Patent Application
20170084415
The present invention relates to a small chip fuse, in particular a chip fuse having a fuse wire placed through its body and used in units supplying power equivalent to rated current and voltage for general household, as well as a method for producing the chip fuse.
In a protection circuit on the primary side of a transformer used with a power unit, a fuse (primary fuse), generally a tubular fuse installed in a fuse holder, is used. To cope with the demand of the market for downsizing and weight-saving of a power unit, however, fuses have come to be directly surface-mounted on a wiring board. For this purpose, rather than a tubular fuse having a cylindrical glass casing, a rectangular chip fuse is often used, in which a linear or strip-shaped fuse element is mounted between the electrodes in a box-shaped ceramic casing. An example of prior art of such a box-shaped casing is disclosed in JP-2012-174443-A, known from which is a chip fuse composed of a fuse wire support made of ceramics and having a through hole along its center, a fuse wire mounted linearly across the through hole between the two opposed ends of the fuse wire support, a cylindrical ceramic casing in which the fuse wire support with the fuse wire as a fuse assembly is inserted, and metal caps located at both ends of the cylindrical body of the casing in electrical conduction with the fuse wire projecting from both ends of the fuse wire support.
Patent Publication 1: JP-2012-174443-A
The conventional chip fuse as discussed above is structured by inserting, into the cylindrical ceramic casing, the fuse assembly consisting of the fuse wire and the fuse wire support, so that the impact from current interruption by the fuse cannot be released to anywhere, causing possible damaging or deformation of the casing. Further, an evaporation product of the fuse element (vapor) generated upon fusion cannot be released to anywhere, and the vapor remains in the casing after fusion, which disadvantageously disturbs security of the insulating resistance between the fused fuse terminals or between the fused fuse wire ends.
The present invention has been made to solve the conventional drawbacks. It is therefore an object of the present invention to provide a chip fuse which is improved to facilitate balanced release of the impact and the vapor generated upon fusion, as well as a method for producing the chip fuse.
According to the present invention, there is provided, as a solution to the above problems, a chip fuse comprising a fuse body and a pair of metal caps, said fuse body further comprising:
a pair of vertically facing upper and lower ceramic substrates,
a fuse wire support having a vertical through hole in its center and held between said upper and lower ceramic substrates, and
a fuse wire mounted between two ends of said fuse wire support across the through hole,
wherein said metal caps are fitted on two ends of said fuse body in electrical conduction with said fuse wire extending out of two ends of said fuse wire support,
wherein said upper ceramic substrate and said fuse wire support, and said lower ceramic substrate and said fuse wire support, are respectively adhered together on their mutually facing surfaces to hermetically close said through hole, partially leaving a non-adhered region on said surfaces adhered.
According to an embodiment of the invention, the non-adhered region may be formed on both sides of the through hole with respect to its longitudinal.
The fuse wire support may be composed of an upper fuse wire support half and a lower fuse wire support half vertically arranged with respect to each other, the through hole may vertically penetrate the upper fuse wire support half and the lower fuse wire support half, and the fuse wire may be mounted across the through hole in the longitudinal direction of the fuse wire support. The non-adhered region may be formed between the upper ceramic substrate and the upper fuse wire support half, between the upper fuse wire support half and the lower fuse wire support half, and between the lower fuse wire support half and the lower ceramic substrate.
According to another embodiment, the fuse wire support may be a single body, and the fuse wire may be mounted across the through hole in the fuse wire support at a slant between two opposed ends of the fuse wire support from an upper surface at one of the ends to a lower surface at the other of the ends of the fuse wire support.
According to the present invention, there is also provided a method for producing the above-mentioned chip fuse, comprising:
mounting a fuse wire between two ends of a fuse wire support having a vertical through hole in its center, across said through hole,
holding said fuse wire support with the fuse wire between a pair of vertically facing ceramic substrates,
adhering together said pair of the ceramic substrates and said fuse wire support on their mutually facing surfaces, partially leaving a non-adhered region on said surfaces adhered, to thereby form a fuse body, and
fitting a metal cap on each end of said fuse body in electrical conduction with said fuse wire.
According to an embodiment of the invention, the non-adhered region may be formed on both sides of the through hole with respect to its longitudinal.
The fuse wire support may be composed of an upper fuse wire support half and a lower fuse wire support half vertically arranged with respect to each other, the through hole may vertically penetrate the upper fuse wire support half and the lower fuse wire support half, and the fuse wire may be mounted across the through hole in the longitudinal direction of the fuse wire support between the upper fuse wire support half and the lower fuse wire support half. The non-adhered region may be formed between the upper ceramic substrate and the upper fuse wire support half, between the upper fuse wire support half and the lower fuse wire support half, and between the lower fuse wire support half and the lower ceramic substrate.
According to another embodiment, the fuse wire support may be a single body, and the fuse wire may be mounted across the through hole in the fuse wire support at a slant between two opposed ends of the fuse wire support from an upper surface at one of the ends to a lower surface at the other of the ends of the fuse wire support.
According to the present invention, there is further provided a method for producing the above-mentioned chip fuse, comprising:
adhering together an upper ceramic substrate and an upper fuse wire support half having a vertical through hole in its center, and a lower ceramic substrate and a lower fuse wire support half having a vertical through hole in its center, respectively, on their mutually facing surfaces, partially leaving a non-adhered region in said surfaces respectively adhered,
mounting a fuse wire between two ends of said lower fuse wire support half across said through hole,
arranging vertically with respect to each other and adhering together said lower fuse wire support half with the fuse wire and said upper fuse wire support half on their mutually facing surfaces, partially leaving a non-adhered region on said surfaces adhered, to thereby form a fuse body, and
fitting a metal cap on each end of said fuse body in electrical conduction with said fuse wire.
According to an embodiment, the non-adhered region may be formed on both sides of the through hole with respect to its longitudinal.
The chip fuse according to the present invention is mainly composed of a fuse body including a pair of vertically facing upper and lower ceramic substrates, a fuse wire support, and a fuse wire mounted on the fuse wire support, and the upper ceramic substrate and the fuse wire support, and the lower ceramic substrate and the fuse wire support, are respectively adhered together on their mutually facing surfaces to hermetically close the through hole, partially leaving a non-adhered region on the adhered surfaces, so that the impact and the vapor generated upon fusion of the fuse is released from inside the chip fuse through the non-adhered regions to outside. Thus, deformation and damage of the chip fuse may be avoided. Since the vapor is not retained inside the chip fuse, the insulating resistance between the fused fuse terminals or between the fused fuse wire ends may be secured, which improves the performance of the chip fuse.
The present invention realizes a fuse which is not damaged upon fusion and in which the insulating resistance between the fused fuse terminals or between the fused fuse wire ends is secured, and protects elements of electronic circuits used in a distribution board or the like which undergoes relatively high voltage and current for general household or the like, to secure the safety against fire disasters.
The upper ceramic substrate 1 and the lower ceramic substrate 5 are in the form of a thin flat plate, and cut out of a ceramic sheet having a larger area than that of the ceramic substrate 1, 5.
The upper fuse wire support half 3 and the lower fuse wire support half 7 are in the form of a thin flat plate, and cut out of a sheet, e.g. an alumina ceramics sheet, having a larger area than that of the fuse wire support half 3, 7.
The fuse wire 9 is made of a metal material in the form of wire or a thin rod, and produced by, for example, silver-plating annealed copper wire or iron-nickel alloy wire. The fuse wire 9 has been set at a particular fusing current value so as to fuse at the particular current value when connected in a circuit of electric equipment or facilities.
The adhesive 2, 6 used in adhering the ceramic substrate 1, 5 and he fuse wire support half 3, 7, respectively, may be, for example, an epoxy adhesive. The adhesive 2, 6 is formed into, for example, as shown in
In this way, the non-adhered region 26, 28, 27 is formed between the members 1 and 3, between the members 7 and 5, and members 3 and 7, respectively, on the adhered surfaces on both sides of the through hole 26 with respect to its longitudinal, while each pair of the members adhered together are closely adhered as a whole, so that the through holes 16 of the fuse wire support halves 3 and 7 define an internal space and is kept hermetically closed in the normal state, i.e., before fusion.
According to the present embodiment, which has the structure as discussed above, the impact (pressure) or vapor generated upon fusion of the fuse wire 9 by the flow of overcurrent through the chip fuse 25 is not only buffered by the volume of the through holes 16, but also released through the non-adhered regions 26, 27, 28 in the side faces, so that safe current interruption is achieved. In other words, according to the present embodiment, damage or deformation of the chip fuse body, which is observed in conventional chip fuses, does not occur. Further, the releasing of the vapor generated upon fusion to outside remarkably improves the insulating resistance between the fused fuse terminals or between the fused fuse wire ends. The release of vapor through the non-adhered regions 26, 27, 28 may be adjusted by varying the shape and size of the adhesives 2, 6, 20.
The present embodiment is fabricated by vertically arranging a pair of fuse support halves each prepared by adhering together a ceramic substrate and a fuse wire support, holding a fuse wire between the pair of the fuse support halves and uniting the same to obtain a fuse body, and then covering the ends of the fuse body with metal caps, and accordingly the current interruption characteristics of the fuse as well as the insulating resistance between the fused fuse terminals or between the fused fuse wire ends after fusion may be improved.
In the production method discussed above, the upper ceramic substrate 1 and the upper fuse wire support half 3 are adhered to obtain the upper fuse support half 4, and the lower ceramic substrate 5 and the lower fuse wire support half 7 are adhered to obtain the lower fuse support half 8, and then the fuse wire 9 is held between the fuse support halves 4 and 8. Alternatively, the fuse wire 9 may be held between the upper fuse wire support half 3 and the lower fuse wire support half 7, and then the upper fuse wire support half 3 and the lower fuse wire support half 7 may be adhered to the upper ceramic substrate 1 and the lower ceramic substrate, respectively.
This embodiment is the same as the first embodiment in that the upper ceramic substrate 31 and the lower ceramic substrate 32 are in the form of a thin flat plate, and the ceramic substrate 31, 32 is cut out, after various processing, of a ceramic sheet having a larger area than that. Production of the fuse wire support 35 is similar to that for the first embodiment, and through hole 37 is formed. In this embodiment, the fuse wire support grooves are formed in the upper and lower surfaces of the fuse wire support 35, wherein those formed in the upper surface of the fuse wire support 35 are fuse wire support grooves 38, whereas those formed in the lower surface are fuse wire support grooves 39. The structure, material, and characteristics of the fuse wire 36, and the materials of the adhesives 33, 40 are the same as those in the first embodiment. Also similarly to the first embodiment, the adhesives 33, 40 are formed in the predetermined shape, and accordingly non-adhered regions 44, 45 are partially left on the adhered surfaces of the upper ceramic substrate 31, the fuse wire support 35, and the lower ceramic substrate 32. Further similarly to the first embodiment, non-adhered regions 44, 45 are formed on the respective adhered surfaces of the members 31 and 35, and of the members 35 and 32, on both sides of the through hole 37 with respect to its longitudinal, and each pair of the members adhered together are closely adhered as a whole, so that the through hole 37 defines an internal space and is kept hermetically closed in the normal state, i.e., before fusion.
According to this embodiment, which has the structure as discussed above, the impact (pressure) or vapor generated upon fusion of the fuse wire 9 by the flow of overcurrent through the chip fuse 43 is not only buffered by the volume of the through hole 37, but also released through the non-adhered regions 44, 45 in the side faces, so that safe current interruption is achieved. In other words, according to the present embodiment, damage or deformation of the chip fuse, which is observed in conventional chip fuses, does not occur. Further, the releasing of the vapor generated upon fusion to outside remarkably improves the insulating resistance between the fused fuse terminals or between the fused fuse wire ends. The release of vapor through the non-adhered regions 44, 45 may be adjusted by varying the shape and size of the adhesives 33, 40.
In the first and second embodiments discussed above, during the fabrication of the fuse body, the upper ceramic substrate and the fuse wire support, and the lower ceramic substrate and the fuse wire support, are respectively adhered together on their mutually facing surfaces to hermetically close the through hole(s), while the non-adhered regions are left partially on the adhered surfaces, so that the internal through hole is kept hermetically closed in the normal state. In another embodiment, during the fabrication of the fuse body, discharge holes for releasing the impact and vapor generated upon fusion may be formed between the upper ceramic substrate and the fuse wire support and between the lower ceramic substrate and the fuse wire support.
Chip fuses of a four-layer structure according to the first embodiment of the present invention were fabricated. Upper and lower ceramic substrates and upper and lower fuse wire support halves were prepared from ceramic sheets. Using fuse wires prepared by silver-plating annealed copper wires, an epoxy adhesive, metal caps prepared by tin-copper-plating a copper-zinc alloy, and a solver cream, 0.011Ω chip fuses of Nos. 1 to 10 were obtained. Current interruption tests were conducted on the obtained chip fuses by applying alternating current of 100 V (phase angle 60°) at 100 A to fuse. The actually measured resistance and breaking time are shown in Table 1. Next, 500 V was applied to the fused chip fuses for 1 minute, and the residual resistance between the fuse terminals was measured with Digital Multi Meter (KIKUSUI ELECTRONICS CORP.). The results are shown in Table 1. In Table 1, “O.L.” (over load) in the column of the residual resistance means that the residual resistance was beyond the measurable range of the Multi Meter (1200 MΩ).
The Electrical Appliance and Material Safety Law in Japan stipulates that the residual resistance after the short circuit breaking performance test should be not lower than 200 kΩ. Table 1 shows that the residual resistances of all of the chip fuses of Nos. 1 to 10 satisfied the standard of the Electrical Appliance and Material Safety Law in Japan. Further, in all of the chip fuses, the impact (pressure) or vapor generated upon breaking operation was released through the non-adhered regions in the side faces, which generated three gap layers of a slight width in the side faces of the chip fuses, but the fuse bodies were not damaged.
Chip fuses were produced according to the prior art disclosed in JP-2012-174443-A. Similarly to the Example discussed above, a fuse wire support provided with a central through hole and fuse wire support grooves was prepared, the same epoxy adhesive as in the Example was applied to the fuse wire support grooves of the support, and the same fuse wire as in the Example was mounted linearly between the opposing ends of the fuse wire support across the through hole, to thereby obtain a fuse assembly. This fuse assembly was inserted into an alumina ceramic casing in the form of a rectangular cylinder, and metal caps were fixed on both ends with a solder cream in the same way as in the Example, so that 0.011Ω chip fuses of Nos. 1 to 5 were obtained. The current interruption tests were conducted on the obtained chip fuses and the residual resistances after fusion were measured in the same way as in the Example. The results are shown in Table 2.
Table 2 shows that the residual resistances of all the chip fuses of Nos. 1 to 5 in the Comparative Example were lower than those of the chip fuses in the Example. The standard of the Electrical Appliance and Material Safety Law in Japan was satisfied only by the chip fuse of No. 1, and the residual resistances of the chip fuses of Nos. 2 to 5 were beyond the standard. In all the chip fuses, the surface was observed to have been burned by the impact (pressure) or vapor generated upon breaking operation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-102171 | May 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/062793 | 4/28/2015 | WO | 00 |
