JP5740768B2 - Manufacturing method of cylindrical current fuse - Google Patents

Description

  The present invention relates to a cylindrical current fuse suitable for surface mounting on a substrate of an electronic device or the like and a method for manufacturing the same.

  Various types of small current fuses that can be surface-mounted on a printed circuit board have been proposed. For example, Patent Literature 1 discloses a cylindrical current fuse in which a fusible wire is stretched around a case body made of a cylindrical ceramic with a through-hole provided therein, and metal caps are fitted to both ends thereof. Has been.

  Patent Document 2 discloses a fusible wire stretched in a hollow space inside a rectangular parallelepiped case formed by fitting a case body made of ceramic and a lid. This cylindrical current fuse has a problem that the cost is increased due to the complicated case body and lid structure.

  On the other hand, the cylindrical current fuse described in Patent Document 1 has a structure in which a fusible wire is slanted in a through-hole inside the ceramic cylinder, so that the structure of the ceramic cylinder itself is relatively simple. However, the current fuse having such a structure has the following problems. In other words, it is preferable that the edge of the ceramic cylinder through-hole is connected to the end face of the ceramic cylinder via an appropriate roundness (curvature radius R), but it is possible to manufacture the moderate roundness (curvature radius R) uniformly. It ’s difficult.

  In an actual ceramic product, the radius of curvature R is different, and the edge of the through hole having almost no radius of curvature R may be nearly vertical (having sharp edges). In this case, when the fusible wire is stretched while being tensioned, the wire is rubbed at the inner peripheral edge portion (corner portion) of the through hole of the ceramic cylindrical body, so that there is a problem that the wire is damaged. When the wire is scratched and the thickness changes, the resistance changes, current concentrates at that portion, and the fusing characteristics are not stable. In the worst case, the wire may be cut by mechanical stress.

  Also, if the wire is stretched loosely so as not to damage the wire, the cap will be fitted and the wire will loosen when the solder melts, and the wire length will not be stable, and the wire will adhere to the inner wall of the ceramic cylinder There is a problem that the fusing characteristics are not stable.

JP-A-6-342623 JP-A-8-162000

  The present invention has been made based on the above-mentioned circumstances, and without damaging the wire at the edge of the through hole on the end surface of the ceramic cylinder, a fusible wire is obliquely attached to the through hole of the ceramic cylinder, and the wire It is an object of the present invention to provide a method of manufacturing a cylindrical current fuse that can fix the end of the wire to the end surface of the cylindrical body in a state where tension is applied to the cylindrical body.

  The cylindrical current fuse of the present invention is a method of manufacturing a cylindrical current fuse having a structure in which a fusible wire 16 is slanted in a through hole 12 inside a ceramic cylinder 11 when the wire 16 is fixed through the through hole 12. Further, eyelet-like solder 15 is formed at the edge of the through hole 12 of the cylindrical body 11 (see FIG. 5). Thereby, the edge part of the through-hole 12 which the wire 16 contacts can be made into the smooth curved surface R of a soft solder compared with ceramics, the stress concerning the wire 16 can be reduced, and the damage of the wire 16 can be prevented. .

  Further, when the fusible body wire 16 is fixed through the through hole 12, the wire 16 is pulled along the end surface of the ceramic cylinder 11, and the wire 16 is heated and welded to the solder 15 on the end surface of the cylinder 11. At the same time, the wire is cut (see FIG. 5). As a result, the wire 16 can be stretched obliquely without slack in the through-hole 12 in a state where tension is applied to the wire 16, and deterioration of the fusing characteristics due to the slack of the wire 16 can be prevented. Furthermore, since the wire 16 is cut at the solder 15 portion on the end surface of the cylinder, it is not necessary to pull out the wire 16 to the outer peripheral surface of the cylinder, and the structure of the cylinder 11 itself can be simplified.

It is sectional drawing of the step which formed eyelet-like solder on the ceramic cylinder end surface, stretched the soluble body wire, and cut it. It is sectional drawing which has arrange | positioned the disk-shaped solder board to the ceramic cylinder end surface. It is sectional drawing which punches out the part which covers the through-hole part of the solder board arrange | positioned at the cylinder end surface with a jig. It is sectional drawing of the step which formed eyelet-like solder. It is sectional drawing of the step which stretches and cut | disconnects a soluble body wire. It is sectional drawing after cut | disconnecting a soluble body wire. It is sectional drawing of the step of fitting a cap to a cylindrical body edge part. It is a perspective view of the step of fitting a cap on a cylindrical body end. It is an expanded sectional view in the stage where a cap was fitted to a cylindrical body end and soldered. It is a figure which shows the modification of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 10. In addition, in each figure, the same code | symbol is attached | subjected and demonstrated to the same or equivalent member or element.

  FIG. 1 shows an outline of a cylindrical current fuse of the present invention. This fuse includes a ceramic cylinder 11, an electrode cap 18 fixed to both ends of the cylinder, and a fusible wire installed in the inner through hole 12 of the cylinder and obliquely stretched between the electrode caps 18 and 18. 16 is a cylindrical current fuse including an eyelet-shaped solder 15 formed from the end surface of the cylinder 11 to the inner surface of the cylinder 11, and the wire 16 is connected to the end surface side of the cylinder of the solder 15 ( Temporarily fixed) It is characterized by being fixed.

  The end portion of the wire 16 does not reach the outer peripheral portion of the cylindrical body 11. That is, the end portion of the wire 16 is fixed to the solder 15 provided on the end surface of the cylindrical body 11, and is cut at the fixed portion. At the end of the wire 16, the solder 15 covering the edge of the through-hole 12 and the solder 19 loaded in the cap 18 are melted when the cap 18 is fixed later, and the inner surface of the cap 18 is joined by the integrated solder 20. (See FIGS. 7 and 9).

  As a result, the wire is conventionally pulled out to the outer peripheral surface of the cylindrical body, accommodated in a groove or the like provided on the outer peripheral surface, and temporarily fixed, but the end of the wire is fixed to the solder 15 with tension applied to the wire. Can be cut. Therefore, it is possible to stretch the wire obliquely without slacking in a state where tension is applied to the wire, and a conventional groove or the like provided on the outer peripheral surface of the cylindrical body is unnecessary, and a cylindrical current fuse having a simplified structure can be obtained.

  2 to 10 show a method of manufacturing a cylindrical current fuse according to an embodiment of the present invention. First, as shown in FIG. 2, a ceramic cylinder 11 having a substantially prismatic outer shape with a through hole 12 therein is prepared. Then, a disk-shaped solder plate 13 is disposed on the end surface of the cylinder 11. The solder plate 13 is preferably formed using Sn—Cu 4-15% solder which is hard and lead-free in order to form a smooth curved surface R at the edge of the cylinder.

  Then, as shown in FIG. 3, a jig (punch) 14 is punched from the solder plate 13 into the through hole 12. As a result, the solder plate 13 is deformed, and as shown in FIG. 4, a ring-shaped solder portion 15a is formed at the edge (corner portion) of the through-hole 12 on the end surface of the ceramic cylinder 11, and the through-hole is formed from the solder portion 15a. A grommet-like solder 15 is formed, which is composed of a solder portion 15b extending on the inner peripheral surface. By punching the plate-shaped solder with the jig 14 as described above, the opening portion of the cylindrical body 11 is covered with the solder 15, and a smooth curved surface R is formed from the end surface of the cylindrical body 11 to the inner wall surface. Although the illustrated example shows only one end face of the cylinder 11, the solder 15 is formed on both end faces of the cylinder 11.

  Next, as shown in FIG. 5, the fusible body wire 16 is obliquely stretched in the through hole 12. Specifically, the cylindrical body 11 is held by a jig (not shown), and the wire 16 is passed through the through hole 12 of the cylindrical body 11. Both ends of the wire 16 are held, and both ends of the wire 16 are substantially parallel to the end surface of the ceramic cylinder and a tension F is applied in the opposite direction. That is, a tension is applied to the end portion (not shown) of the wire 16 in a direction substantially parallel to and opposite to the tension F of the end portion shown in the figure. The wire 16 is in contact with the solder 15 in a state of being tensioned with the tension F, and maintains the tension F. The wire 16 is in sliding contact with the solder 15 while receiving the tension F, but the solder 15 is hard solder and has a smooth curved surface R formed at the inner peripheral edge, so that it is compared with the corner of a conventional ceramic cylinder. Thus, the amount of damage caused by rubbing can be reduced. It should be noted that the tension F may be a weak tension that can be stretched to such an extent that the wire 16 does not loosen.

  At this stage, the tip of the heater chip 17 is brought into contact with the fusible wire 16 on the solder 15a. The contact portion at the tip of the heater chip of the wire 16 is instantaneously heated above the melting point of the solder. By such heating, the wire 16 is fused to the solder 15a, and the wire is softened at the tip portion of the heater chip. Since the wire 16 is pulled with the tension F, the wire is cut at the tip portion of the heater chip, that is, the softened portion. FIG. 6 shows a state after the wire 16 is cut. In this state, the end portion 16a of the wire 16 is fixed on the end face of the ceramic cylinder 11, and the tension is obliquely slackened in the through hole 12 while maintaining the tension F. Although the illustrated example shows only one end face of the ceramic cylinder 11, the wire fixing portions 16 a are formed on both end faces of the ceramic cylinder 11. The solder 15 is deformed by the pressing pressure and heating of the heater chip 17 and protrudes into the through hole 12. The protruding solder 15 wraps the wire 16 and simultaneously fills the through hole 12.

  In the current fuse manufacturing method, there are various methods for cutting the wire. First, there is a method of cutting with a blade. In addition, when cutting with a cutter, it has a blade life and needs to be replaced periodically. Next, there is a method of cutting with a tensile load. However, in this case, for example, the maximum wire diameter requires a load of 1 kg, which is large in terms of equipment. Further, since the breaking load is applied to the entire wire, the wire is extended and at the same time, there is a possibility that the breaking point is not constant. There is also a method of crushing and cutting the wire. However, there is a problem that the wire is damaged such as bending and the characteristics are deteriorated. In the above-described method, the wire is softened and the wire is cut by tension using the force for holding the wire and the soldering heat. Therefore, the wire is not damaged, and the wire can be easily cut with a simple equipment configuration.

  Next, as shown in FIGS. 7 and 8, caps 18 including solder 19 inside are fitted to both ends of the ceramic cylinder 11. FIG. 8 shows a state in which the wire end portion 16a is exposed. As shown in FIG. 6 and the like, all or a part of the wire end portion 16a is covered with the solder 15a. Then, the cap 18 is heated to melt the solders 19 and 15, and the end 16 a of the wire is joined to the cap 18. This state is shown in FIG. Here, the solder 20 is formed by melting the solders 19 and 15. The manufacturing process of the current fuse of the present invention is completed by this cap fitting process. At this point, the wire 16 is somewhat loosened from the state shown in FIG. 6, but the amount of looseness is slight. And since the edge part 16a of a wire is fixed to the sandwich form by the homogeneous solders 19 and 15, organic substance etc. are not included but a fusing characteristic can be made favorable. Further, the cap 18 may be formed with a convex portion 18c as shown in FIG. Thereby, the cap 18 fitted to the end of the cylindrical body 11 is difficult to come off. 7 and 10, the solder 19 inside the cap is illustrated. However, if the amount of the eyelet-shaped solder to be formed first is sufficient to connect the wire 16 and the cap 18, The solder 19 may be omitted.

  According to the above-described current fuse manufacturing method, solder is punched and formed at the edge of the through hole on the end face of the cylinder, so that the inner peripheral edge of the solder has an edge (corner) of the base ceramic cylinder. A smooth curved surface R is formed regardless of the shape. As a result, the edge of the through hole with which the wire comes into contact can be made a smooth curved surface R, and can be made of a softer solder than ceramics, and the stress applied to the wire when the wire is fixed can be reduced. Damage can be reduced. It is more preferable to use in combination the above-described method of covering the inner peripheral edge with eyelet-shaped solder and a structure in which appropriate roundness (curvature radius R) is formed in advance on the inner peripheral edge and the outer peripheral edge of the ceramic cylinder. .

  Furthermore, when fixing the wire through the through-hole, the wire was pulled along the end surface of the cylinder, the wire was fixed to the solder on the end surface of the cylinder, and the wire was cut to apply tension to the wire. In the state, it can be stretched diagonally without slack in the through hole. Thereby, deterioration of the fusing characteristic based on contact with the inner wall surface of the through hole due to loosening of the wire can be reduced.

  Further, when the wire is fixed, the wire is cut at the solder portion on the end face of the cylindrical body. Thereby, it is not necessary to pull out the wire to the outer peripheral surface of the cylinder, the groove 2 required in Patent Document 1 is unnecessary, the structure of the cylinder itself can be simplified, and the manufacturing process can be simplified. Therefore, according to the present invention, it is possible to mass-produce cylindrical current fuses with little variation in fusing characteristics in a process that is easy to automate.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

  The present invention can be used for manufacturing a cylindrical current fuse suitable for surface mounting.

Claims (6)

In the method of manufacturing a cylindrical current fuse having a structure in which a fusible wire is slanted in a through hole inside a ceramic cylinder,
When the wire is fixed through the through hole, solder is formed in advance at the edge of the through hole on both end faces of the cylindrical body, and the wire is fixed with the solder. Method.   When fixing the wire through the through-hole, the wire is pulled along both end surfaces of the cylindrical body, the wire is fixed to the solder on both end surfaces of the cylindrical body, and the wire is broken. The method of manufacturing a cylindrical current fuse according to claim 1, wherein:   A solder disk is arranged on the end surface of the cylinder, and a jig is punched out from the solder disk to the through hole, so that the edge of the through hole on the end surface of the cylinder has a solder portion on the ring and the solder portion. 2. The method of manufacturing a cylindrical current fuse according to claim 1, wherein the solder is formed of a solder portion on the inner peripheral surface of the through hole that extends.   2. The method of manufacturing a cylindrical current fuse according to claim 1, wherein the solder is formed by using lead-free and hard Sn—Cu 4 to 15% solder. 3. A cylindrical current fuse comprising a ceramic cylinder, electrode caps fixed to both ends of the cylinder, and a fusible wire installed inside the cylinder and stretched between the electrode caps,
Solder formed from the end surface of the cylindrical body to the inner surface of the cylindrical body,
Cylindrical, characterized in that said end of the wire is fixed on the end face than the extended surface from the inner wall surface of the cylindrical body of the solder, the end of the wire does not extend to the outer peripheral portion of the cylindrical body Current fuse. The cylindrical current fuse according to claim 5, wherein the solder covering the edge of the through hole and the solder loaded in the cap are melted and fixed with an integrated solder.

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