Abstract:
A truck has an occupant compartment ( 24 ), an engine compartment ( 20 ) forward of the occupant compartment, and a wiring harness ( 34 ) extending through a dash panel ( 26 ) separating the two compartments from each other. A grommet ( 46 ) is secured at a fixed location on a wire bundle ( 42 ) that passes through the grommet. The dash has a through-opening in which the grommet seats, and the engine compartment side of the grommet includes a bend ( 48 ) that curves generally downward and away from the dash to direct the bundle generally downward on the engine compartment side.

Description:
FIELD OF THE INVENTION 
   This invention relates to the routing of electrical wiring harnesses in motor vehicles, and in particular to a wiring harness having a grommet that mounts in a through-opening in a dash panel and through which a wire bundle is routed between an occupant compartment and an engine compartment. 
   BACKGROUND OF THE INVENTION 
   Most motor vehicles that operate on roads and highways typically have an occupant compartment, where the driver and any passenger or passengers sit, and in front of the occupant compartment, an engine compartment for housing the engine that propels the vehicle. 
   Certain electrical devices, such as driver information displays and various controls, are present inside the occupant compartment. Certain ones of those devices need to be in electrical communication with vehicle components that are disposed outside the occupant compartment. Those components include the engine and the transmission through which the engine is coupled with the drivetrain. 
   Consequently it is common practice to bundle wires into wiring harnesses having some connectors that make connections to electrical devices inside the occupant compartment and other connectors that make connections to components that are outside the occupant compartment. Necessarily, such harnesses must pass through a wall shared by the two compartments. Such a wall is sometimes referred to as a dash panel, or simply a dash. 
   Because a number of vehicle components and systems are disposed on or in close proximity to the dash, available space for routing wiring harnesses through the dash is typically at a premium. The location of a wiring harness pass-through in the dash is not the only consideration in the design phase of motor vehicles; the nature of the pass-though is also a consideration. 
   One type of pass-through comprises a grommet that fits to a through-opening in the dash and through which bundled wires pass. Such a grommet may be affixed in some suitable way to the bundled wires so as to be immovable along the length of the harness. Installation of such a harness involves feeding one or more connectors through the through-opening and then pulling the harness until the grommet seats in the through-opening. In that type of pass-through, any connector that must be fed through the dash opening must be small enough in size to freely pass through. 
   Another type of pass-through is somewhat different in that the through-opening in the dash serves as the location where a harness that is inside the occupant compartment mates with a harness that extends into the engine compartment. Mating of the two harnesses is via one connector in one harness mating with another connector in the other harness at the dash. These are sometimes referred to as bulkhead connectors. For example, the occupant compartment harness can terminate in a connector that fits to the through-opening on one side of the dash and is mounted in any suitable way to the dash. The other harness terminates in a mating connector that plugs into the connector on the occupant compartment side of the dash. This type of pass-through is typically more expensive not only because the bulkhead connectors are required, but because other design and manufacturing issues often arise. 
   One of those other issues may be the sequence of steps in assembling a vehicle. Certain motor vehicles have what is sometimes called a body-frame construction. A frame provides the structure for mounting chassis components that form the vehicle powertrain. A body forms the occupant compartment, and at some point in the vehicle assembly process, the body is placed on and fastened to the frame. In the case of a truck, the body is sometimes referred to as the cab. 
   Assuming that many powertrain components, including the engine, transmission, and drivetrain, have been already mounted on the frame at the time that the body is placed on the frame, it then becomes necessary to make connection of engine compartment wiring harness connectors with corresponding occupant compartment wiring harness connectors. Available space considerations after body placement may render it difficult for assembly line personnel to efficiently make those connections. 
   Certain vehicle models that use essentially the same platform may have different electrical devices and components from vehicle to vehicle. Consequently, while the vehicles are generally similar, the wiring may differ from vehicle to vehicle. This means that some wiring harnesses may have more wires in a bundle and other harnesses fewer wires. Consequently, the diameter of a wiring harness passing through the dash in some vehicles will be larger than in others. The wiring harness through-openings in a dash panel are typically created at the time the dash panel is manufactured, typically by punching in sheet metal during the dash panel stamping process. While it would be possible to manufacture dash panels with different sized wiring harness through-openings, that would introduce complexities that would far outweigh the benefits. Therefore it is typical for a wiring harness through-opening in a dash that is common to different vehicle models to have a common size that can accommodate wire bundles of different diameters depending on the particular number and size of wires in a harness needed to satisfy requirements for the respective models and their electrical equipment. 
   Sealing of a grommet to bundled wires in a wiring harness may also be important in order to provide weather- and sound-tightness through the grommet. U.S. Pat. Nos. 5,270,487 and 6,402,155 are examples of grommets that have sealant within the grommet that aids in sealing to the wire bundle passing through the grommet opening. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a novel grommet, wiring harness, and installation in a motor vehicle. The invention allows an occupant compartment wiring harness to extend through a dash and some distance into the engine compartment where it can be conveniently connected with a mating harness to electrically connect electrical devices inside the occupant compartment with vehicle components that are disposed outside the occupant compartment. 
   The invention is especially suitable for use with pre-existing vehicle platforms and models to allow new electrical features, components, and devices to be incorporated without extensive re-design of major body components like a dash panel and cowl tray for example as well as major systems like a HVAC system that are closely integrated with the dash panel. Avoiding extensive structural re-design avoids the costs that would be associated with new or redesigned tooling. 
   The invention provides for a single size grommet to accommodate wiring harnesses of different diameter while enabling suitable sealing between the grommet and the wire bundle passing through the grommet to be conveniently achieved. The grommet also has a configuration that when installed in a dash through-opening directs the wire bundle generally downward thereby also tending to shed away water, road splash, etc. 
   A wiring harness comprising such a grommet allows connections to be made inside the occupant compartment to electrical devices inside the occupant compartment and an engine compartment connector, or connectors, to be passed through a dash panel through-opening. On the engine side of the dash, the harness is pulled through until the grommet reaches the dash at which point it is manipulated to seat it in the through-opening. Preferably, the shape of the through-opening is polarized so that the grommet can seat in the through-opening in a specific orientation where the portion of the grommet on the engine compartment side of the dash will curve about 90° and extend generally downward. 
   The downwardly extending portion of the grommet on the engine compartment side forms a collar around the wiring harness bundle, and by making the collar sufficiently deformable, it can be banded by a strap that girdles and is tightened around the collar to force the collar against bundle, thereby aiding in sealing the grommet to the bundle and in assuring that the grommet is located at a desired location along the length of the harness. 
   Because the grommet need not be molded onto the wiring bundle, a wiring harness that includes the grommet can, within limits, comprise different numbers and sizes of wires. This allows such a harness to be fabricated at a harness maker by threading insulated wires individually, or in groups that may or may not be protectively wrapped, through the grommet, and connectors assembled to the stripped ends of the wires after the wires have been so threaded. 
   One generic aspect of the present invention relates to a motor vehicle comprising an occupant compartment, an engine compartment forward of the occupant compartment, and a wiring harness extending through a wall separating the two compartments from each other. A grommet is secured at a fixed location on a wire bundle that passes through the grommet. The wall comprises a through-opening in which the grommet seats, and the engine compartment side of the grommet comprises a bend that curves generally downward and away from the wall to direct the bundle generally downward on the engine compartment side. 
   Another generic aspect of the present invention relates to a motor vehicle wiring harness comprising a wire bundle having connectors at opposite ends and a grommet that comprises a through-passage through which the wire bundle passes and that is secured at a fixed location on the wire bundle intermediate the connectors at opposite ends. The through-passage comprises a curved bend, and the grommet comprises, on its exterior, an endless perimeter lip comprising an endless perimeter groove for seating the grommet in a through-opening in a wall of a motor vehicle. 
   Still another generic aspect of the present invention relates to a method of installing a wiring harness in a motor vehicle that has an interior compartment, an exterior compartment adjacent the interior compartment, and a wall separating the two compartments from each other. The method comprises passing one or more connectors at one end of a wire bundle through a through-opening in the wall in a direction from one compartment to the other. Then advancing more of the wire bundle through the through-opening in the same direction until the wire bundle has been advanced sufficiently to place a grommet that has a substantially right angle curved bend, through and along which the wire bundle passes, immediately proximate the through-opening on one side of the wall. Then one end of the grommet is inserted into and through the through-opening, and the grommet is advanced further to pass its curved bend through the through-opening until the curved bend is disposed on the other side of the wall so as to direct the wire bundle exiting the one end of the grommet in the other compartment substantially at a right angle to the wire bundle exiting an opposite end of the grommet in the one compartment. 
   The foregoing, along with further features and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, now briefly described as follows. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a portion of the interior of a truck&#39;s engine compartment showing a portion of a wiring harness embodying principles of the invention. 
       FIG. 2  is perspective view showing a grommet that is on the wiring harness. 
       FIG. 3  is a side elevation view of the grommet. 
       FIG. 4  is a view in the direction of arrows  4 - 4  in  FIG. 3 . 
       FIG. 5  is a view in the direction of arrows  5 - 5  in  FIG. 3 . 
       FIG. 6  is a left side view of  FIG. 3 . 
       FIG. 7  is a view in the direction of arrows  7 - 7  in  FIG. 6 . 
       FIG. 8  is a view similar to  FIG. 2  showing another embodiment of grommet. 
       FIG. 9  is a side elevation view of the grommet of  FIG. 8 . 
       FIG. 10  is a view in the direction of arrows  10 - 10  in  FIG. 9 . 
       FIG. 11  is an enlarged view in circle  11  in  FIG. 10 . 
       FIG. 12  is a left side view of  FIG. 9 . 
       FIG. 13  is a right side view of  FIG. 9 . 
       FIG. 14  is a view in the same direction as  FIG. 13  showing a third embodiment of grommet. 
       FIG. 15  is a right side view of  FIG. 14 , partly in cross section. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a portion of an engine compartment  20  of a highway truck  22  that is forward of an occupant compartment  24 . A dash  26  separates the two compartments below a cowl area  28  and windshield  30 . Engine compartment  20  houses an engine  32  that forms part of the truck&#39;s powertrain. 
   One portion of a wiring harness  34  is disposed inside occupant compartment  24  and can&#39;t be specifically seen in  FIG. 1 . Another portion of wiring harness  34  is disposed in engine compartment  20  and can be seen in  FIG. 1 . The latter portion extends from dash  26  some distance into engine compartment  20  where it terminates in a connector  36  shown mated with another connector  38 . Connector  38  is part of an engine/powertrain wiring harness  40  that has other connectors (not visible in  FIG. 1 ) that connect with vehicle electrical components that are disposed either in engine compartment  20  or the underlying chassis. With the two harnesses  34 ,  40  connected together, electrical devices inside occupant compartment  24  are electrically connected with electrical components outside the occupant compartment. 
   Each harness  34 ,  40  comprises a respective wire bundle  42 ,  44  that may be protectively wrapped. Harness  34  further comprises a grommet  46  that mounts the harness on dash  26  on a lateral side of the vehicle fore-aft centerline opposite the side where connectors  36 ,  38  make connection to each other. Grommet  46  has a construction that directs wire bundle  42  generally downward as it enters engine compartment  20 . Grommet  46  is shown by itself in more detail in  FIGS. 2-7 . 
   Those Figures show grommet  46  to comprise a through-passage  48  having opposite ends  50  and  52  where wire bundle  42  enters and exits. An endless perimeter lip  54  comprising an endless perimeter groove  56  surrounds end  50 . At end  50 , through-passage  48  has a transverse cross sectional shape that is defined by a horizontal lower edge  58 , side edges  60 ,  62  extending upward from opposite ends of edge  58  at substantially right angles to edge  58 , and a downwardly concave upper edge  64  extending between upper ends of side edges  60 ,  62 . At end  50 , through-passage  48  has a transverse cross section whose area is larger than that of the through-passage at end  52 . 
   Immediately beyond lip  54 , the wall of grommet  46  that defines through-passage  48  comprises a 90° bend  64 . The transverse cross section of the through-passage progressively diminishes throughout the 90° of the bend until the bend merges into an initially circular walled section  66  that continues downward in a narrowing tapered section  68  that leads to a short straight circular section  70  ending at end  52 . 
   The downwardly extending portion of grommet  46  on the engine compartment side of dash  26  that comprises sections  66 ,  68 ,  70  forms a collar around the wiring harness bundle. In grommet  46 , section  70  may be considered to be the collar. By making the collar sufficiently deformable, it can be banded by a strap (like the one shown in  FIG. 15 ) that girdles and is tightened around the collar to force the collar against the wire bundle passing through the grommet, thereby aiding in sealing the grommet to the bundle and in assuring that the grommet is located at a desired location along the length of the harness. 
   Dash  26  comprises a through-opening in which grommet  46  seats. The shape of the through-opening is substantially congruent with that of groove  56  so as to allow the margin of the through-opening to lodge in groove  56  when grommet  46  is seated in the through-opening. The shape of the through-opening in dash  26  is polarized so that grommet  46  can seat in the through-opening only in a unique orientation where the portion of the grommet on the engine compartment side of the dash will curve about 90° and extend generally downward, as shown in  FIG. 1 . 
   Because grommet  46  is not molded onto wire bundle  42 , a wiring harness that includes grommet  46  can, within limits, comprise different numbers and sizes of wires. This allows a harness like harness  34  to be fabricated at a harness maker by threading insulated wires individually, or in groups that may or may not be protectively wrapped, through the grommet, and connectors assembled to the stripped ends of the wires after the wires have been so threaded. 
   Wiring harness  34  can be connected to devices inside occupant compartment  24 , and connector  36  can be passed through the dash through-opening in the direction from occupant compartment  24  to engine compartment  20 . On the engine side of dash  26 , harness  34  can be pulled through until grommet  46  reaches the through-opening in dash  26 , at which point the grommet is manipulated to seat it in the through-opening.  12 . Seating can be facilitated by personnel who install the harness manually grasping a tab  72  on the exterior of the grommet wall at bend  64  opposite the dash through-opening and pulling the grommet into seating in the through-opening. Then connectors  36 ,  38  can be mated. 
     FIGS. 8-13  show another embodiment of grommet  80  that is like grommet  46 . It differs in that beyond bend  48 , the section  82  that extends vertically downward is not tapered, but rather has a constant cross section.  FIG. 11  shows more detail of lip  54  and groove  56 . 
     FIGS. 14-15  show another embodiment of grommet  90  that is generally like grommet  46 . It differs in certain details such as the shape of end  50 , and in the inclusion of an insert  92  that gives shape to bend  48 . It does show a strap  94  banding the grommet to the wire bundle immediately proximate end  52 . 
   While a presently preferred embodiment of the invention has been illustrated and described, it should be appreciated that principles of the invention apply to all embodiments falling within the scope of the following claims.