Patent Publication Number: US-2015069718-A1

Title: Metal gasket assembly

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to gaskets and more particularly to metal gaskets having a functional layer and an embossment bead. 
     2. Related Art 
     In establishing a gas tight seal between two members to be clamped together, such as a cylinder head and an engine block, it is common to use a cylinder head gasket having one or more layers. Generally, at least one of the layers is a functional layer which has an embossment bead that deforms elastically when the metal gasket is sandwiched between the cylinder head and the engine block, thereby establishing a gas-tight seal. It is important that this gas-tight seal is maintained even during relative movement of the members being sealed, e.g. lifting of the cylinder head away from the engine block during operation of the engine to keep combustion gasses from escaping the combustion chambers. One approach that some gasket manufacturers have taken to ensure that the gas-tight seal is maintained during operation of the engine is to increase the thickness of the gasket in certain locations, thereby increasing the biasing force by the combustion bead against the engine block or the cylinder head. Another approach that some gasket manufacturers have taken is to include one or more compression limiters adjacent the embossment beads of their gaskets to restrict full flattening of the embossment bead between the cylinder head and the engine block. 
     Yet another alternate approach is to form the embossment bead with an indentation formed at its apex so that the embossment bead is M or W shaped when viewed in cross-section. At least one known gasket has such an M or W shaped embossment bead that has a height of between 0.04 to 0.15 mm when in an uncompressed state. The indentation in the embossment bead of this type of gasket functions as a compression limiter to restrict full flattening of the embossment bead, i.e. the stopper feature is built into the embossment bead. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention includes a metal gasket for establishing a seal between a first member, such as a cylinder head, and a second member, such as an engine block. The metal gasket includes at least one functional layer with an inner periphery that surrounds an opening and has a generally flat portion. The functional layer additionally has an embossment bead which is spaced from the inner periphery and surrounds the opening and extends in a first direction away from the generally flat portion. The embossment bead on the functional layer includes an indentation which extends in a second direction opposite of the first direction for providing the embossment bead with three points of contact as viewed in cross-section when compressed between the first and second members. The embossment bead also has a bead height that is greater than 0.15 mm and is no greater than 0.30 mm when in an uncompressed state. This particular range in the bead height is advantageous because it provides optimum sealing performance with reduced forming stresses and increased fatigue resistance as compared to shorter embossment beads with similar shapes. 
     Another aspect of the present invention provides for a metal gasket for establishing a seal between a first member, such as a cylinder head, and a second member, such as an engine block. The metal gasket includes at least one functional layer which has an inner periphery that surrounds an opening. The functional layer also has a generally flat portion and an embossment bead which is spaced from the inner periphery, surrounds the opening and extends in a first direction away from the generally flat portion. The embossment bead on the functional layer further includes an indentation which extends in a second direction that is opposite of the first direction for providing the embossment bead with three points of contact as viewed in cross-section when compressed between the first and second members. The metal gasket further includes a stopper feature which is separate from and adjacent to the embossment bead for restricting full flattening of the embossment bead between the first and second members. As such, the embossment bead with the indentation may be configured for optimizing the seal between the first and second member while the stopper feature restricts the full flattening of the embossment beads, i.e. the sealing performance of the metal gasket is higher than gaskets with U-shaped embossment beads or gaskets with embossment beads that have a built in stopper feature. 
     Yet another aspect of the present invention is a multi-layer gasket assembly for establishing a seal between a first member (such as a cylinder head) and a second member (such as an engine block). The multi-layer gasket assembly includes at least one functional layer having an inner periphery which surrounds an opening and has a generally flat portion. An embossment bead which is spaced from the inner periphery surrounds the opening and extends in a first direction away from the generally flat section. The embossment bead on the functional layer includes an indentation which extends in a second direction that is opposite of the first direction. The multi-layer gasket assembly further includes a distance layer which overlies the functional layer and a stopper which is sandwiched between the distance layer and the functional layer and extends radially across the embossment bead. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is a partially exploded view of an internal combustion engine with a first exemplary metal gasket positioned between a cylinder head and an engine block; 
         FIG. 2  is a cross-sectional and fragmentary view show of the first exemplary embodiment of the metal gasket in an uncompressed condition; 
         FIG. 3  is a cross-sectional and fragmentary view of the first exemplary embodiment of the metal gasket in a compressed condition between the cylinder head and the engine block; 
         FIG. 4  is a top view of the first exemplary embodiment of the metal gasket; 
         FIG. 5  is a cross-sectional and fragmentary view of a second exemplary embodiment of the metal gasket in an uncompressed condition between the cylinder head and the engine block; and 
         FIG. 6  is a cross-sectional and fragmentary view of an exemplary multi-layer gasket assembly. 
     
    
    
     DESCRIPTION OF THE ENABLING EMBODIMENT 
     Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a first exemplary embodiment of a metal gasket  20  for establishing a seal between a first member  22  and a second member  24  is generally shown in  FIG. 1 . In the exemplary embodiment, the metal gasket  20  is a cylinder head gasket configured to establish a gas and fluid tight seal between a cylinder head  22  and an engine block  24  of an internal combustion engine, thereby sealing combustion gasses within a plurality of combustion chambers during operation of the engine. This gas-tight seal is maintained during operation of the engine when the cylinder head  22  may lift off of the engine block  24  in response to a fuel and air combustion within one or more of the combustion chambers. However, it should be appreciated that the metal gasket  20  could find uses in a range of other vehicular or non-vehicular applications, i.e. the metal gasket  20  could be employed to seal any desirable types of first and second members. For example, the metal gasket  20  could be configured to seal an exhaust manifold (not shown) to the engine block  24 . 
     The metal gasket  20  of the first exemplary embodiment has a functional layer  26  with plurality of inner peripheries  28  which surround a plurality of openings  30  that correspond with the combustion chambers of the internal combustion engine. In the exemplary embodiment, the openings  30  of the metal gasket  20  have circular shapes and are spaced from one another to correspond with the combustion chambers of the engine block  24 . It should be appreciated that, depending on the specific application of the metal gasket  20 , the opening or openings  30  could have any suitable shape. 
     Referring now to the cross-sectional view of  FIG. 2 , the functional layer  26  further includes an embossment bead  32  which is spaced radially from the inner periphery  28  and circumferentially surrounds each of the circular openings  30 . The functional layer  26  has a generally flat portion  34  which extends radially between the inner periphery  28  and the embossment bead  32 . The generally flat portion  34  of the functional layer  26  has a first surface  36  (or a top surface  36 ) and a second surface  38  (or a bottom surface  38 ), and the embossment bead  32  extends in a first axial (or vertical) direction from the generally flat portion  34 . As shown, the embossment bead  32  includes an indentation  40  which extends in a second axial (or vertical) direction, which is opposite of the first axial direction, from the top or apex of the embossment bead  32 , thereby giving the embossment bead  32  an M or W-shape with two convex curves (or downwardly facing curves) and a single concave curve (or an upwardly facing curve) when viewed in cross-section and when in a relaxed or uncompressed condition. The embossment bead  32  on the exemplary functional layer  26  extends in the first axial direction to a bead height H B  (which is the vertical distance from the first surface  36  of the generally flat portion  34  to the apexes of the embossment bead  32 ) which is greater than 0.15 mm and is no greater than 0.30 mm (0.15 mm&lt;H≦0.30 mm) when the functional layer  26  is in the relaxed condition. Most preferably, the bead height H B  of the embossment bead  32  when the functional layer  26  is in the relaxed condition is in the range of 0.19 to 0.25 mm. These ranges are relatively high as compared to the bead heights of many other known gasket assemblies with M or W-shaped embossment beads. The relatively high bead height H B  provides for reduced forming stresses on the functional layer  26  as well as increased fatigue resistance for the embossment bead  32 . 
     The indentation  40  of the embossment bead  32  extends in the second axial (or vertical) direction by an indentation height H I  when the functional layer  26  is in the relaxed condition, and the indentation height H I  is less than the bead height H B  of the embossment bead  32 . As such, the bottom of the indentation  40  is spaced vertically above the generally flat portion  34  of the functional layer  26  when the functional layer  26  is in the relaxed condition. 
     Referring now to  FIG. 3 , when the functional layer  26  is compressed between the cylinder head  22  and the engine block  24 , the embossment bead  32  deflects elastically and plastically to maintain the gas and air tight seal between the cylinder head  22  and the engine block  24 . The cylinder head  22  is clamped down until the bottom of the indentation  40  engages against the engine block  24  to provide the embossment bead  32  on the functional layer  26  with three total points of contact or seals when viewed in cross-section. Specifically, when clamped between the cylinder head  22  and the engine block  24 , the embossment bead  32  has two points of contact with the cylinder head  22  and one point of contact with the engine block  24 . These three points of contact provide for improved sealing performance, particularly when the cylinder head  22  lifts off of the engine block  24  during operation of the engine. It should be appreciated that the metal gasket  20  could alternately be flipped by 180° relative to the orientation shown in  FIG. 3  such that the embossment bead  32  has two points of contact with the engine block  24  and one point of contact with the cylinder head  22  as viewed in cross-section. 
     Referring back to the cross-sectional view of  FIG. 2 , the exemplary embodiment of the metal gasket  20  is a single layer gasket having a single functional layer  26 . However, it should be appreciated that the functional layer  26  may be employed in a multi-layer gasket assembly with one or more additional functional layers and/or one or more distance layers (not shown) if desired. The functional layer  26  may include one or more additional embossment beads (e.g., half embossment beads) spaced radially from the M or W-shaped embossment bead  32  with the indentation  40 . 
     The metal gasket  20  may be formed of a range of different metals or combination of metals including, for example, steel, copper, aluminum, etc. The embossment bead  32  is preferably formed into the functional layer  26  through an embossing process. 
     Referring now to  FIG. 5 , a second exemplary embodiment of the metal gasket  120  is generally shown in cross-section. This exemplary embodiment is similar to the first exemplary embodiment of the metal gasket  20  described above but further includes a stopper feature  42  or element which is separate from and adjacent to the embossment bead  32 . In operation, the stopper element  42  restricts full compression of embossment bead  32  when the metal gasket  120  is compressed between the cylinder head  22  and the engine block  24 . In this exemplary embodiment, the stopper feature  42  is a separate element and is affixed to the functional layer  26  at the generally flat portion  34  adjacent the embossment bead  32 . However, it should be appreciated that the stopper feature could take many forms. For example, the stopper feature could be formed integrally with the functional layer or it could be a portion of an additional layer, such as a second functional layer or a distance layer, of a multi-layer gasket assembly. 
     Referring now to  FIG. 6 , an exemplary embodiment of a multi-layer gasket assembly  220  is generally shown in cross-section. This exemplary embodiment includes a functional layer  26  which is similar to the first exemplary embodiment described above but further includes a distance layer  244  with a stopper  242  attached thereto. The distance layer  244  and stopper  242  overly the functional layer  26  and have openings which correspond with the openings in the functional layer  26 . The distance layer  244  extends from an inner periphery  246  which is aligned with the inner periphery  28  of the functional layer  26  to an outer periphery which is spaced radially outwardly from the embossment bead  32  on the functional layer  26 . The stopper  242  also extends from an inner periphery  248  which is aligned with the inner periphery  28  of the functional layer  26  to an outer periphery  250  which is spaced radially outwardly from the embossment bead  32  on the functional layer  26 . As such, the stopper  242  extends radially across the embossment bead  32  on the functional layer  26 . This particular embodiment may be advantageous because the stopper  242  drives an increased load into the embossment bead  32  on the functional layer  26  which may improve the seal provided by the gasket assembly  220  during lifting of the cylinder head off of the engine block. The distance layer  244  and the stopper  242  are preferably formed of metal and may be joined to one another through any suitable process including, for example, welding. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims.