Electrical connection box for use in a vehicle

Abstract: An electrical connection box for use in a vehicle, particularly a car, has a casing (11) and a stack of bus bars (16,17,18) and insulation plates (13,14,15) alternating in the vertical direction. For drainage of water penetrating onto the stack, each insulation plate has a drainage aperture (13a,14a,15a) and a drainage wall (13d,14d,15d) extending downwardly from its aperture so as to define and surround a drainage passage. At least each of the insulation plates other than the topmost one has on its upper surface a flow interruption rib upstanding continuously around its drainage aperture. Water on one bus bar cannot connect the bus bar conductively to another bus bar.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical connection box for use in a vehicle, especially a car and more particularly to an electrical connection box in which vertically stacked bus bars can be prevented from becoming electrically conductive to each other when water enters a casing accommodating the bus bars. The invention also relates to such a box when mounted in a vehicle, e.g. an automobile. 2. Description of the Related Art In this kind of electrical connection box, in order to prevent leakage of current between the bus bars as a result of water penetration from the upper part of the casing while a car is being cleaned, a drainage path for passing water to the lower part of the casing is formed between the periphery of a stack comprising bus bars and insulation plates and the inner side surface of the casing, to discharge water to the outside via a drainage hole formed at the lower part of the casing. In order to discharge to the outside water which has not passed via the drainage hole formed between the periphery of the stack and the inner side surface of the casing and has penetrated into the interior of the stack along the upper surface of the insulation plates, drainage constructions shown in Figs. 6 and 7 accompanying the present specification are known. Fig. 6 is disclosed in Laid-Open Japanese Utility Model Publication No. 3-48322. In this drainage construction, a drainage hole 3 is formed in the uppermost insulation plate 1A of the stack, which comprises three bus bars 2 and two insulation plates 1A, 1B. A drainage cylinder 4 projects from the periphery of the drainage hole 3 to the bottom of the stack. Water which has penetrated into the electrical connection box falls through the drainage hole 3 and the interior of the drainage cylinder 4 to be discharged to the outside via the drainage hole 5a of the lower casing 5. The preamble of claim 1 is based on this prior art. Fig. 6 shows also that the lower insulation plate 1B also has a drainage cylinder similar to the cylinder 4. In the above-described construction, the water on the upper surface of the uppermost insulation plate 1A can be discharged to the outside. However as shown in Fig. 7 (in which three insulation plates 1A, 1B, 1C and three bus bars 2A, 2B, 2c are shown), there is a more general possibility in constructions of this type that water (d) which has passed from the inner side surface of the casing to the upper surface of the insulation plates below the top plate 1A such as the second insulation plate 1B and the third insulation plate 1C, drops from the ends (i.e. the ends adjacent to the drainage cylinder 4 in Fig. 7) of the insulation plates 1B, 1C, surrounding the drainage cylinder 4 onto the insulation plates below or onto the bus bars below. For example, there is a possibility that water flows from the end of the second insulation plate 1B onto the upper surface of the third insulation plate 1C adjacent to the second insulation plate 1B and consequently, the bus bar 2B installed on the second insulation plate 1B and a bus bar 2C installed on the third insulation plate 1C are made electrically conductive to each other through the water. SUMMARY OF THE INVENTION The present invention seeks to reduce or avoid the above-described problem. It is an object of the present invention to prevent vertically stacked bus bars from becoming electrically conductive to one another when water flows along the upper surfaces of insulation plates stacked with the bus bars inside an electrical connection box. According to the present invention, there is provided an electrical connection box for use in a vehicle, comprising:- a casing, a plurality of bus bars, and a plurality of insulation plates having upper and lower surfaces, the bus bars and the insulation plates being arranged in the casing as a vertical stack in which the insulation plates alternate in the vertical direction with the bus bars. Each insulation plate in the stack has a drainage aperture and a drainage wall extending downwardly from the aperture so as to define and surround a drainage passage from the aperture. At least each of the insulation plates other than the topmost one in the stack has on its upper surface a flow interruption rib upstanding continuously around the drainage aperture thereof, the bus bar on the corresponding insulation plate being positioned further from the corresponding drainage aperture than said flow interruption rib. In one preferred embodiment of the invention the flow interruption ribs are spaced from the drainage apertures, and the drainage wall of each insulation plate contacts the upper surface of the next lower insulation plate in the stack between the flow interruption rib and the aperture of the next lower insulation plate, whereby the drainage walls and apertures together form a continuous drainage path extending to the bottom of the stack. In this construction, water which has penetrated into the casing and flows along the upper surface of each insulation plate reaches the drainage aperture, thus meeting the flow interruption rib projecting upward. Water which passes the interruption rib reaches the drainage wall, thus dropping along the inner periphery thereof. Water which has not passed the interruption rib flows to the periphery of the insulation plate, thus dropping through a drainage path formed between the inner side surface of the casing and the insulation plates. Because the drainage wall of each insulation plate is effectively continuous with the drainage wall of the next lower insulation plate, water drops reliably to the lower end of the stack. Thus, water can be prevented from dropping via the drainage apertures to the insulation plates vertically adjacent to each other. Accordingly, it is possible to prevent the bus bars from becoming electrically conductive to each other. In another preferred embodiment of the present invention, each drainage wall of each respective insulator plate extends to the bottom of the stack through the drainage aperture of each of the insulator plates below in the stack, the drainage wall of each respective insulation plate surrounding said drainage wall of each of the insulation plates above in the stack. In this construction, water which has reached the drainage aperture along the upper surface of each insulation plate can reliably fall to the lower end of the stack through the drainage cylinder which is continuous with the drainage aperture of the insulation plate and extending to the lower end of the stack. Accordingly, water flowing along the upper surface of the insulation plate can be prevented from dropping to the adjacent insulation plate through the drainage aperture. Thus, it is possible to prevent the bus bars from being electrically conductive to each other. In this construction in which the drainage walls are nested one within another, the thickness of the drainage walls may be smaller than that of other parts, e.g. the insulation plate itself, so that the space occupied by the drainage walls is not great. BRIEF DESCRIPTION OF THE DRAWINGS These and other optional features of the present invention will become clear from the following description of with the preferred embodiments thereof given with reference to the accompanying drawings throughout which like parts are designated by like reference numerals, and in which: Fig. 1 is a vertical sectional view showing part of a first electrical connection box embodying the present invention; Fig. 2 is an enlarged sectional view showing a portion of the electrical connection box of Fig. 1; Fig. 3 is a schematic perspective view showing the stack of bus bars and insulation plates of the electrical connection box of Fig. 1; Fig. 4 is a vertical sectional view showing a portion of a second electrical connection box embodying the present invention; Fig. 5 is a vertical sectional view showing a portion of a third electrical connection box embodying the invention; Fig. 6 is a vertical sectional view showing part of a prior art electrical connection box; and Fig. 7 is a view illustrating the problem of the known electrical connection box. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figs. 1 to 3 show the first embodiment of the invention. An electrical connection box 10, partly shown in Fig. 1, accommodates a stack comprising insulation plates 13, 14, 15 stacked alternately in the vertical direction with bus bars 16, 17, 18 in a casing thereof which is assembled by lockably fitting a lower casing part 11 and an upper casing part 12 to each other. The lower and upper casing parts 11, 12 are mounted within an outer casing 6 of the box 10. Details of other parts of the box not shown here are not relevant to the inventive concept, and may be embodied for example as shown in Japanese Utility Model Publication No. 3-48322 mentioned above. More specifically, the lowermost insulation plate 13 is supported by a supporting portion 11b projecting from a bottom wall 11a of the lower casing part 11, and the lowermost bus bar 16 is mounted on the upper surface of the lowermost insulation plate 13. On the upper surface of the lowermost bus bar 16, the intermediate insulation plate 14, the intermediate bus bar 17, the upper insulation plate 15 and the upper bus bar 18 are sequentially arranged. The predetermined gaps interval between the lowermost and intermediate bus bars 16, 17 and the intermediate insulation plate and upper insulation plates 14, 15 respectively are maintained by the provision of bosses 14f and 15f, respectively projecting from the lower surface of the intermediate and upper insulation plates 14, 15. In the stacked insulation plates 13, 14, 15, there are respectively formed drainage holes 13a, 14a, 15a communicating vertically with each other at two locations shown in Fig. 3. The drainage holes 13a, 14a, 15a are formed at appropriate positions at which the bus bars 16, 17, 18 are not present. The drainage holes may be formed at only one location or at two or more locations. On the insulation plates 13, 14, 15, there are formed drainage cylinders 13c, 14c, 15c projecting downwardly from each of the respective peripheries 13b, 14b, 15b of the drainage holes 13a, 14a, 15a. Further, on the upper insulation plate 15, there is formed a continuous cylindrical interruption rib 15d projecting upwardly from the drainage hole periphery 15b at a small radial spacing from the hole 15a. Likewise on the intermediate and lowermost insulation plates 14, 13, there are formed continuous cylindrical interruption ribs 14d, 13d projecting upwardly from the drainage hole peripheries 14b, 13b and spaced by a predetermined amount from the drainage hole peripheries 14b, 13b. The drainage cylinder 15c projecting from the upper insulation plate 15 is fitted against the inner peripheral surface of the interruption rib 14d of the intermediate insulation plate 14. The lower surface of the drainage cylinder 15c contacts the upper surface 14e of the intermediate insulation plate 14 between the drainage hole 15a and the interruption rib 14d so as to connect the drainage cylinders 15c, 14c with each other vertically. Similarly, the drainage cylinder 14c projecting downwardly from the intermediate insulation plate 14 is fitted against the inner peripheral surface of the interruption rib 13d of the lowermost insulation plate 13, and similarly the lower surface of the drainage cylinder 14c contacts the upper surface 13e of the lowermost insulation plate 13 between the interruption rib 13d and the drainage hole 13a so as to connect the drainage cylinders 14c, 13c with each other vertically. The drainage cylinder 13c of the lowermost insulation plate 13 projects downwardly a certain distance. The upper, intermediate and lower drainage cylinders 15c, 14c, 13c have the same inner diameter and are vertically continuous with each other so as to constitute a single cylindrical drainage path. The height of the interruption ribs 13d, 14d, 15d is greater than the thickness of the respective bus bars 16, 17, 18 mounted on the lowermost, intermediate and upper insulation plates 13, 14, 15 respectively. The height of the intermediate interruption rib 14d and of the lowermost interruption rib 13d may be such that they contact the lower surface of the next adjacent insulation plate 15 and insulation plate 14, respectively. Protection walls 13g, 14g, 15g project upwardly from the periphery of each of the stacked insulation plates 13, 14, 15 respectively. The protection wall 13g contacts the lower surface of the intermediate insulation plate 14, and the protection wall 14g contacts the lower surface of the upper insulation plate 15 so that the protection walls 13g, 14g, 15g are continuous with each other vertically to prevent the penetration of water into the stack from the peripheries of the insulation plates 13, 14, 15. A drainage gap 19 is formed between the protection walls 13g, 14g, 15g and the inner surface of a side wall 11c of the lower casing part 11. A drainage hole 11d is formed in the bottom wall 11a of the lower casing part 11 below the drainage gap 19. In the electrical connection box 10 having this construction, when water has penetrated into the casing comprising the lower casing part 11 and the upper casing part 12, it is discharged to the drainage hole 11d via the drainage gap 19 formed between the side wall 11c of the lower casing part 11 and the stack of insulation plates 13, 14, 15 and bus bars 16, 17, 18. Any water flowing along the upper surfaces of any of the insulation plates 13, 14, 15 after passing the protection walls 13g, 14g, 15g, reaches the drainage holes 13a, 14a, 15a. Thus water meeting and passing the interruption ribs 13d, 14d, 15d reaches the peripheries 13b, 14b, 15b of drainage holes 13a, 14a, 15a, and drops downward along the inner surface of the drainage cylinders 13c, 14c, 15c. Water which does not pass the interruption ribs 13d, 14d, 15d is discharged downward via the gap 19 at the periphery of the stack or vaporizes. The cooperation of the drainage cylinder 13c, 14c with the respective ribs 14d, 15d helps to ensure that no accumulation of water can occur which might provide a conduction path between two bus bars. Particularly the water leak path from the drainage path through the cylinders 13c, 14c, 15c onto any of the bus bars is tortuous. Thus, essentially no possibility arises that water collects in such a way as to cause the vertically stacked bus bars to become electrically conductive to each other. Even though water which enters the upper drainage cylinder 15c flows along the inner surface thereof, it continues downward along the inner surface of the drainage cylinder 14c, because the inner surface of the lower end of the upper drainage cylinder 15c is continuous with the inner surface of the upper end of the intermediate drainage cylinder 14c. Then, the water flows downward along the inner surface of the lower drainage cylinder 13a, thus reliably flowing downwardly to the lower end of the stack through the drainage cylinders 13c, 14c, 15c. Consequently, the water flowing along the upper surface of the upper insulation plate 15 drops through the stack via the drainage holes. Thus, the bus bars 16, 17, 18 can be reliably prevented from being made electrically conductive to each other by the penetration of water into the casing. Fig. 4 shows a second embodiment which is otherwise similar to that of Figs. 1 to 3 but in which drainage cylinders 13c', 14c', 15c' project downwardly from the periphery of each of the drainage holes 13a', 14a', 15a' in the insulation plates 13', 14', 15', each extending to the lower side of the stack of insulation plates and bus bars. The drainage cylinders 13c', 14c', 15c' are thus overlapping and concentric with each other. Similarly to the first embodiment, interruption ribs 13d', 14d', 15d' are formed on the upper surfaces of each of the insulation plates 13c', 14c', 15c', in this case at the peripheries of the respective drainage holes 13a', 14a', 15a'. Thus, in this second embodiment, the periphery of the drainage cylinder 15c' projecting down from the upper insulation plate 15' is located within the drainage cylinder 14c' projecting down from the intermediate insulation plate 14' with a drainage gap 20 provided between them, and the periphery of the drainage cylinder 14c' is within the drainage cylinder 13c' projecting down from the lowermost insulation plate 13' with a drainage gap 21 provided between them. Water which has penetrated into the casing and flows along the upper surface of the upper insulation plate 15' drops through the drainage cylinder 15c'; water flowing along the upper surface of the intermediate insulation plate 14' drops through the gap 20 formed between the drainage cylinders 15c', 14c'; and water flowing along the upper surface of the lower insulation plate 13' drops through the gap 21 formed between the drainage cylinders 14c', 13c'. Thus, in the second embodiment as well, water on any one of the insulation plates is prevented from dropping to a lower insulation plate. The vertically stacked bus bars can be reliably prevented from becoming electrically conductive to each other due to water. Fig. 5 shows a third embodiment, which differs from the second embodiment in that the thickness of the drainage cylinders 13c', 14c', 15c' projecting downwardly from each of the lower intermediate and upper insulation plates 13', 14', 15' is smaller than that of the plates themselves so that the space occupied by the drainage cylinders fitted one within another can be reduced. The upper insulation plate 15' has no protection rib at the periphery of its drainage hole. As is apparent from the foregoing description, in the electrical connection box according to the present invention, water flowing along the upper surface of each of the vertically stacked insulation plates enters the drainage holes and falls to below the stack. Thus, water can be prevented from dropping to a lower insulation plate or plates via the drainage holes. Thus, the bus bars installed on the insulation plates can be prevented from becoming electrically conductive to each other. Further, in the first embodiment, because each drainage cylinder is fitted into the inner peripheral surface of the interruption rib of a lower plate, the insulation plates can be held at predetermined positions and hence prevented from being moved relatively by shocks. Similarly to the first embodiment, in the second embodiment, because the drainage cylinders are fitted one within another, the insulation plates can be held at predetermined positions and prevented from being relatively displaced by shocks. Further, the construction of the electrical connection box is very simple in that the drainage hole is formed on each insulation plate, and the drainage cylinder, interruption rib and peripheral rib project from the peripheral parts of the drainage hole. Thus, the present invention can be easily embodied at a low cost.

Claims: An electrical connection box for use in a vehicle, comprising a casing (11), and a plurality of bus bars (16,17,18), and a plurality of insulation plates (13,14,15; 13',14',15') arranged in said casing as a vertical stack in which the insulation plates alternate in the vertical direction with the bus bars, wherein each said insulation plate in said stack has a drainage aperture (13a,14a,15a; 13a',14a',15a') and a drainage wall (13c,14c,15c; 13c',14c'15c') extending downwardly from said aperture thereof so as to define and surround a drainage passage from said aperture, characterised in that at least each of said insulation plates other than the topmost one in said stack has on its upper surface a flow interruption rib (13d,14d,15d; 13d',14d',15d') upstanding continuously around said drainage aperture thereof, the bus bar on the corresponding insulation plate being positioned further from the corresponding drainage aperture than said flow interruption rib. An electrical connection box according to claim 1, wherein said flow interruption ribs (13d,14d,15d) are spaced from said drainage apertures (13a,14a,15a), and said drainage wall (13c,14c,15c) of each said insulation plate contacts the upper surface of the next lower insulation plate in said stack between said flow interruption rib and said aperture of said next lower insulation plate, whereby said drainage walls and apertures together form a continuous drainage path extending to the bottom of the stack. An electrical connection box according to claim 2, wherein the topmost insulation plate (15) in said stack also has on its upper surface a flow interruption rib (15d) upstanding around said drainage aperture (15a) thereof. An electrical connection box according to claim 1, wherein each said drainage wall (13c',14c',15c') of each respective insulator plate extends to the bottom of said stack through the drainage aperture of each of the insulator plates below in the stack, said drainage wall of each respective insulation plate surrounding said drainage wall of each of the insulation plates above in the stack. An electrical connection box according to any one of claims 1 to 4, wherein each said drainage wall and each said flow interruption rib is cylindrical in shape. A vehicle having mounted in it an electrical connection box according to any one of claims 1 to 5.

Inventors: HAYAKAWA TATSUYA, HAYAKAWA, TATSUYA
Applicants: SUMITOMO WIRING SYSTEMS, SUMITOMO WIRING SYSTEMS, LTD.
Application year: 1997
Main classification: H01R13
IPC codes: H02G3, H01R13, H01R9