Fuse unit

Abstract

To obtain a fuse unit in which a current path of a fusible element housed in a housing space of the body can secure a sufficient length to achieve high resistance even when there are restrictions on the volume of the housing space, the thinness of the current path, and its spacing.SOLUTION: A fuse unit 1 includes a bus bar 10 and a resin body 20 that partially covers the bus bar 10, in which a fusible element 12 (low-rated fusible element 12a) formed on the bus bar 10 is accommodated in an accommodation space 21 formed in the body 20, and the current path of the fusible element 12 (low-rated fusible element 12a) is accommodated three-dimensionally in the accommodation space.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuse unit having a fusible element that melts when an overcurrent occurs. [Background technology]

[0002] A fuse unit applied to a vehicle or the like electrically connects a battery and a load, and has the function of cutting off the electrical connection between the battery and the load when an overcurrent exceeding the rated current flows, for example. The fuse unit includes a bus bar on which a fusible element that functions as a fuse that melts when an overcurrent occurs is formed (see, for example, Patent Documents 1 and 2). The fuse unit includes a resin body that partially covers the bus bar. The bus bar is made by pressing a metal plate and is integrated with the body by insert molding using a resin material. The body includes an accommodation space that accommodates the fusible element. The accommodation space is generally closed by a transparent cover, which allows the state of the fusible element to be visually confirmed and prevents the scattering of debris that occurs when the fusible element melts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-331591 [Patent Document 2] Japanese Patent Publication No. 2020-47415 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] Because the body is formed using a mold, its shape cannot be easily changed. Therefore, there is a limit to the size of the accommodation space, and a low-rated fusible element that melts with a small current may not be able to be accommodated in the accommodation space. In other words, if the volume of the accommodation space is limited, the desired length of the low-rated fusible element cannot be ensured. That is, a high-rated fusible element that melts with a large current has a shape that is thick and short in the direction of current flow, with low resistance. In contrast, a low-rated fusible element needs to be thin and long in the direction of current flow, with high resistance. However, because it is produced by pressing, there are limits to the thinness and spacing, and it cannot be accommodated in the accommodation space, which has a size limit.

[0005] 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]

[0006] The present invention provides a fuse unit comprising a bus bar and a resin body partially covering the bus bar, wherein a fusible element formed on the bus bar is accommodated in an accommodating space formed in the body, and the current path of the fusible element is accommodated three-dimensionally in the accommodating space. The accommodating space may have an open surface, and the current path may be bent toward the open side. The fusible element may include a placement portion for a low-melting-point metal chip, and the current path may be bent in a direction in which the low-melting-point metal chip is placed in the placement portion. [Effects of the Invention]

[0007] Since the present invention is configured as described above, the current path of the fusible element accommodated in the accommodation space of the body can be ensured to be of sufficient length to achieve high resistance, even if there are restrictions on the volume of the accommodation space, the thinness of the current path, and its spacing. [Brief explanation of the drawings]

[0008] [Figure 1]FIG. 2 is an exploded perspective view of the fuse unit according to the embodiment. [Figure 2] 2A and 2B are a perspective view and an enlarged view of the bus bar shown in FIG. [Figure 3] 2A and 2B are a perspective view and an enlarged view of the body shown in FIG. [Figure 4] 2A and 2B are a plan view and a cross-sectional view shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, components having similar functions will be given the same reference numerals and descriptions thereof will be omitted as appropriate.

[0010] Referring to FIG. 1, the fuse unit 1 of this embodiment includes a plurality of branch circuits connected to a plurality of loads, and each branch circuit is provided with a fusible element 12 that functions as a fuse for protecting the circuit.

[0011] The fuse unit 1 includes a bus bar 10, which is a circuit component, and a resin body 20 that partially covers the bus bar 10. The bus bar 10 is integrated with the body 20 by insert molding the body 20 using a resin material.

[0012] The busbar 10 comprises a power supply side terminal board 11 connected to a battery or the like, and a plurality of load side terminal boards 13 connected to the power supply side terminal board 11 via fusible elements 12 (low-rated fusible elements 12a, high-rated fusible elements 12b). The fusible elements 12 are parts that have a small cross-sectional area through which current passes, making them more likely to melt due to Joule heat. The low-rated fusible elements 12a are thin and long in the direction of current flow, have a high resistance, and melt with a small current. The high-rated fusible elements 12b are thick and short in the direction of current flow, have a low resistance, and melt with a large current.

[0013] The body 20 is formed so as to expose at least a portion of the power supply side terminal board 11 and the load side terminal board 13. The body 20 also has accommodating spaces 21 for accommodating the fusible elements 12, respectively.

[0014] The accommodation space 21 is cylindrical with an open surface that serves as a window, and accommodates the fusible element 12 in a floating state. The open surface of the accommodation space 21 is closed by a transparent cover 30, which makes it possible to visually check the state of the fusible element 12 and prevents the scattering of debris that is generated when the fusible element 12 melts.

[0015] 2(a) is a perspective view of a busbar 10 produced by pressing a metal plate arranged on the XY plane, in which a portion of a power supply side terminal board 11 is bent in the Z direction perpendicular to the XY plane by bending. In FIG. 2(b), (a) is an enlarged view of region A shown in (a).

[0016] Fig. 3(a) is a perspective view of the fuse unit 1 in which the busbar 10 and the body 20 are integrated, showing a state in which the fusible element 12 is accommodated in the accommodation space portion 21. In Fig. 3(b), (b) is an enlarged view of region B shown in (a).

[0017] Fig. 4(a) is a perspective view of the fuse unit 1 in which the bus bar 10 and the body 20 are integrated together. In Fig. 4(b), Fig. 4(a) is a cross-sectional view taken along CC line shown in Fig. 4(a).

[0018] 2 to 4, the low-rated fusible element 12a includes a current path 121 and an arrangement portion 122 for an arrangement portion 122 of a low-melting-point metal tip 40 made of a tin alloy or the like. The low-melting-point metal tip 40 is attached to the arrangement portion 122 by crimping or welding. The low-melting-point metal tip 40 melts when a current equal to or greater than a predetermined current flows through the current path 121, and forms a eutectic with the arrangement portion 122 to form an alloy layer with a high resistance value, which promotes heat generation by electrical current application.

[0019] The current path 121 of the low-rated fusible element 12a is set to be thin and long in the direction of current flow. The current path 121 has limitations on its thinness and spacing due to press processing, so it is necessary to ensure its length. Therefore, the current path 121 is made in a meandering shape on the XY plane, and it is not possible to make contact with the side wall of the accommodation space 21 in the X direction or to ensure sufficient clearance.

[0020] Therefore, the current path 121 of the low-rated fusible element 12a is accommodated in the accommodation space 21 with fusible element bent parts 121a formed by bending at both ends in the X direction toward the side in the Z direction where the low-melting point metal chip 40 is attached by bending processing. In other words, the fusible element bent parts 121a are formed at positions that deviate from the XY plane, and the current path 121 of the low-rated fusible element 12a is accommodated in the accommodation space 21 three-dimensionally.

[0021] In this way, the current path 121 is accommodated three-dimensionally in the accommodation space 21, so that a sufficient length can be ensured to achieve high resistance of the low-rated fusible element 12a even if there are restrictions on the volume of the accommodation space 21 and the thinness and spacing of the current path 121. The fusible element bend 121a may be formed only at one end in the X direction of the current path 121 of the low-rated fusible element 12a.

[0022] The current path 121 has a width X1 in the X direction immediately after press working, which is narrowed to a width X2 in the X direction after the fusible element bent portion 121a is formed. As a result, the width X2 in the X direction of the current path 121 becomes sufficiently shorter than the width X3 in the X direction of the accommodation space 21, and a sufficient clearance X4 is ensured between the current path 121 and the side wall of the accommodation space 21. The sufficient clearance X4 is the space where a molding die for forming the body (accommodation space 21) can be inserted, and if a sufficient clearance X4 cannot be ensured, the body 20 cannot be insert-molded.

[0023] The fusible element bending portion 121a is formed on one open side of the storage space portion 21. Since the forming mold for forming the body 20 (storage space portion 21) is not placed on the open side of the storage space portion 21, the forming conditions for the fusible element bending portion 121a are relatively flexible. If the fusible element bending portion 121a interferes with the cover 30, this can be addressed by simply changing the design of the cover 30.

[0024] In this embodiment, the fusible element bending portion 121a is formed by bending the current path 121 at a substantially right angle in the Z direction, but there is no limit to the number of times it is bent or the bending angle, and these can be set appropriately according to the required length of the current path 121. In addition, the current path 121 of the low-rated fusible element 12a may be accommodated three-dimensionally in the accommodation space portion 21 by bending it in the Z direction.

[0025] As described above, this embodiment is a fuse unit 1 comprising a busbar 10 and a resin body 20 partially covering the busbar 10, in which the fusible element 12 (low-rated fusible element 12a) formed on the busbar 10 is accommodated in an accommodating space portion 21 formed in the body 20, and the current path 121 of the fusible element 12 (low-rated fusible element 12a) is accommodated three-dimensionally in the accommodating space portion 21. With this configuration, the low-rated fusible element 12a can be ensured to have a sufficient length to achieve high resistance even if there are restrictions on the volume of the accommodation space 21 and the thinness and spacing of the current path 121. The width X2 of the current path 121 in the X direction can be made sufficiently shorter than the width X3 of the accommodation space 21 in the X direction. Therefore, a sufficient clearance X4 is ensured between the current path 121 and the side wall of the accommodation space 21 so that a molding die for molding the body (accommodation space 21) can be inserted, making it possible to insert the body 20.

[0026] Furthermore, according to this embodiment, the accommodation space 21 has an open surface, and the current path 121 is bent toward the open surface of the accommodation space 21 . With this configuration, the current path 121 is accommodated three-dimensionally in a direction with a relatively large margin in the accommodation space 21. That is, since the forming mold for shaping the body 20 (accommodation space 21) is not placed on the open surface side of the accommodation space 21, there is a margin in the forming conditions for the fusible element bending portion 121a. If the fusible element bending portion 121a interferes with the cover 30, this can be addressed by simply changing the design of the cover 30.

[0027] Furthermore, according to this embodiment, the fusible element 12 (low-rated fusible element 12a) has an arrangement portion 122 for the low-melting point metal chip 40, and the current path 121 is bent in the direction in which the low-melting point metal chip 40 is arranged in the arrangement portion 122. With this configuration, the current path 121 is accommodated three-dimensionally in a direction with a relatively large margin in the accommodation space portion 21. That is, since a clearance for arranging the low-melting point metal tip 40 is ensured in the arrangement direction of the low-melting point metal tip 40, there is a margin in the conditions for forming the fusible element bending portion 121a.

[0028] 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]

[0029] 1 fuse unit 10 Busbar 11 Power supply side terminal board 12 Soluble 12a low rating fusible 12b High rating fusible 13 Load side terminal board 20 Body 21 Storage space 30 Cover 40 Low melting point metal chip 121 Current path 121a Fusible element bending part 122 Placement section

Claims

1. A fuse unit comprising: a bus bar; and a resin body partially covering the bus bar, wherein a fusible element formed on the bus bar is accommodated in an accommodating space formed in the body, A fuse unit, characterized in that the current path of the fusible element is accommodated three-dimensionally in the accommodation space.

2. The storage space has an open surface, 2. The fuse unit according to claim 1, wherein the current path is bent toward the open side.

3. the fusible element has a low melting point metal chip arrangement portion, 2. The fuse unit according to claim 1, wherein the current path is bent in a direction in which the low-melting-point metal chip is disposed in the disposing portion.

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