Abstract:
A metal gasket for an internal combustion engine includes a first metal plate with a folded portion; a ring member with a sandwiched portion having a sealing bead and an extension portion, with the sandwiched portion being sandwiched in the folded portion to provide a primary sealing portion; a second metal plate laminated to the folded portion of the first metal plate so as to sandwich the extension portion to provide a secondary sealing portion; and a third metal plate sandwiched between the first metal plate and the second metal plate in a portion of the gasket separate from the sandwiched extension portion. In the event that the cylinder head lift becomes greater than the following capability of the sealing bead in the primary sealing portion, the secondary sealing portion provides excellent following capability relative to the lift.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
   The present invention relates to a metal laminate gasket to be installed between a cylinder head and the cylinder block of an internal combustion engine, to seal therebetween. More specifically, the present invention relates to a metal laminate gasket whose secondary sealing portion is reinforced. 
   Recently, with the high performance of an engine, maximum explosion pressure has a tendency to rise. Especially, in a diesel engine, the maximum explosion pressure has a significant tendency to rise. On the other hand, with the reduction in weight of the engine, the mechanical strength has a tendency to decline. As a result, at the time of the explosion inside the cylinder, the lift of a cylinder head becomes large, and the following capability of a cylinder head gasket for the lift is required. 
   However, for example, in a conventional metal laminate cylinder head gasket wherein a primary sealing portion including a sealing bead around a combustion-chamber hole is formed, the amount of compression of the sealing bead is essentially not large compared to the lift. As a result, the following capability for the lift whose size just grew larger cannot be ensured so that an additional following capability is required. Specifically, in addition to the primary sealing portion with large heat resistance around an existing combustion-chamber hole, the secondary sealing portion with excellent following capability for a large lift of the cylinder head and excellent heat resistance is provided. Accordingly, the following capability when the cylinder head is widely lifted is required to be ensured. 
   Also, with the securing of the following capability of the secondary sealing portion when the cylinder head is widely lifted, it is required that load balance relative to the primary sealing portion, secondary sealing portion, and sealing portions around various types of holes such as a water hole and oil hole whose circumferences should be sealed should be appropriately distributed. 
   A technical problem addressed by the present invention is to provide a metal laminate gasket whose following capability relative to the lift of the cylinder head at the time of the explosion inside the cylinder is improved. Other technical problems addressed by the present invention are to provide a metal laminate gasket whose following capability when the cylinder head is largely lifted is secured by the secondary sealing portion with heat resistance and at the same time, the load balance relative to the primary sealing portion, secondary sealing portion, and the sealing portions around various types of holes whose circumferences should be sealed is appropriately distributed. 
   Further objects and advantages of the invention will be apparent from the following description of the invention. 
   SUMMARY OF THE INVENTION 
   In order to solve the above-described problems, a metal laminate gasket of the present invention is formed by laminating multiple metal plates, and includes a combustion-chamber hole corresponding to a combustion chamber of a cylinder block and a hole corresponding to a fluid hole whose circumference should be sealed. 
   In the rim of the combustion-chamber hole, the first metal plate constituting an outer plate of one side of the gasket is folded back, and a sandwiched member which at least includes a bore ring with an extension portion projecting outside of the folded portion of the first metal plate, is sandwiched in the folded portion of the first metal plate. At the same time, the second metal plate constituting the other outer plate is laminated on the surface of the folded side of the first metal plate. The extension portion in the bore ring is sandwiched between the first metal plate and the second metal plate. At the same time, a third metal plate is sandwiched in the range of not overlapping with the bore ring. 
   A bead whose height is higher than one or the other surface of the folded place of the first metal plate is provided in at least one of the first and second metal plates in the place wherein the extension portion of the bore ring is sandwiched. A primary sealing portion is formed by the folded place of the first metal plate sandwiching the sandwiched member. A secondary sealing portion is formed by the first and second metal plates in the place where the extension portion of the bore ring is sandwiched. The total thickness of the first and second metal plates, and the bore ring in the secondary sealing portion, is made smaller than the total thickness of the double thickness of the first metal plate in the primary sealing portion, and the thickness of the sandwiched member. 
   At the same time, the total thickness of the first and second metal plates, and the bore ring in the secondary sealing portion, is made larger than the total thickness of the first-third metal plates in the place where the third metal plate is sandwiched. 
   In a preferred embodiment of the present invention, the metal laminate gasket where the sandwiched member is formed by only the bore ring, the thickness t 2  of the second metal plate is made thinner than the thickness t 1  of the first metal plate, and the thickness t 3  of the third metal plate is made thinner than the thickness t 4  of the bore ring. 
   Also, the bead can be provided in the part sandwiched by the folded portion of the first metal plate in the bore ring. In addition, in another preferred embodiment of the invention, the sandwiched member can be the bore ring and a hole-rim portion relative to the combustion-chamber hole in the second metal plate. 
   In the metal laminate gasket with the above-described structure, the primary sealing portion is formed by the folded place of the first metal plate sandwiching the sandwiched member, and the secondary sealing portion is formed by the first and second metal plates in the place wherein the extension portion of the bore ring is sandwiched. As a result, the secondary sealing portion differs from a secondary sealing portion consisting of heat-resisting rubber, and includes excellent heat resistance as in the case with a primary sealing portion consisting of the metal plate. 
   In the metal laminate gasket, typically, the circumference of the combustion-chamber hole is gas-sealed in the primary sealing portion. However, in the case that the lift of the cylinder head becomes large so that the following capability of the sealing bead in the primary sealing portion cannot carry out gas-sealing, the secondary sealing portion presents an excellent following capability relative to the lift. 
   Specifically, the secondary sealing portion is located near the primary sealing portion and encloses it. The bead whose height is higher than one or the other surface of the folded place of the first metal plate is provided in at least one of the first and second metal plates in the place wherein the extension portion of the bore ring is sandwiched. 
   In addition, the total thickness of the first and second metal plates and the bore ring in the secondary sealing portion is made smaller than the total thickness of the double thickness of the first metal plate in the primary sealing portion; and the thickness of the sandwiched member. As a result, the elastic resilience of the secondary sealing portion is larger than the elastic resilience of the primary sealing portion so that the secondary sealing portion includes an excellent following capability relative to the lift compared to the primary sealing portion. 
   Also, in the secondary sealing portion, the total thickness of the first and second metal plates and the bore ring in the extension portion of the bore ring is made smaller than the total thickness of the double thickness of the first metal plate in the primary sealing portion, and the thickness of the sandwiched member. At the same time, the total thickness of the first and second metal plates and the bore ring in the extension portion of the bore ring is made larger than the total thickness of the first-third metal plates in the place where the third metal plate is sandwiched. 
   As a result, the load balance relative to the primary sealing portion, secondary sealing portion, and the sealing portions around the various types of holes whose circumferences should be sealed in the metal laminate gasket can be appropriately distributed. 
   According to the metal laminate gasket of the present invention described above, a metal laminate gasket is provided whose following capability for the lift of the cylinder head is improved. More specifically, the metal laminate gasket can ensure the following capability by the secondary sealing portion with heat resistance when the cylinder head is widely lifted. At the same time, the load balance relative to the primary sealing portion, secondary sealing portion, and the sealing portions around the various types of holes whose circumferences should be sealed can be appropriately distributed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a substantial cross-sectional view of a first embodiment of a metal laminate gasket according to the present invention; 
       FIG. 2  is a substantial cross-sectional view of a second embodiment of the metal laminate gasket according to the present invention; and 
       FIG. 3  is a substantial cross-sectional view of a third embodiment of the metal laminate gasket according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a cross-sectional shape of the circumference of a combustion-chamber hole  2  in a first embodiment of a metal laminate gasket according to the present invention. A metal laminate gasket  1  is formed by laminating the first, second, and third metal plates  11 ,  12 ,  13  in whole, and includes the combustion-chamber hole  2  corresponding to a combustion chamber of a cylinder block and a hole (not shown in the figure) corresponding to a fluid hole whose circumference should be sealed. 
   Also, in the rim of the combustion-chamber hole  2  of the metal laminate gasket  1 , the first metal plate  11  constituting one side of an outer plate of the gasket is folded back, and a sandwich portion  14   a  of a bore ring  14  consisting of a ring-shaped metal plate is sandwiched in a folded portion  11   a . At the same time, the second metal plate  12  constituting another outer plate is laminated on the face of the folded side of the first metal plate  11 , and an extension portion  14   b  of the bore ring  14  projecting outside of the folded portion  11   a  is sandwiched between the first metal plate  11  and second metal plate  12 . Also, the third metal plate  13  is sandwiched in the range of not overlapping with the bore ring  14 . 
   More specifically, the metal laminate gasket  1  constitutes a folded place of the first metal plate  11  by: the folded portion  11   a  of the first metal plate  11 ; and a metal-plate portion  11   b  located in such a way as to face the folded portion  11   a  which is a non-folded side of the first metal plate  11 . Also, the sandwich portion  14   a  of the bore ring  14  which is a sandwiched member is sandwiched by the folded portion  11   a  and the metal-plate portion  11   b  in the folded place. 
   Also, in the sandwich portion  14   a  of the bore ring  14 , a circular sealing bead  14   c  which is concentric with the combustion-chamber hole  2  and encloses the combustion-chamber hole  2  is formed with a full bead. Also, in the first metal plate  11 , in the place where the extension portion  14   b  of the bore ring  14  is sandwiched, two circular sealing beads  11   c ,  11   d  which are concentric with the combustion-chamber hole  2  and slope in the opposite direction to each other are formed with a half bead. A circular depression  15  enclosing the sealing bead  14   c  is provided between the two half beads  11   c ,  11   d.    
   Also, in the second metal plate  12 , a sealing bead  12   a  which is concentric with the combustion-chamber hole  2  and slopes in a direction opposite to the sealing bead  11   d  is formed with a half bead in a location opposed to the sealing bead  11   d  in the place wherein the extension portion  14   b  of the bore ring  14  is sandwiched. The height of the sealing bead  12   a  is higher than the height of the surface of the folded portion  11   a  of the first metal plate  11 . Also, even in the case in which the metal laminate gasket  1  is fastened between the cylinder block and a cylinder head by a fastening bolt so that the sealing bead  12   a  is crushed, the height of the sealing bead  12   a  is higher than the height corresponding to the expected lift of the cylinder head. 
   Also, in the second metal plate  12 , sealing beads (half beads)  12   b ,  12   c  are provided in a place where the third metal plate  13  is sandwiched. In the third metal plate  13 , sealing beads (half beads)  13   b ,  13   c  sloping in directions opposite to the sealing beads  12   b ,  12   c  are provided in locations opposed to the sealing beads (half beads)  12   b ,  12   c.    
   In addition, as shown in  FIG. 1 , a hole-rim portion  12   e  relative to the combustion-chamber hole  2  of the second metal plate  12  is provided in a location overlapping a part of the extension portion  14   b  of the bore ring  14  located near an edge  11   e  of the folded portion  11   a  of the first metal plate  11 . The hole-rim portion  12   e  is not sandwiched by the folded portion  11   a  of the first metal plate  11 . 
   Also, in the metal laminate gasket  1 , a primary sealing portion  3  is formed by the folded place of the first metal plate  11  sandwiching the bore ring  14 . A secondary sealing portion  4  encloses the primary sealing portion  3  by the first and second metal plates  11 ,  12  in a place where the extension portion  14   b  of the bore ring  14  is sandwiched. The total thickness (t 1 +t 2 +t 4 ) of a thickness t 1  of the first metal plate  11  in the secondary sealing portion  4 ; a thickness t 2  of the second metal plate  12 ; and a thickness t 4  of the bore ring  14  is made smaller than the total thickness ( 2  t 1 +t 4 ) of the double thickness 2 t 1  of the first metal plate  11  in the primary sealing portion  3 ; and the thickness t 4  of the bore ring  14 . 
   At the same time, the total thickness (t 1 +t 2 +t 4 ) of the thickness t 1  of the first metal plate  11  in the secondary sealing portion  4 ; the thickness t 2  of the second metal plate  12 ; and the thickness t 4  of the bore ring  14  is made larger than the total thickness (t 1 +t 2 +t 3 ) of the first-third metal plates  11 - 13  in the place where the third metal plate is sandwiched. In such case, the thickness t 2  of the second metal plate  12  can be made thinner than the thickness t 1  of the first metal plate  11 , and the thickness t 3  of the third metal plate  13  can be made thinner than the thickness t 4  of the bore ring  14 . 
   The metal laminate gasket  1  with the above-described structure forms: the primary sealing portion  3  by the folded place of the first metal plate  11  sandwiching the bore ring  14 ; and the secondary sealing portion  4  by the first and second-metal plates  11 ,  12  in the place wherein the extension portion  14   b  of the bore ring  14  is sandwiched. As a result, the secondary sealing portion  4  includes excellent heat resistance in a similar fashion with the primary sealing portion  3  consisting of the metal plate and differs from a secondary sealing portion consisting of heat-resisting rubber. 
   In the metal laminate gasket  1 , typically, the circumference of the combustion-chamber hole  2  is gas-sealed in the primary sealing portion  3 . However, in the case that the lift of the cylinder head becomes large so that the following capability of the sealing bead in the primary sealing portion  3  cannot carry out gas-sealing, the secondary sealing portion  4  presents the excellent following capability relative to the lift. 
   Specifically, in the secondary sealing portion  4 , the total thickness (t 1 +t 2 +t 4 ) of the thickness t 1  of the first metal plate  11  in the secondary sealing portion  4 ; the thickness t 2  of the second metal plate  12 ; and the thickness t 4  of the bore ring  14  is made smaller than the total thickness (2 t 1 +t 4 ) of the double thickness 2 t 1  of the first metal plate  11  in the primary sealing portion  3 ; and the thickness t 4  of the bore ring  14 . As a result, the rigidity of the secondary sealing portion  4  is made smaller than the rigidity of the primary sealing portion  3 . 
   In addition, the bead  12   a  whose height is higher than the surface of the folded portion  11   a  of the first metal plate  11  is provided in the metal plate  12  in the place where the extension portion  14   b  of the bore ring  14  is sandwiched. As a result, even in the case that the elastic resilience of the secondary sealing portion  4  is larger than the elastic resilience of the primary sealing portion so that the primary sealing portion  3  can not follow the lift of the cylinder head any more, the secondary sealing portion  4  follows the lift and carries out the gas-sealing. 
   Also, in the secondary sealing portion  4 , the total thickness (t 1 +t 2 +t 4 ) of the thickness t 1  of the first metal plate  11  in the extension portion  14   b  of the bore ring  14 ; the thickness t 2  of the second metal plate  12 ; and the thickness t 4  of the bore ring  14  is made smaller than the total thickness (2 t 1 +t 4 ) of the double thickness 2 t 1  of the first metal plate  11  in the folded portion of the first metal plate  11 ; and the thickness t 4  of the bore ring  14 . 
   At the same time, the total thickness (t 1 +t 2 +t 4 ) of the thickness t 1  of the first metal plate  11  in the extension portion  14   b  of the bore ring  14 ; the thickness t 2  of the second metal plate  12 ; and the thickness t 4  of the bore ring  14  is made larger than the total thickness (t 1 +t 2 +t 3 ) of the first-third metal plates  11 - 13  in the range of not overlapping with the bore ring  14 . 
   As a result, the load balance relative to the primary sealing portion  3 , secondary sealing portion  4 , and the sealing portions around various types of holes (not shown in the figure) whose circumferences should be sealed in the metal laminate gasket  1  can be appropriately distributed. 
     FIG. 2  shows the cross-sectional shape of the circumference of the combustion-chamber hole  2  in a second embodiment of the metal laminate gasket according to the present invention. The second embodiment differs from the first embodiment in the following points, however, other structures are the same as those of the first embodiment. 
   The first point is that the sealing bead is not provided in the bore ring  14  in the primary sealing portion  3 . The second point is that the sealing beads are not provided in the first metal plate  11  in the secondary sealing portion  4 . In the second embodiment, the sealing bead is not provided in the bore ring  14  of the primary sealing portion  3  and the first metal plate  11  in the secondary sealing portion  4 , so that the structure of the metal laminate gasket  1  becomes simple compared to the structure of the first embodiment, and can be easily manufactured. 
     FIG. 3  shows the cross-sectional shape of the circumference of the combustion-chamber hole  2  in a third embodiment of the metal laminate gasket according to the present invention. The third embodiment differs from the first embodiment in the following points (a)-(d), however, other structures are the same as those of the first embodiment. 
   (a) In the first embodiment, the sandwiched member sandwiched in the folded place of the first metal plate  11  is only the bore ring  14 . However, in the third embodiment, the bore ring  14  and the hole-rim portion  12   e  relative to the combustion-chamber hole  2  in the second metal plate  12  are sandwiched in the folded place of the first metal plate  11 . As a result, the total thickness of the metal plates  11 ,  12  and the bore ring  14  in the primary sealing portion  3  becomes (2 t 1 +t 2 +t 4 ), and has a thickness that increases by just the thickness t 2  of the second metal plate  12  compared to the case of the first embodiment. 
   (b) The bore ring  14  forms a circular sealing bead  14   d  in the extension portion  14   b . The sealing bead  14   d  is concentric with the half bead  12   a  of the second metal plate  12  and slopes in the opposite direction of the half bead  12   a  from the same radial position with the half bead  12   a . The sealing bead is not formed in the sandwich portion  14   a.    
   (c) The first metal plate  11  includes the sealing bead (half bead)  11   e  whose height is higher than the surface of the metal-plate portion  11   b  which slopes toward the upper side of the extension portion  14   b  from near the border with the metal-plate portion  11   b  in the place wherein the extension portion  14   b  of the bore ring  14  is sandwiched. The sealing beads  11   c ,  11   d  and the circular depression  15  in the first embodiment are not provided. 
   (d) The thickness t 1  of the first metal plate is made thinner than the thickness t 2  of the second metal plate. 
   In the third embodiment, the sealing bead  11   e  whose height is higher than the metal-plate portion  11   b  of the folded place of the first metal plate  11  is provided even in the first metal plate  11  in the place where the extension portion  14   b  is sandwiched, in addition to the sealing bead  12   a  provided in the metal plate  12 . Moreover, the circular sealing bead  14   d  is formed in the extension portion  14   b  of the bore ring  14 , is concentric with the half bead  12   a  of the second metal plate  12 , and slopes in the opposite direction of the half bead  12   a  from the same radial position with the half bead  12   a . As a result, the following capability relative to the lift of the cylinder head is additionally improved. 
   Also, in the third embodiment, the sandwich portion  14   a  of the bore ring  14  and the hole-rim portion  12   e  of the second metal plate  12  are sandwiched by: the folded portion  11   a  in the folded place of the first metal plate  11 ; and the metal-plate portion  11   b . As a result, the binding between the first metal plate  11  and the second metal plate  12  can be increased. 
   Also, in the third embodiment, the total thickness of the metal plates  11 ,  12 , and the bore ring  14  in the primary sealing portion  3  has a thickness that increases by just the thickness t 2  of the second metal plate  12  relative to the first embodiment. Even in that case, the thickness t 1  of the first metal plate is made thinner than the thickness t 2  of the second metal plate so that the increase of the total thickness (2 t 1 +t 2 +t 4 ) of the metal plates  11 ,  12 , and the bore ring  14  in the primary sealing portion  3  can be restrained. 
   The disclosure of Japanese Patent Application No. 2005-020284 filed on Jan. 27, 2005, is incorporated herein.