Abstract:
An engine includes a cylinder head at least partially defining a valve seat pocket. A valve seat is located proximate to the cylinder head to at least partially define the valve seat pocket. A pocket filler is located between the valve seat and the pocket insert such that the pocket filler occupies a substantial portion of the valve seat pocket. A pocket insert is attached to the cylinder head proximate to the valve seat pocket, such that the pocket insert lines at least a portion of the valve seat pocket.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 61/186,952, filed Jun. 15, 2009, which is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates, generally, to an engine, and more specifically, to an arrangement for preventing corrosion of the cylinder head. 
     BACKGROUND OF THE INVENTION 
     Cylinder heads commonly include valve seats to provide a seating surface for the engine valves. The valve seats are typically inserts that are positioned within the cylinder head. Valve seats are typically manufactured from materials that are wear-resistant and heat-resistant. Often the valve seat is manufactured from a different material than the cylinder head. For example, aluminum engine cylinder heads commonly have steel valve seats. 
     SUMMARY OF THE INVENTION 
     An engine includes a cylinder head, a valve seat, and a pocket filler. The cylinder head at least partially defines a valve opening configured to receive a valve, a combustion chamber, and a stepped portion disposed between the valve opening and the combustion chamber. The valve seat may be disposed within the stepped portion and may be configured to make sealing contact with the valve to fluidly isolate the valve opening from the combustion chamber. 
     The pocket filler may be disposed within the stepped portion and between the cylinder head and the valve seat. The pocket filler may be formed from an elastic material configured to permit relative movement between the valve seat and the cylinder head. The cylinder head, the valve seat, and the pocket filler may collectively define a first valve seat pocket and a second valve seat pocket. The first valve seat pocket may be in fluid communication with the valve opening when sealing contact is established between the valve seat and the valve. Likewise, the second valve seat pocket may be in fluid communication with the combustion chamber when sealing contact is established between the valve seat and the valve. 
     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 
         FIG. 1  is a schematic cross-sectional illustration of an engine showing an cylinder head and valve seat. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the Figures, wherein like reference numbers refer to the same or similar components throughout the several views,  FIG. 1  schematically illustrates an engine  10  having a cylinder head  12  that at least partially defines a valve opening  14  and a combustion chamber  15 . A valve  16  is located within the valve opening  14  and includes a valve head  18 . The cylinder head  12  also defines a stepped portion  20  for aligning a valve seat  22 . The cylinder head  12  is preferably an aluminum alloy and the valve seat  22  is preferably a steel alloy. The valve seat  22  may be disposed within the stepped portion  20  and may be positioned to provide a seating surface  24  for the valve head  18  during operation of the engine  10 . Contact between the valve head  18  and the seating surface  24  of the valve seat  22  may be operative to fluidly isolate the valve opening  14  from the combustion chamber  15 . 
     A valve seat pocket filler  28  may be disposed within the stepped portion  20  between the cylinder head  12  and the valve seat  22 . The valve seat pocket filler  28  is formed in the general shape of the stepped portion  20  and manufactured from a material that inhibits corrosion of aluminum. Alternatively, the valve seat pocket filler  28  may have a common shape, such as an O-ring having a circular cross-sectional shape. 
     As illustrated in  FIG. 1 , the cylinder head  12 , the valve seat  22 , and the pocket filler  28  may define a first valve seat pocket  25  and may define a second valve seat pocket  26 . The first valve seat pocket  25  may be in fluid communication with the valve opening  14  when sealing contact is established between the valve seat  22  and the valve head  18 . In a similar manner, the second valve seat pocket  26  may be in fluid communication with the combustion chamber  15  when sealing contact is established between the valve seat  22  and the valve head  18 . 
     The valve seat pocket filler  28  is preferably a rubber-based material which is chemically stable Likewise, the valve seat pocket filler  28  may be formed from an elastic material to accommodate movement of the valve seat  22  relative to the cylinder head  12 . For example, the valve seat pocket filler  28  may be formed from a fluorelastomer, a fluoropolymer (e.g., Polytetrafluoroethylene), or a phenolic material. 
     The valve seat pocket filler  28  may be larger than the stepped portion  20  of the cylinder head  12 , such that the valve seat pocket filler  28  is under compression when the valve head  18  is resting on the valve seat  22 . The valve seat pocket filler  28  may substantially occupy the stepped portion  20  of the cylinder head  12  to prevent the stepped portion  20  from filling with engine fuel. Therefore, the valve seat pocket filler  28  prevents fuel from becoming trapped in the stepped portion  20  in a manner where it cannot be easily evacuated, and also prevents corrosion of the cylinder head  12 , which may result when the engine fuel is a bio-fuel and the cylinder head  12  is formed of an aluminum alloy. The valve seat pocket filler  28  may also be bonded in place to assist the valve seat pocket filler  28  in filling the stepped portion  20 . 
     The valve seat pocket filler  28  may also have a coating  30  of material applied to the surface which is known to have an inhibiting effect on the corrosion of aluminum. For example, the material for the coating  30  may be colloids such as tragacanth, acacia, agar-agar, glue, dextrin, or gelatin. Additional materials known to have an inhibiting effect on the corrosion of aluminum may also be mixed with the colloids for the coating  30  of the valve seat pocket filler  28 . For example, aldehydes, sebacic axis, phenyl semicarbazide derivatives, amines, cerium dibuytlphosphates, citric acid, azodyes, anion, pyridine, surfactants, Vernonia amygdalina, Halide ions, 2-acetylphenothiazine, methyl red, TSC (Thiosemicarbazone), Lawsonia extract (Henna, aqueous extract of Rosmarinus officinalis L, methylene blue, Hibiscus subdariffa (Karkode) extract, molasses, caffeine, 4-(2′-amino-5′-methylphenylazo) antipyrine, Zenthoxylum alatum plant, extract of the leaves of Nypa fruticans (Wurmb), or vanadates may be mixed with the colloids to form the coating  30 . Therefore, the valve seat pocket filler  28  may release inhibitors to prevent corrosion of the cylinder head  12  proximate to the stepped portion  20 . 
     A pocket insert  32  may also be secured to the cylinder head  12  at the stepped portion  20 . The pocket insert  32  provides a liner for the cylinder head  12  along the stepped portion  20  and assists in preventing corrosion of the valve seat  22  and the cylinder head  12  adjacent the first and second valve seat pockets  25 ,  26 . In one embodiment, the pocket insert  32  is a steel insert that is preformed and secured to the cylinder head  12  at the stepped portion  20  during casting of the cylinder head  12 . That is, the pocket insert  32  may be placed in the mold for the cylinder head  12  such that the cylinder head  12  is formed around the pocket insert  32  during casting. 
     The pocket insert  32  may also include a first layer  34  formed of a first material and a second layer  36  formed of a second material. The first and the second materials may be selected to increase the corrosion protection of the cylinder head  12  at the first and second valve seat pockets  25 ,  26 . The first layer  34  may be adjacent the valve seat  22  and the second layer  36  may be adjacent the cylinder head  12 . Alternately, the second layer  36  may be a cladding applied around the first layer  34 . In either of these embodiments, the first layer  34  may be steel to assist in preventing corrosion and the second layer may be aluminum to improve the bond that forms between the cylinder head  12  and the pocket insert  32  during casting of the cylinder head  12 . Alternately, there may be tabs located on the pocket insert  32  to mechanically bond the pocket insert  32  to the cylinder head  12  during casting of the cylinder head  12 . 
     The valve seat pocket filler  28  can be secured to the valve seat  22  or to the cylinder head  12  by attachment to the pocket insert  32 . Adhesive material may be used to secure the valve seat pocket filler  28  to the valve seat  22  or the pocket insert  32 . 
     The valve seat  22  includes a first valve seat coating  38 . The first valve seat coating  38  is preferably a ceramic coating. The first valve seat coating  38  may be created by applying an aluminum coating to the surface of the valve seat  22  such as by an Alumiplate™ technique, as is known to those skilled in the art. The aluminum coating is then converted into a ceramic coating such as through an electro-deposition technique like Anodine EC2™, as is known to those skilled in the art. The resulting first valve seat coating  38  has high corrosion resistance and high wear resistance. By first applying an aluminum coating and then converting the aluminum to ceramic, there is a higher level of adhesion between the first valve seat  22  and the first valve seat coating  38 . The valve seat coating  38  prevents fretting wear on the valve seat  22  during operation of the engine  10   
     The valve seat  22  may also include a second valve seat coating  40 . The second valve seat coating  40  may be a material applied to the surface of the first valve seat coating  38 , which is known to have an inhibiting effect on the corrosion of aluminum. For example, aldehydes, sebacic axis, phenyl semicarbazide derivatives, amines, cerium dibuytlphosphates, citric acid, azodyes, anion, pyridine, surfactants, or vanadates, etc. may be mixed with the a base material to form the second valve seat coating  40 . The base material for the second valve seat coating  40  may be a hard material such as ceramic. Alternatively, the inhibitor may be directly incorporated into the first valve seat coating  38 . The second valve seat coating  40  may be formed about the entire circumference of the valve seat  22 , as shown, or may be applied to areas where the inhibitor may have the most effect, such as adjacent to the first and second valve seat pockets  25 ,  26 . Therefore, the valve seat pocket seat  22  may release inhibitors to prevent corrosion of the engine bock head  12  proximate to the first and second valve seat pockets  25 ,  26 . 
     In the embodiment described above, the valve seat pocket filler  28 , the pocket insert  30 , first the valve seat coating  38 , and the second valve seat coating  40  are all used within the engine  10 . However, each of these elements may be utilized individually or in combination with one another to promote resistance to corrosion within the engine  10 . 
     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.