Abstract:
A metal gasket is formed by a bead plate provided with a continuous bead, and an outer plate partly bent around combustion chamber holes to laminate the metal plates together. The bead has a linear common portion situated in an intermediate area between two cylinder bore holes, curved surrounding portions diverging from the linear common portion near the one second hole to partly surround the cylincder bore and water hole, and a curved linking portion extending between the curved surrounding portions to partly surround the water hole. The water hole is completely surrounded by the parts of the curved surrounding portions and the curved linking portion.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to a metal gasket with a continuous bead interposed between a cylinder head and cylinder block of an internal combustion engine. 
     Conventionally, in a cylinder head gasket interposed between a cylinder head and a cylinder block of an internal combustion engine, especially in case the gasket seals a water hole located close to an area between two combustion holes of the engine where an interval between the combustion holes is narrow, there is a difficulty in sealing the water hole. 
     Also, in recent years, in order to secure a durability of the gasket itself, a metal gasket has been used widely. In the metal gasket, in case an interval or intermediate area between the combustion chamber holes adjacent to each other is narrow, beads around these combustion chamber holes are connected to each other to form a common portion in the intermediate area between the combustion chamber holes. In this case, curved portions surrounding the combustion chamber holes diverge at an intersecting portion from the common portion. However, if it is tried to form a water hole outside the intersecting portion close to the center of the intermediate area between the combustion chamber holes, it is difficult to surround a periphery of the water hole by the curved portions of the bead. 
     Accordingly, an object of the invention is to provide a metal laminate gasket with a continuous bead, in which a water hole can be formed outside the bead intersecting portion and close to a center of the intermediate portion between the combustion chamber holes. 
     Another object of the invention is to provide a metal laminate gasket as stated above, in which intermediate portion between the adjacent combustion chamber holes and the water hole can be effectively sealed by bead portions. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     A metal laminate gasket of the invention is used for an internal combustion engine having a plurality of cylinder bores and at least one water hole. The gasket is basically formed by a first metal plate, and a second metal plate laminated together. 
     The first metal plate includes a plurality of first holes corresponding to the cylinder bores, an intermediate area between two first holes, at least one second hole corresponding to the at least one water hole and located in the intermediate area, and a continuous bead situated around the first and second holes. The bead has a linear common portion situated in the intermediate area, curved surrounding portions diverging from the linear common portion at an intersecting section near the at least one second hole to partly surround the first and at least one second holes, and a curved linking portion extending between the curved surrounding portions to partly surround the at least one second hole. The second hole is completely surrounded circularly by the curved surrounding portions and the curved linking portion. 
     The second metal plate has a main portion laminated on the first metal plate, third and fourth holes corresponding to the first and second holes, curved portions situated in the respective first holes, and flanges extending from the respective curved portions and located partly over the first metal plate to sandwich the first metal plate between the main portion and the flange. Each flange has a linear edge at the intermediate area to sandwich the linear common portion between two of the linear edges, and a curved edge surrounding the first hole. 
     In the metal gasket of the invention, since the periphery of the second hole, i.e. water hole, formed outside the bead intersecting portion between the adjacent first holes, i.e. combustion chamber holes, is surrounded and sealed by the curved surrounding portions and the curved linking portions, the water hole can be provided close to the center at the immediate portion outside of the bead intersecting portion. 
     The metal laminate gasket may further include a third metal plate laminated on the first metal plate to sandwich the first metal plate between the main portion and the flange of the second metal plate. The third metal plate includes a thick portion laminated on the bead and thin portions laminated on the flanges. Instead of forming the thick and thin portions, a fourth metal plate may be laminated on the third metal plate to be located at the continuous bead. Accordingly, the bead can provide a strong surface pressure when the gasket is compressed between the cylinder head and the cylinder block. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view showing an embodiment of a metal laminate gasket according to the present invention; 
     FIG. 2 is an enlarged plan view showing a main section of the embodiment, in which an outer plate is omitted; 
     FIG. 3 is a cross sectional view taken along line  3 — 3  in FIG. 2; 
     FIG. 4 is a cross sectional view taken along line  4 — 4  in FIG. 2; and 
     FIG. 5 is a cross sectional view, similar to FIG. 3, of another embodiment of the metal gasket of the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 through 4 show an embodiment of a metal gasket according to a present invention. A metal gasket is formed by laminating a plurality of (three or more) metal plates, and here, the metal gasket is formed by an outer plate  10 , a bead plate  20  and a sealing plate  30  laminated together. The outer plate  10  includes a main portion  10   a  extending substantially throughout the entire area of the gasket, curved portions  10   b  extending from the main portion  10   a  to surround respective combustion chamber holes  1 , and flanges  11  extending from the curved portions  10   b  to hold and fix the bead plate  20  and the sealing plate  30  between the main portion  10   a  and the flange  11 . 
     The bead plate  20  includes a continuous bead  21  surrounding the combustion chamber holes  1  and water holes  4 . The sealing plate  30  abuts against the continuous bead  21  formed in the bead plate  20 . The metal gasket includes the aforementioned plates  10 ,  20  and  30 , and in addition, still another metal plate or the like may be laminated. 
     As shown in FIG. 1, in the gasket formed by laminating the metal plates, a plurality of combustion chamber holes  1  is closely disposed with a narrow interval or intermediate area  5  therebetween, and water holes  2  are formed outside bead intersecting portions  22  of the bead  21 , described later, in a space between the adjacent combustion chamber holes  1 . Also, bolt holes  3 , other fluid holes  4  and the like, which are necessary to the gasket, are formed. 
     In the outer plate  10  forming the gasket, the portions, i.e. curved portions  10   b , around the respective combustion chamber holes  1  are bent, and the flanges  11  extend from the curved portions  10   b  to fix other laminated metal plates between the main portion  10   a  and the flange  11 . The curved portions  10   b  and flanges  11  form sealing sections around the combustion chamber holes  1 . In order to fix the other metal plates, not only the portions around the combustion chamber holes  1  but also outer peripheries of other portions of the outer plate  10  may be bent. 
     The bead plate  20  held by the flanges  11  of the outer plate  10  is formed of a spring steel plate, and includes the continuous bead  21 . The continuous bead  21  includes curved bead portions or curved surrounding portions  21   a  surrounding the respective combustion chamber holes  1  for sealing the periphery thereof, a common linear portion or common bead  23 , and a curved linking portion or connection bead  24 . Namely, in the intermediate area  5  between the two adjacent combustion chamber holes  1 , the curved bead portions  21   a  around the respective combustion chamber holes  1  are combined to thereby form the common bead  23 . In other words, the common bead  23  is located between the bead intersecting portions  22 . The bead width of the common bead  23  is the same as that of the curved portions  21   a  around the combustion chamber hole  1 , or may be wider. 
     In the gasket, the water holes  2  are formed immediately outside the bead intersecting portions  22 , and the connection bead  24  is formed between the curved bead portions  21   a . A circular sealing section surrounding a periphery of the water hole  2  is formed by parts  21   b  of the curved bead portions  21   a  and the connection bead  24 . Thus, the parts  21   b  of the curved bead portions  21   a  slightly project toward the combustion chamber holes  1 . Incidentally, the centers of the respective beads described above are shown by one-dotted chain lines in FIG.  2 . 
     On the other hand, the sealing plate  30  is located outside the bead plate  20  and abuts against the curved bead  21   a , the common bead  23  and the connection bead  24  to seal the abutting portions. The sealing plate  30  has dented portions  30   a  around the combustion chamber holes  1  where the flanges  11  are placed. The depth of the dented portion  30   a  is less than the thickness of the flange  11 . Therefore, when the gasket is tightened, the surface pressure without elasticity is formed at the flanges  11 , and the surface pressure with elasticity is formed on the continuous bead  21 . 
     As shown in FIG. 5, instead of the sealing plate  30 , it is possible to use a sealing plate  31  which abuts against the continuous bead  21  of the bead plate  20 , and an outer plate  32  which is laminated with the sealing plate  31  to thereby cover and enclose the sealing plate  31 . The surface pressure by the bead  21  is supported by the sealing plate  31 . 
     In the invention, since the water holes  2  are formed close to the center of the intermediate area  5  between the combustion chamber holes  1 , parts, i.e. curved dents,  11   a  of the flange  11  are dented close to the combustion chamber holes  1 , and middle areas  11   b  of the flanges  11  located between the water holes  2  are formed linearly to have a linear edge  11   b ′. The middle areas  11   b  sandwich the common bead  23  to securely seal between the combustion chamber holes  1 . 
     Incidentally, it is not always necessary to laminate a plurality of the metal plates forming the gasket in the order described above, and it is sufficient that the continuous bead  21  including the curved bead  21   a , the common bead  23  and connection bead  24 , is formed in one of the metal plates described above, and the sealing plate  30  abuts against these beads. 
     In the metal gasket structured as described above, since the periphery of the water hole  2  formed outside the bead intersecting portion  22  between the adjacent combustion chamber holes  1  is surrounded and sealed by the curved beads  21   a , which surround the combustion chamber holes  1 , and the connection bead  24 , it is possible to provide the water hole  2  at the immediate area outside the bead intersecting portion  22  between the two adjacent combustion chamber holes  1 . 
     Also, the metal gasket of the invention includes the outer plate  10  which are bent around the combustion chamber holes  1  to fix a plurality of the metal plates, the bead plate  20  in which the bead portions  21   a ,  23 ,  24  are formed, and the sealing plate abutting against the beads  21   a ,  23  and  24 . Accordingly, the narrow intermediate area  5  between the adjacent combustion chamber holes and the periphery of the water hole  2  can be effectively sealed by the continuous bead  21 . 
     As described above, according to the metal gasket of the invention, the water hole can be formed close to the combustion chamber hole outside the bead intersecting section. Also, in the gasket in which a plurality of metal plates is laminated, the narrow portion between the adjacent combustion chamber holes and the periphery of the water hole can be effectively sealed by the bead. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.