The present invention relates to a metal gasket with a locally heat-treated bead used for an internal combustion engine.
An internal combustion engine has been developed to provide high power and light weight. As a result, high pressure and high temperature are applied to the engine. Since a metal gasket is strong against high pressure and high temperature, the metal gasket has been widely used.
In the metal gasket, when holes, such as cylinder bores, water holes, oil holes and so on, are sealed, beads are formed on a metal plate around the holes to project outwardly from a metal plate. When the metal plate with the beads is situated between a cylinder block and a cylinder head and is tightened, the beads are compressed to provide surface pressures thereat, by which the holes are sealed.
In the gasket, the various holes are formed as stated above. However, since high pressure and high temperature are formed in the cylinder bores, bolts for tightening the cylinder head and the cylinder block are arranged around the cylinder bores to provide surface pressures around the cylinder bores as equal as possible. The pressures for other holes are less than those of the cylinder bores.
When the gasket is designed, therefore, the highest surface pressures are formed around the cylinder bores to securely seal therearound. In case the beads are formed around the various holes, in view of the required arrangement of the surface pressures on the gasket, the beads around the cylinder bores are formed to provide the surface pressures higher than those of the other holes.
In order to change the surface pressure of the bead, the height and/or width of the bead is changed. Generally speaking, as the height of the bead increases, the surface pressure of the bead increases, and as the width of the bead decreases, the surface pressure of the bead increases. Further, in case the hardness or the thickness of the plate for the bead is changed, the surface pressure of the bead is changed, as well.
The metal gaskets and metal laminate gaskets have been designed and prepared in view of the above, for example, U.S. Pat. No. 5,536,024. However, in case the surface pressures of the beads on one metal plate are changed, the width and/or height of the beads must be changed. In this respect, although the surface pressure of the bead can be adjusted by changing the width and/or height of the bead, the surface pressure can not be precisely adjusted by changing the width and/or height of the bead.
In view of the above, the present invention has been made, and an object of the invention is to provide a metal gasket with a bead, wherein the surface pressure of the bead can be changed easily without changing the width and height.
Another object of the invention is to provide a metal gasket as stated above, wherein the surface pressures of the beads on one metal plate can be changed easily.
A further object of the invention is to provide a metal gasket as stated above, wherein the arrangement of the beads with different surface pressures can be made easily.
Further objects and advantages of the invention will be apparent from the following description of the invention.