JP4757931B2 - Protective element - Google Patents

Description

  The present invention relates to a protective element useful for interrupting overcurrent to a high capacity secondary battery, for example, a high capacity lithium ion secondary battery, and stopping charging or discharging during overcharge or overdischarge.

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-type thermal fuse and a resistor that are collectively brought into close proximity are known.
FIG. 5 shows an example of a secondary battery protection circuit.
In FIG. 5, 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 it moves to the anode interface, and the pores coalesce at the interface to generate cracks.

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 about 200 μm was deposited in contact with the electrode, and a gap having a thickness of about 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 about 50 μm was deposited in contact with the end surface of the copper, and a void having a thickness of about 20 μm was formed in contact with the end surface of the copper lead conductor on the anode side.

  In FIG. 5, “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.).

  Thus, in FIG. 5, the polarity of the both end electrodes of the low melting point alloy fuse 30 ′ changes at the time of charging and discharging, but assuming rapid charging, the amount of power per hour is higher at the time of charging. Since it becomes larger than that at the time of discharge, migration of the low melting point alloy fuse 30 ′ is difficult to avoid.

An object of the present invention is to provide a protection element with a resistor that can protect a device to be protected used under a direct current against overcurrent by eliminating migration of a low melting point alloy.
It is a further object of the present invention to provide a protection element with a resistor that can protect a device to be protected used under a direct current from an abnormality other than an overcurrent by eliminating migration of a low melting point alloy. is there.

The protection element according to claim 1 has a pair of pin electrodes, a guide shaft is juxtaposed with these pin electrodes, and an overcurrent exothermic piece that generates heat when energized with an overcurrent is inserted through the guide shaft Arranged between the tips of the pair of pin electrodes, and between each pin electrode and the overcurrent exothermic piece and between the guide shaft and the overcurrent exothermic piece are joined with a low melting point soluble material, A spring holding a compression reaction force that separates the overcurrent exothermic piece from the pin electrode is provided, a pin electrode leg is led out and covered with a case, and the spring strain energy based on the compression reaction force is The lower end position of the first amplitude of vibration at the upper end of the spring generated by the melting of the low melting point soluble material is 0 in the pin electrode direction from the guide shaft tip, where h is the distance between the pin electrode tip and the guide shaft tip side case inner surface. .Spring to be located within 8h In the configuration compression reaction force is set, resistor resistor lead conductor becomes attached to the opposite ends of the body are added, one lead conductor of the resistor is used as a guide shaft, the compression coil spring resistor The guide shaft is inserted between the main body and the overcurrent exothermic piece, and the resistor is energized and heated between the other lead conductor of the resistor and either of the pin electrodes when the protected device is abnormal. A resistance heating circuit for melting the low melting point soluble material is connected.
In the protective element according to claim 2 , in the protective element according to claim 1 , since the overcurrent exothermic piece remains in contact with the bundle after colliding with the ceiling in the case, the upper end of the amplitude is saturated and linearized. It is characterized by.
The protection element according to claim 3 has a pair of pin electrodes, a guide shaft is juxtaposed with these pin electrodes, and an overcurrent exothermic piece that generates heat when energized with an overcurrent is inserted through the guide shaft Arranged between the tips of the pair of pin electrodes, and between each pin electrode and the overcurrent exothermic piece and between the guide shaft and the overcurrent exothermic piece are joined with a low melting point soluble material, A spring holding a compression reaction force that separates the overcurrent exothermic piece from the pin electrode is provided, the pin electrode leg is led out and covered with a case, and the spring strain energy based on the compression reaction force has a low melting point The overcurrent exothermic piece released by melting of the fusible material and moved to the upper end portion of the guide shaft is provided with means for retaining at the upper end portion thereof.
The protection element according to claim 4 is the protection element according to claim 3, wherein a resistor having lead conductors attached to both ends of the resistor body is added, and one lead conductor of the resistor is used as a guide shaft. The compression coil spring is inserted into the guide shaft between the resistor main body and the overcurrent exothermic piece, and between the one lead conductor of the resistor derived from the case and either of the pin electrodes, A resistance heating circuit is connected to cause the resistor to generate heat when abnormal and melt the low melting point soluble material.
The protection element according to claim 5 is the protection element according to claim 4 , wherein the spring strain energy based on the compression reaction force is released by melting of the low melting point soluble material and moved to the upper end portion of the guide shaft. The means for fastening the piece to the upper end portion thereof is a taper portion or a twist portion provided at the upper end portion of the guide shaft.
Protection device according to claim 6 is in claim 1, 2, 4 What Re of the protective element, the overcurrent exothermic piece disc, oval, or a flat-shaped end portions arc, pin electrodes Has a circular arc shape on the outer surface that fits the outer circumference of the circular overcurrent exothermic piece, and the tip of the pin electrode is joined with a low melting point soluble material at the location facing the outer circumference of the circular overcurrent exothermic piece. A heat-conductive electrical insulating material is interposed in the gap between the inner surface and the resistor body by filling, applying to the resistor body, or arranging a molded product.
Protection device according to claim 7, in claim 6 What Re of the protective element, the case is characterized in that it is a horizontally or vertically the two-piece or locked to each other.
Protection device according to claim 8, in claims 1-7 What Re of the protective element, and wherein the low-melting-friendly welding material is an alloy that does not contain lead.
Protection device according to claim 9, in claim 8 something Re of the protective element, the low-melting-friendly welding material is quantified mounted on overcurrent exothermic piece, overcurrent exothermic piece by reflow and the pin electrodes and the guide shaft And is joined.
Protection device according to claim 10, in claim 1,2,4～9 what Re of the protective element, is for the protection of a secondary battery, abnormality is a time of overcharge or overdischarge of the secondary battery And the overcurrent is an overcurrent when the secondary battery is discharged .

(1) The location where the spring reaction force acts on the low melting point soluble material is the 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. Therefore, the stress acting on the low melting point soluble material can be reduced as compared with the case of 1 to 2 places. Therefore, creep of the low melting point soluble material 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 low melting point fusible material joining the overcurrent exothermic piece and the electrode is melted by the generated heat, and the spring With the stress energy, the overcurrent exothermic piece is detached from between the pin electrodes and the overcurrent is interrupted. Therefore, in normal times, the flow of direct current to the low melting point fusible material is substantially less than that using the conventional linear fuse element, and DC migration of the low melting point fusible material can be eliminated well. Overcurrent can be properly cut off by eliminating the malfunction based on the above.
(3) When an abnormality other than the overcurrent occurs in the protected device, the resistor is heated by energization, the low melting point fusible material is melted by the generated heat, and the overcurrent exothermic piece is formed between the pin electrodes by the stress energy of the spring. Power supply to the protected device is stopped. Therefore, as explained in (1), the flow of direct current to the low melting point soluble material is substantially small during normal times, and the direct current migration of the low melting point soluble material can be well eliminated. Therefore, it is possible to properly cut off the power supply when the protected device is abnormal.
(4) Since the spring is released from the compression reaction force due to the melting of the low melting point soluble material, the overcurrent exothermic piece moves along the guide shaft and collides with the upper surface in the case, and the spring receives the compression reaction force. The upper end of the spring vibrates. This vibration is a damped vibration, and the overcurrent exothermic piece finally stops at the position of the ceiling in the case. This ceiling position is set so that the melted low melting point soluble material can be cut without stringing. The amplitude is determined by the stored strain energy of the spring, and therefore the initial compression reaction force of the spring, and the lower end position of the first amplitude is the distance from the pin electrode tip to the guide shaft tip side case inner surface from the guide shaft tip to the pin electrode direction. Since the compression reaction force of the spring is set sufficiently high so as to be located at a height within 0.8 h, the overcurrent exothermic piece can be quickly detached from the pin electrode when the low melting point soluble material is melted, In addition, re-contact between the overcurrent exothermic piece and the molten low melting point soluble material at the tip of the pin electrode can be reliably prevented. Therefore, reliable and quick power interruption can be guaranteed.

1 is a view showing an embodiment of a protection element according to the present invention. It is drawing which shows the stress state in the protection element shown in FIG. It is explanatory drawing which shows the vibration state of the spring upper end based on fusion | melting of the low melting-point soluble material of the protection element shown in FIG. It is a longitudinal cross-sectional view which shows another Example of the protection element which concerns on this invention. 3-2 (a) is a drawing showing the mounting state of the spring in FIG. 3-1, (b) in FIG. 3-2 is a cross-sectional view in FIG. 3-1, and (c) in FIG. 3-2. FIG. 3 is a cross-sectional view of FIG. It is drawing which shows the mounting state of the spring different from the above of the protection element which concerns on this invention. It is drawing which shows an example of the division | segmentation case used in 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.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A is a longitudinal sectional view showing an embodiment of the protective element according to the present invention, and FIG. 1B is a cross-sectional view of FIG.
In FIG. 1, 10 is a heat-resistant insulating base, for example, a phenol resin plate. Reference numerals 1 and 1 denote a pair of parallel pin electrodes which are inserted and fixed to the insulating base 10. This pin electrode can be made of copper, tin-plated brass, or the like. Reference numeral 6 denotes a guide shaft which can use a metal body and is arranged in parallel to the pin electrodes 1 and 1 and fixed to the base 1. 2 is an overcurrent exothermic piece, and a metal plate that is thinner than the cross section of the pin electrode 1 or an alloy plate that has a higher specific resistance than the pin electrode 1 can be used. A hole 21 is provided in the overcurrent exothermic piece 2 and is inserted through the guide shaft 6.
3 is a low melting point soluble material in which the overcurrent exothermic piece 2 and each of the pin electrodes 1 and 1 and between the overcurrent exothermic piece 2 and the guide shaft 6 are joined. A thermoplastic resin or the like can be used.
Reference numeral 7 denotes a coil spring. For example, a stainless spring can be used. The spring 7 and the overcurrent exothermic piece 2 are sequentially inserted into the guide shaft 6, and both ends of the overcurrent exothermic piece 2 are connected to the pin electrodes 1, 1. The coil spring 7 is compressed while being brought into contact with the tip surface, and in this state, between the tip surface of each pin electrode 1, 1 and each end of the overcurrent exothermic piece 2, the overcurrent exothermic piece 2 and the guide shaft 6 Are joined by a low melting point soluble material 3.
Reference numeral 5 denotes an insulator case, and the tip of the guide shaft 6 terminates at the ceiling inside the case.

If the mechanical state based on the spring reaction force in the above is simplified, the compression spring as shown in FIG. 2 (a) [sectional view] and FIG. 2 (b) [top view with respect to FIG. 2 (a)]. 7, the shear stress F acts on the cross-section SS of the low melting point fusible material joining each pin electrode and the overcurrent exothermic piece to cause the overcurrent exothermic piece and the guide shaft. Can be brought into a state in which the shear stress f acts on the interface s-s of the low-melting-point soluble material.
In FIG. 2, the area of the cross section SS is S, the area of the interface s-s is s, the compression reaction force of the compression spring 7 is T, and the low melting point soluble material between the overcurrent exothermic piece 2 and the guide shaft 6. 3 where the thickness of the portion where the shear force acts is t, the height is b, and the shear Young's modulus of the low melting point soluble material is G.
2SF + sf = T
F / G = ft / G
Is established.
Since the area s of the interface s−s is s≈2πrb, where r is the radius of the guide shaft, the stress F is given by [Expression 1] F≈0.5 T / [S + (πrb) / (t) ]
Given in.

  In Equation 1, the radius r of the guide shaft contributes to the reduction of the stress F because the overcurrent exothermic piece 2 and the guide shaft 3 are joined with a low melting point soluble material. The shear stress F acting on the low melting point soluble material portion SS joining the exothermic piece 2 can be reduced by increasing the radius r, and the creep at the low melting point soluble material portion SS can be well prevented. Therefore, the electrical contact state between the pin electrodes 1 and 1 and the overcurrent exothermic piece 2 can be stably maintained.

In FIG. 1, when the low melting point soluble material 3 is melted, the strain energy based on the initial compression reaction force of the spring 7 is released, and the overcurrent exothermic piece 2 finally extends to the position of the ceiling in the case. Pressed and fixed with considerable compressive stress. The distance h between the position of the fixed overcurrent exothermic piece and the tip of the pin electrode 1 is uniquely set so that the molten low melting point soluble alloy can be cut continuously without stringing. Even when the sex piece comes into contact with the ceiling in the case, the spring is in a considerably compressed state. Therefore, the overcurrent exothermic piece collides with the ceiling inside the case due to melting of the low melting point soluble material, and the compression reaction force acts on the spring by this collision, and the tip of the spring is displaced in the time-dependent state shown in FIG. Even if the spring stretches and the overcurrent exothermic piece contacts the ceiling inside the case, the spring does not move to contract instantly due to elasticity, but the spring after the overcurrent exothermic piece at the tip of the spring contacts the ceiling inside the case. Although it is between the bundles until the contraction starts, time Δt elapses, and the upper end of the amplitude becomes a saturation straight line. In FIG. 1, since the interval between the initial position of the spring tip and the ceiling in the case is uniquely set as described above, the amplitude of the spring vibration is determined by the initial strain energy of the spring, and hence the initial compression reaction force. Accordingly, the lower end position of the first amplitude is set so that the distance between the tip of the pin electrode and the guide shaft tip side case inner surface is h, and is positioned at a height within 0.8 h from the guide shaft tip to the pin electrode direction. The compression reaction force is set sufficiently high, the molten low melting point soluble alloy can be quickly shut off by the spring force, and the overcurrent exothermic piece and the molten low melting point soluble material at the tip of the pin electrode are reliably recontacted. Can be prevented. Accordingly, it is possible to guarantee quick and reliable energization interruption due to overcurrent exothermic piece separation.
Moreover, when using on the conditions that an arc generate | occur | produces at the time of interruption | blocking, an arc-extinguishing agent can also be added.

  Instead of regulating the initial compression reaction force of the spring, a means for holding the overcurrent exothermic piece that has reached the ceiling in the case due to melting of the low melting point soluble material to the upper end of the guide shaft may be provided. As a means for securing the overcurrent exothermic piece that has reached the ceiling inside the case to the upper end of the guide shaft, a taper convex portion is provided at the upper end of the guide shaft, and the hole of the overcurrent exothermic piece beyond the taper convex portion is tapered. A structure that supports the overcurrent exothermic piece by hooking it to the step, a structure that twists the upper end of the guide shaft and prevents the overcurrent exothermic piece from falling over the torsion part, elastic check pawl, overcurrent heat generation The structure which attaches a magnetic body to a sex piece, and arrange | positions a magnet to the ceiling in a case, the structure which attaches an adhesive material etc. to the ceiling in a case, etc. can be enumerated.

  The dimensions of soldering (low melting point soluble material) are set so that the shear stress F of Formula 1 is a safe value with respect to the initial compression reaction force T of the spring.

  For the low melting point soluble material, a solder can be suitably used. In particular, a lead-free solder, for example, a lead-free solder containing at least one of Sn and In, a lead-free solder containing Bi, and Sb are also included. Lead-free solder can be used. If the amount of the low melting point soluble material is insufficient, the predetermined bonding strength cannot be ensured, and if the amount is excessive, stringing is likely to occur at the time of melt cutting, so high precision management of the amount of the low melting point soluble material is required. Is done. Thus, a low melting point fusible alloy is quantitatively supplied to a predetermined portion of the overcurrent exothermic piece with a high precision jig, a pin electrode is positioned on the overcurrent exothermic piece, a guide shaft is inserted, and then It is preferable to use a method of melting a low melting point soluble alloy by heating, that is, a reflow method.

FIG. 3A is a longitudinal sectional view showing another embodiment of the protective element according to the present invention. 3-2 (a) is the initial setting state of the spring, FIG. 3-2 (b) is a cross-sectional view of FIG. 3-1, and FIG. 3-2 (c) is FIG. 3-1. The ha sectional drawing in each is shown.
In FIG. 3-1, 10 is a heat-resistant insulating base, for example, a phenol resin plate. Reference numerals 1 and 1 denote a pair of parallel pin electrodes, in which a leg portion 100 is formed by right-angle bending, and an assembly-type insulating base 10 is assembled so as to embrace the pin electrode leg portion 100. This pin electrode can be made of copper. 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, for example, a ceramic score, resistance wires are wound around the core, and each winding end is welded to each cap electrode 801,801. The lead conductors 80 a are used as the guide shaft 6, and are arranged in parallel between the pin electrodes 1 and 1. The other lead conductor 80 b is drawn from the insulating base 10. The other lead conductor 80 may be a flexible conductor and an insulation-coated electric wire, or may be pulled out by being joined to another conductor such as a metal plate by a method such as welding.
Reference numeral 2 denotes an overcurrent exothermic piece, which is inserted in the hole through the guide shaft 6 (80a) and placed between the pin electrodes 1 and 1 with a sufficiently low resistance electrically. Compared to the electrode 1, an alloy plate having a higher specific resistance than the electrode 1 can be used. 3 is a low melting point soluble material in which the overcurrent exothermic piece 2 and each of the pin electrodes 1 and 1 and between the overcurrent exothermic piece 2 and the guide shaft 6 (80a) are joined. Or a conductive thermoplastic resin can be used. Reference numeral 7 denotes a spring, for example, a stainless spring, which is inserted into the guide shaft 6 (80a) in a compressed state between the overcurrent exothermic piece 2 and one end of the resistor body, and when the low melting point soluble material 3 is melted. The overcurrent exothermic piece 2 has a stress energy that can be detached from the pin electrodes 1 and 1. Insulating spacer provided with a central convex portion that can be closely attached to the spring, as shown in FIG. 3B, in order to eliminate the contact between the spring and the guide shaft by concentrating the spring on the guide shaft. 900 (for example, made of ceramics) is tightly inserted through the guide shaft 6 (80a).

  The overcurrent exothermic piece 2 can be a disk as shown in FIG. 3-2 (B), or can be an oval shape or a flat shape of both end arcs. It can also be in the form of an arc that is flush or fits around the outer periphery of the current exothermic piece.

Further, as shown in FIG. 3-2 (C), a heat-conductive insulating material 800 is inserted into the gap between the pin electrodes 1 and 1 and the resistor body 8 from the gap between the pair of pin electrode electrodes 1 and 1. For example, a curable resin containing an inorganic powder filler such as silica sand, for example, a silicone resin, an epoxy resin, or the like can be injected and filled. With this configuration, the heat generated later of the resistor body 8 can be quickly transmitted to the low melting point soluble material via the pin electrodes 1 and 1.

In the protection element shown in FIG. 3A, the resistance heating circuit including the lead conductor 4 → the pin electrode 1 → the overcurrent exothermic piece 2 → the lead conductor 80a → the resistor 8 → the lead conductor 80b The resistor 8 is energized to generate heat and the generated heat melts the low-melting-point soluble materials 3, 3, 3, and the pin electrodes 1, 1 are disconnected. Accordingly, the specific resistance value of the spring 7 such as a stainless spring is not so high as that of the lead conductor 80a, and after the resistance heating circuit is turned on, the pin electrode 1 → Since the current flows through the path of the overcurrent exothermic piece 2 → spring 7 → resistor cap electrode 801 → resistor 8 and the spring 7 generates heat, the deterioration of the spring characteristics may hinder the operation of the protective element. As shown in FIG. 3-2 (A), a spacer 900 is used as an insulator, and a plate-like insulating spacer 901 is interposed between the overcurrent exothermic piece 2 and the spring 7. In addition, the insulating spacer 901 suppresses the inflow of the fusible material to the position where the spring contacts the overcurrent exothermic piece when joining the low melting point fusible material, and ensures the insulation distance between the spring and the fusible material. It plays a role to let you.
As shown in FIG. 3C, insulating spacers 901 and 902 may be interposed between the spring 7 and the overcurrent exothermic piece 2 or between the spring 7 and the resistor cap electrode 801. Both of these insulating spacers 901 and 902 can be interposed. Further, instead of the insulating spacer 902, the resistor cap electrode 801 can be coated with an insulating film.
Further, since the upper end inner periphery and the lower end inner periphery of the spring 7 may come into contact with the lead conductor 8a due to the inclination of the spring 7, there is a possibility that the current bypasses the spring 7. Therefore, between the inner side of the spring 7 and the lead conductor 8a. It is safer to interpose the insulating cylinder 9.

In the protection element according to the present invention, the shape of the overcurrent exothermic piece can be appropriately set such as a strip or a circle, and the cross-sectional shape of the pin electrode can be appropriately set accordingly.
For example, as shown in FIG. 3-4, the case can be divided into left and right or upper and lower parts, and both pieces can be joined by a male side claw and a female side groove, and the material is plastic, such as polycarbonate, PPS, PBT. It can be. Moreover, it can also be set as the structure more than three divisions.
Applying a flux to the low melting point soluble material joint is advantageous in preventing stringing of the soluble material. In this case, the case has a sealed structure.

The protection element according to the present invention can be suitably used as a protection element of the secondary battery protection circuit shown in FIG.
In FIG. 4, 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 conductors 4 and 4 connected to the electrodes 1 and 1 and the other lead conductor 80b of the resistor 8 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 soluble material 3, the stress energy of the spring 7 is released, and the overcurrent exothermic piece 2 is connected to the electrodes 1, 1. The load L and the secondary battery E are disconnected from each other, 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 turned on. The secondary battery E is energized to generate heat, melts the low melting point soluble material 3 with the generated heat, releases the compression stress energy of the spring 7 and detaches the overcurrent exothermic piece 2 from between the electrodes 1 and 1 to form the secondary battery. Block between E and load L.
Further, at the time of charging, for overcharging, the switch sw is turned on by a signal from the IC circuit T, the resistor 8 is 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. Melting is performed to release the compressive stress energy of the spring 7, and the overcurrent exothermic piece 2 is detached from the electrodes 1, 1 to cut off the secondary battery E and the charging power source S.

In the secondary battery protection circuit, the polarities of both pin electrodes change alternately at the time of charging and discharging, but the amount of electric power per time is larger at the time of charging than at the time of discharging. However, since the electrical continuity between each pin electrode and the overcurrent exothermic piece is well secured for electrical contact, the flow of DC current to the low melting point soluble material is considerably less, and the low melting point melting material alloy DC migration can be eliminated.
When an overcurrent flows, the overcurrent exothermic piece generates Joule heat, the low melting point soluble material is melted by the generated heat, the spring is released, and the overcurrent exothermic piece is detached from between the electrodes by the retained stress energy. To be released. Therefore, the DC overcurrent can be properly cut off.
If overcharging occurs during charging or overdischarging occurs during discharging, the resistor generates heat, the low melting point soluble material is melted by the generated heat, the spring is released, and the overcurrent exothermicity is generated by the retained stress energy. The piece is detached from between the electrodes, and the secondary battery and the charging power source or the secondary battery and the load are interrupted. Therefore, the secondary battery can be properly protected from overcharge or overdischarge abnormality.

The pin electrode 1 is made of copper and can be coated with Sn or an Sn-based alloy to prevent oxidation of the surface.
In this copper pin electrode, copper diffuses and migrates to the low melting point alloy soluble material 3 at the joint interface with the low melting point alloy soluble material 3, the mechanical strength of the low melting point alloy soluble material 3 is lowered, and the melting temperature fluctuates. Therefore, a portion of the pin electrode 1 to be bonded to at least the low-melting-point alloy soluble material 3, preferably a copper migration blocking film such as Ni, Ni-P, Ni-B, At least one or more films of Fe, Pd, and Pd—P can be provided between the Sn or Sn-based alloy coating layer.
The overcurrent exothermic piece 2 may be made of copper or a copper alloy such as brass, and may be coated with an Sn or Sn-based alloy to prevent surface oxidation. In order to prevent copper from diffusing and transferring from the overcurrent exothermic piece 2 to the low melting point alloy soluble material 3 that joins the overcurrent exothermic piece 2 and the pin electrode 1, at least the low current exothermic piece 2 is low. An alloy in which at least one layer of Ni, Ni-P, Ni-B, Fe, Pd, and Pd-P is Sn or Sn-based at the portion to be joined to the melting point alloy soluble material 3 It can provide between coating layers. Further, in order to prevent copper from diffusing and transferring from the overcurrent exothermic piece to the low melting point alloy soluble material 3 for joining the guide shaft 6 or the lead conductors 80a, 80b of the resistor and the overcurrent exothermic piece 2, A copper migration blocking film can be provided on at least a portion of the overcurrent exothermic piece 2 to be joined to the low melting point alloy soluble material 3. It is preferable to provide a copper migration blocking film on the entire surface of the overcurrent exothermic piece 2.
The guide shaft 6 or the lead conductors 80a, 80b of the resistor has a high resistance value of the resistor. Therefore, the copper wire, the copper alloy wire, the nickel wire, the iron wire, or the composite wire in which the copper layer is coated (whatever Alternatively, Sn or an alloy based on Sn can be coated on the outermost layer), and in this case, the guide shaft 6 or the lead conductor 80a is joined to at least the low melting point alloy soluble material 3. A portion, preferably a copper migration prevention film, for example, at least one film of Ni, Ni-P, Ni-B, Fe, Pd, Pd-P is formed on the entire surface of the overcurrent exothermic piece 2 by Sn or Sn group It is also possible to provide an alloy as described above between the coating layer.
By providing these intermediate layers, the strength of the lead fixing electrode is increased, and there is an advantage that the fatigue resistance is improved. There is also an advantage that Sn whisker growth can be suppressed from Sn or an alloy based on Sn.

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 low melting point soluble material side, but a bypass of several percent to 30% is acceptable. The In this case, the amount of the low-melting-point alloy soluble material that joins the pin electrode on the anode side and the overcurrent exothermic piece during charging is the same as the low-melting-point alloy soluble material that joins the other pin electrode and the overcurrent exothermic piece. It is effective as a countermeasure against the migration to increase the amount of the above.
A mark that can recognize this can be attached to the pin electrode that is on the anode side during charging.

DESCRIPTION OF SYMBOLS 10 Insulation base 1 Electrode 2 Overcurrent exothermic piece 21 Hole 3 Low melting point soluble material 4 Lead wire 5 Case 6 Guide shaft 7 Spring 8 Resistor 80a One lead conductor (guide shaft) of a resistor
800 Thermally conductive insulation

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

Claims (10)

It has a pair of pin electrodes, and guide shafts are arranged in parallel to these pin electrodes, and an overcurrent exothermic piece that generates heat when energized with an overcurrent is inserted between the tip ends of the pair of pin electrodes. Between each pin electrode and the overcurrent exothermic piece and between the guide shaft and the overcurrent exothermic piece with a low melting point soluble material, and the overcurrent exothermic piece is connected to the pin A spring holding a compression reaction force that separates from the electrode is provided, the pin electrode leg is led out and covered with a case, and the spring strain energy based on the compression reaction force is released by melting of the low melting point soluble material. The lower end position of the first amplitude of the vibration of the upper end of the spring generated is located at a height within 0.8 h from the guide shaft tip to the pin electrode direction, where h is the distance between the pin electrode tip and the guide shaft tip side case inner surface. compression reaction force of the spring is set such In adult, across the resistor body comprising a lead conductor is attached resistor is added, one of the lead conductors of the resistor is used as a guide shaft, a compression coil spring resistor body and overcurrent exothermic piece Between the other lead conductor of the resistor led out from the case and either one of the two pin electrodes and energized when the protected device is abnormal, and the resistor is energized to generate heat. A resistance heating circuit for melting the low melting point soluble material is connected. The protective element according to claim 1 , wherein the upper end of the amplitude is saturated and linearized so that the overcurrent exothermic piece remains in contact with the bundle after colliding with the ceiling in the case . It has a pair of pin electrodes, and guide shafts are arranged in parallel to these pin electrodes, and an overcurrent exothermic piece that generates heat when energized with an overcurrent is inserted between the tip ends of the pair of pin electrodes. Between each pin electrode and the overcurrent exothermic piece and between the guide shaft and the overcurrent exothermic piece with a low melting point soluble material, and the overcurrent exothermic piece is connected to the pin A spring holding a compression reaction force that separates from the electrode is provided, the pin electrode lead portion is led out and covered with a case, and the spring strain energy based on the compression reaction force is released by the melting of the low melting point soluble material to guide A protective element characterized in that means for holding the overcurrent exothermic piece moved to the upper end of the shaft at the upper end is provided. 4. The protection element according to claim 3, wherein a resistor having lead conductors attached to both ends of the resistor body is added, one lead conductor of the resistor is used as a guide shaft, and a compression coil spring is connected to the resistor body. A current is passed between one of the lead conductors of the resistor and either of the pin electrodes that are inserted into the guide shaft between the overcurrent exothermic pieces and led out from the case, and the resistor is energized. And a resistance heating circuit for melting the low melting point soluble material by applying heat to the protective element. The upper end of the guide shaft is provided with means for holding the overcurrent exothermic piece released to the upper end of the guide shaft by the spring strain energy based on the compression reaction force released by the melting of the low melting point soluble material. The protection element according to claim 4 which is a taper part or a twist part. The overcurrent exothermic piece is a disc, oval shape, or a flat shape with circular arcs at both ends, and the pin electrode has an outer cross-section arc shape that fits the outer periphery of the circular overcurrent exothermic piece, and the circular overcurrent exothermic piece The tip of the pin electrode is joined with a low-melting-point soluble material at the location facing the outer periphery, and a heat-conducting electrical insulating material is filled in the gap between the inner surface of each pin electrode and the resistor body or applied to the resistor body. The protective element according to claim 1 , wherein the protective element is interposed by arrangement of a molded product or the like. The protective element according to any one of claims 1 to 6 , wherein the protective element is divided into two or more of right and left or upper and lower where the case is locked to each other. The protective element according to claim 1, wherein the low melting point soluble material is an alloy containing no lead. Low melting-friendly welding material is quantified mounted on overcurrent exothermic pieces, reflowed by the joining of the overcurrent exothermic piece and the pin electrodes and the guide shaft is characterized in that it is carried out according to claim 1 to 8, wherein either Protective element. It is for protection of a secondary battery, the abnormal time is when the secondary battery is overcharged or overdischarged, and the overcurrent is an overcurrent when the secondary battery is discharged. The protective element in any one of 4-9 .

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