Abstract:
An anti-drainback apparatus for an oil filter assembly includes an anti-drainback valve formed from an elastomeric material. The anti-drainback valve is operable to selectively restrict reverse flow through the oil filter assembly. The anti-drainback valve is generally frusta-conical in shape and includes at least one relief valve to selectively open in the presence of a predetermined pressure to allow reverse flow through the oil filter assembly. An oil filter assembly is also provided incorporating the disclosed anti-drainback valve.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an anti-drainback valve for use within an oil filter. 
       BACKGROUND OF THE INVENTION 
       [0002]    Liquid filters, such as an engine oil filter, may employ an anti-drainback valve which operates to prevent oil from draining from the passages within the engine during shut-down thereby providing a measure of protection against noise emitted by components, such as the valvetrain components, during re-start of the engine. Newly manufactured engines are generally provided with oil through one of the passages defined by the engine (i.e. a fill passage) in order to lubricate interfaces and provide oil to the engine&#39;s oil pump for oil pump priming prior to starting the engine. The fill passage tends to be located downstream from the oil filter, while the oil pump tends to be located upstream from the oil filter and, as such, the anti-drainback valve within the oil filter tends to restrict oil flow to the oil pump thereby increasing the time required to prime the oil pump. Consequently, a filter may be installed without an anti-drainback valve to allow an adequate amount of oil to reach the oil pump to enhance oil pump priming during the filling operation. 
       SUMMARY OF THE INVENTION 
       [0003]    An anti-drainback apparatus for an oil filter assembly is provided. The anti-drainback apparatus includes an anti-drainback valve formed from an elastomeric material and operable to selectively restrict reverse flow through the oil filter assembly. The anti-drainback valve is generally frustoconical in shape and includes at least one relief valve to selectively open in the presence of a predetermined pressure to allow reverse flow through the oil filter assembly. 
         [0004]    An oil filter assembly for an engine is also provided. The engine defines first and second oil passages in communication with the oil filter assembly. The oil filter assembly includes an anti-drainback valve disposed within the oil filter assembly and operable to substantially restrict the flow of oil from the first oil passage when the pressure differential between the first oil passage and second oil passage is below a predetermined value. The anti-drainback valve includes at least one relief valve operable to selectively open to allow the flow of oil from the first oil passage when the pressure differential between the first oil passage and second oil passage is greater than or equal to the predetermined value. 
         [0005]    The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a schematic sectional view of an oil filter assembly incorporating an anti-drainback valve; and 
           [0007]      FIG. 2  is a schematic bottom view of the anti-drainback valve of  FIG. 1  illustrating a plurality relief valves incorporated within the anti-drainback valve. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0008]    Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures,  FIG. 1  shows an oil filter  10  for filtering the lubricating oil used in an engine  12 . The engine  12  includes a reservoir  11 , such as an oil pan, configured to contain a predetermined amount of oil  15 . The oil filter  10  comprises a cylindrical canister  13  having a closed end  14  and an open end  16 . The open end  16  is partially closed by a closure plate  18  having a central fluid outlet  20  and a plurality of fluid inlets  22 , one of which is shown in  FIG. 1 , that are radially arranged around the outlet  20 . The outlet  20  is threaded to engage a pipe  23  extending from an oil passage  24  defined by the engine  12 , while the inlets  22  are open to an oil passage such as a main oil gallery  25  defined by the engine  12  and disposed radially inward from a generally circular gasket  26 . The gasket  26  is mounted on a plate  27  whose outer periphery is rolled together with the open end  16  of the canister  13  to be thereby secured to the canister  13  and also retain the closure plate  18  against outward movement. A positive displacement oil pump  29  is provided in communication with the main oil gallery  25  and is operable to communicate oil  15 , under pressure, from the reservoir  11  to the main oil gallery  25  for subsequent introduction to the oil filter  10 . 
         [0009]    A cylindrical filter cartridge  28  is positioned in the canister  13  and includes a suitable filtering element  30  of suitable filter media, such as a pleated paper type media. The outer side of the filtering element  30  is spaced radially inward from the canister&#39;s cylindrical wall so that oil entering through the inlets  22  may flow to the outside of the filter cartridge  28  and then radially inwardly through the filtering element  30  to a hollow axially extending center portion  31 , defined by the filter cartridge  28 , and thence to the return pipe  23  where it is communicated to the main oil gallery  25 . The filter cartridge  28  further includes end cover plates  32  and  34  which fit over and are sealingly secured to the opposite ends of the filtering element  30  to provide support therefor as well as provision for holding the filter cartridge  28  in position within the canister  13 . The end cover  32  has a central opening  33  through which filtered oil  15  passes to the outlet  20  while the other end cover  34  has no openings therethrough and is engageable with the canister&#39;s closed end  14 . A bypass valve (not shown), such as a spring loaded poppet valve, may be provided within the end cover  34  to allow oil  15  to bypass the filtering element  30  should the filtering element  30  become overly restrictive, such as by increased fluid viscosity and/or contaminate accumulation. 
         [0010]    To prevent oil  15  from draining through the inlets  22  caused by insufficient pressure within the main oil gallery  25  due to, for example, discontinuance of the operation of the oil pump  29 , there is provided an anti-drainback valve  36  formed from an elastomeric material, such as rubber, which is located between the end cover  32  of the filter cartridge  28  and the closure plate  18 . In such an arrangement, one end of the filter cartridge  28  is held against the canister&#39;s closed end  14  and the anti-drainback valve  36  is sealingly engaged between the end cover  32  and the closure plate  18 . 
         [0011]    The anti-drainback valve  36  has an annular body  38  arrangeable between the closure plate  18  and the filter cartridge&#39;s end cover  32 . The body  38  has a central opening  40  through which the oil  15  can pass to the outlet  20 . The closure plate  18  is provided with an inwardly extending annular flange or collar  42  about the outlet  20  which fits in the opening  40  to thus coaxially locate the anti-drainback valve  36  with the closure plate  18 . The body  38  additionally has an axially extending annular collar  44  in engagement with the central opening  33  of the end cover  32  of the filter cartridge  28  to provide a coaxial relationship between the anti-drainback valve  36  and the filter cartridge  28 . In addition, the annular collar  44  has a radially inwardly extending annular rib  48  for sealingly engaging a smooth shoulder  49  that is formed on the end of the pipe  23 . 
         [0012]    Further describing the structure of the anti-drainback valve  36 , the body  38  has a flexible, radially and axially outwardly, annular valve portion  50  of frustoconical shape with a lip  52  on its outer perimeter. The lip  52 , in the absence of oil pressure within the main oil gallery  25 , normally seats on the closure plate  18 , radially outward of the inlets  22 . Thereby preventing oil  15  contained within the oil filter  10  and hence the oil passage  24  from draining through the inlets  22  and subsequently siphoned to the sump  11 . The valve portion  50  diverges axially outward and is flexible to lift off the closure plate  18  in response to pressure at the inlets  22  resulting from operation of the oil pump  29  to permit flow to the filter cartridge  28 . 
         [0013]    Referring to  FIG. 2  there is shown a bottom view of the anti-drainback valve  36  illustrating a plurality relief valves  56  formed as slits or cuts defined therein and extending generally radially outwardly along the annular valve portion  50 . The slits forming relief valves  56  may be of other shapes such as star-shapes, cross-shapes, or slits extending generally circumferentially. Those skilled in the art will recognize that any cut or slit configuration provided on the anti-drainback valve  56  that opens in response to a pressure differential may be used while remaining within the scope of that which is claimed. Additionally, the relief valves  56  may be molded features formed on the annular valve portion  50 , such as one-way flapper valves. The relief valves  56  extend completely through the annular valve portion  50 . As shown in  FIG. 2 , six relief valves  56  are equally spaced about the circumference of the annular valve portion  50 ; however, those skilled in the art will recognize that greater or fewer relief valves  56  and alternate spacing schemes may be employed while remaining within the scope of that which is claimed. The relief valves  56  are selectively openable in response to a predetermined pressure differential between the oil passage  24  and the main oil gallery  25 , shown in  FIG. 1 . 
         [0014]    The operation of the oil filter  10  will be discussed in greater detail with reference to  FIGS. 1 and 2 . During operation of the engine  12 , the oil pump  29  operates to provide oil  15 , under pressure, to the main oil gallery  25  where it is subsequently introduced to the inlets  22 . The oil  15  traverses the inlets  22  and biases the annular valve portion  50  of the anti-drainback valve  36  away from the closure plate  18  such that the oil  15  is allowed to flow into the canister  13 . The oil  15  is forced though the filter cartridge  28  where contaminates, such as particles, are removed prior to introduction to the center portion  31  where the oil  15  is introduced to the oil passage  24  via the pipe  23  to enable reliable operation of the engine  12 . Upon shut-down of the engine  12 , the operation of the oil pump  29  is discontinued such that the pressure within the main oil gallery  25  is essentially zero. As a result, the oil  15  remaining within the oil passage  24  and the oil filter  10  will bias the annular valve portion  50  of the anti-drainback valve  36  against the closure plate  18  thereby blocking the backflow or reverse flow of oil  15  through the inlets  22 . This is desirable since an amount of oil  15  remains within the engine  12  to provide lubrication and hydraulic control to components, such as valvetrain components, upon restart of the engine  12 . 
         [0015]    In some instances, such as when filling a newly manufactured engine with oil  15 , it may be beneficial to fill the engine  12  with oil under pressure through a fill passage, not shown, in communication with the oil passage  24  to provide an amount of oil  15  to components of the engine  12  as well as providing oil  15  to aid in priming the oil pump  29 . By providing pressurized oil  15  to the passage  24 , in the absence of pressure within the main oil gallery  25 , oil  15  is forced from the oil passage  24  to the center portion  31  of the filter cartridge  28 . The oil  15  is forced through the filtering element  30  where it engages the anti-drainback valve  36 . As the pressure of the oil  15  acting on the annular valve portion  50  of the anti-drainback valve  36  is increase above a predetermined level, the oil  15  will force the relief valves  56  to open thereby allowing oil  15  to flow from the canister  13 , through the inlets  22 , and into the main oil gallery  25 . The oil  15  is subsequently introduced to the oil pump  29  where it promotes the priming of the oil pump  29 . The predetermined pressure level is greater than the head pressure exerted on the anti-drainback valve  36  at engine shut-down; therefore, the anti-drainback valve  36  is still effective to maintain a quantity of oil  15  within the engine  12  to enhance operation of the engine  12  and re-start. Additionally, by providing relief valves  56  within the anti-drainback valve  36 , the need to install an oil filter having no anti-drainback valve  36  to enable priming of the oil pump  29  during an engine assembly plant fill operation is obviated. 
         [0016]    While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.