Patent Publication Number: US-7907401-B2

Title: Housing for an electronic unit

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to an improved housing for an electronic unit, the housing including a space for receiving a printed circuit board, one or more feet, and a venting device. The present invention also relates to a method for manufacturing a vehicle incorporating the electronic unit housing. 
     BACKGROUND OF THE INVENTION 
     Housings for vehicle electronic units receive electronic components disposed on printed circuit boards. The printed circuit boards must be protected from dust and moisture. 
     Vehicle electronic unit housings are regularly exposed to large temperature fluctuations. During a rise in temperature, air in the receiving spaces of the housings expand and must be discharged to the outside in order to prevent mechanical stresses that could cause the housings to rupture. Conventionally, venting devices are used that place the receiving spaces in communication with atmosphere surrounding the housings. 
     For aesthetic reasons, electronic unit housings are frequently painted over, together with the components on which they are disposed. With conventional electronic unit housings, it is possible for atomized paint to settle in and clog the venting devices. In addition, electronic unit housings are regularly cleaned together with their associated vehicles by means of steam jets. With conventional electronic unit housings, this can result in moisture penetrating the receiving spaces and causing damage (e.g., to membranes therein). 
     SUMMARY OF THE INVENTION 
     Generally speaking, in accordance with embodiments of the present invention, an improved housing for an electronic unit is provided which overcomes disadvantages associated with conventional electronic unit housings. In accordance with embodiments of the present invention, the housing includes (i) a space for receiving a printed circuit board, (ii) at least one foot constructed and arranged to fasten the housing onto a base, and (iii) a venting device which opens on the side of the housing facing the base. By this construction, the venting device is well protected from atomized paint or steam. 
     According to an embodiment of the present invention, the venting device opens into the foot. 
     Within the scope of the present description, the foot refers in particular to that region of the electronic unit housing which is disposed to the side of a projection of the receiving space onto the base. The electronic unit housing may have two feet, which are disposed on the two sides of the receiving space. The foot can be constructed as a strap and comprise a mounting device, such as, for example, a fastening eye, by which the electronic unit housing can be fastened onto a component, such as, for example, a vehicle component. 
     The electronic unit housing lies flat, with its underside on the base. Thus, it would be expected that the position at which the venting device opens on the underside is irrelevant. However, the arrangement of the foot offers clear advantages compared with an arrangement at other positions of the underside of the electronic unit housing. Since the foot is fastened to the vehicle component, it is there that the contact pressure is high and the sealing action is particularly effective. 
     An advantage of the configuration according to embodiments of the invention is that it can be easily manufactured and is very robust against aerosols, such as are emitted, for example, by a jet or a can during painting. 
     According to an embodiment of the present invention, the venting device has an internal opening to the receiving space and an external opening, in communication with the internal opening via a venting duct, for venting the receiving space, wherein at least one of the openings (external and internal), is covered with a membrane of stretched plastic or other suitable material (e.g., GORE-TEX). This membrane has micropores that are large enough to allow air to pass while blocking water or paint particles. 
     An advantage of this construction is that the venting device is protected reliably against penetrating particles by simple means. It is preferable to provide the membrane where the venting device opens into the foot. In this case, contamination of the membrane is largely ruled out, since even the finest particles are deposited at other positions of the electronic unit housing before they can reach the external opening on their path through the foot. 
     In another embodiment of the present invention, the external opening and the membrane are covered with a cap, wherein the cap has a recess that embraces the membrane and wherein the recess is positioned relative to (directed away from) the base such that a labyrinth effect is achieved. That is, air flowing from atmosphere surrounding the electronic unit housing into the receiving space must first travel substantially parallel to the underside to reach the external opening, after which it must change direction and flow away from the underside, then again change direction and flow back toward the underside, before changing direction one more time and entering the venting duct. In this way, aerosol particles will likely be deposited on the cap, for example, or on another component of the electronic unit housing, thus preventing them from reaching and contaminating the membrane. 
     It is also possible to provide, in the foot, ribs angled toward one another in a straddled configuration and arranged so as to drain off stagnant water. 
     Preferably, the venting duct broadens in diameter from the internal opening to the external opening. It is not necessary that the venting duct have a circular cross section for this purpose. For example, it is possible for the venting duct to be a slot. In this case, the feature that the venting duct broadens in diameter from the internal opening to the external opening will be understood to mean that a maximum cross section of the venting duct increases in diameter. Stagnant moisture in the venting duct can be prevented in this way. 
     According to another embodiment of the present invention, the foot is constructed such that a rim of the foot rests flat on the flat base, with the rim surrounding the external opening. The rim will be understood to be that part of the foot which is in contact with the respective base when the electronic unit housing is mounted. This rim blocks the penetration of aerosol laden air into the foot. 
     Because the rim surrounds the external opening, the air must first flow past the electronic unit housing in the region of the receiving space before it can reach the external opening. Aerosol particles can be deposited along this path, thus protecting the membrane from contamination. 
     By the feature that the rim surrounds the external opening it is to be understood that, when the electronic unit housing is mounted on the base, no direct linear path exists from anywhere in the atmosphere surrounding the foot through the rim to the external opening. For this purpose, it is not necessary that the rim completely surround the external opening. For example, it is sufficient that, as viewed from the external opening, the rim surround three quarters of a circumferential angle of the external opening. 
     According to another embodiment of the present invention, the foot has a fastening eye, the eye diameter of which is such that the external opening is disposed at a distance of less than four times the eye diameter from the fastening eye. The distance in this case is to be understood to be the distance between the respective centers of the fastening eye on the one hand and of the external opening on the other hand. Because the foot is screwed onto the fastening eye, a particularly large force is present there to press the electronic unit housing against the base. In the vicinity of the fastening eye, the rim is thereby pressed particularly firmly onto the base, and, so, it is particularly difficult for aerosol laden air to penetrate toward the external opening. 
     The present invention also is directed to a method for manufacturing a vehicle, including the steps of mounting an electronic unit housing as described herein on a component of the vehicle and painting the component and vehicle together. As described above, this common painting operation is irrelevant to the functional performance of the venting device, since the aerosol laden air produced during painting cannot harm the membrane. 
     Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification. 
     The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, as well as the various steps and the relation of one or more of such steps with respect to each of the others, and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  is a top perspective view of an electronic unit housing according to an embodiment of the present invention; 
         FIG. 2  is a bottom perspective view of the embodiment of the electronic unit housing depicted in  FIG. 1 ; 
         FIG. 3  is a longitudinal cross-sectional view of the embodiment of the electronic unit housing depicted in  FIG. 1 ; 
         FIG. 4  is a transverse cross-sectional view of the embodiment of the electronic unit housing depicted in  FIG. 1 ; 
         FIG. 5  is a longitudinal cross-sectional view of an electronic unit housing according to another embodiment of the present invention; and 
         FIG. 6  is a perspective view of a foot of the embodiment of the electronic unit housing depicted in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawing figures,  FIG. 1  shows an electronic unit housing  10  in the form of, for example, an injection-molded plastic article having a main body  12  and feet  14 . 1 ,  14 . 2  disposed on the two sides of main body  12  and integrally joined to main body  12 . A socket  16  is provided on main body  12 , into which a plug can be inserted and which is designed for connection to a printed circuit board disposed in the main body. 
     Foot  14 . 1  has a fastening eye  18 . 1  in the form of an overmolded metal sleeve. In the same way, foot  14 . 2  comprises a fastening eye  18 . 2 . Feet  14 . 1 ,  14 . 2  are designed to fasten electronic unit housing  10  onto a base such that the housing rests with at least one part of its underside  20  flat on the base. 
       FIG. 2  shows electronic unit housing  10  from its underside  20  so that a cover plate  22  for a receiving space  24  disposed behind it (see  FIG. 3 ) is visible. Cover plate  22  seals off underside  20  flush with feet  14 . 1 ,  14 . 2  or is slightly offset from underside  20 . Cover plate  22  seals receiving space  24  and can be fastened by means of a snap connector  26 , for example. 
       FIG. 2  shows a slot-like external opening  28  via which a venting duct  30  opens to the outside. Venting duct  30  is bounded by a venting-duct wall  32 . 
       FIG. 3  is a cross-sectional view, in longitudinal direction, of electronic unit housing  10  (x-direction; see  FIG. 1 ), through venting duct  30 . A printed circuit board  34  is disposed in receiving space  24 , where it is fastened, for example by means of screws  36 , to electronic unit housing  10 . Relative to underside  20 , cover plate  22  is shifted toward an upper side  38  of electronic unit housing  10 , and, thus, it is not in contact with a base  40  on which electronic unit housing  10  is mounted. 
     Feet  14 . 1 ,  14 . 2  rest within a respective rim  42 . 1 ,  42 . 2  on base  40 . Venting duct  30  ends with its external opening  28  in an inside part of rim  42 . 1  (see  FIG. 2 ). 
     At its end remote from external opening  28 , venting duct  30  has an internal opening  44 , which represents the transition into receiving space  24 . A membrane  46  of, for example, stretched plastic is mounted adjacent to internal opening  44 . The membrane has a pore diameter that allows air to pass but blocks water droplets. Membrane  46  surrounds a cylinder (e.g., formed from rubber), to which a stretched film (e.g., formed from plastic) is attached (e.g., bonded), and is held in electronic unit housing  10  with, for example, a claw ring. 
       FIG. 4  is a sectional view through an air admission duct taken along plane E (see  FIG. 3 ), which runs in a transverse direction of electronic unit housing  10 . Venting duct  30 , viewed in a cross section Q, becomes smaller with increasing distance from the underside. External opening  28  is disposed directly adjacent to rim  42 . 1 . 
       FIG. 5  is a partial/cross-sectional view through venting duct  32  of another embodiment of an inventive electronic unit housing  10 . External opening  28  is covered with a cap  48 , which is attached (e.g., clipped) into recess  50  in foot  14 . 1 . Membrane  46  covers external opening  28  of venting duct  30 . 
     Cap  48  is constructed such that air flowing into venting duct  30  undergoes three changes of direction by respective direction-change angles α 1 , α 2 , α 3  of more than 160° each, as indicated by inflow path  52 . As shown in  FIG. 5 , direction-change angles α 1 , α 2 , α 3  can lie in a common plane, although they are not required to do so. 
       FIG. 6  is a detailed perspective view of the foot according to  FIG. 5 . Cap  48  is fitted into recess  50  such that two air admission slots  54 . 1 ,  54 . 2  are formed. Air admission slots  54 . 1  and  54 . 2  have a width that corresponds to a fraction of the circumference of cap  48 . 
       FIG. 6  shows how rim  42 . 1  surrounds external opening  28  and cap  48  almost completely. Air attempting to pass rim  42 . 1  is able to enter the rim only through air inlets  56 . 1 ,  56 . 2 . Thus, the rim surrounds external opening  28  over a circumferential angle β=β 1  +β 2  of greater than 270° . 
     Cap  48  has a recess  49  and forms, together with foot  14 . 1 , a labyrinth, which causes aerosol particles contained in entering air to be deposited first at ribs  58 . 1 ,  58 . 2  of foot  14 . 1 , before external opening  28  is reached. Ribs  58 . 1 ,  58 . 2  are angled toward one another at an angle of 45° to 135°, for example. Venting duct  30 , membrane  46  and cap  48  are parts of a venting device  60 . 
     Accordingly, the present invention provides an electronic unit housing of simple construction that is robust in its protection against penetration by aerosols (e.g., atomized paint or steam). 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.