Patent Publication Number: US-7900932-B2

Title: Valve stem sealing assembly

Description:
TECHNICAL FIELD 
     The invention relates to internal combustion engine valve stem seal assemblies, and more particularly to a valve stem seal assembly that has an elastomeric valve stem seal bonded to a multi-diameter metal retainer. 
     BACKGROUND OF THE INVENTION 
     Those skilled in the art will appreciate the manner in which intake and exhaust valves are employed in cylinder heads of internal combustion engines. In conventional overhead valve internal combustion engines, a pair of valves reciprocates in timed alternation to provide intermittent communication between the intake and exhaust manifolds and a combustion chamber. As is well known, the intake port of a combustion chamber is opened and closed by the reciprocating motion of at least one intake valve. The intake valve permits fuel mixed with air to flow into the combustion chamber. In addition, an internal combustion engine has at least one exhaust valve and associated exhaust port for releasing expended combustion gases into the atmosphere. Lubrication is provided to the upper portions of the valves. Because temperatures in the combustion chamber may approach or exceed 1000 degrees Centigrade, any lubricating oil exposed to these temperatures will vaporize or burn leaving behind deposits that may interfere with the proper sealing of the valves and cause rapid deterioration. Also, excessive burned or unburned oil in the exhaust stream may worsen engine exhaust emissions. Valve stem seal assemblies are used to seal against leakage of oil between each valve guide and its associated valve stem. 
     It is therefore necessary to provide seals around the upper region of the valve stems and along the valve guide. A typical valve stem seal takes the form of a cylinder partially closed at one end by the valve seal. The cylindrical region seats about the valve guide to maintain the valve seal stationary. An upper region of the valve stem is surrounded by the valve seal when the valve stem is fully inserted into the valve seal assembly. 
     However, known constructions where the valve stem seals seat about the valve guide, require a great deal of material to extend along the height of the valve guide. Additional material translates into higher costs. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is directed to an improved valve stem seal assembly for sealing a valve stem, using minimal material, and thus being cost effective without sacrificing sealing capabilities. The valve stem seal assembly of the present invention includes a retainer and a sealing element disposed within the retainer. The retainer includes an upper portion, a lower portion and a radially extending flange. The flange is connected to the lower portion. The lower portion is connected to the upper portion by an inwardly extending step. The diameter of the upper portion is less than the diameter of the lower portion. 
     The sealing element is annular and constructed of an elastomeric material. The sealing element further includes at least one sealing lip that engages an upper portion of a valve guide. The sealing lip is formed by a downwardly and inwardly curving first section of the sealing member that extends from a top surface of the sealing member such that the sealing lip is spaced a predetermined distance from the top of the sealing member. The sealing lip further includes a generally planar portion that extends a predetermined length so as to provide a gripping surface. An optional second sealing lip may also be included. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross section of integral bonded top seal for a valve stem in accordance with the present invention; 
         FIG. 2  is an enlarged view of a top portion of the seal taken from section  2  of  FIG. 1 ; and 
         FIG. 3  is an enlarged view of a bottom portion of the seal taken from section  3  of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIG. 1 , a valve stem seal assembly  10  incorporates an elastomeric valve sealing element of valve stem seal  12  that is assembled to a generally cylindrical retainer  14 . Sealing element  12  may be affixed to retainer  14  by bonding or the like. Although the invention contemplates that retainer  14  is formed of metal, other materials may be suitable depending on the harshness of the particular environment. For example, some glass-filed nylons or other plastics may be suitable for some engine environments, such that retainer  14  may suitably formed of plastic materials. 
     Retainer  14  includes a lower cylindrical portion  16  and an upper cylindrical portion  18 . Upper and lower cylindrical portions  16 ,  18  are connected together by a step  20  that extends inwardly from lower cylindrical portion  16  such that upper cylindrical portion  18  has a diameter d that is less than the diameter D of lower cylindrical portion  16 . Upper cylindrical portion  18  has an opening  22  therein. Retainer  14  further includes a radially extending flange  23  that is preferably integral with the lower cylindrical portion  16 . 
     Sealing element  12  has a generally cylindrical body that includes interior surface  24  and an exterior surface  26 . Exterior surface  26  is generally planar and is attached to an interior wall  28  of upper cylindrical portion  18  of retainer  14 . Interior surface  24  includes an oil sealing lip  30  that is adapted for contacting a cylindrical surface of a valve stem S. Oil sealing lip  30  is formed by a first section  32  of sealing element  12  that extends downwardly and curves inwardly toward the center of valve stem seal assembly  10 . First section  32  serves to space oil sealing lip  30  a predetermined distance from the top surface  34  of sealing element  12 . In addition, the curve of the first section  32  operates to create a reservoir to collect oil. Oil sealing lip  30  has a generally planar portion  36 . Planar portion  36  is oriented so as to be generally vertical, as shown in  FIG. 2 , and has a predetermined length L, so as to provide a gripping surface for contacting the valve stem S. 
     Sealing element  12  may further includes a second oil sealing lip  38  that is longitudinally spaced from oil sealing lip  30  adapted to contact the valve stem S. Second oil sealing lip  38  is formed by a connecting portion  40  that extends downwardly and outwardly from first oil sealing lip  30 . Second oil sealing lip  38  is spaced outwardly from oil sealing lip  30  and includes a contact surface  42  that is angled. Contact surface  42  is offset from a bottom portion  44  of exterior surface  26  of sealing element  12 . 
     Those skilled in the art will appreciate that second oil sealing lip  38  is not required in all applications. Moreover, those skilled in the art will appreciate that oil sealing lip  30  (and second oil sealing lip  38 ) are sized to assure proper lubrication and consequent avoidance of premature damage to the oil sealing lip  30  (and second oil sealing lip  38 ) due to friction, as well as any friction scouring of the valve stem. 
     In accordance with one aspect of the invention, an oily environment exists above the cylinder head deck, or one subject to “splash and spray oil” as described in the art. As a result, valve stem assembly  10  is needed to assure that oil does not migrate into the area under the valve head of a valve stem and into the combustion chamber. 
     One known migration path that oil may travel into the combustion chamber extends between the valve stem and the sealing element  12 . In accordance with the invention, oil sealing lip  30  is the primary gate for deterring oil travel along this migration path. The curved first section  32  of the sealing element  12  also serves to create a reservoir to collect and evaporate oil. Second oil scaling lip  38  may be included to prevent oil flow migration past the top surface of the valve guide  46 , and down along a path between the valve stem and the valve stem seal assembly  10 . 
     It should be understood that the aforementioned and other various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby.