JP7416413B2 - protection element - Google Patents

Description

The present invention relates to a protection element.

Patent Document 1 discloses an invention related to a protection element. The protection element according to Patent Document 1 includes a pair of electrodes, a heating element, a bonding material, and an elastic body. The pair of electrodes are arranged to face each other. The heating element is arranged across the pair of electrodes. A heating element generates heat when current flows through it. The bonding material bonds the heating element to each of the pair of electrodes. The elastic body is placed between the pair of electrodes. The elastic body applies a separating force to the heating element. The separation force is the force in the direction that causes the heating element to separate from the pair of electrodes. The bonding strength of the bonding material falls below a predetermined strength at a predetermined temperature. The predetermined temperature is the temperature reached by the heat generated by the heating element. The predetermined strength is the strength that can withstand the separation force. The protection element according to Patent Document 1 further includes a shielding insulator and a magnetic force generating section. The shielding insulator is arranged between the pair of electrodes so as to shield the other when viewed from one side of the pair of electrodes. The magnetic force generation section generates magnetic force between the pair of electrodes in advance. The protection element disclosed in Patent Document 1 is capable of passing a large current at a larger voltage than conventional protection elements.

Japanese Patent Application Publication No. 2013-98134

However, there is a need for further improvement in the reliability of operation of protection elements in high-temperature environments. The present invention solves these problems. An object of the present invention is to provide a protection element with higher operational reliability under high temperature environments.

The protection element of the present invention will be explained based on the drawings. Note that the reference numerals in the figures are used in this column to aid understanding of the content of the invention, and are not intended to limit the content to the illustrated range.

In order to solve the above problems, according to an aspect of the present invention, the protection element 10 includes a pair of electrodes 22 and 24, a heating element 26, a bonding material 28, an elastic body 32, and a magnetic force generating section 38. Equipped with The pair of electrodes 22, 24 face each other. A heating element 26 is disposed straddling the pair of electrodes 22, 24. The heating element 26 generates heat when current flows therethrough. Bonding material 28 bonds heating element 26 to each pair of electrodes 22 and 24. Elastic body 32 is placed between the pair of electrodes 22,24. The elastic body 32 applies a separating force to the heating element 26 . The magnetic force generating section 38 generates a magnetic force between the pair of electrodes 22 and 24 in advance. The separation force is the force that causes the heating element 26 to separate from the pair of electrodes 22, 24. The bonding strength of the bonding material 28 falls below a predetermined strength at a predetermined temperature. The predetermined temperature is the temperature reached by the heat generated by the heating element 26. The predetermined strength is the strength that can withstand the separation force. The magnetic force generating section 38 includes a samarium cobalt magnet 50, a magnet accommodation space forming section 90, and a filler 54. The magnet accommodating space forming section 90 forms a magnet accommodating space. A samarium cobalt magnet 50 is housed in the magnet housing space. The filler 54 is housed together with the samarium cobalt magnet 50 in the magnet housing space. The filler 54 is filled in the gap between the samarium cobalt magnet 50 and the magnet accommodation space forming part 90.

When an overcurrent flows through the heating element 26 disposed across the pair of electrodes 22 and 24, the heating element 26 generates heat. When the bonding material 28 reaches a predetermined temperature due to the heat generated by the heating element 26, the bonding strength of the bonding material 28 falls below the predetermined strength. If the bonding strength of the bonding material 28 falls below a predetermined strength, the bonding material 28 will no longer be able to withstand the separation force. The heating element 26 is separated from the electrodes 22 and 24 by the elastic body 32 because it cannot withstand the separation force. This cuts off the current between the electrodes 22 and 24. When an arc is generated between the electrodes 22 and 24 after the current is cut off, the arc is subjected to Lorentz force by the magnetic force generated by the magnetic force generator 38. The arc extends by receiving the Lorentz force. When the arc extends, the arc voltage increases compared to when it does not extend. Additionally, the arc is cooled by being extended. The arc becomes difficult to sustain due to the synergistic effect of the increase in arc voltage and the cooling of the arc. As a result, it becomes possible to flow a large current with a large voltage. The samarium cobalt magnet 50 included in the magnetic force generating section 38 has superior performance in a high temperature environment compared to an alnico magnet. The magnet accommodating space forming part 90 forms a magnet accommodating space, and the samarium cobalt magnet 50 is accommodated in the magnet accommodating space, thereby reducing the possibility that the samarium cobalt magnet 50 will receive direct force from the outside of the protection element 10. By filling the gap between the samarium cobalt magnet 50 and the magnet accommodating space forming part 90 with the filler 54, the samarium cobalt magnet 50 does not collide with the magnet accommodating space forming part 90. This reduces the possibility that the samarium cobalt magnet 50 will be damaged compared to the case otherwise. As the possibility of damage to the samarium cobalt magnet 50 is reduced, a decrease in magnetic flux density due to damage to the samarium cobalt magnet 50 is less likely to occur. When the decrease in magnetic flux density becomes less likely to occur, the possibility that malfunctions associated with it will occur decreases. As a result, a protective element with higher reliability of operation under high temperature environments is provided.

Furthermore , the material of the filler 54 mentioned above is any one of epoxy resin, silicone resin, and urethane resin.

When the filler 54 is made of any one of epoxy resin, silicone resin, and urethane resin, the filler 54 has a buffering effect. Thereby, the possibility that the samarium cobalt magnet 50 will be damaged is further reduced compared to the case where this is not the case. As a result, a protection element is provided that is more reliable in operation under high temperature environments.

Furthermore , the above-described filler 54 brings the samarium cobalt magnet 50 into close contact with the region 170 of the magnet accommodation space forming portion 90 that faces the pair of electrodes 22 and 24 .

The filler 54 brings the samarium cobalt magnet 50 into close contact with the region 170 of the magnet accommodation space forming portion 90 that faces the pair of electrodes 22 and 24, compared to the case where the samarium cobalt magnet 50 is separated from the region 170. , the arc experiences a large Lorentz force. The filler 54 having a buffering effect brings the samarium cobalt magnet 50 into close contact with the region 170 of the magnet accommodation space forming portion 90 that faces the pair of electrodes 22 and 24, so that the samarium cobalt magnet 50 receives force from the region 170. However, the influence of that force is mitigated. This reduces the possibility that the samarium cobalt magnet 50 will be damaged compared to the case otherwise. Since the possibility of the samarium cobalt magnet 50 being damaged is reduced, there is a high possibility that the situation in which the arc is subjected to a large Lorentz force will be maintained for a long period of time. As a result, a protective element with higher reliability of operation under high temperature environments is provided.

According to the present invention, a protection element with higher operational reliability in a high temperature environment is provided.

FIG. 2 is a perspective view of a protection element according to an embodiment of the invention. 1 is a cross-sectional view of a protection element according to an embodiment of the present invention. FIG. 1 is a perspective view of a case according to an embodiment of the present invention. It is a figure of the situation where a samarium cobalt magnet is being accommodated in a magnet accommodation space in an embodiment of an invention different from the present invention . FIG. 6 is a cross-sectional view of the vicinity of the magnet housing space forming portion of the case in a case where the filler has a buffer layer in an embodiment of the invention different from the present invention .

Hereinafter, the present invention will be explained in detail based on the drawings. In the following description, the same parts are given the same reference numerals. Their names and functions are the same. Therefore, detailed descriptions thereof will not be repeated.

[Configuration description]
FIG. 1 is a perspective view of a protection element 10 according to this embodiment. In FIG. 1 the protection element 10 is shown in assembled condition. In this figure, a part of the protection element 10 has been removed. FIG. 2 is a cross-sectional view of the protection element 10 according to this embodiment. The configuration of the protection element 10 according to this embodiment will be explained based on FIGS. 1 and 2.

The protective element 10 according to the present embodiment includes an insulating base 20, a positive electrode 22, a negative electrode 24, a heating element 26, a bonding material 28, an insulating spacer 30, a compression coil spring 32, an insulating plate 34, and a guide lead. 36 and a magnetic force generating section 38.

In the case of this embodiment, the insulating base 20 is made of Bakelite. The insulating substrate 20 serves as a base. The insulating base 20 is provided with a guide lead holding recess 152 .

The positive electrode 22 and the negative electrode 24 correspond to a pair of electrodes in the protection element 10 according to this embodiment. The positive electrode 22 and the negative electrode 24 are fixed to the insulating base 20 such that one end of each is opposite to each other and protrudes from the insulating base 20 .

The heating element 26 is a rectangular member with a hole in the center. The heating element 26 is arranged astride between the positive electrode 22 and the negative electrode 24. The heating element 26 generates heat when current flows therethrough.

In this embodiment, the bonding material 28 is used to bond the heating element 26 to the positive electrode 22. In this embodiment, the bonding material 28 is also used to bond the heating element 26 to the negative electrode 24. The bonding strength of the bonding material 28 is less than a predetermined strength at a predetermined temperature. In the case of this embodiment, the "predetermined temperature" means the temperature reached by the heat generated by the heating element 26. In the case of this embodiment, the bonding material 28 is an alloy whose melting point is the above-mentioned "predetermined temperature".

The insulating spacer 30 is a member having a cylindrical portion and an annular portion extending from one end of the cylindrical portion. The insulating spacer 30 provides insulation between the insulating base 20 and the compression coil spring 32.

Compression coil spring 32 is arranged between positive electrode 22 and negative electrode 24 . Compression coil spring 32 applies a separation force to heating element 26 . In the case of this embodiment, the "separation force" is a force in a direction in which the heating element 26 joined to the positive electrode 22 and the negative electrode 24 separates from the positive electrode 22 and the negative electrode 24. The above-mentioned "predetermined strength" means strength to withstand separation force. That is, the bonding material 28 cannot withstand the separation force when its temperature reaches a predetermined temperature.

The insulating plate 34 is a disc-shaped member with a hole in the center. The insulating plate 34 is placed on the compression coil spring 32. The insulating plate 34 provides insulation between the compression coil spring 32 and the heating element 26.

The guide lead 36 is a cylindrical member. The end of the guide lead 36 is inserted into the guide lead holding recess 152 of the insulating base 20. The guide lead 36 passes through the heating element 26. The heating element 26 subjected to the separation force rises along the guide lead 36.

The magnetic force generating section 38 generates magnetic force between the positive electrode 22 and the negative electrode 24 in advance. In the case of this embodiment, the magnetic force generating section 38 includes a samarium cobalt magnet 50, a case 52, and a filler 54.

In the case of this embodiment, the samarium cobalt magnet 50 has a rectangular parallelepiped shape. Therefore, the samarium cobalt magnet 50 according to this embodiment has a pair of planes parallel to each other. One of those planes is the north pole of the samarium cobalt magnet 50 according to this embodiment. The other of those planes is the S pole of the samarium cobalt magnet 50 according to this embodiment.

The case 52 covers the positive electrode 22, the negative electrode 24, the heating element 26, the bonding material 28, and the compression coil spring 32, and holds the samarium cobalt magnet 50.

FIG. 3 is a perspective view of the case 52 according to this embodiment. The configuration of the case 52 according to this embodiment will be explained based on FIG. 3. The case 52 according to this embodiment is made of Bakelite. In the case of this embodiment, the case 52 includes a pair of magnet housing space forming sections 90 and an operating space forming section 92 . The pair of magnet accommodation space forming sections 90 and the operating space forming section 92 are integrated.

In the case of this embodiment, the pair of magnet housing space forming sections 90 face each other with the operating space forming section 92 in between. The magnet accommodating space forming section 90 forms a magnet accommodating space. The magnet accommodation space forming section 90 has an electrode facing region 170. The electrode facing region 170 faces the positive electrode 22 and the negative electrode 24 . One samarium cobalt magnet 50 is housed in each magnet housing space.

The operating space forming section 92 forms an operating space. A positive electrode 22, a negative electrode 24, a heating element 26, a bonding material 28, and a compression coil spring 32 are housed in the operating space. A guide lead holding hole 150 is formed in the ceiling portion of the operating space forming section 92 .

The above-described filler 54 is housed together with the samarium cobalt magnet 50 in the magnet housing spaces formed by the pairs of magnet housing space forming sections 90, respectively. The filler 54 is filled in the gap between the samarium cobalt magnet 50 and the magnet accommodation space forming part 90. As is clear from FIG. 2, the filler 54 according to this embodiment brings the samarium cobalt magnet 50 into close contact with the electrode facing region 170 of the magnet accommodation space forming portion 90.

[Description of manufacturing method]
The protection element 10 according to this embodiment is manufactured by the following procedure. First, a manufacturer manufactures components that constitute the protection element 10 according to this embodiment. Methods of manufacturing these parts are well known. Therefore, their detailed description will not be repeated.

When the above-described component is manufactured, the manufacturer inserts one end of the guide lead 36 into the guide lead holding recess 152 of the insulating base 20. The manufacturer then fixes the positive electrode 22 and negative electrode 24 to the insulating substrate 20. Once they are fixed, the manufacturer causes the guide lead 36 to pass through the insulating spacer 30, the compression coil spring 32, the insulating plate 34, and the heating element 26. When the guide lead 36 passes through them, the manufacturer joins the heating element 26 to the positive electrode 22 and the negative electrode 24 using the joining material 28 .

When the heating element 26 is joined to the positive electrode 22 and the negative electrode 24, the manufacturer manufactures the magnetic force generating section 38. First, the manufacturer places the samarium cobalt magnet 50 into the magnet housing space. At this time, the samarium cobalt magnet 50 is placed in close contact with the electrode facing region 170. Next, the manufacturer fills the magnet housing space of the case 52 with epoxy resin before polymerization. The epoxy resin that has entered the magnet housing space presses the samarium cobalt magnet 50 against the electrode facing area 170. Thereafter, when the polymerization of the epoxy resin is completed, the epoxy resin is cured. The hardened epoxy resin becomes the filler 54. Thereby, the filler 54 brings the samarium cobalt magnet 50 into close contact with the electrode facing region 170 , that is, the region of the magnet accommodation space forming portion 90 that faces the pair of the positive electrode 22 and the negative electrode 24 .

Next, the manufacturer covers the insulating base 20 with the case 52. At the same time, the manufacturer allows the guide lead 36 to pass through the guide lead holding hole 150. When the guide lead 36 passes through the guide lead holding hole 150, the manufacturer fills the recess around the guide lead holding hole 150 in the case 52 with epoxy resin before polymerization. When the epoxy resin is cured, the protective element 10 according to this embodiment is completed.

[Explanation of usage]
The protection element 10 according to this embodiment is used, for example, to protect a lithium ion secondary battery from overcurrent, overcharging, or overdischarging. Although the protection element 10 according to this embodiment is not strictly protection, it may be used to cut off power supply for reasons similar to protection. The protection element 10 according to this embodiment is used, for example, as one of the elements constituting a secondary battery protection circuit. In that case, the protection element 10 according to this embodiment is connected in series to the lithium ion secondary battery. The protection element 10 according to the present embodiment receives power supply based on the operation of any of the other elements constituting the above-described secondary battery protection circuit. A current resulting from the electric power flows from the positive electrode 22 to the negative electrode 24 of the protection element 10 according to this embodiment. The current passes through the heating element 26. Since the current passes through the heating element 26, the heating element 26 generates heat. When the heating element 26 generates heat, the temperature of the bonding material 28 increases. When the temperature of the bonding material 28 reaches the above-mentioned predetermined temperature, the bonding material 28 melts. When the bonding material 28 melts, the compression coil spring 32 separates the heating element 26 from the positive electrode 22 and the negative electrode 24. As a result, current no longer flows from the positive electrode 22 to the negative electrode 24. When current stops flowing from the positive electrode 22 to the negative electrode 24, power to the lithium ion secondary battery described above is cut off. As a result, the lithium ion secondary battery is protected.

When the compression coil spring 32 moves the heating element 26 away from the positive electrode 22 and negative electrode 24, arcing may occur. When an arc occurs, electrons are emitted from the negative electrode 24 to the positive electrode 22. Since the samarium cobalt magnet 50 of the magnetic force generating section 38 generates a magnetic force between the positive electrode 22 and the negative electrode 24 in advance, a Lorentz force acts on the emitted electrons. Since the Lorentz force acts on the electron, the trajectory of the arc bends. When the trajectory curves, the arc lengthens compared to when it does not curve. When the arc extends, the voltage at which the arc occurs (arc voltage) becomes higher than when the arc does not extend. Additionally, the arc is cooled by being extended. Further, the arc is cooled by contacting the case 52, that is, a structure made of an insulating material. The synergistic effect of the increase in arc voltage and the cooling of the arc makes it difficult for the arc to continue. Since the arc becomes difficult to sustain, the protection element 10 according to this embodiment can flow a large current at a larger voltage than the conventional protection element 10.

[Explanation of effects]
In the protection element 10 according to the present embodiment, the samarium cobalt magnet 50 included in the magnetic force generating section 38 has superior performance in a high temperature environment compared to an alnico magnet. When the samarium cobalt magnet 50 is damaged, the pieces of the samarium cobalt magnet 50 exert magnetic force on each other. When the pieces of the samarium cobalt magnet 50 give magnetic force to each other, part of the magnetic force that was directed outside the samarium cobalt magnet 50 before the breakage is directed from one of the pieces of the samarium cobalt magnet 50 to another. That will happen. As a result, the magnetic flux density outside the magnetic force generating section 38 decreases. On the other hand, the magnet accommodating space forming part 90 of the case 52 forms a magnet accommodating space, and the samarium cobalt magnet 50 is accommodated in the magnet accommodating space, so that the samarium cobalt magnet 50 can receive direct force from the outside of the protection element 10. Sexuality decreases. By filling the gap between the samarium cobalt magnet 50 and the magnet accommodating space forming part 90 with the filler 54, the samarium cobalt magnet 50 does not collide with the magnet accommodating space forming part 90. This reduces the possibility that the samarium cobalt magnet 50 will be damaged compared to the case otherwise. When the samarium cobalt magnet 50 becomes difficult to break, it becomes difficult for the magnetic flux density to decrease due to the damage of the samarium cobalt magnet 50. When it becomes difficult for the magnetic flux density to decrease, the possibility that the arc becomes difficult to extend or cooled decreases. When the possibility of the arc becoming difficult to extend or being cooled is reduced, the possibility of associated malfunctions occurring is reduced. As a result, the reliability of operation of the protection element 10 according to this embodiment in a high temperature environment becomes higher.

Furthermore, in the protection element 10 according to this embodiment, the material of the filler 54 is epoxy resin, so the possibility that the samarium cobalt magnet 50 will be damaged is further reduced due to the buffering effect of the filler 54. As a result, the reliability of the operation of the protection element 10 according to this embodiment in a high temperature environment becomes even higher.

Further, in the protection element 10 according to the present embodiment, the filler 54 brings the samarium cobalt magnet 50 into close contact with the electrode facing region 170 of the magnet accommodation space forming portion 90 . As a result, the arc is subjected to a larger Lorentz force than when the samarium cobalt magnet 50 is away from the electrode facing region 170. Since the filler 54 having a buffering effect brings the samarium cobalt magnet 50 into close contact with the electrode facing region 170, even if the samarium cobalt magnet 50 receives a force from the electrode facing region 170, the influence of the force is alleviated. This reduces the possibility that the samarium cobalt magnet 50 will be damaged compared to the case otherwise. Since the possibility of the samarium cobalt magnet 50 being damaged is reduced, it is more likely that the situation in which the arc is subjected to a large Lorentz force will be maintained for a long period of time. As a result, a protective element with higher reliability of operation under high temperature environments is provided.

<Explanation of modification example>
The protection element 10 described above is exemplified to embody the technical idea of the present invention. The protection element 10 described above can be modified in various ways within the scope of the technical idea of the present invention.

For example, the number and arrangement of magnets are not limited to those described above. The material of the insulating base 20 and the case 52 may be a phenol resin other than Bakelite. These materials may also be other insulating materials. Examples of other insulating materials include polybutylene terephthalate (PBT) and polyphenylene sulfide (PPS). These insulating materials may or may not contain fillers. An example of an insulating material containing a filler is polyphenylene sulfide containing a glass filler. The direction of the magnetic force generated by the magnetic force generating section 38 is not particularly limited as long as the arc generated between the positive electrode 22 and the negative electrode 24 can extend under the Lorentz force. The protection element according to the present invention may include a disc spring or other elastic body instead of the compression coil spring 32.

Further, the material of the filler 54 may be either silicone resin or urethane resin .

In a manufacturing procedure for a protection element according to an invention different from the present invention , the magnetic force generating section 38 may be manufactured by, for example, the following procedure. In that case, the manufacturer first puts a small amount of epoxy resin 190 before polymerization into the magnet housing space of the case 52. Next, the manufacturer places the samarium cobalt magnet 50 into the magnet housing space. At this time, the samarium cobalt magnet 50 is inserted so that a gap is formed between the samarium cobalt magnet 50 and the electrode facing region 170. FIG. 4 is a diagram showing a state in which the samarium cobalt magnet 50 is being accommodated in the magnet accommodation space. When the samarium cobalt magnet 50 is housed in the magnet housing space, the manufacturer adds epoxy resin 190 before polymerization to the magnet housing space. Thereafter, when the polymerization of the epoxy resin 190 is completed, the epoxy resin 190 is cured. The cured epoxy resin 190 becomes the filler 54. In this case, the epoxy resin 190 enters into the gap between the samarium cobalt magnet 50 and the electrode facing region 170 by soaking the samarium cobalt magnet 50 in the epoxy resin 190 already contained therein. Thereafter, by adding the epoxy resin 190 before polymerization, the epoxy resin 190 further enters the gap between the samarium cobalt magnet 50 and the electrode facing region 170. As a result, the filler 54 has a buffer layer 192 disposed between the samarium cobalt magnet 50 and the electrode facing region 170. FIG. 5 is a cross-sectional view of the vicinity of the magnet housing space forming portion 90 of the case 52 when the filler 54 has the buffer layer 192.

10...Protective element 20...Insulating base 22...Positive electrode 24...Negative electrode 26...Heating element 28...Joining material 30...Insulating spacer 32...Compression coil spring 34...Insulating plate 36...Guide lead 38...Magnetic force generating section 50...Samarium cobalt magnet 52... Case 54...filler 90...magnet accommodation space forming part 92...operating space forming part 110...inner wall forming part 112...magnet arrangement part 130...magnet base part 132...leg part 150...guide lead holding hole 152...guide lead holding recess 170... Electrode facing region 190... Epoxy resin 192... Buffer layer

Claims (1)

a pair of electrodes facing each other;
a heating element that is disposed astride between the pair of electrodes and generates heat when a current flows;
a bonding material for bonding the heating element to each of the pairs of electrodes;
an elastic body disposed between the pair of electrodes and applying a separating force to the heating element;
a magnetic force generating section that generates magnetic force in advance between the pair of electrodes,
The separation force is a force in a direction that causes the heating element to separate from the pair of electrodes,
the bonding strength of the bonding material is below a predetermined strength at a predetermined temperature;
The predetermined temperature is a temperature reached by heat generation of the heating element,
The predetermined strength is a protection element that is strong enough to withstand the separation force,
The magnetic force generating section is
samarium cobalt magnet,
a magnet accommodating space forming part that forms a magnet accommodating space in which the samarium cobalt magnet is accommodated;
a filler that is housed in the magnet housing space together with the samarium cobalt magnet and filled in a gap between the samarium cobalt magnet and the magnet housing space forming part ;
The material of the filler is any one of epoxy resin, silicone resin, and urethane resin,
A protection element characterized in that the filler brings the samarium cobalt magnet into close contact with a region of the magnet accommodation space forming portion that faces the pair of electrodes .

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