JP2022067385A5 - - Google Patents

Description

The present invention relates to a fuse in which a space inside the case is filled with a filler as an arc extinguisher so as to tightly adhere to and seal the conductor housed in the case.

1 to 3 of JP-A No. 2015-35338 (Patent Document 1) show a current fuse, etc. in which the space inside the case 12 is filled with a filler material 14 so as to seal the conductor 54 housed in the case 12. A protection element is disclosed. In this protective element, the filler contains particulate alumina and silicone resin, and in a specific example, silicone rubber is used as the silicone resin. The publication states that when the filler 14 is in close contact with the conductor 54 and the filler 14 seals the conductor 54, the heat generated in the conductor 54 due to energization can be easily transferred to the conductor 54 compared to when there is a space around the conductor 54. It is described that the conductor 54 is more likely to flow out of the conductor 54, thereby suppressing a rise in temperature of the conductor 54 due to accumulation of heat over a long period of time. Furthermore, the publication states that in order to prepare for the conductor 54 melting down due to a small Joule heat integral value, it is no longer necessary to increase the cross-sectional area of the surface perpendicular to the direction in which the current flows in the cross section of the conductor 54. There is. Furthermore, when the filler 14 comes into close contact with the conductor 54 and the filler 14 seals the conductor 54, the heat generated when the conductor 54 melts expands the gas around the conductor 54, thereby preventing damage to the protective element. It is stated that this can be avoided and the reliability, speed, and safety of operation can be improved. Furthermore, silicone resin has good heat resistance among synthetic resins, so by including silicone resin in the filler 14, deterioration of the filler 14 due to heat can be suppressed compared to when other synthetic resins with poor heat resistance are included. It is stated that.

Japanese Patent Application Publication No. 2015-35338

It is presumed that the silicone resin described in Cited Document 1 was dissolved into a liquid state using an organic solvent and then hardened after filling the case. However, when the filler filled in the entire case is cured, the volume of the filler after hardening will vary, so filling the case to its full capacity requires special equipment and time. There is a problem that it takes Furthermore, a filler made of hardened silicone resin has a problem in that the insulation resistance after interruption is not very high.

An object of the present invention is to provide a fuse that can easily fill the case with the filler even when silicone resin is used as the filler material, and that can increase the insulation resistance after being cut off. There is a particular thing.

The present invention includes a conductor that includes a plurality of fusing parts and a plurality of non-fusing parts, and in which at least one fusing part melts when a current having a Joule heat integral value equal to or greater than a predetermined value flows, and a case that accommodates the conductor. , the fuse includes an arc-extinguishing filler filled in the space inside the case so as to seal the conductor. In the present invention, the space within the case includes one or more first space portions including at least one of the plurality of fusing portions of the conductor, and the remaining space portion other than the at least one fusing portion of the conductor. One or more second space portions include the fusing portion. The first space is filled with a first type of filler containing silica sand particles. The second space is filled with a second type of filler, which is made of a mixture of silica sand particles and silicone resin particles, and is made by melting and hardening the silicone resin particles. Note that the one or more first space portions and the one or more second space portions are formed as a result of filling the case with the first and second types of fillers.

One first space portion and one second space portion may be arranged in the longitudinal direction of the conductor portion, and the second space portions are arranged on both sides of the one first space portion, and the second space portion is located on both sides of the conductor portion. The first space portions may be arranged in the longitudinal direction of the conductor portion, and the first space portions may be arranged on both sides of one second space portion in the longitudinal direction of the conductor portion, and the first space portions may be arranged alternately in the longitudinal direction of the conductor portion. The number of first and second spatial parts is arbitrary.

In the second space, connecting portions made of melted and hardened silicone resin are formed between each particle of silica sand, between the silica sand and the case, and between the silica sand and the fused portion of the conductor. As a result, the silica sand and silicone resin melted by the heat of the arc when the conductor melted, combined with the melted conductor to form an insulator and extinguish the arc. Damage to the protective element due to expansion of gas around the body can be avoided, and reliability, speed and safety of operation can be improved. Furthermore, in the present invention, since the first space is filled with the first type of filler that does not contain silicone resin particles but contains silica sand particles, the silicone resin particles melt and harden. Even if the volume of the second space created by this process is not constant, the inside of the case can be easily filled with the filling material . In particular, the first space portion filled with the first type of filler containing silica sand particles but not silicone resin particles exists as an almost completely insulated portion after disconnection, so that the fuse after disconnection Insulation resistance can be increased reliably.

Note that the silicone is preferably a condensed thermosetting silicone resin. Condensation type thermosetting silicone melts when heated to form a connecting portion without having to be liquefied using an organic solvent, making it easier to manufacture fuses.

The structure of the conductor is arbitrary. A typical conductor consists of a single wire conductor in which multiple narrow sections with a high resistance value and multiple wide sections with a low resistance value are arranged alternately, and one narrow section constitutes one fusing section. , one wide area constitutes one unfused area. As a conductor, N parallel conductors (N is an integer of 2 or more) are connected in parallel to one single wire conductor in which multiple narrow portions with a high resistance value and multiple wide portions with a low resistance value are arranged alternately. N narrow parts adjacent in the parallel direction of N single wire conductors constitute one fusing part, and N wide parts adjacent in the parallel direction of N single wire conductors constitute one fusing part. It is also possible to use a material having two non-fusion parts.

As the condensation type thermosetting silicone resin, those represented by the following chemical formula can be used.

FIG. 2 is a perspective view of the appearance of the fuse according to the present embodiment. FIG. 2 is a longitudinal cross-sectional view of the fuse of FIG. 1; (A) to (C) are photographs taken with a microscope at 100x magnification of natural silica sand, condensed thermosetting silicone resin particles, and a mixture of natural silica sand particles and condensed thermosetting silicone resin particles, respectively. be. (A) and (B) are the arc duration and recovery voltage of the fuse of this embodiment for the confirmation test using the first type of filler and the second type of filler, and (C) and (D) are the arc duration characteristics and recovery voltage characteristics of a comparative test fuse filled only with a second type of filler consisting of a mixture of silica sand and condensed thermosetting silicone.

An example of an embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view of the external appearance of the fuse 1 of this embodiment, and FIG. 2 is a longitudinal cross-sectional view of the fuse 1.

The fuse 1 of this embodiment includes an insulating cylindrical body 5 filled with a first type of filler 3A called arc-extinguishing sand and a second type of filler 3B, and the cylindrical body 5. A pair of cap-shaped electrodes 9 and 11 are fitted to both ends and electrically connected to a fuse element 7 as a conductor. L-shaped terminals 13 and 15 are fixed to the cap-shaped electrodes 9 and 11.

The cylindrical body 5 is integrally molded from ceramic. The fuse element 7 is a conductor that is integrally formed by pressing a long and narrow fuse metal plate made of silver or copper. The fuse element 7 of this embodiment is made of two single wire conductors, each of which has six wide portions 71A to 71E with a small resistance value and five narrow portions 73A to 73E with a large resistance value arranged alternately. 70A and 70B are constituted by parallel conductors connected in parallel. Two narrow parts (for example, 73B, 73B) adjacent in the parallel direction of the two single-wire conductors 70A and 70B constitute one fusing part, and two narrow parts (for example, 73B, 73B) adjacent in the parallel direction of the two single-wire conductors 70A and 70B Two wide parts (for example, 71B, 71B) constitute one unfused part. Therefore, in this fuse element 7, five blown parts and six non-fused parts are arranged alternately in the longitudinal direction of the fuse element 7.

In this embodiment, the case 12 is constituted by the cylinder 5 and the cap-shaped electrodes 9 and 11. The space 4 in the case 12 of the fuse 1 of this embodiment includes a first space portion 4A containing one fusing part (71A, 71A) and four fusing parts (73B, 73B to 73E, 73E). It is divided into a second space portion 4B contained therein. The first space portion 4A is filled with a first type of filler 3A containing only silica sand particles. Further, the second space portion 4B is filled with a second type of filling made of a mixture of silica sand particles and condensed thermosetting silicone resin particles, which is formed by melting and hardening the condensing thermosetting silicone resin particles. Material 3B is filled. In the second space portion 4B, between each silica sand, between the silica sand and the case 12, and between the silica sand and the fusing part of the fuse element 7 as a conductor, there is a condensation type thermosetting material that has been melted and hardened. A connecting portion made of silicone resin is formed. With this structure, even if the volume of the second space portion 4B formed by melting and hardening of the condensed thermosetting silicone resin particles is not constant, the silica sand does not contain any condensed thermosetting silicone resin particles. By adjusting the volume of the first space portion 4A, whose volume is determined by the amount of the first type of filler 3A containing only particles, the inside of the case 13 is filled with the filler .

Specifically, the second type of filler 3A is composed of a mixture of natural silica sand particles and condensed thermosetting silicone resin particles. The heat of the arc generated after the fusing parts (73A, 73A to 73E, 73E) of the fuse element 7 are melted melts the silica sand particles, which cover and adhere to the surface of the fuse element 7, causing the arc to be extinguished by the cooling effect. Ru. In this embodiment, the first space portion filled with the first type of filler containing only silica sand particles without containing particles of condensed thermosetting silicone resin has one fusing portion (7A, 7A), and since this one fusing portion is reliably fused, the first space portion exists as an almost completely insulated portion (2000 MΩ or more) after the cutoff.

The condensed thermosetting silicone contained in the second type of filler 3B used in this embodiment is represented by the chemical formula below.

The molecules of this condensation type thermosetting silicone resin are connected to each other by a reaction caused by heat, and in a thermoset state, there is almost no elasticity or compressibility. Therefore, this silicone has different properties after curing from silicone rubber, which exhibits high elasticity and compressibility after curing.

In this embodiment, the average particle size of the natural silica sand particles is 245 μm, the average particle size of the condensed thermosetting silicone resin particles is 15 μm, and the proportion of the condensed thermosetting silicone in the mixture is 0 to 12 μm. A mixture with varying percentages was prepared as a second type of filler 3A.

Figures 3 (A) to (C) show natural silica sand with an average particle size of 245 μm, particles of condensed thermosetting silicone resin with an average particle size of 15 μm, and particles of these natural silica sand particles and condensed thermosetting silicone resin. This is a photograph taken with a microscope at 100 times magnification of the mixture (the proportion of condensed thermosetting silicone resin is 7%). As shown in FIG. 3(C), it can be seen that in this mixture, many small particles of composite thermosetting silicone resin are wrapped around the particles of natural silica sand.

Moreover, as the first type of filler 3A, natural silica sand with an average particle diameter of 245 μm was prepared. Note that in the present specification, the average particle size means the particle size at 50% of the integrated value in the particle size distribution determined by laser diffraction/scattering method.

[Test fuse]
In order to confirm the interrupting performance, a pure silver plate is processed as the fuse element 7, and a single wire conductor is formed so that the width of the narrow part is, for example, 0.2 mm to 0.3 mm, and the width of the wide part is, for example, 6 mm to 7 mm. I prepared two wires lined up in parallel.

A fuse in which only the second type of filler was placed in the case 12 was prepared as a fuse for comparative testing. In addition, for a confirmation test, the first space was filled with the first type of filler and the second space was filled with the second type of filler, as in the above embodiment. .

In each of the fuses for the comparison test and the fuse for the confirmation test, thermal condensation type thermal effect silicone is formed between each natural silica sand, between the natural silica sand and the case, and between the natural silica sand and the conductor. There was no large variation in the amount of connecting parts made of resin. In addition, we conducted a test for the breaking performance of both fuses, and it was confirmed that the breaking performance of both fuses improved.

However, when the insulation resistance was measured after the fuse was cut off, it was found that the insulation resistance of the comparative test fuse was as large as several MΩ. This is considered to be due to the presence of carbon components in the condensed thermosetting silicone resin. In contrast, all of the test fuses had insulation resistances of 2000 MΩ or more after being cut off. This means that in areas where the first type of filler does not contain condensed thermosetting silicone resin but only contains silica sand, no carbon component is present in the layer of the first type of filler after cutting off. This is because it showed perfect insulation properties.

[Interrupting characteristic test]
The breaking performance tests for the fuses for the comparison test and the fuse for the confirmation test were conducted in accordance with the general rules of JIS8352. As a result, it was confirmed that performance such as arc duration and recovery voltage was improved. FIG. 4 shows the results of testing the interrupting characteristics of the fuses for comparison testing and the fuses for confirmation testing. FIGS. 4A and 4B show the arc duration when the fuse of this embodiment for a confirmation test using the first type of filler 3A and the second type of filler 3B is charged to 710V. and the recovery voltage, and Figures 4 (C) and (D) show the results when a comparative test fuse filled with only the second type of filler, which is a mixture of silica sand and condensed thermosetting silicone, was charged to 710 V. arc duration characteristics and recovery voltage characteristics. As can be seen by comparing FIG. 4(B) and FIG. 4(D), the arc duration of the fuse for the confirmation test of this embodiment is slightly longer than that of the fuse for the comparative test. Furthermore, as can be seen by comparing FIGS. 4A and 4C, it can be seen that the recovery voltage of the fuse manufactured in this embodiment is as stable as that of the fuse of the comparative example. However, the test results show that the fuses used for the confirmation test and the fuses used for the comparison test do not differ significantly in their breaking characteristics. As mentioned above, when the insulation resistance after disconnection was measured, the insulation resistance of the fuses for comparison tests was approximately several MΩ at most, but for the fuses for the confirmation test of this embodiment, the insulation resistance was The insulation resistance after interruption was 2000 MΩ or more. Therefore, in this respect, it was confirmed that the fuse of this embodiment is practically excellent.

[Mixing ratio test]
A test was conducted to confirm the mixing ratio of condensed thermosetting silicone in a mixture of natural silica sand particles and condensed thermosetting silicone resin particles. In this test, the mixing ratio of condensation type thermosetting silicone was varied from 0% to 12% in a comparative test fuse, and the arc current and arc duration were measured. It was found that when the mixing ratio was between 7% and 12%, the current squared time product arc I2t became smaller and the arc duration became shorter. Therefore, it can be seen from this result that the mixing ratio is preferably 7% to 12%. Note that this preferable range does not change even if the rated capacity of the fuse changes, and even if the rated capacity of the fuse changes, and as in the embodiment shown in FIG. The second type of filler 3B in the fuse of this embodiment is also substantially unchanged.

[Number of cut-off parts]
In the above embodiment, the first space portion 4A includes one non-blocking portion (71A, 71A) and one blocking portion (73A, 73A); It is preferable that the number of blocking parts included in the second space portion 4B is smaller than the number of blocking parts included in the second space portion 4B. This is because the second type of filler 3B has better blocking performance than the first type of filler 3A.

In the embodiment described above, each of the first space portion 4A and the second space portion 4B is provided, but a plurality of each of these space portions may exist. If there are a plurality of them, the first space portions 4A and the second space portions 4B may be arranged alternately along the fuse element 7.

[others]
Although natural silica sand is used in the above embodiment, it is of course possible to use artificial silica sand.

Furthermore, in the above embodiments, the condensed thermosetting silicone having the chemical formula described above is used, but it is of course applicable to the case where other condensed thermosetting silicones are used.

Further, the shape of the fuse element is not limited to the shape of this embodiment.

According to the present invention, even when silicone is used as the material for the arc-extinguishing filler, the insulation resistance after interruption can be increased.

1 fuse 3A first type of filler
3B Second type of filler 4A First space portion 4B Second space portion 5 Cylindrical body 7 Fuse element 9, 11 Cap-shaped electrode 12 Case

Claims (8)

A conductor comprising a plurality of fusing parts and a plurality of non-fusing parts, and at least one of the fusing parts melts when a current having a Joule heat integral value equal to or higher than a predetermined value flows;
a case housing the conductor;
A fuse comprising an arc-extinguishing filler filled in a space in the case so as to seal the conductor,
The space includes one or more first space parts including at least one fusing part included in the plurality of fusing parts of the conductor, and the remaining fusing parts other than the at least one fusing part of the conductor. Consisting of one or more second spatial parts containing,
The first space portion is filled with a first type of filler containing silica sand particles,
The second space is filled with a second type of filler, which is made of a mixture of silica sand particles and silicone resin particles, and is made by melting and hardening the silicone resin particles. Fuse to do. The fuse according to claim 1, wherein one of the first space portions and one of the second space portions are lined up in the longitudinal direction of the conductor. The fuse according to claim 1, wherein the second space portions are arranged on both sides of one of the first space portions in the longitudinal direction of the conductor. The fuse according to claim 1, wherein the first space portions are arranged on both sides of one of the second space portions in the longitudinal direction of the conductor. The fuse according to any one of claims 1 to 4, wherein the silicone resin is a condensation type thermosetting silicone resin. The conductor is composed of a single wire conductor in which a plurality of narrow portions having a high resistance value and a plurality of wide portions having a low resistance value are arranged alternately, and one narrow portion constitutes one fusing portion. 5. The fuse according to claim 1 , wherein one of the wide portions constitutes one of the unfused portions. The conductor is a parallel conductor in which N single wire conductors (N is an integer of 2 or more) are connected in parallel, in which a plurality of narrow portions with a high resistance value and a plurality of wide portions with a low resistance value are arranged alternately. Composed of conductors,
The N narrow portions adjacent in the parallel direction of the N single wire conductors constitute one fusing portion, and the N wide portions adjacent in the parallel direction of the N single wire conductors constitute one fusing portion. 5. The fuse according to claim 1, wherein said non-melting portion comprises two non-melting portions. The condensed thermosetting silicone resin is represented by the chemical formula below.

The fuse according to claim 4 or 7.