Abstract:
A gasket having a layer including at least one combustion opening and a wave area located on the layer is disclosed. The wave area includes a first wave and a second wave. The first wave is proximate the combustion opening. A flat portion near the second wave includes a first end and a second end. A full bead is located next to the second end of the flat portion whereby a lower surface of the flat portion is above the lower projecting surfaces of the wave area.

Description:
TECHNICAL FIELD 
     The embodiments of the invention described herein are generally directed to sealing gaskets. 
     BACKGROUND 
     Gaskets made of a metal material have been used to seal a joint where a cylinder head interfaces with a cylinder block of an engine. There are openings in the gasket which cooperate with the combustion chambers, water passages and oil passages in the engine. These gasket openings typically have a structure to enhance sealing around the openings. 
     Cylinder head gaskets are the most sophisticated type of gaskets. When first starting an engine in cold weather, parts near the combustion chamber might be subfreezing. Then, after only a few minutes of engine operation, these same parts may reach 400 degrees Fahrenheit. The inner edges of the cylinder head gaskets are exposed to combustion flame temperatures from 2,000 to 3,000 degrees Fahrenheit. 
     Pressures inside the combustion chamber also vary tremendously. On the intake stroke, a vacuum or low pressure exists in the cylinder. Then after combustion, pressure peaks of approximately 1,000 pounds per square inch (psi) occur. This extreme change from suction to high pressure happens in a fraction of a second. Cylinder head gaskets, under these conditions must also provide the following: seal intake stroke vacuum, combustion pressure, and the flame in the combustion chamber; prevent coolant leakage, resist rust, corrosion and, in many cases, meter coolant flow; seal oil passages through the engine block and engine head while resisting chemical action; allow for lateral and vertical head movement as the engine heats and cools; be flexible enough to seal minor surface warpage while being stiff enough to maintain adequate gasket compression; fill small machining marks that could lead to serious gasket leakage failure; and withstand forces produced by engine vibration. 
     Known ways to enhance gasket opening sealing includes the use of metal plates having wave beads. However, the gaskets with wave beads provide uneven sealing pressure patterns and shift the heavy load away from the desired wave area. When the heavy load is shifted away from the desired wave area onto a flat portion of the gasket, the sealing pressure is decreased. Moreover, this localized excessive loading accelerates the cracking failure at the flat portion of the gasket. 
     Therefore, there is a need for a cylinder head gasket that creates an even sealing pressure pattern at the wave area. It would be desirable to provide load shifting that reduces premature cracking failure by properly distributing the load along the wave area so that the load is not concentrated at the flat portion. The load should be distributed evenly throughout the entire region of the seal where the load is desired. 
     BRIEF SUMMARY 
     The embodiments described herein are directed to a gasket having a metal layer including at least one combustion opening and a wave area located on the layer. The wave area includes a first wave and a second wave. The first wave is proximate the combustion opening. A flat portion near the second wave includes a first end and a second end. A full bead is located next to the second end of the flat portion whereby a lower surface of the flat portion is above the lower projecting surfaces of the wave area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and inventive aspects of an embodiment described herein will become more apparent upon reading the following detailed description, claims, and drawings, of which the following is a brief description: 
         FIG. 1  is a partial plan view of a metal gasket according to one embodiment; 
         FIG. 2  is a sectional view along section  2 - 2  in  FIG. 1  showing an embodiment of a single layer gasket having a wave area and a full bead; and 
         FIG. 3  is a sectional view along section  2 - 2  in  FIG. 1  showing an embodiment of a multi-layer gasket having an active layer and a wave bead layer. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, an illustrative embodiment is shown in detail. Although the drawings represent an embodiment, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain the innovative aspects of the embodiment. Further, the embodiments described herein are not intended to be exhaustive or otherwise limit or restrict the invention to the precise form and configuration shown in the drawings and disclosed in the following detailed description. 
     Referring to  FIGS. 1 and 2 , a cylinder head  6  and a cylinder block  7  of an internal-combustion engine have opposed surfaces  8 ,  9  that require proper sealing. A metal gasket  10  is adapted to be held between the cylinder head  6  and the cylinder block  7  and seal the clearances between the opposed surfaces  8 ,  9  thereof. The metal gasket  10  is applied to a multi-cylinder engine corresponding to cylinder bores (not shown) formed in the cylinder block. A plurality of cylinder bore holes  12  or combustion chamber holes are formed side by side. The metal gasket  10  has various kinds of holes including water holes (not shown), oil holes (not shown), and bolt holes  14  around the cylinder bore holes  12 . 
     Now referring to  FIG. 2 , the metal gasket  10  includes a wave area  18  disposed proximate a cylinder bore edge  16 . The wave area  18  includes at least two waves that may be formed in a single sheet metal layer  20 . The metal gasket  10  further includes at least one full bead  22 . In one embodiment, the wave area  18  may include a plurality of undulating waves. However, any full bead may be used for full bead  22  and any plurality of waves may be used for the wave area  18 . The single sheet metal layer  20  may also be incorporated into a multi-layered steel (MLS) gasket (not shown) having a stopper layer and an active layer. An embodiment of the metal gasket  10  may be formed from any metal but preferably from a 301 stainless steel having its thickness determined by the user as required. 
     Each cylinder bore hole  12  is sealed off to prevent combustion gasses from escaping by the wave area  18  and the full bead  22  surrounding the cylinder bore. The wave area  18  provides cross-sectionally projecting waves, which extend along the circumference of each cylinder bore hole  12 . A flat portion  24  is disposed between the wave area  18  and the full bead  22  having a flat portion lower surface  25 . The wave area  18  is formed so that a projecting upper first surface  26  of a first wave  28  and a projecting upper second surface  30  of a second wave  32  are generally planer. Furthermore, the flat portion  24  is raised so that the flat portion lower surface  25  is initially about 10-100 microns above a lower first surface  29  of the first wave  28  and a lower second surface  31  of the second wave  32 . A third wave  34  is shown positioned between the first and the second waves  28 ,  32 . However, a plurality of waves may be included between the first wave  28  and the second wave  32 . In a second embodiment, the upper first surface  26  of the first wave  28  projects upwardly from the projecting upper second surface  30  of the second wave  32 . 
     During operation of the engine, the metal gasket  10  is set between the opposed surfaces of the cylinder head  8  and the cylinder block  9  and tightened by a clamping mechanism. In one embodiment, the clamping mechanism includes bolts, however, other suitable clamping mechanisms may be used. With the metal gasket  10  installed, the full bead  22  and the wave area  18  elastically deform in a spring-like fashion to the metal layer  20 . The wave area  18  creates a uniform sealing pressure pattern at the wave area  18  having the flat portion  24  raised so that the flat portion lower surface  25  is initially about 10-100 microns above the lower first surface  29  of the first wave  28  and the lower second surface  31  of the second wave  32 . This load shifting reduces premature cracking failure at the flat portion  24  by properly distributing the load along the wave area  18  so that the load is not concentrated at the flat portion  24  between the wave area  18  and the full bead  22 . Instead, the load is distributed evenly throughout the entire region of the wave area  18  where the load is desired. 
     Referring to  FIG. 3 , an embodiment of the metal gasket  10  is shown including an active layer  40  forming a multi-layered gasket. The gasket  10  includes two metal layers  20 ,  40  mounted atop the other. However, any number of layers may be used. In the illustrated embodiment, lower metal layer  20  includes the same general construction and seal arrangement as the single layer metal gasket  10  described above. 
     The upper metal layer  40  includes a bead  42  and generally may have additional beads provided. The upper metal layer  40  may be formed from steel, stainless steel, or the like. The multi-layer gasket is constructed such that an upper end  44  is generally aligned with a lower end  46  proximate the cylinder bore edge  16 . A lower flat surface  48  of the upper metal layer  40  is generally in sealing contact with at least the upper first surface  26  of the first wave  28 . Beads  22  and  42  are generally aligned so that a lower surface  50  of the upper metal layer  40  is in operational communication with an upper surface  52  of the lower metal layer  20 . At least a portion of an active layer upper surface  54  is in contact with the cylinder head surface  8  and at least a portion of a wave bead layer lower surface  56  is in contact with the cylinder block surface  9 . The shape of the beads may be selected from any commonly know geometric shape and may be varied to achieve uniform sealing stresses in both layers. 
     To control seal operating thickness, one or more design parameters may be varied, including, but not limited to, bead width, bead depth, bead shape, and plate thickness. Such control provides the ability to easily customize the metal gasket  10  for a particular gasket application. The metal gasket  10  may also include an elastomeric coating having a thickness between 0.001 millimeters and 0.05 millimeters. However, thicker coatings may be used. The coating is a Dana Corporation F50 coating; however, other like coatings may be used. The coating performs a sealing function. 
     The embodiments herein have been particularly shown and described, which are merely illustrative of the best mode for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. 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. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.