At least substantially metallic cylinder head gasket

Details At least substantially metallic cylinder head gasket At least substantially metallic cylinder head gasket

2002-01-23

2004-08-03

Knight, Anthony (Department: 3676)

Seal for a joint or juncture

Seal between fixed parts or static contact against...

Contact seal between parts of internal combustion engine

C277S595000

Reexamination Certificate

active

06769696

ABSTRACT:

The present disclosure relates to the subject matter disclosed in German application No. 101 48 295.7 of Sep. 29, 2001 which is incorporated herein by reference in its entirety and for all purposes.
BACKGROUND OF THE INVENTION
The invention relates to a cylinder head gasket with an at least substantially metallic gasket plate comprising at least one combustion chamber opening enclosed by at least one bead elastically deformable in its height, and close to the bead at least one deformation delimiting device (stopper) likewise enclosing the combustion chamber opening and delimiting the bead deformation.
In the case of one-layered or multilayer metallic cylinder head gaskets it has so far been customary, in order to produce a stopper radially inside or outside (with respect to the combustion chamber opening) of the bead carrying out a sealing function, to increase the thickness of a sheet metal layer in an area enclosing the combustion chamber opening in the shape of a circular ring by a flat metallic ring being attached (for example, by welding) to this sheet metal layer or by an edge area of the sheet metal layer surrounding the combustion chamber opening being flanged, i.e., folded over through approximately 180°. Such a stopper has at least almost no elastic properties, and, in most cases, also at least almost no plastic properties, in any case under the pressure forces exerted on the stopper during operation of the engine.
Single layered or multilayer metallic cylinder head gaskets have recently been proposed (WO 98/28559 and DE-U-298 04 534), wherein the stopper is to a considerable extent plastically and/or elastically, preferably predominantly elastically deformable under the pressure forces acting on the stopper during operation of the engine and is designed in one of the following ways: The sheet metal layer provided with the stopper is provided radially within the bead carrying out the sealing function and requiring protection (with respect to the combustion chamber opening) with one or several beads forming the stopper, enclosing the combustion chamber opening in the shape of a ring and extending concentrically with the combustion chamber opening, and in the event that there are several beads, these can project alternately in one or the other direction of the axis of the combustion chamber opening (see FIGS. 12A and 12B of WO 98/28559). Alternatively, the stopper is formed by a series of ribs and grooves following one another alternately in the radial direction, enclosing the combustion chamber opening in the shape of a ring and being provided on both sides of the sheet metal layer, with the ribs projecting above the two main surfaces of the sheet metal layer and thus resulting in a thickening of the sheet metal layer in the area of the stopper, each rib on the one side of the sheet metal layer having located directly opposite it a rib on the other side of the sheet metal layer (the same then applies to the grooves), and the ribs and grooves having been produced by extrusion of the sheet metal layer (FIG. 12E of WO 98/28559 and DE-U-298 04 534). These stoppers are easier to manufacture than stoppers attached to a sheet metal layer or produced by flanging a sheet metal layer, as it is possible for a sheet metal layer provided with beads to be punched out and provided with the beads with a single tool and for a sheet metal layer to be punched out and provided with the above-described ribs and grooves with a single tool. On the other hand, the recently proposed stoppers have a serious disadvantage:
The fundamental purpose of a stopper is to protect the bead at least mainly carrying out the sealing function against excessive deformations during operation of the engine, a purpose which can only be fulfilled in a highly inadequate way by a stopper which is elastically and/or plastically deformable to a considerable extent during operation of the engine. If the stopper is formed by a bead enclosing the combustion chamber opening in the shape of a circular ring or by several such beads arranged concentrically with each other, the cylinder head gasket clamped between engine block and cylinder head is unable to offer any considerable resistance to the flattening of the beads (not taking into account the stiffness of the beads), as a displacement (in the radial direction with respect to the combustion chamber opening) of the area of the sheet metal layer surrounding the combustion chamber opening, which occurs along with the flattening of the beads forming the stopper, cannot be prevented in these known cylinder head gaskets. These disadvantages also apply to the stopper disclosed in DE-C-199 34 825 consisting of a ring of lugs punched out at three of their sides and bent alternately upwards and downwards out of a sheet metal layer.
The object underlying the invention was to create an at least substantially metallic cylinder head gasket wherein when manufacturing the device for delimiting the deformation (stopper), the attaching of a metal ring or the flanging of a sheet metal layer can likewise be dispensed with, but wherein the device for delimiting the deformation can fulfill its main purpose, namely that of preventing excessive deformation or flattening of a bead mainly carrying out the sealing during operation of the engine better than the above-described known devices for delimiting the deformation consisting of one or several beads or ribs and grooves concentrically enclosing the combustion chamber opening.
SUMMARY OF THE INVENTION
Departing from a cylinder head gasket with such a device for delimiting the deformation, i.e., a cylinder head gasket of the kind mentioned at the outset, wherein the device for delimiting the deformation is formed in a sheet metal layer of the gasket plate by such a deformation of the sheet metal layer that the latter has elevations and depressions in its main surfaces in the area of the device for delimiting the deformation, and the thickness of the device for delimiting the deformation is greater than the original thickness of the undeformed metal sheet of the sheet metal layer, i.e., for example, the thickness of the sheet metal layer in an area of the sheet metal layer bordering directly on the device for delimiting the deformation, this object is accomplished by means of a sheet metal layer provided with the device for delimiting the deformation, which is designed in accordance with the invention, such that in sections through the sheet metal layer along circular cylindrical surfaces coaxial with the combustion chamber opening, the device for delimiting the deformation respectively has a row of discrete elevations following one another in a circumferential direction of the combustion chamber opening and joined to one another in the respective circular cylindrical surface by the sheet metal of the sheet metal layer, and corresponding depressions lying directly opposite these elevations in the sheet metal layer, with the shape of the elevations differing from the shape of circular arcs at least partially enclosing the combustion chamber opening in a plan view of the sheet metal layer, and the total area occupied by the elevations being at least equal to half of the total area of the device for delimiting the deformation and preferably considerably larger than 50% of this total area. The area occupied by an elevation (in a plan view of the sheet metal layer) is to be understood as the total area of all those portions of the sheet metal layer which were deformed when producing the elevation by deforming the sheet metal layer, i.e., which project out of the plane defined by the sheet metal layer prior to its deformation.
The device for delimiting the deformation according to the invention also differs from a modification of the device for delimiting the deformation known from WO 98/28559, which consists of circular-arc-shaped beads which do not extend exactly concentrically with the combustion chamber opening, so that one or several beads immediately adjacent to the combustion chamber opening do not form complete circles—in such a modificatio

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