Metal gasket

#The present invention relates to a metal gasket, which is clamped between two joining surfaces and seals the joining surfaces with a bead thereof, the metal gasket including the bead surrounding at least one hole for fluid, which allows openings for fluid to be communicated with each other, the openings being provided in the respective joining surfaces.

#As a metal gasket mentioned above, for example as shown in FIG. 7, a metal gasket 3 which is held between two joining surfaces 1 and 2, which are joining surfaces with an engine cylinder head and with an EGR plate which is installed on an intake manifold and on which a gas passage concavity for EGR system is formed, is included. Such a metal gasket 3 usually has an intake through hole 3a connecting an intake port 1a and an intake pipe port 2a, which are provided, as openings for fluid, each on the joining surface 1 of the cylinder head and the joining surface 2 of EGR plate installed on the intake manifold, and a full bead 3b having a cross section of a chevron shape as a bead surrounding the intake through hole 3a (It looks V shape in the drawing). Whole circumference of the full bead 3b is interposed between the joining surfaces 1 and 2, which are urged in the closing direction each other by fitting bolts (not shown in the drawing) as shown by an arrow A in the drawing, and is pressed strongly by the joining surfaces 1 and 2. Thus, high surface pressure is generated on whole circumference of the full bead 3b to exert high sealing properties.

#At the request for further engine exhaust gas cleaning and more improvement in fuel consumption and the like in recent years, there have been a possibility that as shown in FIG. 8, the foregoing gas passage concavity 2b, lightning holes and lightning hollows for weight reduction (not shown in the drawing) are formed in an opposite position to a part of bead 3b on a joining surface 2 of an EGR plate installed on the an intake manifold, which is one of two joining surfaces 1 and 2 holding a metal gasket 3 therebetween. When portions without pressuring surface such as the gas passage concavity 2b, the lightning holes and the like are formed, in a single plate-type metal gasket 3 which has been used conventionally, the portions of bead 3b opposite to the portions without pressuring surface such as the foregoing gas passage concavity 2b, the lightning holes and the like should be originally pressurized to the other joining surface as shown with a dashed lined in the drawing. However, there is no surface to push the portions of bead 3b, and the areas of bead 3b can be escaped to an area without pressuring surface as shown with a solid line in the drawing. Therefore, there has been a problem that the areas of bead 3b are not pressurized strongly enough to the joining surface 1 of cylinder head which is the other joining surface and sealing properties in the areas of bead 3b decrease. It has been particularly a problem that the decrease of the sealing properties is especially remarkable when the metal gasket 3 is held between the foregoing joining surface 1 of a cylinder head and the joining surface 2 of EGR plate where pressure in the openings becomes negative pressure since the openings for fluid are an intake port 1a and an intake pipe port 2a.

#FIG. 1 is a plan view showing a single plate-type metal gasket as one embodiment of a metal gasket according to the present invention;

#FIG. 2 is a plan view showing a joining surface for installing an intake manifold, of a cylinder head of an automotive engine, which is one of the two joining surfaces to clamp the metal gasket of the foregoing embodiment therebetween;

#FIG. 3 is a plan view showing a joining surface of EGR plate to the cylinder head, the EGR plate being installed on the intake manifold, which is the other joining surface of the two joining surfaces to clamp the metal gasket of the foregoing embodiment therebetween;

#Hereafter, description will be made in detail for a preferred embodiment of the present invention with reference to the drawings. Here, FIG. 1 is a plan view showing a single plate-type metal gasket as the embodiment of metal gaskets according to the present invention. FIG. 2 is a plan view showing a joining surface for installing an intake manifold of a cylinder head for an automotive engine, which is one of the two joining surfaces clamping the metal gasket of the embodiment therebetween. FIG. 3 is a plan view showing a joining surface of an EGR plate to the cylinder head, the EGR plate is installed on the intake manifold, which is the other one of the two joining surfaces clamping the metal gasket of the embodiment mentioned above therebetween.

#On a joining surface 1 for installing an intake manifold, of a cylinder head for an automotive engine shown in FIG. 2, four intake ports 1a as an opening for fluid are provided, and also a gas passage concavity (concave portion) 1b for an EGR system, as an area without pressuring surface, extending in a channel shape from left side to center area on the upper area of the joining surface 1 in the figure. There are also provided lighting concavities (concave portions) lc for weight reduction, as portions having no pressuring surface, which are located on the upper area of the joining surface 1 and areas between adjacent intake ports 1a in the figure, and five bolt installing holes 1d for installing the foregoing EGR plate to the cylinder head on a joining surface 1 for installing the intake manifold. In each intake port 1a, extending portion 1e, which extends toward another intake port 1a adjacent to the former intake port 1a, is provided.

#Furthermore, on a joining surface 2 of the EGR plate installed on the intake manifold shown in FIG. 3, four intake pipe ports 2a as openings for fluid are provided. There is also provided a gas passage concavity 2b for an EGR system as an area without pressuring surface, which is extended left and right side in a channel shape on the upper area of the joining surface 2 with both ends thereof extending downward, and is located between adjacent intake pipe ports 2a which is two pairs each on either side in the figure, and five penetrating holes 2c for fitting bolts for installing the EGR plate to a cylinder head, on the joining surface 2.