Patent Publication Number: US-6340019-B1

Title: Fuel rail mounting bracket with isolator

Description:
FIELD OF THE INVENTION 
     The present invention relates to an isolator design that provides a simple method to incorporate an isolator to a fabricated fuel rail design. Specifically, the invention is a snap-on rail mounting isolator that reduces heat transfer from a metallic intake manifold to a metal-fabricated fuel rail. 
     DESCRIPTION OF RELATED ART 
     Fuel rails for supplying gasoline fuel to an internal combustion engine are well known in the art. These fuel rails generally provide a conduit from which fuel is distributed to a plurality of individual fuel injectors (i.e. “multi-point” fuel injection). 
     In the most common arrangement, fuel is pumped from a fuel reservoir, through a fuel supply line, to the fuel rail. Fuel flows through the fuel rail to a plurality of fuel injectors. The fuel rail is attached to the top of the fuel injectors, and supplies fuel into the upper end of each fuel injector, which then injects the fuel into the intake manifold of the engine. Normally, not all of the fuel passing through the rail is fed to the injectors. The remaining fuel passes through the fuel rail to a fuel return line. Typically, a fuel pressure regulator is employed in the fuel return line downstream of the last injector. Fuel not used by the injectors is then returned to the reservoir via the return line. 
     Vehicle performance problems are a major concern in fuel rail designs. Vehicle barrier issues may negate the use of plastic fuel rails as well as plastic mounting brackets. Moreover, press-fitting an isolator onto a metal fuel rail requires more tooling and increases the number of maintenance issues to be addressed. Increased parts increases the probability of loose parts falling into the manifold and eventually into the engine block, potentially damaging the engine. 
     The need exists for a fuel rail design that does not suffer from the heat transfer problems inherent in the conventional designs and that does not increase the manufacturing, tooling and maintenance problems inherent in the conventional designs. 
     SUMMARY OF THE INVENTION 
     The present invention provides a simple method to incorporate an isolator to a metal fabricated fuel rail design with a minimal snap-on fit attachment load. 
     With the present invention, the number of loose parts during the fuel rail to intake manifold assembly process is reduced. Moreover, if vehicle barrier issues are of a concern, which may negate the use of a plastic fuel rail and a heat sink prone metal fabricated fuel rail is required, vehicle performance problems resulting from hot fuel handling may be addressed by incorporating the plastic isolators. 
     Alternatives to the use of the plastic isolators would be the use of a plastic fuel rail design or incorporating plastic mounting brackets to a metal fuel rail. However, vehicle barrier requirements and fuel rail packaging requirements on the intake manifold, may dictate a metal fuel rail design. 
     The structural arrangement of the present invention provides a fuel rail design that is more cost effective, that will meet stringent packaging and performance requirements, and that may be more conducive to efficient manufacturing initiatives. Barrier concerns can be addressed with use of metal fabricated fuel rails where protection of the fuel system is reduced. Packaging issues can be addressed where the intake manifold requires an unconventional fuel rail design, which may dictate a metal fuel rail process that does not permit a cost effective process such as plastic to be used, yet hot fuel handling may be a concern. Press fitting an isolator onto a metal fuel rail design requires more tooling and maintenance issues to be addressed. A manual, light force snap-fit installed isolator, as proposed by this invention, can make the overall manufacturing process more efficient and effective by improving handling at the assembly plant. 
     The plastic snap-on rail mounting isolator of this invention reduces the heat transfer from a metallic intake manifold to a metal fabricated rail. This heat transferral would potentially cause hot fuel handling vehicle driveability problems as well as heat the excess unused fuel from the fuel rail being returned back to the fuel tank. In turn, this can cause vehicle emission problems. The snap-on feature prevents loose parts from falling into the manifold and eventually into the engine block, potentially damaging the engine. 
     The provision of a simple snap-on plastic isolator with minimal assembly force effectively reduces the heat transfer of the engine to the fuel in the fuel rail assembly, hence reducing vehicle hot fuel handling and emission problems. This invention also affords greater design flexibility in offering customers more cost effective rail designs for their packaging constraints. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of an electronic multi-point fuel injection system and showing a fuel rail assembly; 
     FIG. 2 a  is a top view of an exemplary fuel rail showing two locations of the isolators of this invention; 
     FIG. 2 b  is an end view of the fuel rail assembly of FIG. 2 a;    
     FIG. 3 is a cross sectional view of an isolator assembly according to this invention mounted to an intake manifold; 
     FIG. 4 is a second embodiment of the isolator assembly according to this invention; 
     FIG. 5 is an alternate arrangement of the isolator design. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 1, an electronic multi-point fuel injection system is schematically shown including the fuel tank  10 , fuel pump  20 , fuel feed line  30 , fuel rail  40 , injector valves  50 - 57 , pressure regulator  60 , fuel return line  70 , and fuel filter  80 . Such an electronic multi-point fuel injector system typically uses a computer, engine sensors and one solenoid injector for each engine cylinder. The operation of the electronic multi-point injector system is similar to a modulated, single point injection system; however, fuel is injected at each intake port instead of at the top center of the intake manifold. 
     A multi-point pressure regulator  60  is mounted in the fuel line before or after the injectors and in FIG. 1 the regulator  60  is shown after the injectors. A vacuum line  62  leads from the regulator  60  to the engine intake manifold (not shown). The regulator  60  maintains a constant pressure at the inlet to the injector valves  50 - 57  by acting as a bypass branch. 
     The fuel rail  40  feeds fuel to each injector  50 - 57 , and it primarily consists of a tubing assembly that connects the main fuel line to the inlet of each injector  50 - 57 . One fuel rail design is shown in FIGS. 2 a  and  2   b , where FIG. 2 a  is a top view of a fuel rail layout and FIG. 2 b  is an end view of the fuel rail design of FIG. 2 a . As seen in FIGS. 2 a  and  2   b , the fuel rail  40  receives fuel from the fuel feed line  30 . In FIG. 2 a , six injectors are shown. 
     The plastic isolator design  100  of this invention provides for the isolation of each fuel rail mounting bracket  110  in FIGS. 3 and 4 from the intake manifold mounting boss  120  and the screw assembly  130  that secures the fuel rail assembly  140  to the intake manifold  150 . This isolation reduces the amount of heat transfer from the hot engine intake manifold  150  to the fuel rail assembly  140 , which in turn transfers heat back to the fuel tank via the fuel return line. In the preferred embodiment, isolation of the fuel rail assembly  140  to the intake manifold  150  is accomplished by a two piece nylon 6/6 33% glass filled isolator washer  160  placed between the fuel rail mounting bracket  110  and the manifold mounting boss  120 . An isolator sleeve  170 , of the same material, is placed between the bracket  110  and the screw assembly  130  load-distributing washer  180 . The isolator sleeve  170  has three locking tabs  190 , which snap onto an inside diameter rib  161  on the isolator washer  160 . The screw assembly  130  passes through each of the isolator sleeve  170  and isolator washer and between each locking tab  190  to thereby securely lock each element of the isolator design  100  onto the bracket  110 . 
     The assembly described above and shown in FIG. 3 provides a means of attachment for both isolator parts  160 ,  170  to the fuel rail mounting bracket  110 . This assembly secures the isolator to the bracket  110  of the rail assembly  140  during handling until installation of the rail on the manifold  150  is completed (see FIGS.  3  and  4 ). The locking tabs  190  also provide isolation of the screw assembly  130  with respect to the mounting bracket  110 . 
     FIG. 4 shows a partial view of an alternate layout of the fuel rail  140  and shows the mounting bracket prior to assembly on the manifold where only the bracket  110 , isolator washer  160  and isolator sleeve  170  are shown. 
     FIG. 5 shows an alternate arrangement of the isolator design wherein the placement of the isolator washer  160  and isolator sleeve  170  are reversed. 
     It should be noted that the isolator washer  160  may be made of a stiffer material, such as phenolic, if space is a constraint for the intake manifold  150  and manifold mounting boss  120  surface, as the nylon will require more area to properly distribute the torque load of the rail attaching screwing  130 . Similar and equivalent materials for the isolator member  160 ,  170  will be apparent to those of skill in the art. 
     The competitive benefit of the plastic isolator design is that it provides a simple method to incorporate an isolator to a metal fabricated fuel rail design with a minimal snap-on fit attachment load. The user does not have to handle loose parts during the fuel rail to intake manifold assembly process. Also, if vehicle barrier issues are of a concern, which may negate the use of a plastic fuel rail, and a heat sink prone metal fabricated fuel rail is required, vehicle driveability problems resulting from hot fuel handling may be addressed by incorporating the plastic isolators. 
     The use of plastic isolators can allow for more flexibility in proposing fuel rail design processes that are more cost effective, that will meet stringent customer packaging and performance requirements, and be more conducive to efficient manufacturing capabilities. Barrier concerns can be addressed allowing the use of metal fabricated fuel rails in place of plastic fuel rails, where protection of the fuel system is reduced. Packaging issues can be addressed where the intake manifold requires an unconventional fuel rail design, which may dictate a metallic fuel rail process that does not permit a cost effective process such as plastic to be used, yet hot fuel handling may be a concern. 
     Press fitting an isolator onto a metal fuel rail design requires more tooling and maintenance issues to be addressed. A manual, light force snap-fit installed isolator can make the overall manufacturing process more efficient and effective. 
     The plastic snap-on rail mounting isolators of this invention reduce the heat transfer from a hot intake manifold to a metal fabricated rail. This heat transfer would potentially cause hot fuel handling problems as well as heat the excess unused fuel from the fuel rail being returned back to the fuel tank. In turn, this can cause vehicle emission problems. The snap-on feature prevents loose parts from falling into the manifold and eventually into the engine block, which may potentially damage the engine. 
     While the foregoing invention has been shown and described with reference to a preferred embodiment, it will be understood by those of skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of this invention. For example, the invention has been described with reference to a plastic isolator; however, the invention should not be limited to that material as those skilled in the art may have knowledge of other materials that possess the same properties and benefits associated with the plastic isolator described herein.