Fuse

Abstract

To provide a fuse capable of coping with change in heat capacity of a fuse element accompanied by omission of a protective cylinder with a simple configuration.SOLUTION: A fuse includes two resistance wires 8 continuous in one direction, and a fusible alloy portion 5 for electrically connecting overlapping end portions of the two resistance wires 8. The fusible alloy portion 5 includes a body unit 55 extending in the one direction, and projection portions 51, 52 provided on at least one end side of the body unit 55 and projecting in the one direction more than other portions 53, 54.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a fuse.

Background Art

[0002] A time-lag fuse having a fuse element in which the ends of two connected resistance wires are electrically connected by a fusible body, a head terminal is connected to one resistance wire, and a lead wire is connected to the other resistance wire, and the fuse element is covered with a coating cylinder is widely spread.

[0003] For example, in Patent Document 1, a time-lag fuse is disclosed in which a stopper is provided near the opening end in order to prevent the lead wire from coming out of the coating cylinder opening and hanging down when the fusible body is melted by an overcurrent while a tensile force is applied to the lead wire.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventionally, hard vinyl chloride has been used as the material of the coating cylinder. In this case, in order to prevent the coating cylinder from being damaged by the alloy that scatters when the fusible body is melted, the periphery of the fusible body is surrounded by a protective cylinder.

[0006] Since the protective cylinder is always in contact with the fusible body, a part of the heat transmitted to the fusible body is conducted to the protective cylinder. Therefore, it has been necessary to consider the protective cylinder when calculating the heat capacity related to the melting of the fusible body.

[0007] On the other hand, with the discontinuation of the use of rigid vinyl chloride as the material of the coating cylinder, the protection cylinder has also become unnecessary. However, since the heat capacity of the protection cylinder is included in the calculation of the heat capacity related to the fusing of the fusible body, when omitting the protection cylinder, it is necessary to increase the heat capacity of the fusible body by only the heat capacity of the protection cylinder, or to lower the electrical resistance value to reduce the heat generation amount of the resistance wire.

[0008] To increase the heat capacity of the fusible body, methods such as increasing the diameter of the fusible body can be considered. However, when the diameter increases, there is a risk that the fusible body may come into contact with the coating cylinder. Also, to lower the electrical resistance value, a method of shortening the distance between the lead wire and the head terminal can be considered. However, when such a distance is shortened, there is a problem that the minimum fusing current related to the fusing of the fusible body increases because heat escapes to the head terminal and the lead wire.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a fuse that can cope with a change in the heat capacity of a fuse element accompanying the omission of the protection cylinder with a simple configuration.

Means for Solving the Problems

[0010] The fuse according to the present invention is a fuse including two resistance wires connected in series in one direction and a fusible alloy part that electrically connects the overlapping end parts of the two resistance wires, wherein the fusible alloy part includes a body part extending in the one direction and a protruding part provided on at least one end side of the body part and protruding in the one direction more than other parts.

Effects of the Invention

[0011] According to the present invention, with a simple configuration, it is possible to cope with a change in the heat capacity of the fuse element accompanying the omission of the protection cylinder.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0013] Hereinafter, the fuse according to the present invention will be described based on the drawings showing its embodiments.

[0014] (Embodiment 1) FIG. 1 is an explanatory diagram showing the configuration of a fuse 10 according to Embodiment 1. The fuse 10 according to Embodiment 1 is a so-called time-lag fuse, and a fuse element 2 is accommodated in a covering cylinder 1. In FIG. 1, for the sake of convenience, a state in which a part of the covering cylinder 1 is removed along the length direction of the covering cylinder 1 is shown.

[0015] The covering cylinder 1 has, for example, an elongated cylindrical shape and is made of pressboard or kraft paper. As described above, a fuse element 2 is accommodated in the covering cylinder 1, and a part of a lead wire 7 described later is further accommodated. The covering cylinder 1 protects the fuse element 2 against mechanical pressure from the outside and prevents the fuse element 2 from being affected by the fusing characteristics. Further, when the current is interrupted, the covering cylinder 1 is heated by an arc to emit arc-extinguishing gas, and the arc is neutralized to improve the interruption performance.

[0016] The fuse element 2 has two resistance wires 8 and a fusible alloy part 5 that electrically connects the ends of the two resistance wires 8. The resistance wires 8 include a first resistance wire 81 and a second resistance wire 82 that are connected in series along the axial direction (one direction) of the covering cylinder 1. One end of the first resistance wire 81 is connected to a head terminal 6 described later, and one end of the second resistance wire 82 is connected to a lead wire 7 described later.

[0017] The first resistance wire 81 and the second resistance wire 82 have the opposite ends in the axial direction of the coating cylinder 1 overlapping each other. That is, the other end of the first resistance wire 81 and the other end of the second resistance wire 82 overlap each other over a predetermined range when viewed in the radial direction of the coating cylinder 1.

[0018] The fusible alloy part 5 is a low-melting-point alloy with low electrical conductivity such as a solder alloy, and as described above, connects the other end of the first resistance wire 81 and the other end of the second resistance wire 82 by condensation. The fusible alloy part 5 extends along the axial direction of the coating cylinder 1.

[0019] FIG. 2 is a perspective view showing the fuse element 2 of the fuse 10 according to Embodiment 1. The fusible alloy part 5 has a body part 55 extending in the axial direction of the coating cylinder 1 and protruding parts 51 and 52 respectively provided at both ends of the body part 55. Specifically, the protruding part 51 is provided on the side of the first resistance wire 81, and the protruding part 52 is provided on the side of the second resistance wire 82.

[0020] The body part 55 has an elliptical capsule shape in a cross-sectional view along the length direction. As described above, the protruding part 51 is provided at one end of the body part 55, and the protruding part 52 is provided at the other end of the body part 55.

[0021] The protruding part 51 is a part that protrudes in the axial direction of the coating cylinder 1 more than the other part 53 at one end of the body part 55. Here, the other part 53 is one end surface of the body part 55 where the protruding part 51 is not provided. Also, the protruding part 52 is a part that protrudes in the axial direction of the coating cylinder 1 more than the other part 54 at the other end of the body part 55. Here, the other part 54 is the other end surface of the body part 55 where the protruding part 52 is not provided. In other words, the protruding part 51 protrudes toward the head terminal 6 side, and the protruding part 52 protrudes toward the lead wire 7 side.

[0022] The protruding parts 51 and 52 surround the periphery of the resistance wire 8 and cover the outer peripheral surface. FIG. 3 is a partial cross-sectional view showing the fuse element 2 of the fuse 10 according to Embodiment 1. As shown in FIG. 3, the protrusion 51 is provided around the first resistance wire 81, and the protrusion 52 is provided around the second resistance wire 82. In other words, the first resistance wire 81 is covered by the protrusion 51, and the second resistance wire 82 is covered by the protrusion 52.

[0023] That is, the other end of the first resistance wire 81 includes an embedded portion embedded in the body portion 55 and a covering portion covered by the protrusion 51 following the embedded portion, and the other end of the second resistance wire 82 includes an embedded portion embedded in the body portion 55 and a covering portion covered by the protrusion 52 following the embedded portion. In other words, the embedded portion of the first resistance wire 81 and the embedded portion of the second resistance wire 82 overlap in a radial view of the covering cylinder 1.

[0024] The protrusion 51 and the protrusion 52 do not protrude in the radial direction of the body portion 55 more than the peripheral surface of the body portion 55. Also, the dimensions L1 of the protrusion 51 and the protrusion 52 in the axial direction of the body portion 55 are the same. For example, the protrusion 51 and the protrusion 52 have the same shape. As shown in FIG. 3, the dimension L1 is the dimension from the tip 811 (the abutment described later) of the embedded portion of the first resistance wire 81 to the tip of the protrusion 52, and the dimension from the tip 821 of the embedded portion of the second resistance wire 82 to the tip of the protrusion 51.

[0025] Therefore, the embedded portions of the first resistance wire 81 and the second resistance wire 82 have the same length, and the covering portions of the first resistance wire 81 and the second resistance wire 82 also have the same length.

[0026] In the first resistance wire 81, the tip 811 of the embedded portion abuts against the other portion 54 on the opposite side (the other end side) of the protrusion 51 covering the first resistance wire 81 from the inside of the body portion 55. Also, in the second resistance wire 82, the tip 821 of the embedded portion abuts against the other portion 53 on the opposite side (one end side) of the protrusion 52 covering the second resistance wire 82 from the inside of the body portion 55.

[0027] That is, at one end of the body portion 55, the protruding portion 51 protrudes to cover the first resistance wire 81, and at the other portion 53 corresponding to the protruding portion 51, the tip 821 of the embedded portion of the second resistance wire 82 abuts from the inside of the body portion 55. At the other end of the body portion 55, the protruding portion 52 protrudes to cover the second resistance wire 82, and at the other portion 54 corresponding to the protruding portion 52, the tip 811 of the embedded portion of the first resistance wire 81 abuts from the inside of the body portion 55.

[0028] The first resistance wire 81, the second resistance wire 82, and the fusible alloy portion 5 related to the fuse element 2 are integrally manufactured by, for example, casting.

[0029] At one end of the first resistance wire 81, as described above, the head terminal 6 is connected. The head terminal 6 is made of a conductive metal and has an elongated cylindrical portion 61 disposed within the covering cylinder 1 and a disc-shaped portion 62. The cylindrical portion 61 has an outer diameter smaller than the inner diameter of the covering cylinder 1 and extends along the axial direction of the covering cylinder 1. One end of the first resistance wire 81 is inserted and fixed into one end of the cylindrical portion 61, and a disc-shaped portion 62 is continuously provided perpendicular to the axis of the cylindrical portion 61 at the other end of the cylindrical portion 61. The disc-shaped portion 62 has a diameter larger than the outer diameter of the covering cylinder 1 and is attached to one of the electrodes. For example, the cylindrical portion 61 and the disc-shaped portion 62 are integrally formed.

[0030] Note that a cylindrical spacer 11 is externally fitted to the cylindrical portion 61. The spacer 11 is made of, for example, an insulating material, has an outer diameter slightly smaller than the inner diameter of the covering cylinder 1, and an inner diameter slightly larger than the outer diameter of the cylindrical portion 61, and holds the cylindrical portion 61 so as to be located on the same axis as the covering cylinder 1.

[0031] One end of the second resistance wire 82 is connected to the lead wire 7 as described above. The lead wire 7 is composed of a plurality of bundled copper wires, and a metal cap 9 is put on one end on the side of the second resistance wire 82. The cap 9 has a cylindrical shape. One end of the lead wire 7 is inserted into and fixed in the cap 9 from one end side of the cap 9, and one end of the second resistance wire 82 is inserted into and fixed in the cap 9 from the other end side of the cap 9. The other end of the lead wire 7 is fixed to another electrode corresponding to the electrode to which the head terminal 6 is connected, and a tensile force is applied to the lead wire 7.

[0032] In the fuse 10 according to Embodiment 1 having the above-described configuration, when an overcurrent equal to or higher than the threshold flows through the fuse 10 (fuse element 2), the fusible alloy portion 5 begins to melt due to the heat generation of the resistance wire 8. As described above, since a tensile force is applied to the lead wire 7, when the overcurrent flows for a predetermined time, the fusible alloy portion 5 is melted and the first resistance wire 81 and the second resistance wire 82 are separated. As a result, the current between the head terminal 6 (one electrode) and the lead wire 7 (the other electrode) is interrupted.

[0033] Conventionally, hard vinyl chloride has been used as the material of the coating cylinder. In this case, when the fusible alloy portion is melted, the coating cylinder may be damaged by the scattered alloy. Therefore, in preparation for this, the periphery of the fusible alloy portion is surrounded by a so-called kraft cylinder. That is, conventionally, a kraft cylinder is interposed between the fusible alloy portion of the fuse element and the coating cylinder, and the kraft cylinder is always in contact with the fusible alloy portion.

[0034] Therefore, conventionally, in the design of the fuse, the kraft cylinder has been considered. That is, since the kraft cylinder is always in contact with the fusible alloy portion, a part of the heat transmitted to the fusible alloy portion is conducted to the kraft cylinder. Therefore, when calculating the heat capacity related to the melting of the fusible alloy portion, it is necessary to add and subtract the amount corresponding to the kraft cylinder.

[0035] On the one hand, with the discontinuation of the use of rigid vinyl chloride as the material for the coating cylinder, the kraft cylinder has also become unnecessary. However, since the heat capacity of the kraft cylinder is included in the calculation of the heat capacity related to the fusing of the fusible alloy part, when omitting the kraft cylinder, it is necessary to increase the heat capacity of the fusible alloy part only by the heat capacity of the kraft cylinder, or to reduce the electrical resistance value to reduce the calorific value.

[0036] First, to increase the heat capacity of the fusible alloy part, there are methods of increasing the diameter or the length of the fusible alloy part. However, if the diameter becomes larger, there is a risk of contact with the coating cylinder, and the design freedom is restricted. Also, if the length of the fusible alloy part becomes longer, the embedded part of the resistance wire embedded in the fusible alloy part, that is, the overlapping part of the resistance wires, becomes longer, and the inter-pole distance (distance between the other ends of the resistance wires) during the current interruption operation becomes shorter, resulting in a risk of non-interruption.

[0037] And to reduce the electrical resistance value, there is a method of shortening the distance between the lead wire and the head terminal, that is, the effective length which is the length of the fuse element. However, when the effective length is shortened, there is a problem that the minimum fusing current related to the fusing of the fusible alloy part increases because heat escapes to the head terminal and the lead wire.

[0038] In contrast, in the fuse 10 according to Embodiment 1, as described above, by providing the protruding part 51 and the protruding part 52 at both ends of the body part 55 of the fusible alloy part 5 respectively, the problems associated with the omission of the above-described kraft cylinder are solved.

[0039] That is, in the fuse 10 according to Embodiment 1, by adding the protruding part 51 and the protruding part 52 to the body part 55 similar to the conventional one, the heat capacity of the entire fusible alloy part 5 is increased, compensating for the reduction in heat capacity caused by the omission of the kraft cylinder. Also, in the fuse 10 according to Embodiment 1, since the protruding part 51 and the protruding part 52 are provided at both ends of the body part 55, it is not necessary to increase the diameter of the fusible alloy part 5. Furthermore, the protruding part 51 and the protruding part 52 are partially provided on both end faces of the body part 55, and the embedded parts of the first resistance wire 81 and the second resistance wire 82, that is, the parts where the first resistance wire 81 and the second resistance wire 82 overlap each other, are not expanded.

[0040] Also, in the fuse 10 according to Embodiment 1, as described above, the tip 811 of the embedded portion of the first resistance wire 81 abuts against the other portion 54 on the side opposite to the protruding portion 51 from the inside of the body portion 55, and the tip 821 of the embedded portion of the second resistance wire 82 abuts against the other portion 53 on the side opposite to the protruding portion 52 from the inside of the body portion 55. That is, when manufacturing the fuse element 2 by casting, the operator pushes in the first resistance wire 81 and the second resistance wire 82 until the ends abut against the mold. Therefore, the length of the embedded portion of the resistance wire 8 can be maintained constant with a simple operation, and the current interruption performance of the fuse 10 can be stabilized.

[0041] Furthermore, in the fuse 10 according to Embodiment 1, as described above, since the protruding portion 51 and the protruding portion 52 have the same shape, when connecting the head terminal 6 and the lead wire 7 to the fuse element 2, the operator does not need to worry about the connection direction of the fuse element 2, and the workability can be improved.

[0042] (Embodiment 2) The fuse 10 according to Embodiment 2 includes a coating cylinder 1 and a fuse element 2 accommodated in the coating cylinder 1, similar to Embodiment 1.

[0043] The fuse element 2 has a first resistance wire 81 and a second resistance wire 82, and a fusible alloy portion 5A that electrically connects the ends of the first resistance wire 81 and the second resistance wire 82. One end of the first resistance wire 81 is connected to the head terminal 6, and one end of the second resistance wire 82 is connected to the lead wire 7.

[0044] In the fuse 10 according to Embodiment 2, the shape of the fusible alloy portion 5A is different from that of the fusible alloy portion 5 of the fuse 10 according to Embodiment 1. FIG. 4 is a perspective view showing the fuse element 2 of the fuse 10 according to Embodiment 2.

[0045] The soluble alloy part 5A has a body part 55A extending in the axial direction of the coating cylinder 1, and protruding parts 51A and 52A respectively provided at both ends of the body part 55A. On the side of the first resistance wire 81, the protruding part 51A is provided, and on the side of the second resistance wire 82, the protruding part 52A is provided.

[0046] The body part 55A has a cylindrical shape that is a parallelogram in a sectional view along the length direction. That is, both end faces in the length direction of the body part 55A are flat surfaces inclined with respect to the axial direction of the body part 55A. Both end faces of the body part 55A are elliptical and parallel to each other.

[0047] As described above, the protruding part 51A is provided at one end of the body part 55A, and the protruding part 52A is provided at the other end of the body part 55A respectively. The protruding parts 51A and 52A are parts that respectively surround the first resistance wire 81 and the second resistance wire 82. That is, the protruding part 51A protrudes in the axial direction of the coating cylinder 1 more than the other part 53A on one end face of the body part 55A, and the protruding part 52A protrudes in the axial direction of the coating cylinder 1 more than the other part 54A on the other end face of the body part 55A.

[0048] FIG. 5 is a partial cross-sectional view showing the fuse element 2 of the fuse 10 according to Embodiment 2. As shown in FIG. 5, the first resistance wire 81 is covered by the protruding part 51A, and the second resistance wire 82 is covered by the protruding part 52A. The embedded part of the first resistance wire 81 and the embedded part of the second resistance wire 82 overlap in a radial view of the coating cylinder 1.

[0049] The protruding part 51A and the protruding part 52A do not protrude in the radial direction of the body part 55A more than the circumferential surface of the body part 55A. The protruding part 51A and the protruding part 52A have the same dimension L2 in the axial direction of the body part 55A. For example, the protruding part 51A and the protruding part 52A have the same shape. Therefore, the embedded part of the first resistance wire 81 and the embedded part of the second resistance wire 82 have the same length, and the covered part of the first resistance wire 81 and the covered part of the second resistance wire 82 also have the same length.

[0050] In the first resistance wire 81, the tip 811 of the embedded portion abuts against the other portion 54A on the side opposite to the protruding portion 51A (the other end side) from the inside of the body portion 55A. In the second resistance wire 82, the tip 821 of the embedded portion abuts against the other portion 53A on the side opposite to the protruding portion 52A (one end side) from the inside of the body portion 55A.

[0051] Since it has the configuration as described above, similar to Embodiment 1, the fuse 10 according to Embodiment 2 can also increase the heat capacity of the entire fusible alloy portion 5A by adding the protruding portion 51A and the protruding portion 52A, and solve the problems associated with the omission of the kraft tube described above.

[0052] Also, in the fuse 10 according to Embodiment 2, as described above, the tip 811 of the embedded portion of the first resistance wire 81 abuts against the other portion 54A on the side opposite to the protruding portion 51A from the inside of the body portion 55A, and the tip 821 of the embedded portion of the second resistance wire 82 abuts against the other portion 53A on the side opposite to the protruding portion 52A from the inside of the body portion 55A. Therefore, similar to Embodiment 1, the length of the embedded portion of the resistance wire 8 can be maintained constant with a simple operation, and the current interruption performance of the fuse 10 can be stabilized.

[0053] Furthermore, in the fuse 10 according to Embodiment 2, as described above, since the protruding portions 51A and 52A have the same shape, the workability when connecting the head terminal 6 and the lead wire 7 to the fuse element 2 can be improved.

[0054] For the parts similar to those in Embodiment 1, the same reference numerals are given and the detailed description is omitted.

[0055] In the above Embodiments 1 to 2, the case where the protruding portions 51 and 52 are provided at both ends of the body portion 55 and the protruding portions 51A and 52A are provided at both ends of the body portion 55A has been described as an example, but it is not limited thereto. A configuration in which either one of the protruding portions 51 and 52 is provided on the body portion 55 and either one of the protruding portions 51A and 52A is provided on the body portion 55A may also be acceptable.

[0056] In addition, in the above-described Embodiments 1 and 2, the cases where the protruding portions 51 and 52 have the same shape and where the protruding portions 51A and 52A have the same shape have been described respectively, but the present invention is not limited thereto. For example, the protruding portions 51 and 52 may have different shapes respectively, or the protruding portions 51A and 52A may have different shapes respectively.

[0057] Furthermore, in the above-described Embodiments 1 and 2, the case where the tip 811 of the embedded portion of the first resistance wire 81 abuts against the other portions 54 and 54A on the opposite side and the tip 821 of the embedded portion of the second resistance wire 82 abuts against the other portions 53 and 53A on the opposite side has been described, but the present invention is not limited thereto. A configuration may be adopted in which the tip 811 of the embedded portion of the first resistance wire 81 does not abut against the other portions 54 and 54A on the opposite side and the tip 821 of the embedded portion of the second resistance wire 82 does not abut against the other portions 53 and 53A on the opposite side.

[0058] The technical features (constituent elements) described in Embodiments 1 and 2 can be combined with each other, and by combining them, new technical features can be conceived. The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

[0059] The matters described in each embodiment can be combined with each other. In addition, the independent claims and dependent claims described in the claims can be combined with each other in all possible combinations regardless of the citation form. Furthermore, the claims use a form (multi-claim form) in which a claim that cites two or more other claims is described, but the present invention is not limited thereto. A form in which a multi-claim (multi-multi-claim) that cites at least one multi-claim is described may be used.

Explanation of Reference Numerals

[0060] 1: Coating cylinder, 2: Fuse element, 5, 5A: Fusible alloy part, 6: Head terminal, 7: Lead wire, 8: Resistance wire, 10: Fuse, 51, 52, 51A, 52A: Protrusion, 53, 54, 53A, 54A: Other parts, 55, 55A: Body part, 81: First resistance wire, 82: Second resistance wire

Claims

1. A fuse comprising two resistive wires connected in series in one direction and a fusible alloy part for electrically connecting the overlapping ends of the two resistive wires, wherein the fusible alloy part comprises a body part extending in the one direction, and a protruding part provided on at least one end side of the body part and protruding in the one direction more than the other parts.

2. The fuse according to claim 1, wherein the protruding part is provided around the resistive wire.

3. The protruding part is provided around one of the resistive wires, and the end of the other resistive wire is embedded in the body part in a state of abutting against the other part from the inside of the body part. The fuse according to claim 1.

4. The fuse according to any one of claims 1 to 3, wherein the protruding parts are respectively provided at both ends of the body part.

5. The fuse according to claim 4, wherein the two protruding parts provided at both ends of the body part have the same shape.

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