overcurrent exothermic piece is provided with a projecting portion that contacts the one end of the resistor body through the hole in the center of the support plate and one lead conductor insertion hole that passes through the projecting portion. Joining with a fusible alloy is performed at the boundary between the projection and one end of the resistor body, and a through hole is provided in the support plate to accommodate one end of each pin electrode. One end and each end of the overcurrent exothermic piece are joined with a soluble alloy, guide shaft insertion holes are provided at both ends of the support plate, and a spring is inserted into each guide shaft inserted into each guide shaft insertion hole. The protective element according to claim 1 , wherein the protective element is formed. The other lead conductor of the resistor and the lead portion of the pair of pin electrodes are drawn out from the pedestal, the guide shaft is fixed to the pedestal, and a case is mounted on the pedestal. Or a protective element. 6. The protective element according to claim 5, wherein an insulator that changes color due to heat generated by the resistor body is provided to cover the resistor body and the pair of pin electrodes, and the case can be seen through. It is for protection of a secondary battery, the time of abnormality is the time of overcharge or overdischarge of the secondary battery, and the overcurrent is an overcurrent at the time of secondary battery discharge. Any protection element. The amount of the fusible alloy joining the pin electrode on the anode side during charging and the overcurrent exothermic piece is made larger than the amount of the fusible alloy joining the other pin electrode and the overcurrent exothermic piece. The protective element according to claim 7, wherein The protective element according to claim 1, wherein the fusible alloy is a Bi-based or Sb-based alloy.

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