Abstract:
Methods and apparatus are provided for electrostatic discharge mitigation for a fuel module. In one embodiment, the system includes a fuel pump having a power and ground connection for pumping fuel. A fuel filter in fluid communication with the fuel pump, the fuel filter including one or more components made of a non-conductive plastic and having a sulfonated surface covered with a conductive surface formed over the sulfonated surface. The conductive surface is electrically coupled to the vehicle ground plane. A method is provided for mitigation of electrostatic discharge in a fuel module. In one embodiment, the method includes sulfonating non-conductive plastic components of the fuel module to provide a sulfonated layer on the non-conductive plastic components and forming a conductive layer over the sulfonated layer to provide an electrical discharge path for electrostatic buildup resulting from fuel moving through the fuel module.

Description:
TECHNICAL FIELD 
     The technical field generally relates to fuel delivery modules for motor vehicles that provide fuel from fuel reservoirs, and more particularly to fuel delivery modules capable of mitigating electrostatic discharge resulting from fuel flow through the fuel module. 
     BACKGROUND 
     It is known that conduit structures that are exposed to turbulent fuel flow may, under some circumstances, acquire an electrostatic (or static electric) charge. Left unabated, electrostatic charge buildup can lead to spontaneous discharge if and when the charge exceeds the breakthrough voltage between the charged element and nearest ground which may ultimately lead to failure of the conduit requiring replacement. Accordingly, it is common to provide a conductive path to the vehicle ground plane to discharge any static charge that may be developed in conduits such as fuel delivery modules for vehicles. Plastic materials employed for fuel delivery module, such as polyoxymethylene (POM), are generally not conductive and so are typically combined or impregnated with conductive additives (such as carbon powders, carbon fibers or stainless steel fibers) to increase conductivity. These additives generally reduce the tensile or creep strength of the material and may react differently when exposed to environmental input such as heat and fuel compared to the base plastic. Further, these materials may be higher cost and require more complex processing. Accordingly, it is preferred to minimize the use of these conductive additives. 
     Accordingly, due to its lower cost and higher strength it is desirable to use non-conductive polyoxymethylene in fuel modules for vehicles. In addition, it is desirable to use a non-conductive polyoxymethylene that can be made conductive without a reduction in material strength or performance. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
     SUMMARY 
     A system is provided for a fuel delivery module with electrostatic discharge mitigation. In one embodiment, the system includes a fuel pump having a power and ground connection for pumping fuel. A fuel filter in fluid communication with the fuel pump, the fuel filter including one or more components made of a non-conductive plastic and having a sulfonated surface covered with a conductive surface formed over the sulfonated surface. The conductive surface is electrically coupled to the ground connection of the fuel pump (or other suitable connection to the vehicles ground plane). The system includes a fuel exit port in fluid communication with the fuel filter, the fuel exit port being formed from a non-conductive plastic having a sulfonated interior surface with a conductive surface formed over the sulfonated interior surface and also electrically coupled to the ground connection of the fuel pump. 
     A method is provided for mitigation of electrostatic discharge in a fuel module. In one embodiment, the method includes sulfonating non-conductive plastic components of the fuel delivery module to provide a sulfonated layer on the non-conductive plastic components and forming a conductive layer over the sulfonated layer to provide an electrical discharge path for electrostatic buildup resulting from fuel moving through the fuel module. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is an illustration of a vehicle in accordance with an embodiment; 
         FIG. 2  is an illustration of a fuel module in accordance with an embodiment; and 
         FIG. 3  is an illustration of a process for forming sulfonation and conductive layers on components of the fuel module in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. 
     In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. 
     Additionally, the following description refers to elements or features being “connected” or “coupled” together. As used herein, “connected” may refer to one element/feature being directly joined to (or directly communicating with) another element/feature, and not necessarily mechanically. Likewise, “coupled” may refer to one element/feature being directly or indirectly joined to (or directly or indirectly communicating with) another element/feature, and not necessarily mechanically. However, it should be understood that, although two elements may be described below, in one embodiment, as being “connected,” in alternative embodiments similar elements may be “coupled,” and vice versa. Thus, although the schematic diagrams shown herein depict example arrangements of elements, additional intervening elements, devices, features, or components may be present in an actual embodiment. 
     Finally, for the sake of brevity, conventional techniques and components related to vehicle electrical and mechanical parts and other functional aspects of the system (and the individual operating components of the system) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the invention. It should also be understood that  FIGS. 1-3  are merely illustrative and may not be drawn to scale. 
     Referring to the drawings, wherein like reference numbers refer to like components,  FIG. 1  shows a vehicle  100  according to exemplary embodiments. In addition to the illustrated vehicle, the vehicle  100  may be any one of a number of different types of vehicles, such as, for example, air craft, water craft, motorcycle, off-road vehicles, or other motor vehicles including a sedan, a wagon, a truck, or a sport utility vehicle (SUV), and may be two-wheel drive (2WD), four-wheel drive (4WD), or all-wheel drive (AWD). 
     In  FIG. 1  the simplified illustrated embodiment of vehicle  100  includes, without limitation: a vehicle engine  102  coupled to a fuel reservoir  104  via a fuel conduit  106 . The engine  102  may be any one of, or combination of, a number of different types of engines, such as, for example, a gasoline or diesel fueled combustion engine, a flex fuel vehicle (FFV) engine (i.e., using a mixture of gasoline and alcohol), a gaseous compound (e.g., hydrogen and/or natural gas) fueled engine, a combustion/electric motor hybrid engine, and an electric motor. Fuel is provided to the engine  102  via the fuel conduit  106  from a fuel module  108 . Fuel may be added to the fuel reservoir from time to time via a fill tube  110 . During operation, the engine  102  drives wheels  112  via drive shafts  114  to propel the vehicle  100 . 
     Referring now to  FIG. 2 , a schematic diagram of the fuel module  108  of  FIG. 1  is shown in accordance with various embodiments. The fuel module  108  may include a fuel pump, fuel filter, pressure regulator, and other components, and may be housed in a plastic housing  200  and a module cover  202  which provides for sealing the fuel module into the fuel tank. Fuel enters the housing  200  (if used in a particular implementation) from the fuel reservoir (not shown in  FIG. 2 ) via a one-way valve  204  (e.g., a check valve). Although illustrated as positioned on the bottom of the housing  200 , it will be appreciated that the check valve could be positioned in other locations on the housing  200 . A fuel pump  206  draws fuel through a fuel strainer  208  as indicated by the fuel flow arrow  210 . The pumped fuel (indicated by arrow  212 ) is then sent via a connector conduit  214  to a fuel filter  216 . A pressure relief valve  218  is located on the fuel filter  216  which opens to maintain pressure to a limit determined according to the implemented embodiment. The filtered fuel (indicated by arrows  220 ) passes through a filter conduit  222  as indicated by arrow  224  to a fuel exit port  226  from which the fuel (indicated by arrow  228 ) is delivered to the engine ( 102  in  FIG. 1 ) via the fuel conduit  106  (in  FIG. 1 ). The fuel exit port  226  is sealingly connected with the cover  202  which, in turn, sealingly seated to the housing  200 . In some embodiments, guide rods  230  guidably interconnect the cover  202  with the housing  200 . 
     In order to supply electricity to operate the fuel pump  206  a power lead  232  (or series of leads) and a ground (or chassis) lead  234  are provided for the fuel pump  206 . As noted above, conduits or surfaces exposed to turbulent fuel flow may, under some circumstances, acquire an electrostatic (or static electric) charge. Left unabated, electrostatic charge buildup can lead to spontaneous discharge if and when the charge exceeds the breakthrough voltage between the charged element and nearest ground which may ultimately lead to failure of the exposed components requiring replacement. A conductive path to the vehicle ground plane is provided to discharge any static charge that may be developed. In some embodiments, this conductive path is provided from the ground lead  243  that is coupled to the fuel pump  206 . The conduit  214  is made conductive, which provides a ground path to the fuel filter  216 . In some embodiments, the fuel filter is provided with a discharge to ground path via an optional ground lead  236 . 
     Accordingly to exemplary embodiments, various components of the fuel module  108  are formed of non-conductive polyoxymethylene (POM) and made conductive via a sulfonation process prior to forming a conductive layer over a sulfonation layer formed on the component by the sulfonation process that will be discussed in detail in connection with  FIG. 3 . Normally, non-conductive polyoxymethylene does not adhere or bond to conductive layers, causing the use of conductive fibers, powders or other additives throughout the base plastic matrix. However, the sulfonation process facilitates bonding conductive material to the surface of the non-conductive polyoxymethylene, permitting this material to support discharging electrostatic buildup in embodiments of the fuel module  108 . 
     Referring now to  FIG. 3 , an exemplary portion of a component of the fuel module  108  is shown. While any component of the fuel module  108  could employ this process, typically, some of the components of the fuel module  108  are made of various materials and by various processes, and may not need to use the sulfonation and conductive layer process according to exemplary embodiments. Those components (and/or the surfaces thereof) that could particularly benefit from the sulfonation and conductive layer process will be discussed below in connection with  FIG. 4 . 
     In some embodiments, the base material  300  of a component of the fuel module  108  is made of non-conductive polyoxymethylene (POM). As used herein sulfonation refers to a process by which a component is exposed to an atmosphere of sulfur-dioxide or sulfur-trioxide sufficient to form a sulfonation layer  302  on the base material  300 . After the sulfonation process, a conductive layer  304  may be applied over the sulfonation layer  302  via conventional plating, sputtering or vapor deposition techniques. In some embodiments, the conductive layer is formed of a fuel compatible material such as tin, nickel, gold or palladium. 
     With reference back to  FIG. 2 , a variety of components of the fuel delivery module  108  can benefit from the process of  FIG. 3 . Typically, those components coming into contact with increased fuel turbulence could particularly benefit from the embodiments of the present disclosure. For example, the fuel filter  216  includes a filter cover  240  and filter housing  242 . The interior surface  244  of the filter cover  240  typically experiences fuel applied under the pressure provided by the fuel pump  206 , which may be a turbulent flow. In some embodiments a ground discharge path is provided by the connector conduit  214  to the ground lead  234  of the fuel pump  206 . However, the connector conduit may be an extruded part made of polyamide, polyethylene, POM, or Polyvinylidene fluoride (PVDF) that can be made conductive via conventional coextruded multilayer construction techniques where the inner layer is compounded with conductive additives as described above. However, if the connector conduit  214  were made of non-conductive polyoxymethylene, the interior surface  246  could be sulfonated and have a conductive layer applied. In some embodiments, a ground discharge path may be provided to the fuel filter  216  via a direct ground lead  236 . In such embodiments, it would be useful for the exterior surface  248  of the filter cover  240  to also be sulfonated and made conductive as discussed in connection with  FIG. 3 . In some embodiments, the interior surface  250  of the filter housing  402  could benefit from the sulfonation and conductive layering process of  FIG. 3 . 
     Another component experiencing high fuel flow that may cause turbulence is the filter conduit  222 . In some embodiments, the filter conduit  222  is an extruded component made of polyamide, polyethylene, POM, or Polyvinylidene fluoride (PVDF) that can be made conductive via conventional coextruded multilayer construction techniques where the inner layer is compounded with conductive additives as described above. However, if the filter conduit  222  were made of non-conductive polyoxymethylene, the interior surface  252  could be sulfonated and have a conductive layer applied. 
     Still another component experiencing high fuel flow that may lead to turbulence is the fuel exit port  226 . In some embodiments, the fuel port  226  is formed as an elbow having an inlet  254 , and outlet  256  and an angled portion  258 . This configuration may cause fuel flowing through the fuel exit port  226  to experience a 90 degree change in direction. Thus, there is an increased possibility for fuel flow turbulence to develop within the fuel exit port  226 . Accordingly, the interior surface  260  (or at least the portion thereof forming the angled portion  258 ) could be sulfonated and have a conductive layer applied. 
     Accordingly, an improved fuel module is provided for a vehicle having electrostatic buildup discharge protection. The sulfonation process allows a conductive layer to be applied over materials such as non-conductive polyoxymethylene without causing the material to become brittle or difficult to mold. The sulfonation and conductive layering process may be used selectively on some components or component surfaces as it is electrically compatible with other components made conductive via conventional techniques. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the appended claims and the legal equivalents thereof.