The present invention relates to a steel laminate gasket for an internal combustion engine to provide desired surface pressure around a hole to be sealed.
An engine for an automobile has been developed to seek high power and light weight. In order to satisfy these demands for the engine, an engine is made of aluminum alloy, to which high temperature and high pressure are applied.
Since a steel laminate gasket is made of a plurality steel plates, the steel laminate gasket is strong against high temperature and pressure. Therefore, the steel laminate gasket has been used widely for a recent engine to which high temperature and pressure are applied.
A cylinder head of a recent engine is generally made of aluminum alloy. In some cases, a cylinder block is also made of aluminum alloy. In case the cylinder head or cylinder block is made of aluminum alloy, a large amount of tightening pressure can not be applied to tighten the cylinder head and the cylinder block, because the cylinder head or cylinder block may deform by the tightening pressure.
Especially, when the gasket includes a wire ring around the cylinder hole, the cylinder head or cylinder block is liable to deform when tightened. Also, in case a large surface pressure is applied around a cylinder hole when the gasket is tightened, the cylinder head or cylinder block may deform around the cylinder hole.
As shown in FIGS. 1 and 2, a gasket 10 formed of an upper plate 11 with a bead 11a, a middle plate 12 and a lower plate 13 with a bead 13a is known. When the gasket 10 is tightened, the beads 11a, 13a deform to provide a strong surface pressure around a cylinder hole Hc. Therefore, unless the cylinder head and cylinder block are strong, the cylinder head and cylinder block may deform when tightened.
In U.S. Pat. No. 4,898,396, a gasket is formed of three plates, wherein upper and lower plates extend around a cylinder hole and have sealing mechanisms to seal therearound. In this patent, a surface pressure is formed adjacent to the cylinder hole.
Accordingly, one object of the present invention is to provide a steel laminate gasket, in which the cylinder head and cylinder block can be tightened at desired surface pressure when the gasket is tightened.
Another object of the invention is to provide a steel laminate gasket as stated above, which can provide moderate surface pressure at an area slightly away from the cylinder hole to prevent deformation of the cylinder hole.
A further object of the invention is to provide a steel laminate gasket as stated above, which can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.