Abstract:
A metal laminate gasket to be arranged between two members includes a first metal plate and a second metal plate laminated together. The first metal plate has a first hole to be sealed, a first bead around the first hole, and a plurality of second holes around the first bead as bolt holes. The second metal plate has a third hole and fourth holes corresponding to the first and second holes, respectively, and depressions formed at a side facing the first metal plate around the third hole. Each of the depressions is formed on two sides of a line connecting a center of the third hole and a center of each of the fourth holes so that a compressing force of the bead when the gasket is compressed becomes substantially equal around the first hole.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
       [0001]    The invention relates to a metal laminate gasket that is mounted between two members coupled to each other, which have holes to be mutually communicated, for sealing the periphery of the holes. The invention relates, in particular, to a metal laminate gasket that is suitably used at the terminal or connecting areas of various supply and exhaust pipes. 
         [0002]    It is very commonly known to form a structure in connecting, via a metal laminate gasket having a bead for sealing, two members having holes to be mutually communicated, such as connecting areas of various supply and exhaust pipes. In this connecting structure, flanges, or equivalents thereto, are provided at the connecting areas of the two members, and the flanges are mutually fastened and fixed by bolts at several points around the holes. 
         [0003]    The same applies to the connection of a cylinder block and a head block in an internal combustion engine, through a cylinder head gasket. 
         [0004]    In a case where, at the connecting areas of such two members, the above-mentioned flanges are fastened and fixed by the above-mentioned bolts at several points around the hole to be mutually communicated, the compressing force working on the bead between the flanges becomes very great at places near the bolts. On the other hand, at places away from the bolts, the compressing forces become weak because their fastening forces have less effect there. As a result, there arises a problem that stable sealing cannot be provided because the bead surface pressure in the gasket around the hole to be mutually communicated becomes unequal. This sort of problem becomes more apparent as the mechanical strength of flanges or equivalents thereto becomes weaker because of saving of material for economy and making the members to be coupled to each other with light weight. 
         [0005]    The technical feature covered by this invention is that in connecting two members having holes to be mutually communicated via a metal laminate gasket having a bead at its hole edge by mutually fastening and fixing the two members by means of bolts at several points on the flanges in their connecting areas, the compressing force of the above-mentioned bead generated by the fastening forces of the above-mentioned bolts is made substantially equal in the circumference of the hole edge. 
         [0006]    Further objects and advantages of the invention will be apparent from the following description of the invention. 
       SUMMARY OF THE INVENTION  
       [0007]    In order to solve the above-mentioned problem, a metal laminate gasket is mounted between two members coupled to each other which have holes to be mutually communicated for sealing of the peripheries of the holes, wherein the gasket is formed by laminating multiple metal plates, and has a communicating hole corresponding to the holes to be mutually communicated of the above-mentioned two members, and around the communicating hole, several bolt holes to insert bolts to fasten the above-mentioned two members. 
         [0008]    In the gasket, one of the metal plates is formed as a bead plate, to have a bead on the edge of the communicating hole, and on the same edge in another metal plate, on both sides of a line connecting the center of the communicating hole and the center of each of the bolt holes, a depression is formed by coining to make the compressing force of the bead generated by the fastening force of the bolts even. 
         [0009]    In a preferred embodiment of the above-mentioned metal laminate gasket of the present invention, each of the above-mentioned depressions is formed in such a way to have an area with a constant depth within a range of 15 to 20 degrees on each side of the line connecting the center of the above-mentioned communicating hole and the center of the bolt hole and to have, on both sides of the constant depth area, gentle faces leading to the metal plate surface. Moreover, the above-mentioned depressions formed by coining can be regulated so that the compressing force of the above-mentioned beads may be equalized by its measurement. Furthermore, in the above-mentioned metal laminate gasket, two to six bolt holes according to the number of bolts needed to couple the above-mentioned two members can be arranged equally around the above-mentioned communicating hole. 
         [0010]    It should be noted that the metal laminate gaskets of the present invention can be applied not only in the connection, via a gasket, of two members, such as connecting areas of various supply and exhaust pipes, that have holes to be mutually communicated, but also in the case of a cylinder head gasket interposed between a cylinder block and a head block in an internal combustion engine. 
         [0011]    In cases where two members having holes to be mutually communicated are connected, via a metal laminate gasket having a bead on its communicating hole edge, by means of mutually fastening and fixing with bolts at several points in the flanges of the connecting areas of the two members, the metal laminate gasket of the present invention makes it possible to even the compressing force of the bead generated by the fastening force of the bolts in the circumference of the communicating hole edge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]      FIG. 1  is a plan view showing a first embodiment of a metal laminate gasket of the present invention. 
           [0013]      FIG. 2  is an enlarged cross sectional view taken along line  2 - 2  in  FIG. 1 . 
           [0014]      FIG. 3  is an enlarged cross sectional view taken along line  3 - 3  in  FIG. 1 . 
           [0015]      FIG. 4  is an enlarged cross sectional view taken along line  4 - 4  in  FIG. 1 . 
           [0016]      FIG. 5  is an enlarged partial cross sectional view at the same position as  FIG. 2  in a second embodiment of the metal laminate gasket of the present invention. 
           [0017]      FIG. 6  is an enlarged partial cross sectional view at the same position as  FIG. 2  in a third embodiment of the metal laminate gasket of the present invention. 
           [0018]      FIG. 7  is a partial top view showing a fourth embodiment in which the metal laminate gasket of the present invention is applied to a cylinder head gasket. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0019]      FIGS. 1 to 4  illustrate a first embodiment of the metal laminate gasket of the present invention. Metal laminate gasket  1  is mounted between two members coupled to each other which have holes to be mutually communicated, such as the connecting areas of various supply and exhaust pipes, for the sealing of the peripheries of the holes at the connecting areas. It can also be applied, for example, to a cylinder head gasket interposed between a cylinder block and a head block in an internal combustion engine. 
         [0020]    The above-mentioned metal laminate gasket  1  is formed by laminating multiple metal plates. In the first embodiment illustrated in the figure, the gasket has two outer plates  2  and  3 , formed by metal plates, and intermediate plate  4  which is interposed between outer plates  2  and  3 . Outer plates  2  and  3  and intermediate plate  4  have holes  2   b,    3   b  and  4   a  to be mutually communicated. Gasket  1  has communicating hole  5 , formed by holes  2   b,    3   b  and  4   a,  which communicates holes  8   a  and  9   a  of two members  8  and  9  coupled to each other via the gasket  1 . It also has bolt holes  6  around communicating hole  5  to insert bolts (illustration omitted) to couple the above-mentioned two members  8  and  9 . 
         [0021]    The figure here illustrates a case in which three bolt holes  6  are equally arranged around communicating hole  5 , but in other cases, two to six bolt holes according to the number of bolts needed to couple two members  8  and  9  can be equally arranged around communicating hole  5 . 
         [0022]    In the above-mentioned metal laminate gasket  1 , outer plates  2  and  3  among the above-mentioned laminated metal plates, serving as bead plates, form beads (half beads)  2   a  and  3   a  on the edge of communicating hole  5 . Depressions  7  shown in  FIGS. 1 to 3  are formed by coining on the edge of communicating hole  5  of intermediate plate  4 , which is the other laminated metal plate. 
         [0023]    Depressions  7  are provided on both sides of line L connecting the center of the above-mentioned communicating hole  5  and the center of each of bolt holes  6  for the purpose of equalizing the compressing force of beads  2   a  and  3   a  generated by the fastening force of the above-mentioned bolts. Depressions  7  and the above-mentioned beads  2   a  and  3   a  are formed so that they are mutually superimposed. 
         [0024]    In cases of connecting the connecting areas of these two members  8  and  9  by mutually fastening and fixing them with bolts at several points around holes  8   a  and  9   a  to be mutually communicated, and in particular when the mechanical strength at the flanges of two members  8  and  9  is insufficient, the compressing force working on beads  2   a  and  3   a  between two members  8  and  9  is very great at places near the bolt and is weak at places away from the bolt due to less effect of its fastening force. However, if the above-mentioned depressions  7  are provided near the bolt holes, the compressing force of the above-mentioned beads  2   a  and  3   a  generated by the fastening force of the bolts is equalized around communicating hole  5 , so that stable sealing in the circumference of the communicating hole  5  can be provided. 
         [0025]    The range, in the circumference of the above-mentioned communicating hole  5 , where depressions  7  should be provided differs depending on the mechanical strength of the connecting areas of two members  8  and  9  to be connected via gasket  1 . Generally speaking, it is preferable that area  7   a  with a constant depth should be formed in a range of 15 to 20 degrees on both sides of line L connecting the center of the above-mentioned communicating hole  5  and the center of each of bolt holes  6 , and areas  7   b  should be formed on both sides of area  7   a  with its gentle face leading to the surface of intermediate plate  4 . 
         [0026]    Furthermore, the setting form of the above-mentioned depression  7  formed by coining and, in particular, the width of area  7   a  having a constant depth as well as the shape of the curved surface of area  7   b  having a gentle face can be regulated, by measuring the compressing force of the above-mentioned beads  2   a  and  3   a  by means of pressure sensitive paper, so that the force is equalized. 
         [0027]      FIGS. 5 and 6  illustrate cross sectional views in second and third embodiments of the present invention at the position corresponding to position  2 - 2  in  FIG. 1 . 
         [0028]    Metal laminate gasket  11  in the second embodiment of the present invention shown in  FIG. 5  has, as laminated multiple metal plates, outer plates  12  and  13 , as well as two intermediate plates  14 A and  14 B interposed between these outer plates  12  and  13 . 
         [0029]    These outer plates  12  and  13  as well as intermediate plates  14 A and  14 B have communicating hole  15  corresponding to holes  8   a  and  9   a  (see  FIG. 2 ) of the above-mentioned two members  8  and  9  coupled to each other via gasket  11 . Bolt holes are to be provided around this communicating hole  15  as a matter of course but they are omitted in the figure. 
         [0030]    In the above-mentioned metal laminate gasket  11 , outer plates  12  and  13  among the above-mentioned laminated metal plates, serving as bead plates, form beads (full beads)  12   a  and  13   a  on the edge of communicating hole  15 . With regard to the other laminated metal plates, namely two intermediate plates  14 A and  14 B, the thinner intermediate plate  14 B is folded back in such a way that it covers the edge of communicating hole  15  at the thicker intermediate plate  14 A, and depression  17  which is substantially the same as depression  7  in the first embodiment previously described in  FIGS. 1 to 3  is formed by coining on intermediate plate  14 A in the part covered by intermediate plate  14 B. Thus, the intermediate plate  14 B has a base portion  14 B 1  and a flange  14 B 2 . 
         [0031]    The description of the structure of this depression  17 , including the range of its setting and its effects, is omitted here to avoid duplication since they are the same as in the case of the first embodiment. 
         [0032]    Metal laminate gasket  21  in the third embodiment of the present invention shown in  FIG. 6  has, as laminated multiple metal plates, outer plates  22  and  23 , as well as two intermediate plates  24 A and  24 B situated between these outer plates  22  and  23 . These outer plates  22  and  23  as well as intermediate plates  24 A and  24 B have communicating hole  25  corresponding to holes  8   a  and  9   a  (see  FIG. 2 ) of the above-mentioned two members  8  and  9  coupled to each other via gasket  21 . Bolt holes are to be provided around this communicating hole  25  as a matter of course but they are omitted in the figure. 
         [0033]    In the above-mentioned metal laminate gasket  21 , with regard to the two intermediate plates  24 A and  24 B among the above-mentioned laminated metal plates, the thinner intermediate plate  24 B is folded back, as in the case of the second embodiment, in such a way that it covers the edge of communicating hole  25  at the thicker intermediate plate  24 A. The other laminated metal plates, namely outer plates  22  and  23 , serve as bead plates, wherein outer plate  22  forms bead (full bead)  22 a, as in the case of the second embodiment, on the edge of communicating hole  25 , and outer plate  23  is laminated on intermediate plate  24 A within a limit not reaching the edge of the folded-back part of intermediate plate  24 B and forms bead (half bead)  23   a  at its end. 
         [0034]    As in the case of the second embodiment, depression  27  is formed by coining on intermediate plate  24 A in the part covered by thinner intermediate plate  24 B. The description of the structure of this depression  27 , including the range of its setting and its effects, is omitted here since they are the same as in the case of depression  7  in the first embodiment previously described in  FIGS. 1 to 3 . 
         [0035]      FIG. 7  illustrates a fourth embodiment in which a metal laminate gasket of the present invention is applied to a cylinder head gasket. 
         [0036]    In this fourth embodiment, the two members  8  and  9  coupled to each other shown in  FIG. 2  are a cylinder block and a head block in an internal combustion engine, and metal laminate gasket  31  shown in the figure, interposed between them, is arranged as a cylinder head gasket. 
         [0037]    As in the first to third embodiments mentioned above, this metal laminate gasket  31  is formed by laminating multiple metal plates, and is arranged so that the communicating hole  35  provided in these plates faces the combustion chamber hole of the internal combustion engine. Bolt holes  36  are arranged around communicating hole  35 . 
         [0038]    In the above-mentioned metal laminate gasket  31 , part of the laminated metal plates, serving as a bead plate, forms bead  32   a  on the edge of communicating hole  35 , and depressions  37  are formed, by coining, on the edge of communicating hole  35  of the other laminated metal plate. These are substantially the same as described in the first to third embodiments. 
         [0039]    The above-mentioned depressions  37  are provided on both sides of the line connecting the center of the above-mentioned communicating hole  35  and the center of each of bolt holes  36  for the purpose of equalizing the compressing force of the above-mentioned bead  32   a  generated by the fastening force of bolts. As for this depression  37 , the description of its structure including the range of its setting and its effects is omitted here since they are the same as in the case of the first embodiment. 
         [0040]    The disclosure of Japanese Patent Application No. 2007-266721 filed on Oct. 12, 2007 is incorporated as a reference. 
         [0041]    While the invention has been described with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.