Abstract:
A filter assembly is disclosed for use with a fuel system. The filter assembly may have a base with a first side, and a second side opposite the first side. The filter assembly may also have a filter extending from the first side of the base, a valve extending from the second side of the base, and a metallic cover having a closed end surrounding the valve and an open end located adjacent the second side of the base. The filter assembly may further have a seal sandwiched between the metallic cover and the base, a retainer connected to the base and extending over the metallic cover, and a fastener threadingly engaged with the retainer and protruding inward to press the metallic cover toward the base.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to a fuel system and, more particularly, to a fuel system having a filter assembly with a valve cover. 
       BACKGROUND 
       [0002]    A typical fuel system includes a pump that draws fuel from a tank, pressurizes the fuel, and directs the pressurized fuel through a supply passage and filter to one or more fuel injectors. A first check valve is disposed within a return line that extends from the fuel injectors back to the tank, and a second check valve is disposed in parallel with the filter. In order for the fuel system to function properly, the system should be generally free of air and free of undue flow restrictions (e.g., restrictions caused by plugging of the filter). 
         [0003]    Historically, the air-free and restriction-free status of a fuel system was confirmed by way of one or more sight-glasses plumbed in-line with the first and second check valves. For example, a first sight-glass was associated with the first check valve and used to determine that the supply and return passages were free of air, while a second sight-glass was associated with the second check valve and used to determine that the filters were not clogged. In particular, when the first sight-glass was full of fuel, it could be concluded that the supply and return passages were generally air-free. And as long as the second sight-glass was empty of fuel, it could be concluded that the filter was creating little restriction on the fuel flow. Such a system is disclosed in a maintenance manual entitled “645E BLOWER-TYPE ENGINE MAINTENANCE MANUAL”, 5 th  edition, which was published in January 1980. 
         [0004]    A conventional sight-glass includes a transparent glass bowl that is inverted, having its rim pressed against a cast filter base. A gasket or other seal is sandwiched between the rim of the glass bowl and a machined face of the base. An arcuate bracket extends from the base at one side of the glass bowl over the closed end of the glass bowl to an opposing side. A bolt is threadingly engaged with the bracket at a center of the glass bowl, and is adjustable to press the center downward toward the rim. This downward pressing functions to urge the rim of the glass bowl against the gasket, thereby sealing the sight-glass against the base. 
         [0005]    Although the use of a sight-glass may be effective in determining the status of a fuel system, the sight-glass can also be problematic. In particular, the sight-glass (e.g., the glass bowl and/or the arcuate bracket holding the glass bowl) is subject to extreme vibration in some applications. These vibrations, if not accounted for, can cause the glass bowl and/or the arcuate bracket to fail. 
         [0006]    The disclosed fuel system and filter assembly are directed to overcoming one or more of the problems set forth above and/or other problems of the prior art. 
       SUMMARY 
       [0007]    In one aspect, the present disclosure is directed to a filter assembly for a fuel system. The filter assembly may include a base with a first side, and a second side opposite the first side. The filter assembly may also include a filter extending from the first side of the base, a valve extending from the second side of the base, and a metallic cover having a closed end surrounding the valve and an open end located adjacent the second side of the base. The filter assembly may further include a seal sandwiched between the metallic cover and the base, a retainer connected to the base and extending over the metallic cover, and a fastener threadingly engaged with the retainer and protruding inward to press the metallic cover toward the base. 
         [0008]    In another aspect, the present disclosure is directed to another filter assembly for a fuel system. This filter assembly may include a base having a first side and a second side opposite the first side, a filter extending from the first side of the base, and a valve extending from the second side of the base. The filter assembly may also include a cover having a closed end surrounding the valve and an open end located adjacent the second side of the base, and a seal sandwiched between the metallic cover and the base. The filter assembly may further include a retainer having first and second sides connected to the base, and a third side extending over the cover between the first and second sides. The first, second, and third sides may form a generally C-shaped channel. The filter assembly may additionally include a fastener threadingly engaged with the third side of the retainer and protruding inward to press the cover toward the base. 
         [0009]    In yet another aspect, the present disclosure is directed to a fuel system. The fuel system may include a tank, a pump connected to draw fuel from the tank, a plurality of fuel injectors, and a manifold connecting the pump to the plurality of fuel injectors. The fuel system may also include a filter assembly disposed between the pump and the manifold. The filter assembly may have a base with a first side and a second side opposite the first side, a filter extending from the first side of the base, a first valve extending from the second side of the base, and a second valve located adjacent the first valve and extending from the second side of the base. The fitter assembly may additionally have a first metallic cover with a closed end surrounding the first valve and an open end located adjacent the second side of the base, and a second metallic cover with a closed end surrounding the second valve and an open end located adjacent the second side of the base. The filter assembly may further have a seal sandwiched between each of the first and second metallic covers and the base; and a first retainer with first and second sides connected to the base, and a third side extending over the first metallic cover between the first and second sides. The first, second, and third sides of the first retainer may form a first generally C-shaped channel. The filter assembly may also have a second retainer with first and second sides connected to the base, and a third side extending over the second metallic cover between the first and second sides. The first, second, and third sides of the second retainer may form a second generally C-shaped channel. The filter assembly may further have a first fastener threadingly engaged with the third side of the first retainer and protruding inward to press the first metallic cover toward the base, a second fastener threadingly engaged with the third side of the second retainer and protruding inward to press the second metallic cover toward the base, and a safety wire passing through a head of at least one of the first and second fasteners to inhibit loosening of the at least one of the first and second fasteners. The first and second metallic covers may each include a lip located at the open end to engage the seal and having a circular-lay roughness of about 125 μinch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0010]      FIG. 1  is a diagrammatic and schematic illustration of an engine having an exemplary disclosed fuel system; 
           [0011]      FIG. 2  is a cross-sectional illustration of an exemplary disclosed filter assembly that may be used in conjunction with the fuel system of  FIG. 1 ; and 
           [0012]      FIGS. 3 and 4  are isometric illustrations of exemplary filter assembly embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  illustrates an engine equipped with having a fuel system  12 . For the purposes of this disclosure, engine  10  is depicted and described as being a four-stroke diesel engine. One skilled in the art will recognize, however, that engine  10  may embody any other type of internal combustion engine such as, for example, a two-stroke diesel, gasoline, or gaseous fuel-powered engine. Engine  10  may include a block  14  that at least partially defines a plurality of combustion chambers  16 . In the illustrated embodiment, engine  10  includes four combustion chambers  16 . However, it is contemplated that engine  10  may include a greater or lesser number of combustion chambers  16  and that combustion chambers  16  may be disposed in an “in-line” configuration, in a “V” configuration, in an opposing-piston configuration, in a rotary configuration, or in any other suitable configuration. 
         [0014]    As also shown in  FIG. 1 , engine  10  may include a crankshaft  18  that is rotatably disposed within block  14 . A connecting rod (not shown) associated with each combustion chamber  16  may connect a piston (not shown) to crankshaft  18  so that a sliding motion of each piston within the respective combustion chamber  16  results in a rotation of crankshaft  18 . Similarly, a rotation of crankshaft  18  may result in a sliding motion of the pistons. 
         [0015]    Fuel system  12  may include components that cooperate to deliver injections of pressurized fuel into each combustion chamber  16 . Specifically, fuel system  12  may include a tank  20  configured to hold a supply of fuel; and a pump  22  connected to draw fuel from tank  20 , to pressurize the fuel, and to direct the pressurized fuel to a plurality of fuel injectors  24  by way of a manifold  26 . Pump  22  may be connected to tank  20  via a suction passage  28 , and to manifold  26  via a supply passage  29 . A check valve  30  may be disposed within suction passage  28 , if desired. Manifold  26  may be connected to tank  20  via a return passage  34 . 
         [0016]    Pump  22  may be connected with crankshaft  18  in any manner readily apparent to one skilled in the art, where a rotation of crankshaft  18  will result in a corresponding rotation of a pump driveshaft. For example, pump  22  is shown in  FIG. 1  as being connected to crankshaft  18  through a gear train. It is contemplated, however, that pump  22  may alternatively be driven electrically, hydraulically, pneumatically, or in another appropriate manner. 
         [0017]    Fuel injectors  24  may be disposed within cylinder heads (not shown) of engine  10 , and sequentially fluidly connected to manifold  26 . Fuel injectors  24  may be directly connected to manifold  26  such that all of the fuel flowing through manifold  26  also flows through each individual injector  24  or, alternatively, fuel injectors  24  may be connected to common manifold  26  by a plurality of individual fuel lines  32 . Each fuel injector  24  may be operable to inject an amount of pressurized fuel into an associated combustion chamber  16  at predetermined timings, fuel pressures, and quantities. The timing of fuel injection into combustion chamber  16  may be synchronized with the motion of the corresponding piston (not shown) reciprocatingly disposed therein. In the depicted embodiment, fuel injectors  24  are mechanical unit injectors (MUI injectors). It is contemplated, however that fuel injectors  24  could alternatively embody mechanically-actuated, electronically-controlled unit injectors (MEUI injectors); hydraulically actuated, electronically-controlled unit injectors (HEUI injectors); or any other type of fuel injectors known in the art. 
         [0018]    A filter assembly  36  may be plumbed between pump  22  and manifold  26 , and also between manifold  26  and tank  20 . As shown schematically in  FIG. 2  and physically in  FIGS. 3 and 4 , filter assembly  36  may include a base  38 , and one or more canister filters (filters)  40  hanging from a lower side  42  of base  38 . First and second check valves  44 ,  46  may be mounted to an upper side  48  of base  38  opposite filters  40 . During normal operation (e.g., when filters  40  are not plugged), pressurized fuel from pump  22  may flow into base  38  and split via a pair of branch passages  50  into two parallel flows that pass through filters  40 . The separate flows may then recombine within base  38  and be discharged as a single flow to manifold  26 . 
         [0019]    During abnormal conditions, for example when plugging of one or more of filters  40  creates a restriction to the flow through branch passages  50 , a fuel pressure inside base  38  may rise. This high-pressure fuel, in addition to communicating with filters  40 , may also be directed to check valve  46  via a bypass passage  52 . When the fuel pressure exceeds an opening pressure of check valve  46  (e.g., about 60 psi), check valve  46  may open and allow the fuel to pass back to tank  20  via return passage  34 . 
         [0020]    Check valve  44  may be in communication with return passage  34  (e.g., via a passage  54  formed in base  38 ), and function as a priming valve. In particular, during startup of pump  22 , check valve  44  may remain closed, allowing the fuel pumped into manifold  26  to build in pressure. When manifold  26  has been adequately filled with fuel, and the fuel therein reaches a desired operating pressure (e.g., about 5 psi or higher), check valve  44  may open and allow excess fuel and air to pass from return passage  34  through passage  54  to tank  20 . Thus, during normal operation of fuel system  12 , some fuel should continuously be passing through check valve  44 . 
         [0021]    In earlier iterations of fuel system  12 , sight glasses  56  (shown as dashed lines only in  FIG. 2 ) were disposed over check valves  44  and  46 , and formed portions of passages  52  and  54 . In particular, after the fuel was discharged from check valves  44 ,  46 , the fuel exited base  38  and entered into an interior space of sight glasses  56 . This fuel then passed from sight glasses  56  back into base  38  to continue its flow through passages  52  and  54 . In this way, the fuel being discharged from check valves  44  and  46  could be visible to an operator of engine  10 . For example, when filters  40  were plugged, fuel would have been visible within the sight glass  56  covering valve  46 ; and when manifold  26  was filled and properly pressurized, fuel would have been visible within the sight glass  56  covering valve  44 . Thus, during normal operation, fuel should only have been visible within the one sight glass  56  covering valve  44  (i.e., the sight glass  56  covering valve  46  should normally have been empty, as long as filters  40  were not plugged). However, for reasons stated above, sight glasses  56  are no longer utilized in the disclosed embodiments. 
         [0022]    In the disclosed embodiments, sight glasses  56  have been replaced with metallic valve covers (covers)  58  (shown only in  FIGS. 3 and 4 ). Like the previously used sight glasses  56 , covers  58  may have a dome shape, with a closed end  60  and an open end  62 . A lip  64  may be formed at open end  62  that is received within a machined recess  66  of base  38 . A seal (e.g., a gasket)  68  may be disposed in recess  66  and sandwiched between lip  64  and the internal face of recess  66 . In some embodiments, lip  64  may have a circular-lay roughness of about 100-150 μinch (e.g., about 125 μinch), which may help lip  64  engage with seal  68  to create a fuel-tight interface. 
         [0023]    In the disclosed embodiment, the closed end  60  of each cover  58  is spherical. It is contemplated, however, that the closed end could alternatively be flat, such that cover  58  has more of a cylindrical shape than a domed shape, if desired. Other shapes may also be possible. Cover  58  may be fabricated from a non-corrosive metal, for example stainless steel or aluminum, through a deep-draw process. 
         [0024]    A retainer  70  may pass over the closed end  60  of cover  58  and, together with a fastener  72 , function to press cover  58  against seal  68 . In the embodiment shown in  FIG. 3 , a single retainer  70  is used in conjunction with two covers  58 . Retainer  70  may be formed from a generally C-shaped channel that extends lengthwise past the centers of each cover  58 . In particular, retainer  70  may include a first side  74  connected to base  38  at one edge of cover  58 , a second side  76  connected to base  38  at a second edge opposite first side  74 , and a third side  78  that extends between first and second sides  74 ,  76 . Each of first and second sides  74  and  76  may be oriented generally perpendicular to third side  78 . 
         [0025]    A threaded hole  80  may be formed within third side  78  of retainer  70 , at a location generally aligned with the center of each cover  58 . Fastener  72  may engage threaded hole  80 , such that rotation of fastener  72  extends a shaft portion of fastener  72  inward through retainer  70  and against the center of the corresponding cover  58 . With this configuration, further rotation of fastener  72  may cause fastener  72  to engage the center of cover  58  and urge cover  58  against seal  68 . In some embodiments, cover  58  may be recessed at fastener  72  to receive a tip of fastener  72 . 
         [0026]    In order for retainer  70  to properly anchor fastener  72  and withstand vibrational loading during operation of engine  10 , retainer  70  must have a minimum thickness at third side  78 . In the disclosed embodiment, the thickness of third side  78  may be at least two-times a wall thickness of cover  58 . For example, the thickness of third side  78  may be about 0.25 inch, while the wall thickness of cover  58  may be about 0.12 inch. The three-sided, generally orthogonal shape of retainer  70  may help to increase a stiffness of retainer  70  that further helps retainer  70  to resist damage caused by the vibrational loading. It is contemplated that additional internal ribbing (not shown) could be formed within retainer  70 , if desired, to further increase the stiffness of retainer  70 . 
         [0027]    In some applications, it may be possible for the vibrational loading of engine  10  to cause fasteners  72  to back out of hole  80 . To help fasteners  72  resist this tendency, a cross-hole  82  may be formed through a head portion of each fastener  72 , and a safety wire  84  may simultaneously pass through cross-holes  82  of both fasteners  72 , thereby binding the rotations of fasteners  72  to each other. This binding may inhibit rotation of either fastener  72 . 
         [0028]    First and second sides  74 ,  76  of retainer  70  may connect to base  38  at a plurality of different anchor points. For example, four different ears or tabs  86  may be integrally formed with base  38 , and extend upward from upper surface  48 . Ears  86  may be located outward of first and second sides  74 ,  76 , and arranged in pairs that are each generally aligned with one of covers  58  (e.g., the center of the corresponding cover  58 ). A fastener  88  may pass through each ear  86  to engage retainer  70 . It is contemplated that a vibration damper (e.g., a compressive washer —not shown) may be located at the interface of ear  86  and cover  58 , if desired. In this configuration, retainer  70  may be generally fixed to base  38 , such that little (if any) relative pivoting occurs. 
         [0029]    Two separate retainers  90  are used in place of retainer  70  in the embodiment of  FIG. 4 . Specifically, one retainer  90  is used to retain each cover  58  in place relative to base  38 . Each retainer  90 , like retainer  70 , may be a generally 3-sided structure formed into a C-shaped channel. A length of retainer  90 , however, may be less than one-half of a length of retainer  70 . In addition, each retainer  90  may be connected to base  38  by way of only two ears  86  (one at each of first and second sides  74 ,  76 ). Further, a clearance may exist between upper side  48  of base  38  and lower edges of first and second sides  74 ,  76 . With this configuration, each retainer  90  may be able to pivot independently somewhat about an axis passing through its corresponding fasteners  88 . This pivoting motion may help to center fastener  72  with the center of cover  58 . In addition, in some embodiments, cover  58  may be able to pivot and/or translate somewhat relative to the associated retainer  90  (or  70 ), if desired. 
         [0030]    Because covers  58  are metallic, in one embodiment, they may not be translucent in the same manner that the previously-used sight glasses  56  were transparent. As a result, the proper functioning of fuel system  12  may no longer be visually apparent. For this reason, one or more sensors may be connected to base  38  and in fluid communication with the appropriate passages. For example a first pressure sensor  92  may be connected to base  38  and located in fluid communication with passage  52  (referring to  FIG. 1 ), and a second sensor  94  may be connected to base  38  and located in fluid communication with passage  54 . Each of these sensors  92 ,  94  may be configured to generate signals indicative of fuel pressures within the corresponding covers  58 , the signals then being utilized to determine the air-free and restriction-free status of fuel system  12 . 
       INDUSTRIAL APPLICABILITY 
       [0031]    The disclosed fuel system and filter assembly may be applicable to any combustion engine where reliable and continuous operation is desired. The disclosed fuel system may help to improve reliability and facilitate continuous operation by reducing a risk of component failure within the filter assembly. In particular, the disclosed filter assembly may include valve covers that are robust, and associated retainers and fasteners that have been designed to reduce and/or withstand vibrational loading of the associated engine. 
         [0032]    It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed fuel system and filter assembly. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed fuel system and filter assembly. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.