GB2329753A

GB2329753A - Busbar for electrical junction box

Info

Publication number: GB2329753A
Application number: GB9820961A
Authority: GB
Inventors: Tomohiro Sugiura
Original assignee: Yazaki Corp
Current assignee: Yazaki Corp
Priority date: 1997-09-26
Filing date: 1998-09-25
Publication date: 1999-03-31
Anticipated expiration: 2018-09-25
Also published as: JP3308874B2; DE19843855A1; JPH1198649A; DE19843855C2; GB2329753B; GB9820961D0

Abstract

A bus bar (16) for an electrical junction box comprises a first terminal provided an upper edge of the bus bar for serving as a connector terminal of the electrical junction box. A second terminal is provided an lower edge of the bus bar for being fixed and connected to a wiring board of the electrical junction box. A recessed portion (20) is formed in the lower edge of the bus bar so as to avoid an interference with an electrical device on the wiring board, and a projected portion (22) is formed in the upper edge of the bus bar above the recessed portion. The vertical cross-section of the bus bar where the projected portion and the recessed portion are formed is substantially equal to that of where any other portion of the bus bar. Preferably the projected portion (22) and causally formed projections (20a) on the lower edge act as the terminals.

Description

BUS BAR STRUCTURE OF ELECTRICAL JUNCTION BOX The present invention relates to an improved bus bar structure used for connecting together a wiring board and a main cover of an electrical junction box mounted on an automobile or the like.

The present invention is based on Japanese Patent Application No. Hei 9-261963 which is incorporated herein by reference.

Many electric parts have heretofore been used in an electric equipment and an automobile having complicated electric elements, and there has been commonly used an electrical junction box by which electric circuits for transmitting and receiving information, signals and electric power between these electric parts are mutually connected in a concentrated manner. In this electrical junction box, a wiring board is received in a casing, and this wiring board and a main cover are connected together by bus bars. Generally, there has been used a construction in which end portions of the bus bars are exposed to the surface of the main cover, and are used as connector terminals. Therefore, these bus bars are fixed by fitting to the wiring board.

Figs. 4 and 5 show the conventional construction of mounting of vertical bus bars 1 on a wiring board 2. In these Figures, the two bus bars 1 are bent at a plurality of portions thereof in a direction of the thickness thereof in accordance with their respective wiring patterns. Shallow grooves 3, corresponding respectively to the patterns of bending of the two bus bars, are formed in the surface of the wiring board 2, and reception grooves 4 of a generally U-shaped cross-section are formed respectively at predetermined portions of the shallow groove 3. The reception grooves 4 are formed respectively at such positions that they will not interfere with parts, mounted on an under cover (not shown) provided below of the wiring board 2, or a lower wiring board.

A plurality of projections la, each corresponding in shape to the associated reception groove 4, are formed on a lower edge of each bus bar 1, and the projections la of each bus bar 1 are inserted respectively into the associated reception grooves 4, thereby stably fixing the bus bar 1 to the wiring board 2 by fitting. In Fig. 4, terminal portions ib are formed on an upper edge of each bus bar 1.

In the above bus bar structure, as shown in Figs. 5(a) and 5(b), with respect to a height dimension of each bus bar 1, the height a of those portions thereof each having the projection la is larger than the height b of non-projected portions thereof having no such projection. And besides, when it is inevitable that the bus bar 1 will intersect the part projecting from the under cover, the lower edge of the non-projected portion is often notched or recessed so that the bus bar and this part will not interfere with each other, and thus the height dimension must be reduced.

When the electricity is turn on, the amount of heat generated upon in a bus bar having a constant thickness is inversely proportional to a height dimension of the bus bar through which the electric current flows, and therefore particularly when a large current flows through the bus bar 1, resistance heat develops at those portions of a small height dimension. Therefore, when those portions of a small height dimension generate heat, the internal temperature rises, which causes a problem that those parts, liable to be affected by high temperature, fail to properly function or fail to perform the intended function, and in some cases, there has been encountered a problem that the cover or the wiring board is subjected to damage due to fusion.

An object of the present invention is to overcome the above problems, and more specifically to provide a bus bar structure of an electrical junction box in which even if a recess is formed in a bus bar in order to prevent the interference of the bus bar with an under cover or a lower wiring board, that portion of the bus bar, having the recess, can have a predetermined vertical cross-sectional area.

In order to achieve the above object, there is provided a bus bar for an electrical junction box comprising: a first terminal provided an upper edge of the bus bar for serving as a connector terminal of the electrical junction box; a second terminal provided an lower edge of the bus bar for being fixed and connected to a wiring board of the electrical junction box; a recessed portion formed in the lower edge of the bus bar so as to avoid an interference with an electrical device on the wiring board; and a projected portion formed in the upper edge of the bus bar above the recessed portion, wherein a vertical cross section of the bus bar where the projected portion and the recessed portion are formed is substantially equal to that of where any other portion of the bus bar.

In the bus bar, a height dimension of the projected portion is equal to that of the recessed portion, and distance dimensions between the both upper corners of the recessed portion and corresponding opposed both lower corners of the projected portion are respectively equal to or larger than the height dimension of the any other portion of the bus bar. The height dimension of the any other portion is set such that resistance heat to be generated therein can be kept to a temperature lower than an allowable temperature.

Therefore, the bus bar does not have any portion, having a temperature more than the allowable temperature. Accordingly, it is prevented the temperature within the electrical junction box unduly rises and thereby parts sensitive to heat are damaged.

In the accompanying drawings: Fig. 1 is an exploded perspective view showing a bus bar structure of an electrical junction box of the present invention; Fig. 2 is a plan view showing an essential portion of the bus bar structure of Fig. 1; Fig. 3 is a perspective view showing a mounting structure of a wiring board on which the bus bar of Fig. 1 is mounted; Fig. 4 is a perspective view showing the conventional mounting structure of vertical bus bars and a wiring board; Fig. 5(a) is a fragmentary, cross-sectional view taken along the line A-A of Fig. 4; and Fig. 5(b) is a fragmentary, cross-sectional view taken along the line B-B of Fig. 4.

A preferred embodiment of a bus bar structure of an electrical junction box of the present invention will now be described in detail with reference to Figs. 1 to 3. Fig. 1 is an exploded, perspective view of the electrical junction box having the bus bar structure of the present invention, Fig. 2 is a plan view showing an essential portion of a bus bar of Fig. 1, and Fig. 3 is a perspective view showing a mounting structure of a wiring board on which the bus bar of Fig. 1 is mounted.

As shown in Fig. 1, the electrical junction box of this embodiment comprises an under cover 10 whose interior is partitioned into a plurality of chambers in which electric connection parts are received, respectively, a main cover 14 which is fitted on an upper portion of the under cover 10, and includes many connector portions projecting from an upper face thereof, and the wiring board 12 received within the main cover 14. A pair of vertical bus bars 16 are mounted on the wiring board 12 to connect the wiring board 12 and the main cover 14 together, and a lower edge of each bus bar 16 is fitted into the wiring board 12, and is fixed thereto.

Each of the vertical bus bars 16 is formed by bending a metal sheet of a good electrical conductivity at a plurality of portions thereof in accordance with wiring configuration of the electrical junction box, and connector terminals 18 inserted respectively into the associated connector portions of the main cover 14 are formed on an upper edge of the bus bar. A plurality of projections, which are inserted respectively into reception grooves formed in the wiring board 12, are formed on the lower edge of the bus bar 16, and also a plurality of recesses are formed in the lower edge of the bus bar 16 in order to prevent the interference of the bus bar with various parts projecting from the upper face of the wiring board 12. Projections are formed respectively on those portions of the upper edge of the bus bar corresponding respectively to those portions of the lower edge thereof in which the recesses are formed, respectively, and therefore a height dimension L of the bus bar is generally constant regardless of the recess-projection arrangement of the lower edge of the bus bar.

As shown in Fig. 2, the reference height dimension L of the bus bar 16 is determined by a value of an electric current flowing through the bus bar. Therefore, in the process of the design, when it becomes necessary to form the recess 20, having a height A and a width B, in the lower edge of the bus bar 16, the projection 22, having the same height A, is formed on that portion of the upper edge of the bus bar 16 corresponding to this recess 20. However, if only the height is increased, the width of corner portions designated by a reference character C becomes small.

Therefore, it is necessary that the length of the corner portions denoted by C is equal to or larger than the reference height dimension L. For example, if the height A is equal to the reference height dimension L, the length dimension D of the projection 22 is set to not less than (B + 2 cos 0).

As shown in Fig. 3, the projections 20a are causally formed respectively in both sides of each recess 20 in the lower edge of the bus bar 16. Therefore, if insertion grooves 24 are formed in the surface of the wiring board 12 at a pitch corresponding to the pitch of the recesses 20, the bus bar 16 can be stably fixed to the wiring board without the need for providing the reception grooves 4 (see Fig. 4). In this case, the shrinkage or the like, resulting from the formation of the reception grooves in the wiring board 12, can be positively prevented.

As has been described heretofore, in the bus bar structure of the electrical junction box according to the present invention, the recesses are formed in the lower edge of the vertical bus bar in order to prevent the interference of the bus bar with parts projecting from the upper face of the wiring board, and the projection is formed on that portion of the upper edge of the bus bar, disposed just above each of the recesses, and the projection has the height and length which correspond to the configuration of the recess, so that the vertical bus bar has a substantially uniform vertical cross-sectional area throughout its length.

The projection is equal in height to the recess, and the distance between the both upper corners of the recess and corresponding opposed both lower corners of the projection is respectively equal to or larger than the reference height dimension of the vertical bus bar.

Therefore, the vertical bus bar does not have any portion whose height dimension is smaller than the reference height dimension, and resistance heat, having a temperature more than an allowable temperature, is positively prevented from being generated.

Therefore, the temperature within the electrical junction box, will not unduly rise, thus preventing those parts, sensitive to heat, from being damaged, and therefore the bus bar of a high reliability can be obtained.

It is contemplated that numerous modifications may be made to the apparatus of the present invention without departing from the spirit and scope of the present invention defined in the following claims.

Claims

CLAIMS 1. A bus bar for an electrical junction box comprising: a first terminal provided an upper edge of the bus bar for serving as a connector terminal of the electrical junction box; a second terminal provided an lower edge of the bus bar for being fixed and connected to a wiring board of the electrical junction box; a recessed portion formed in the lower edge of the bus bar so as to avoid an interference with an electrical device on the wiring board; and a projected portion formed in the upper edge of the bus bar above the recessed portion, wherein a vertical cross-section of the bus bar where the projected portion and the recessed portion are formed is substantially equal to that of where any other portion of the bus bar.
2. The bus bar for the electrical junction box as set forth in claim 1, wherein a height dimension of the projected portion is equal to that of the recessed portion, and distance dimensions between the both upper corners of the recessed portion and corresponding opposed both lower corners of the projected portion are respectively equal to the height dimension of the any other portion of the bus bar.
3. The bus bar for the electrical junction box as set forth in claim 1, wherein a height dimension of the projected portion is equal to that of the recessed portion, and distance dimensions between the both upper corners of the recessed portion and corresponding opposed both lower corners of the projected portion are respectively larger than the height dimension of the any other portion of the bus bar.
4. The bus bar for the electrical junction box as set forth in claim 2, wherein the height dimension of the any other portion is set such that resistance heat to be generated therein can be kept to a temperature lower than an allowable temperature.
5. The bus bar for the electrical junction box as set forth in claim 3, wherein the height dimension of the any other portion is set such that resistance heat to be generated therein can be kept to a temperature lower than an allowable temperature.
6. The bus bar for the electrical junction box as set forth in claim 1, wherein a projected portion which is causally formed in the lower edge of the bus bar in accordance with forming of the recessed portion serves as the second terminal.
7. A bus bar substantially as described with reference to the accompanying drawings.