Fuse element

Abstract

To obtain an inexpensive fuse element that can be surely fused by a constant fusing current.SOLUTION: A plate-shaped base body 10 in which flat plate-shaped terminal units 11, 12 are connected by a thin wiring unit 13, and provided with a low melting point metal holding unit 14 in the wiring unit 13, and a low melting point body 15 fixed to the low melting point metal holding part 14 are provided. The low-melting-point body 15 is fixed to the low melting point metal holding unit 14 by using a holding opening 14A. The holding opening 14A is formed not at a center of the low melting point metal holding unit 14 in a current flow direction, but asymmetrically up and down biased toward a side where the first wiring portion 131 is located.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuse element configured to open due to an overcurrent. [Background technology]

[0002] For safety reasons, fuse elements that melt a current path when an overcurrent occurs are widely used in automobiles and the like. Such fuse elements have a variety of structures, and among them, as described in Patent Document 1, for example, a fuse element that combines a substrate made of a conductive metal (such as copper) with a low-melting-point body made of a low-melting-point metal (such as tin) is known.

[0003] FIG. 3 is a perspective view showing a simplified schematic of the structure of this fuse element 9. Here, a base 90 is used in which flat terminal portions 91 and 92 are connected by a wiring portion 93. A low-melting-point metal holding portion 94 having a circular outer shape with a locally wider width is provided in the center of the wiring portion 93, and a circular holding opening 94A is formed in the low-melting-point metal holding portion 94 concentrically therewith. This gives the low-melting-point metal holding portion 94 an annular shape. Because the base 90 is formed from a single metal plate, the wiring portion 93 and the low-melting-point metal holding portion 94 have the same (uniform) thickness.

[0004] A low-melting-point body 95 made of a low-melting-point metal is fixed to the low-melting-point metal holding portion 94. The holding opening 94A can be used for this fixation. For example, a wire made of a low-melting-point metal can be inserted into the holding opening 94, cut to a short length, and then crimped to fix the wire to the low-melting-point metal holding portion 94 as the low-melting-point body 95.

[0005] In this fuse element 9, when a large current flows between the terminals 91 and 92, heat is generated in the low-melting-point metal holding portion 94, causing the low-melting-point body 95 to melt while fixed. This causes the low-melting-point metal (e.g., tin) constituting the low-melting-point body 95 to form an alloy with the metal (e.g., copper) constituting the low-melting-point metal holding portion 94 (base 90). The melting point of this alloy is higher than that of the original low-melting-point metal (e.g., tin) but lower than that of the original metal (e.g., copper). In other words, this portion of the base 90 has a low melting point, which melts the portion of the low-melting-point metal holding portion 94 in the wiring portion 93, thereby interrupting the current path. Meanwhile, while low-melting-point metals generally have low mechanical strength, the high mechanical strength of this fuse element 9 is maintained by the metal constituting the base 90 when the low-melting-point body 95 is not melted.

[0006] 4 is a plan view schematically showing the current path near the low-melting-point metal holding portion after the low-melting-point body 95 has melted. This configuration directly reflects the configuration of the base 90 (low-melting-point metal holding portion 94, wiring portion 93), so the current path is as shown by the arrows in FIG. 4. The portion of this path that is the thinnest and most likely to melt is the annular-shaped portion of the low-melting-point metal holding portion 94, and such melting is particularly likely to occur in areas A1 and A2.

[0007] Here, the base 90, which is the main body of the fuse element 9, can be easily manufactured from a single metal plate by sheet metal processing or the like. Since the process of fixing the low-melting-point body 95 can also be easily performed as described above, the fuse element 9 can be manufactured inexpensively. Furthermore, the mechanical strength of the fuse element 9 in an unblown state is maintained by the metal that constitutes the base 90. For this reason, the fuse element 9 is provided in multiple locations in, for example, an automobile. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2018-101506 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0009] In the structures shown in Figures 3 and 4, a large current causes a portion of the low-melting-point metal holding portion 94 to melt. However, in this case, it is not always certain which portion of the annular low-melting-point metal holding portion 94 melts. For example, melting may occur in regions A1 and A2 in Figure 4. However, in reality, both regions do not melt simultaneously; one melts first. In this case, which region melts first depends on factors such as the processing accuracy (positional accuracy) of the holding opening 94A, and is generally not determined. For example, if region A1 melts first, the molten metal components may adhere to the opposing region A2, which may effectively thicken region A2, reducing its electrical resistance and making it more difficult to melt.

[0010] Fuse elements are required to reliably fuse the current path at a certain set fusing current (or to maintain high insulation resistance), but when this situation occurs, it becomes difficult to reliably fuse at a constant fusing current.

[0011] That is, there is a demand for an inexpensive fuse element that can be reliably blown with a constant fusing current.

[0012] The present invention has been made in view of the above circumstances, and has as its object to solve the above problems. [Means for solving the problem]

[0013] The present invention provides a fuse element that partially fuses to cut off a current path when a fusing current of a predetermined magnitude flows, the fuse element having a wiring portion through which the current flows and a low-melting-point metal holding portion formed locally in the middle of the wiring portion and thicker than the wiring portion, the fuse element comprising: a base body having a plate-like structure made of metal; and a low-melting-point body fixed to a holding opening that is an opening that passes through the low-melting-point metal holding portion and made of a low-melting-point metal having a melting point lower than that of the metal, wherein, in a plan view, the low-melting-point metal holding portion has a A first wiring portion and a second wiring portion, which are parts of the wiring portion, are connected to the low-melting point metal portion on one side and the other side in the direction of current flow, respectively, and the holding opening is formed in the low-melting point metal holding portion so as to be biased in a direction along the current flow direction so that the distance between the holding opening and the first wiring portion is smaller than the distance between the holding opening and the second wiring portion, thereby forming an area on the one side in the low-melting point metal holding portion where the width of the current path is locally narrowed. The low-melting-point metal holding portion and the holding opening may have a circular outer shape in a plan view. In a plan view, the regions in the low-melting point metal holding portion where the current density is locally high may be formed at two locations along a direction perpendicular to the current flow direction, and when the minimum line widths in the regions are X1 and X2, respectively, and the widths perpendicular to the current flow direction of the first wiring portion and the second wiring portion are W1 and W2, respectively, W1 > X1 + X2 and W2 > X1 + X2 may be satisfied. W1 <W2とされていてもよい。 In a plan view, the holding opening may be formed only in a region on the one side of the center of the low-melting-point metal holding portion in the current-carrying direction. [Effects of the Invention]

[0014] Since the present invention is configured as described above, it is possible to reliably fuse with a constant fusing current, and it is possible to obtain an inexpensive fuse element. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view of a fuse element according to an embodiment. [Figure 2] FIG. 2 is a plan view of the periphery of a low-melting-point metal holding portion in the fuse element according to the embodiment. [Figure 3] FIG. 1 is a perspective view of a conventional fuse element. [Figure 4] FIG. 10 is a plan view of the periphery of a low-melting-point metal holding portion in a conventional fuse element. DETAILED DESCRIPTION OF THE INVENTION

[0016] A fuse element according to an embodiment of the present invention will be described. Fig. 1 is a perspective view corresponding to Fig. 3, showing the structure of this fuse element 1. Like the fuse element 9 described above, this fuse element 1 also has flat terminal portions 11 and 12 connected by a thin wiring portion 13, a plate-like base 10 on which a low-melting-point metal holding portion 14 is provided in the wiring portion 13, and a low-melting-point body 15 fixed to the low-melting-point metal holding portion 14. Similarly, the low-melting-point body 15 is fixed to the low-melting-point metal holding portion 14 using a holding opening 14A formed in the low-melting-point metal holding portion 14.

[0017] Furthermore, as described above, the base 10 is manufactured by processing a metal plate. Therefore, the wiring portion 13 and the low-melting-point metal holding portion 14 are made of a common metal plate and are the same thickness. This is also similar to the base 90 in the fuse element 9 described above. Therefore, the fuse element 1 can be manufactured inexpensively, and the mechanical strength in the unblown state is maintained by the base 10.

[0018] However, in this fuse element 1, the configuration of the low-melting-point metal holding portion 14 is different from that of the fuse element 9, and the positional relationship between the holding opening 14A and the low-melting-point metal holding portion 14 is different. Fig. 2 is a plan view showing the configuration of the base 10 near the low-melting-point metal holding portion 14. Here, the upper and lower portions of the low-melting-point metal holding portion 14 of the wiring portion 13 in Fig. 1 are distinguished and described as a first wiring portion 131 and a second wiring portion 132, respectively, and the wiring width of the first wiring portion 131 is W1, and the wiring width of the second wiring portion 132 is W2 (W2 > W1). The direction in which current flows through this low-melting-point metal holding portion 14 is the current flow direction C (the vertical direction in Fig. 2).

[0019] Here, the holding opening 14A is formed asymmetrically in the vertical direction, biased toward the side where the first wiring portion 131 is located (the upper side in FIG. 2), rather than in the center of the low-melting-point metal holding portion 14 along the current flow direction C. With this configuration, in the low-melting-point metal holding portion 14, as shown in regions B1 (left side) and B2 (right side) in the figure, portions where the current path is locally narrow are formed, and these regions are blown out by a large current.

[0020] Furthermore, because melting is likely to occur in each of the two regions B1 and B2, one of them will melt first, similar to regions A1 and A2 in Fig. 4. However, regions B1 and B2 are adjacent (closer) to regions A1 and A2 in Fig. 4, and therefore it is less likely that only region B1 will melt and region B2 will not. In fact, when these regions melt, the low-melting-point metal holding portion 14 and the first wiring portion 131 will melt and be separated. For this reason, even if one of regions B1 and B2 melts first, it is always the portion of this fuse element 1 between the low-melting-point metal holding portion 14 and the first wiring portion 131 that will ultimately melt due to the large current.

[0021] Specifically, by adjusting the vertical position of the holding opening 14A in FIG. 2, the minimum line widths X1 in region B1 and X2 in region B2 in FIG. 2 can be set, and X1, X2 << W1, X1 + X2 << W2 can be achieved. Here, in order to particularly stably fuse between the metal holding portion 14 and the first wiring portion 131, it is preferable that X1 and X2 are sufficiently thinner than W1 and W2, for example, X1 + X2 < W1, X1 + X2 < W2.

[0022] However, the side where regions B1 and B2 are formed (the side where the holding opening 14A is formed offset) is preferably the side of the thin first wiring portion 131 as shown in FIG. 2, because it is particularly easy to make X1 and X2 small. In this case, X1 + X2 < W1 < W2.

[0023] However, even when W1 > W2 in FIG. 2 (or when the holding opening 14A is formed offset to the side of the thick second wiring portion 132 in FIG. 2), similarly, X1, X2 << W1, X1 + X2 << W2 can be achieved. That is, as long as the minimum line widths X1 and X2 in regions A1 and A2 can be set in this way, the holding opening 14A may be formed offset to either the thin side or the thick side of the first wiring portion and the second wiring portion. Alternatively, W1 = W2 may be set. This setting can be easily performed in the patterning of the substrate 10, and there is no change in other manufacturing processes. Also, regarding the mechanical strength of the fuse element 1 before melting being maintained by the metal constituting the substrate 10, it is the same as that of the fuse element 9 described above.

[0024] Also, in order to make X1 and X2 small, the holding opening 14A is preferably formed on the upper side (the side of the first wiring portion 131) in FIG. 2 as long as X1 and X2 do not become excessively small and the strength of the substrate 10 does not decrease thereby. For this reason, for example, when the planar shapes of the low-melting-point metal holding portion 14 and the holding opening 14A are circular as shown in FIG. 2, the holding opening 14A may be formed only in the region above the center of the low-melting-point metal holding portion 14.

[0025] The planar shapes of the low-melting-point metal holding portion and the holding opening can be set as appropriate, and they do not need to have the same shape. However, it is particularly preferable to make them simple circular as described above, as this allows the base to be manufactured easily and inexpensively.

[0026] In addition, although the above only describes the configuration of the low-melting-point metal holding portion and the holding opening, and the relationship between these and the wiring portion, other configurations of the base, or the configuration of the wiring portion at a location separated from the low-melting-point metal holding portion, are optional. In either case, the base can be easily and inexpensively manufactured by sheet metal processing or the like.

[0027] The present invention has been described above based on an embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components, and that such modifications are also within the scope of the present invention. [Explanation of symbols]

[0028] 1, 9 Fuse element 10, 90 base 11, 12, 91, 92 terminal section 13, 93 Wiring section 14, 94 Low melting point metal retaining part 14A, 94A holding opening 15, 95 Low melting point 131 1st wiring section (wiring section) 132 2nd wiring section (wiring section)

Claims

1. A fuse element that partially melts and cuts off a current path when a fusing current of a predetermined magnitude flows, a base body having a metal plate-like structure, the base body having a wiring portion through which the current flows and a low-melting-point metal holding portion formed locally in the middle of the wiring portion and thicker than the wiring portion; a low-melting-point body that is fixed to a holding opening that is an opening that penetrates the low-melting-point metal holding portion and is made of a low-melting-point metal that has a melting point lower than that of the metal; Equipped with In a plan view, a first wiring portion and a second wiring portion that are parts of the wiring portion are connected to the low-melting-point metal portion on one side and the other side in a current flow direction in which a current flows through the low-melting-point metal holding portion, respectively; a fuse element characterized in that the retaining opening is formed in the low-melting point metal holding portion so as to be offset in a direction along the current flow direction, so that the distance between the retaining opening and the first wiring portion is smaller than the distance between the retaining opening and the second wiring portion, thereby forming an area on one side in the low-melting point metal holding portion where the width of the current path is locally narrowed.

2. 2. The fuse element according to claim 1, wherein the low-melting-point metal holding portion and the holding opening have circular outer shapes in a plan view.

3. 3. The fuse element according to claim 1, wherein, in a plan view, the regions in the low-melting-point metal holding portion where the current density is locally high are formed at two locations along a direction perpendicular to the current flow direction, and when the minimum line widths in the regions are X1 and X2, and the widths perpendicular to the current flow direction of the first wiring portion and the second wiring portion are W1 and W2, respectively, W1 > X1 + X2 and W2 > X1 + X2.

4. 4. The fuse element according to claim 3, wherein W1<W2.

5. 3. The fuse element according to claim 2, wherein, in a plan view, the holding opening is formed only in an area on the one side of the center of the low-melting-point metal holding portion in the current-carrying direction.

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